KR20210014060A - Method for processing packet duplication supporting improved handover, method for preventing header decompression failure upon handover and apparatus therefor - Google Patents

Abstract

The present invention relates to a communication technique converging a fifth-generation (5G) communication system for supporting a higher data transmission rate after a fourth-generation (4G) system and Internet of things (IoT) technology and to a system thereof. The present invention can be applied to an intelligent service (for example, a smart home, a smart building, a smart city, a smart or connected car, healthcare, digital education, retail, security, and safety-related services, and the like) based on 5G communication technique and IoT-related technique. Moreover, the present invention relates to a packet duplication processing method for supporting improved handover in a next-generation mobile communication system, a method for preventing a header decompression failure in handover, and an apparatus thereof. A control signal processing method comprises the following steps of: receiving a first control signal transmitted from a base station; processing the received first control signal; and transmitting a second control signal generated based on processing to the base station.

Description

A packet redundancy processing method that supports improved handover in a next-generation mobile communication system, a method for preventing header decompression failure during handover, and a device for this (METHOD FOR PROCESSING PACKET DUPLICATION SUPPORTING IMPROVED HANDOVER, METHOD FOR PREVENTING HEADER DECOMPRESSION FAILURE UPON HANDOVER AND APPARATUS THEREFOR}

The present invention relates to a packet redundancy processing method supporting improved handover in a next-generation mobile communication system, a method for preventing header decompression failure during handover, and an apparatus therefor.

Efforts are being made to develop an improved 5G communication system or a pre-5G communication system in order to meet the increasing demand for wireless data traffic after the commercialization of 4G communication systems. For this reason, a 5G communication system or a pre-5G communication system is called a Beyond 4G Network communication system or an LTE system and a Post LTE system. In order to achieve a high data rate, the 5G communication system is being considered for implementation in the ultra-high frequency (mmWave) band (eg, such as the 60 Giga (60 GHz) band). In order to mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, in 5G communication systems, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed. In addition, in order to improve the network of the system, in 5G communication system, advanced small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation And other technologies are being developed. In addition, in the 5G system, advanced coding modulation (ACM) methods such as Hybrid FSK and QAM Modulation (FQAM) and SWSC (Sliding Window Superposition Coding), advanced access technologies such as Filter Bank Multi Carrier (FBMC), NOMA (non orthogonal multiple access), and sparse code multiple access (SCMA) have been developed.

On the other hand, the Internet is evolving from a human-centered network in which humans generate and consume information, to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. IoE (Internet of Everything) technology, which combines IoT technology with big data processing technology through connection with cloud servers, is also emerging. In order to implement IoT, technology elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, a sensor network for connection between objects, machine to machine , M2M), and MTC (Machine Type Communication) technologies are being studied. In the IoT environment, intelligent IT (Internet Technology) services that create new value in human life by collecting and analyzing data generated from connected objects can be provided. IoT is the field of smart home, smart building, smart city, smart car or connected car, smart grid, healthcare, smart home appliance, advanced medical service, etc. through the convergence and combination of existing IT (information technology) technology and various industries. Can be applied to.

Accordingly, various attempts have been made to apply a 5G communication system to an IoT network. For example, technologies such as sensor network, machine to machine (M2M), and MTC (Machine Type Communication) are implemented by techniques such as beamforming, MIMO, and array antenna. There is. As the big data processing technology described above, a cloud radio access network (cloud RAN) is applied as an example of the convergence of 5G technology and IoT technology.

Meanwhile, technology related to efficient handover in a next-generation mobile communication system is being studied.

In a next-generation mobile communication system, an efficient handover method is required to support a service with low transmission delay and no data loss. In addition, there is a need for a method for preventing a header decompression failure problem that may occur during handover in a terminal or a base station.

The present invention for solving the above problems is a method for processing a control signal of a first terminal in a wireless communication system, the method comprising: receiving a first control signal transmitted from a second terminal; Processing the received first control signal; And transmitting a second control signal generated based on the processing to the second terminal.

In the present invention, when performing a handover in a next-generation mobile communication system, a variety of efficient handover methods that prevent data interruption time due to handover from occurring are proposed to support a service without data interruption. In addition, the present invention proposes methods for preventing a header decompression failure that may occur in a base station or a terminal when performing a handover in a next-generation mobile communication system, so that data is lost or transmission delay occurs due to header compression failure. To be able to solve.

1A is a diagram showing the structure of an LTE system to which the present invention can be applied.
1B is a diagram showing a radio protocol structure in an LTE system to which the present invention can be applied.
1C is a diagram showing the structure of a next-generation mobile communication system to which the present invention can be applied.
1D is a diagram showing a radio protocol structure of a next-generation mobile communication system to which the present invention can be applied.
FIG. 1E is a diagram illustrating a procedure for establishing a connection with a network by switching from an RRC idle mode to an RRC connected mode by a terminal in the present invention.
1F is a diagram illustrating signaling procedures for performing handover in a next generation mobile communication system.
1G shows specific steps of the first embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.
1H is a diagram showing a downlink or uplink original data (PDCP SDU)-based data redundancy method applicable to handover proposed in the present invention.
FIG. 1I is a diagram illustrating an operation of a receiving PDCP layer device and a duplicate detection procedure of a terminal when the original data-based data redundant transmission method is not applied in the first embodiment of the efficient handover method proposed in the present invention.
FIG. 1J is a diagram illustrating an operation of a receiving PDCP layer apparatus of a terminal and a redundancy detection procedure when an original data-based data redundancy transmission method is applied in the first embodiment of the efficient handover method proposed in the present invention.
1K is a diagram illustrating a terminal operation applicable to embodiments proposed in the present invention.
1L shows the structure of a terminal to which an embodiment of the present invention can be applied.
1M is a block diagram of a TRP in a wireless communication system to which an embodiment of the present invention can be applied.
2A is a diagram illustrating a structure of an LTE system to which the present invention can be applied.
2B is a diagram showing a radio protocol structure in an LTE system to which the present invention can be applied.
2C is a diagram showing the structure of a next-generation mobile communication system to which the present invention can be applied.
2D is a diagram showing a radio protocol structure of a next-generation mobile communication system to which the present invention can be applied.
FIG. 2E is a diagram illustrating a procedure for establishing a connection with a network by switching from an RRC idle mode to an RRC connected mode by a terminal in the present invention.
2F is a diagram illustrating signaling procedures for performing handover in a next generation mobile communication system.
FIG. 2G is a diagram illustrating a header compression or decompression procedure when PDCP layer devices of a transmitting end and a receiving end use the ROHC protocol in the handover procedure of FIG. 2F.
2H is a diagram illustrating a first embodiment in which a header decompression failure problem may occur with respect to downlink data during handover in the present invention.
2I is a diagram showing a second embodiment in which a header decompression failure problem may occur for downlink data during handover in the present invention.
FIG. 2J is a diagram illustrating another second embodiment in which a header decompression failure problem may occur for uplink data during handover in the present invention.
2K is a diagram illustrating a third embodiment in which a header decompression failure problem may occur with respect to downlink data during handover in the present invention.
2L is a diagram showing another third embodiment in which a header decompression failure problem may occur for uplink data during handover in the present invention.
2M is a diagram showing the operation of a terminal proposed in the present invention.
2N shows a structure of a terminal to which an embodiment of the present invention can be applied.
2O is a block diagram of a TRP in a wireless communication system to which an embodiment of the present invention can be applied.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary depending on the intention or custom of users or operators. Therefore, the definition should be made based on the contents throughout this specification.

In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

A term for identifying an access node used in the following description, a term for network entities, a term for messages, a term for an interface between network objects, a term for various identification information And the like are illustrated for convenience of description. Therefore, the present invention is not limited to the terms described below, and other terms referring to objects having an equivalent technical meaning may be used.

For convenience of description below, the present invention uses terms and names defined in the 3GPP 3rd Generation Partnership Project Long Term Evolution (LTE) standard. However, the present invention is not limited by the terms and names, and can be applied equally to systems conforming to other standards. In the present invention, the eNB may be used interchangeably with gNB for convenience of description. That is, a base station described as an eNB may represent a gNB.

The present invention proposes seamless handover methods capable of minimizing data interruption time due to handover or making it 0 ms in a next-generation mobile communication system.

Specifically, the efficient handover methods proposed in the present invention may have one or two or more of the following features.

- Performing data transmission and reception (uplink or downlink data transmission and reception) through protocol layer devices (PHY layer device, MAC layer device, RLC layer device, or PDCP layer device) of the source base station and the first plurality of bearers When the terminal receives a handover command message (for example, a handover command message or an RRC Reconfiguration message) from the source base station, the terminal corresponds to the protocol layer devices of the first plurality of bearers (for example, having the same bearer identifier). ) Protocol layer devices of a new second plurality of bearers are set, and data transmission/reception (uplink or downlink data transmission and reception) is not interrupted through the first plurality of bearers with the source base station, and data is maintained. It may be characterized in that it performs transmission/reception (uplink or downlink data transmission and reception).

-After receiving the handover command message from the above, protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device) of a plurality of newly configured second bearers are sent to the handover command message. It is characterized in that it is configured for data transmission and reception with the target base station based on the included bearer configuration information or protocol layer device information.

-In the above, the UE performs data transmission/reception (uplink or downlink data transmission and reception) with the source base station to the protocol layer devices of the first plurality of bearers, while being used as the protocol layer device of the second plurality of bearers (for example, For example, a MAC layer device) may be characterized by performing a random access procedure to a target base station. In the above, the random access procedure may include transmitting a preamble, receiving a random access response, or transmitting a message 3.

-In the above, the UE performs data transmission/reception with the source base station to the protocol layer devices of the first plurality of bearers, and the random access procedure to the target base station to the protocol layer device of the second plurality of bearers (for example, the MAC layer device). And transmitting a handover completion message to the target base station to the protocol layer devices of the second plurality of bearers.

- In the above, when the UE performs data transmission/reception with the source base station by the protocol layer devices of the first plurality of bearers, if the first uplink transmission resource is allocated from the target base station, the UE passes through the protocol layer devices of the first plurality of bearers. Receiving downlink data, but stopping uplink data transmission, switching the uplink data transmission to the protocol layer device of the second plurality of bearers (for example, the MAC layer device) to transmit the uplink data to the target base station. It may be characterized in that the downlink data is also received from the target base station to the protocol layer device of the second plurality of bearers (for example, the MAC layer device).

In the following of the present invention, efficient handover procedures with no data interruption time and low transmission delay are proposed based on the above features.

1A is a diagram showing the structure of an LTE system to which the present invention can be applied.

Referring to Figure 1a, as shown, the radio access network of the LTE system is a next-generation base station (Evolved Node B, hereinafter ENB, Node B or base station) (1a-05, 1a-10, 1a-15, 1a-20) and It is composed of MME (1a-25, Mobility Management Entity) and S-GW (1a-30, Serving-Gateway). User Equipment (hereinafter, referred to as UE or terminal) 1a-35 accesses an external network through ENBs 1a-05 to 1a-20 and S-GW 1a-30.

In FIG. 1A, ENBs 1a-05 to 1a-20 correspond to the existing node B of the UMTS system. The ENB is connected to the UEs 1a-35 through a radio channel and performs a more complex role than the existing Node B. In the LTE system, all user traffic including real-time services such as VoIP (Voice over IP) through the Internet protocol are serviced through a shared channel, so status information such as buffer status, available transmission power status, and channel status of UEs A device that collects and schedules is required, and ENB (1a-05 ~ 1a-20) is in charge of this. One ENB typically controls multiple cells. For example, in order to implement a transmission rate of 100 Mbps, the LTE system uses, for example, an orthogonal frequency division multiplexing (OFDM) in a 20 MHz bandwidth as a radio access technology. In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied. The S-GW 1a-30 is a device that provides a data bearer, and creates or removes a data bearer under the control of the MME 1a-25. The MME is a device responsible for various control functions as well as mobility management functions for a terminal, and is connected to a plurality of base stations.

1B is a diagram showing a radio protocol structure in an LTE system to which the present invention can be applied.

Referring to Figure 1b, the radio protocol of the LTE system is PDCP (Packet Data Convergence Protocol 1b-05, 1b-40), RLC (Radio Link Control 1b-10, 1b-35), MAC (Medium Access Control 1b-15, 1b-30). PDCP (Packet Data Convergence Protocol) (1b-05, 1b-40) is in charge of operations such as IP header compression/restore. The main functions of PDCP are summarized as follows.

-Header compression and decompression (ROHC only)

-Transfer of user data

-In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM

-Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

-Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM

-Retransmission of PDCP SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM

-Encryption and decryption function (Ciphering and deciphering)

-Timer-based SDU discard in uplink.

Radio Link Control (hereinafter referred to as RLC) (1b-10, 1b-35) performs ARQ operation by reconfiguring a PDCP packet data unit (PDU) to an appropriate size. The main functions of RLC are summarized as follows.

-Data transfer function (Transfer of upper layer PDUs)

-ARQ function (Error Correction through ARQ (only for AM data transfer))

-Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)

-Re-segmentation of RLC data PDUs (only for AM data transfer)

-Reordering of RLC data PDUs (only for UM and AM data transfer)

-Duplicate detection (only for UM and AM data transfer)

-Error detection function (Protocol error detection (only for AM data transfer))

-RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

-RLC re-establishment

The MACs 1b-15 and 1b-30 are connected to several RLC layer devices configured in one terminal, and perform an operation of multiplexing RLC PDUs to MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC are summarized as follows.

-Mapping between logical channels and transport channels

-Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels

-Scheduling information reporting function

-HARQ function (Error correction through HARQ)

-Priority handling between logical channels of one UE

-Priority handling between UEs by means of dynamic scheduling

-MBMS service identification

-Transport format selection

-Padding function

The physical layer (1b-20, 1b-25) channel-codes and modulates upper layer data, converts it into OFDM symbols, and transmits it to the radio channel, or demodulates OFDM symbols received through the radio channel and decodes the channel and delivers it to the upper layer. Do the action.

1C is a diagram showing the structure of a next-generation mobile communication system to which the present invention can be applied.

Referring to Figure 1c, as shown, the radio access network of the next-generation mobile communication system (hereinafter NR or 5G) is a next-generation base station (New Radio Node B, hereinafter NR gNB or NR base station) (1c-10) and NR CN (1c). -05, New Radio Core Network). The user terminal (New Radio User Equipment, hereinafter NR UE or terminal) 1c-15 accesses the external network through the NR gNB 1c-10 and NR CN 1c-05.

In FIG. 1C, the NR gNB 1c-10 corresponds to an Evolved Node B (eNB) of an existing LTE system. The NR gNB is connected to the NR UE 1c-15 through a radio channel and can provide a service superior to that of the existing Node B. In the next-generation mobile communication system, all user traffic is serviced through a shared channel, so a device that collects and schedules status information such as buffer status, available transmission power status, and channel status of UEs is required. (1c-10) is in charge. One NR gNB typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the current LTE, it may have more than the existing maximum bandwidth, and a beamforming technology may be additionally grafted using Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology. . In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied. The NR CN (1c-05) performs functions such as mobility support, bearer setup, and QoS setup. The NR CN is a device responsible for various control functions as well as mobility management functions for a terminal, and is connected to a plurality of base stations. In addition, the next-generation mobile communication system can be interlocked with the existing LTE system, and the NR CN is connected to the MME (1c-25) through a network interface. The MME is connected to the existing eNB (1c-30).

1D is a diagram showing a radio protocol structure of a next-generation mobile communication system to which the present invention can be applied. .

Referring to Figure 1d, the radio protocol of the next-generation mobile communication system is NR SDAP (1d-01, 1d-45), NR PDCP (1d-05, 1d-40), NR RLC (1d-10) in the terminal and the NR base station, respectively. , 1d-35), and NR MAC (1d-15, 1d-30).

The main functions of the NR SDAP (1d-01, 1d-45) may include some of the following functions.

-Transfer of user plane data

-Mapping between a QoS flow and a DRB for both DL and UL for uplink and downlink

-Marking QoS flow ID for uplink and downlink (marking QoS flow ID in both DL and UL packets)

-A function of mapping a relective QoS flow to a data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

For the SDAP layer device, the UE may be configured with an RRC message to set whether to use the header of the SDAP layer device or the function of the SDAP layer device for each PDCP layer device, bearer or logical channel, and the SDAP header. If is set, the UE uses the NAS QoS reflective configuration 1-bit indicator (NAS reflective QoS) in the SDAP header and the AS QoS reflective configuration 1-bit indicator (AS reflective QoS) to map the QoS flow and data bearer of the uplink and downlink. Can be instructed to update or reset. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used as data processing priority, scheduling information, etc. to support smooth service.

The main functions of NR PDCP (1d-05, 1d-40) may include some of the following functions.

Header compression and decompression (ROHC only)

-Transfer of user data

-In-sequence delivery of upper layer PDUs

-Out-of-sequence delivery of upper layer PDUs

-Order reordering function (PDCP PDU reordering for reception)

-Duplicate detection of lower layer SDUs

-Retransmission of PDCP SDUs

-Encryption and decryption function (Ciphering and deciphering)

-Timer-based SDU discard in uplink.

In the above, the reordering function of the NR PDCP device refers to a function of rearranging the PDCP PDUs received from the lower layer in order based on the PDCP sequence number (SN), and the function of delivering data to the upper layer in the rearranged order. It may include, or may include a function of immediately delivering without considering the order, may include a function of recording lost PDCP PDUs by rearranging the order, and reporting the status of lost PDCP PDUs It may include a function of performing the transmission side, and may include a function of requesting retransmission of lost PDCP PDUs.

The main functions of the NR RLC (1d-10, 1d-35) may include some of the following functions.

-Data transfer function (Transfer of upper layer PDUs)

-In-sequence delivery of upper layer PDUs

-Out-of-sequence delivery of upper layer PDUs

-ARQ function (Error Correction through ARQ)

-Concatenation, segmentation and reassembly of RLC SDUs

-Re-segmentation of RLC data PDUs

-Reordering of RLC data PDUs

-Duplicate detection

-Protocol error detection

-RLC SDU discard function (RLC SDU discard)

-RLC re-establishment

In the above, the in-sequence delivery function of the NR RLC device refers to the function of delivering RLC SDUs received from the lower layer to the upper layer in order, and originally, one RLC SDU is divided into several RLC SDUs and received. If so, it may include a function of reassembling and delivering it, and may include a function of rearranging the received RLC PDUs based on RLC sequence number (SN) or PDCP sequence number (SN), and rearranging the order It may include a function of recording lost RLC PDUs, may include a function of reporting a status of lost RLC PDUs to a transmitting side, and a function of requesting retransmission of lost RLC PDUs. If there is a lost RLC SDU, it may include a function of transferring only RLC SDUs before the lost RLC SDU to a higher layer in order, or if a predetermined timer expires even if there is a lost RLC SDU, the timer It may include a function of delivering all RLC SDUs received before the start of the system in order to the upper layer, or if a predetermined timer expires even if there is a lost RLC SDU, all RLC SDUs received so far are sequentially transferred to the upper layer. It may include the ability to deliver. In addition, RLC PDUs may be processed in the order in which they are received (regardless of the order of serial number and sequence number, in the order of arrival) and delivered to the PDCP device regardless of the order (Out-of sequence delivery). Segments stored in a buffer or to be received in the future may be received, reconstructed into one complete RLC PDU, processed, and delivered to the PDCP device. The NR RLC layer may not include a concatenation function, and the function may be performed in the NR MAC layer or may be replaced with a multiplexing function of the NR MAC layer.

In the above, the out-of-sequence delivery function of the NR RLC device refers to a function of directly delivering RLC SDUs received from the lower layer to the upper layer regardless of the order, and originally, one RLC SDU is When it is divided into SDUs and received, it may include a function of reassembling and transmitting them, and includes a function of storing the RLC SN or PDCP SN of the received RLC PDUs, sorting the order, and recording the lost RLC PDUs. I can.

The NR MACs 1d-15 and 1d-30 may be connected to several NR RLC layer devices configured in one terminal, and the main functions of the NR MAC may include some of the following functions.

-Mapping between logical channels and transport channels

-Multiplexing and demultiplexing function (Multiplexing/demultiplexing of MAC SDUs)

-Scheduling information reporting function

-HARQ function (Error correction through HARQ)

-Priority handling between logical channels of one UE

-Priority handling between UEs by means of dynamic scheduling

-MBMS service identification

-Transport format selection

-Padding function

The NR PHY layer (1d-20, 1d-25) channel-codes and modulates upper layer data, converts it into OFDM symbols, and transmits it to the radio channel, or demodulates and channel-decodes OFDM symbols received through the radio channel to the upper layer. You can perform the transfer operation.

FIG. 1E is a diagram illustrating a procedure for establishing a connection with a network by switching from an RRC idle mode to an RRC connected mode by a terminal in the present invention.

In FIG. 1e, the base station may send an RRCConnectionRelease message to the terminal when the terminal transmitting and receiving data in the RRC connected mode does not transmit or receive data for a predetermined reason or for a predetermined period of time to switch the terminal to the RRC idle mode (1e-01). In the future, when the current connection is not established (hereinafter, idle mode UE), when data to be transmitted occurs, it performs an RRC connection establishment process with the base station. The terminal establishes uplink transmission synchronization with the base station through a random access process and transmits an RRCConnectionRequest message to the base station (1e-05). In the message, the identifier of the terminal and the reason for establishing a connection (establishmentCause) are stored. The base station transmits an RRCConnectionSetup message so that the terminal establishes an RRC connection (1e-10).

The message includes configuration information for each service/bearer/each RLC device or logical channel or for each bearer, whether to use ROHC for each bearer/logical channel, and ROHC configuration information (e.g., ROHC version, initial information, etc. ), statusReportRequired information (information that the base station instructs the PDCP Status report to the terminal), drb-ContinueROHC information (configuration information to keep and use the ROHC configuration information as it is, included in the PDCP layer device configuration information (pdcp-config) to be transmitted. Can). In addition, RRC connection configuration information and the like are stored in the message. The bearer for the RRC connection is also referred to as SRB (Signaling Radio Bearer), and is used for transmission and reception of an RRC message, which is a control message between the terminal and the base station.

The terminal that has established the RRC connection transmits an RRCConnetionSetupComplete message to the base station (1e-15). The message includes a control message called SERVICE REQUEST that requests the MME to set up a bearer for a predetermined service. The base station transmits the SERVICE REQUEST message contained in the RRCConnetionSetupComplete message to the MME or AMF (1e-20), and the MME or AMF determines whether to provide the service requested by the terminal. As a result of the determination, if the terminal determines to provide the requested service, the MME or AMF transmits an INITIAL CONTEXT SETUP REQUEST message to the base station (1e-25). The message includes information such as QoS (Quality of Service) information to be applied when setting up a Data Radio Bearer (DRB), and security-related information (for example, Security Key, Security Algorithm) to be applied to the DRB.

In addition, when the base station does not receive the capability information of the UE from the MME or AMF, the base station may transmit a UE capability information request message to the UE to check capability information of the UE (1e-26). Upon receiving the UE capability information request message, the UE may construct and generate a UE capability information message and report it to the base station (1e-27). The terminal capability information message may include what types of handover methods the terminal supports. For example, an indicator for each handover method may be defined in the terminal capability information report message, and handover methods supported by the terminal may be indicated by the indicator to report whether each handover method is supported to the base station. When the base station checks the terminal capability information, the base station considers the reported UE capability using an indicator defined for each handover method in a handover command message (e.g., RRCReconfiguration message) when instructing the UE to handover. Thus, it is possible to set which handover method to indicate to the terminal. The terminal may perform a handover procedure to the target base station according to the handover method indicated in the handover command message.

The base station exchanges a SecurityModeCommand message (1e-30) and a SecurityModeComplete message (1e-35) to configure security with the terminal. When the security configuration is completed, the base station transmits an RRCConnectionReconfiguration message to the terminal (1e-40).

The message includes configuration information for each service/bearer/each RLC device or logical channel or for each bearer, whether to use ROHC for each bearer/logical channel, and ROHC configuration information (e.g., ROHC version, initial information, etc. ), statusReportRequired information (information that the base station instructs the PDCP Status report to the terminal), drb-ContinueROHC information (configuration information to keep and use the ROHC configuration information as it is, included in the PDCP layer device configuration information (pdcp-config) to be transmitted. Can). In addition, RRC connection configuration information and the like are stored in the message. The bearer for the RRC connection is also referred to as SRB (Signaling Radio Bearer), and is used for transmission and reception of an RRC message, which is a control message between the terminal and the base station.

In addition, the message includes configuration information of a DRB to which user data is to be processed, and the terminal applies the information to configure the DRB and transmits an RRCConnectionReconfigurationComplete message to the base station (1e-45). The base station after completing the DRB setup with the terminal transmits an INITIAL CONTEXT SETUP COMPLETE message to the MME or AMF (1e-50), and the MME or AMF that receives it transmits the S1 BEARER SETUP message and S1 to set up the S-GW and S1 bearers. Exchange BEARER SETUP RESPONSE messages (1e-055, 1e-60). The S1 bearer is a connection for data transmission established between the S-GW and the base station, and corresponds to DRB and 1:1. When all of the above processes are completed, the terminal transmits and receives data through the base station and the S-GW (1e-65, 1e-70). This general data transmission process is largely composed of three steps: RRC connection setup, security setup, and DRB setup. In addition, the base station may transmit an RRC Connection Reconfiguration message to the terminal for a predetermined reason to refresh, add, or change the configuration (1e-75).

In the present invention, a bearer may mean including SRB and DRB, SRB means Signaling Radio Bearer, and DRB means Data Radio Bearer. The SRB is mainly used to transmit and receive RRC messages of the RRC layer device, and the DRB is mainly used to transmit and receive user layer data. In addition, UM DRB refers to a DRB using an RLC layer device operating in an UM (Unacknowledged Mode) mode, and AM DRB refers to a DRB using an RLC layer device operating in an AM (Acknowledged Mode) mode.

1F is a diagram illustrating signaling procedures for performing handover in a next generation mobile communication system.

The terminal (1f-01) in the RRC connected mode state reports the cell measurement information (Measurement Report) to the current source base station (Source eNB, 1f-02) when a periodic or specific event is satisfied (1f-05). Based on the measurement information, the source base station determines whether or not the terminal performs handover to an adjacent cell. Handover is a technology for changing a source base station providing a service to a terminal in a connected mode state to another base station (or another cell of the same base station). If the source base station determines handover, the source base station sends a handover request message (HO (Handover) request) message to a new base station that will provide service to the terminal, that is, a target base station (Traget eNB, 1f-03). Is requested (1f-10).

The handover request message may include a handover method supported or preferred by a source base station or a plurality of handover methods, and may include an indicator requesting a handover method preferred by the target base station as another method.

If the target base station accepts the handover request, it transmits a handover request acceptance (HO request Ack) message to the source base station (1f-15).

The handover request acceptance message may include a handover method included by the source base station in the handover request message or a handover method supported (or preferred or indicated) by a target base station among a plurality of handover methods. The base station may instruct the terminal of the handover method indicated by the target base station in the handover request acceptance message. As another method, the target base station may configure the source base station and the terminal to perform the indicated handover method by indicating a handover method supported by the target base station as an indicator in the handover request acceptance message.

Upon receiving the message, the source base station transmits a handover command message (HO command message) to the terminal (1f-20). The handover command (HO command) message is transmitted by the source base station to the terminal using an RRC Connection Reconfiguration message (1f-20).

By using an indicator defined for each handover method in the handover command message (for example, an RRCReconfiguration message), the base station may set a handover method to the terminal in consideration of the terminal capability. The terminal may perform a handover procedure to the target base station according to the handover method indicated in the handover command message.

Upon receiving the message, the terminal stops transmitting and receiving data with the source base station and starts a timer T304. In T304, if the terminal does not succeed in handover to the target base station for a predetermined time, it returns to the original configuration of the terminal and switches to the RRC Idle state. The source base station delivers a sequence number (SN) status for uplink/downlink data and, if there is downlink data, transfers it to the target base station (1f-30, 1f-35). The terminal attempts random access to the target cell indicated by the source base station (1f-40). The random access is for notifying the target cell that the terminal is moving through handover and at the same time to synchronize uplink synchronization. For the random access, the terminal transmits a preamble ID provided from the source base station or a preamble corresponding to a randomly selected preamble ID to the target cell. After transmission of the preamble, after a specific number of subframes have passed, the UE monitors whether a random access response message (RAR) is transmitted from the target cell. The time interval to be monitored is referred to as a random access response window (RAR window). During the specific time, if a random access response (RAR) is received (1f-45). The terminal transmits a handover complete (HO complete) message to the target base station as an RRC Reconfiguration Complete message (1f-55). When the random access response is successfully received from the target base station as described above, the terminal terminates the T304 timer (1f-50). The target base station requests path modification to correct the paths of bearers set as the source base station (1f-60, 1f-65) and notifies the source base station to delete the UE context of the terminal (1f-70). Accordingly, the terminal attempts to receive data from the start of the RAR window to the target base station, and after receiving the RAR, transmits an RRC Reconfiguration Complete message and starts data transmission and reception with the target base station.

The present invention proposes seamless handover methods that can minimize or make the data interruption time due to handover 0ms in a next-generation mobile communication system, and downlink or uplink packets to minimize transmission delay that may occur during handover. (For example, PDCP SDU) We propose a redundancy method.

The UE sets a source base station and a plurality of first bearers, and transmits/receives data (uplink or downlink) through protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device) of each bearer. Data transmission and reception), and setting a target base station and a plurality of second bearers, and configuring each protocol layer device (PHY layer device or MAC layer device or RLC layer device or PDCP layer device) of each bearer. Although data transmission and reception (uplink or downlink data transmission and reception) can be performed, in the following of the present invention, for convenience of explanation, one bearer is described and described as if the terminal has one bearer in the drawings and description.

1G shows specific steps of the first embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.

In FIG. 1G, when the UE confirms the indicator indicating the improved handover method in the handover command message or the indicator indicating the handover method of the first embodiment proposed in the present invention, the method of the first embodiment of the present invention is applied. I can.

In the first embodiment of the efficient handover method of FIG. 1G, the terminal 1g-20 transmits and receives data with the source base station 1g-05 in the first step 1g-01, and then sends a handover command message from the source base station. Even if received, data can be continuously transmitted and received through the source base station and the protocol layer devices (1g-22) of the first bearer in order to minimize the data interruption time that occurs during handover. I can. When an indicator indicating an improved handover method or an indicator indicating a handover method according to the first embodiment proposed in the present invention is identified in the handover command message, the method according to the first embodiment of the present invention can be applied.

In addition, according to the settings included in the handover command message received above, the UE may use protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device, 1g-21) of the second bearer for the target base station. ) Can be set or established in advance. The second bearer may be configured and established to have the same bearer identifier or logical channel identifier as the first bearer so that data interruption time does not occur for each bearer. In addition, in the first embodiment, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may be characterized in that they logically operate as one PDCP layer device, and a more detailed operation method is shown in FIG. Explain. When the one PDCP layer device distinguishes between the layer devices of the first bearer and the layer devices of the second bearer, consider that they are connected to different MAC layer devices or have different logical channel identifiers, or Considering that they are different RLC layer devices connected to different MAC layer devices or using different encryption keys, the layer devices of the first bearer (or the first RLC layer device) and By separating layer devices of the second bearer (or second RLC layer devices), encryption or decryption procedures are performed with different security keys for uplink data and downlink data, and different compression protocol contexts are used. It may be characterized by compressing or decompressing.

In addition, in the case where the UE can transmit both the uplink data to the source base station and the target base station in the first embodiment, a coverage reduction problem due to insufficient transmission power of the UE or a transmission resource request to a base station when transmitting uplink data In order to prevent the problem of determining whether to transmit the uplink data (link selection), the transmission of uplink data in the first embodiment may be characterized in that transmission of uplink data can be transmitted to only one of the source base station and the target base station. . That is, in the first embodiment of the improved handover method proposed in the present invention, uplink data transmission is not simultaneously transmitted to different base stations, and when uplink data transmission is performed to the source base station and the first condition is satisfied, the source base station Switching to the target base station in may perform uplink data transmission to the target base station. Therefore, the terminal performs a scheduling request to only one of the source base station or the target base station, and reports on the size of data to be transmitted from the PDCP layer device (e.g., buffer status report transmission). It may be characterized in that it is possible to transmit uplink data to only one base station by transmitting to only one of the base stations and receiving uplink transmission resources. In addition, even if the terminal receives the handover command message from the source base station, it may be characterized in that it does not initialize the MAC layer device of the first bearer in order to prevent data loss by continuing data transmission and reception due to HARQ retransmission.

In the first embodiment of the efficient handover method of FIG. 1G, the terminal 1g-20 is the target base station 1g-10 indicated in the handover command message in the second step (1g-02). Even when performing the random access procedure through the protocol layer devices of the bearer of the UE, the terminal can continue to transmit and receive data (uplink data transmission and downlink data reception) with the source base station through the protocol layer devices of the first bearer. You can do it.

In the first embodiment of the efficient handover method of FIG. 1G, when the terminal 1g-20 satisfies the first condition in the third step (1g-03), the first bearer protocol layer devices 1g -22) to stop transmitting the uplink data to the source base station, and transmit the uplink data to the target base station through the protocol layer devices (1g-21) of the second bearer. The data can be continuously received from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer. In addition, the PDCP layer device (1g-21) of the second bearer includes transmission/reception data or serial number information stored in the PDCP layer device (1g-22) of the first bearer, information such as header compression and decompression context, or security key. By using the information, it is possible to continuously perform data transmission and reception with the target base station, and downlink data can be received and processed from the source base station.

The first condition for the UE to switch uplink data transmission from the source base station to the target base station in the third step (1g-03) is as follows.

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

-When a specific condition is extended based on the above condition, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or to the terminal When an uplink transmission resource is first indicated

■ For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

◆ When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed. When the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

■ If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

◆ The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a Random Access Response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using a link transmission resource, and a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal performs a random access procedure to the target base station. Since it can be considered that is successfully completed, the UE monitors the PDCCH afterwards and satisfies the first condition when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE or is instructed for the first time. It can be judged that it is. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

■ If the handover command message contains uplink transmission resources for the target base station,

◆ When the terminal transmits message 3 (for example, a handover complete message or an RRCReconfigurationComplete message) to the uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, the random access procedure is performed. It may be determined that it has been successfully completed, and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

■ If the handover command message does not contain uplink transmission resources for the target base station

◆ When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (for example, handover completion Message or RRCReconfigurationComplete message) and receiving a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, it may be determined that the random access procedure has been successfully completed, and that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In the above, the downlink from the source base station (or target base station) is characterized in that the terminal can continue to receive downlink data from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer. RLC, not data, through protocol layer devices of the first bearer (or second bearer) for AM bearers so that data can be received smoothly or the source base station (or target base station) can smoothly transmit downlink data. The RLC status report may be characterized by allowing the source base station (or the target base station) to continuously perform transmission on the uplink. This is because, in the case of AM bearers, after transmitting data to the transmitting end, if successful delivery is not indicated by the RLC status report (ie, if the RLC status report is not received), data cannot be continuously transmitted thereafter. In addition, in the efficient handover method, the terminal satisfies the first condition and stops transmitting uplink data to the source base station through the protocol layer devices of the first bearer, and switches the protocol layer devices of the second bearer. Even if the uplink data is started to be transmitted to the target base station through the terminal, the terminal can smoothly receive the downlink data from the source base station (or target base station) or the source base station (or target base station) can smoothly transmit the downlink data. To allow, transmission of HARQ ACK or HARQ NACK information or RLC control data (for example, ACK or NACK information of RLC status report) or PDCP control data (for example, through protocol layer devices of the first bearer (or second bearer)) For example, PDCP status report or ROHC feedback information) may be continuously transmitted. In addition, in the efficient handover method, the terminal satisfies the first condition and stops transmitting the uplink data to the source base station through the protocol layer devices of the first bearer, and switches the protocol layer device of the second bearer. Even if the uplink data is started to be transmitted to the target base station through the network, the UE also transmits data due to HARQ retransmission of the MAC layer device or data transmission due to retransmission of the AM mode RLC layer device to prevent data loss to the source base station. It can be characterized by being able to carry on. In the above efficient handover method, the terminal satisfies the first condition and stops transmitting uplink data to the source base station through the protocol layer devices of the first bearer, and switches the protocol layer device of the second bearer. When transmitting the uplink data to the target base station through the source base station, the source base station or the target base station divide the time and allocate the transmission resource to the terminal so that the uplink transmission resource to the target base station and the uplink transmission resource to the source base station do not collide. I can. If the uplink transmission resource to the target base station and the uplink transmission resource to the source base station collide and overlap, the terminal prioritizes the uplink transmission resource to the source base station in order to maintain the downlink data transmission from the source base station. Transmission can be performed to the source base station. As another method, if the uplink transmission resource to the target base station and the uplink transmission resource to the source base station collide and overlap, the terminal uplink transmission resource to the target base station to maintain downlink data transmission from the target base station. By prioritizing, data transmission may be performed to the target base station.

Specifically, when the terminal receives the handover command message and the efficient handover of the present invention is instructed, the terminal performs a scheduling request through the first protocol layer device and buffers until the first condition is satisfied. By transmitting a status report to the source base station, uplink transmission resources can be received, uplink data can be transmitted, and downlink data can be received from the source base station. However, if the first condition is satisfied, the UE no longer transmits data to the source base station, switches the uplink, performs a scheduling request through the second protocol layer device, and transmits a buffer status report to the target base station. It is possible to receive uplink transmission resources and transmit uplink data to a target base station. However, the UE can continue to receive downlink data from the source base station, and continues to report HARQ ACK or HARQ NACK or RLC status or PDCP control data (eg, PDCP status report or ROHC feedback information) corresponding to the downlink data. It may be characterized in that the transmission is possible. In addition, the terminal may also receive downlink data from the target base station if the first condition is satisfied.

In the first embodiment of the efficient handover method of FIG. 1G, if the terminal 1g-20 satisfies the second condition in the fourth step 1g-04, the terminal 1g -22) may be characterized by stopping downlink data reception from the source base station 1g-05. In the above, the second condition may be one of the following conditions.

-When the terminal performs a random access procedure to the target base station through the layer devices (1g-21) of the second bearer and receives a random access response

-When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

-When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

-When the base station sets a separate timer to the terminal in an RRC message, and the timer expires

■ The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response is received from the target base station or handover to the target base station. It may be started when transmitting a completion message or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When data is transmitted through the uplink transmission resource after being allocated or when successful delivery of the transmitted data is confirmed

-When the source base station performs the efficient handover proposed in the present invention, a predetermined method to determine when to stop transmitting downlink data to the terminal or to release the connection with the terminal (for example, when a predetermined timer expires) It can be determined as when (a timer can be started after the handover instruction is instructed) or when an indication that the terminal has successfully performed handover to the target base station from the target base station is received). In addition, if the downlink data is not received from the source base station for a predetermined period of time, the terminal may determine that the connection with the source base station is released and release the connection.

-When the terminal receives an instruction to release the connection with the source base station from the target base station (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU

-When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

-If the terminal does not receive downlink data from the source base station for a predetermined time

-When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or to the terminal When an uplink transmission resource is first indicated

■ For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

◆ When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed. When the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

■ If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

◆ The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a Random Access Response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using a link transmission resource, and a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal performs a random access procedure to the target base station. Since it can be considered that is successfully completed, the UE monitors the PDCCH afterwards and satisfies the first condition when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE or is instructed for the first time. It can be judged that it is. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

-If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

■ If the handover command message contains uplink transmission resources for the target base station,

◆ When the terminal transmits message 3 (for example, a handover complete message or an RRCReconfigurationComplete message) to the uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, the random access procedure is performed. It may be determined that it has been successfully completed, and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

■ If the handover command message does not contain uplink transmission resources for the target base station

-When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (for example, handover is completed. Message or RRCReconfigurationComplete message) and receiving a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, it may be determined that the random access procedure has been successfully completed, and that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In the above, if the UE does not indicate HARQ ACK or NACK information for the downlink data after transmitting downlink data to the UE, the source BS may confirm that the UE has stopped receiving downlink data from the source BS. As another method, the UE instructs the source base station to no longer receive downlink data from the source base station by transmitting newly defined MAC control information or RLC control information or PDCP control information or RRC message to the uplink or connects with the source base station. Can be ordered to release.

In addition, the PDCP layer device 1g-21 of the second bearer includes information such as transmission/reception data or serial number information or header compression and decompression context or security key stored in the PDCP layer device 1g-22 of the first bearer. By using, it is possible to continuously perform data transmission and reception with the target base station.

In the present invention, the base station defines indicators for the embodiments proposed in the present invention in the handover command message (e.g., RRCReconfiguration message) when transmitting a handover command message to the terminal, and performs a handover procedure corresponding to an embodiment. It is possible to instruct the UE whether triggering is performed, and the UE may perform a handover procedure according to the handover method indicated in the handover command message and perform handover to the target base station while minimizing data interruption time. As another method, in the handover command message, an indicator for the embodiments proposed in the present invention may be defined for each bearer, and a specific embodiment to be applied to which bearer during handover may be indicated in more detail. For example, the embodiments of the present invention may be applied only to an AM bearer driven by an RLC layer device driven in the AM mode, or extended and applied to a UM bearer driven by an RLC layer device driven in the UM mode. May be. In addition, it is assumed that the embodiments proposed in the present invention are applied to DRB. However, if necessary (for example, if the UE maintains the SRB for the source base station and fails to handover to the target base station, it is possible to report or restore the handover failure message to the SRB for the source base station), the SRB is also extended. It can also be applied.

In the embodiments of the present invention, for convenience of explanation, it has been described that the terminal is configured with a first bearer for a source base station or a second bearer for a target base station, and the terminal is a plurality of first bearers for the source base station. Alternatively, it can be easily extended to a case in which a plurality of second bearers for the target base station are configured and applied equally. As another method, a case in which a plurality of bearers for a plurality of target base stations are configured can be easily extended and applied equally. For example, it is possible to perform a handover procedure to the first target base station and set the second bearers. If the handover fails, the handover procedure is performed to the second target base station, and the second bearers are set to Among the target base stations, the UE may search for and determine a cell that satisfies a predetermined condition (eg, a certain signal strength or more) by itself, and may determine one cell to perform a handover procedure.

In the first embodiment of the efficient handover method for minimizing the data interruption time due to handover in the present invention, it is difficult for the source base station to know exactly when the terminal stops receiving downlink data. Therefore, if the possibility of losing downlink data transmitted from the source base station to the terminal increases, a lot of data may be lost. In the case of the RLC AM mode, data lost as described above may be recovered due to retransmission of the PDCP layer device (eg, a PDCP re-establishment procedure or a PDCP data recovery procedure) during handover, but may cause a transmission delay. Also, in the case of the RLC UM mode, there is no method for recovering data loss as described above.

Accordingly, the present invention proposes a data redundant transmission method applicable to the source base station and the target base station to prevent transmission delay or data loss that may occur during handover as described above.

1H is a diagram showing a downlink or uplink original data (PDCP SDU) based data duplication method applicable to handover proposed in the present invention.

The data redundancy method proposed in FIG. 1H is characterized in that data redundancy transmission is based on original data (PDCP SDU). Specifically, the source base station and the target base station are characterized in that the source base station transmits the same data as the original data once, and the target base station transmits it once to transmit the same data twice, but when the source base station transmits the original data (PDCP SDU) When performing the header compression procedure of the original data, it is compressed by applying the header compression protocol context (1h-10) of the source base station, and when performing the integrity protection or encryption procedure on the original data (or compressed original data), the source base station Integrity protection or encryption procedure is performed by applying the security key (1h-15) of, whereas when the original data (PDCP SDU) is transmitted from the target base station, when the header compression procedure of the original data is performed, the header of the target base station is compressed. Compressed by applying a protocol context (1h-20), and when performing integrity protection or encryption procedures on the original data (or compressed original data), integrity protection or encryption by applying the security key (1h-25) of the target base station The procedure may be performed, and the source base station and the target base station may transmit different data (PDCP PDUs) generated by performing data processing in each PDCP layer device to the terminal with respect to the original data.

Therefore, when the terminal receives the different data (PDCP PDU), in the case of data received from the source base station, it performs a decryption or integrity verification procedure with the security key set from the source base station (1h-35), and the header compression protocol set with the source base station. The header is decompressed with the context (1h-35) and the original data is configured. In the case of data received from the target base station, a decryption or integrity verification procedure is performed with the security key set from the target base station (1h-30), and A header compression protocol context may be used to decompress the header (1h-30), and the original data may be configured and transmitted to an upper layer device. That is, although the two PDCP PDUs transmitted in the above are different data, the PDCP SDU generated through data processing of the receiving PDCP layer device may have the same data.

In addition, in the above, the UE can simultaneously receive downlink data from the source base station and the target base station, and the decoding or integrity verification or header decompression procedure for downlink data from the source base station is performed by using a security key or header compression for the source base station. The procedure is performed in 1h-35 using context, and the procedure for decoding or integrity verification or header decompression for downlink data from the target base station is performed in 1h-30 using a security key or header compression context for the target base station. In the procedure, a function of sorting the PDCP SDUs in an ascending order of a COUNT value or a PDCP serial number for PDCP SDUs for which data processing has been completed, and then transferring them to an upper layer in order may be performed at 1h-40.

The original data (PDCP SDU)-based data redundant transmission method proposed in the present invention may be indicated to the terminal by defining a new indicator in a handover command message (eg, RRCReconfiguration message), and the original data-based data redundant transmission method or The efficient handover method of the first embodiment may be indicated by separately defining an indicator for each downlink or uplink, and may be indicated by defining an indicator separately for each bearer, for each PDCP layer device, or for each logical channel. If an indicator is defined for each bearer when defining a new indicator in the handover command message, only for a specific service (e.g., only for a specific bearer or PDCP layer device sensitive to transmission delay) The efficient handover method of the first embodiment can be applied to a downlink or an uplink.

In FIG. 1H, the UE may perform data transmission/reception with the source base station through protocol layer devices of the first bearer, and simultaneously perform data transmission and reception with the target base station through the protocol layer devices of the second bearer.

In the above, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may be configured in the terminal, respectively, but may logically operate as one PDCP layer device as shown in FIG. 1H. Specifically, the one PDCP layer device may be implemented as an upper PDCP layer device and two lower PDCP layer devices for each source base station and each target base station by dividing functions of the PDCP layer device.

In the above, the upper transmitting PDCP layer device may perform a role of allocating a PDCP serial number to data received from the upper layer device. And header compression can also be performed. In addition, in the two lower transmission PDCP layer devices for each source base station and each target base station, when integrity protection is set using a separate security key set with each source base station and each target base station, the integrity protection procedure is performed in the PDCP header. And data (PDCP SDU), the encryption procedure is applied, and transmitted to the transmission RLC layer device of each of the first bearer or the transmission RLC layer device of the second bearer to perform transmission. In the above, the two lower transmission PDCP layer devices may be characterized in that they may perform parallel processing of header compression or integrity protection or encryption procedures in parallel to accelerate data processing speed. It may be characterized in that the two lower transmission PDCP layer devices perform the integrity protection or encryption procedure using different security keys. In addition, it may be characterized in that the integrity protection or encryption procedure of different data is performed by logically applying different security keys or security algorithms in one transmitting PDCP layer device.

In the above, the upper receiving PDCP layer device performs a duplicate detection function on the data received from the lower layer devices based on the PDCP serial number, or arranges the order of the received data in ascending order of the PDCP serial number to order the upper layer. It can play the role of delivering as it is. In addition, header compression may be decompressed. In addition, in the two lower receiving PDCP layer devices for each source base station and each target base station, when integrity protection is set using a separate security key set with each source base station and each target base station, the integrity verification procedure is performed in the PDCP header. It is applied to and data (PDCP SDU), a decoding procedure is applied, and transmitted to an upper receiving PDCP layer device to perform data processing. In the two lower receiving PDCP layer devices, in order to reduce unnecessary integrity verification or decoding procedures, a window is driven based on the PDCP serial number to discard data outside the window and redundant data is first performed, and valid data in the window is performed. It is also possible to perform the integrity verification or decryption procedure for only those. The two lower receiving PDCP layer devices each perform a header compression or integrity protection or encryption procedure in parallel in order to accelerate the data processing speed in the two lower transmitting PDCP layer devices based on the PDCP serial number. Parallel processing) may be performed, and the integrity protection or encryption procedure may be performed by using different security keys in the two lower transmission PDCP layer devices. In addition, it may be characterized in that the integrity protection or encryption procedure of different data is performed by logically applying different security keys or security algorithms in one transmitting PDCP layer device. In addition, the lower receiving PDCP layer devices may perform an out-of-sequence deciphering or integrity verification procedure for each data received regardless of the order of the PDCP serial numbers.

The upper PDCP layer device and the lower PDCP layer device may be considered as one PDCP layer device, and the one receiving or transmitting PDCP layer device may include layer devices of the first bearer and layer devices of the second bearer. When distinguishing, consider the fact that they are connected to different MAC layer devices, have different logical channel identifiers, or consider that they are different RLC layer devices connected to different MAC layer devices, or use different encryption keys. In consideration of using, the layer devices of the first bearer (or the first RLC layer device) and the layer devices of the second bearer (or the second RLC layer device) are distinguished from the uplink data. The downlink data may be encrypted or decrypted using different security keys, and may be compressed or decompressed using different compression protocol contexts.

When the efficient handover method (e.g., DAPS, Dual Active Protocol Stack) proposed in the present invention is instructed to the terminal in a handover command message and applied and executed by the terminal, the terminal performs a hand if the following fourth condition is satisfied for each bearer. Before receiving the over command message, the PDCP layer device used for each bearer can be switched or changed to the structure of the effective PDCP layer device proposed in FIG. 1H, or newly configured and applied. In the above, the fourth condition may be one or more of the following conditions.

-When the terminal receives the handover command message from the source base station and indicates the efficient handover proposed in the present invention in the handover command message, or indicates a method of applying the efficient PDCP layer device structure proposed in FIG. 1K,

-When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

-When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

-When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits or receives data for the first time through the PUCCH or PUSCH uplink transmission resource

-When the base station sets a separate timer to the terminal in an RRC message, and the timer expires

■ The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response is received from the target base station or handover to the target base station. It may be started when transmitting a completion message or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

-When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or to the terminal When an uplink transmission resource is first indicated

■ For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

◆ When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed. When the included or indicated first uplink transmission resource is received, it may be determined that the fourth condition is satisfied.

■ If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

◆ The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a Random Access Response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using a link transmission resource, and a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal performs a random access procedure to the target base station. Since it can be considered that is successfully completed, the UE monitors the PDCCH afterwards and satisfies the fourth condition when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE or when it is instructed for the first time. It can be judged that it is. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It may be judged that the condition of 4 is satisfied.

-If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

■ If the handover command message contains uplink transmission resources for the target base station,

◆ When the terminal transmits message 3 (for example, a handover complete message or an RRCReconfigurationComplete message) to the uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, the random access procedure is performed. It may be determined that it has been successfully completed and it may be determined that the fourth condition is satisfied. Alternatively, it may be determined that the fourth condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

■ If the handover command message does not contain uplink transmission resources for the target base station

◆ When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (for example, handover completion Message or RRCReconfigurationComplete message) and receiving a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, it may be determined that the random access procedure has been successfully completed and that the fourth condition is satisfied. Alternatively, it may be determined that the fourth condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In addition, when the efficient handover proposed in the present invention is indicated to the terminal in the handover command message and applied and performed by the terminal, the terminal satisfies the fourth condition for each bearer, before receiving the handover command message. The PDCP layer device can be switched or changed to the structure of the effective PDCP layer device proposed in FIG. 1K, or newly configured and applied. In addition, if the following fifth condition is satisfied, the reception of downlink data from the source base station is stopped, and the terminal switches or changes to the structure of the efficient PDCP layer device proposed in FIG. 1K for each bearer, or a handover command to the newly configured structure of the PDCP layer device. Before the message is received, it can be switched back to the PDCP layer device used for each bearer, changed or newly applied. In the above, the fifth condition may be one or more of the following conditions.

-When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

-When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

-When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

-When the base station sets a separate timer to the terminal in an RRC message, and the timer expires

■ The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response is received from the target base station or handover to the target base station. It may be started when transmitting a completion message or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

-When the terminal receives an instruction to release the connection with the source base station from the target base station (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU

-When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

-If the terminal does not receive downlink data from the source base station for a predetermined time

-When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or to the terminal When an uplink transmission resource is first indicated

■ For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

◆ When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed. When the included or indicated first uplink transmission resource is received, it may be determined that the fifth condition is satisfied.

■ If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

◆ The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a Random Access Response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using a link transmission resource, and a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal performs a random access procedure to the target base station. Since it can be considered that is successfully completed, the UE monitors the PDCCH afterwards and satisfies the fifth condition when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE or when it is instructed for the first time. It can be judged that it is. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It may be judged that the condition of 5 is satisfied.

-If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

■ If the handover command message contains uplink transmission resources for the target base station,

◆ When the terminal transmits message 3 (for example, a handover complete message or an RRCReconfigurationComplete message) to the uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, the random access procedure is performed. It may be determined that it has been successfully completed, and it may be determined that the fifth condition is satisfied. Alternatively, it may be determined that the fifth condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

■ If the handover command message does not contain uplink transmission resources for the target base station

◆ When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (for example, handover completion Message or RRCReconfigurationComplete message) and receiving a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, it is determined that the random access procedure has been successfully completed and the fifth condition is satisfied. Alternatively, it may be determined that the fifth condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

As another method, the UE stops receiving downlink data from the source base station when the fifth condition is satisfied, and the RLC layer device or MAC of the first protocol layer device for each bearer determines the structure of the efficient PDCP layer device proposed in FIG. The layer device may be released and the structure of the effective PDCP layer device proposed in FIG. 1K may be continuously applied and used for each bearer.

Therefore, it should be noted that the data redundancy procedure proposed by the present invention is not a data redundant transmission method based on processed data (PDCP PDU), but a data redundancy transmission method based on original data (PDCP SDU). In addition, the structure for receiving downlink data from the source base station and the target base station of the terminal above can be extended and applied even when the original data-based data redundancy procedure is not applied.

The original data (PDCP SDU)-based data redundant transmission method proposed in the present invention may be extended and applied to an uplink data transmission method. Specifically, the terminal is characterized by transmitting the same data as the original data once to the source base station and once to the target base station for redundant transmission, but the original data (PDCP SDU) is processed by one PDCP layer device, When performing the header compression procedure of the original data when transmitting to the source base station, it is compressed by applying the header compression protocol context of the source base station (1h-35), and integrity protection or encryption procedure is applied to the original data (or compressed original data). When performing, the integrity protection or encryption procedure is performed by applying the security key of the source base station (1h-35), whereas when the original data (PDCP SDU) is transmitted to the target base station, the header compression procedure of the original data is performed. Compresses by applying the header compression protocol context of the target base station (1h-30), and when performing integrity protection or encryption procedures on the original data (or compressed original data), integrity protection or encryption by applying the security key of the target base station Performing a procedure (1h-30), characterized in that the UE transmits different data (PDCP PDUs) generated by performing data processing in one PDCP layer device, respectively, to the source base station and the target base station for the original data. can do.

Therefore, when the source base station and the target base station receive the different data (PDCP PDU), the source base station decrypts the received data with the security key of the source base station in the PDCP layer device of the source base station or performs an integrity verification procedure (1h-15). , Decompressing the header in the context of the header compression protocol of the source base station (1h-10) and constructing the original data, and the target base station decrypts the received data with the security key of the target base station in the PDCP layer device of the target base station or performs an integrity verification procedure. After performing (1h-25), decompressing the header in the context of the header compression protocol of the target base station (1h-20), the original data may be configured and transmitted to the upper layer device. That is, although the two PDCP PDUs transmitted in the above are different data, the PDCP SDU generated through data processing of the receiving PDCP layer device may have the same data.

When applying the first embodiment of the efficient handover method proposed above of the present invention, a first method of performing a duplicate detection procedure in a receiving PDCP layer device (terminal or base station) is as follows.

FIG. 1I is a diagram illustrating an operation of a receiving PDCP layer device and a duplicate detection procedure of a terminal when the original data-based data redundant transmission method is not applied in the first embodiment of the efficient handover method proposed in the present invention.

In Figure 1i, the UE can simultaneously receive downlink data from the source base station and the target base station in one PDCP layer device (1i-40), and decryption or integrity verification or header decompression for downlink data from the source base station The procedure is performed using a security key or header compression context for the source base station, and the decoding or integrity verification or header decompression procedure for downlink data from the target base station is performed using a security key or header compression context for the target base station. In the above procedure, the PDCP SDUs for which data processing has been completed may be sorted in an ascending order of a COUNT value or a PDCP serial number, and then transmitted to a higher layer in order.

The first method (1i-30) of the duplicate detection procedure proposed in the present invention above does not distinguish whether the data received from the receiving PDCP layer device is received from the source base station or the target base station, and the PDCP serial number or When data having a PDCP serial number or a COUNT value that has been previously received based on the COUNT value is received, the data is discarded to perform a duplicate detection procedure.

In the first method of performing the duplicate detection procedure in the above, a specific operation of the receiving PDCP layer device is as follows.

Specifically, if the receiving PDCP layer device has previously received the COUNT value corresponding to the currently received data in the duplication detection procedure, and has previously successfully received the data corresponding to the COUNT value, it is determined that duplicate detection has occurred. And discarding the received data to perform a duplicate detection procedure. Successful reception of data above means that the data corresponding to the COUNT value has been processed and stored in a buffer, or has been received and processed and transmitted to an upper layer device, or data has been transmitted to and discarded from an upper layer device. Alternatively, when an integrity protection and verification procedure is set, it may be indicated that integrity verification has been successfully performed on data corresponding to the COUNT value. That is, since it can be determined that the data has not been successfully received when the integrity verification of data received due to an attack by a hacker has failed, normal data may not be discarded in the duplicate detection procedure.

In the first method of performing the duplicate detection procedure in the present invention, a specific operation of the receiving PDCP layer device is as follows.

When receiving a PDCP PDU from a lower layer, the receiving PDCP layer device determines the COUNT value of the received PDCP PDU as follows.

-1> If the received RCVD_SN is RCVD_SN <= SN(RX_DELIV)-Window_Size

■ 2> Update to RCVD_HFN = HFN(RX_DELIV) + 1.

-1> Otherwise, if RCVD_SN is RCVD_SN> SN(RX_DELIV) + Window_Size

■ 2> RCVD_HFN = HFN(RX_DELIV)-Update to 1.

-1> If not above

■ 2> Update RCVD_HFN = HFN(RX_DELIV).

-1> RCVD_COUNT is determined as RCVD_COUNT = [RCVD_HFN, RCVD_SN].

After determining the COUNT value of the received PDCP PDU, the receiving PDCP layer device updates the window state variables and processes the PDCP PDU as follows.

-1> Decryption is performed on the PDCP PDU using the RCVD_COUNT value, and integrity verification is performed.

■ 2> If integrity verification fails

■ 2> Instructs the higher layer to fail integrity verification and discards the received PDCP Data PDU (the data part of the PDCP PDU).

-1> if RCVD_COUNT <RX_DELIV or

-If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before

■ 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

If the received PDCP PDU is not discarded, the receiving PDCP layer device operates as follows.

-1> The PDCP SDU processed above is stored in the receive buffer.

-1> If RCVD_COUNT >= RX_NEXT

■ 2> Update RX_NEXT to RCVD_COUNT + 1.

-1> If the out of order delivery indicator (outOfOrderDelivery) is set (if out of order delivery operation is indicated),

■ 2> The PDCP SDU is delivered to the upper layer.

-1> If RCVD_COUNT is equal to RX_DELIV

■ 2> The above data are delivered to the upper layer in the order of COUNT values.

◆ 3> Starting from the value of COUNT = RX_DELIV, all consecutive PDCP SDUs are delivered to the upper layer.

■ 2> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that is greater than or equal to the current RX_DELIV and has not been delivered to the upper layer.

-1> If the t-Reordering timer is running and the RX_DELIV value is greater than or equal to RX_REORD,

■ 2> Stop and reset the t-Reordering timer.

-1> If the t-Reordering timer is not running (including when it is stopped under the above condition) and RX_DELIV is less than RX_NEXT,

■ 2> Update RX_REORD value to RX_NEXT.

■ 2> Start the t-Reordering timer.

Another specific operation of the receiving PDCP layer device of the first method for performing the duplicate detection procedure in the above is as follows.

Specifically, if the receiving PDCP layer device has previously received the COUNT value corresponding to the currently received data in the duplication detection procedure, and has previously successfully received the data corresponding to the COUNT value (if integrity protection and verification If the procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred and the received data is discarded to improve the duplicate detection procedure. It can prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received. Successful reception of data above means that the data corresponding to the COUNT value has been processed and stored in a buffer, or has been received and processed and transmitted to an upper layer device, or data has been transmitted to and discarded from an upper layer device. Alternatively, when an integrity protection and verification procedure is set, it may be indicated that integrity verification has been successfully performed on data corresponding to the COUNT value. In other words, since it can be determined that the data has not been successfully received when the integrity verification of the data received by the hacker has failed, normal data may not be discarded in the duplicate detection procedure. A detailed procedure of the receiving PDCP layer device proposed in the present invention is as follows.

When receiving a PDCP PDU from a lower layer, the receiving PDCP layer device determines the COUNT value of the received PDCP PDU as follows.

-1> If the received RCVD_SN is RCVD_SN <= SN(RX_DELIV)-Window_Size

■ 2> Update to RCVD_HFN = HFN(RX_DELIV) + 1.

-1> Otherwise, if RCVD_SN is RCVD_SN> SN(RX_DELIV) + Window_Size

■ 2> RCVD_HFN = HFN(RX_DELIV)-Update to 1.

-1> If not above

■ 2> Update RCVD_HFN = HFN(RX_DELIV).

-1> RCVD_COUNT is determined as RCVD_COUNT = [RCVD_HFN, RCVD_SN].

After determining the COUNT value of the received PDCP PDU, the receiving PDCP layer device updates the window state variables and processes the PDCP PDU as follows.

-1> Decryption is performed on the PDCP PDU using the RCVD_COUNT value, and integrity verification is performed.

■ 2> If integrity verification fails

■ 2> Instructs the higher layer to fail integrity verification and discards the received PDCP Data PDU (the data part of the PDCP PDU).

-1> if RCVD_COUNT <RX_DELIV or

-If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and an integrity protection and verification procedure has been set, and the integrity verification procedure has been successfully performed for the PDCP PDU corresponding to the RCVD_COUNT value. If ever

-If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been established

■ Discard the received PDCP Data PDU (the data part of the PDCP PDU).

If the received PDCP PDU is not discarded, the receiving PDCP layer device operates as follows.

-1> The PDCP SDU processed above is stored in the receive buffer.

-1> If RCVD_COUNT >= RX_NEXT

■ 2> Update RX_NEXT to RCVD_COUNT + 1.

-1> If the out of order delivery indicator (outOfOrderDelivery) is set (if out of order delivery operation is indicated),

■ 2> The PDCP SDU is delivered to the upper layer.

-1> If RCVD_COUNT is equal to RX_DELIV

■ 2> If header decompression has not been performed for all currently stored PDCP SDUs, the header decompression procedure is performed (if the header compression procedure is set), and the data is delivered to the upper layer in the order of COUNT values.

◆ 3> Starting from the value of COUNT = RX_DELIV, all consecutive PDCP SDUs are delivered to the upper layer.

■ 2> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that is greater than or equal to the current RX_DELIV and has not been delivered to the upper layer.

-1> If the t-Reordering timer is running and the RX_DELIV value is greater than or equal to RX_REORD,

■ 2> Stop and reset the t-Reordering timer.

-1> If the t-Reordering timer is not running (including when it is stopped under the above condition) and RX_DELIV is less than RX_NEXT,

■ 2> Update RX_REORD value to RX_NEXT.

■ 2> Start the t-Reordering timer.

When the PDCP reordering timer (t-Reordering) expires, the receiving PDCP layer device operates as follows.

-1> If header decompression has not been performed for all currently stored PDCP SDUs, a header decompression procedure is performed (when a header compression procedure is set), and the data is delivered to the upper layer in the order of COUNT values.

■ 2> All PDCP SDUs with COUNT values less than RX_REORD are delivered.

■ 2> All PDCP SDUs having consecutive COUNT values starting from the RX_REORD value are delivered.

-1> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that has a COUNT value greater than or equal to RX_REORD and has not been transferred to the upper layer.

-1> If the RX_DELIV value is less than the RX_NEXT value,

■ 2> Update the RX_REORD value to the RX_NEXT value.

■ 2> Start the t-Reordering timer.

When the PDCP reordering timer (t-Reordering) expires, the receiving PDCP layer device operates as follows.

-1> If the header decompression procedure has not been applied before (i.e., if data has not yet been processed for the upper layer header), the header decompression procedure is performed on the stored data, and the data are in the order of COUNT values. It passes to the upper layer.

n 2> All PDCP SDUs with COUNT values smaller than the RX_REORD value are delivered.

■ 2> All PDCP SDUs having consecutive COUNT values starting from the RX_REORD value are delivered.

-1> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that has a COUNT value greater than or equal to RX_REORD and has not been transferred to the upper layer.

-1> If the RX_DELIV value is less than the RX_NEXT value,

■ 2> Update the RX_REORD value to the RX_NEXT value.

■ 2> Start the t-Reordering timer.

When applying the second embodiment of the efficient handover method proposed in the present invention, a second method of performing a duplicate detection procedure in a receiving PDCP layer device (a terminal or a base station) is as follows. The second embodiment of the efficient handover method above will be described in detail below, and an embodiment of applying the original data-based data redundancy transmission method proposed in the present invention to the first embodiment of the efficient handover method is shown.

FIG. 1J is a diagram illustrating an operation of a receiving PDCP layer apparatus of a terminal and a redundancy detection procedure when an original data-based data redundancy transmission method is applied in the first embodiment of the efficient handover method proposed in the present invention.

In Figure 1j, the UE can simultaneously receive downlink data from the source base station and the target base station in one PDCP layer device (1j-40), and decryption or integrity verification or header decompression for downlink data from the source base station The procedure is performed using a security key or header compression context for the source base station, and the decoding or integrity verification or header decompression procedure for downlink data from the target base station is performed using a security key or header compression context for the target base station. In the above procedure, the PDCP SDUs for which data processing has been completed may be sorted in an ascending order of a COUNT value or a PDCP serial number, and then transmitted to a higher layer in order.

The second method (1j-30) of the redundancy detection procedure proposed in the present invention above distinguishes whether data received from the receiving PDCP layer device is received from the source base station or the target base station, and the duplicate detection procedures are each Separately performing data received from the source base station based on the PDCP serial number or COUNT value (1j-31), and separately performing data received from the target base station based on the PDCP serial number or COUNT value ( 1j-30), and filtering and discarding data received outside the window. In addition, after performing the decoding or integrity verification or header decompression procedure for valid data received within the window, it is processed by the PDCP layer device (decryption or integrity verification) without discriminating whether it is received from the source base station or the target base station. Alternatively, the duplicate detection procedure (1j-32) is performed once again for all PDCP SDUs generated by decompressing the header) based on the PDCP serial number or COUNT value.

That is, when data having a PDCP serial number or COUNT value that has been previously received based on a PDCP serial number or COUNT value for data received from the source base station is received, the data is discarded and the duplicate detection procedure is performed ( 1j-31), upon receipt of data having a PDCP serial number or COUNT value that has been previously received based on the PDCP serial number or COUNT value for data received from the target base station, the data is discarded and the duplicate detection procedure is performed. (1j-30), processing (decryption or integrity verification or header decompression) in the PDCP layer device for the data that has passed the duplication detection procedure, and sets the PDCP serial number or COUNT value for all the generated PDCP SDUs. If there are two or more identical data having each PDCP serial number or COUNT value as a standard, a duplicate detection procedure can be performed by discarding one data (1j-32).

In the above, a duplicate detection procedure is performed once for each link, that is, data received from the source base station (1j-31) or a duplicate detection procedure is performed once for data received from the target base station (1j-30). Then, after performing the processing of the PDCP layer device, the reason for the duplication detection procedure (1j-32) to the original data (PDCP SDU) is performed once more is as follows.

-In the first embodiment of the efficient handover method proposed in the present invention, the terminal can simultaneously receive downlink data from the source base station and the target base station, and the data received from the source base station is compressed by a separate security key and header of the source base station. The context must be applied and processed, and the data received from the target base station must be processed by applying a separate security key and header compression context of the target base station.

-If the original data (PDCP SDU)-based data redundant transmission method proposed in the present invention is applied to the first embodiment of the present invention (second embodiment of the present invention), in the terminal receiving PDCP layer device, the original data is Data received from the source base station for other PDCP PDUs must be processed by applying a separate source base station's security key and header compression context, and the data received from the target base station is processed by applying a separate target base station's security key and header compression context. You have to deal with it.

-However, if the first method of the duplicate detection procedure proposed in the present invention is applied, that is, it does not discriminate whether the received data is received from the source base station or the target base station, and is received as a PDCP serial number or COUNT value. If data (PDCP PDUs) are classified, there may be a problem of discarding data received by a target base station having the same PDCP serial number or COUNT value as the data received from the source base station. For example, the source base station transmits data (PDCP PDU) including information for updating the header compression context of the source base station to the terminal to the terminal with PDCP serial number 3, but the target base station processes data having the same PDCP SDU to PDCP. If configured as a PDCP PDU with serial number 3 and previously transmitted to the terminal, the terminal has received data with PDCP serial number 3 from the target base station, so the header compression context with PDCP serial number 3 received from the source base station is updated. By discarding informational data (eg, IR packet), a problem, error, or failure may occur in the header compression context update procedure.

-Accordingly, the second method of the redundancy detection procedure of the present invention is to perform each redundancy detection procedure according to whether it is received from the source base station or the target base station. This is because data received from each base station may also generate redundant data due to HARQ retransmission or retransmission of the RLC layer device. And the reason for performing the duplicate detection procedure once more after processing in the PDCP layer device for each data is that the original data-based data redundancy transmission method proposed in the present invention allows PDCP SDUs to transmit the same data after processing of the PDCP layer device is completed. Since it has a characteristic of having two or more identical data for each PDCP serial number or COUNT value, only one data must be left and the remaining data must be discarded so that the same data may not be repeatedly transmitted to the upper layer.

In order to apply the second method of the duplicate detection procedure in the above, one PDCP layer device of the terminal or the base station receives data from the source base station (for example, layer devices of the first bearer) and the target base station. When classifying the data (for example, layer devices of the second bearer), consider that they are connected to different MAC layer devices, or have different logical channel identifiers, or are connected to different MAC layer devices. Considering that there are different RLC layer devices, or considering that different encryption keys are used, data received from the source base station (eg, layer devices of the first bearer) and received from the target base station The second method (1j-30, 1j-31) of the redundancy detection procedure is applied by separating data (eg, layer devices of the second bearer), and different data for uplink data and downlink data It may be characterized by performing an encryption or decryption procedure with a security key, compressing or decompressing using different compression protocol contexts, and applying the second method (1j-32) of the duplicate detection procedure.

A detailed operation of the receiving PDCP layer device in the second method for performing the duplicate detection procedure in the above is as follows.

Specifically, if the receiving PDCP layer device has previously received the COUNT value corresponding to the currently received data in the duplication detection procedure, and has previously successfully received the data corresponding to the COUNT value (if integrity protection and verification If the procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred and the received data is discarded to improve the duplicate detection procedure. It can prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received. Successful reception of data above means that the data corresponding to the COUNT value has been processed and stored in a buffer, or has been received and processed and transmitted to an upper layer device, or data has been transmitted to and discarded from an upper layer device. Alternatively, when an integrity protection and verification procedure is set, it may be indicated that integrity verification has been successfully performed on data corresponding to the COUNT value. In other words, since it can be determined that the data has not been successfully received when the integrity verification of the data received by the hacker has failed, normal data may not be discarded in the duplicate detection procedure. A detailed procedure of the receiving PDCP layer device proposed in the present invention is as follows.

When receiving a PDCP PDU from a lower layer, the receiving PDCP layer device determines the COUNT value of the received PDCP PDU as follows.

-1> If the received RCVD_SN is RCVD_SN <= SN(RX_DELIV)-Window_Size

■ 2> Update to RCVD_HFN = HFN(RX_DELIV) + 1.

-1> Otherwise, if RCVD_SN is RCVD_SN> SN(RX_DELIV) + Window_Size

■ 2> RCVD_HFN = HFN(RX_DELIV)-Update to 1.

-1> If not above

■ 2> Update RCVD_HFN = HFN(RX_DELIV).

-1> RCVD_COUNT is determined as RCVD_COUNT = [RCVD_HFN, RCVD_SN].

After determining the COUNT value of the received PDCP PDU, the receiving PDCP layer device updates the window state variables and processes the PDCP PDU as follows.

-1> Decryption is performed on the PDCP PDU using the RCVD_COUNT value, and integrity verification is performed.

■ 2> If integrity verification fails

■ 2> Instructs the higher layer to fail integrity verification and discards the received PDCP Data PDU (the data part of the PDCP PDU).

-1> if RCVD_COUNT <RX_DELIV or

-If a PDCP PDU having a value of 1> or RCVD_COUNT has been successfully received before, and if the downlink source data-based data redundancy transmission method or the efficient handover method of the first embodiment has not been set.

-If a PDCP PDU with a value of 1> or RCVD_COUNT has previously been successfully received from the same lower layer device (for example, when a PDCP layer device is connected to multiple RLC layer devices, from the same RLC layer device (another (If a PDCP PDU having the same RCVD_COUNT value has previously been successfully received) connected to the same MAC layer device or from an RLC layer device having the same logical channel identifier), and the downlink source data-based data redundant transmission method or 1 If the efficient handover method of the embodiment is set

■ 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

If the received PDCP PDU is not discarded, the receiving PDCP layer device operates as follows.

-1> The PDCP SDU processed above is stored in the receive buffer.

-1> If RCVD_COUNT >= RX_NEXT

■ 2> Update RX_NEXT to RCVD_COUNT + 1.

-1> If the out of order delivery indicator (outOfOrderDelivery) is set (if out of order delivery operation is indicated),

■ 2> The PDCP SDU is delivered to the upper layer.

-1> If RCVD_COUNT is equal to RX_DELIV

■ 2> Duplicate detection procedure is performed on all currently stored PDCP SDUs (for example, when the original data-based data redundancy transmission or the efficient handover method of the first embodiment is set, the same COUNT value among the currently stored PDCP SDUs is If there are two or more PDCP SDUs, only one PDCP SDU can be left for each COUNT value and the remaining redundant data (PDCP SDUs) can be discarded, ie, PDCP SDUs having the same COUNT value among all stored PDCP SDUs. By performing a duplication detection procedure for a single COUNT value, only one PDCP SDU corresponding to one COUNT value can be stored and only one can be transmitted to an upper layer, and data redundant transmission based on original data or the efficient handover method of the first embodiment. When this is set, the header decompression procedure may also be performed in an ascending order of COUNT values for each data received by each lower RLC layer device.) If header decompression is not performed on the data, the header decompression procedure is performed. (When the header compression procedure is set), the data is transferred to the upper layer in the order of COUNT values. From the same (or the same) lower layer device in another way (e.g., when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (or connected to the same MAC layer device in another way or the same logical channel) After performing a header decompression procedure in ascending order of the PDCP serial number or COUNT value with the ROHC context (source base station or target base station) corresponding to the lower layer device with respect to the received data (from the RLC layer device having the identifier)) The duplication detection procedure may be performed and the data may be delivered to an upper layer in the order of COUNT values.

◆ 3> Starting from the value of COUNT = RX_DELIV, all consecutive PDCP SDUs are delivered to the upper layer.

■ 2> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that is greater than or equal to the current RX_DELIV and has not been delivered to the upper layer.

-1> If the t-Reordering timer is running and the RX_DELIV value is greater than or equal to RX_REORD,

■ 2> Stop and reset the t-Reordering timer.

-1> If the t-Reordering timer is not running (including when it is stopped under the above condition) and RX_DELIV is less than RX_NEXT,

■ 2> Update RX_REORD value to RX_NEXT.

■ 2> Start the t-Reordering timer.

When the PDCP reordering timer (t-Reordering) expires, the receiving PDCP layer device operates as follows.

-1> Perform a duplicate detection procedure for all currently stored PDCP SDUs (for example, if the original data-based data redundancy transmission or the efficient handover method of the first embodiment is set, the same COUNT value among the currently stored PDCP SDUs is set. If there are two or more PDCP SDUs, only one PDCP SDU can be left for each COUNT value and the remaining redundant data (PDCP SDUs) can be discarded, ie, PDCP SDUs having the same COUNT value among all stored PDCP SDUs. By performing a duplication detection procedure for a single COUNT value, only one PDCP SDU corresponding to one COUNT value can be stored and only one can be transmitted to an upper layer, and data redundant transmission based on original data or the efficient handover method of the first embodiment. When this is set, the header decompression procedure may also be performed in an ascending order of COUNT values for each data received by each lower RLC layer device.) If header decompression is not performed on the data, the header decompression procedure is performed. (When the header compression procedure is set), the data is transferred to the upper layer in the order of COUNT values. From the same (or the same) lower layer device in another way (e.g., when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (or connected to the same MAC layer device in another way or the same logical channel) After performing a header decompression procedure in ascending order of the PDCP serial number or COUNT value with the ROHC context (source base station or target base station) corresponding to the lower layer device with respect to the received data (from the RLC layer device having the identifier)) The duplication detection procedure may be performed and the data may be delivered to an upper layer in the order of COUNT values.

■ 2> All PDCP SDUs with COUNT values less than RX_REORD are delivered.

■ 2> All PDCP SDUs having consecutive COUNT values starting from the RX_REORD value are delivered.

-1> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that has a COUNT value greater than or equal to RX_REORD and has not been transferred to the upper layer.

-1> If the RX_DELIV value is less than the RX_NEXT value,

■ 2> Update the RX_REORD value to the RX_NEXT value.

■ 2> Start the t-Reordering timer.

Another specific operation of the receiving PDCP layer device of the second method for performing the duplicate detection procedure in the above is as follows.

Specifically, if the receiving PDCP layer device has previously received the COUNT value corresponding to the currently received data in the duplication detection procedure, and has previously successfully received the data corresponding to the COUNT value (if integrity protection and verification If the procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred and the received data is discarded to improve the duplicate detection procedure. It can prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received. Successful reception of data above means that the data corresponding to the COUNT value has been processed and stored in a buffer, or has been received and processed and transmitted to an upper layer device, or data has been transmitted to and discarded from an upper layer device. Alternatively, when an integrity protection and verification procedure is set, it may be indicated that integrity verification has been successfully performed on data corresponding to the COUNT value. In other words, since it can be determined that the data has not been successfully received when the integrity verification of the data received by the hacker has failed, normal data may not be discarded in the duplicate detection procedure. A detailed procedure of the receiving PDCP layer device proposed in the present invention is as follows.

When receiving a PDCP PDU from a lower layer, the receiving PDCP layer device determines the COUNT value of the received PDCP PDU as follows.

-1> If the received RCVD_SN is RCVD_SN <= SN(RX_DELIV)-Window_Size

■ 2> Update to RCVD_HFN = HFN(RX_DELIV) + 1.

-1> Otherwise, if RCVD_SN is RCVD_SN> SN(RX_DELIV) + Window_Size

■ 2> RCVD_HFN = HFN(RX_DELIV)-Update to 1.

-1> If not above

■ 2> Update RCVD_HFN = HFN(RX_DELIV).

-1> RCVD_COUNT is determined as RCVD_COUNT = [RCVD_HFN, RCVD_SN].

After determining the COUNT value of the received PDCP PDU, the receiving PDCP layer device updates the window state variables and processes the PDCP PDU as follows.

-1> Decryption is performed on the PDCP PDU using the RCVD_COUNT value, and integrity verification is performed.

■ 2> If integrity verification fails

■ 2> Instructs the higher layer to fail integrity verification and discards the received PDCP Data PDU (the data part of the PDCP PDU).

-1> if RCVD_COUNT <RX_DELIV or

-If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and an integrity protection and verification procedure has been set, and the integrity verification procedure has been successfully performed for the PDCP PDU corresponding to the RCVD_COUNT value. If there is an enemy and if the downlink source data-based data redundancy transmission method or the efficient handover method of the first embodiment is not set,

-If a PDCP PDU having a value of 1> or RCVD_COUNT has been successfully received before and if the integrity protection and verification procedure has not been set, and the downlink original data-based data redundancy transmission method or the efficient handover method of the first embodiment If this is not set

-If a PDCP PDU with a value of 1> or RCVD_COUNT has previously been successfully received from the same lower layer device (for example, when a PDCP layer device is connected to multiple RLC layer devices, from the same RLC layer device (another In this way, if a PDCP PDU having the same RCVD_COUNT value has previously been successfully received) from an RLC layer device connected to the same MAC layer device or having the same logical channel identifier), and an integrity protection and verification procedure has been established, and the RCVD_COUNT value If the integrity verification procedure for the PDCP PDU corresponding to is previously successfully performed, and if the downlink source data-based data redundancy transmission method or the efficient handover method of the first embodiment is set

-If a PDCP PDU having a value of 1> or RCVD_COUNT has been successfully received from the same lower layer device, for example, when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (another method If a PDCP PDU having the same RCVD_COUNT value has been successfully received before) connected to the same MAC layer device or from an RLC layer device having the same logical channel identifier), and if the integrity protection and verification procedure has not been established and downlink If the original data-based data redundancy transmission method or the efficient handover method of the first embodiment is set

■ Discard the received PDCP Data PDU (the data part of the PDCP PDU).

If the received PDCP PDU is not discarded, the receiving PDCP layer device operates as follows.

-1> The PDCP SDU processed above is stored in the receive buffer.

-1> If RCVD_COUNT >= RX_NEXT

■ 2> Update RX_NEXT to RCVD_COUNT + 1.

-1> If the out of order delivery indicator (outOfOrderDelivery) is set (if out of order delivery operation is indicated),

■ 2> The PDCP SDU is delivered to the upper layer.

-1> If RCVD_COUNT is equal to RX_DELIV

■ 2> Duplicate detection procedure is performed on all currently stored PDCP SDUs (for example, when the original data-based data redundancy transmission or the efficient handover method of the first embodiment is set, the same COUNT value among the currently stored PDCP SDUs is If there are two or more PDCP SDUs, only one PDCP SDU can be left for each COUNT value and the remaining redundant data (PDCP SDUs) can be discarded, ie, PDCP SDUs having the same COUNT value among all stored PDCP SDUs. By performing a duplication detection procedure for a single COUNT value, only one PDCP SDU corresponding to one COUNT value can be stored and only one can be transmitted to an upper layer, and data redundant transmission based on original data or the efficient handover method of the first embodiment. When this is set, the header decompression procedure may also be performed in an ascending order of COUNT values for each data received by each lower RLC layer device.) If header decompression is not performed on the data, the header decompression procedure is performed. (When the header compression procedure is set), the data is transferred to the upper layer in the order of COUNT values. From the same (or the same) lower layer device in another way (e.g., when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (or connected to the same MAC layer device in another way or the same logical channel) After performing a header decompression procedure in ascending order of the PDCP serial number or COUNT value with the ROHC context (source base station or target base station) corresponding to the lower layer device with respect to the received data (from the RLC layer device having the identifier)) The duplication detection procedure may be performed and the data may be delivered to an upper layer in the order of COUNT values.

◆ 3> Starting from the value of COUNT = RX_DELIV, all consecutive PDCP SDUs are delivered to the upper layer.

■ 2> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that is greater than or equal to the current RX_DELIV and has not been delivered to the upper layer.

-1> If the t-Reordering timer is running and the RX_DELIV value is greater than or equal to RX_REORD,

■ 2> Stop and reset the t-Reordering timer.

-1> If the t-Reordering timer is not running (including when it is stopped under the above condition) and RX_DELIV is less than RX_NEXT,

■ 2> Update RX_REORD value to RX_NEXT.

■ 2> Start the t-Reordering timer.

When the PDCP reordering timer (t-Reordering) expires, the receiving PDCP layer device operates as follows.

-1> Perform a duplicate detection procedure for all currently stored PDCP SDUs (for example, if the original data-based data redundancy transmission or the efficient handover method of the first embodiment is set, the same COUNT value among the currently stored PDCP SDUs is set. If there are two or more PDCP SDUs, only one PDCP SDU can be left for each COUNT value and the remaining redundant data (PDCP SDUs) can be discarded, ie, PDCP SDUs having the same COUNT value among all stored PDCP SDUs. By performing a duplication detection procedure for a single COUNT value, only one PDCP SDU corresponding to one COUNT value can be stored and only one can be transmitted to an upper layer, and data redundant transmission based on original data or the efficient handover method of the first embodiment. When this is set, the header decompression procedure may also be performed in an ascending order of COUNT values for each data received by each lower RLC layer device.) If header decompression is not performed on the data, the header decompression procedure is performed. (When the header compression procedure is set), the data is transferred to the upper layer in the order of COUNT values. From the same (or the same) lower layer device in another way (e.g., when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (or connected to the same MAC layer device in another way or the same logical channel) After performing a header decompression procedure in ascending order of the PDCP serial number or COUNT value with the ROHC context (source base station or target base station) corresponding to the lower layer device with respect to the received data (from the RLC layer device having the identifier)) The duplication detection procedure may be performed and the data may be delivered to an upper layer in the order of COUNT values.

■ 2> All PDCP SDUs with COUNT values less than RX_REORD are delivered.

■ 2> All PDCP SDUs having consecutive COUNT values starting from the RX_REORD value are delivered.

-1> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that has a COUNT value greater than or equal to RX_REORD and has not been transferred to the upper layer.

-1> If the RX_DELIV value is less than the RX_NEXT value,

■ 2> Update the RX_REORD value to the RX_NEXT value.

■ 2> Start the t-Reordering timer.

In addition, in the above procedure, the receiving PDCP layer device is from the same (or the same) lower layer device (for example, when the PDCP layer device is connected to a plurality of RLC layer devices, the same RLC layer device (with another method) Decompressing headers in ascending order of PDCP serial number or COUNT value with ROHC context (source base station or target base station) corresponding to the lower layer device for data received from the connected or RLC layer device having the same logical channel identifier)) After performing the procedure, in order to perform the duplication detection procedure, different PDCP windows and PDCP window state variables may be independently operated for data received from each lower layer device. For example, in the embodiment of the present invention, since the receiving PDCP layer device is connected to the RLC layer device for the source base station and the RLC layer device for the target base station, the receiving PDCP layer device is received from the RLC layer device for the source base station. The first PDCP window and the first PDCP window state variables can be operated for the data, and the receiving PDCP layer device is also capable of operating the second PDCP window and the second PDCP window for data received from the RLC layer device for the target base station. 2 PDCP window state variables can be operated. By operating the PDCP window and PDCP state variables independently in this way, data received from each base station can be decrypted with a security key corresponding to each base station, and the data received from each base station are sorted in order, and each received in order or in ascending order. The header decompression procedure can be performed according to the base station, and duplicate PDCP SDUs are discarded by applying a redundant detection procedure to the data received from the source base station and the data received from the target base station until the header compression procedure is completed. The data may be transferred to the upper layer device in ascending order of serial number or COUNT value.

Another method of the second method (1j-30) of the redundancy detection procedure proposed in the present invention above is that data received from the receiving PDCP layer device when the second embodiment of the present invention is indicated by the handover command message It is characterized in that the duplicate detection procedure is not performed on the window, and only data received outside the window is filtered and discarded. In addition, after performing the decoding or integrity verification or header decompression procedure for valid data received within the window, it is processed by the PDCP layer device (decryption or integrity verification) without discriminating whether it is received from the source base station or the target base station. Alternatively, a duplicate detection procedure (1j-32) is performed for all PDCP SDUs generated by decompressing the header) based on the PDCP serial number or COUNT value.

That is, each PDCP serial number or COUNT value is based on the PDCP serial number or COUNT value for all PDCP SDUs that are processed (decrypted or integrity verified or header decompressed) for received data in the PDCP layer device. If there are two or more identical data, a duplicate detection procedure can be performed by discarding one data (1j-32).

A detailed operation of the receiving PDCP layer device according to another method of the second method for performing the duplicate detection procedure in the above is as follows.

Specifically, if the receiving PDCP layer device has previously received the COUNT value corresponding to the currently received data in the duplication detection procedure, and has previously successfully received the data corresponding to the COUNT value (if integrity protection and verification If the procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred and the received data is discarded to improve the duplicate detection procedure. It can prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received. Successful reception of data above means that the data corresponding to the COUNT value has been processed and stored in a buffer, or has been received and processed and transmitted to an upper layer device, or data has been transmitted to and discarded from an upper layer device. Alternatively, when an integrity protection and verification procedure is set, it may be indicated that integrity verification has been successfully performed on data corresponding to the COUNT value. In other words, since it can be determined that the data has not been successfully received when the integrity verification of the data received by the hacker has failed, normal data may not be discarded in the duplicate detection procedure. A detailed procedure of the receiving PDCP layer device proposed in the present invention is as follows.

When receiving a PDCP PDU from a lower layer, the receiving PDCP layer device determines the COUNT value of the received PDCP PDU as follows.

-1> If the received RCVD_SN is RCVD_SN <= SN(RX_DELIV)-Window_Size

■ 2> Update to RCVD_HFN = HFN(RX_DELIV) + 1.

-1> Otherwise, if RCVD_SN is RCVD_SN> SN(RX_DELIV) + Window_Size

■ 2> RCVD_HFN = HFN(RX_DELIV)-Update to 1.

-1> If not above

■ 2> Update RCVD_HFN = HFN(RX_DELIV).

-1> RCVD_COUNT is determined as RCVD_COUNT = [RCVD_HFN, RCVD_SN].

After determining the COUNT value of the received PDCP PDU, the receiving PDCP layer device updates the window state variables and processes the PDCP PDU as follows.

-1> Decryption is performed on the PDCP PDU using the RCVD_COUNT value, and integrity verification is performed.

■ 2> If integrity verification fails

■ 2> Instructs the higher layer to fail integrity verification and discards the received PDCP Data PDU (the data part of the PDCP PDU).

-1> if RCVD_COUNT <RX_DELIV or

-If a PDCP PDU having a value of 1> or RCVD_COUNT has been successfully received before, and if the downlink source data-based data redundancy transmission method or the efficient handover method of the first embodiment has not been set.

■ 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

If the received PDCP PDU is not discarded, the receiving PDCP layer device operates as follows.

-1> The PDCP SDU processed above is stored in the receive buffer.

-1> If RCVD_COUNT >= RX_NEXT

■ 2> Update RX_NEXT to RCVD_COUNT + 1.

-1> If the out of order delivery indicator (outOfOrderDelivery) is set (if out of order delivery operation is indicated),

■ 2> The PDCP SDU is delivered to the upper layer.

-1> If RCVD_COUNT is equal to RX_DELIV

■ 2> Duplicate detection procedure is performed on all currently stored PDCP SDUs (for example, when the original data-based data redundancy transmission or the efficient handover method of the first embodiment is set, the same COUNT value among the currently stored PDCP SDUs is If there are two or more PDCP SDUs, only one PDCP SDU can be left for each COUNT value and the remaining redundant data (PDCP SDUs) can be discarded, ie, PDCP SDUs having the same COUNT value among all stored PDCP SDUs. By performing a duplication detection procedure for a single COUNT value, only one PDCP SDU corresponding to one COUNT value can be stored and only one can be transmitted to an upper layer, and data redundant transmission based on original data or the efficient handover method of the first embodiment. When this is set, the header decompression procedure may also be performed in an ascending order of COUNT values for each data received by each lower RLC layer device.) If header decompression is not performed on the data, the header decompression procedure is performed. (When the header compression procedure is set), the data is transferred to the upper layer in the order of COUNT values. From the same (or the same) lower layer device in another way (e.g., when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (or connected to the same MAC layer device in another way or the same logical channel) After performing a header decompression procedure in ascending order of the PDCP serial number or COUNT value with the ROHC context (source base station or target base station) corresponding to the lower layer device with respect to the received data (from the RLC layer device having the identifier)) The duplication detection procedure may be performed and the data may be delivered to an upper layer in the order of COUNT values.

◆ 3> Starting from the value of COUNT = RX_DELIV, all consecutive PDCP SDUs are delivered to the upper layer.

■ 2> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that is greater than or equal to the current RX_DELIV and has not been delivered to the upper layer.

-1> If the t-Reordering timer is running and the RX_DELIV value is greater than or equal to RX_REORD,

■ 2> Stop and reset the t-Reordering timer.

-1> If the t-Reordering timer is not running (including when it is stopped under the above condition) and RX_DELIV is less than RX_NEXT,

■ 2> Update RX_REORD value to RX_NEXT.

■ 2> Start the t-Reordering timer.

When the PDCP reordering timer (t-Reordering) expires, the receiving PDCP layer device operates as follows.

-1> Perform a duplicate detection procedure for all currently stored PDCP SDUs (for example, if the original data-based data redundancy transmission or the efficient handover method of the first embodiment is set, the same COUNT value among the currently stored PDCP SDUs is set. If there are two or more PDCP SDUs, only one PDCP SDU can be left for each COUNT value and the remaining redundant data (PDCP SDUs) can be discarded, ie, PDCP SDUs having the same COUNT value among all stored PDCP SDUs. By performing a duplication detection procedure for a single COUNT value, only one PDCP SDU corresponding to one COUNT value can be stored and only one can be transmitted to an upper layer, and data redundant transmission based on original data or the efficient handover method of the first embodiment. When this is set, the header decompression procedure may also be performed in an ascending order of COUNT values for each data received by each lower RLC layer device.) If header decompression is not performed on the data, the header decompression procedure is performed. (When the header compression procedure is set), the data is transferred to the upper layer in the order of COUNT values. From the same (or the same) lower layer device in another way (e.g., when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (or connected to the same MAC layer device in another way or the same logical channel) After performing a header decompression procedure in ascending order of the PDCP serial number or COUNT value with the ROHC context (source base station or target base station) corresponding to the lower layer device with respect to the received data (from the RLC layer device having the identifier)) The duplication detection procedure may be performed and the data may be delivered to an upper layer in the order of COUNT values.

■ 2> All PDCP SDUs with COUNT values less than RX_REORD are delivered.

■ 2> All PDCP SDUs having consecutive COUNT values starting from the RX_REORD value are delivered.

-1> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that has a COUNT value greater than or equal to RX_REORD and has not been transferred to the upper layer.

-1> If the RX_DELIV value is less than the RX_NEXT value,

■ 2> Update the RX_REORD value to the RX_NEXT value.

■ 2> Start the t-Reordering timer.

Another specific operation of the receiving PDCP layer device of the second method for performing the duplicate detection procedure in the above is as follows.

Specifically, if the receiving PDCP layer device has previously received the COUNT value corresponding to the currently received data in the duplication detection procedure, and has previously successfully received the data corresponding to the COUNT value (if integrity protection and verification If the procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred and the received data is discarded to improve the duplicate detection procedure. It can prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received. Successful reception of data above means that the data corresponding to the COUNT value has been processed and stored in a buffer, or has been received and processed and transmitted to an upper layer device, or data has been transmitted to and discarded from an upper layer device. Alternatively, when an integrity protection and verification procedure is set, it may be indicated that integrity verification has been successfully performed on data corresponding to the COUNT value. In other words, since it can be determined that the data has not been successfully received when the integrity verification of the data received by the hacker has failed, normal data may not be discarded in the duplicate detection procedure. A detailed procedure of the receiving PDCP layer device proposed in the present invention is as follows.

When receiving a PDCP PDU from a lower layer, the receiving PDCP layer device determines the COUNT value of the received PDCP PDU as follows.

-1> If the received RCVD_SN is RCVD_SN <= SN(RX_DELIV)-Window_Size

■ 2> Update to RCVD_HFN = HFN(RX_DELIV) + 1.

-1> Otherwise, if RCVD_SN is RCVD_SN> SN(RX_DELIV) + Window_Size

■ 2> RCVD_HFN = HFN(RX_DELIV)-Update to 1.

-1> If not above

■ 2> Update RCVD_HFN = HFN(RX_DELIV).

-1> RCVD_COUNT is determined as RCVD_COUNT = [RCVD_HFN, RCVD_SN].

After determining the COUNT value of the received PDCP PDU, the receiving PDCP layer device updates the window state variables and processes the PDCP PDU as follows.

-1> Decryption is performed on the PDCP PDU using the RCVD_COUNT value, and integrity verification is performed.

■ 2> If integrity verification fails

■ 2> Instructs the higher layer to fail integrity verification and discards the received PDCP Data PDU (the data part of the PDCP PDU).

-1> if RCVD_COUNT <RX_DELIV or

-If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and an integrity protection and verification procedure has been set, and the integrity verification procedure has been successfully performed for the PDCP PDU corresponding to the RCVD_COUNT value. If there is an enemy and if the downlink source data-based data redundancy transmission method or the efficient handover method of the first embodiment is not set,

-If a PDCP PDU having a value of 1> or RCVD_COUNT has been successfully received before and if the integrity protection and verification procedure has not been set, and the downlink original data-based data redundancy transmission method or the efficient handover method of the first embodiment If this is not set

■ Discard the received PDCP Data PDU (the data part of the PDCP PDU).

If the received PDCP PDU is not discarded, the receiving PDCP layer device operates as follows.

-1> The PDCP SDU processed above is stored in the receive buffer.

-1> If RCVD_COUNT >= RX_NEXT

■ 2> Update RX_NEXT to RCVD_COUNT + 1.

-1> If the out of order delivery indicator (outOfOrderDelivery) is set (if out of order delivery operation is indicated),

■ 2> The PDCP SDU is delivered to the upper layer.

-1> If RCVD_COUNT is equal to RX_DELIV

■ 2> Duplicate detection procedure is performed on all currently stored PDCP SDUs (for example, when the original data-based data redundancy transmission or the efficient handover method of the first embodiment is set, the same COUNT value among the currently stored PDCP SDUs is If there are two or more PDCP SDUs, only one PDCP SDU can be left for each COUNT value and the remaining redundant data (PDCP SDUs) can be discarded, ie, PDCP SDUs having the same COUNT value among all stored PDCP SDUs. By performing a duplication detection procedure for a single COUNT value, only one PDCP SDU corresponding to one COUNT value can be stored and only one can be transmitted to an upper layer, and data redundant transmission based on original data or the efficient handover method of the first embodiment. When this is set, the header decompression procedure may also be performed in an ascending order of COUNT values for each data received by each lower RLC layer device.) If header decompression is not performed on the data, the header decompression procedure is performed. (When the header compression procedure is set), the data is transferred to the upper layer in the order of COUNT values. From the same (or the same) lower layer device in another way (e.g., when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (or connected to the same MAC layer device in another way or the same logical channel) After performing a header decompression procedure in ascending order of the PDCP serial number or COUNT value with the ROHC context (source base station or target base station) corresponding to the lower layer device with respect to the received data (from the RLC layer device having the identifier)) The duplication detection procedure may be performed and the data may be delivered to an upper layer in the order of COUNT values.

◆ 3> Starting from the value of COUNT = RX_DELIV, all consecutive PDCP SDUs are delivered to the upper layer.

■ 2> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that is greater than or equal to the current RX_DELIV and has not been delivered to the upper layer.

-1> If the t-Reordering timer is running and the RX_DELIV value is greater than or equal to RX_REORD,

■ 2> Stop and reset the t-Reordering timer.

-1> If the t-Reordering timer is not running (including when it is stopped under the above condition) and RX_DELIV is less than RX_NEXT,

■ 2> Update RX_REORD value to RX_NEXT.

■ 2> Start the t-Reordering timer.

When the PDCP reordering timer (t-Reordering) expires, the receiving PDCP layer device operates as follows.

-1> Perform a duplicate detection procedure for all currently stored PDCP SDUs (for example, if the original data-based data redundancy transmission or the efficient handover method of the first embodiment is set, the same COUNT value among the currently stored PDCP SDUs is set. If there are two or more PDCP SDUs, only one PDCP SDU can be left for each COUNT value and the remaining redundant data (PDCP SDUs) can be discarded, ie, PDCP SDUs having the same COUNT value among all stored PDCP SDUs. By performing a duplication detection procedure for a single COUNT value, only one PDCP SDU corresponding to one COUNT value can be stored and only one can be transmitted to an upper layer, and data redundant transmission based on original data or the efficient handover method of the first embodiment. When this is set, the header decompression procedure may also be performed in an ascending order of COUNT values for each data received by each lower RLC layer device.) If header decompression is not performed on the data, the header decompression procedure is performed. (When the header compression procedure is set), the data is transferred to the upper layer in the order of COUNT values. From the same (or the same) lower layer device in another way (e.g., when a PDCP layer device is connected to a plurality of RLC layer devices, from the same RLC layer device (or connected to the same MAC layer device in another way or the same logical channel) After performing a header decompression procedure in ascending order of the PDCP serial number or COUNT value with the ROHC context (source base station or target base station) corresponding to the lower layer device with respect to the received data (from the RLC layer device having the identifier)) The duplication detection procedure may be performed and the data may be delivered to an upper layer in the order of COUNT values.

■ 2> All PDCP SDUs with COUNT values less than RX_REORD are delivered.

■ 2> All PDCP SDUs having consecutive COUNT values starting from the RX_REORD value are delivered.

-1> Update the RX_DELIV value to the COUNT value of the first PDCP SDU that has a COUNT value greater than or equal to RX_REORD and has not been transferred to the upper layer.

-1> If the RX_DELIV value is less than the RX_NEXT value,

■ 2> Update the RX_REORD value to the RX_NEXT value.

■ 2> Start the t-Reordering timer.

In addition, in the above procedure, the receiving PDCP layer device is from the same (or the same) lower layer device (for example, when the PDCP layer device is connected to a plurality of RLC layer devices, the same RLC layer device (with another method) Decompressing headers in ascending order of PDCP serial number or COUNT value with ROHC context (source base station or target base station) corresponding to the lower layer device for data received from the connected or RLC layer device having the same logical channel identifier)) After performing the procedure, in order to perform the duplication detection procedure, different PDCP windows and PDCP window state variables may be independently operated for data received from each lower layer device. For example, in the embodiment of the present invention, since the receiving PDCP layer device is connected to the RLC layer device for the source base station and the RLC layer device for the target base station, the receiving PDCP layer device is received from the RLC layer device for the source base station. The first PDCP window and the first PDCP window state variables can be operated for the data, and the receiving PDCP layer device is also capable of operating the second PDCP window and the second PDCP window for data received from the RLC layer device for the target base station. 2 PDCP window state variables can be operated. By operating the PDCP window and PDCP state variables independently in this way, data received from each base station can be decrypted with a security key corresponding to each base station, and the data received from each base station are sorted in order, and each received in order or in ascending order. The header decompression procedure can be performed according to the base station, and duplicate PDCP SDUs are discarded by applying a redundant detection procedure to the data received from the source base station and the data received from the target base station until the header compression procedure is completed. The data may be transferred to the upper layer device in ascending order of serial number or COUNT value.

1G may show specific steps of a second embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.

In the second embodiment of the efficient handover method of FIG. 1G, the terminal 1g-20 transmits and receives data with the source base station 1g-05 in the first step (1g-01), and then sends a handover command message from the source base station. Even if received, data can be continuously transmitted and received through the source base station and the protocol layer devices (1g-22) of the first bearer in order to minimize the data interruption time that occurs during handover. I can. When an indicator indicating an improved handover method or an indicator indicating a handover method according to the second embodiment proposed by the present invention is checked in the handover command message, the method according to the second embodiment of the present invention can be applied. In addition, in the handover command message (e.g., RRCReconfiguration message), a new indicator indicating a method of transmitting data redundancy based on original data (PDCP SDU) proposed in the present invention may be defined and indicated to the terminal, and the original data based data redundancy The transmission method or the efficient handover method of the first embodiment may be indicated by separately defining an indicator for each of the downlink or the uplink, and further, an indicator may be separately defined for each bearer or for each PDCP layer device or for each logical channel. I can. If an indicator is defined for each bearer when defining a new indicator in the handover command message, only for a specific service (e.g., only for a specific bearer or PDCP layer device sensitive to transmission delay) The efficient handover method of the first embodiment can be applied to a downlink or an uplink.

In the second embodiment of the present invention, when the first embodiment of the efficient handover method is indicated by the indicator in the handover command message, and the original data-based data redundant transmission method or the efficient handover method of the first embodiment is indicated by the indicator In the following, a specific handover method and procedure is proposed.

In addition, the protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device, 1g-21) of the second bearer for the target base station according to the settings included in the received handover command message. It may be characterized in that it can be set or established in advance. The second bearer may be configured and established to have the same bearer identifier or logical channel identifier as the first bearer so that data interruption time does not occur for each bearer. In addition, in the second embodiment, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may logically operate like one PDCP layer device, and a more detailed operation method is shown in FIG. Explain. When the one PDCP layer device distinguishes between the layer devices of the first bearer and the layer devices of the second bearer, consider that they are connected to different MAC layer devices or have different logical channel identifiers, or Considering that they are different RLC layer devices connected to different MAC layer devices or using different encryption keys, the layer devices of the first bearer (or the first RLC layer device) and By separating layer devices of the second bearer (or second RLC layer devices), encryption or decryption procedures are performed with different security keys for uplink data and downlink data, and different compression protocol contexts are used. It may be characterized by compressing or decompressing.

In addition, in the case where the UE can transmit both the uplink data to the source base station and the target base station in the second embodiment, a coverage reduction problem due to insufficient transmission power of the UE or a transmission resource request to a base station when transmitting uplink data In order to prevent the problem of determining whether to transmit uplink data or not (link selection), the transmission of uplink data in the second embodiment may be characterized in that transmission of uplink data can be transmitted to only one of the source base station and the target base station. . That is, in the first embodiment of the improved handover method proposed in the present invention, uplink data transmission is not simultaneously transmitted to different base stations, and when uplink data transmission is performed to the source base station and the first condition is satisfied, the source base station Switching to the target base station in may perform uplink data transmission to the target base station. Therefore, the terminal performs a scheduling request to only one of the source base station or the target base station, and reports on the size of data to be transmitted from the PDCP layer device (e.g., buffer status report transmission). It may be characterized in that it is possible to transmit uplink data to only one base station by transmitting to only one of the base stations and receiving uplink transmission resources. In addition, even if the terminal receives the handover command message from the source base station, it may be characterized in that it does not initialize the MAC layer device of the first bearer in order to prevent data loss by continuing data transmission and reception due to HARQ retransmission.

In the above, if the original data-based data redundant transmission method or the efficient handover method of the first embodiment is configured for the uplink in the handover command message, the UE uses the first bearer or the second bearer for the uplink data. Data may be transmitted to the source base station and the target base station by applying the original data-based data redundant transmission method or the efficient handover method of the first embodiment. In addition, one receiving PDCP layer device of the source base station and the target base station may process the received data by applying the second method of performing the redundancy detection procedure proposed above.

In the second embodiment of the efficient handover method of FIG. 1G, the terminal 1g-20 is the target base station 1g-10 indicated in the handover command message in the second step (1g-02). Even when performing the random access procedure through the protocol layer devices of the bearer of the UE, the terminal can continue to transmit and receive data (uplink data transmission and downlink data reception) with the source base station through the protocol layer devices of the first bearer. You can do it.

In the second embodiment of the efficient handover method of FIG. 1G, when the terminal 1g-20 satisfies the first condition in the third step (1g-03), the first bearer protocol layer devices 1g -22) to stop transmitting the uplink data to the source base station, and transmit the uplink data to the target base station through the protocol layer devices (1g-21) of the second bearer. The data can be continuously received from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer. In the above, when the terminal stops transmitting uplink data to the source base station through the protocol layer devices 1g-22 of the first bearer, the UE performs an RLC re-establishment procedure for the transmitting RLC layer device among the protocol layer devices. Can be done.

In the above handover command message, if the original data-based data redundant transmission method or the efficient handover method of the first embodiment is set for the downlink, the source base station and the target base station are the first bearer or the second bearer for the downlink data. Through the application of the original data-based data redundant transmission method or the efficient handover method of the first embodiment, data may be transmitted to the terminal. In addition, one receiving PDCP layer device of the terminal may process the received data by applying the second method of performing the duplicate detection procedure proposed above.

In the above, the first condition may be one of the following conditions. The first condition for the UE to switch uplink data transmission from the source base station to the target base station in the third step (1g-03) is as follows.

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

In the above, the downlink from the source base station (or target base station) is characterized in that the terminal can continue to receive downlink data from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer. RLC, not data, through protocol layer devices of the first bearer (or second bearer) for AM bearers so that data can be received smoothly or the source base station (or target base station) can smoothly transmit downlink data. The RLC status report may be characterized by allowing the source base station (or the target base station) to continuously perform transmission on the uplink. This is because, in the case of AM bearers, after transmitting data to the transmitting end, if successful delivery is not indicated by the RLC status report (ie, if the RLC status report is not received), data cannot be continuously transmitted thereafter.

In the second embodiment of the efficient handover method of FIG. 1G, if the terminal 1g-20 satisfies the second condition in the fourth step 1g-04, the terminal 1g -22) may be characterized in that the reception of downlink data from the source base station 1g-05 is stopped. In the above, the second condition may be one of the following conditions.

-When the terminal performs a random access procedure to the target base station through the layer devices (1g-21) of the second bearer and receives a random access response

-When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

-When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

-When the base station sets a separate timer to the terminal in an RRC message, and the timer expires

■ The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response is received from the target base station or handover to the target base station. It may be started when transmitting a completion message or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When data is transmitted through the uplink transmission resource after being allocated or when successful delivery of the transmitted data is confirmed

-When the source base station performs the efficient handover proposed in the present invention, a predetermined method to determine when to stop transmitting downlink data to the terminal or to release the connection with the terminal (for example, when a predetermined timer expires) It can be determined as when (a timer can be started after the handover instruction is instructed) or when an indication that the terminal has successfully performed handover to the target base station from the target base station is received). In addition, if the downlink data is not received from the source base station for a predetermined period of time, the terminal may determine that the connection with the source base station is released and release the connection.

-When the terminal receives an instruction to release the connection with the source base station from the target base station (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU

-When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

-If the terminal does not receive downlink data from the source base station for a predetermined time

-When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or to the terminal When an uplink transmission resource is first indicated

■ For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

◆ When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed. When the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

■ If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

◆ The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a Random Access Response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using a link transmission resource, and a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal performs a random access procedure to the target base station. Since it can be considered that is successfully completed, the UE monitors the PDCCH afterwards and satisfies the first condition when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE or is instructed for the first time. It can be judged that it is. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

■ If the handover command message contains uplink transmission resources for the target base station,

◆ When the terminal transmits message 3 (for example, a handover complete message or an RRCReconfigurationComplete message) to the uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, the random access procedure is performed. It may be determined that it has been successfully completed, and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

■ If the handover command message does not contain uplink transmission resources for the target base station

◆ When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (for example, handover completion Message or RRCReconfigurationComplete message) and receiving a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, it may be determined that the random access procedure has been successfully completed, and that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In the above, if the UE does not indicate HARQ ACK or NACK information for the downlink data after transmitting downlink data to the UE, the source BS may confirm that the UE has stopped receiving downlink data from the source BS. As another method, the UE instructs the source base station to no longer receive downlink data from the source base station by transmitting newly defined MAC control information or RLC control information or PDCP control information or RRC message to the uplink or connects with the source base station. Can be ordered to release.

In addition, the PDCP layer device 1g-21 of the second bearer includes information such as transmission/reception data or serial number information or header compression and decompression context or security key stored in the PDCP layer device 1g-22 of the first bearer. By using, it is possible to continuously perform data transmission and reception with the target base station.

In FIG. 1f of the present invention, when transmitting a handover command message (1f-20) to the terminal, the base station defines indicators for the embodiments proposed in the present invention in the handover command message (for example, RRCReconfiguration message) It is possible to instruct the terminal whether to trigger the handover procedure corresponding to the embodiment, and the terminal performs a handover procedure according to the handover method indicated in the handover command message and minimizes data interruption time to the target base station. Handover can be performed.

In the embodiments of the present invention, when the UE performs data transmission/reception with the source base station through the protocol layer devices of the first bearer and data transmission/reception with the target base station through the protocol layer devices of the second bearer, the first The MAC layer device of the bearer and the MAC layer device of the second bearer operate separate DRX (Discontinuous Reception) periods, respectively, to reduce battery consumption of the terminal. That is, the UE may continue to apply the DRX cycle of the MAC layer device when transmitting and receiving data through the protocol layer devices of the first bearer even after receiving the handover command message, and the first condition or DRX may be stopped according to the second condition. In addition, the UE may separately apply the DRX cycle to the MAC layer device of the second bearer according to the instruction of the target base station.

In addition, in the present invention, the meaning that the terminal stops uplink transmission to the source base station through the protocol layer devices of the first bearer and stops downlink transmission from the source base station means that the protocol layer devices of the first bearer (PHY layer devices) Or, it means that the UE re-establishes, initializes, or releases a MAC layer device, an RLC layer device, or a PDCP layer device.

In the embodiments of the present invention, for convenience of explanation, it has been described that the terminal is configured with a first bearer for a source base station or a second bearer for a target base station, and the terminal is a plurality of first bearers for the source base station. Alternatively, it can be easily extended to a case in which a plurality of second bearers for the target base station are configured and applied equally.

The first or second embodiment of the efficient handover method proposed in the present invention, the original data-based data redundancy transmission method, and the first and second methods of the duplicate detection procedure are easily extended to the case of uplink. Can be applied.

1I and 1J are diagrams illustrating the structure of an efficient PDCP layer device that can be applied to embodiments of the present invention.

In the present invention, the structure of an efficient PDCP layer device as shown in FIGS. 1I and 1J is proposed. The structure of the PDCP layer device can be applied to the first embodiment or the second embodiment of the efficient handover method for minimizing the data interruption time proposed in the present invention.

In FIGS. 1I and 1J, the UE may perform data transmission/reception with the source base station through protocol layer devices of the first bearer, and simultaneously perform data transmission/reception with the target base station through protocol layer devices of the second bearer.

In the above, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may be configured in the terminal, respectively, but logically operate as a single PDCP layer device as shown in FIGS. 1I and 1J. Specifically, the one PDCP layer device may be implemented as an upper PDCP layer device and two lower PDCP layer devices for each source base station and each target base station by dividing functions of the PDCP layer device.

In the above, the upper transmitting PDCP layer device may perform a role of allocating a PDCP serial number to data received from the upper layer device. And header compression can also be performed. In addition, in the two lower transmission PDCP layer devices for each source base station and each target base station, when integrity protection is set using a separate security key set with each source base station and each target base station, the integrity protection procedure is performed in the PDCP header. And data (PDCP SDU), the encryption procedure is applied, and transmitted to the transmission RLC layer device of each of the first bearer or the transmission RLC layer device of the second bearer to perform transmission. In the above, the two lower transmission PDCP layer devices may be characterized in that they may perform parallel processing of header compression or integrity protection or encryption procedures in parallel to accelerate data processing speed. It may be characterized in that the two lower transmission PDCP layer devices perform the integrity protection or encryption procedure using different security keys. In addition, it may be characterized in that the integrity protection or encryption procedure of different data is performed by logically applying different security keys or security algorithms in one transmitting PDCP layer device.

In the above, the upper receiving PDCP layer device performs a duplicate detection function on the data received from the lower layer devices based on the PDCP serial number, or arranges the order of the received data in ascending order of the PDCP serial number to order the upper layer. It can play the role of delivering as it is. In addition, header compression may be decompressed. In addition, in the two lower receiving PDCP layer devices for each source base station and each target base station, when integrity protection is set using a separate security key set with each source base station and each target base station, the integrity verification procedure is performed in the PDCP header. It is applied to and data (PDCP SDU), a decoding procedure is applied, and transmitted to an upper receiving PDCP layer device to perform data processing. In the two lower receiving PDCP layer devices, in order to reduce unnecessary integrity verification or decoding procedures, a window is driven based on the PDCP serial number to discard data outside the window and redundant data is first performed, and valid data in the window is performed. It is also possible to perform the integrity verification or decryption procedure for only those. The two lower receiving PDCP layer devices each perform a header compression or integrity protection or encryption procedure in parallel in order to accelerate the data processing speed in the two lower transmitting PDCP layer devices based on the PDCP serial number. Parallel processing) may be performed, and the integrity protection or encryption procedure may be performed by using different security keys in the two lower transmission PDCP layer devices. In addition, it may be characterized in that the integrity protection or encryption procedure of different data is performed by logically applying different security keys or security algorithms in one transmitting PDCP layer device. In addition, the lower receiving PDCP layer devices may perform an out-of-sequence deciphering or integrity verification procedure for each data received regardless of the order of the PDCP serial numbers.

In the embodiments of the PDCP layer device procedure proposed in the present invention, the upper PDCP layer device has a common header compression protocol context (for example, ROHC context) for data transmitted in the PDCP layer device structure as shown in FIG. And each of the lower PDCP layer devices 1i-21 and 1i-22 may be extended and applied to a structure in which each encryption procedure is performed by using different security keys.

As another method, in order to parallelly process the encryption or decryption procedure for data to be processed with different security keys, two devices or processors may perform an encryption or decryption procedure for each data having different security keys.

As another method, in order to uniformly process the encryption or decryption procedure for data that needs to be processed with different security keys, a security key every time to perform the encryption or decryption procedure for each data having different security keys with one device or processor. You can process the data by changing it to suit each data.

In order to process the header compression or header decompression procedure in parallel for data that needs to be processed in different header compression contexts in another way, each data that needs to be processed in different header compression contexts by two devices or processors A header compression or header decompression procedure may be performed.

In another way, in order to uniformly process the header compression or header decompression procedure for data that needs to be processed in different header compression contexts, each header for data that needs to be processed in different header compression contexts by one device or processor Data can be processed by changing the compression context according to each data.

In addition, the embodiments of the PDCP layer device procedure proposed in the present invention, for the data received in the PDCP layer device structure as shown in FIG. 1i, each lower PDCP layer device (1i-21, 1i-22) is a different security key. It can be extended and applied to a structure in which each decoding procedure is performed by using and a higher PDCP layer device performs a header compression decompression procedure with a common header compression protocol context (eg, ROHC context).

1K is a diagram illustrating a terminal operation applicable to embodiments proposed in the present invention.

In FIG. 1K, when the terminal 1k-05 receives a handover command message, if the message includes an indicator indicating the first embodiment of the efficient handover method, the terminal is the second bearer for the indicated target base station. Even when setting and establishing protocol layer devices and performing a random access procedure to a target base station through the established protocol layer devices (1k-10, 1k-15), the UE and the source base station through the protocol layer devices of the first bearer. Data transmission/reception (uplink data transmission and downlink data reception) can be continued (1k-20). In addition, if an indicator indicating the method for transmitting duplicate original data based on the original data or the efficient handover method of the first embodiment is set in the message, the receiving PDCP layer device of the terminal performs a duplicate detection procedure on the received data. Apply the second method. However, if an indicator indicating the original data-based data redundant transmission method or the efficient handover method of the first embodiment is not set in the handover command message for the downlink, the receiving PDCP layer device of the terminal duplicates the received data. The first method of performing the detection procedure is applied.

If the terminal satisfies the first condition, it stops transmitting the uplink data to the source base station through the protocol layer devices of the first bearer and uplinks through the protocol layer devices (1g-21) of the second bearer. It is characterized in that link data is transmitted to the target base station, and the downlink data can be continuously received from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer (1k- 30).

If the first condition is not satisfied above, the first condition can be checked while continuing to perform the existing procedure.

In addition, if the second condition is satisfied, the UE may stop receiving downlink data from the source base station 1g-05 through the protocol layer devices of the first bearer (1k-45). In addition, the PDCP layer device 1g-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1g-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

If the second condition is not satisfied, the second condition can be checked while continuing to perform the existing procedure.

The operation of the terminal or the base station according to the embodiment of the present invention is as follows.

-If an indicator indicating the first embodiment of the efficient handover method is included in the received handover command message

■ The source base station and the target base station perform operations according to the first embodiment of the handover method

■ The terminal performs the operation according to the first embodiment of the efficient handover method

■ The receiving PDCP layer device of the terminal applies the first method of performing a duplicate detection procedure

-If an indicator indicating the second embodiment of the efficient handover method is included in the received handover command message, or an indicator indicating the first embodiment of the efficient handover method and a downlink source data-based data redundant transmission method Or, if an indicator indicating the efficient handover method of the first embodiment is included

■ The source base station and the target base station perform operations according to the second embodiment of the efficient handover method

■ The source base station and the target base station apply the original data-based data redundant transmission method or the efficient handover method of the first embodiment.

■ The terminal performs the operation according to the second embodiment of the efficient handover method

■ The receiving PDCP layer device of the terminal applies the second method of performing a duplicate detection procedure

1L shows the structure of a terminal to which an embodiment of the present invention can be applied.

Referring to the drawing, the terminal includes a radio frequency (RF) processing unit 1l-10, a baseband, a processing unit 1l-20, a storage unit 1l-30, and a control unit 1l-40. do.

The RF processing unit 1l-10 performs a function of transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processing unit 1l-10 up-converts the baseband signal provided from the baseband processing unit 1l-20 to an RF band signal and then transmits it through an antenna, and the RF band signal received through the antenna Is down-converted to a baseband signal. For example, the RF processing unit 1l-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), and the like. I can. In the drawing, only one antenna is shown, but the terminal may include a plurality of antennas. In addition, the RF processing unit 1l-10 may include a plurality of RF chains. Further, the RF processing unit 1l-10 may perform beamforming. For the beamforming, the RF processing unit 1l-10 may adjust a phase and a magnitude of each of signals transmitted/received through a plurality of antennas or antenna elements. In addition, the RF processing unit may perform MIMO, and may receive multiple layers when performing the MIMO operation. The RF processing unit 1l-10 may perform reception beam sweeping by appropriately setting a plurality of antennas or antenna elements under the control of the controller, or adjust the direction and beam width of the reception beam so that the reception beam cooperates with the transmission beam. have.

The baseband processing unit 1l-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the system. For example, when transmitting data, the baseband processing unit 11-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 11-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 11-10. For example, in the case of the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit 11-20 generates complex symbols by encoding and modulating a transmission bit stream, and subcarriers the complex symbols. After mapping to, OFDM symbols are constructed through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processing unit 11-20 divides the baseband signal provided from the RF processing unit 11-10 in units of OFDM symbols, and applies a fast Fourier transform (FFT) operation to subcarriers. After reconstructing the mapped signals, the received bit stream is restored through demodulation and decoding.

The baseband processing unit 11-20 and the RF processing unit 11-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 11-20 and the RF processing unit 11-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, or a communication unit. Further, at least one of the baseband processing unit 11-20 and the RF processing unit 11-10 may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit 1l-20 and the RF processing unit 1l-10 may include different communication modules to process signals of different frequency bands. For example, the different radio access technologies may include an LTE network, an NR network, and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.5GHz, 5Ghz) band, and a millimeter wave (eg, 60GHz) band.

The storage unit 1l-30 stores data such as a basic program, an application program, and setting information for the operation of the terminal. The storage unit 1l-30 provides stored data at the request of the control unit 1l-40.

The control unit 1l-40 controls overall operations of the terminal. For example, the control unit 1l-40 transmits and receives signals through the baseband processing unit 1l-20 and the RF processing unit 1l-10. In addition, the control unit 1l-40 writes and reads data in the storage unit 1l-40. To this end, the control unit 1l-40 may include at least one processor. For example, the control unit 1l-40 may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls an upper layer such as an application program.

1M is a block diagram of a TRP in a wireless communication system to which an embodiment of the present invention can be applied.

As shown in the figure, the base station includes an RF processing unit (1m-10), a baseband processing unit (1m-20), a backhaul communication unit (1m-30), a storage unit (1m-40), and a control unit (1m-50). Consists of including.

The RF processing unit 1m-10 performs a function of transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processing unit (1m-10) up-converts the baseband signal provided from the baseband processing unit (1m-20) to an RF band signal and then transmits it through an antenna, and an RF band signal received through the antenna. Downconverts to a baseband signal. For example, the RF processing unit 1m-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. In the drawing, only one antenna is shown, but the first access node may include a plurality of antennas. In addition, the RF processing unit 1m-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1m-10 may perform beamforming. For the beamforming, the RF processing unit 1m-10 may adjust a phase and a magnitude of each of signals transmitted and received through a plurality of antennas or antenna elements. The RF processor may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 1m-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the first wireless access technology. For example, when transmitting data, the baseband processing unit 1m-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1m-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1m-10. For example, in the case of the OFDM scheme, when transmitting data, the baseband processing unit 1m-20 generates complex symbols by encoding and modulating a transmission bit stream, mapping the complex symbols to subcarriers, and then IFFT OFDM symbols are configured through calculation and CP insertion. In addition, when receiving data, the baseband processing unit 1m-20 divides the baseband signal provided from the RF processing unit 1m-10 in units of OFDM symbols, and reconstructs signals mapped to subcarriers through FFT operation. After that, the received bit stream is restored through demodulation and decoding. The baseband processing unit 1m-20 and the RF processing unit 1m-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1m-20 and the RF processing unit 1m-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, a communication unit, or a wireless communication unit.

The communication unit 1m-30 provides an interface for performing communication with other nodes in the network.

The storage unit 1m-40 stores data such as a basic program, an application program, and setting information for the operation of the main station. In particular, the storage unit 1m-40 may store information on bearers allocated to the connected terminal, measurement results reported from the connected terminal, and the like. In addition, the storage unit 1m-40 may store information that is a criterion for determining whether to provide multiple connections to the terminal or to stop. In addition, the storage unit 1m-40 provides stored data at the request of the control unit 1m-50.

The control unit 1m-50 controls overall operations of the main station. For example, the control unit 1m-50 transmits and receives signals through the baseband processing unit 1m-20 and the RF processing unit 1m-10 or through the backhaul communication unit 1m-30. In addition, the control unit 1m-50 writes and reads data in the storage unit 1m-40. To this end, the control unit 1m-50 may include at least one processor.

Meanwhile, in the present invention, a header decompression failure problem that may occur when handover is performed in a next-generation mobile communication system is considered for each scenario, and a base station operation or a terminal operation capable of preventing the header compression failure problem is proposed.

2A is a diagram illustrating a structure of an LTE system to which the present invention can be applied.

Referring to Figure 2a, as shown, the radio access network of the LTE system is a next-generation base station (Evolved Node B, hereinafter ENB, Node B or base station) (2a-05, 2a-10, 2a-15, 2a-20) and It is composed of MME (2a-25, Mobility Management Entity) and S-GW (2a-30, Serving-Gateway). User Equipment (hereinafter referred to as UE or terminal) 2a-35 accesses an external network through ENBs 2a-05 to 2a-20 and S-GW 2a-30.

In FIG. 2A, ENBs 2a-05 to 2a-20 correspond to the existing node B of the UMTS system. The ENB is connected to the UEs 2a-35 through a radio channel and performs a more complex role than the existing Node B. In the LTE system, all user traffic including real-time services such as VoIP (Voice over IP) through the Internet protocol are serviced through a shared channel, so status information such as buffer status, available transmission power status, and channel status of UEs A device that collects and performs scheduling is needed, and ENB (2a-05 ~ 2a-20) is in charge of this. One ENB typically controls multiple cells. For example, in order to implement a transmission rate of 100 Mbps, the LTE system uses, for example, an orthogonal frequency division multiplexing (OFDM) in a 20 MHz bandwidth as a radio access technology. In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied. The S-GW 2a-30 is a device that provides a data bearer, and creates or removes a data bearer under the control of the MME 2a-25. The MME is a device responsible for various control functions as well as mobility management functions for a terminal, and is connected to a plurality of base stations.

2B is a diagram showing a radio protocol structure in an LTE system to which the present invention can be applied.

Referring to Figure 2b, the radio protocol of the LTE system is PDCP (Packet Data Convergence Protocol 2b-05, 2b-40), RLC (Radio Link Control 2b-10, 2b-35), MAC (Medium Access Control 2b-15, 2b-30). PDCP (Packet Data Convergence Protocol) (2b-05, 2b-40) is in charge of operations such as IP header compression/restore. The main functions of PDCP are summarized as follows.

-Header compression and decompression (ROHC only)

-Transfer of user data

-In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM

-Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

-Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM

-Retransmission of PDCP SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM

-Encryption and decryption function (Ciphering and deciphering)

-Timer-based SDU discard in uplink.

Radio Link Control (hereinafter referred to as RLC) (2b-10, 2b-35) performs an ARQ operation by reconfiguring a PDCP packet data unit (PDU) to an appropriate size. The main functions of RLC are summarized as follows.

-Data transfer function (Transfer of upper layer PDUs)

-ARQ function (Error Correction through ARQ (only for AM data transfer))

-Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)

-Re-segmentation of RLC data PDUs (only for AM data transfer)

-Reordering of RLC data PDUs (only for UM and AM data transfer)

-Duplicate detection (only for UM and AM data transfer)

-Error detection function (Protocol error detection (only for AM data transfer))

-RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

-RLC re-establishment

The MACs 2b-15 and 2b-30 are connected to several RLC layer devices configured in one terminal, and perform an operation of multiplexing RLC PDUs to MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC are summarized as follows.

-Mapping between logical channels and transport channels

-Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels

-Scheduling information reporting function

-HARQ function (Error correction through HARQ)

-Priority handling between logical channels of one UE

-Priority handling between UEs by means of dynamic scheduling

-MBMS service identification

-Transport format selection

-Padding function

The physical layer (2b-20, 2b-25) channel-codes and modulates upper layer data, converts it into OFDM symbols, and transmits it to the radio channel, or demodulates OFDM symbols received through the radio channel and decodes the channel and transmits it to the upper layer Do the action.

2C is a diagram showing the structure of a next-generation mobile communication system to which the present invention can be applied.

Referring to Figure 2c, as shown, the radio access network of the next-generation mobile communication system (hereinafter NR or 5G) is a next-generation base station (New Radio Node B, hereinafter NR gNB or NR base station) 2c-10 and NR CN (2c). -05, New Radio Core Network). The user terminal (New Radio User Equipment, hereinafter NR UE or terminal) 2c-15 accesses the external network through the NR gNB 2c-10 and the NR CN 2c-05.

In FIG. 2c, the NR gNB 2c-10 corresponds to the eNB (Evolved Node B) of the existing LTE system. The NR gNB is connected to the NR UE (2c-15) through a radio channel and can provide a service superior to that of the existing Node B. In the next-generation mobile communication system, all user traffic is serviced through a shared channel, so a device that collects and schedules status information such as buffer status, available transmission power status, and channel status of UEs is required. (2c-10) is in charge. One NR gNB typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the current LTE, it may have more than the existing maximum bandwidth, and a beamforming technology may be additionally grafted using Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology. . In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied. The NR CN (2c-05) performs functions such as mobility support, bearer setup, and QoS setup. The NR CN is a device responsible for various control functions as well as mobility management functions for a terminal, and is connected to a plurality of base stations. In addition, the next-generation mobile communication system can be interlocked with the existing LTE system, and the NR CN is connected to the MME (2c-25) through a network interface. The MME is connected to the existing eNB (2c-30).

2D is a diagram showing a radio protocol structure of a next-generation mobile communication system to which the present invention can be applied. .

Referring to Figure 2d, the radio protocol of the next-generation mobile communication system is NR SDAP (2d-01, 2d-45), NR PDCP (2d-05, 2d-40), NR RLC (2d-10) in the terminal and the NR base station, respectively. , 2d-35), NR MAC (2d-15, 2d-30).

The main functions of the NR SDAP (2d-01, 2d-45) may include some of the following functions.

-Transfer of user plane data

-Mapping between a QoS flow and a DRB for both DL and UL for uplink and downlink

-Marking QoS flow ID for uplink and downlink (marking QoS flow ID in both DL and UL packets)

-A function of mapping a relective QoS flow to a data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

For the SDAP layer device, the UE may be configured with an RRC message to set whether to use the header of the SDAP layer device or the function of the SDAP layer device for each PDCP layer device, bearer or logical channel, and the SDAP header. If is set, the UE uses the NAS QoS reflective configuration 1-bit indicator (NAS reflective QoS) in the SDAP header and the AS QoS reflective configuration 1-bit indicator (AS reflective QoS) to map the QoS flow and data bearer of the uplink and downlink. Can be instructed to update or reset. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used as data processing priority, scheduling information, etc. to support smooth service.

The main functions of NR PDCP (2d-05, 2d-40) may include some of the following functions.

Header compression and decompression (ROHC only)

-Transfer of user data

-In-sequence delivery of upper layer PDUs

-Out-of-sequence delivery of upper layer PDUs

-Order reordering function (PDCP PDU reordering for reception)

-Duplicate detection of lower layer SDUs

-Retransmission of PDCP SDUs

-Encryption and decryption function (Ciphering and deciphering)

-Timer-based SDU discard in uplink.

In the above, the reordering function of the NR PDCP device refers to a function of rearranging the PDCP PDUs received from the lower layer in order based on the PDCP sequence number (SN), and the function of delivering data to the upper layer in the rearranged order. It may include, or may include a function of immediately delivering without considering the order, may include a function of recording lost PDCP PDUs by rearranging the order, and reporting the status of lost PDCP PDUs It may include a function of performing the transmission side, and may include a function of requesting retransmission of lost PDCP PDUs.

The main functions of the NR RLC (2d-10, 2d-35) may include some of the following functions.

-Data transfer function (Transfer of upper layer PDUs)

-In-sequence delivery of upper layer PDUs

-Out-of-sequence delivery of upper layer PDUs

-ARQ function (Error Correction through ARQ)

-Concatenation, segmentation and reassembly of RLC SDUs

-Re-segmentation of RLC data PDUs

-Reordering of RLC data PDUs

-Duplicate detection

-Protocol error detection

-RLC SDU discard function (RLC SDU discard)

-RLC re-establishment

In the above, the in-sequence delivery function of the NR RLC device refers to the function of delivering RLC SDUs received from the lower layer to the upper layer in order, and originally, one RLC SDU is divided into several RLC SDUs and received. If so, it may include a function of reassembling and delivering it, and may include a function of rearranging the received RLC PDUs based on RLC sequence number (SN) or PDCP sequence number (SN), and rearranging the order It may include a function of recording lost RLC PDUs, may include a function of reporting a status of lost RLC PDUs to a transmitting side, and a function of requesting retransmission of lost RLC PDUs. If there is a lost RLC SDU, it may include a function of transferring only RLC SDUs before the lost RLC SDU to a higher layer in order, or if a predetermined timer expires even if there is a lost RLC SDU, the timer It may include a function of delivering all RLC SDUs received before the start of the system in order to the upper layer, or if a predetermined timer expires even if there is a lost RLC SDU, all RLC SDUs received so far are sequentially transferred to the upper layer. It may include the ability to deliver. In addition, RLC PDUs may be processed in the order in which they are received (regardless of the order of serial number and sequence number, in the order of arrival) and delivered to the PDCP device regardless of the order (Out-of sequence delivery). Segments stored in a buffer or to be received in the future may be received, reconstructed into one complete RLC PDU, processed, and delivered to the PDCP device. The NR RLC layer may not include a concatenation function, and the function may be performed in the NR MAC layer or may be replaced with a multiplexing function of the NR MAC layer.

In the above, the out-of-sequence delivery function of the NR RLC device refers to a function of directly delivering RLC SDUs received from the lower layer to the upper layer regardless of the order, and originally, one RLC SDU is When it is divided into SDUs and received, it may include a function of reassembling and transmitting them, and includes a function of storing the RLC SN or PDCP SN of the received RLC PDUs, sorting the order, and recording the lost RLC PDUs. I can.

The NR MACs 2d-15 and 2d-30 may be connected to several NR RLC layer devices configured in one terminal, and the main functions of the NR MAC may include some of the following functions.

-Mapping between logical channels and transport channels

-Multiplexing and demultiplexing function (Multiplexing/demultiplexing of MAC SDUs)

-Scheduling information reporting function

-HARQ function (Error correction through HARQ)

-Priority handling between logical channels of one UE

-Priority handling between UEs by means of dynamic scheduling

-MBMS service identification

-Transport format selection

-Padding function

The NR PHY layer (2d-20, 2d-25) channel-codes and modulates upper layer data, converts it into OFDM symbols, and transmits it to the radio channel, or demodulates and channel-decodes OFDM symbols received through the radio channel to the upper layer. You can perform the transfer operation.

FIG. 2E is a diagram illustrating a procedure for establishing a connection with a network by switching from an RRC idle mode to an RRC connected mode by a terminal in the present invention.

In FIG. 2e, the base station may send an RRCConnectionRelease message to the terminal when the terminal transmitting and receiving data in the RRC connected mode does not transmit or receive data for a predetermined reason or for a predetermined period of time to switch the terminal to the RRC idle mode (2e-01). In the future, when the current connection is not established (hereinafter, idle mode UE), when data to be transmitted occurs, it performs an RRC connection establishment process with the base station. The UE establishes uplink transmission synchronization with the base station through a random access process and transmits an RRCConnectionRequest message to the base station (2e-05). In the message, the identifier of the terminal and the reason for establishing a connection (establishmentCause) are stored. The base station transmits an RRCConnectionSetup message so that the terminal establishes an RRC connection (2e-10).

The message includes configuration information for each service/bearer/each RLC device or logical channel or for each bearer, whether to use ROHC for each bearer/logical channel, and ROHC configuration information (e.g., ROHC version, initial information, etc. ), statusReportRequired information (information that the base station instructs the PDCP Status report to the terminal), drb-ContinueROHC information (configuration information to keep and use the ROHC configuration information as it is, included in the PDCP layer device configuration information (pdcp-config) to be transmitted. Can). In addition, RRC connection configuration information and the like are stored in the message. The bearer for the RRC connection is also referred to as SRB (Signaling Radio Bearer), and is used for transmission and reception of an RRC message, which is a control message between the terminal and the base station.

The terminal that has established the RRC connection transmits an RRCConnetionSetupComplete message to the base station (2e-15). The message includes a control message called SERVICE REQUEST that requests the MME to set up a bearer for a predetermined service. The base station transmits the SERVICE REQUEST message contained in the RRCConnetionSetupComplete message to the MME or AMF (2e-20), and the MME or AMF determines whether to provide the service requested by the terminal. As a result of the determination, if the terminal determines to provide the requested service, the MME or AMF transmits an INITIAL CONTEXT SETUP REQUEST message to the base station (2e-25). The message includes information such as QoS (Quality of Service) information to be applied when setting up a Data Radio Bearer (DRB), and security-related information (for example, Security Key, Security Algorithm) to be applied to the DRB.

In addition, when the base station has not received the capability information of the UE from the MME or AMF, the base station may transmit a UE capability information request message to the UE to check capability information of the UE (2e-26). Upon receiving the UE capability information request message, the UE may construct and generate a UE capability information message and report it to the base station (2e-27). The terminal capability information message may include what types of handover methods the terminal supports. For example, an indicator for each handover method may be defined in the terminal capability information report message, and handover methods supported by the terminal may be indicated by the indicator to report whether each handover method is supported to the base station. When the base station checks the terminal capability information, the base station considers the reported UE capability using an indicator defined for each handover method in a handover command message (e.g., RRCReconfiguration message) when instructing the UE to handover. Thus, it is possible to set which handover method to indicate to the terminal. The terminal may perform a handover procedure to the target base station according to the handover method indicated in the handover command message. In addition, the terminal capability information message may include whether the terminal supports a header compression method or protocol for uplink or downlink. And based on the terminal capability information, the base station may set a header compression method for uplink or downlink for each bearer or for each PDCP layer device to the terminal in the RRCReconfiguration message (for example, a handover command message).

The base station exchanges a SecurityModeCommand message (2e-30) and a SecurityModeComplete message (2e-35) to configure security with the terminal. When the security configuration is completed, the base station transmits an RRCConnectionReconfiguration message to the terminal (2e-40).

The message includes configuration information for each service/bearer/each RLC device or logical channel or for each bearer, whether to use ROHC for each bearer/logical channel, and ROHC configuration information (e.g., ROHC version, initial information, etc. ), statusReportRequired information (information that the base station instructs the PDCP Status report to the terminal), drb-ContinueROHC information (configuration information to keep and use the ROHC configuration information as it is, included in the PDCP layer device configuration information (pdcp-config) to be transmitted. Can). In addition, RRC connection configuration information and the like are stored in the message. The bearer for the RRC connection is also referred to as SRB (Signaling Radio Bearer), and is used for transmission and reception of an RRC message, which is a control message between the terminal and the base station.

In addition, the message includes configuration information of a DRB to which user data is to be processed, and the terminal applies the information to configure the DRB and transmits an RRCConnectionReconfigurationComplete message to the base station (2e-45). The base station after completing the DRB setup with the terminal transmits an INITIAL CONTEXT SETUP COMPLETE message to the MME or AMF (2e-50), and the MME or AMF that receives it transmits the S1 BEARER SETUP message and S1 to set the S-GW and S1 bearer. Exchange BEARER SETUP RESPONSE messages (2e-055, 2e-60). The S1 bearer is a connection for data transmission established between the S-GW and the base station, and corresponds to DRB and 1:1. When all of the above processes are completed, the terminal transmits and receives data to and from the base station through the S-GW (2e-65, 2e-70). This general data transmission process is largely composed of three steps: RRC connection setup, security setup, and DRB setup. In addition, the base station may transmit an RRC Connection Reconfiguration message to the terminal for a predetermined reason to refresh, add, or change the configuration (2e-75).

In the present invention, a bearer may mean including SRB and DRB, SRB means Signaling Radio Bearer, and DRB means Data Radio Bearer. The SRB is mainly used to transmit and receive RRC messages of the RRC layer device, and the DRB is mainly used to transmit and receive user layer data. In addition, UM DRB refers to a DRB using an RLC layer device operating in an UM (Unacknowledged Mode) mode, and AM DRB refers to a DRB using an RLC layer device operating in an AM (Acknowledged Mode) mode.

2F is a diagram illustrating signaling procedures for performing handover in a next generation mobile communication system.

The terminal (2f-01) in the RRC connected mode state reports the cell measurement information (Measurement Report) to the current source base station (Source eNB, 2f-02) when a periodic or specific event is satisfied (2f-05). Based on the measurement information, the source base station determines whether or not the terminal performs handover to an adjacent cell. Handover is a technology for changing a source base station providing a service to a terminal in a connected mode state to another base station (or another cell of the same base station). If the source base station determines handover, the source base station sends a handover request message (HO (Handover) request) message to a new base station that will provide service to the terminal, that is, a target base station (Traget eNB, 2f-03) to handover. Is requested (2f-10).

The handover request message may include a handover method supported or preferred by a source base station or a plurality of handover methods, and may include an indicator requesting a handover method preferred by the target base station as another method.

If the target base station accepts the handover request, it transmits a handover request acceptance (HO request Ack) message to the source base station (2f-15).

The handover request acceptance message may include a handover method included by the source base station in the handover request message or a handover method supported (or preferred or indicated) by a target base station among a plurality of handover methods. The base station may instruct the terminal of the handover method indicated by the target base station in the handover request acceptance message. As another method, the target base station may configure the source base station and the terminal to perform the indicated handover method by indicating a handover method supported by the target base station as an indicator in the handover request acceptance message.

Upon receiving the message, the source base station transmits a handover command message (HO command message) to the terminal (2f-20). The handover command (HO command) message is transmitted from the source base station to the terminal using an RRC Connection Reconfiguration message (2f-20).

By using an indicator defined for each handover method in the handover command message (for example, an RRCReconfiguration message), the base station may set a handover method to the terminal in consideration of the terminal capability. The terminal may perform a handover procedure to the target base station according to the handover method indicated in the handover command message.

Upon receiving the message, the terminal stops transmitting and receiving data with the source base station and starts a timer T304. In T304, if the terminal does not succeed in handover to the target base station for a predetermined time, it returns to the original configuration of the terminal and switches to the RRC Idle state. The source base station delivers a sequence number (SN) status for uplink/downlink data and, if there is downlink data, transfers it to the target base station (2f-30, 2f-35). The terminal attempts random access to the target cell indicated by the source base station (2f-40). The random access is for notifying the target cell that the terminal is moving through handover and at the same time to synchronize uplink synchronization. For the random access, the terminal transmits a preamble ID provided from the source base station or a preamble corresponding to a randomly selected preamble ID to the target cell. After transmission of the preamble, after a specific number of subframes have passed, the UE monitors whether a random access response message (RAR) is transmitted from the target cell. The time interval to be monitored is referred to as a random access response window (RAR window). During the specific time, if a random access response (RAR) is received (2f-45). The terminal transmits a handover complete (HO complete) message to the target base station as an RRC Reconfiguration Complete message (2f-55). When the random access response is successfully received from the target base station as described above, the terminal terminates the T304 timer (2f-50). The target base station requests path modification to correct the paths of bearers set as the source base station (2f-60, 2f-65), and notifies the source base station to delete the UE context of the terminal (2f-70). Accordingly, the terminal attempts to receive data from the start of the RAR window to the target base station, and after receiving the RAR, transmits an RRC Reconfiguration Complete message and starts data transmission and reception with the target base station.

In the following of the present invention, in order to prevent a header decompression failure problem that may occur during handover in a next-generation mobile communication system, a specific solution is proposed in various embodiments.

FIG. 2G is a diagram illustrating a header compression or decompression procedure when PDCP layer devices of a transmitting end and a receiving end use the ROHC protocol in the handover procedure as shown in FIG. 2F.

In Figure 2g, the out of order delivery (out of delivery) indicator is not set as an RRC message, and a transmitting or receiving PDCP layer device (AM DRB, AM Data radio bearer) connected or configured with an RLC device supporting AM mode or UM mode is If a connection with the source base station is established and the base station has set up to use the ROHC protocol before transmitting data (can be set with an RRC message as shown in Fig. 2e or 2f), the transmitting PDCP layer device sets the bearer or sets the ROHC protocol. After completing, construct an IR packet and transmit it, the PDCP layer device at the receiving end synchronizes the ROHC protocol with the transmitting end by receiving it. That is, the ROHC protocol for data received by checking and storing all header information of the upper layer header (for example, TCP/IP header) and setting information related to the ROHC protocol for compression or decompression (for example, ROCH context). Used to decompress the compressed header (2g-05).

In 2g-05, the synchronization between the ROHC protocol of the PDCP device at the transmitting end and the ROHC protocol of the PDCP device at the receiving end are synchronized, and the data transmitted by compressing a higher layer header (e.g., TCP/IP header) with the ROHC protocol at the transmitting end are converted to the ROHC protocol It can be decompressed and restored to be delivered to an upper layer. In the above, the IR (Initialization and Refresh) packet may be included in data and transmitted, and the transmitting PDCP layer device includes compression setting information for compression or decompression to the receiving PDCP layer device. Therefore, if the IR packet is not successfully delivered to the receiving PDCP layer device, a header decompression error may occur for the received data. That is, the header decompression failure problem described in the present invention is when the header compression context (ROHC context) is not used as it is during handover, or in the RRC message (for example, RRCReconfiguration message) indicating handover, the header compression context is This occurs only when an indicator to use as it is (for example, drb-ContinueROHC) is not set or not indicated, or when the header compression protocol is initialized. Therefore, the methods proposed in the present invention may be applied only when the header decompression failure problem occurs. That is, if the header compression context (ROHC context) is used as it is during handover, or the header compression protocol is not initialized, the methods proposed in the present invention need not be applied unnecessarily. As another method, for convenience of implementation, the methods proposed in the present invention may always be applied when performing handover.

2H is a diagram illustrating a first embodiment in which a header decompression failure problem may occur with respect to downlink data during handover in the present invention.

In FIG. 2H, when the terminal 2h-03 receives a handover command message from the source base station 2h-01, it performs the handover method indicated in the handover command message and performs a handover procedure to the target base station 2h-02. Perform.

In the above, in the first embodiment of the present invention, an embodiment of a specific procedure in which a base station and a terminal transmit and receive data in a handover procedure is as follows.

-Step 1: The source base station transmits data (for example, PDCP PDU or PDCP SDU) having a PDCP serial number or COUNT value of 100 to 110 to the terminal through the downlink. However, it is not possible to receive a confirmation that data corresponding to Nos. 100 to 110 has been successfully delivered to the UE (eg, RLC ACK of an RLC Status report). In addition, the source base station instructs the handover by transmitting a handover command message (eg, RRCReconfiguration message) to the terminal.

-Step 2: In the first step, the source base station transfers all data to the target base station in ascending order from data that has not received confirmation of successful delivery or data having the lowest PDCP serial number or COUNT value that has not received confirmation of successful delivery. Transfer to the terminal to perform transmission or retransmission.

-Step 3: The target base station performs data processing in the PDCP layer device on the data (e.g., PDCP SDU) received from the source base station, and, for example, the transmitting PDCP layer device of the target base station targets the data. Header compression may be performed based on the ROHC context of the base station, integrity protection or encryption procedure may be performed based on the security key of the target base station, and data may be delivered to a lower layer. In the above, in order to initialize or synchronize the header compression context, the target base station may perform data processing by configuring an IR packet in data corresponding to a PDCP serial number or COUNT value from 100 to 104. More specifically, in the above, the header compression protocol is in U mode (U-mode, a mode in which the receiving end does not request feedback (ACK or NACK) in unidirectional mode) or R mode (the receiving end receives ACK or NACK in R-mode, Reliable mode). Sending mode) or O mode (a mode in which the receiver sends NACK in O-mode, Optimistic mode), or when operating in an IR state (IR state) can generate and transmit IR packets. In addition, data from #105 to #130 may be compressed based on the header compression context, integrity protected or encrypted, and transmitted to a lower layer or prepared for transmission. In the above, the IR (Initialization and Refresh) packet may be included in data and transmitted, and the transmitting PDCP layer device includes compression setting information for compression or decompression to the receiving PDCP layer device. Therefore, if the IR packet is not successfully delivered to the receiving PDCP layer device, a header decompression error may occur for the received data.

-Step 4: After receiving the handover command message from the source base station, the terminal completes the handover procedure to the target base station according to the handover method or handover configuration information indicated in the handover command message, and then to the target base station. A handover completion message (eg, an RRCReconfigurationComplete message) may be transmitted, and a PDCP status report may be configured and transmitted for each PDCP layer device or bearer. In the PDCP status report, a status report indicating that from 100 to 110 of the PDCP serial number or COUNT value has been successfully received from the source base station may be performed.

-Step 5: Upon receiving the PDCP status report from the above, the target base station discards the received data for successful delivery. Accordingly, data corresponding to the PDCP serial number or COUNT value 100 to 110 are discarded, and data corresponding to the PDCP serial number or COUNT value 111 to 130 may be transmitted to the terminal.

-Step 6: In the above, the terminal receives and decodes data corresponding to the PDCP serial number or COUNT value 111 to 130 from the target base station, and if integrity protection is set, performs a header decompression procedure after performing integrity verification. I can. However, when the header decompression procedure is performed, since an IR packet including information on which the data is compressed has not been received, a header decompression failure occurs, resulting in data loss or an error in data.

In the present invention, methods for solving the problem of the first embodiment in which a header decompression failure problem may occur with respect to downlink data during handover are proposed as follows. It may be transmitted by applying one or more of the following methods.

-Method 1: When the target base station discards data according to the PDCP status report received from the terminal during handover, if the data including the generated IR packet after processing the data in advance should be discarded, after discarding the data , The transmission is performed by newly generating or configuring and including an IR packet in a plurality of data to be transmitted to the terminal for the first time. Accordingly, since the terminal can receive the IR packet, it can normally perform a header decompression procedure for data received later.

-Method 2: When performing a handover, the UE and the base station do not perform a header compression procedure on the transmitted data during handover or until the handover is completed, if a header compression procedure is set. Instead, it may be characterized in that the IR packet is continuously included and transmitted. If the header compression procedure is not applied and the IR packet is continuously transmitted as described above, the receiving PDCP layer device stores and synchronizes the ROHC context, and does not perform the header decompression procedure on the received data. No failure problem occurs. When transmitting an IR packet in the handover procedure, it may be transmitted by applying one of the following methods.

■ Method 2-1: In the above, the target base station continues to transmit data until a handover completion message is received from the terminal or until a PDCP status report is received, or until a predetermined timer expires or for a predetermined time. It can be transmitted including the IR packet without applying the header compression procedure to the. And after that, a header compression procedure can be applied to transmitted data.

■ Method 2-2: In the above, the target base station can transmit the data received from the source base station including the IR packet without applying the header compression procedure. In addition, new downlink data received from the core network may be transmitted by applying a header compression procedure.

■ Method 2-3: In the above, the target base station may transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, downlink data that performs new transmission or is initially transmitted may be transmitted by applying a header compression procedure.

■ Method 2-4: In the above, the target base station may transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, for downlink data that performs new transmission or is transmitted for the first time, the first plurality of data may be transmitted including an IR packet, and data transmitted thereafter may be transmitted by applying a header compression procedure.

Method 3: In the handover procedure, when the target base station transmits the IR packet, the target base station does not include the IR packet in downlink data (for example, PDCP data PDU) and does not transmit the downlink PDCP control data (for example, PDCP control The IR packet may be included and transmitted in a PDU (for example, a new PDCP control PDU or interspersed ROHC feedback). Since the downlink PDCP control data is not assigned a COUNT value or a PDCP serial number, and is not discarded by a PDCP status report, the base station can always transmit PDCP control data including IR packets processed in advance, and multiple transmissions Or you can send it first. Accordingly, when the UE receives the PDCP control data including the IR packet, it can receive, store and synchronize the ROHC context, and can normally apply a header decompression procedure for downlink data.

The problem of the first embodiment in which a header decompression failure problem may occur for downlink data during handover in the present invention may also occur for uplink data during handover. Accordingly, in the following of the present invention, methods for solving the problem of the first embodiment that occur with respect to uplink data are proposed as follows. It may be transmitted by applying one or more of the following methods.

-Method 1: When the terminal discards data according to the PDCP status report received from the source base station or the target base station during handover, if the data including the IR packet generated by processing the data in advance must be discarded, the data is discarded. After discarding, an IR packet is newly generated or configured to be included in a plurality of data to be transmitted to the target base station for the first time to perform transmission. Accordingly, since the terminal can receive the IR packet, it can normally perform a header decompression procedure for data received later.

-Method 2: When performing a handover, the UE and the base station do not perform a header compression procedure on the transmitted data during handover or until the handover is completed, if a header compression procedure is set. Instead, it may be characterized in that the IR packet is continuously included and transmitted. If the header compression procedure is not applied and the IR packet is continuously transmitted as described above, the receiving PDCP layer device stores and synchronizes the ROHC context, and does not perform the header decompression procedure on the received data. No failure problem occurs. When transmitting an IR packet in the handover procedure, it may be transmitted by applying one of the following methods.

■ Method 2-1: In the above, the UE receives the handover command message and transmits the handover completion message, or until the first uplink transmission resource is allocated from the target base station or until the PDCP status report is received or a predetermined It is possible to transmit including an IR packet without applying a header compression procedure to data to be continuously transmitted for a predetermined time or until the timer expires. And after that, a header compression procedure can be applied to transmitted data.

■ Method 2-2: In the above, the UE can transmit data transmitted to the source base station including the IR packet without applying the header compression procedure. In addition, new uplink data may be transmitted by applying a header compression procedure.

■ Method 2-3: In the above, the UE can transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, uplink data that performs new transmission or is initially transmitted may be transmitted by applying a header compression procedure.

■ Method 2-4: In the above, the UE can transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, for uplink data that performs new transmission or is transmitted for the first time, the first plurality of data may be transmitted including an IR packet, and data to be transmitted after that may be transmitted by applying a header compression procedure.

Method 3: In the handover procedure, when transmitting an IR packet, the UE does not include the IR packet in uplink data (eg PDCP data PDU) and does not transmit uplink PDCP control data (eg PDCP control PDU). The IR packet may be included and transmitted in (eg, a new PDCP control PDU or interspersed ROHC feedback). Since the uplink PDCP control data is not assigned a COUNT value or a PDCP serial number, and is not discarded by a PDCP status report, the UE can always transmit PDCP control data including IR packets processed in advance, and multiple transmissions Or you can send it first. Accordingly, when the target base station receives the PDCP control data including the IR packet, the ROHC context can be received, stored, and synchronized, and the header decompression procedure can be normally applied to the uplink data.

2I is a diagram illustrating a second embodiment in which a header decompression failure problem may occur for downlink data during handover in the present invention.

In FIG. 2i, when the terminal 2i-03 receives a handover command message from the source base station 2i-01, it performs the handover method indicated in the handover command message and performs a handover procedure to the target base station 2i-02. Perform.

In the above, an embodiment of a specific procedure for transmitting and receiving data in a handover procedure between a base station and a terminal in the second embodiment of the present invention is as follows.

-Step 1: The source base station transmits data (for example, PDCP PDU or PDCP SDU) having a PDCP serial number or COUNT value of 100 to 110 to the terminal through the downlink. However, it is not possible to receive a confirmation that data corresponding to Nos. 100 to 110 has been successfully delivered to the UE (eg, RLC ACK of an RLC Status report). In addition, the source base station instructs the handover by transmitting a handover command message (eg, RRCReconfiguration message) to the terminal.

-Step 2: In the first step, the source base station transfers all data to the target base station in ascending order from data that has not received confirmation of successful delivery or data having the lowest PDCP serial number or COUNT value that has not received confirmation of successful delivery And transmits or retransmits to the terminal. In step 1, the UE has successfully received data corresponding to the PDCP serial number or COUNT value from 100 to 106, but fails to transmit a feedback (RLC ACK) indicating that the data has been successfully received to the source base station. .

-Step 3: The target base station performs data processing in the PDCP layer device on the data (e.g., PDCP SDU) received from the source base station, and, for example, the transmitting PDCP layer device of the target base station targets the data. Header compression may be performed based on the ROHC context of the base station, integrity protection or encryption procedure may be performed based on the security key of the target base station, and data may be delivered to a lower layer. In the above, in order to initialize or synchronize the header compression context, the target base station may perform data processing by configuring an IR packet in data corresponding to a PDCP serial number or COUNT value from 100 to 104. More specifically, in the above, the header compression protocol is in U mode (U-mode, a mode in which the receiving end does not request feedback (ACK or NACK) in unidirectional mode) or R mode (the receiving end receives ACK or NACK in R-mode, Reliable mode). Sending mode) or O mode (a mode in which the receiver sends NACK in O-mode, Optimistic mode), or when operating in an IR state (IR state) can generate and transmit IR packets. In addition, data from #105 to #130 may be compressed based on the header compression context, integrity protected or encrypted, and transmitted to a lower layer or prepared for transmission. In the above, the IR (Initialization and Refresh) packet may be included in data and transmitted, and the transmitting PDCP layer device includes compression setting information for compression or decompression to the receiving PDCP layer device. Therefore, if the IR packet is not successfully delivered to the receiving PDCP layer device, a header decompression error may occur for the received data.

-Step 4: After receiving the handover command message from the source base station, the terminal completes the handover procedure to the target base station according to the handover method or handover configuration information indicated in the handover command message, and then to the target base station. A handover completion message (for example, an RRCReconfigurationComplete message) may be transmitted, and data corresponding to numbers 100 to 130 of the PDCP serial number or COUNT value may be received from the target base station. However, in step 2, since the terminal has already successfully received the data corresponding to the PDCP serial number or COUNT value 100 to 106, the data corresponding to the PDCP serial number or COUNT value 100 to 106 received in step 4 above. Is determined as redundantly received data and immediately discarded. Accordingly, the IR packets included in the data from the PDCP serial number or COUNT value from 100 to 104 are discarded and lost, resulting in a header decompression error from data 105.

In the present invention, methods for solving the problem of the second embodiment in which a header decompression failure problem may occur for downlink data during handover are proposed as follows. It may be transmitted by applying one or more of the following methods.

-Method 1: During handover, the terminal, the source base station, or the target base station always configures and transmits a PDCP status report before transmitting or receiving data. That is, in the second embodiment, if the target base station receives the PDCP status report from the terminal, it is possible to know that the terminal has already successfully received the data corresponding to the PDCP serial number or COUNT value 100 to 106. It can be prevented from being discarded by the duplicate detection procedure of this terminal. As another method, the target base station may be characterized in that it receives the PDCP status report from the terminal and then checks the generated data or generates data and transmits the data, and until the PDCP status report is received, the data generation or data You can also delay transmission. As another method, the retransmitted data may be characterized by retransmitting the data by checking the generated data after receiving the PDCP status report from the terminal or by generating the data. It may be characterized in that it may be characterized in that it may be characterized in that it may delay the generation or transmission of retransmitted data until the PDCP status report is received.

-Method 2: When performing a handover, the UE and the base station do not perform a header compression procedure on the transmitted data during handover or until the handover is completed, if a header compression procedure is set. Instead, it may be characterized in that the IR packet is continuously included and transmitted. If the header compression procedure is not applied and the IR packet is continuously transmitted as described above, the receiving PDCP layer device stores and synchronizes the ROHC context, and does not perform the header decompression procedure on the received data. No failure problem occurs. When transmitting an IR packet in the handover procedure, it may be transmitted by applying one of the following methods.

■ Method 2-1: In the above, the target base station continues to transmit data until a handover completion message is received from the terminal or until a PDCP status report is received, or until a predetermined timer expires or for a predetermined time. It can be transmitted including the IR packet without applying the header compression procedure to the. And after that, a header compression procedure can be applied to transmitted data.

■ Method 2-2: In the above, the target base station can transmit the data received from the source base station including the IR packet without applying the header compression procedure. In addition, new downlink data received from the core network may be transmitted by applying a header compression procedure.

■ Method 2-3: In the above, the target base station may transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, downlink data that performs new transmission or is initially transmitted may be transmitted by applying a header compression procedure.

■ Method 2-4: In the above, the target base station may transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, for downlink data that performs new transmission or is transmitted for the first time, the first plurality of data may be transmitted including an IR packet, and data transmitted thereafter may be transmitted by applying a header compression procedure.

Method 3: In the handover procedure, when the target base station transmits the IR packet, the target base station does not include the IR packet in downlink data (for example, PDCP data PDU) and does not transmit the downlink PDCP control data (for example, PDCP control The IR packet may be included and transmitted in a PDU (for example, a new PDCP control PDU or interspersed ROHC feedback). Since the downlink PDCP control data is not assigned a COUNT value or a PDCP serial number, and is not discarded by a PDCP status report, the base station can always transmit PDCP control data including IR packets processed in advance, and multiple transmissions Or you can send it first. Accordingly, when the UE receives the PDCP control data including the IR packet, it can receive, store and synchronize the ROHC context, and can normally apply a header decompression procedure for downlink data.

-Method 4: In the handover procedure, the receiving PDCP layer device performs a procedure to check whether the received data is data in the window (for example, only data in the window is determined as valid data) or a duplicate detection procedure, and data outside the window A decoding procedure may be performed, a header decompression procedure may be performed, and a procedure of extracting if an IR packet is included in the redundant data may be performed before discarding the data or redundant data. That is, if it is determined that data outside the header window or redundant data is determined in the procedure for checking whether the data is in the window or the duplicate detection procedure, the decoding procedure is performed before the data outside the window or the redundant data is discarded, and the header decompression procedure is performed. It checks whether the IR packet is included, stores the ROHC context information of the IR packet, if the IR packet is included, updates the ROHC context information of the receiving PDCP layer device, and then performs a header decompression procedure of the received data. By applying, the header compression decompression procedure can be performed. In the header decompression procedure, the procedure of checking whether an IR packet is included in the received data, storing ROHC context information of the IR packet if the IR packet is included, and updating ROHC context information of the receiving PDCP layer device are performed. Can include. When processing data outside the window or redundant data in the procedure for checking whether the data is within the window or the duplicate detection procedure proposed above, it may be transmitted by applying one of the following methods. In the following, the RCVD_COUNT value means the COUNT value corresponding to the received data, and RX_DELIV indicates the lower end of the window that meets the validity of the data in the receiving PDCP layer device, or the first (or still rearrangement) that has not been delivered to the upper layer. Indicates the COUNT value of the data (which has the lowest COUNT value waiting).

■ Method 4-1: In the method 4-1, before discarding data outside the window or redundant data, a decoding procedure is performed and a header compression decompression procedure is applied.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before (if the received data is duplicate data)

● 2> If the decoding procedure for the received PDCP Data PDU (the data part of the PDCP PDU) has not been performed, the decoding procedure is performed, and the header decompression procedure is performed (for example, if the IR packet is checked and there is no IR packet) ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-2: In the method 4-2, before discarding data outside the window or redundant data, a decoding procedure is performed and a header decompression procedure is applied. In addition, in the above method 4-2, in order to enhance security, if the COUNT value corresponding to the currently received data has been previously received, and the data corresponding to the COUNT value has been successfully received (if integrity protection And if the verification procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred, and the received data is discarded to perform the duplicate detection procedure. It can be improved to prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and the integrity protection and verification procedure has been set, the integrity verification procedure for the PDCP PDU corresponding to the RCVD_COUNT value has previously been successfully performed. If ever

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been set.

● 2> If the decoding procedure for the received PDCP Data PDU (the data part of the PDCP PDU) has not been performed, the decoding procedure is performed, and the header decompression procedure is performed (for example, if the IR packet is checked and there is no IR packet) ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-3: In Method 4-3, data outside the window or redundant data only in the handover procedure, only when the header compression protocol is initialized, or when the header compression protocol is in the U mode NC (No context) state. It may be characterized in that a decoding procedure is performed and a header compression decompression procedure is applied before being discarded. The operation may be performed in a U mode (Unidirectional mode), O mode (Bidirectional Optimistic Mode) or R mode (Bidirectional Reliable Mode) in NC state (No Context) or SC state (Static Context). That is, even if an expired or duplicated packet is not immediately discarded, it is decoded, integrity verification is performed, and header decompression is performed. Therefore, even if an IR packet is carried in the duplicated packet, the PDCP layer device at the receiving end may receive it, check all header information and ROHC protocol configuration information, and complete synchronization with the transmitting end ROHC protocol. Accordingly, header-compressed PDCP PDUs transmitted from the transmitting end can be successfully decompressed.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before (if the received data is duplicate data)

● 2> If the header decompression protocol (ROHC) is in the NC state of U mode (or the header compression protocol has been reset and has not been reset)

■ 3> If the decoding procedure is not performed for the received PDCP Data PDU (the data part of the PDCP PDU), the decoding procedure is performed, and the header decompression procedure is performed (e.g., check the IR packet and if there is no IR packet). ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-4: In Method 4-4, data outside the window or redundant data only in the handover procedure, only when the header compression protocol is initialized, or when the header compression protocol is in the U mode NC (No context) state. It may be characterized in that a decoding procedure is performed and a header compression decompression procedure is applied before being discarded. The operation may be performed in a U mode (Unidirectional mode), O mode (Bidirectional Optimistic Mode) or R mode (Bidirectional Reliable Mode) in NC state (No Context) or SC state (Static Context). That is, even if an expired or duplicated packet is not immediately discarded, it is decoded, integrity verification is performed, and header decompression is performed. Therefore, even if an IR packet is carried in the duplicated packet, the PDCP layer device at the receiving end may receive it, check all header information and ROHC protocol configuration information, and complete synchronization with the transmitting end ROHC protocol. Accordingly, header-compressed PDCP PDUs transmitted from the transmitting end can be successfully decompressed. In addition, in order to enhance security, the method 4-4 above has previously received the COUNT value corresponding to the currently received data, and if the data corresponding to the COUNT value has been successfully received (if integrity protection And if the verification procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred, and the received data is discarded to perform the duplicate detection procedure. It can be improved to prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and the integrity protection and verification procedure has been set, the integrity verification procedure for the PDCP PDU corresponding to the RCVD_COUNT value has previously been successfully performed. If ever

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been set.

● 2> If the header decompression protocol (ROHC) is in the NC state of U mode (or the header compression protocol has been reset and has not been reset)

■ 3> If the decoding procedure is not performed for the received PDCP Data PDU (the data part of the PDCP PDU), the decoding procedure is performed, and the header decompression procedure is performed (e.g., check the IR packet and if there is no IR packet). ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 5: For Method 1, Method 2, Method 3, and Method 4, a downlink source data-based data redundancy transmission method (PDCP SDU based duplication) in a handover command message (or RRC message) or an efficient hand in the first embodiment Apply the proposed duplicate detection procedure applicable when the over method is set or not set, and apply the header decompression procedure by applying the above methods to the data determined to be duplicate data (or data outside the window) Then, the redundant data (or data outside the window) can be discarded.

FIG. 2J is a diagram illustrating another second embodiment in which a header decompression failure problem may occur for uplink data during handover in the present invention.

In the present invention, the problem of the second embodiment in which header decompression failure may occur for downlink data during handover may occur in the same manner as in FIG. 2J for uplink data during handover. Accordingly, in the following of the present invention, methods for solving the problem of the second embodiment that occur with respect to uplink data are proposed as follows. It may be transmitted by applying one or more of the following methods.

-Method 1: During handover, the terminal, the source base station, or the target base station always configures and transmits a PDCP status report before transmitting or receiving data. That is, in the uplink case of the second embodiment, if the terminal receives the PDCP status report from the target base station, it can be seen that the terminal has already successfully received data corresponding to the PDCP serial number or COUNT value 100 to 106. Therefore, it is possible to prevent the IR packet from being discarded by the duplicate detection procedure of the target base station. As another method, the terminal may be characterized in that the terminal receives the PDCP status report from the target base station and then checks the generated data or generates data and transmits the data, and until the PDCP status report is received, the data generation or data You can also delay transmission. As another method, the retransmitted data may be characterized by retransmitting the data by checking the generated data after receiving the PDCP status report from the target base station or by generating the data. It may be characterized in that it may be characterized in that it may be characterized in that it may delay the generation or transmission of retransmitted data until the PDCP status report is received.

-Method 2: When performing a handover, the UE and the base station do not perform a header compression procedure on the transmitted data during handover or until the handover is completed, if a header compression procedure is set. Instead, it may be characterized in that the IR packet is continuously included and transmitted. If the header compression procedure is not applied and the IR packet is continuously transmitted as described above, the receiving PDCP layer device stores and synchronizes the ROHC context, and does not perform the header decompression procedure on the received data. No failure problem occurs. When transmitting an IR packet in the handover procedure, it may be transmitted by applying one or more of the following methods.

■ Method 2-1: In the above, the target base station continues to transmit data until a handover completion message is received from the terminal or until a PDCP status report is received, or until a predetermined timer expires or for a predetermined time. It can be transmitted including the IR packet without applying the header compression procedure to the. And after that, a header compression procedure can be applied to transmitted data.

■ Method 2-2: In the above, the target base station may transmit data received from the source base station including the IR packet without applying a header compression procedure. In addition, new downlink data received from the core network may be transmitted by applying a header compression procedure.

■ Method 2-3: In the above, the target base station can transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, downlink data that performs new transmission or is initially transmitted may be transmitted by applying a header compression procedure.

■ Method 2-4: In the above, the target base station can transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, for downlink data that performs new transmission or is transmitted for the first time, the first plurality of data may be transmitted including an IR packet, and data transmitted thereafter may be transmitted by applying a header compression procedure.

Method 3: In the handover procedure, when transmitting an IR packet, the UE does not include the IR packet in uplink data (eg PDCP data PDU) and does not transmit uplink PDCP control data (eg PDCP control PDU). The IR packet may be included and transmitted in (eg, a new PDCP control PDU or interspersed ROHC feedback). Since the uplink PDCP control data is not assigned a COUNT value or a PDCP serial number, and is not discarded by a PDCP status report, the UE can always transmit PDCP control data including IR packets processed in advance, and multiple transmissions Or you can send it first. Accordingly, when the target base station receives the PDCP control data including the IR packet, the ROHC context can be received, stored, and synchronized, and the header decompression procedure can be normally applied to downlink data.

-Method 4: In the handover procedure, the receiving PDCP layer device performs a procedure to check whether the received data is data in the window (for example, only data in the window is determined as valid data) or a duplicate detection procedure, and data outside the window A decoding procedure may be performed, a header decompression procedure may be performed, and a procedure of extracting if an IR packet is included in the redundant data may be performed before discarding the data or redundant data. That is, if it is determined that data outside the header window or redundant data is determined in the procedure for checking whether the data is in the window or the duplicate detection procedure, the decoding procedure is performed before the data outside the window or the redundant data is discarded, and the header decompression procedure is performed. It checks whether the IR packet is included, stores the ROHC context information of the IR packet, if the IR packet is included, updates the ROHC context information of the receiving PDCP layer device, and then performs a header decompression procedure of the received data. By applying, the header compression decompression procedure can be performed. In the header decompression procedure, the procedure of checking whether an IR packet is included in the received data, storing ROHC context information of the IR packet if the IR packet is included, and updating ROHC context information of the receiving PDCP layer device are performed. Can include. When processing data outside the window or redundant data in the procedure for checking whether the data is within the window or the duplicate detection procedure proposed above, it may be transmitted by applying one of the following methods. In the following, the RCVD_COUNT value means the COUNT value corresponding to the received data, and RX_DELIV indicates the lower end of the window that meets the validity of the data in the receiving PDCP layer device, or the first (or still rearrangement) that has not been delivered to the upper layer. Indicates the COUNT value of the data (which has the lowest COUNT value waiting).

■ Method 4-1: In the method 4-1, before discarding data outside the window or redundant data, a decoding procedure is performed and a header compression decompression procedure is applied.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before (if the received data is duplicate data)

● 2> If the decoding procedure for the received PDCP Data PDU (the data part of the PDCP PDU) has not been performed, the decoding procedure is performed, and the header decompression procedure is performed (for example, if the IR packet is checked and there is no IR packet) ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-2: In the method 4-2, before discarding data outside the window or redundant data, a decoding procedure is performed and a header decompression procedure is applied. In addition, in the above method 4-2, in order to enhance security, if the COUNT value corresponding to the currently received data has been previously received, and the data corresponding to the COUNT value has been successfully received (if integrity protection And if the verification procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred, and the received data is discarded to perform the duplicate detection procedure. It can be improved to prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and the integrity protection and verification procedure has been set, the integrity verification procedure for the PDCP PDU corresponding to the RCVD_COUNT value has previously been successfully performed. If ever

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been set.

● 2> If the decoding procedure for the received PDCP Data PDU (the data part of the PDCP PDU) has not been performed, the decoding procedure is performed, and the header decompression procedure is performed (for example, if the IR packet is checked and there is no IR packet) ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-3: In Method 4-3, data outside the window or redundant data only in the handover procedure, only when the header compression protocol is initialized, or when the header compression protocol is in the U mode NC (No context) state. It may be characterized in that a decoding procedure is performed and a header compression decompression procedure is applied before being discarded. The operation may be performed in a U mode (Unidirectional mode), O mode (Bidirectional Optimistic Mode) or R mode (Bidirectional Reliable Mode) in NC state (No Context) or SC state (Static Context). That is, even if an expired or duplicated packet is not immediately discarded, it is decoded, integrity verification is performed, and header decompression is performed. Therefore, even if an IR packet is carried in the duplicated packet, the PDCP layer device at the receiving end may receive it, check all header information and ROHC protocol configuration information, and complete synchronization with the transmitting end ROHC protocol. Accordingly, header-compressed PDCP PDUs transmitted from the transmitting end can be successfully decompressed.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before (if the received data is duplicate data)

● 2> If the header decompression protocol (ROHC) is in the NC state of U mode (or the header compression protocol has been reset and has not been reset)

■ 3> If the decoding procedure is not performed for the received PDCP Data PDU (the data part of the PDCP PDU), the decoding procedure is performed, and the header decompression procedure is performed (e.g., check the IR packet and if there is no IR packet). ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-4: In Method 4-4, data outside the window or redundant data only in the handover procedure, only when the header compression protocol is initialized, or when the header compression protocol is in the U mode NC (No context) state. It may be characterized in that a decoding procedure is performed and a header compression decompression procedure is applied before being discarded. The operation may be performed in a U mode (Unidirectional mode), O mode (Bidirectional Optimistic Mode) or R mode (Bidirectional Reliable Mode) in NC state (No Context) or SC state (Static Context). That is, even if an expired or duplicated packet is not immediately discarded, it is decoded, integrity verification is performed, and header decompression is performed. Therefore, even if an IR packet is carried in the duplicated packet, the PDCP layer device at the receiving end may receive it, check all header information and ROHC protocol configuration information, and complete synchronization with the transmitting end ROHC protocol. Accordingly, header-compressed PDCP PDUs transmitted from the transmitting end can be successfully decompressed. In addition, in order to enhance security, the method 4-4 above has previously received the COUNT value corresponding to the currently received data, and if the data corresponding to the COUNT value has been successfully received (if integrity protection And if the verification procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred, and the received data is discarded to perform the duplicate detection procedure. It can be improved to prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and the integrity protection and verification procedure has been set, the integrity verification procedure for the PDCP PDU corresponding to the RCVD_COUNT value has previously been successfully performed. If ever

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been set.

● 2> If the header decompression protocol (ROHC) is in the NC state of U mode (or the header compression protocol has been reset and has not been reset)

■ 3> If the decoding procedure is not performed for the received PDCP Data PDU (the data part of the PDCP PDU), the decoding procedure is performed, and the header decompression procedure is performed (e.g., check the IR packet and if there is no IR packet). ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 5: For Method 1, Method 2, Method 3, and Method 4, a downlink source data-based data redundancy transmission method (PDCP SDU based duplication) in a handover command message (or RRC message) or an efficient hand in the first embodiment Apply the proposed duplicate detection procedure applicable when the over method is set or not set, and apply the header decompression procedure by applying the above methods to the data determined to be duplicate data (or data outside the window) Then, the redundant data (or data outside the window) can be discarded.

2K is a diagram illustrating a third embodiment in which a header decompression failure problem may occur for downlink data during handover in the present invention.

In FIG. 2K, when the terminal 2k-03 receives a handover command message from the source base station 2k-01, it performs the handover method indicated in the handover command message and performs a handover procedure to the target base station 2k-02. Perform.

In the above, in the third embodiment of the present invention, an embodiment of a specific procedure in which the base station and the terminal transmit and receive data in the handover procedure is as follows.

-Step 1: The source base station transmits data (for example, PDCP PDU or PDCP SDU) having a PDCP serial number or COUNT value of 100 to 110 to the terminal through the downlink. However, it is not possible to receive a confirmation that data corresponding to Nos. 100 to 110 has been successfully delivered to the UE (eg, RLC ACK of an RLC Status report). In addition, the source base station instructs the handover by transmitting a handover command message (eg, RRCReconfiguration message) to the terminal.

-Step 2: In the first step, the source base station transfers all data to the target base station in ascending order from data that has not received confirmation of successful delivery or data having the lowest PDCP serial number or COUNT value that has not received confirmation of successful delivery And transmits or retransmits to the terminal. In step 1, the UE has successfully received data corresponding to the PDCP serial number or COUNT value from 100 to 106, but fails to transmit a feedback (RLC ACK) indicating that the data has been successfully received to the source base station. .

-Step 3: The target base station performs data processing in the PDCP layer device on the data (e.g., PDCP SDU) received from the source base station, and, for example, the transmitting PDCP layer device of the target base station targets the data. Header compression may be performed based on the ROHC context of the base station, integrity protection or encryption procedure may be performed based on the security key of the target base station, and data may be delivered to a lower layer. In the above, in order to initialize or synchronize the header compression context, the target base station may perform data processing by configuring an IR packet in data corresponding to a PDCP serial number or COUNT value from 100 to 104. More specifically, in the above, the header compression protocol is in U mode (U-mode, a mode in which the receiving end does not request feedback (ACK or NACK) in unidirectional mode) or R mode (the receiving end receives ACK or NACK in R-mode, Reliable mode). Sending mode) or O mode (a mode in which the receiver sends NACK in O-mode, Optimistic mode), or when operating in an IR state (IR state) can generate and transmit IR packets. In addition, data from #105 to #130 may be compressed based on the header compression context, integrity protected or encrypted, and transmitted to a lower layer or prepared for transmission. In addition, data corresponding to a PDCP serial number or a COUNT value of 100 to 110 may be transmitted to the terminal. In the above, the IR (Initialization and Refresh) packet may be included in data and transmitted, and the transmitting PDCP layer device includes compression setting information for compression or decompression to the receiving PDCP layer device. Therefore, if the IR packet is not successfully delivered to the receiving PDCP layer device, a header decompression error may occur for the received data.

-Step 4: After receiving the handover command message from the source base station, the terminal completes the handover procedure to the target base station according to the handover method or handover configuration information indicated in the handover command message, and then to the target base station. A handover completion message (for example, an RRCReconfigurationComplete message) may be transmitted, and data corresponding to 107 to 108 of the PDCP serial number or COUNT value may be received from the target base station. And if the receiving RLC layer device is set to the out-of-order transmission function or when the out-of-order transmission function is performed, when the RLC layer device receives the data, even though the data from 100 to 106 has not yet been received, the 107 and 108 It is possible to transfer the data of 1 to the upper layer device, the PDCP layer device. In addition, since the terminal has already successfully received the data corresponding to the PDCP serial number or COUNT value from 100 to 106 in step 2, the data corresponding to the PDCP serial number or COUNT value from 107 to 108 that is received in step 4. It is possible to determine as the ordered data or data in order after number 106, perform a decoding procedure immediately, and apply a header decompression procedure. However, since IR packets included in the PDCP serial number or COUNT value from 100 to 104 have not yet been received, a header decompression error occurs from data 106.

In the present invention, methods for solving the problem of the third embodiment in which a header decompression failure problem may occur with respect to downlink data during handover are proposed as follows. It may be transmitted by applying one or more of the following methods.

-Method 1: During handover, the terminal, the source base station, or the target base station always configures and transmits a PDCP status report before transmitting or receiving data. That is, in the third embodiment, if the target base station receives the PDCP status report from the terminal, it is possible to know that the terminal has already successfully received the data corresponding to the PDCP serial number or COUNT value from 100 to 106. Can be transmitted by including after data 107. As another method, the target base station may be characterized in that it receives the PDCP status report from the terminal and then checks the generated data or generates data and transmits the data, and until the PDCP status report is received, the data generation or data You can also delay transmission. As another method, the retransmitted data may be characterized by retransmitting the data by checking the generated data after receiving the PDCP status report from the terminal or by generating the data. It may be characterized in that it may be characterized in that it may be characterized in that it may delay the generation or transmission of retransmitted data until the PDCP status report is received.

-Method 2: When performing a handover, the UE and the base station do not perform a header compression procedure on the transmitted data during handover or until the handover is completed, if a header compression procedure is set. Instead, it may be characterized in that the IR packet is continuously included and transmitted. If the header compression procedure is not applied and the IR packet is continuously transmitted as described above, the receiving PDCP layer device stores and synchronizes the ROHC context, and does not perform the header decompression procedure on the received data. No failure problem occurs. When transmitting an IR packet in the handover procedure, it may be transmitted by applying one of the following methods.

■ Method 2-1: In the above, the target base station continues to transmit data until a handover completion message is received from the terminal or until a PDCP status report is received, or until a predetermined timer expires or for a predetermined time. It can be transmitted including the IR packet without applying the header compression procedure to the. And after that, a header compression procedure can be applied to transmitted data.

■ Method 2-2: In the above, the target base station may transmit data received from the source base station including the IR packet without applying a header compression procedure. In addition, new downlink data received from the core network may be transmitted by applying a header compression procedure.

■ Method 2-3: In the above, the target base station can transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, downlink data that performs new transmission or is initially transmitted may be transmitted by applying a header compression procedure.

■ Method 2-4: In the above, the target base station can transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, for downlink data that performs new transmission or is transmitted for the first time, the first plurality of data may be transmitted including an IR packet, and data transmitted thereafter may be transmitted by applying a header compression procedure.

Method 3: In the handover procedure, when the target base station transmits the IR packet, the target base station does not include the IR packet in downlink data (for example, PDCP data PDU) and does not transmit the downlink PDCP control data (for example, PDCP control The IR packet may be included and transmitted in a PDU (for example, a new PDCP control PDU or interspersed ROHC feedback). Since the downlink PDCP control data is not assigned a COUNT value or a PDCP serial number, and is not discarded by a PDCP status report, the base station can always transmit PDCP control data including IR packets processed in advance, and multiple transmissions Or you can send it first. Accordingly, when the UE receives the PDCP control data including the IR packet, it can receive, store and synchronize the ROHC context, and can normally apply a header decompression procedure for downlink data.

-Method 4: In the handover procedure, the receiving PDCP layer device performs a procedure to check whether the received data is data in the window (for example, only data in the window is determined as valid data) or a duplicate detection procedure, and data outside the window A decoding procedure may be performed, a header decompression procedure may be performed, and a procedure of extracting if an IR packet is included in the redundant data may be performed before discarding the data or redundant data. That is, if it is determined that data outside the header window or redundant data is determined in the procedure for checking whether the data is in the window or the duplicate detection procedure, the decoding procedure is performed before the data outside the window or the redundant data is discarded, and the header decompression procedure is performed. It checks whether the IR packet is included, stores the ROHC context information of the IR packet, if the IR packet is included, updates the ROHC context information of the receiving PDCP layer device, and then performs a header decompression procedure of the received data. By applying, the header compression decompression procedure can be performed. In the header decompression procedure, the procedure of checking whether an IR packet is included in the received data, storing ROHC context information of the IR packet if the IR packet is included, and updating ROHC context information of the receiving PDCP layer device are performed. Can include. When processing data outside the window or redundant data in the procedure for checking whether the data is within the window or the duplicate detection procedure proposed above, it may be transmitted by applying one of the following methods. In the following, the RCVD_COUNT value means the COUNT value corresponding to the received data, and RX_DELIV indicates the lower end of the window that meets the validity of the data in the receiving PDCP layer device, or the first (or still rearrangement) that has not been delivered to the upper layer. Indicates the COUNT value of the data (which has the lowest COUNT value waiting).

■ Method 4-1: In the method 4-1, before discarding data outside the window or redundant data, a decoding procedure is performed and a header compression decompression procedure is applied.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before (if the received data is duplicate data)

● 2> If the decoding procedure for the received PDCP Data PDU (the data part of the PDCP PDU) has not been performed, the decoding procedure is performed, and the header decompression procedure is performed (for example, if the IR packet is checked and there is no IR packet) ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-2: In the method 4-2, before discarding data outside the window or redundant data, a decoding procedure is performed and a header decompression procedure is applied. In addition, in the above method 4-2, in order to enhance security, if the COUNT value corresponding to the currently received data has been previously received, and the data corresponding to the COUNT value has been successfully received (if integrity protection And if the verification procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred, and the received data is discarded to perform the duplicate detection procedure. It can be improved to prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and the integrity protection and verification procedure has been set, the integrity verification procedure for the PDCP PDU corresponding to the RCVD_COUNT value has previously been successfully performed. If ever

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been set.

● 2> If the decoding procedure for the received PDCP Data PDU (the data part of the PDCP PDU) has not been performed, the decoding procedure is performed, and the header decompression procedure is performed (for example, if the IR packet is checked and there is no IR packet) ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-3: In Method 4-3, data outside the window or redundant data only in the handover procedure, only when the header compression protocol is initialized, or when the header compression protocol is in the U mode NC (No context) state. It may be characterized in that a decoding procedure is performed and a header compression decompression procedure is applied before being discarded. The operation may be performed in a U mode (Unidirectional mode), O mode (Bidirectional Optimistic Mode) or R mode (Bidirectional Reliable Mode) in NC state (No Context) or SC state (Static Context). That is, even if an expired or duplicated packet is not immediately discarded, it is decoded, integrity verification is performed, and header decompression is performed. Therefore, even if an IR packet is carried in the duplicated packet, the PDCP layer device at the receiving end may receive it, check all header information and ROHC protocol configuration information, and complete synchronization with the transmitting end ROHC protocol. Accordingly, header-compressed PDCP PDUs transmitted from the transmitting end can be successfully decompressed.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before (if the received data is duplicate data)

● 2> If the header decompression protocol (ROHC) is in the NC state of U mode (or the header compression protocol has been reset and has not been reset)

■ 3> If the decoding procedure is not performed for the received PDCP Data PDU (the data part of the PDCP PDU), the decoding procedure is performed, and the header decompression procedure is performed (e.g., check the IR packet and if there is no IR packet). ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-4: In Method 4-4, data outside the window or redundant data only in the handover procedure, only when the header compression protocol is initialized, or when the header compression protocol is in the U mode NC (No context) state. It may be characterized in that a decoding procedure is performed and a header compression decompression procedure is applied before being discarded. The operation may be performed in a U mode (Unidirectional mode), O mode (Bidirectional Optimistic Mode) or R mode (Bidirectional Reliable Mode) in NC state (No Context) or SC state (Static Context). That is, even if an expired or duplicated packet is not immediately discarded, it is decoded, integrity verification is performed, and header decompression is performed. Therefore, even if an IR packet is carried in the duplicated packet, the PDCP layer device at the receiving end may receive it, check all header information and ROHC protocol configuration information, and complete synchronization with the transmitting end ROHC protocol. Accordingly, header-compressed PDCP PDUs transmitted from the transmitting end can be successfully decompressed. In addition, in order to enhance security, the method 4-4 above has previously received the COUNT value corresponding to the currently received data, and if the data corresponding to the COUNT value has been successfully received (if integrity protection And if the verification procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred, and the received data is discarded to perform the duplicate detection procedure. It can be improved to prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and the integrity protection and verification procedure has been set, the integrity verification procedure for the PDCP PDU corresponding to the RCVD_COUNT value has previously been successfully performed. If ever

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been set.

● 2> If the header decompression protocol (ROHC) is in the NC state of U mode (or the header compression protocol has been reset and has not been reset)

■ 3> If the decoding procedure is not performed for the received PDCP Data PDU (the data part of the PDCP PDU), the decoding procedure is performed, and the header decompression procedure is performed (e.g., check the IR packet and if there is no IR packet). ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 5: For Method 1, Method 2, Method 3, and Method 4, a downlink source data-based data redundancy transmission method (PDCP SDU based duplication) in a handover command message (or RRC message) or an efficient hand in the first embodiment Apply the proposed duplicate detection procedure applicable when the over method is set or not set, and apply the header decompression procedure by applying the above methods to the data determined to be duplicate data (or data outside the window) Then, the redundant data (or data outside the window) can be discarded.

2L is a diagram showing another third embodiment in which a header decompression failure problem may occur for uplink data during handover in the present invention.

In the present invention, the problem of the third embodiment in which header decompression failure may occur for downlink data during handover may occur in the same manner as in FIG. 2L for uplink data during handover. Accordingly, in the following of the present invention, methods for solving the problem of the third embodiment that occur with respect to uplink data or downlink data are proposed as follows. It may be transmitted by applying one or more of the following methods.

-Method 1: During handover, the terminal, the source base station, or the target base station always configures and transmits a PDCP status report before transmitting or receiving data. That is, in the uplink case of the second embodiment, if the terminal receives the PDCP status report from the target base station, it can be seen that the terminal has already successfully received data corresponding to the PDCP serial number or COUNT value 100 to 106. Therefore, the IR packet can be transmitted by including data 107. As another method, the terminal may be characterized in that the terminal receives the PDCP status report from the target base station and then checks the generated data or generates data and transmits the data, and until the PDCP status report is received, the data generation or data You can also delay transmission. As another method, the retransmitted data may be characterized by retransmitting the data by checking the generated data after receiving the PDCP status report from the target base station or by generating the data. It may be characterized in that it may be characterized in that it may be characterized in that it may delay the generation or transmission of retransmitted data until the PDCP status report is received.

-Method 2: When performing handover, if the header compression procedure is set, the UE or the base station does not perform a header compression procedure on the transmitted data during handover or until the handover is completed. Instead, it may be characterized in that the IR packet is continuously included and transmitted. More specifically, in the above, the header compression protocol is in U mode (U-mode, a mode in which the receiving end does not request feedback (ACK or NACK) in unidirectional mode) or R mode (the receiving end receives ACK or NACK in R-mode, Reliable mode). Sending mode) or O mode (a mode in which the receiver sends NACK in O-mode, Optimistic mode), or when operating in an IR state (IR state) can generate and transmit IR packets. Therefore, when performing handover, the UE or base station sets the header compression protocol in U-mode (U-mode, unidirectional) during handover or until handover is completed for bearers for which the header compression procedure is set. Mode in which the receiving end does not request feedback (ACK or NACK) or R mode (R-mode, a mode in which the receiving end sends ACK or NACK in Reliable mode) or O mode (O-mode, a mode that receives NACK in Optimistic mode) This sending mode) or in the IR state (IR state) can be maintained or operated. If the header compression procedure is not applied and the IR packet is continuously transmitted as described above, the receiving PDCP layer device stores and synchronizes the ROHC context, and does not perform the header decompression procedure on the received data. No failure problem occurs. If the method 2 is applied to the first or second embodiment of the efficient handover method (for example, DAPS handover method) proposed in the present invention, when performing handover as described above, if header compression is performed. If the procedure is set, during handover or until handover is performed and handover is completed (i.e., when a handover command message is received or a random access procedure is completed to the target base station (when the first condition is satisfied)) Alternatively, the header compression procedure is not performed on the transmitted data until an instruction to release the connection with the source base station is received from the target base station (when the second condition is satisfied), and the IR packet is continuously included and transmitted. It can be characterized by that. More specifically, in the above, the header compression protocol is in U mode (U-mode, a mode in which the receiving end does not request feedback (ACK or NACK) in unidirectional mode) or R mode (the receiving end receives ACK or NACK in R-mode, Reliable mode). Sending mode) or O mode (a mode in which the receiver sends NACK in O-mode, Optimistic mode), or when operating in an IR state (IR state) can generate and transmit IR packets. Therefore, when performing an efficient handover (for example, a DAPS handover method), the UE or the base station performs handover for bearers for which the header compression procedure is set, or when the handover is completed (i.e. Receiving a handover command message or completing a random access procedure to the target base station (when satisfying the first condition) or receiving an instruction to release the connection with the source base station (when meeting the second condition) from the target base station U mode (U-mode, a mode in which the receiving end does not request feedback (ACK or NACK) in unidirectional mode) or R mode (R-mode, a reliable mode in which the receiving end receives ACK or NACK). Sending mode) or O mode (O-mode, a mode in which the receiving end sends NACK in optimistic mode) or in an IR state (IR state). When transmitting an IR packet in the handover procedure in Method 2, it may be transmitted by applying one or more of the following methods.

■ Method 2-1: In the above, the terminal, the source base station, or the target base station continues until a handover completion message is received from the terminal or until a PDCP status report is received, or until a predetermined timer expires or for a predetermined time. Thus, the transmitted data can be transmitted including an IR packet without applying a header compression procedure. And after that, a header compression procedure can be applied to transmitted data.

■ Method 2-2: In the above, the terminal, the source base station, or the target base station may transmit data received from the source base station including the IR packet without applying a header compression procedure. In addition, new downlink data received from the core network may be transmitted by applying a header compression procedure.

■ Method 2-3: In the above, the UE, the source base station, or the target base station may transmit the retransmitted data including the IR packet without applying a header compression procedure. In addition, downlink data that performs new transmission or is initially transmitted may be transmitted by applying a header compression procedure.

■ Method 2-4: In the above, the UE, the source base station, or the target base station may transmit the retransmitted data including the IR packet without applying the header compression procedure. In addition, for downlink data that performs new transmission or is transmitted for the first time, the first plurality of data may be transmitted including an IR packet, and data transmitted thereafter may be transmitted by applying a header compression procedure.

In order to further improve the performance of Method 2 proposed in the present invention, it is possible to use Method 2 during handover only when the sixth condition proposed in the following is satisfied. Because as described in the present invention, the header decompression failure problem described in the present invention occurs only when the header compression context (ROHC context) is not used as it is during handover, or when the header compression protocol is initialized. Therefore, if the header compression context (ROHC context) is used as it is during handover or the header compression protocol is not initialized, the methods proposed in the present invention need not be applied unnecessarily. For example, if the security key is not changed during handover, a separate procedure is not instructed to the UM bearer, or a PDCP data recovery procedure is instructed to the AM bearer, or a separate procedure is applied to the UM bearer for which the DAPS handover method is not set. A PDCP data recovery procedure is instructed to the AM bearer for which the procedure is not indicated or the DAPS handover method is not configured, and the second PDCP layer device structure is used for the bearer (UM or AM bearer) for which the DAPS handover method is configured. If the same header compression context for the bearers is continuously applied to the header compression context of the source base station and the header compression context of the target base station, it is not necessary to perform the proposed method 2 unnecessarily. If the above method 2 is used even when the header compression context (ROHC context) is used as it is during handover, or the header compression protocol is not initialized, the header compression context or the header compression protocol is unnecessarily initialized, resulting in unnecessary overhead. This may result in waste of transmission resources. In addition, method 2 proposed in the present invention is a bearer with a header compression protocol set (UM or AM bearer) in a general handover method or a bearer with a DAPS handover method set in an efficient handover method (DAPS handover method). ) Or to a bearer (UM or AM bearer) for which the DAPS handover method is not set, can be applied for each bearer. The sixth condition may indicate one or more of the following conditions.

-1) Header compression in the case of not using the header compression context (ROHC context) in the general handover method or the efficient handover method (DAPS handover method) or in the RRC message (for example, RRCReconfiguration message) indicating handover When an indicator to use the context as it is (eg drb-ContinueROHC) is not set or is not instructed

-2) Or when initializing the header compression protocol in a general handover method or an efficient handover method (DAPS handover method)

-3) Or in a general handover method or an efficient handover method (DAPS handover method), the header compression protocol is in U mode (U-mode, a mode in which the receiving end does not require feedback (ACK or NACK) in unidirectional mode) or R Mode (R-mode, a mode in which the receiving end sends ACK or NACK in Reliable mode) or O mode (a mode in which the receiving end sends NACK in O-mode, Optimistic mode) or in IR state or operates Occation,

-4) Or, in the general handover method or the efficient handover method (DAPS handover method), the header compression protocol is in U mode (U-mode, a mode in which the receiving end does not require feedback (ACK or NACK) in unidirectional mode) or R Mode (R-mode, a mode in which the receiving end sends ACK or NACK in Reliable mode) or O mode (a mode in which the receiving end sends NACK in O-mode, Optimistic mode) or in NC state or operates Occation,

-5) Or when the security key is changed when handover is performed in the general handover method or the efficient handover method (DAPS handover method) or when handover is instructed,

-6) When a handover is performed in a general handover method or an efficient handover method (DAPS handover method), or when a handover is instructed, security key or security setting information is set,

-7) Or when a general handover method or an efficient handover method (DAPS handover method) is indicated or configured, the header compression context for the source base station and the header compression context for the target base station are the same. If you are not using it as a context,

-8) Or when a general handover method or an efficient handover method (DAPS handover method) is indicated or set, the header compression context for the target base station is continuously used as the header compression context (ROHC context) for the source base station. If not,

-9) Or, when a general handover method or an efficient handover method (DAPS handover method) is indicated or set, the same header compression context is not continuously applied to the header compression context of the source base station and the header compression context of the target base station. If not,

In addition, when the efficient handover method proposed in the present invention (DAPS handover method) is instructed or set, the security key is not changed, or there is no security setting information, or when the security key change is not indicated or set, the DAPS A separate procedure is not instructed to a UM bearer with no handover method set, or a PDCP data recovery procedure is instructed to an AM bearer with no DAPS handover method set, or a bearer with a DAPS handover method set (UM or AM bearer). ) For the second PDCP layer device structure (a security key for a source base station or a security key for a target base station, a header compression context for a source base station, or a header compression context for a target base station, respectively, can be maintained and applied, The same header compression context for the bearers can be continuously applied to the header compression context of the source base station or the header compression context of the target base station using the structure of the PDCP layer device performing the rearrangement function), or to the source base station and the target base station. One and the same header compression context can be maintained and applied. Because if the security key is used as it is, but if the header compression context is initialized or reset, when the base station (or terminal) transmits or retransmits data, different data encrypted with the same security key (different headers compressed in different ways) Data) can be transferred, so a security problem can arise. That is, a hacker or a number of unspecified or unauthorized attackers may receive different data encrypted with the same security key and obtain useful information for deriving the security key, thereby causing a security problem.

Method 3: In the handover procedure, when transmitting an IR packet, the UE does not include the IR packet in uplink data (eg PDCP data PDU) and does not transmit uplink PDCP control data (eg PDCP control PDU). The IR packet may be included and transmitted in (eg, a new PDCP control PDU or interspersed ROHC feedback). Since the uplink PDCP control data is not assigned a COUNT value or a PDCP serial number, and is not discarded by a PDCP status report, the UE can always transmit PDCP control data including IR packets processed in advance, and multiple transmissions Or you can send it first. Accordingly, when the target base station receives the PDCP control data including the IR packet, the ROHC context can be received, stored, and synchronized, and the header decompression procedure can be normally applied to downlink data.

-Method 4: In the handover procedure, the receiving PDCP layer device performs a procedure to check whether the received data is data in the window (for example, only data in the window is determined as valid data) or a duplicate detection procedure, and data outside the window A decoding procedure may be performed, a header decompression procedure may be performed, and a procedure of extracting if an IR packet is included in the redundant data may be performed before discarding the data or redundant data. That is, if it is determined that data outside the header window or redundant data is determined in the procedure for checking whether the data is in the window or the duplicate detection procedure, the decoding procedure is performed before the data outside the window or the redundant data is discarded, and the header decompression procedure is performed. It checks whether the IR packet is included, stores the ROHC context information of the IR packet, if the IR packet is included, updates the ROHC context information of the receiving PDCP layer device, and then performs a header decompression procedure of the received data. By applying, the header compression decompression procedure can be performed. In the header decompression procedure, the procedure of checking whether an IR packet is included in the received data, storing ROHC context information of the IR packet if the IR packet is included, and updating ROHC context information of the receiving PDCP layer device are performed. Can include. When processing data outside the window or redundant data in the procedure for checking whether the data is within the window or the duplicate detection procedure proposed above, it may be transmitted by applying one of the following methods. In the following, the RCVD_COUNT value means the COUNT value corresponding to the received data, and RX_DELIV indicates the lower end of the window that meets the validity of the data in the receiving PDCP layer device, or the first (or still rearrangement) that has not been delivered to the upper layer. Indicates the COUNT value of the data (which has the lowest COUNT value waiting).

■ Method 4-1: In the method 4-1, before discarding data outside the window or redundant data, a decoding procedure is performed and a header compression decompression procedure is applied.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before (if the received data is duplicate data)

● 2> If the decoding procedure for the received PDCP Data PDU (the data part of the PDCP PDU) has not been performed, the decoding procedure is performed, and the header decompression procedure is performed (for example, if the IR packet is checked and there is no IR packet) ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-2: In the method 4-2, before discarding data outside the window or redundant data, a decoding procedure is performed and a header decompression procedure is applied. In addition, in the above method 4-2, in order to enhance security, if the COUNT value corresponding to the currently received data has been previously received, and the data corresponding to the COUNT value has been successfully received (if integrity protection And if the verification procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred, and the received data is discarded to perform the duplicate detection procedure. It can be improved to prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and the integrity protection and verification procedure has been set, the integrity verification procedure for the PDCP PDU corresponding to the RCVD_COUNT value has previously been successfully performed. If ever

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been set.

● 2> If the decoding procedure for the received PDCP Data PDU (the data part of the PDCP PDU) has not been performed, the decoding procedure is performed, and the header decompression procedure is performed (for example, if the IR packet is checked and there is no IR packet) ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-3: In Method 4-3, data outside the window or redundant data only in the handover procedure, only when the header compression protocol is initialized, or when the header compression protocol is in the U mode NC (No context) state. It may be characterized in that a decoding procedure is performed and a header compression decompression procedure is applied before being discarded. The operation may be performed in a U mode (Unidirectional mode), O mode (Bidirectional Optimistic Mode) or R mode (Bidirectional Reliable Mode) in NC state (No Context) or SC state (Static Context). That is, even if an expired or duplicated packet is not immediately discarded, it is decoded, integrity verification is performed, and header decompression is performed. Therefore, even if an IR packet is carried in the duplicated packet, the PDCP layer device at the receiving end may receive it, check all header information and ROHC protocol configuration information, and complete synchronization with the transmitting end ROHC protocol. Accordingly, header-compressed PDCP PDUs transmitted from the transmitting end can be successfully decompressed.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before (if the received data is duplicate data)

● 2> If the header decompression protocol (ROHC) is in the NC state of U mode (or the header compression protocol has been reset and has not been reset)

■ 3> If the decoding procedure is not performed for the received PDCP Data PDU (the data part of the PDCP PDU), the decoding procedure is performed, and the header decompression procedure is performed (e.g., check the IR packet and if there is no IR packet). ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 4-4: In Method 4-4, data outside the window or redundant data only in the handover procedure, only when the header compression protocol is initialized, or when the header compression protocol is in the U mode NC (No context) state. It may be characterized in that a decoding procedure is performed and a header compression decompression procedure is applied before being discarded. The operation may be performed in a U mode (Unidirectional mode), O mode (Bidirectional Optimistic Mode) or R mode (Bidirectional Reliable Mode) in NC state (No Context) or SC state (Static Context). That is, even if an expired or duplicated packet is not immediately discarded, it is decoded, integrity verification is performed, and header decompression is performed. Therefore, even if an IR packet is carried in the duplicated packet, the PDCP layer device at the receiving end may receive it, check all header information and ROHC protocol configuration information, and complete synchronization with the transmitting end ROHC protocol. Accordingly, header-compressed PDCP PDUs transmitted from the transmitting end can be successfully decompressed. In addition, in order to enhance security, the method 4-4 above has previously received the COUNT value corresponding to the currently received data, and if the data corresponding to the COUNT value has been successfully received (if integrity protection And if the verification procedure is set, if the data corresponding to the COUNT value has been previously received and the integrity verification procedure has been successfully performed), it is determined that duplicate detection has occurred, and the received data is discarded to perform the duplicate detection procedure. It can be improved to prevent hacker attacks. In addition, if integrity protection and verification procedures are not set, the COUNT value corresponding to the currently received data can be immediately discarded if it has been previously received.

◆ 1> If RCVD_COUNT <RX_DELIV (if the received data is outside the window)

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before, and the integrity protection and verification procedure has been set, the integrity verification procedure for the PDCP PDU corresponding to the RCVD_COUNT value has previously been successfully performed. If ever

◆ If a PDCP PDU with a value of 1> or RCVD_COUNT has been successfully received before and if integrity protection and verification procedures have not been set.

● 2> If the header decompression protocol (ROHC) is in the NC state of U mode (or the header compression protocol has been reset and has not been reset)

■ 3> If the decoding procedure is not performed for the received PDCP Data PDU (the data part of the PDCP PDU), the decoding procedure is performed, and the header decompression procedure is performed (e.g., check the IR packet and if there is no IR packet). ROHC context can be saved or updated).

● 2> Discard the received PDCP Data PDU (the data part of the PDCP PDU).

■ Method 5: For Method 1, Method 2, Method 3, and Method 4, a downlink source data-based data redundancy transmission method (PDCP SDU based duplication) in a handover command message (or RRC message) or an efficient hand in the first embodiment Apply the proposed duplicate detection procedure applicable when the over method is set or not set, and apply the header decompression procedure by applying the above methods to the data determined to be duplicate data (or data outside the window) Then, the redundant data (or data outside the window) can be discarded.

The various embodiments in which a header decompression failure problem may occur during handover in the present invention may be applied to PDCP layer devices or bearers driven in RLC AM mode, and PDCP layer devices driven in RLC UM mode It can be extended and applied to bearers. In addition, by extending the above embodiments, when the PDCP re-establishment procedure is triggered for the RLC UM mode or RLC AM mode in the RRC message, or when the PDCP data recovery procedure is triggered, or when a handover or a handover command message is received. Alternatively, when transmitting a handover completion message, an indicator to configure and transmit a PDCP status report may be newly defined and instructed to the UE.

2M is a diagram showing the operation of a terminal proposed in the present invention.

In FIG. 2m, when the terminal 2m-01 receives a handover command message (eg, RRC message) from the base station (2m-05), it performs a procedure according to the handover method indicated in the handover command message, and the The handover procedure is performed by performing the function indicated in the handover command message (2m-10). In addition, when the header decompression failure error described in the present invention occurs, for example, Method 1 or Method 2 or Method 3 or Method 4 to prevent problems such as the first embodiment, the second embodiment, or the third embodiment. Alternatively, a data transmission/reception procedure may be performed according to method 5 (2m-15).

The terminal operation described above may be extended to the base station and applied to the operation of the base station.

2N shows the structure of a terminal to which an embodiment of the present invention can be applied.

Referring to the figure, the terminal includes a radio frequency (RF) processing unit 2n-10, a baseband, a processing unit 2n-20, a storage unit 2n-30, and a control unit 2n-40. do.

The RF processing unit 2n-10 performs a function of transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processing unit 2n-10 up-converts the baseband signal provided from the baseband processing unit 2n-20 into an RF band signal and transmits it through an antenna, and the RF band signal received through the antenna Is down-converted to a baseband signal. For example, the RF processing unit 2n-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), and the like. I can. In the drawing, only one antenna is shown, but the terminal may include a plurality of antennas. In addition, the RF processing unit 2n-10 may include a plurality of RF chains. Furthermore, the RF processing unit 2n-10 may perform beamforming. For the beamforming, the RF processing unit 2n-10 may adjust a phase and a magnitude of signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit may perform MIMO, and may receive multiple layers when performing the MIMO operation. The RF processing unit 2n-10 may perform reception beam sweeping by appropriately setting a plurality of antennas or antenna elements under the control of the controller, or adjust the direction and beam width of the reception beam so that the reception beam cooperates with the transmission beam. have.

The baseband processing unit 2n-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the system. For example, when transmitting data, the baseband processing unit 2n-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 2n-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 2n-10. For example, in the case of the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit 2n-20 generates complex symbols by encoding and modulating a transmission bit stream, and subcarriers of the complex symbols After mapping to, OFDM symbols are constructed through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processing unit 2n-20 divides the baseband signal provided from the RF processing unit 2n-10 in units of OFDM symbols, and applies a fast Fourier transform (FFT) operation to subcarriers. After reconstructing the mapped signals, the received bit stream is restored through demodulation and decoding.

The baseband processing unit 2n-20 and the RF processing unit 2n-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 2n-20 and the RF processing unit 2n-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, or a communication unit. Furthermore, at least one of the baseband processing unit 2n-20 and the RF processing unit 2n-10 may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit 2n-20 and the RF processing unit 2n-10 may include different communication modules to process signals of different frequency bands. For example, the different radio access technologies may include an LTE network, an NR network, and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.5GHz, 5Ghz) band, and a millimeter wave (eg, 60GHz) band.

The storage unit 2n-30 stores data such as a basic program, an application program, and setting information for the operation of the terminal. The storage unit 2n-30 provides stored data according to the request of the control unit 2n-40.

The controller 2n-40 controls overall operations of the terminal. For example, the control unit 2n-40 transmits and receives signals through the baseband processing unit 2n-20 and the RF processing unit 2n-10. Also, the control unit 2n-40 writes and reads data in the storage unit 2n-40. To this end, the control unit 2n-40 may include at least one processor. For example, the controller 2n-40 may include a communication processor (CP) that controls communication and an application processor (AP) that controls an upper layer such as an application program.

2O is a block diagram of a TRP in a wireless communication system to which an embodiment of the present invention can be applied.

As shown in the drawing, the base station includes an RF processing unit (2o-10), a baseband processing unit (2o-20), a backhaul communication unit (2o-30), a storage unit (2o-40), and a control unit (2o-50). Consists of including.

The RF processing unit 2o-10 performs functions for transmitting and receiving signals through a wireless channel, such as band conversion and amplification of signals. That is, the RF processing unit 2o-10 up-converts the baseband signal provided from the baseband processing unit 2o-20 to an RF band signal and transmits it through an antenna, and the RF band signal received through the antenna Downconverts to a baseband signal. For example, the RF processing unit 2o-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. In the drawing, only one antenna is shown, but the first access node may include a plurality of antennas. In addition, the RF processing unit 2o-10 may include a plurality of RF chains. Furthermore, the RF processing unit 2o-10 may perform beamforming. For the beamforming, the RF processing unit 2o-10 may adjust a phase and a magnitude of each of signals transmitted and received through a plurality of antennas or antenna elements. The RF processor may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 2o-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the first wireless access technology. For example, when transmitting data, the baseband processor 2o-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 2o-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 2o-10. For example, in the case of the OFDM scheme, when transmitting data, the baseband processing unit 2o-20 generates complex symbols by encoding and modulating a transmission bit stream, mapping the complex symbols to subcarriers, and then IFFT OFDM symbols are configured through calculation and CP insertion. In addition, when receiving data, the baseband processing unit 2o-20 divides the baseband signal provided from the RF processing unit 2o-10 in units of OFDM symbols, and reconstructs signals mapped to subcarriers through FFT operation. After that, the received bit stream is restored through demodulation and decoding. The baseband processing unit 2o-20 and the RF processing unit 2o-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 2o-20 and the RF processing unit 2o-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, a communication unit, or a wireless communication unit.

The communication unit 2o-30 provides an interface for performing communication with other nodes in the network.

The storage unit 2o-40 stores data such as a basic program, an application program, and setting information for the operation of the main station. In particular, the storage unit 2o-40 may store information on bearers allocated to the connected terminal, measurement results reported from the connected terminal, and the like. In addition, the storage unit 2o-40 may store information that is a criterion for determining whether to provide or stop providing multiple connections to the terminal. In addition, the storage unit 2o-40 provides stored data according to the request of the control unit 2o-50.

The control unit 2o-50 controls overall operations of the main station. For example, the control unit 2o-50 transmits and receives signals through the baseband processing unit 2o-20 and the RF processing unit 2o-10 or through the backhaul communication unit 2o-30. In addition, the control unit 2o-50 writes and reads data in the storage unit 2o-40. To this end, the control unit 2o-50 may include at least one processor.

Claims (1)

In the control signal processing method in a wireless communication system,
Receiving a first control signal transmitted from a base station;
Processing the received first control signal; And
And transmitting a second control signal generated based on the processing to the base station.

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