KR101058687B1 - Method and apparatus for receiving control message using serial number in multimedia broadcasting / multicast service - Google Patents

Abstract

The present invention relates to a method and apparatus for applying selective combining using RLC serial number to MBMS control message in MBMS communication system. According to the present invention, a terminal receives the data units in a communication system in which a control message for a multimedia broadcasting / multicast (MBMS) service is divided or concatenated into a plurality of data units and serial numbers are assigned to the data units. The method for receiving the control message may include receiving a plurality of data units each including at least one control message and having a serial number, and storing the received data units in an order according to the serial number; Determining whether there are first data units that can be assembled into a first control message among the data units, and if the first data units exist, at least that can be assembled into a second control message among the stored data units; Determining whether one second data unit exists; If the data unit exists, copying the second data unit and storing the copied second data unit again; assembling the first data units except for the copied second data unit to form a control message. And the same data units have the same serial number regardless of the time of transmission. This invention makes it possible to receive MBMS control messages quickly and accurately.

MBMS, MCCH, RLC PDU, RRC

Description

METHOD AND APPARATUS FOR OBTAINING CONTROL MESSAGE USING SEQUENCE NUMBERS IN MULTIMEDIA BROADCAST / MULTICAST SERVICE}             

1 is a simplified block diagram of a mobile communication system for an MBMS service to which the present invention is applied;

2 is a diagram illustrating a hierarchical structure of a Uu interface for communication of data and signaling messages between a terminal and an RNC to which the present invention is applied.

3A and 3B are diagrams illustrating a case where selective combining is not applied to an MBMS control message and an example of transmission when it is applied.

4 is a structural diagram of a terminal according to a first embodiment of the present invention;

5 is a flowchart illustrating the operation of an OOS delivery entity according to a first embodiment of the present invention.

FIG. 6 is a view for explaining an example of LI applied to the present invention. FIG.

7 is a structural diagram of a terminal according to a second embodiment of the present invention;

8 is a diagram for explaining the structure of an SCR window according to a second embodiment of the present invention;

9 is a flowchart illustrating operation of an RLC entity according to a second embodiment of the present invention.

The present invention relates to a Multicast Multimedia Broadcast Service (hereinafter, referred to as an MBMS service), and more particularly, to a method and apparatus for receiving control information for an MBMS service.

Due to the development of communication technology, the services provided by the mobile communication system using the wideband code division multiple access (CDMA) scheme are not only conventional voice services but also large capacity such as packet data and circuit data. It is evolving into packet service communication for transmitting data and multimedia broadcasting / communication for transmitting multimedia service. Accordingly, in order to support the multimedia broadcasting / communication, an MBMS service that provides a service from one or more multimedia data sources to a plurality of user equipments (hereinafter referred to as UEs) has been discussed.

The MBMS service refers to a service for transmitting the same multimedia data to multiple receivers through a wireless network. In this case, by allowing multiple receivers to share one radio channel, it is possible to save radio transmission resources. The MBMS service supports multimedia transmission forms such as real-time video, audio, still images, and text. The MBMS service is a service that can simultaneously provide audio data and video data according to the multimedia transmission format, and requires a large amount of transmission resources. In the case of the MBMS service, since the same data must be transmitted to a plurality of cells in which users are located, one-to-one (Point to Point: PtP) or one-to-many (Point to Multiple :) Called PtM).

In order to receive MBMS service, UEs must first acquire control information on a transport channel carrying an MBMS service data stream, that is, an MBMS transport channel (hereinafter referred to as MTCH). The control information may include code information on a physical channel to which the transport channel is mapped, a service identifier for the MBMS service, information indicating that the MBMS service is started, information on types of services available at a corresponding time in a specific cell, and the like. Include. The control information is transmitted through an MBMS Control Channel (hereinafter referred to as MCCH), which is a separate common channel distinguished from the transport channel.

The MCCH is configured for each cell and all user terminals located in the cell should be able to access the MCCH. Therefore, the MCCH must have sufficient power level to be transmitted until cell change. However, since this may result in excessive consumption of forward transmission resources, instead of reducing the MCCH transmission output, the same message containing one MBMS control information (hereinafter referred to as MBMS control message) within one modification period (Modification Period) By retransmitting several times per repetition, a scheme for increasing the likelihood that a terminal located in a cell change successfully receives an MBMS control message has been introduced. This scheme is efficient when the size of the MBMS control message is small, but has a disadvantage in that the transmission efficiency is low when the size of the MBMS control message is large.                         

In a mobile communication system, an MBMS control message is divided or concatenated into data units having a size suitable for transmission on a wireless channel. If the MBMS control message has a small size, the MBMS control message can be stored in one data unit. However, if the MBMS control message has a large size, the MBMS control message is divided into 6 to 7 data units. When the MBMS control message is divided into a plurality of data units, the terminal must receive all data units divided from one MBMS control message to obtain the MBMS control message. Therefore, as the MBMS control message is larger, the probability that the UE successfully receives the MBMS control message is reduced.

In order to solve this problem, a selective combining method using serial numbers for transmitting and receiving MBMS control messages has been discussed. Selective combinations using serial numbers typically consist of duplicate checks and reordering. However, when order rearrangement is used to receive the MBMS control message, the control operation may not be performed efficiently.

That is, since the MBMS control message contains control information necessary for reception of the MTCH, it is necessary for the terminal to acquire the MBMS control message as soon as possible in order to use the MBMS service. As an example, since information such as a probability value used by UEs to receive a specific MBMS service to attempt RRC connection establishment is updated with a relatively short period, it should be obtained as soon as possible. However, if it fails to receive the preceding data unit of the MBMS control message, the terminal waits to receive the corresponding data unit of the next MBMS control message to be retransmitted. This delays the delivery of the MBMS control message, resulting in a delay in the reception of the MBMS service.

Accordingly, an object of the present invention, which was devised to solve the problems of the prior art operating as described above, is to provide a method and apparatus for performing selective combining using serial numbers in transmitting and receiving MBMS control messages in an MBMS system. .

An embodiment of the present invention, which is designed to achieve the above object, divides or concatenates a control message for a multimedia broadcasting / multicast (MBMS) service into a plurality of data units and assigns serial numbers to the data units. In the communication system for granting and transmitting the terminal for receiving the data units to receive the control message,

Receiving a plurality of data units including at least one control message and each having a serial number and storing the received data units in order according to the serial number;

Determining whether there are first data units that can be assembled into a first control message among the stored data units;

If the first data units exist, determining whether there is at least one second data unit that can be assembled into a second control message among the stored data units;

If the second data unit exists, copying the second data unit and storing the copied second data unit again;

Assembling the first data units other than the copied second data unit to form a control message,
Regardless of the transmission time, the same data units have the same serial number.

According to another embodiment of the present invention, in a communication system in which a control message for a multimedia broadcasting / multicast (MBMS) service is divided or concatenated into a plurality of data units and a serial number is assigned to the data units, the terminal transmits the control message. A method for receiving data units by receiving data units, the method comprising:

When receiving a data unit including at least a part of a control message and having a predetermined serial number, checking whether the serial number of the data unit is included in a predetermined window;

Storing the data unit in a buffer if the serial number is not included in the window;

Determining whether a data unit having the serial number is already stored in the buffer when the serial number is included in the window;

If the data unit having the serial number is not already stored, storing the data unit in the buffer;

Determining whether there are first data units that can be assembled into a first control message among the stored data units;

If the first data units exist, assembling the first data units to form the first control message;
Regardless of the transmission time, the same data units have the same serial number.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The present invention to be described later is to receive the MBMS control message including the MBMS control information, that is, the MBMS control message quickly and efficiently in the mobile communication system providing the MBMS service.

First, the MBMS service applied to the present invention will be described.

1 shows a simplified configuration diagram of a mobile communication system for an MBMS service. Here, an example of applying a MBMS service to a 3GPP (3rd Generation Project Partnership) system, which is a standard of third generation asynchronous mobile communication, is illustrated.

Referring to FIG. 1, UEs 161, 162, 163, 171, and 172 refer to terminal devices or subscribers capable of receiving MBMS services, and are referred to as cell 1 160 and cell 2 170. Is controlled by a base station apparatus, Node B, which wirelessly transmits MBMS related data to subscribers. A Radio Network Controller (RNC) 140 controls the plurality of cells 160 and 170, selectively transmits multimedia data to a specific cell, and is configured to provide MBMS service. Control the wireless channel. The connection between the RNC 140 and the UEs 161-172 is called a Radio Resource Control (RRC) interface.

The RNC 140 is connected to a Packet Switched or Packet Service (PS) network such as the Internet by a Serving GPRS Support Node (hereinafter referred to as 'SGSN') 130. Communication between the RNC 140 and the PS network is made by packet switched signaling (PS signaling). In particular, the connection between the RNC 140 and the SGSN 130 is called an Iu-PS interface.

SGSN 130 controls the MBMS-related services of each subscriber. Representative examples of the role played by the SGSN 130 include managing a service related data of each subscriber and selectively transmitting multimedia data to a specific RNC 140.

The Transit NW 120 provides a communication path between the Broadcast Multicast Service Center (BM-SC) 110 and the SGSN 130 and to an external network through a Gateway GPRS Support Node (GGSN). Can be connected. The BM-SC 110 is responsible for scheduling MBMS data as a source of MBMS data.

Meanwhile, the RNC 140 is connected to a circuit switched (CS) network by a mobile switching center (hereinafter referred to as 'MSC') 150. The CS network refers to a voice-based legacy communication network that is connection-based. Communication between the RNC 140 and the MSC 150 is performed by circuit switched signaling (CS signaling). In particular, the connection between the RNC 140 and the MSC 150 is called an Iu-CS interface. MBMS data streams are delivered to UEs 161, 162, 163, 171 and 172 via the transport network 120, SGSN 130, RNC 140, Node B and cells 160, 170.

Although not shown in FIG. 1, there may be a plurality of SGSNs for one MBMS service and a plurality of RNCs for each SGSN. Each SGSN is an RNC 140, and each RNC performs selective data transmission to each of a plurality of cells, and for this purpose, a list of nodes to which a data stream should be delivered (that is, SGSN is a list of RNCs and an RNC is a list of cells). List) and the like, and selectively transmit MBMS data only to the stored nodes later.

2 illustrates a hierarchical structure of a Uu interface for communication of data and signaling messages between a terminal and an RNC. Herein, the control plane is used to exchange control signals between the UE and the RNC, and the user plane is used to transmit actual data.

Referring to FIG. 2, the control plane 100 includes a radio resource control (RRC) layer 102, a radio link control (RLC) layer 210, a media access control (MAC) layer 112, and physical (Physical). (Hereinafter referred to as a PHY) layer 114, the user plane 102 includes a packet data control protocol (PDCP) layer 206, a broadcast / multicast control (BMC) layer 108, an RLC layer 110, There is a MAC layer 112, a physical layer 114. In a typical case, the physical layer 114 of the layers is located in each cell, that is, Node Bs, and is located in the RNC from the MAC layer 112 to the RRC layer 104.

The physical layer 114 is a layer that provides an information transmission service using a radio transfer technology, and corresponds to a first layer of an Open Systems Interconnection (OSI) model. The physical layer 114 and the MAC layer 112 are connected by transport channels, which are defined by the manner in which specific data is processed in the physical layer.

The MAC layer 112 and the RLC layer 110 are connected through a logical channel. The MAC layer 112 transmits the data delivered by the RLC layer 110 through the logical channel to the physical layer through an appropriate transport channel, and the data transmitted by the physical layer 114 through the transport channel through an appropriate logical channel. It serves to deliver to the RLC layer 110. In addition, by inserting additional information into the data received through the logical channel or the transport channel or by analyzing the inserted additional information to take appropriate action, and controls the random access operation.

The RLC layer 110 is responsible for establishing and releasing logical channels. The RLC layer 110 may operate in one of three operation modes such as an acknowledgment mode (AM), an unacknowledged mode (UM), and a transparent mode (TM), and provide different functions for each operation mode. In particular, the RLC layer 110 divides / concatenates a service data unit (hereinafter referred to as SDU) from an upper layer into an appropriate size or a protocol data unit (hereinafter referred to as RLC PDU) from an lower layer. It is responsible for assembling them, and for error correction through ARQ (Automatic Repeat reQuest).

The PDCP layer 106 is located above the RLC layer 110 in the user plane 102. The PDCP layer 106 compresses and restores headers of data transmitted in the form of IP packets, and provides an RNC service to a specific terminal with mobility. It is responsible for the lossless transfer of data, etc. under the situation that is changed. The PDCP layer 106 is responsible for lossless SRNS relocation support and header compression in the case of normal services, but in the case of MBMS services, lossless SRNS (Serving RNS) redirection is due to broadcast / multicasting characteristics. There is no need to support allocation. Here, SRNS reassignment refers to a process of resetting the other RNC to the SRNC by a UE moved to a cell controlled by another RNC other than the SRNC. The BMC layer 108 is located above the RLC layer 110 and supports a broadcast service for transmitting the same data to a plurality of unspecified terminals in a specific cell.

The RRC layer 104 is responsible for allocating and releasing radio resources between the UTRAN and the terminal. The RRC layer 104 manages radio resources allocated to terminals in an RRC connected mode, manages mobility of the terminals, and transmits core network signals to the terminals to be transmitted to the terminals. It serves to convey.

Since the MBMS control message is control information, it is generated by the RRC layer 204 of the control plane 200 and divided and assembled by the RLC layer 210. That is, when the RLC layer 210 receives the SDU containing the MBMS control message from the RRC layer 204, the RLC layer 210 reconfigures the SDU into a plurality of PDUs having a predetermined size (hereinafter referred to as RLC PDUs). A header including a serial number is added for each and then transferred to the MAC layer 212, which is a lower layer.

There are two major divisions and concatenation methods for reconstructing the RLC PDU. In the case where the size of the RLC SDU is larger than the RLC PDU, the splitting refers to a method of dividing the RLC SDU into an appropriate size and then putting the RLC SDU into several RLC PDUs. The concatenation means a method in which several RLC SDUs are contained in one RLC PDU when the size of the RLC SDU is smaller than the RLC PDU. Both schemes may be used for one RLC SDU, for example if one RLC SDU is split into three RLC PDUs and the last piece of the RLC SDU has a size smaller than one RLC PDU, the RLC The last piece of the SDU is concatenated with the first piece of the next RLC SDU and stored in one RLC PDU.

Upon reception, the RLC layer 210 receives the RLC PDUs from the MAC layer 212, rearranges and combines them according to serial numbers, constructs an SDU containing an MBMS control message, and delivers the SDUs to the RRC layer 204. In the case of the MBMS service performed in the forward direction, the RLC layer of the base station is responsible for partitioning the MBMS control message, and the RLC layer of the user terminal is responsible for assembling the MBMS control message.                     

Here, the selective combining of the RLC PDUs performed by the RLC layer 210 will be described.

3A illustrates an example of transmission when selective combining is not applied to an MBMS control message, and FIG. 3B illustrates an example of transmission when selective combining is applied to an MBMS control message.

In FIG. 3A, the RRC layer of the RNC generates MBMS control message 1 305, MBMS control message 2 110, and MBMS control message 3 330. The messages are delivered to the RLC layer. The RLC layer divides the messages into RLC PDUs, reconstructs them, and sequentially assigns serial numbers. In this case, the MBMS control message 1 305 is divided into an RLC PDU 106 having a serial number '1', an RLC PDU 107 having a serial number '2', and an RLC PDU 108 having a serial number '3'. . Hereinafter, an RLC PDU having a serial number n is called RLC PDU n. MBMS control message 2 310 is reconfigured and transmitted to RLC PDU 4 311.

After a certain time, the RNC determines retransmission of MBMS control message 2 315 and forwards MBMS control message 2 315 to the RLC layer. The RLC layer reconfigures and transmits MBMS control message 2 315 to RLC PDU 5 316. After some time again, the RNC decides to retransmit MBMS control message 1 320 and forwards MBMS control message 1 320 to the RLC layer. The RLC layer reconfigures and transmits the MBMS control message 1 320 as an RLC PDU 6 321, an RLC PDU 7 322, and an RLC PDU 8 323. Similarly, the MBMS control message 2 325 is reconfigured and transmitted to the RLC PDU 326, and the new MBMS control message 3 330 is reconfigured and transmitted to the RLC PDU 10 331 and the RLC PDU 11 332.                     

However, if the serial numbers of the RLC PDUs corresponding to one MBMS control message are differently assigned as described above, the UE receiving the RLC PDUs contains the same data in the RLC PDU 1 306 and the RLC PDU 6 321. I can't recognize that it is. Therefore, in order for the UE to receive MBMS control message 1 (305 or 320), the UE receives both RLC PDU 1 306, RLC PDU 2 307, and RLC PDU 3 308, or RLC PDU 6 321 and the like. Both RLC PDU 7 322 and RLC PDU 8 323 must be received.

For example, even though a terminal has successfully received the RLC PDU 1 306 and the RLC PDU 2 307, and has successfully received the RLC PDU 6 321 and the RLC PDU 8 323, the terminal is finally received. Failure to acquire MBMS Control Message 1 (305 or 320). To solve this problem, a method of applying selective combining using RLC serial number when transmitting and receiving MBMS control messages has been proposed.

Referring to FIG. 3B, MBMS control message 1 335 and 350 are transmitted twice, and MBMS control message 2 340, 345 and 355 are transmitted three times. At this time, the RLC PDUs 336 to 338 and 351 to 353 of the MBMS control message 1 335 and the MBMS control message 1 350 are assigned the same RLC serial numbers # 1, 2, and 3. Accordingly, when the UE receives the RLC PDU 1 336 or 351, the RLC PDU 2 337 or 352, and the RLC PDU 3 338 or 353, the UE succeeds in obtaining the MBMS control message 1 (335 or 350). Since the RLC PDU 1 (336 or 351), the RLC PDU 2 (337 or 352) and the RLC PDU 3 (338 or 353) are transmitted twice each, the probability that the UE succeeds in receiving the MBMS control message 1 (335 or 350) Also increases.

For example, if the UE succeeds in receiving the RLC PDU 1 336 and the RLC PDU 2 337, and then receives the RLC PDU 1 351 and the RLC PDU 3 353, the UE receives the RLC PDU 1 336 or the like. 351 and RLC PDU 2 337 and RLC PDU 3 353 are combined to obtain MBMS control message 1 (335 or 350).

In the following, two embodiments will be disclosed for the RLC entity to assemble protocol data units (PDUs) split from MBMS control messages using serial numbers. The first embodiment complements the existing selective coupling scheme such as MTCH, and the second embodiment applies the selective coupling scheme to the RLC layer.

<< first embodiment >>

4 illustrates a structure of a terminal according to the first embodiment of the present invention. As illustrated, a physical (PHY) entity 535, a MAC entity 530, a duplication check entity 525, It is composed of an order reorder buffer (order reorder buffer) 520, an Out Of Sequence (OOS) delivery entity 515, an RLC entity 510, and an RRC entity 505. Among the entities, the roles of the entities other than the OOS delivery entity 515 are briefly described below.

The physical object 535 is responsible for a physical layer protocol for processing a radio signal received through a radio channel, and serves as despreading, demodulation, and channel decoding of a forward radio signal. To perform.

The MAC entity 530 is responsible for the protocol of the MAC layer to interpret the MAC header from the data delivered by the physical layer, and process accordingly. The MAC header includes multiplexing information (TCTF: Target Channel Type Field). Data from which the MAC header is removed becomes an RLC PDU.

The duplicate confirmation entity 525 discards already received RLC PDUs among the RLC PDUs transmitted from the MAC entity 530, and supports only the newly received RLC PDUs to the reorder buffer 520 to support selective combining. To pass.

The reorder buffer 520 stores the RLC PDUs delivered from the duplicate acknowledgment entity 525 in order according to the serial number, and delivers the correct RLC PDUs to the RLC layer in order to support selective combining of the RLC layers. .

The OOS delivery entity 515 checks the header information of the RLC PDUs stored in the reorder buffer 520 to support the selective combining of MBMS control messages, and identifies the RLC PDUs that can be assembled into SDUs so that they can be RLC. The order rearrangement buffer 520 is controlled to be delivered to the layer. Here, assembling into SDUs means that all RLC PDUs required to assemble one SDU are present in the sequence rearrangement buffer 520. Specifically, the header information of the RLC PDUs is a serial number (SN) and a length indicator (hereinafter referred to as LI) which are sequentially assigned to one MBMS control message.

The RLC entity 510 is responsible for the protocol of the RLC layer, combines the RLC PDUs delivered from the reorder buffer 520 of the RLC layer, and delivers the MBMS control message to the upper layer RRC entity 505 as an SDU. do. The RRC entity 505 then interprets the MBMS control message delivered by the RLC entity 510 and takes the necessary action.

The operation of the OOS delivery entity 515 is related to the main features of the first embodiment of the present invention.

5 is a flowchart showing the operation of the OOS delivery entity according to the first embodiment of the present invention.

Referring to FIG. 5, in step 605, a new RLC PDU arrives in the reorder buffer. The RLC PDU is stored at an appropriate location based on the serial number included in the header information therein. In step 610, the OOS delivery entity examines the serial numbers and LIs of the RLC PDUs stored in the reorder buffer. The LI is information supporting division / concatenation performed in the RLC entity, and indicates the end point of the SDU, that is, the MBMS control message, in bytes in the RLC PDU. A more detailed description of the LI will be described later with reference to FIG. 6.

In step 615, the OOS delivery entity checks whether there are RLC PDUs that can be assembled into SDUs among the RLC PDUs stored in the reorder buffer. This is done by determining whether there is at least one unreceived RLC PDU between the RLC PDU containing the start of one SDU and the RLC PDU containing the end of the SDU.

For example, the RLC PDUs stored in the reorder buffer have SN and LI as shown in Table 1 below.

SN LI Payload n x SDU i, SDU k n + 1 n / a SDU k n + 2 n / a SDU k n + 3 y SDU k, SDU j n + 4 n / a SDU j n + 7 z SDU j, SDU h

According to Table 1, SDU k starts at the x + 1 th payload byte of the RLC PDU (SN = n) and ends at the y th payload byte of the RLC PDU (SN = n + 3). have. And there is no unreceived RLC PDU between the RLC PDU (SN = n) and (SN = n + 3). Therefore, the RLC PDU (SN = n), the RLC PDU (SN = n + 1), the RLC PDU (SN = n + 2), and the RLC PDU (SN = n + 3) are determined to be RLC PDUs that can be assembled. .

Hereinafter, RLC PDUs that can be assembled into SDUs are referred to as RLC PDU_Rs. RLC PDU_Rs refer to RLC PDUs that are included in a set of RLC PDUs having consecutive serial numbers, including the start and end points of a specific SDU.

In other words, in step 615, it is determined whether RLC PDU_R exists among the RLC PDUs stored in the reorder buffer. If the RLC PDU_R does not exist, that is, the assembly of the SDU is not possible, the OOS delivery entity proceeds to step 635 and waits for the next RLC PDU to arrive in the reorder buffer. On the other hand, if there is an RLC PDU_R, the flow proceeds to step 620.

In step 620, the OOS delivery entity determines whether there is an RLC PDU concatenated with another SDU among the RLC PDU_Rs. Taking Table 1 as an example, SDU i and SDU k are concatenated in RLC PDU (SN = n), and SDU k and SDU j are concatenated in RLC PDU (SN = n + 3). As such, RLC PDUs concatenated with two or more RLC SDUs are referred to as RLC PDU_C hereinafter. In step 620, if there is no RLC PDU_C among the RLC PDU_Rs, the process proceeds to step 630, and if present, the process proceeds to step 625.

In step 625, the OOS delivery entity duplicates and stores the RLC PDU_Cs. Then, two RLC PDUs, RLC PDU_R and RLC PDU_C, exist in the reorder buffer. In step 630, the OOS delivery entity delivers the RLC PDU_Rs stored in the reorder buffer to the upper layer. In this case, if the RLC PDU_Cs are copied in step 625, one RLC PDU_Cs are still stored in the reorder buffer. This is to ensure the opportunity to be reassembled to other RLC SDUs included in the RLC PDU_C.

Taking Table 1 again as an example, in step 625, the OOS forwarding entity copies an RLC PDU (SN = n) and an RLC PDU (SN = n + 3) corresponding to RLC PDU_R and RLC PDU_C. As a result, there are two RLC PDUs (SN = n) and RLC PDUs (SN = n + 3) in the reorder buffer. In step 630, the OOS forwarding entity selects an RLC PDU (SN = n), an RLC PDU (SN = n + 1), an RLC PDU (SN = n + 2), and an RLC PDU (SN = n + 3) corresponding to the RLC PDU_R. Pass it to the upper layer. At this point, the RLC PDU (SN = n) and RLC PDU (SN = n + 3) remain in the reorder buffer. The RLC PDUs will be delivered together when SDU i or SDU j is completed and delivered to a higher layer.

Of course, if there is no RLC PDU_C among the RLC PDU_Rs, step 625 is not necessary.

The OOS entity that delivered the RLC PDU_Rs to the higher layer in step 630 waits until the next RLC PDU arrives in the reorder buffer.

Figure 6 shows in more detail in the application of LI applied to the present invention. The LI relates to the function of the RLC entity.                     

Referring to FIG. 6, the transmitting RLC entity receives an RLC SDU # 1 705 and an RLC SDU # 2 710 from a higher layer. For convenience of description, the sizes of the RLC SDU # 1 and the RLC SDU # 2 are 13 bytes and 10 bytes, respectively, and the size of the RLC PDU is fixed to 6 bytes.

Then, the sending RLC entity divides the RLC SDU into pieces of a size suitable for a 6-byte RLC PDU, and inserts a serial number (SN) and LI into each piece to complete the RLC PDUs. The serial number is then inserted into every RLC PDU, and LI is only inserted into the RLC PDU containing the last piece of the SDU to indicate the end point of one SDU. That is, the RLC SDU # 1 705 is divided into pieces of 5 bytes, 5 bytes, and 3 bytes, each of which is divided into an RLC PDU # 1 715, an RLC PDU # 2 720, and an RLC PDU # 3 ( 725). In addition, the RLC SDU # 2 710 is divided into pieces of 1 byte, 5 bytes, and 4 bytes, and the pieces are stored in the RLC PDU # 3 725 and the RLC PDU # 4 730, respectively.

As shown in FIG. 6, the last piece of RLC SDU # 1 705 is present in RLC PDU # 3 725, so LI is inserted only in RLC PDU # 3 725. LI indicates that RLC SDU # 1 705 terminates at the third payload byte of RLC PDU # 3 725. The payload means a portion of the RLC PDU except for SN and LI. Serial numbers inserted into the RLC PDU # 1 715, the RLC PDU # 2 720, the RLC PDU # 3 725, and the RLC PDU # 4 730 are monotonically increased by one. The configured RLC PDUs are transmitted to a receiving side RLC through a radio channel.

The receiving RLC entity arranges the RLC PDUs in the sequence rearrangement buffer according to the serial number, and then determines whether each RLC PDU contains LI, so that the third payload of the RLC PDU # 3 725 is determined. Notice that it terminates at the byte. This means that another SDU starts at the fourth payload byte of RLC PDU # 3 725. Therefore, the receiving RLC entity combines the payloads of RLC PDU # 1 715 and the payloads of RLC PDU # 2 720 and the payload 3 bytes of RLC SDU # 3 725, thus providing the original RLC SDU. Assemble # 1 (705). Also, combine the last payload byte of RLC PDU # 3 (725) with the payload of RLC PDU # 4 (730) and the payload 4 bytes of RLC SDU # 5 (not shown). Assemble 2 (710). The receiving RLC entity forwards the completed RLC SDUs 705 and 710 to the higher layer.

In summary, an operation of reconfiguring split or concatenated RLC PDUs into RLC SDUs by a receiving RLC entity is as follows.

1. Arrange received RLC PDUs according to serial number.

2. Identify the start and end points of the RLC SDU from the arranged RLC PDUs.

3. Reconfigure the RLC SDUs to match the start and end points.

The starting point of one RLC SDU is typically the next byte of the end point of the other RLC SDU. Therefore, the receiving RLC entity can identify the end point of one RLC SDU, while identifying the start point of the next RLC SDU. In the example of FIG. 7, the starting point of RLC SDU # 1 is not separately indicated, but since another RLC SDU is terminated in the previous RLC PDU, LI is not inserted into RLC PDU # 1.

To summarize the operation of the OOS delivery entity according to the first embodiment of the present invention once again, the OOS delivery entity distinguishes between RLC PDU_R and RLC PDU_C by using LI and serial numbers as shown in FIG. RLC PDUs corresponding to PDU_R are delivered to the RLC layer. At this time, the RLC PDUs corresponding to RLC PDU_R and RLC PDU_C also have a copy in the reorder buffer so that the RLC SDU other than the reassembled RLC SDU can be reassembled later.

<< 2nd Example >>

FIG. 7 illustrates a structure of a terminal according to a second embodiment of the present invention, and is composed of a physical entity 820, a MAC entity 815, an RLC entity 710, and an RRC entity 805 as shown. . The configuration of the other entities except for the RLC entity 810 is the same as described above. The RLC entity 810 rearranges the order of the RLC PDUs, detects the RLC PDUs for assembling an SDU, and delivers the RLC PDUs to the RRC entity 805 for the purpose of combining the Selective Combining Buffer 840 and the Selective Combiner 845. Use

The SCR buffer 840 stores the RLC PDUs delivered from the MAC entity 815. RLC PDUs that can be assembled into one RLC SDU among the stored RLC PDUs are assembled into RLC SDUs and then delivered to the RRC entity 805. The selective combiner 845 manages RLC PDUs stored in the SCR buffer 840 according to a parameter called an SCR window. The structure of the SCR window is shown in FIG.

As shown in FIG. 8, the SCR window 865 is defined according to the ScrWindow_UpperEdge 850 and the SCR_WINDOW_SIZE 855. The ScrWindow_UpperEdge 850 means the highest serial number of the RLC PDUs received by the UE to the present time. If the serial number of the newly received RLC PDU is larger than the existing value of ScrWindow_UpperEdge, the ScrWindow_UpperEdge is updated with the serial number of the newly received RLC PDU. The initial value of the ScrWindow_UpperEdge 850 is one less than the serial number of the first received RLC PDU.

SCR_WINDOW_SIZE 855 is a parameter set by the RNC and known to UEs and used to prevent infinite retransmission of the RLC PDU. The RNC does not retransmit an RLC PDU having a serial number lower by the SCR_WINDOW_SIZE 855 than the highest number among the serial numbers of the RLC PDU transmitted to the present time. In addition, the UE discards the RLC PDUs having a serial number lower than the SCR_WINDOW_SIZE 855 or more than the highest number among the serial numbers of the RLC PDUs received up to now. Through this operation, the UE does not perform selective combining on the RLC PDU having the same serial number but containing different data.

Then, the SCR window 865 uses the ScrWindow_UpperEdge 850 as the upward endpoint, and modulates (ScrWindow_UpperEdge-SCR_WINDOW_SIZE) to 128 to modulate the value 860 as the downward endpoint. It is a window. Here, the upward direction indicates a direction in which the serial number of the RLC PDU increases as the window progress direction 870. The SCR window 865 increases in the same direction each time the ScrWindow_UpperEdge 850 is updated. When the serial number of the RLC PDU received at some point is located in the SCR window 865, the serial number of the RLC PDU is considered to be smaller than the ScrWindow_UpperEdge 850, and when located outside the SCR window 865, The serial number of the RLC PDU is considered to be greater than ScrWindow_UpperEdge 850.

For example, at some point when ScrWindow_UpperEdge 850 is 100 and SCR_WINDOW_SIZE 855 is 64, the SCR window 865 has an upward endpoint of 100 and a downward endpoint of 36. Subsequently, when an RLC PDU having a serial number of 50 arrives, the serial number 50 is located in the SCR window 865, so the serial number 50 is smaller than 100, which is ScrWindow_UpperEdge. As another example, when an RLC PDU having a serial number of 30 arrives, the serial number 30 is located outside the SCR window 865, so that the serial number 30 is greater than 100, which is ScrWindow_UpperEdge. Therefore, ScrWindow_UpperEdge 850 is updated to 30 and the new downward endpoint of the SCR window 865 is 96, which is -34 calculated as 128 modules. As another example, when the RLC PDU having the serial number 120 arrives, the serial number 120 is located in the SCR window 865, so that the serial number 120 is smaller than the ScrWindow_UpperEdge 850.

As seen above, the optional combiner 845 moves the SCR window 865 with the ScrWindow_UpperEdge 850 being updated, and the serial number of the RLC PDU received according to the receiver SCR window 865 is greater than the ScrWindow_UpperEdge 850. Determine if big or small The SCR buffer 840 stores only RLC PDUs with serial numbers on the SCR window 865. For example, if the SCR window 865 is [downward endpoint = 0, upward endpoint = 64], only the RLC PDUs having serial numbers between 0 and 64 are stored in the SCR buffer 840.

9 is a flowchart illustrating the operation of an RLC entity according to a second embodiment of the present invention.

Referring to FIG. 9, in step 905, the RLC entity receives an RLC PDU whose serial number is SN. In step 907, the RLC entity checks whether the serial number SN is located in the SCR window. If the SN is located in the SCR window, the RLC entity proceeds to step 925. Otherwise, the RLC entity proceeds to step 910.

In step 910, the RLC entity stores the RLC PDU in an SCR buffer. Since the SN is not located in the SCR window means that the SN is larger than ScrWindow_UpperEdge, in step 912 the RLC entity updates the value of ScrWindow_UpperEdge to the SN. In operation 915, the selective combiner updates the SCR window by moving the downward endpoint of the SCR window by the size of the ScrWindow_UpperEdge. For example, if the ScrWindow_UpperEdge is 10 and the SN is 15, the ScrWindow_UpperEdge is moved to 15 by 5. Therefore, the lower endpoint of the SCR window is also moved by five.

In step 917, the optional combiner discards RLC PDUs whose serial number is outside of the new SCR window among RLC PDUs stored in the SCR buffer. For example, when an RLC PDU having a serial number 75 is stored in an SCR buffer, the serial number 75 was located in the SCR-wondow [74 to 10] before the SCR window was moved, but the SCR window [ 79 to 15] outside the SCR window. Therefore, the RLC PDU is discarded. The RLC entity having completed step 917 proceeds to step 950.

In step 950, the RLC entity determines whether RLC SDU assembly is possible using RLC PDUs stored in the SCR buffer. If RLC SDU assembly is not possible with only the RLC PDUs stored in the SCR buffer, the RLC object proceeds to step 995 to terminate the operation and wait until a new RLC PDU arrives. On the other hand, if RLC SDU assembly is possible, the flow proceeds to step 955. In step 955, the RLC entity assembles the RLC SDUs from the RLC PDUs stored in the SCR buffer. In step 960, the RLC entity delivers the assembled RLC SDUs to an upper layer. The RLC entity then proceeds to step 995 to terminate the operation and wait for a new RLC PDU to arrive.

If the SN is included in the SCR window in step 907, the process proceeds to step 925. In step 925, the RLC entity determines whether duplicate RLC PDUs of which the serial number is SN have been received. If the RLC PDU having the serial number SN is already stored in the SCR buffer, the RLC PDU is duplicated and the process proceeds to step 940. If the serial number SN does not store the RLC PDU in the SCR buffer, the RLC PDU is not duplicated and the process proceeds to step 930. In step 940, the RLC entity discards the RLC PDU whose serial number is SN, and proceeds to step 995 to terminate the operation and wait until the next RLC PDU arrives. In step 930, the RLC entity stores an RLC PDU having the serial number SN in an SCR buffer, and proceeds to step 950. That is, it is determined whether RLC SDU assembly is possible including the RLC PDU, and if possible, a new RLC SDU is assembled and delivered to the upper layer. The upper layer extracts an MBMS control message from the RLC SDU to perform an MBMS service.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention has the effect of improving the reception success rate of the MBMS control message and delivering the MBMS control message to the RRC layer as quickly as possible, so that the control operation related to the MBMS can proceed properly.

Claims (7)

In a communication system for dividing or concatenating a control message for a multimedia broadcasting / multicast (MBMS) service into a plurality of data units and assigning serial numbers to the data units, the terminal receives the data units and transmits the control message. In the method for receiving, Receiving a plurality of data units including at least one control message and each having a serial number and storing the received data units in order according to the serial number; Determining whether there are first data units that can be assembled into a first control message among the stored data units; If the first data units exist, determining whether there is at least one second data unit that can be assembled into a second control message among the stored data units; If the second data unit exists, copying the second data unit and storing the copied second data unit again; Assembling the first data units other than the copied second data unit to form a control message, Receiving method characterized in that the same data units have the same serial number regardless of the transmission time. The method of claim 1, wherein the first data units, And a first data unit and a last data unit of the first control message, wherein the data units have consecutive serial numbers. The receiving method of claim 1, wherein the data units including the end point of the corresponding control message among the stored data units further include a length indicator indicating the end point of the corresponding control message in bytes. In a communication system for dividing or concatenating a control message for a multimedia broadcasting / multicast (MBMS) service into a plurality of data units and assigning serial numbers to the data units, the terminal receives the data units and transmits the control message. In the method for receiving, When receiving a data unit including at least a part of a control message and having a predetermined serial number, checking whether the serial number of the data unit is included in a predetermined window; Storing the data unit in a buffer if the serial number is not included in the window; Determining whether a data unit having the serial number is already stored in the buffer when the serial number is included in the window; If the data unit having the serial number is not already stored, storing the data unit in the buffer; Determining whether there are first data units that can be assembled into a first control message among the stored data units; If the first data units exist, assembling the first data units to form the first control message; Receiving method characterized in that the same data units have the same serial number regardless of the transmission time. The method of claim 4, further comprising: updating the window according to the serial number if the serial number is not included in the window, and discarding data units not included in the updated window in the buffer. A reception method characterized by the above. The method of claim 4, wherein the window, And having the highest serial number of the serial numbers of the last received data units as the upward endpoint, and having a window size set by the system to prevent infinite retransmission of the data units. The method of claim 6, wherein the window, And a value obtained by modulo operation of the difference between the upper end point and the window size as 128 as the lower end point.

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