KR20200143127A - Apparatus and method of Delay-based HARQ procedure control in NR NTN - Google Patents

Abstract

The present disclosure provides a method for controlling a delay-based HARQ procedure in an NR non-terrestrial network. More particularly, the present disclosure provides a method for providing a HARQ operation for a terminal serviced through a non-terrestrial network by applying a flexible HARQ process number considering a propagation delay between a satellite and the terminal.

Description

Delay-based HARQ procedure control method and apparatus in NR non-ground network {Apparatus and method of Delay-based HARQ procedure control in NR NTN}

The present invention relates to a method and apparatus for controlling a HARQ procedure in consideration of propagation delay between satellites and terminals for 5G NR-based non-terrestrial network communication.

In one embodiment, in a method for controlling a delay-based HARQ procedure in an NR non-terrestrial network, HARQ by applying a flexible HARQ process number considering a propagation delay between a satellite and a terminal for a terminal serviced through a non-ground network. Provides a way to provide behavior.

1 is a diagram schematically illustrating a structure of an NR wireless communication system to which the present embodiment can be applied.
2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.
3 is a diagram illustrating a resource grid supported by a radio access technology to which the present embodiment can be applied.
4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.
5 is a diagram illustrating a synchronization signal block in a wireless access technology to which the present embodiment can be applied.
6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.
7 is a diagram for explaining CORESET.
8 is a diagram illustrating an example of symbol level alignment for different SCSs to which the present embodiment can be applied.
9 is a diagram showing an overview of an NR MAC structure to which this embodiment can be applied.
10 is a diagram showing an example of a typical NTN scenario to which the present embodiment can be applied.
11 is a diagram showing a type of NTN platform to which this embodiment can be applied.
12 is a diagram showing a configuration of a base station according to another embodiment.
13 is a diagram showing a configuration of a user terminal according to another embodiment.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. In adding reference numerals to elements of each drawing, the same elements may have the same numerals as possible even if they are indicated on different drawings. In addition, in describing the embodiments, when it is determined that a detailed description of a related known configuration or function may obscure the gist of the present technical idea, the detailed description may be omitted. When "include", "have", "consists of" and the like mentioned in the present specification are used, other parts may be added unless "only" is used. In the case of expressing the constituent elements in the singular, the case including plural may be included unless there is a specific explicit description.

In addition, in describing the constituent elements of the present disclosure, terms such as first, second, A, B, (a) and (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, order, or number of the component is not limited by the term.

In the description of the positional relationship of the components, when two or more components are described as being "connected", "coupled" or "connected", the two or more components are directly "connected", "coupled" or "connected" ", but it will be understood that two or more components and other components may be further "interposed" to be "connected", "coupled" or "connected". Here, the other components may be included in one or more of two or more components "connected", "coupled" or "connected" to each other.

In the description of the temporal flow relationship related to the components, the operation method or the manufacturing method, for example, the temporal predecessor relationship such as "after", "after", "after", "before", etc. Alternatively, a case where a flow forward and backward relationship is described may also include a case that is not continuous unless "direct" or "direct" is used.

On the other hand, when a numerical value for a component or its corresponding information (e.g., level, etc.) is mentioned, the numerical value or its corresponding information is related to various factors (e.g., process factors, internal or external impacts, etc.) It can be interpreted as including an error range that may be caused by noise, etc.).

The wireless communication system in the present specification refers to a system for providing various communication services such as voice and data packets using radio resources, and may include a terminal, a base station, or a core network.

The embodiments disclosed below can be applied to a wireless communication system using various wireless access technologies. For example, the present embodiments include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA). Alternatively, it may be applied to various various wireless access technologies such as non-orthogonal multiple access (NOMA). In addition, the wireless access technology may mean not only a specific access technology, but also a communication technology for each generation established by various communication consultation organizations such as 3GPP, 3GPP2, WiFi, Bluetooth, IEEE, and ITU. For example, CDMA may be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with a radio technology such as global system for mobile communications (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented with a wireless technology such as IEEE (institute of electrical and electronics engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (evolved UTRA), and the like. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with a system based on IEEE 802.16e. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA), and employs OFDMA in downlink and SC- in uplink. Adopt FDMA. As described above, the present embodiments may be applied to a wireless access technology currently disclosed or commercialized, and may be applied to a wireless access technology currently being developed or to be developed in the future.

Meanwhile, a terminal in the present specification is a generic concept that refers to a device including a wireless communication module that performs communication with a base station in a wireless communication system, and is used in WCDMA, LTE, NR, HSPA, and IMT-2020 (5G or New Radio). It should be interpreted as a concept that includes all of the UE (User Equipment) of, as well as the MS (Mobile Station), UT (User Terminal), SS (Subscriber Station), and wireless device in GSM. In addition, the terminal may be a user's portable device such as a smart phone according to the usage type, and in the V2X communication system, it may mean a vehicle, a device including a wireless communication module in the vehicle, and the like. In addition, in the case of a machine type communication system, it may mean an MTC terminal, an M2M terminal, a URLLC terminal, etc. equipped with a communication module so that machine type communication is performed.

The base station or cell of the present specification refers to the end of communication with the terminal in terms of the network, and Node-B (Node-B), eNB (evolved Node-B), gNB (gNode-B), LPN (Low Power Node), Sector, Site, various types of antennas, BTS (Base Transceiver System), Access Point, Point (e.g., Transmit Point, Receiving Point, Transmitting Point), Relay Node ), a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, a remote radio head (RRH), a radio unit (RU), and a small cell. Also, the cell may mean including a bandwidth part (BWP) in the frequency domain. For example, the serving cell may mean an activation BWP of the terminal.

In the various cells listed above, since there is a base station controlling one or more cells, the base station can be interpreted in two ways. 1) In relation to the radio area, the device itself may provide a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, and a small cell, or 2) the radio area itself may be indicated. In 1), all devices that are controlled by the same entity that provide a predetermined wireless area are controlled by the same entity, or all devices that interact to form a wireless area in collaboration are instructed to the base station. A point, a transmission/reception point, a transmission point, a reception point, etc. may be an embodiment of a base station according to the configuration method of the wireless area. In 2), it is also possible to instruct the base station to the radio region itself to receive or transmit a signal from the viewpoint of the user terminal or the viewpoint of a neighboring base station.

In the present specification, a cell refers to a component carrier having coverage of a signal transmitted from a transmission/reception point or a coverage of a signal transmitted from a transmission/reception point, and the transmission/reception point itself. I can.

Uplink (Uplink, UL, or uplink) refers to a method of transmitting and receiving data to a base station by a UE, and downlink (Downlink, DL, or downlink) refers to a method of transmitting and receiving data to a UE by a base station. do. Downlink may refer to a communication or communication path from multiple transmission/reception points to a terminal, and uplink may refer to a communication or communication path from a terminal to multiple transmission/reception points. In this case, in the downlink, the transmitter may be a part of the multiple transmission/reception points, and the receiver may be a part of the terminal. In addition, in the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of the multiple transmission/reception points.

Uplink and downlink transmit and receive control information through a control channel such as Physical Downlink Control CHannel (PDCCH), Physical Uplink Control CHannel (PUCCH), and the like, and The same data channel is configured to transmit and receive data. Hereinafter, a situation in which signals are transmitted and received through channels such as PUCCH, PUSCH, PDCCH, and PDSCH is expressed in the form of'transmitting and receiving PUCCH, PUSCH, PDCCH and PDSCH'. do.

In order to clarify the description, hereinafter, the present technical idea is mainly described with a 3GPP LTE/LTE-A/NR (New RAT) communication system, but the present technical feature is not limited to the corresponding communication system.

3GPP develops 5G (5th-Generation) communication technology to meet the requirements of ITU-R's next-generation wireless access technology after research on 4G (4th-Generation) communication technology. Specifically, 3GPP develops a new NR communication technology separate from 4G communication technology and LTE-A pro, which has improved LTE-Advanced technology as a 5G communication technology to meet the requirements of ITU-R. Both LTE-A pro and NR refer to 5G communication technology. Hereinafter, 5G communication technology will be described centering on NR when a specific communication technology is not specified.

The operation scenario in NR defined various operation scenarios by adding considerations to satellites, automobiles, and new verticals from the existing 4G LTE scenario.In terms of service, eMBB (Enhanced Mobile Broadband) scenario, high terminal density, but wide It is deployed in the range and supports the mMTC (Massive Machine Communication) scenario that requires a low data rate and asynchronous connection, and the URLLC (Ultra Reliability and Low Latency) scenario that requires high responsiveness and reliability and supports high-speed mobility. .

In order to satisfy this scenario, NR discloses a wireless communication system to which a new waveform and frame structure technology, a low latency technology, a mmWave support technology, and a forward compatible provision technology are applied. In particular, in the NR system, various technological changes are proposed in terms of flexibility to provide forward compatibility. The main technical features of the NR will be described below with reference to the drawings.

<NR system general>

1 is a diagram schematically showing a structure of an NR system to which this embodiment can be applied.

1, the NR system is divided into 5GC (5G Core Network) and NR-RAN parts, and NG-RAN controls user plane (SDAP/PDCP/RLC/MAC/PHY) and UE (User Equipment). It is composed of gNB and ng-eNB that provide plane (RRC) protocol termination. The gNB or gNB and ng-eNB are interconnected through an Xn interface. The gNB and ng-eNB are each connected to 5GC through the NG interface. The 5GC may include an Access and Mobility Management Function (AMF) in charge of a control plane such as a terminal access and mobility control function, and a User Plane Function (UPF) in charge of a control function for user data. NR includes support for both frequency bands below 6GHz (FR1, Frequency Range 1) and frequencies above 6GHz (FR2, Frequency Range 2).

gNB means a base station that provides NR user plane and control plane protocol termination to a terminal, and ng-eNB means a base station that provides E-UTRA user plane and control plane protocol termination to a terminal. The base station described in the present specification should be understood in a sense encompassing gNB and ng-eNB, and may be used as a means to distinguish between gNB or ng-eNB as necessary.

<NR wave form, numer roller and frame structure>

In NR, a CP-OFDM waveform using a cyclic prefix is used for downlink transmission, and CP-OFDM or DFT-s-OFDM is used for uplink transmission. OFDM technology is easy to combine with MIMO (Multiple Input Multiple Output), and has the advantage of being able to use a low complexity receiver with high frequency efficiency.

On the other hand, in NR, since the requirements for data rate, delay rate, and coverage are different for each of the three scenarios described above, it is necessary to efficiently satisfy the requirements for each scenario through a frequency band constituting an arbitrary NR system. . To this end, a technique for efficiently multiplexing a plurality of different numerology-based radio resources has been proposed.

값이 2의 지수 값으로 사용되어 지수적으로 변경된다.Specifically, the NR transmission neuron is determined based on sub-carrier spacing and CP (Cyclic prefix), and is based on 15khz as shown in Table 1 below.

The value is used as an exponent of 2 and changes exponentially.

Subcarrier spacing Cyclic prefix Supported for data Supported for synch 0 15 Normal Yes Yes One 30 Normal Yes Yes 2 60 Normal, Extended Yes No 3 120 Normal Yes Yes 4 240 Normal No Yes

As shown in Table 1 above, the NR neuron can be classified into 5 types according to the subcarrier interval. This is different from the fixed subcarrier spacing of 15khz of LTE, one of the 4G communication technologies. Specifically, subcarrier intervals used for data transmission in NR are 15, 30, 60, and 120khz, and subcarrier intervals used for synchronization signal transmission are 15, 30, 12, and 240khz. In addition, the extended CP is applied only to the 60khz subcarrier interval. On the other hand, a frame structure in NR is defined as a frame having a length of 10 ms consisting of 10 subframes having the same length of 1 ms. One frame can be divided into 5 ms half frames, and each half frame includes 5 subframes. In the case of the 15khz subcarrier interval, one subframe consists of 1 slot, and each slot consists of 14 OFDM symbols.

2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.

Referring to FIG. 2, in the case of a normal CP, a slot is fixedly composed of 14 OFDM symbols, but the length in the time domain of the slot may vary according to the subcarrier interval. For example, in the case of a newer roller having a 15khz subcarrier interval, a slot is 1ms long and has the same length as the subframe. In contrast, in the case of a newer roller with a 30khz subcarrier spacing, a slot consists of 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5ms. That is, the subframe and the frame are defined with a fixed time length, and the slot is defined by the number of symbols, and the time length may vary according to the subcarrier interval.

Meanwhile, NR defines a basic unit of scheduling as a slot, and introduces a mini-slot (or sub-slot or non-slot based schedule) in order to reduce the transmission delay of the radio section. If a wide subcarrier spacing is used, the length of one slot is shortened in inverse proportion, so that transmission delay in the radio section can be reduced. The mini-slot (or sub-slot) is for efficient support for the URLLC scenario, and scheduling is possible in units of 2, 4, or 7 symbols.

In addition, unlike LTE, NR defines uplink and downlink resource allocation as a symbol level within one slot. In order to reduce HARQ delay, a slot structure capable of transmitting HARQ ACK/NACK directly within a transmission slot has been defined, and this slot structure is named and described as a self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slot formats are used in 3GPP Rel-15. In addition, a common frame structure constituting an FDD or TDD frame is supported through a combination of various slots. For example, a slot structure in which all symbols of a slot are set to downlink, a slot structure in which all symbols are set to uplink, and a slot structure in which a downlink symbol and an uplink symbol are combined are supported. In addition, NR supports that data transmission is distributed and scheduled in one or more slots. Accordingly, the base station may inform the UE of whether the slot is a downlink slot, an uplink slot, or a flexible slot using a slot format indicator (SFI). The base station can indicate the slot format by indicating the index of the table configured through UE-specific RRC signaling using SFI, and dynamically indicates through Downlink Control Information (DCI) or statically or through RRC. It can also be quasi-static.

<NR physical resource>

Regarding the physical resource in NR, the antenna port, resource grid, resource element, resource block, bandwidth part, etc. are considered. do.

The antenna port is defined so that a channel carrying a symbol on an antenna port can be inferred from a channel carrying another symbol on the same antenna port. When the large-scale property of a channel carrying a symbol on one antenna port can be inferred from a channel carrying a symbol on another antenna port, the two antenna ports are QC/QCL (quasi co-located or quasi co-location) relationship. Here, the wide-range characteristic includes at least one of delay spread, Doppler spread, frequency shift, average received power, and received timing.

3 is a diagram illustrating a resource grid supported by a radio access technology to which the present embodiment can be applied.

Referring to FIG. 3, since the NR supports a plurality of neurons in the same carrier, a resource grid may exist according to each neuron in the resource grid. In addition, the resource grid may exist according to an antenna port, a subcarrier spacing, and a transmission direction.

A resource block consists of 12 subcarriers, and is defined only in the frequency domain. In addition, a resource element consists of one OFDM symbol and one subcarrier. Accordingly, as shown in FIG. 3, the size of one resource block may vary according to the subcarrier interval. In addition, NR defines “Point A” that serves as a common reference point for the resource block grid, a common resource block, and a virtual resource block.

4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.

In NR, unlike LTE where the carrier bandwidth is fixed at 20Mhz, the maximum carrier bandwidth is set from 50Mhz to 400Mhz for each subcarrier interval. Therefore, it is not assumed that all terminals use all of these carrier bandwidths. Accordingly, in the NR, as shown in FIG. 4, a bandwidth part (BWP) can be designated within the carrier bandwidth and used by the terminal. In addition, the bandwidth part is associated with one neurology and is composed of a subset of consecutive common resource blocks, and can be dynamically activated over time. The UE is configured with up to four bandwidth parts, respectively, in uplink and downlink, and data is transmitted and received using the active bandwidth part at a given time.

In the case of a paired spectrum, uplink and downlink bandwidth parts are independently set, and in the case of an unpaired spectrum, unnecessary frequency re-tuning between downlink and uplink operations is prevented. For this purpose, the downlink and uplink bandwidth parts are set in pairs to share a center frequency.

<NR initial connection>

In NR, the terminal accesses the base station and performs cell search and random access procedures to perform communication.

Cell search is a procedure in which a terminal synchronizes with a cell of a corresponding base station, obtains a physical layer cell ID, and obtains system information by using a synchronization signal block (SSB) transmitted by a base station.

5 is a diagram illustrating a synchronization signal block in a wireless access technology to which the present embodiment can be applied.

Referring to FIG. 5, an SSB consists of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) occupying 1 symbol and 127 subcarriers, respectively, and a PBCH spanning 3 OFDM symbols and 240 subcarriers.

The terminal receives the SSB by monitoring the SSB in the time and frequency domain.

SSB can be transmitted up to 64 times in 5ms. A plurality of SSBs are transmitted in different transmission beams within 5 ms time, and the UE performs detection on the assumption that SSBs are transmitted every 20 ms period based on one specific beam used for transmission. The number of beams that can be used for SSB transmission within 5 ms time may increase as the frequency band increases. For example, up to 4 SSB beams can be transmitted under 3GHz, and up to 8 in a frequency band of 3 to 6GHz, and a maximum of 64 different beams in a frequency band of 6GHz or higher can be used to transmit SSBs.

Two SSBs are included in one slot, and the start symbol and the number of repetitions in the slot are determined according to the subcarrier interval as follows.

Meanwhile, the SSB is not transmitted at the center frequency of the carrier bandwidth, unlike the conventional LTE SS. That is, the SSB may be transmitted even in a place other than the center of the system band, and a plurality of SSBs may be transmitted in the frequency domain when broadband operation is supported. Accordingly, the UE monitors the SSB by using a synchronization raster, which is a candidate frequency location for monitoring the SSB. The carrier raster and synchronization raster, which are information on the center frequency of the channel for initial access, have been newly defined in NR, and the synchronization raster has a wider frequency interval than the carrier raster to support fast SSB search of the terminal. I can.

The UE can acquire the MIB through the PBCH of the SSB. The MIB (Master Information Block) includes minimum information for the terminal to receive remaining system information (RMSI, Remaining Minimum System Information) broadcast by the network. In addition, PBCH is information about the location of the first DM-RS symbol in the time domain, information for the UE to monitor SIB1 (e.g., SIB1 neurology information, information related to SIB1 CORESET, search space information, PDCCH Related parameter information, etc.), offset information between the common resource block and the SSB (the position of the absolute SSB in the carrier is transmitted through SIB1), and the like. Here, the SIB1 neurology information is equally applied to some messages used in the random access procedure for accessing the base station after the terminal completes the cell search procedure. For example, the neurology information of SIB1 may be applied to at least one of messages 1 to 4 for a random access procedure.

The aforementioned RMSI may mean System Information Block 1 (SIB1), and SIB1 is periodically broadcast (ex, 160ms) in a cell. SIB1 includes information necessary for the UE to perform an initial random access procedure, and is periodically transmitted through the PDSCH. In order for the UE to receive SIB1, it is necessary to receive newer roller information used for SIB1 transmission and CORESET (Control Resource Set) information used for SIB1 scheduling through the PBCH. The UE checks scheduling information for SIB1 using SI-RNTI in CORESET, and acquires SIB1 on the PDSCH according to the scheduling information. SIBs other than SIB1 may be periodically transmitted or may be transmitted according to the request of the terminal.

6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 6, when the cell search is completed, the UE transmits a random access preamble for random access to the base station. The random access preamble is transmitted through the PRACH. Specifically, the random access preamble is transmitted to the base station through a PRACH consisting of consecutive radio resources in a specific slot that is periodically repeated. In general, when a terminal initially accesses a cell, a contention-based random access procedure is performed, and when a random access is performed for beam failure recovery (BFR), a contention-free random access procedure is performed.

The terminal receives a random access response to the transmitted random access preamble. The random access response may include a random access preamble identifier (ID), a UL Grant (uplink radio resource), a temporary C-RNTI (Temporary Cell-Radio Network Temporary Identifier), and a TAC (Time Alignment Command). Since one random access response may include random access response information for one or more terminals, the random access preamble identifier may be included to inform which terminal the included UL Grant, temporary C-RNTI, and TAC are valid. The random access preamble identifier may be an identifier for the random access preamble received by the base station. TAC may be included as information for the UE to adjust uplink synchronization. The random access response may be indicated by a random access identifier on the PDCCH, that is, a Random Access-Radio Network Temporary Identifier (RA-RNTI).

Upon receiving a valid random access response, the terminal processes information included in the random access response and performs scheduled transmission to the base station. For example, the UE applies TAC and stores a temporary C-RNTI. Also, by using UL Grant, data stored in the buffer of the terminal or newly generated data is transmitted to the base station. In this case, information for identifying the terminal should be included.

Finally, the terminal receives a downlink message for resolving contention.

<NR CORESET>

The downlink control channel in NR is transmitted in CORESET (Control Resource Set) having a length of 1 to 3 symbols, and transmits uplink/downlink scheduling information, SFI (Slot Format Index), and TPC (Transmit Power Control) information. .

In this way, NR introduced the concept of CORESET to secure system flexibility. CORESET (Control Resource Set) means a time-frequency resource for a downlink control signal. The terminal may decode the control channel candidate using one or more search spaces in the CORESET time-frequency resource. A QCL (Quasi CoLocation) assumption for each CORESET is set, and this is used to inform the characteristics of the analog beam direction in addition to the delay spread, Doppler spread, Doppler shift, and average delay, which are characteristics assumed by conventional QCL.

7 is a diagram for explaining CORESET.

Referring to FIG. 7, CORESET may exist in various forms within a carrier bandwidth within one slot, and CORESET may consist of up to 3 OFDM symbols in the time domain. In addition, CORESET is defined as a multiple of 6 resource blocks up to the carrier bandwidth in the frequency domain.

The first CORESET is indicated through the MIB as part of the initial bandwidth part configuration so that additional configuration information and system information can be received from the network. After establishing the connection with the base station, the terminal may receive and configure one or more CORESET information through RRC signaling.

In this specification, frequencies, frames, subframes, resources, resource blocks, regions, bands, subbands, control channels, data channels, synchronization signals, various reference signals, various signals, or various messages related to NR (New Radio) Can be interpreted as a meaning used in the past or present, or in various meanings used in the future.

New Radio (NR)

NR progressed in 3GPP is a radio access technology capable of satisfying various QoS requirements required for each subdivided and specified usage scenario as well as an improved data rate compared to LTE. In particular, eMBB (enhancement Mobile BroadBand), mMTC (massive MTC), and URLLC (Ultra Reliable and Low Latency Communications) are defined as representative usage scenarios of NR. structure is provided. The frame structure of NR supports a frame structure based on multiple subcarriers. The basic SCS is 15kHz, and a total of 5 SCS types are supported at 15kHz*2 ^μ . 8 shows an example of symbol level alignment for different SCSs. As shown in FIG. 8, it can be seen that the slot length varies according to numerology. That is, it can be seen that the shorter the slot length, the larger the SCS. In addition, the number of OFDM symbols constituting a slot in the NR, y value, was determined to have a value of y=14 regardless of the SCS value in the case of normal CP. Accordingly, a random slot consists of 14 symbols, and according to the transmission direction of the corresponding slot, all symbols are used for DL transmission, or all symbols are used for UL transmission, or DL portion + (gap) + It can be used in the form of a UL portion. In addition, a mini-slot consisting of fewer symbols than the slot is defined in an arbitrary numerology (or SCS), and based on this, a short time-domain scheduling interval for uplink/downlink data transmission/reception is set, or slot aggregation A long time-domain scheduling interval for transmitting/receiving uplink/downlink data may be configured through. In particular, in the case of transmission and reception of latency critical data such as URLLC, it is difficult to satisfy the latency requirement when scheduling is performed in slot units based on 1ms (14 symbols) defined in a numerology-based frame structure with a small SCS value such as 15kHz Therefore, for this purpose, a mini-slot consisting of fewer OFDM symbols than the corresponding slot can be defined, and based on this, it can be defined to perform scheduling for latency critical data such as the corresponding URLLC.

NR supports the following structure in the time axis. Here, the difference from existing LTE is that in NR, the basic scheduling unit is changed to a slot. Also, regardless of subcarrier-spacing, a slot consists of 14 OFDM symbols. On the other hand, it supports a non-slot structure composed of 2, 4, 7 OFDM symbols, which are smaller scheduling units. The non-slot structure can be used as a scheduling unit for URLLC service.

NR HARQ (Hybrid ARQ)

The MAC protocol performs an error correction function through HARQ. 9 shows an example of a MAC structure. For NR, Asynchronous Incremental Redundancy Hybrid ARQ is supported in downlink transmission. The base station may provide the HARQ-ACK feedback timing to the terminal dynamically within DCI or semi-statically in an RRC configuration. The MAC entity includes one HARQ entity for each serving cell, and each HARQ entity maintains 16 downlink HARQ processes. In NR, Asynchronous Incremental Redundancy Hybrid ARQ is supported in uplink transmission. The base station schedules uplink transmission and retransmission using the uplink grant on the DCI. The MAC entity includes one HARQ entity for each serving cell, and each HARQ entity maintains 16 uplink HARQ processes.

Non-Terrestrial Network (NTN)

A non-terrestrial network refers to a network or a segment of a network using RF resources mounted on a satellite (or an Unmanned Aircraft System platform (UAS)). FIG. 10 shows an example of a typical NTN scenario.

NTN can be implemented in various ways as follows.

-Scenario A: Transparent GEO (NTN beam foot print fixed on earth)

-Scenario B: Regenerative GEO (NTN beam foot print fixed on earth)

-Scenario C1: Transparent LEO (NTN beam foot print fixed on earth)

-Scenario C2: Transparent LEO (NTN beam foot print moving on earth)

-Scenario D1: Regenerative LEO (NTN beam foot print fixed on earth)

-Scenario D2: Regenerative LEO (NTN beam foot print moving on earth)

Here, transparent payload or regenerative payload is defined as follows.

-A transparent payload: Radio Frequency filtering, Frequency conversion and amplification. Hence, the waveform signal repeated by the payload is un-changed;

-A regenerative payload: Radio Frequency filtering, Frequency conversion and amplification as well as demodulation/decoding, switch and/or routing, coding/modulation. This is effectively equivalent to having all or part of base station functions (e.g. gNB) on board the satellite (or UAS platform).

The satellite (or UAS platform) generate beams typically generate several beams over a given service area, the satellite generated beams are bounded by the field of view of the satellite. bounded by its field of view.) The beam's footprint is typically elliptical. 11 shows the type of NTN platform and the footprint size of a typical beam.

Due to the distance between the terminal and the satellite, when the NTN provides the HARQ procedure of the NR as it is, for example, when the HARQ operation is performed through 16 parallel HARQ processes provided by the NR, the packet is transmitted in the error correction process through HARQ. This can lead to HARQ stalling. However, in order to increase the number of HARQ processes, it is difficult to increase the number of HARQ processes because an additional cost is required for the terminal. In addition, the base station transmits the HARQ process ID to the terminal through the DCI. In order to identify the increased HARQ process ID, there is a problem in that more bits must be allocated to the DCI to distinguish the HARQ process ID.

When the NTN provides the HARQ procedure of the NR as it is, packet transmission may be delayed due to the limited parallel HARQ process in the error correction process through HARQ due to propagation delay between the terminal and the satellite, thereby significantly reducing the data rate. In addition, when the number of HARQ processes to be parallel processed is increased, there is a problem in that more bits must be allocated to DCI in order to distinguish HARQ process IDs.

The present invention, conceived to solve the above problem, proposes a method and apparatus for efficiently providing HARQ operation through a non-ground network.

Hereinafter, a method of controlling HARQ based on NR radio access technology will be described. However, this is for convenience of description, and the present invention may be applied to any wireless access technology. Although the present invention relates to a HARQ control method through a non-ground network, the present invention can be applied to HARQ control over a terrestrial network or through an interface between a terminal and a terminal (e.g. PC5). The embodiments described in the present invention include the contents of information elements and operations specified in TS 38.321, which is an NR MAC standard, and TS 38.213, which is an NR physical layer control standard. Even if the contents of the terminal operation related to the definition of the corresponding information element are not included in the present specification, the contents specified in the standard specification, which is a known technique, may be included in the present invention. The embodiments provided below may be implemented individually or by arbitrarily combining/combining each of the embodiments.

As described above, due to the limited number of HARQ processes, the application of HARQ becomes difficult as the distance between the terminal and the satellite such as GEO or MEO increases. Therefore, it is possible to disable the HARQ process. For convenience of description, not operating the HARQ process is indicated as HARQ turn off. This is for convenience of description, and may be replaced with an arbitrary function name that may be caused by not operating HARQ such as HARQ disable, HARQ deactivation, no Uplink HARQ feedback, and HARQ feedback disable in the terminal for downlink transmission.

On the other hand, in the case of the UAS platform and LEO, the HARQ delay may not be large. In addition, HARQ has the advantage of a soft combining gain. Therefore, even in the case of NTN, there is a case where it is desirable to operate (enable/turn on/uplink HARQ feedback) the HARQ process.

To this end, it is necessary for the base station to configure HARQ turn off/turn on in the terminal, and it is necessary to additionally define a terminal operation corresponding thereto.

At the current RAN1#97 meeting, it was decided to support the following items first in the NR NTN Study Item.

Agreement:

Network disabling of HARQ via RRC configuration should be supported.

· FFS: Dynamic disabling of HARQ by gNB.

Agreement:

Evaluate impact of Satellite RTT when HARQ is enabled and potential solutions if needed

· At least the following aspects should be considered if the number of HARQ processes is> 16:

o DCI size

o HARQ soft buffer size

In this proposal, a method of considering the propagation delay between satellites and terminals in consideration of the DCI size for the increase in the number of HARQ processes currently considered is described.

Method 1. An additional HARQ process number field is allocated in consideration of the delay time of the satellite and the terminal.

As mentioned above, NR NTN supports communication between satellites and terrestrial terminals.

Currently, NR is conducting simulation by considering various satellite orbits, and among them, specific simulation parameters have been defined for three cases as follows.

For reference, a method of deriving the number of _{HARQ processes} N _HARQ for subcarrier spacing = 15 kHz of LTE/NR is as follows.

N _HARQ =

-T _p : 2Tp is required considering propagation delay and RTT.

-T _slot : Slot transmission time (15kHz standard, 1ms)

-T _UEP : UE data processing time after PDCCH and PDSCH reception

-T _ack : Transmission time of A/N

-T _gNBP : gNB data processing time after A/N reception

In LTE/NR SCS=15kHz, the following values can be derived basically. If the distance between the terminal and the base station is negligibly small or falls within the CP, the propagation delay T _p becomes 0. Also

In addition, a single subframe/slot is 1 ms, and the processing time of the terminal and the base station is usually set to 3 ms or less. Also, assuming that PUCCH for Ack/Nack transmission is also transmitted in slot units, it is 1ms. Therefore, when the HARQ process number is derived based on SCS=15kHz LTE/NR per Transport Block (TB), it is as follows.

=8 per TBN _HARQ =

=8 per TB

Therefore, a 3-bit field for each TB is included in the DCI to refer to the HARQ process number. Using the same principle, if the propagation delay between the satellite and the terminal located in the satellite orbits LEO-600, LEO-1200, and GEO is calculated, it becomes 2ms, 4ms, and 120ms, respectively, and the HARQ process number in each case is calculated as follows.

= 12 per TBLEO-600 standard N _HARQ =

= 12 per TB

= 16 per TBLEO-1200 standard N _HARQ =

= 16 per TB

= 248 per TBGEO criterion N _HARQ =

= 248 per TB

A required HARQ process number can be derived through a delay according to the satellite orbit of the terminal. Therefore, when considering the propagation delay between satellites and terminals, the number of HARQ processes needs to increase from 8 (=3 bits) per existing TB to a specific bit or more. Since HARQ cannot be applied to the number of HARQ processes having a too large size, it can be assumed that the HARQ on/off technique is applied. However, as in the case of LEO-600,1200, it is possible to expand and operate the HARQ chain sufficiently by only adding relatively few'N' bits.

Therefore, in this proposal, we propose a flexible HARQ process number application scheme that considers propagation delay between satellites and terminals. To achieve this, the change of the HARQ process number must be signaled to the terminal first, or a predefined configuration must be followed in a predefined way.

When the propagation delay between the satellite and the terminal exceeds the maximum allowable value supported by the existing timing advance, it is necessary to additionally specify the number of HARQ processes. To this end, as mentioned above, a method for a satellite base station to refer to a terminal and a method for a satellite and a base station to follow preset values are required.

● Alt.1: Refers to information on the number of additional HARQ processes to the terminal

√ The base station signals the number of HARQ processes currently being operated to the terminal. That is, information on how many HARQ processes 8 per TB have been changed is delivered based on information estimated through propagation delay between satellites and base stations. When accurate information on the number is provided to the terminal, the terminal can divide the soft buffer and map 1:1 to the number of HARQ processes. Corresponding information may be directly signaled to the UE through RRC, and dynamic signaling through DCI may be applied in some cases.

● Alt.2: Indirect designation through existing system information delivered to the terminal

√ The satellite base station may transmit the corresponding information to the terminal using information previously provided without performing additional signaling on the number of HARQ processes added to the terminal. For example, information such as a timing advance value applied during uplink transmission may be used. When the maximum range of the TA value exceeds the range supported by the existing NR standard, a new range value for NTN is applied. Based on this range of values, the UE can derive the number of corresponding HARQ processes, and directly applies the calculated number of HARQ processes to data transmission of PDSCH/PUSCH. For example, the TA value can be converted directly into the transmission delay time, and the range of the number of HARQ processes can be predefined in the form of the following table using this value. For reference, TA means round trip time (RTT), and half of the value corresponds to one way propagation delay.

In this proposal, it is assumed that the soft buffer of the terminal is also increased so that the number of HARQ processes can be increased, or a situation in which the number of HARQ processes does not increase is not restricted by securing a sufficient soft buffer from the viewpoint of the terminal. If the soft buffer of the terminal follows only the category defined in the existing NR spec., the size of the TB that the terminal can transmit and receive at one time may be limited. Therefore, in this case, it is possible to apply a method of lowering the resource allocation size that can be transmitted to the terminal and transmitting.

Hereinafter, a signaling configuration method for referring to a flexible HARQ process in consideration of propagation delay between satellites and terminals is proposed.

The number of HARQ processes described in this proposal is a number described as an example, and it is not excluded that the NR system can operate 4 bits per TB.

Option 1-1. In adding the HARQ process field, other fields in DCI are used exclusively and the entire DCI size is maintained.

This proposal proposes a method of maintaining the existing DCI size as it is in a method of flexibly applying the number of HARQ processes based on the aforementioned propagation delay between satellites and terminals. That is, the UE maintains the number of blind decoding for PDCCH detection or reuses the existing DCI format without defining a new DCI format. To this end, some of the other fields in the existing DCI field should be used to refer to the HARQ process. Basically, you can think of only redundancy version field (RV field). For satellite-to-terminal transmission, where propagation delay is long, even if a retransmission error occurs, a soft value combining effect can be maintained to the maximum by applying a specific RV pattern. For example, according to the RV field definition of TS 38.212, there are a total of 4 types, and can be referred to as 2 bits in DCI.

In this proposal, it means that a part or all of the RV field is used exclusively to refer to the flexible HARQ process. For example, if the RV field is limited to 1 bit, the remaining 1 bit may be additionally used to refer to the HARQ process. In this case, since the HARQ process can be referred to as 5 bits per TB based on NR, up to 32 HARQ processes can be referred to. In a similar way, the RV field can be set to 0 bit. In this case, the RV value defined in advance through RRC is used as a default. When the RV field is modified to 1 bit, a specific set can be set as RRC in advance and used. {0,1},{0,2},{0,3},{1,2}, {1,3} , {2,3} can be selected and defined. In addition, the RV field value may not be used at all. In this case, all 2 bits of the RV field may be used to refer to the HARQ process, and the RV value follows a value defined as higher layer signaling.

In addition, some of the resource allocation field or DMRS allocation field may be dedicated to the DCI. In this case, the flexibility of the field decreases, but the DCI size does not change, so the blind decoding complexity of the terminal is maintained as it is, and the existing DCI The format is reused.

Option 1-2. In adding the HARQ process field, a variable DCI size according to the delay time of the satellite and the terminal is applied.

In this proposal, the flexible HARQ process field is applied in the same manner as in'Scheme 1-1', but it means that other fields in DCI are not dedicated. That is, it means that the HARQ process field in the DCI is variably changed based on the propagation delay between the satellite and the terminal, and the final DCI size is also changed. In this case, if the base station does not provide configuration information on the DCI size and format that can be changed to the terminal, the terminal increases the number of Bling decoding for detecting the corresponding PDCCH.

In this proposal, the operation may be different depending on whether the terminal receives information about propagation delay between the satellite and the terminal from the satellite base station.

If the information on the flexible HARQ process is not accurately signaled to the UE, the UE must perform blind decoding in consideration of the variable range of the corresponding DCI size. For example, when the terminal estimates the number of HARQ processes by indirectly estimating the propagation delay between the base station and the terminal based on the TA value, blind decoding may be performed by assuming all the number of cases. As an additional example, if the HARQ process additional bit estimated by the terminal based on the TA value is'N', blind decoding to be performed by the terminal may be assumed as follows. That is, there is a possibility to additionally perform blind decoding as much as N times the number of added HARQ process bits.

- Step-1: Perform blind decoding based on original DCI size

- Step-2: Original DCI size +1, blind decoding performed

- ...

- Step-N+1: Original DCI size +N, blind decoding performed

As described above, the present invention solves the ambiguity of the terminal operation and reduces transmission loss by applying a specific operation of the HARQ procedure considering the transmission delay time between the satellite and the terminal for a terminal serviced through a non-terrestrial network. Can be reduced.

12 is a diagram showing a configuration of a base station 1000 according to another embodiment.

Referring to FIG. 12, a base station 1000 according to another embodiment includes a control unit 1010, a transmission unit 1020, and a reception unit 1030.

The control unit 1010 is a method for controlling a delay-based HARQ procedure in an NR non-terrestrial network required to perform the above-described present invention, for a terminal serviced through a non-ground network, a propagation delay between the satellite and the terminal applying a flexible HARQ process number by considering controls the operation of the overall base station 1000 according to the method of providing a HARQ operation).

The transmission unit 1020 and the reception unit 1030 are used to transmit and receive signals, messages, and data necessary for carrying out the above-described present invention with the terminal.

13 is a diagram showing the configuration of a user terminal 1100 according to another embodiment.

Referring to FIG. 13, a user terminal 1100 according to another embodiment includes a receiving unit 1110, a control unit 1120, and a transmitting unit 1130.

The receiver 1110 receives downlink control information, data, and a message from the base station through a corresponding channel.

In addition, the control unit 1120 is a method for controlling a delay-based HARQ procedure in an NR non-terrestrial network required to perform the above-described present invention, for a terminal serviced through a non-terrestrial network, a propagation delay between the satellite and the terminal. A flexible HARQ process number considering) is applied to control the overall operation of the user terminal 1100 according to a method of providing HARQ operation.

The transmitter 1130 transmits uplink control information, data, and a message to the base station through a corresponding channel.

The above-described embodiments may be supported by standard documents disclosed in at least one of IEEE 802, 3GPP and 3GPP2 wireless access systems. That is, steps, configurations, and parts not described in order to clearly reveal the present technical idea among the embodiments may be supported by the aforementioned standard documents. In addition, all terms disclosed in the present specification can be described by the standard documents disclosed above.

The above-described embodiments can be implemented through various means. For example, the present embodiments may be implemented by hardware, firmware, software, or a combination thereof.

In the case of implementation by hardware, the method according to the embodiments includes one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), and FPGAs. (Field Programmable Gate Arrays), a processor, a controller, a microcontroller, or a microprocessor.

In the case of implementation by firmware or software, the method according to the embodiments may be implemented in the form of an apparatus, procedure, or function that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor through various known means.

In addition, terms such as "system", "processor", "controller", "component", "module", "interface", "model", or "unit" described above generally refer to computer-related entity hardware, hardware and software. It may mean a combination of, software, or running software. For example, the above-described components may be, but are not limited to, a process driven by a processor, a processor, a controller, a control processor, an object, an execution thread, a program, and/or a computer. For example, both the controller or processor and the application running on the controller or processor can be components. One or more components may reside within a process and/or thread of execution, and the components may be located on one device (eg, a system, a computing device, etc.) or distributed across two or more devices.

The above description is merely illustrative of the technical idea of the present disclosure, and those of ordinary skill in the technical field to which the present disclosure pertains will be able to make various modifications and variations without departing from the essential characteristics of the technical idea. In addition, the present embodiments are not intended to limit the technical idea of the present disclosure, but to explain the technical idea, and thus the scope of the technical idea is not limited by these embodiments. The scope of protection of the present disclosure should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present disclosure.

Claims (1)

In a delay-based HARQ procedure control method in an NR non-ground network,
A method for providing HARQ operation by applying a flexible HARQ process number taking into account a propagation delay between a satellite and a terminal for a terminal serviced through a non-ground network.

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