Method and apparatus for transmitting and receiving HARQ responses in sidelink communication

Abstract

Disclose a method and apparatus for sending and receiving HARQ responses in sidelink communication. The operating method of a first terminal includes the following steps: receiving DCI for scheduling sidelink transmission from a base station; sending first sidelink data to a second terminal based on the DCI; receiving a first SL HARQ response for the first sidelink data from the second terminal on a PSFCH; and sending the first SL HARQ response to the base station through a PUCCH at a feedback timing indicated by first information included in the DCI.

Description

Technical Field

[0001] The present invention relates to a sidelink communication technology, and more particularly, to a technology for reporting sidelink (SL) hybrid automatic repeat request (HARQ) responses. Background Art

[0002] In order to handle the rapidly increasing wireless data after the commercialization of 4th Generation (4G) communication systems (e.g., Long Term Evolution (LTE) communication systems or LTE-Advanced (LTE-A) communication systems), 5th Generation (5G) communication systems (e.g., New Radio (NR) communication systems) that use the frequency bands of 4G communication systems (e.g., bands below 6 GHz) and frequency bands higher than those of 4G communication systems (e.g., bands above 6 GHz) are being considered. 5G communication systems can support enhanced Mobile Broadband (eMBB) communication, Ultra-Reliable and Low-Latency Communication (URLLC), and massive Machine Type Communication (mMTC).

[0003] 4G communication systems and 5G communication systems can support Vehicle to Everything (V2X) communication (e.g., sidelink communication). V2X communication supported in cellular communication systems such as 4G communication systems and 5G communication systems can be referred to as "Cellular-V2X (C-V2X) communication". V2X communication (e.g., C-V2X communication) can include Vehicle to Vehicle (V2V) communication, Vehicle to Infrastructure (V2I) communication, Vehicle to Pedestrian (V2P) communication, Vehicle to Network (V2N) communication, etc.

[0004] In a cellular communication system, Vehicle-to-Everything (V2X) communication (e.g., C-V2X communication) can be performed based on sidelink communication technologies (e.g., Proximity based Services (ProSe) communication technology, Device-to-Device (D2D) communication technology, etc.). For example, a sidelink channel can be established for vehicles participating in Vehicle-to-Vehicle (V2V) communication (e.g., sidelink communication), and communication between vehicles can be performed using the sidelink channel. Configured grant (CG) resources can be used to perform sidelink communication. The CG resources can be configured periodically, and the CG resources can be used to send periodic data (e.g., periodic sidelink data).

[0005] On the other hand, a sidelink (SL) Hybrid Automatic Repeat reQuest (HARQ) response for sidelink data can be sent to a base station through an uplink channel. The sidelink data may not be sent according to priority, and in this case, a negative acknowledgment (NACK) can be sent to the base station as the SL HARQ response for the sidelink data. When the NACK for the sidelink data is received, the base station can send control information including an information element for retransmission of the sidelink data to a terminal. Since the information element received from the base station may be different from the information element used by the terminal for transmission of the sidelink data, the transmission of the sidelink data may not be accurately performed. Therefore, a method for solving this problem may be needed. SUMMARY OF THE INVENTION

[0006] TECHNICAL PROBLEM

[0007] An object of the present invention for solving the above problems is to provide a method and apparatus for sending and receiving a Hybrid Automatic Repeat reQuest (HARQ) response in sidelink communication.

[0008] TECHNICAL SOLUTION

[0009] According to a first embodiment of the present invention for achieving the above object, an operation method of a first terminal may include: receiving Downlink Control Information (DCI) for scheduling a sidelink transmission from a base station; transmitting first sidelink data to a second terminal based on the DCI; receiving a first SL HARQ response for the first sidelink data from the second terminal through a Physical Sidelink Feedback Channel (PSFCH); and transmitting the first SL HARQ response to the base station through a Physical Uplink Control Channel (PUCCH) at a feedback timing indicated by a first information included in the DCI.

[0010] Among them, the operation method of the first terminal may further include: receiving, from the base station, a high-layer message including information indicating one or more feedback timings, where the first information included in the DCI may indicate one of the one or more feedback timings.

[0011] Among them, the feedback timing may indicate the time gap between the PSFCH and the PUCCH.

[0012] Among them, the DCI may further include resource allocation information for the first sidelink data, and the first sidelink data may be transmitted on the PSSCH indicated by the resource allocation information.

[0013] Among them, the operation method of the first terminal may further include: sending sidelink control information (SCI) including resource allocation information for the first sidelink data to a second terminal, where the first sidelink data may be transmitted on the PSSCH indicated by the resource allocation information.

[0014] Among them, the SCI may further include an RV, and the RV may be determined based on a pre-configured mapping relationship.

[0015] Among them, sending the first SL HARQ response to the base station may include: generating a HARQ-ACK codebook including a DL HARQ response for the downlink data received from the base station and the first SL HARQ response; and sending the HARQ-ACK codebook to the base station through the PUCCH.

[0016] Among them, the operation method of the first terminal may further include: sending second sidelink data to the second terminal; and receiving a second SL HARQ response from the second terminal for the second sidelink data, where the second SL HARQ response may be sent to the base station together with the first SL HARQ response through the PUCCH.

[0017] According to a second embodiment of the present invention for achieving the above object, an operation method of a base station may include: generating a DCI including resource allocation information for sidelink data and first information indicating a feedback timing for an SL HARQ response for the sidelink data; sending the DCI to a first terminal through a PDCCH; and receiving the SL HARQ response from the first terminal through the PUCCH at the feedback timing, where the SL HARQ response may be generated by a second terminal that receives the sidelink data from the first terminal.

[0018] Among them, the operation method of the base station may further include: sending a high-layer message including information indicating one or more feedback timings, where the first information included in the DCI may indicate one of the one or more feedback timings.

[0019] Among them, the feedback timing may indicate the time gap between the PSFCH and the PUCCH.

[0020] Among them, the SL HARQ response may be received together with the DL HARQ response for the downlink data sent from the base station to the first terminal.

[0021] According to a third embodiment of the present invention for achieving the above object, a first terminal may include: a processor; and a memory configured to store at least one instruction executed by the processor, where the at least one instruction may be executed to: receive a DCI for scheduling sidelink transmission from the base station; send first sidelink data to a second terminal based on the DCI; receive a first SL HARQ response for the first sidelink data from the second terminal through the PSFCH; and send the first SL HARQ response to the base station through the PUCCH at a feedback timing indicated by first information included in the DCI.

[0022] Among them, the at least one instruction may be further executed to receive a high-layer message including information indicating one or more feedback timings from the base station, where the first information included in the DCI may indicate one of the one or more feedback timings.

[0023] Among them, the feedback timing may indicate the time gap between the PSFCH and the PUCCH.

[0024] Among them, the DCI may further include resource allocation information for the first sidelink data, and the first sidelink data may be sent on the PSSCH indicated by the resource allocation information.

[0025] Among them, the at least one instruction may be further executed to send sidelink control information (SCI) including resource allocation information for the first sidelink data to the second terminal, where the first sidelink data may be sent on the PSSCH indicated by the resource allocation information.

[0026] Among them, the SCI may further include an RV, and the RV may be determined based on a pre-configured mapping relationship.

[0027] Wherein, the at least one instruction may be further executed to generate, when sending the first SL HARQ response to the base station, a HARQ-ACK codebook including a DL HARQ response for downlink data received from the base station and the first SL HARQ response; and send the HARQ-ACK codebook to the base station via the PUCCH.

[0028] Wherein, the at least one instruction may be further executed to send second sidelink data to the second terminal; and receive a second SL HARQ response from the second terminal for the second sidelink data, wherein the second SL HARQ response may be sent to the base station together with the first SL HARQ response via the PUCCH.

[0029] Technical effects

[0030] According to the present invention, a transmitting terminal can receive DCI including information elements required for sidelink communication from a base station. When the information elements included in the DCI are different from the information elements for the current sidelink communication, the transmitting terminal can reconfigure the information elements according to preconfigured rules and can perform sidelink communication with a receiving terminal by using the reconfigured information elements. Therefore, sidelink communication can be effectively performed and the performance of the communication system can be improved. Description of the drawings

[0031] Figure 1 is a conceptual diagram showing a V2X communication scenario.

[0032] Figure 2 is a conceptual diagram showing a first embodiment of a cellular communication system.

[0033] Figure 3 is a conceptual diagram showing a first embodiment of a communication node constituting a cellular communication system.

[0034] Figure 4 is a block diagram showing a first embodiment of a user plane protocol stack of a UE performing sidelink communication.

[0035] Figure 5 is a block diagram showing a first embodiment of a control plane protocol stack of a UE performing sidelink communication.

[0036] Figure 6 is a block diagram showing a second embodiment of a control plane protocol stack of a UE performing sidelink communication.

[0037] Figure 7 is a sequence diagram showing a first embodiment of a sidelink communication method in a communication system.

[0038] Figure 8It is a sequence diagram showing a first embodiment of a method for transmitting a HARQ-ACK codebook (e.g., a semi-static HARQ-ACK codebook).

[0039] Figure 9 It is a sequence diagram showing a second embodiment of a method for transmitting a HARQ-ACK codebook. Detailed implementation

[0040] The present invention can be modified in various ways and can have multiple embodiments. Specific embodiments are shown by way of example in the drawings and described in detail. However, it should be understood that this description is not intended to limit the present invention to specific embodiments, and the present invention will cover all modifications, equivalent forms, and alternative forms falling within the spirit and technical scope of the present invention.

[0041] Although terms such as "first", "second", etc. may be used to describe various components, these components should not be construed as being limited by these terms. These terms are only used to distinguish one component from another. For example, without departing from the scope of the rights of the present invention, the first component may be referred to as the second component, and similarly, the second component may be referred to as the first component. The term "and / or" includes combinations of multiple related listed items or any one of the multiple related listed items.

[0042] It will be understood that when a component is referred to as being "connected" or "coupled" to another component, the component can be directly connected or coupled to the other component, or there may be other components in between. On the other hand, when a component is referred to as being "directly connected" or "directly coupled" to another component, there are no other components in between.

[0043] The terms used herein are only for describing specific embodiments and are not intended to limit the embodiments of the present invention. Singular expressions include plural expressions unless clearly indicated otherwise in the context. It will be understood that the terms "including", "having", etc. in the present application specify the presence of the features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, and do not exclude the presence or addition of one or more other features, quantities, steps, operations, components, parts, or combinations thereof.

[0044] Unless otherwise defined, all terms, including technical terms and scientific terms, used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. It will be further understood that terms defined in a general dictionary should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted as idealized or overly formal meanings unless clearly defined in the present application.

[0045] In the following, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. When describing the present invention, for the sake of overall understanding, the same reference numerals are used for the same components in the drawings, and repeated descriptions of the same components will be omitted.

[0046] Figure 1 is a conceptual diagram showing a V2X communication scenario.

[0047] Referring to Figure 1 , V2X communication may include vehicle-to-vehicle (V2V) communication, vehicle-to-infrastructure (V2I) communication, vehicle-to-pedestrian (V2P) communication, vehicle-to-network (V2N) communication, etc. V2X communication may be supported by a cellular communication system 140 (e.g., a cellular communication network), and the V2X communication supported by the cellular communication system 140 may be referred to as "cellular-V2X (C-V2X) communication". The cellular communication system 140 may include a 4G communication system (e.g., an LTE communication system or an LTE-A communication system), a 5G communication system (e.g., an NR communication system), etc.

[0048] V2V communication may refer to the communication between vehicle #1 100 (e.g., a communication node located in vehicle #1 100) and vehicle #2 110 (e.g., a communication node located in vehicle #2 110). Various driving information (e.g., velocity, heading, time, position, etc.) may be exchanged between vehicle 100 and vehicle 110 through V2V communication. For example, autonomous driving (e.g., platooning) may be supported based on the driving information exchanged through V2V communication. The V2V communication supported in the cellular communication system 140 may be performed based on "sidelink" communication technologies (e.g., ProSe communication technology and D2D communication technology, etc.). In this case, the communication between vehicle 100 and vehicle 110 may be performed by using at least one sidelink channel established between vehicle 100 and vehicle 110.

[0049] V2I communication may refer to the communication between vehicle #1 100 (e.g., a communication node located in vehicle 100) and infrastructure located by the roadside (e.g., a roadside unit (RSU)) 120. The infrastructure 120 may be a traffic light or a street lamp located by the roadside. For example, when performing V2I communication, communication may be performed between a communication node located in vehicle #1 100 and a communication node located in the traffic light. Traffic information, driving information, etc. may be exchanged between vehicle #1 100 and infrastructure 120 through V2I communication. The V2I communication supported in the cellular communication system 140 may be performed based on sidelink communication technologies (such as ProSe communication technology and D2D communication technology, etc.). In this case, the communication between vehicle 100 and infrastructure 120 may be performed by using at least one sidelink channel established between vehicle 100 and infrastructure 120.

[0050] V2P communication may refer to the communication between vehicle #1 100 (e.g., a communication node located in vehicle #1 100) and a person 130 (e.g., a communication node carried by person 130). Driving information of vehicle #1 100 and movement information of person 130 (such as speed, heading, time, location, etc.) may be exchanged between vehicle #1 100 and person 130 through V2P communication. The communication node located in vehicle #1 100 or the communication node carried by person 130 may generate an alarm indicating danger by judging a dangerous situation based on the obtained driving information and movement information. The V2P communication supported in the cellular communication system 140 may be performed based on sidelink communication technologies (such as ProSe communication technology and D2D communication technology, etc.). In this case, the communication between the communication node located in vehicle 100 and the communication node carried by person 130 may be performed by using at least one sidelink channel established between the communication nodes.

[0051] V2N communication may refer to the communication between vehicle #1 100 (e.g., a communication node located in vehicle #1 100) and a server connected via a cellular communication system 140 (e.g., a cellular communication network). The V2N communication may be performed based on 4G communication technologies (e.g., LTE communication technology or LTE-A communication technology specified in the 3GPP standard), 5G communication technologies (e.g., NR communication technology specified in 3GPP), etc. Additionally, the V2N communication may be performed based on communication technologies specified in the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard (e.g., Wireless Access in Vehicular Environments (WAVE) communication technology, Wireless Local Area Network (WLAN) communication technology, etc.), communication technologies specified in the IEEE 802.15 standard (e.g., Wireless Personal Area Network (WPAN), etc.), etc.

[0052] On the other hand, the cellular communication system 140 that supports V2X communication may be configured as follows.

[0053] Figure 2 It is a conceptual diagram showing a first embodiment of the cellular communication system.

[0054] Referring to Figure 2 , the cellular communication system may include an access network, a core network, etc. The access network may include a base station 210, a repeater 220, user equipment (UE) 231 to 236, etc. The UEs 231 to 236 may include communication nodes located in Figure 1 vehicles 100 and 110, communication nodes located in Figure 1 infrastructure 120, Figure 1 communication nodes carried by person 130, etc. When the cellular communication system supports 4G communication technology, the core network may include a serving-gateway (S-GW) 250, a packet data network (PDN) gateway (P-GW) 260, a mobility management entity (MME) 270, etc.

[0055] When the cellular communication system supports 5G communication technology, the core network may include a User Plane Function (UPF) 250, a Session Management Function (SMF) 260, an Access and Mobility Management Function (AMF) 270, etc. Alternatively, when Non-Stand Alone (NSA) is supported in the cellular communication system, the core network composed of an S-GW 250, a P-GW 260, and an MME 270, etc., can support both 4G and 5G communication technologies, and the core network composed of a UPF 250, an SMF 260, and an AMF 270, etc., can support both 5G and 4G communication technologies.

[0056] In addition, when the cellular communication system supports network slicing technology, the core network can be divided into multiple logical network slices. For example, a network slice supporting V2X communication (such as a V2V network slice, a V2I network slice, a V2P network slice, a V2N network slice, etc.) can be configured, and V2X communication can be supported through the V2X network slice configured in the core network.

[0057] Communication nodes (e.g., base stations, repeaters, UEs, S-GWs, P-GWs, MMEs, UPFs, SMFs, AMFs, etc.) constituting a cellular communication system can perform communication using at least one communication technology among code division multiple access (CDMA) technology, wideband CDMA (WCDMA) technology, time division multiple access (TDMA) technology, frequency division multiple access (FDMA) technology, orthogonal frequency division multiplexing (OFDM) technology, Filtered OFDM technology, orthogonal frequency division multiple access (OFDMA) technology, single carrier FDMA (SC-FDMA) technology, non-orthogonal multiple access (NOMA) technology, generalized frequency division multiplexing (GFDM) technology, filter bank multi-carrier (FBMC) technology, universal filtered multi-carrier (UFMC) technology, and space division multiple access (SDMA) technology.

[0058] Communication nodes (e.g., base stations, repeaters, UEs, S-GWs, P-GWs, MMEs, UPFs, SMFs, AMFs, etc.) constituting a cellular communication system can be configured as follows.

[0059] Figure 3 It is a conceptual diagram showing a first embodiment of a communication node constituting a cellular communication system.

[0060] Referring to Figure 3 , the communication node 300 may include at least one processor 310, a memory 320, and a transceiver 330 connected to a network to perform communication. Additionally, the communication node 300 may further include an input interface device 340, an output interface device 350, a storage device 360, etc. Each component included in the communication node 300 may be connected via a bus 370 and communicate with each other.

[0061] However, each component included in the communication node 300 may be connected to the processor 310 through a separate interface or a separate bus instead of the common bus 370. For example, the processor 310 may be connected to at least one of the memory 320, the transceiver 330, the input interface device 340, the output interface device 350, and the storage device 360 through a dedicated interface.

[0062] The processor 310 may execute at least one program instruction stored in at least one of the memory 320 and the storage device 360. The processor 310 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor that executes the method according to an embodiment of the present invention. Each of the memory 320 and the storage device 360 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 320 may include at least one of a read only memory (ROM) and a random access memory (RAM).

[0063] Referring again to Figure 2 , in the communication system, the base station 210 may form a macro cell or a small cell, and may be connected to the core network through an ideal backhaul or a non-ideal backhaul. The base station 210 may send the signals received from the core network to the UEs 231 to 236 and the repeater 220, and may send the signals received from the UEs 231 to 236 and the repeater 220 to the core network. UE#1 231, UE#2 232, UE#4 234, UE#5 235, and UE#6 236 may belong to the cell coverage of the base station 210. UE#1 231, UE#2 232, UE#4 234, UE#5 235, and UE#6 236 may be connected to the base station 210 by performing a connection establishment process with the base station 210. UE#1 231, UE#2 232, UE#4 234, UE#5 235, and UE#6 236 may communicate with the base station 210 after being connected to the base station 210.

[0064] The repeater 220 can be connected to the base station 210 and can relay communications between the base station 210 and the UE#3 233 and the UE#4 234. In other words, the repeater 220 can send the signals received from the base station 210 to the UE#3 233 and the UE#4 234, and can send the signals received from the UE#3 233 and the UE#4 234 to the base station 210. The UE#4 234 can belong to the cell coverage of the base station 210 and the cell coverage of the repeater 220 at the same time, and the UE#3 233 can belong to the cell coverage of the repeater 220. In other words, the UE#3 233 can be located outside the cell coverage of the base station 210. The UE#3 233 and the UE#4 234 can be connected to the repeater 220 by performing a connection establishment process with the repeater 220. The UE#3 233 and the UE#4 234 can communicate with the repeater 220 after being connected to the repeater 220.

[0065] The base station 210 and the repeater 220 can support multi-input multi-output (MIMO) (e.g., single user (SU)-MIMO, multi-user (MU)-MIMO, massive MIMO, etc.) communication technologies, coordinated multipoint (CoMP) communication technologies, Carrier Aggregation (CA) communication technologies, unlicensed band communication technologies (e.g., Licensed Assisted Access (LAA), enhanced LAA (eLAA), etc.), sidelink communication technologies (e.g., ProSe communication technologies, D2D communication technologies), etc. The UE#1 231, the UE#2 232, the UE#5 235, and the UE#6 236 can perform operations corresponding to the base station 210 and operations supported by the base station 210, etc. The UE#3 233 and the UE#4 234 can perform operations corresponding to the repeater 220 and operations supported by the repeater 220, etc.

[0066] Here, the base station 210 can be referred to as a Node B (NB), an evolved Node B (eNB), a base transceiver station (BTS), a radio remote head (RRH), a transmission reception point (TRP), a radio unit (RU), a roadside unit (RSU), a radio transceiver, an access point, an access node, etc. The repeater 220 can be referred to as a small base station, a relay node, etc. Each of UEs 231 to 236 can be referred to as a terminal, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, an on-broad unit (OBU), etc.

[0067] On the other hand, the communication between UE#5 235 and UE#6 236 can be performed based on sidelink communication technologies (e.g., ProSe communication technology, D2D communication technology). The sidelink communication can be performed based on a one-to-one scheme or a one-to-many scheme. When performing V2V communication using sidelink communication technology, UE#5 235 can be a communication node in vehicle #1 100 located at Figure 1 and UE#6 236 can be a communication node in vehicle #2 110 located at Figure 1 When performing V2I communication using sidelink communication technology, UE#5 235 can be a communication node in vehicle #1 100 located at Figure 1 and UE#6 236 can be a communication node in infrastructure 120 located at Figure 1 When performing V2P communication using sidelink communication technology, UE#5 235 can be a communication node in vehicle #1 100 located at Figure 1 and UE#6 236 can be Figure 1 a communication node carried by person 130 located at

[0068] Depending on the locations of the UEs (e.g., UE#5 235 and UE#6 236) participating in sidelink communication, the scenarios of applying sidelink communication can be classified as shown in Table 1 below. For example, Figure 2 The scenario of sidelink communication between the shown UE#5 235 and UE#6 236 can be sidelink communication scenario #C.

[0069] [Table 1]

[0070] Sidelink communication scenario Location of UE#5 235 Location of UE#6 236 #A Outside the coverage of base station 210 Outside the coverage of base station 210 #B Inside the coverage of base station 210 Outside the coverage of base station 210 #C Inside the coverage of base station 210 Inside the coverage of base station 210 #D Inside the coverage of base station 210 Inside the coverage of other base stations

[0071] On the other hand, the user plane protocol stack of the UEs (e.g., UE#5 235 and UE#6 236) performing sidelink communication can be configured as follows.

[0072] Figure 4 is a block diagram showing a first embodiment of the user plane protocol stack of the UE performing sidelink communication.

[0073] As Figure 4 shown, UE#5 235 can be Figure 2 the shown UE#5 235, and UE#6 236 can be Figure 2 the shown UE#6 236. The sidelink communication scenario between UE#5 235 and UE#6 236 can be one of sidelink communication scenarios #A to #D in Table 1. The user plane protocol stack of each of UE#5 235 and UE#6 236 can include a Physical (PHY) layer, a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, and a Packet Data Convergence Protocol (PDCP) layer.

[0074] The sidelink communication between UE#5 235 and UE#6 236 can be performed using a PC5 interface (e.g., PC5-U interface). The Layer 2 identifier (ID) (e.g., source Layer 2 ID, destination Layer 2 ID) can be used for sidelink communication, and the Layer 2 ID can be an ID configured for V2X communication (e.g., V2X service). Additionally, in sidelink communication, hybrid automatic repeat request (HARQ) feedback operations can be supported, and RLC acknowledged mode (RLC AM) or RLC unacknowledged mode (RLC UM) can be supported.

[0075] On the other hand, the control plane protocol stack of the UEs (e.g., UE#5 235 and UE#6 236) performing sidelink communication can be configured as follows.

[0076] Figure 5 is a block diagram showing a first embodiment of the control plane protocol stack of a UE performing sidelink communication, Figure 6 is a block diagram showing a second embodiment of the control plane protocol stack of a UE performing sidelink communication.

[0077] As Figure 5 and Figure 6 shown, UE#5 235 can be the UE#5 235 shown in Figure 2 shown, and UE#6 236 can be the UE#6 236 shown in Figure 2 shown. The sidelink communication scenario between UE#5 235 and UE#6 236 can be one of sidelink communication scenarios #A to #D in Table 1. Figure 5 The control plane protocol stack shown can be a control plane protocol stack for sending and receiving broadcast information (e.g., Physical Sidelink Broadcast Channel (PSBCH)).

[0078] Figure 5 The control plane protocol stack shown can include a PHY layer, a MAC layer, an RLC layer, and a radio resource control (RRC) layer. The sidelink communication between UE#5 235 and UE#6 236 can be performed using a PC5 interface (e.g., PC5-C interface). Figure 6 The control plane protocol stack shown can be a control plane protocol stack for sidelink communication in a one-to-one scenario. Figure 6 The control plane protocol stack shown can include a PHY layer, a MAC layer, an RLC layer, a PDCP layer, and a PC5 signaling protocol layer.

[0079] On the other hand, the channels used in sidelink communication between UE#5 235 and UE#6 236 may include Physical Sidelink Shared Channel (PSSCH), Physical Sidelink Control Channel (PSCCH), Physical Sidelink Discovery Channel (PSDCH), and Physical Sidelink Broadcast Channel (PSBCH). The PSSCH can be used to transmit and receive sidelink data and can be configured in the UE (e.g., UE#5 235 or UE#6 236) through higher layer signaling. The PSCCH can be used to transmit and receive sidelink control information (SCI), and can also be configured in the UE (e.g., UE#5 235 or UE#6 236) through higher layer signaling.

[0080] The PSDCH can be used for the discovery process. For example, discovery signals can be transmitted through the PSDCH. The PSBCH can be used to transmit and receive broadcast information (e.g., system information). Additionally, demodulation reference signal (DMRS), synchronization signal, etc. can be used in the sidelink communication between UE#5 235 and UE#6 236. The synchronization signal can include primary sidelink synchronization signal (PSSS) and secondary sidelink synchronization signal (SSSS).

[0081] On the other hand, the sidelink transmission mode (TM) can be classified into sidelink TM#1 to TM#4 as shown in Table 2 below.

[0082] [Table 2]

[0083] Sidelink TM Description #1 Transmitted using resources scheduled by the base station #2 UE transmits autonomously without base station scheduling #3 In V2X communication, transmitted using resources scheduled by the base station #4 In V2X communication, UE transmits autonomously without base station scheduling

[0084] When sidelink TM#3 or TM#4 is supported, each of UE#5 235 and UE#6 236 can utilize the resource pool configured by the base station 210 to perform sidelink communication. Resource pools can be configured for each of the sidelink control information and sidelink data.

[0085] The resource pool for sidelink control information can be configured based on the RRC signaling procedure (e.g., dedicated RRC signaling procedure, broadcast RRC signaling procedure). The resource pool for receiving sidelink control information can be configured through the broadcast RRC signaling procedure. When sidelink TM#3 is supported, the resource pool for transmitting sidelink control information can be configured through the dedicated RRC signaling procedure. In this case, the sidelink control information can be transmitted through the resources scheduled by the base station 210 within the resource pool configured through the dedicated RRC signaling procedure. When sidelink TM#4 is supported, the resource pool for transmitting sidelink control information can be configured through the dedicated RRC signaling procedure or the broadcast RRC signaling procedure. In this case, the sidelink control information can be transmitted through the resources autonomously selected by the UE (e.g., UE#5235 or UE#6236) within the resource pool configured through the dedicated RRC signaling procedure or the broadcast RRC signaling procedure.

[0086] When sidelink TM#3 is supported, the resource pool for transmitting and receiving sidelink data may not be configured. In this case, the sidelink data can be transmitted and received through the resources scheduled by the base station 210. When sidelink TM#4 is supported, the resource pool for transmitting and receiving sidelink data can be configured through the dedicated RRC signaling procedure or the broadcast RRC signaling procedure. The sidelink data can be transmitted and received through the resources autonomously selected by the UE (e.g., UE#5235 or UE#6236) within the resource pool configured through the dedicated RRC signaling procedure or the broadcast RRC signaling procedure.

[0087] Hereinafter, a method for retransmitting sidelink data will be described. In an embodiment, the HARQ response may be referred to as "HARQ-acknowledgment (HARQ-ACK)". The HARQ response can be an ACK or a negative ACK (NACK). The downlink (DL) HARQ response can be a HARQ response for downlink data, the uplink (UL) HARQ response can be a HARQ response for uplink data, and the sidelink (SL) HARQ response can be a HARQ response for sidelink data.

[0088] Even when describing the execution of a method (e.g., transmitting or receiving a signal) at a first communication node in a communication node, the corresponding second communication node can also execute a method corresponding to the method executed at the first communication node (e.g., receiving or transmitting a signal). In other words, when describing the operation of UE#1 (e.g., vehicle#1), the corresponding UE#2 (e.g., vehicle#2) can execute an operation corresponding to the operation of UE#1. Conversely, when describing the operation of UE#2, the corresponding UE#1 can execute an operation corresponding to the operation of UE#2. In the embodiments described below, the operation of the vehicle can be the operation of the communication node located in the vehicle.

[0089] In an embodiment, the signaling may be one or a combination of two or more of high-layer signaling, MAC signaling, and physical (PHY) signaling. Messages for high-layer signaling may be referred to as "high-layer messages" or "high-layer signaling messages". Messages for MAC signaling may be referred to as "MAC messages" or "MAC signaling messages". Messages for PHY signaling may be referred to as "PHY messages" or "PHY signaling messages". High-layer signaling may refer to operations of sending and receiving system information (e.g., master information block (MIB), system information block (SIB)) and / or RRC messages. MAC signaling may refer to operations of sending and receiving MAC control elements (CE). PHY signaling may refer to operations of sending and receiving control information (e.g., downlink control information (DCI), uplink control information (UCI), SCI).

[0090] Sidelink signals may be synchronization signals and reference signals for sidelink communication. For example, the synchronization signal may be a synchronization signal / physical broadcast channel (SS / PBCH) block, sidelink synchronization signal (SLSS), primary sidelink synchronization signal (PSSS), secondary sidelink synchronization signal (SSSS), etc. The reference signal may be a channel state information-reference signal (CSI-RS), DMRS, phase tracking-reference signal (PT-RS), cell specific reference signal (CRS), sounding reference signal (SRS), discovery reference signal (DRS), etc.

[0091] The sidelink channel can be a PSSCH, PSCCH, PSDCH, PSBCH, physical sidelink feedback channel (PSFCH), etc. Additionally, the sidelink channel can refer to a sidelink channel that includes a sidelink signal mapped to specific resources in the corresponding sidelink channel. Sidelink communication can support broadcast services, multicast services, groupcast services, and unicast services.

[0092] Sidelink communication can be performed based on a single SCI scheme or a multi-SCI scheme. When using the single SCI scheme, data transmission (e.g., sidelink data transmission, sidelink-shared channel (SL-SCH) transmission) can be performed based on a single SCI (e.g., the Phase 1 SCI). When using the multi-SCI scheme, two SCIs (e.g., the Phase 1 SCI and the Phase 2 SCI) can be used to perform data transmission. The SCI can be sent via the PSCCH and / or PSSCH. When using the single SCI scheme, the SCI (e.g., the Phase 1 SCI) can be sent via the PSCCH. When using the multi-SCI scheme, the Phase 1 SCI can be sent via the PSCCH, and the Phase 2 SCI can be sent via the PSCCH or PSSCH. The Phase 1 SCI can be referred to as the "First Phase SCI", and the Phase 2 SCI can be referred to as the "Second Phase SCI".

[0093] The Phase 1 SCI can include more than one information element among priority information, frequency resource assignment information, time resource allocation information, resource reservation period information, DMRS mode information, Phase 2 SCI format information, beta_offset indicator, the number of DMRS ports, and modulation and coding scheme (MCS) information. The Phase 2 SCI can include more than one information element among HARQ process identifier (ID), redundancy version (RV), source ID, target ID, CSI request information, region ID, and communication range requirements.

[0094] Figure 7 It is a sequence diagram showing a first embodiment of a sidelink communication method in a communication system.

[0095] As Figure 7As shown, a communication system may include a base station, a transmitting terminal (e.g., a first terminal), and a receiving terminal (e.g., a second terminal). The base station may be Figure 2 the base station 210 shown, and the transmitting terminal may be Figure 2 the UE#5 235 shown, and the receiving terminal may be Figure 2 the UE#6 236 shown. Each of the base station, the transmitting terminal, and the receiving terminal may be configured the same as or similar to Figure 3 the communication node 300 shown. The transmitting node and the receiving node may support Figures 4 to 6 the protocol stack shown.

[0096] The base station may generate downlink control information (DCI) for sidelink scheduling and transmit the DCI via a physical downlink control channel (PDCCH) (S701). The DCI for sidelink scheduling may be referred to as "SL DCI". The SL DCI may have a DCI format 3_0 or a DCI format 3_1. The SL DCI may include a resource pool index, a time gap, a HARQ process number, a redundancy version (RV), a new data indicator (NDI), the lowest index of a subchannel allocated for an initial transmission, an SCI format 1-A field (e.g., frequency resource allocation, time resource allocation), a PSFCH to HARQ feedback timing indicator, a PUCCH resource indicator, a configuration index, a counter sidelink assignment index, and / or a padding bit. The frequency resource allocation and the time resource allocation included in the SL DCI may indicate resources for sidelink communication (e.g., SCI transmission and / or SL data transmission).

[0097] The transmitting terminal may receive the SL DCI from the base station and may identify information elements included in the SL DCI. The transmitting terminal may perform sidelink communication based on the information elements included in the SL DCI. Additionally, the receiving terminal may also receive the SL DCI from the base station.

[0098] The transmitting terminal may generate an SCI based on the information elements included in the SL DCI and send the SCI to the receiving terminal (S702). The SCI may be sent on the PSCCH and / or PSSCH. The SCI may have one or more of the SCI format 1-A, SCI format 2-A, and SCI format 2-B. The transmitting terminal may send SL data to the receiving terminal by using the resources indicated by the SCI (S703). The receiving terminal may receive the SCI from the transmitting terminal and may receive the SL data from the transmitting terminal in the resources indicated by the SCI. The sidelink communication procedure between the transmitting terminal and the receiving terminal may be performed without an SCI. When the SL DCI includes resource allocation information for sidelink communication (e.g., frequency resource allocation, time resource allocation), the sidelink communication procedure between the transmitting terminal and the receiving terminal may be performed based on the SL DCI instead of the SCI. In other words, the transmission of SL data (e.g., PSSCH transmission) may be scheduled by the SL DCI.

[0099] The receiving terminal may generate an SL HARQ response for the SL data and may send the SL HARQ response to the transmitting terminal (S704). The SL HARQ response may be sent via the PSFCH. The transmitting terminal may receive the SL HARQ response from the receiving terminal. The transmitting terminal may send the SL HARQ response to the base station by using the resources indicated by the information elements included in the SL DCI (e.g., physical uplink control channel (PUCCH), physical uplink shared channel (PUSCH)) (S705). The base station may receive the SL HARQ response from the transmitting terminal and may identify the reception status of the SL data based on the SL HARQ response.

[0100] On the other hand, in a specific case (e.g., when the SL data has a low priority), the transmitting terminal may not send the SL data (e.g., PSSCH) scheduled by the SL DCI. In this case, the transmitting terminal may report a NACK to the base station. Additionally, when the SCI is not sent according to the SL DCI, the transmitting terminal may report a NACK to the base station. These operations may cause problems in the retransmission process of the SL data. As a first problem, the redundancy version (RV) included in the SL DCI for retransmission may be different from the actual RV of the SL data sent from the transmitting terminal. Therefore, the RV of the SL data sent on the PSSCH may be different from the RV indicated by the SL DCI. As a second problem, it may not be clear whether the SL data transmission process based on the NACK that occurs when the transmission of the SL data is not performed is counted as a retransmission process.

[0101] When a NACK for SL data is received, the base station may configure information elements (e.g., parameters) for retransmission of the SL data. For example, the base station may configure the RV for retransmission of the SL data. The RV for retransmission may be configured differently from the RV for a previous transmission (e.g., an initial transmission). In addition, the base station may increment the number of retransmissions of the SL data by 1. However, when a NACK is generated due to non-execution of the transmission of the SL data, the transmitting terminal may not reconfigure the RV for transmission of the SL data and may determine that the non-executed transmission of the SL data is not included in the number of retransmissions. Therefore, the following two schemes can be used to solve these problems.

[0102] - Scheme 1: Parameters for retransmission of SL data can be redefined.

[0103] - Scheme 2: A NACK generated when the transmission of SL data is not executed can be configured differently from a NACK generated due to reception failure of the SL data.

[0104] In the following embodiments, a NACK generated due to reception failure of the SL data may be referred to as a "type 1 NACK", and a NACK generated when the transmission of the SL data is not executed may be referred to as a "type 2 NACK".

[0105] Scheme 1: Method for configuring parameters for retransmission of SL data

[0106] When a type 2 NACK is received from the transmitting terminal, the base station may send SL DCI (hereinafter referred to as "retransmission SL DCI") to the transmitting terminal to retransmit the SL data associated with the type 2 NACK. The transmitting terminal may receive the retransmission SL DCI from the base station and may identify the information elements included in the retransmission SL DCI. In this case, the transmitting terminal may generate an SCI including the previous RV of the RV included in the retransmission SL DCI and may send the generated SCI to the receiving terminal. In addition, the NDI included in the retransmission SL DCI may be configured to indicate that the SL DCI is for a retransmission operation.

[0107] When the RV pattern is (RV#0 → RV#1 → RV#2 → RV#3) and the retransmission SL DCI includes RV#0, the transmitting terminal may send an SCI including RV#3, i.e., the previous RV of RV#0, to the receiving terminal, and the transmitting terminal may determine the RV included in the SCI based on the mapping relationship defined in Table 3. The RV included in the SCI may be determined based on a circular buffer scheme. In addition, the NDI included in the SCI may be configured to indicate that the SCI is for a retransmission operation.

[0108] [Table 3]

[0109] RV included in the retransmitted SL DCI RV included in the SCI RV#0 ←→ RV#3 RV#1 ←→ RV#0 RV#2 ←→ RV#1 RV#3 ←→ RV#2

[0110] The transmitting terminal can use the RV included in the SCI instead of re - transmitting the SL DCI to send the SL data. When receiving the SCI from the transmitting terminal, the receiving terminal can perform the receiving operation of the SL data by using the RV included in the SCI.

[0111] On the other hand, the transmitting terminal may not be able to perform the sending operation of the SL data twice. The two sending operations that the transmitting terminal cannot perform can be consecutive or non - consecutive. In this case, the transmitting terminal can determine the RV included in the SCI based on the mapping relationship defined in Table 4 below. For example, when RV#0 is included in the re - transmitted SL DCI and the sending operation of the SL data cannot be continuously performed twice, the transmitting terminal can determine RV#2 as the RV included in the SCI. The NDI included in the re - transmitted SL DCI can be configured to indicate that the SL DCI is for the re - transmission operation, and the NDI included in the SCI can be configured to indicate that the SCI is for the re - transmission operation.

[0112] [Table 4]

[0113] RV included in the retransmitted SL DCI RV included in the SCI RV#0 ←→ RV#2 RV#1 ←→ RV#3 RV#2 ←→ RV#0 RV#3 ←→ RV#1

[0114] On the other hand, in a specific case, the RV included in the SCI can be configured differently from the RV included in the re - transmitted SL DCI. The RV can be divided into type 1 RV that can be used alone to decode data (e.g., SL data) and type 2 RV that can be used to decode data together with other RVs. RV#0 and RV#2 can be type 1 RV, and RV#1 and RV#3 can be type 2 RV. To ensure the transmission of SL data with type 1 RV, the RV included in the SCI can be configured differently from the RV included in the re - transmitted SL DCI.

[0115] When the re - transmitted SL DCI associated with the type 2 NACK includes type 2 RV, the transmitting terminal can send an SCI including the previous RV (e.g., RV#0 or RV#2) of the type 2 RV (e.g., RV#1 or RV#3) included in the re - transmitted SL DCI. This operation can be applied to the case where the type 2 NACK is the NACK generated when the initial transmission is not performed. When the re - transmitted SL DCI associated with the type 2 NACK includes type 1 RV, the transmitting terminal can send an SCI including the type 1 RV (e.g., RV#0 or RV#2) indicated by the re - transmitted SL DCI.

[0116] As another method, when the transmission operation of the SL data cannot be continuously performed, when receiving a retransmission SL DCI associated with a type 2 NACK, the transmitting terminal may transmit an SCI including a previous RV of the RV included in the retransmission SL DCI, and when receiving a retransmission SL DCI associated with a type 2 NACK thereafter, the transmitting terminal may transmit an SCI including the RV indicated by the corresponding retransmission SL DCI.

[0117] The transmission operation of the SL data according to the type 2 NACK may be counted as a retransmission.

[0118] Solution 2: Method for configuring type 2 NACK

[0119] - Feedback of HARQ response based on sequence selection

[0120] The transmitting terminal may feedback a HARQ response to the base station based on sequence selection. When the HARQ response is ACK, the transmitting terminal may select a sequence mapped to ACK from a pre-configured sequence set, and may send the selected sequence to the base station through the PUCCH. When the HARQ response is NACK (e.g., type 1 NACK or type 2 NACK), the transmitting terminal may select a sequence mapped to NACK from a pre-configured sequence set, and may send the selected sequence to the base station through the PUCCH. The sequences mapped to ACK, type 1 NACK, and type 2 NACK may be configured as shown in Table 5 below.

[0121] [Table 5]

[0122] Sequence #1 Sequence #2 Sequence #3 ACK Type 1 NACK Type 2 NACK

[0123] The sequences defined in Table 5 may be orthogonal sequences or semi-orthogonal sequences. Alternatively, sequences may be defined based on different cyclic shift values. Sequence #3 may be generated using a value between the cyclic shift value applied to Sequence #1 and the cyclic shift value applied to Sequence #2. Alternatively, Sequence #3 may be generated by applying a pre-configured cyclic shift value to Sequence #2. Alternatively, Sequence #3 may be generated by puncturing specific resource elements (REs) based on Sequence #2. To support the above operations, the base station may notify the terminal (e.g., the transmitting terminal and / or the receiving terminal) of the cyclic shift value, puncturing pattern, and / or puncturing rate using one or a combination of two or more of higher layer signaling, MAC signaling, and PHY signaling. Alternatively, the cyclic shift value, puncturing pattern, and / or puncturing rate may be predefined in the technical specification. Sequence #3 may be different from Sequence #1 and Sequence #2. Sequence #3 may be configured according to various schemes to be different from Sequence #1 and Sequence #2.

[0124] On the other hand, the feedback operation of the HARQ response can be performed in units of code block groups (CBGs). The transmitting terminal can send the HARQ responses for two CBGs to the base station on the PUCCH. In this case, the sequences of the HARQ responses for two CBGs can be defined as shown in Table 6 below.

[0125] [Table 6]

[0126] Sequence #1 Sequence #2 Sequence #3 Sequence #4 Sequence #5 (A, A) (A, N1) (N1, A) (N1, N1) (N2, N2)

[0127] The sequences defined in Table 6 can be orthogonal sequences or semi-orthogonal sequences. Alternatively, the sequences can be defined based on different cyclic shift values. In Table 6, A can refer to ACK, N1 can refer to type 1 NACK, and N2 can refer to type 2 NACK. Table 6 can be extended and applied to the case where the HARQ response for more than three CBGs is indicated by one sequence. For example, the sequences of the HARQ responses for three CBGs can be defined as shown in Table 7 below.

[0128] [Table 7]

[0129] Sequence #1 Sequence #2 Sequence #3 (A, A, A) (A, A, N1) (A, N1, A) Sequence #4 Sequence #5 Sequence #6 (N1, A, A) (N1, A, N1) (N1, N1, A) Sequence #7 Sequence #8 Sequence #9 (A, N1, N1) (N1, N1, N1) (N2, N2, N2)

[0130] In another embodiment, the sequences of the HARQ responses for two CBGs can be defined as shown in Table 8 below. The sequences defined in Table 8 can be orthogonal sequences or semi-orthogonal sequences. Alternatively, the sequences can be defined based on different cyclic shift values.

[0131] [Table 8]

[0132] Sequence #1 Sequence #2 Sequence #3 (A, A) (A, N1) (A, N2) Sequence #4 Sequence #5 Sequence #6 (N1, A) (N2, A) (N1, N1) Sequence #7 Sequence #8 Sequence #9 (N2, N1) (N1, N2) (N2, N2)

[0133] The transmitting terminal can select one sequence from nine sequences and can send the selected sequence to the base station via the PUCCH (or PUSCH). The sequences indicating type 2 NACK (e.g., sequence #3, sequence #5, sequence #7, sequence #8, and sequence #9) can be generated based on modified values of the cyclic shift values of the sequences that do not indicate type 2 NACK (e.g., sequence #1, sequence #2, sequence #4, and sequence #6). Alternatively, the sequences indicating type 2 NACK can be generated by dotting specific REs with the sequences that do not indicate type 2 NACK as a reference. The sequences indicating type 2 NACK can be configured to be different from the sequences that do not indicate type 2 NACK. The sequences indicating type 2 NACK can be configured according to various schemes to be detectable.

[0134] - Feedback of HARQ response based on a codebook

[0135] Figure 8It is a sequence diagram showing a first embodiment of a method of transmitting a HARQ-ACK codebook (e.g., a semi-static HARQ-ACK codebook).

[0136] As Figure 8 shown, a transmission period (e.g., the time span of the codebook) may include 4 time slots, and communication may be performed using three carriers in the transmission period. Carrier #0 and Carrier #1 may be used for downlink communication, and Carrier #2 may be used for sidelink communication. One TB (or one CBG) may be transmitted in each of Carrier #0 and Carrier #2, and two TBs (or two CBGs) may be transmitted in Carrier #1.

[0137] In the HARQ-ACK codebook, AN may indicate ACK or NACK as a result of decoded data, and N may indicate NACK. Scheduled transmission may be a transmission scheduled by semi-static signaling or dynamic signaling. Unscheduled resources may be resources that are not scheduled. In other words, a specific resource may not be used for data transmission and reception, and in this case, the specific resource may be an unscheduled resource. Since no data (e.g., SL data) is transmitted in the unscheduled resource, the terminal may not receive data in the unscheduled resource, and thus may transmit a NACK. In other words, for the configuration of the HARQ-ACK codebook, a NACK for the unscheduled resource may be generated.

[0138] Alternatively, the unscheduled resource may be a resource scheduled by scheduling information (e.g., scheduling information included in DCI or SCI) that the terminal has not received. In this case, since the scheduling information is not received, the terminal may not be able to receive the data corresponding to the scheduling information, and thus may transmit a NACK. For example, when the SL DCI is missing, the transmitting terminal may not know whether the SL DCI has been transmitted. Therefore, the transmitting terminal may send a NACK to the base station. When the base station receives a NACK from the transmitting terminal, the base station may determine that the reception of the SL DCI or the reception of the SL data has failed, and then perform a retransmission process of the SL data.

[0139] When the transmission unit of data (e.g., SL data) is a time slot, a HARQ-ACK codebook including 16 HARQ response bits can be generated. A terminal (e.g., a transmitting terminal) can send the HARQ-ACK codebook to a base station via the PUCCH allocated within time slot #4 of carrier #0. For example, the transmitting terminal can send SL data in carrier #2 and can receive a HARQ response (e.g., ACK or NACK) for the SL data from the receiving terminal explicitly or implicitly. The transmitting terminal can generate a HARQ-ACK codebook including HARQ responses for one or more SL data or a HARQ-ACK codebook including HARQ responses for one or more SL data and HARQ responses for one or more DL data (e.g., data transmitted in carrier #0 and carrier #1), and send the HARQ-ACK codebook to the base station.

[0140] The feedback timing of the HARQ response for SL data (e.g., PUCCH timing) can be set by the base station. For example, the base station can send a high-layer message including information on one or more HARQ feedback timings to a terminal (e.g., a transmitting terminal and / or a receiving terminal). The HARQ feedback timing can indicate the time gap between the PSFCH and the PUCCH. The HARQ feedback timing can be referred to as "sl-PSFCH-ToPUCCH", and "SL-ScheduledConfig" including "sl-PSFCH-ToPUCCH" can be included in the high-layer message sent from the base station to the terminal.

[0141] A terminal (e.g., a transmitting terminal and / or a receiving terminal) can receive a high-layer message from the base station and can identify information on one or more HARQ feedback timings included in the high-layer message. The base station can send SL DCI including a HARQ feedback timing indicator to a terminal (e.g., a transmitting terminal and / or a receiving terminal). The HARQ feedback timing indicator can be referred to as a PSFCH-to-HARQ feedback timing indicator. The HARQ feedback timing indicator can indicate the transmission time (e.g., PUCCH timing) of the HARQ response for SL data. For example, the HARQ feedback timing indicator can indicate the time gap (e.g., time offset) between the PSFCH and the PUCCH timing (e.g., HARQ feedback timing). The HARQ feedback timing indicator included in the SL DCI can indicate one of the one or more HARQ feedback timings configured by the high-layer message.

[0142] A terminal (e.g., a transmitting terminal and / or a receiving terminal) can receive SL DCI from a base station and can identify information elements included in the SL DCI (e.g., scheduling information of SL data, HARQ feedback timing indicator, etc.). The transmitting terminal can send SL data to the receiving terminal and can receive a HARQ response for the SL data from the receiving terminal on the PSFCH. Resources indicated by the SL DCI can be used to send and receive SL data. The transmitting terminal can send a HARQ response for the SL data to the base station using resources (e.g., PUCCH) indicated by the HARQ feedback timing indicator included in the SL DCI. The base station can receive a HARQ response for the SL data from the transmitting terminal in resources (e.g., PUCCH) indicated by the HARQ feedback timing indicator included in the SL DCI.

[0143] On the other hand, in Figure 8 the embodiment shown, DL HARQ response bits and SL HARQ response bits can be generated independently, the DL HARQ response bits and the SL HARQ response bits can be concatenated to generate a HARQ-ACK codebook, and one HARQ-ACK codebook can be sent to the base station. The concatenation operation between the DL HARQ response bits and the SL HARQ response bits can be performed according to various schemes. For example, the SL HARQ response bits can be concatenated after the DL HARQ response bits.

[0144] In Figure 8 the embodiment shown, when ACK is set to 1 and NACK is set to 0, the HARQ-ACK codebook can be configured as shown in Table 9 below. AN can refer to ACK or NACK.

[0145] [Table 9]

[0146] 1 0 0 1 0 0 0 0 0 0 0 1 0 1 0 0

[0147] The SL HARQ response can be (NACK, ACK, NACK, NACK). Here, the first NACK and the third NACK can be NACKs for the scheduled resources. The NACK generated when the SL data transmission operation is not performed in the scheduled resources can be a type 2 NACK (i.e., N2). When the first NACK is a type 2 NACK, the SL HARQ response can be configured as shown in Table 10 below. The NACK for the scheduled resources (e.g., N1) can be distinguished from the NACK for the non-scheduled resources (e.g., N1).

[0148] [Table 10]

[0149]

[0150] To indicate N2 of Table 10, the indication bits can be configured as shown in Tables 11 to 14 below. In Table 11, the indication bit of N2 can be set to 1. In this case, the HARQ-ACK codebook can include 1 bit as the indication bit of N2.

[0151] [Table 11]

[0152] Carrier #2 (SL) 1 N / A N / A N / A

[0153] In Table 12, the indication bit of N2 for the scheduled resource can be set to 1, and the indication bit of N1 for the scheduled resource can be set to 0. In this case, the HARQ-ACK codebook can include 2 bits (e.g., the indication bit of N2 + the indication bit of N1). The HARQ-ACK codebook may not include the indication bit of ACK for the scheduled resource and the indication bit of NACK for the non-scheduled resource.

[0154] [Table 12]

[0155] Carrier #2 (SL) 1 N / A 0 N / A

[0156] In Table 13, the indication bit of N2 for the scheduled resource can be set to 1, the indication bit of N1 for the scheduled resource can be set to 0, and the indication bit of ACK for the scheduled resource can be set to 0. In this case, the HARQ-ACK codebook can include 3 bits (e.g., the indication bit of N2 + the indication bit of N1 + the indication bit of ACK).

[0157] [Table 13]

[0158] Carrier #2 (SL) 1 0 0 N / A

[0159] In Table 14, the indication bit of N2 for the scheduled resource can be set to 1, and the indication bits for the remaining cases can be set to 0. In this case, the HARQ-ACK codebook can include 4 bits.

[0160] [Table 14]

[0161] Carrier #2 (SL) 1 0 0 0

[0162] The position of N2 for multiple scheduled resources may not be recognizable. To identify the position of N2, additional information can be sent.

[0163] Figure 9 is a sequence diagram showing a second embodiment of the method for transmitting the HARQ-ACK codebook. As Figure 9As shown, three carriers can be used to perform communication. Carrier #0 and Carrier #1 can be used for downlink communication, and Carrier #2 can be used for sidelink communication. One TB (or one CBG) can be sent in each carrier. The HARQ-ACK feedback operation can be performed based on a dynamic codebook. When using the dynamic codebook, the HARQ response (e.g., NACK) for non-scheduled resources may not be fed back. Therefore, the number of HARQ response bits included in the dynamic codebook can be less than the number of HARQ response bits included in the semi-static codebook.

[0164] When using the dynamic codebook, in order to identify for which data (e.g., PDSCH or PSSCH) the HARQ response bits are ACK / NACK, the counter downlink assignment index (cDAI) and / or the total downlink assignment index (tDAI) can be used. The cDAI and tDAI can be included in the control information (e.g., DCI, SCI). In Figure 9 the (x, y) shown, x can be the cDAI and y can be the tDAI. The cDAI and tDAI can be configured considering not only the downlink TB (e.g., PDSCH) but also the sidelink TB (e.g., PSSCH).

[0165] The index of the TB sent through Carrier #0 in Slot #0 can be 0, and the index of the TB sent through Carrier #2 in Slot #0 can be 1. The cDAI can be incremented by 1. The tDAI can be configured in slot units. The tDAI can be configured as the maximum index among the indexes of the TBs sent in the corresponding slot. In other words, the tDAI can be configured as the maximum value of the cDAI in the corresponding slot. The tDAI can be set to 1 in Slot #0, and the tDAI can be set to 3 in Slot #1. The tDAI can be used to indicate the total number of downlink allocations from the first slot to the current slot within the transmission interval. The sidelink allocation can be included in the total number of downlink allocations. Therefore, the SL HARQ response can be multiplexed with the DL HARQ response in the HARQ-ACK codebook (e.g., dynamic codebook).

[0166] The HARQ-ACK codebook can include 8 HARQ response bits and can be transmitted via PUCCH (or PUSCH). The counter sidelink assignment index (cSAI) and the total sidelink assignment index (tSAI) for the SL HARQ response can be configured. The cSAI and tSAI can operate independently of the cDAI and tDAI. Even in this case, the SL HARQ response can be multiplexed with the DL HARQ response within one codebook, and this one codebook can be transmitted to the base station via PUCCH. The SL HARQ response can be concatenated after the DL HARQ response within one codebook. Alternatively, the DL HARQ response can be concatenated after the SL HARQ response within one codebook.

[0167] In Table 15 below, the SL HARQ response can be (NACK, NACK, ACK). The dynamic codebook may not include HARQ response bits for non-scheduled resources. Therefore, the size of the SL HARQ response can be 3 bits. The first NACK in the SL HARQ response can be a type 1 NACK (i.e., N1). The second NACK in the SL HARQ response can be a type 2 NACK (i.e., N2).

[0168] [Table 15]

[0169] Carrier #2 (SL) N1 N2 A

[0170] To indicate N2 in Table 15, the indication bit can be configured as shown in Tables 16 to 18 below. In Table 16, the indication bit for N2 can be set to 1. In this case, the HARQ-ACK codebook can include 1 bit as the indication bit for N2.

[0171] [Table 16]

[0172] Carrier #2 (SL) N / A 1 N / A

[0173] In Table 17, the indication bit for N2 for the scheduled resource can be set to 1, and the indication bit for N1 for the scheduled resource can be set to 0. In this case, the HARQ-ACK codebook can include 2 bits (e.g., the indication bit for N2 + the indication bit for N1). The HARQ-ACK codebook may not include the indication bit for ACK for the scheduled resource.

[0174] [Table 17]

[0175] Carrier #2 (SL) 0 1 N / A

[0176] In Table 18, the indication bit for N2 of the scheduling resource can be set to 1, the indication bit for N1 of the scheduling resource can be set to 0, and the indication bit for ACK of the scheduling resource can be set to 0. In this case, the HARQ-ACK codebook can include 3 bits (e.g., the indication bit for N2 + the indication bit for N1 + the indication bit for ACK).

[0177] [Table 18]

[0178] Carrier #2 (SL) 0 1 0

[0179] The position of N2 for multiple scheduling resources may not be recognizable. To identify the position of N2, additional information can be sent.

[0180] The method according to the present invention can be implemented as program instructions executable by various computers and recorded on a computer-readable medium. The computer-readable medium can include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the computer-readable medium can be designed and configured specifically for the present invention or can be known and available to those skilled in the computer software field.

[0181] Examples of computer-readable media can include hardware devices such as ROM, RAM, and flash memory that are specifically configured to store and execute program instructions. Examples of program instructions include, for example, machine code generated by a compiler and high-level language code executable by a computer using an interpreter. The above hardware devices can be configured to operate as at least one software module to perform the operations of the present invention, and vice versa.

[0182] Although the above has been described in detail with reference to the embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention.

Claims

1. A method for operating a first terminal in a communication system, comprising: Receiving, from a base station, downlink control information (DCI) for scheduling sidelink transmission, the DCI including a counter sidelink allocation index (cSAI); Sending sidelink control information (SCI) to a second terminal, the SCI including a redundancy version (RV); Sending first sidelink data to the second terminal based on the DCI and the SCI; Receiving, from the second terminal, a first sidelink hybrid automatic repeat request response (first SL HARQ response) for the first sidelink data through a physical sidelink feedback channel (PSFCH); and Sending, at a feedback timing indicated by first information included in the DCI, a HARQ-ACK codebook including the first SL HARQ response to the base station through a physical uplink control channel (PUCCH), wherein the cSAI is used to identify the first sidelink data associated with the first SL HARQ in the HARQ-ACK codebook, in response to the first sidelink data being retransmitted data due to the second terminal not receiving the first sidelink data, the RV included in the SCI is different from the RV associated with the first sidelink data not received by the second terminal, and in response to the first sidelink data being retransmitted data due to the first terminal not sending the first sidelink data, the RV included in the SCI is the same as the RV associated with the first sidelink data not sent by the first terminal.

2. The method for operating the first terminal according to claim 1, further comprising: Receiving, from the base station, a high-layer message including information indicating one or more feedback timings, wherein the first information included in the DCI indicates one of the one or more feedback timings.

3. The method for operating the first terminal according to claim 1, wherein the feedback timing indicates a time gap between the PSFCH and the PUCCH.

4. The method for operating the first terminal according to claim 1, wherein the DCI further includes resource allocation information for the first sidelink data, and the first sidelink data is sent on a physical sidelink shared channel (PSSCH) indicated by the resource allocation information.

5. The method for operating the first terminal according to claim 1, further comprising: Sending sidelink control information (SCI) including resource allocation information for the first sidelink data to the second terminal, wherein the first sidelink data is sent on a physical sidelink shared channel (PSSCH) indicated by the resource allocation information.

6. The method for operating the first terminal according to claim 1, wherein the HARQ-ACK codebook further includes a downlink HARQ response (DL HARQ response) for downlink data received from the base station.

7. The method for operating the first terminal according to claim 1, further comprising: Send the second sidelink data to the second terminal; and Receive a second SL HARQ response for the second sidelink data from the second terminal, wherein the HARQ-ACK codebook further includes the second SL HARQ response.

8. A first terminal in a communication system, comprising: A processor; and A memory storing at least one instruction executed by the processor, wherein the at least one instruction is executed to: Receive downlink control information (DCI) for scheduling sidelink transmission from a base station, the DCI including a counter sidelink allocation index (cSAI); Send sidelink control information (SCI) including a redundancy version (RV) to a second terminal; Send first sidelink data to the second terminal based on the DCI and the SCI; Receive a first sidelink hybrid automatic repeat request response (first SL HARQ response) for the first sidelink data from the second terminal via a physical sidelink feedback channel (PSFCH); and Send a HARQ-ACK codebook including the first SL HARQ response to the base station via a physical uplink control channel (PUCCH) at a feedback timing indicated by first information included in the DCI, wherein the cSAI is used to identify the first sidelink data associated with the first SL HARQ in the HARQ-ACK codebook, In response to the first sidelink data being retransmitted data due to the second terminal not receiving the first sidelink data, the RV included in the SCI is different from the RV associated with the first sidelink data not received by the second terminal, and In response to the first sidelink data being retransmitted data due to the first terminal not sending the first sidelink data, the RV included in the SCI is the same as the RV associated with the first sidelink data not sent by the first terminal.

9. The first terminal according to claim 8, wherein The at least one instruction is further executed to receive a high-layer message from the base station including information indicating one or more feedback timings, wherein the first information included in the DCI indicates one of the one or more feedback timings.

10. The first terminal according to claim 8, wherein The feedback timing indicates a time gap between the PSFCH and the PUCCH.

11. The first terminal according to claim 8, wherein The DCI further includes resource allocation information for the first sidelink data, and the first sidelink data is sent on a physical sidelink shared channel (PSSCH) indicated by the resource allocation information.

12. The first terminal according to claim 8, wherein The at least one instruction is further executed to send sidelink control information (SCI) including resource allocation information for the first sidelink data to the second terminal, Among them, the first sidelink data is sent on a physical sidelink shared channel (PSSCH) indicated by the resource allocation information.

13. The first terminal according to claim 8, wherein, The HARQ-ACK codebook further includes a downlink HARQ response (DL HARQ response) for downlink data received from the base station.

14. The first terminal according to claim 8, wherein the at least one instruction is further executed to: send second sidelink data to the second terminal; and receive a second SL HARQ response from the second terminal for the second sidelink data, wherein the HARQ-ACK codebook further includes the second SL HARQ response.

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