Method and apparatus for retransmission in sidelink communication

Abstract

Disclosed are a method and apparatus for retransmission in sidelink communication. An operation method of a transmitting terminal includes the steps of: transmitting first data to a receiving terminal based on a first retransmission scheme; switching a retransmission scheme from the first retransmission scheme to a second retransmission scheme when a preset condition is satisfied; and transmitting second data to the receiving terminal based on the second retransmission scheme.

Description

Technical Field

[0001] This disclosure relates to a sidelink communication technique, and more specifically, to a technique for retransmitting data in sidelink communication. Background Technology

[0002] To handle the surge in wireless data following the commercialization of fourth-generation (4G) communication systems (e.g., Long Term Evolution (LTE) and LTE-Advanced (LTE-A) systems), fifth-generation (5G) communication systems (e.g., New Radio (NR) systems) are being considered, utilizing both 4G frequency bands (e.g., below 6 GHz) and higher frequency bands (e.g., above 6 GHz). 5G systems can support Enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low-Latency Communication (URLLC), and Massive Machine-Type Communication (mMTC), among others.

[0003] 4G 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 and 5G 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, and so on.

[0004] In cellular communication systems, V2X communication (e.g., C-V2X communication) can be performed based on sidelink communication technologies (e.g., proximity-based service (ProSe) communication, device-to-device (D2D) communication, etc.). For example, a sidelink channel can be established for vehicles participating in V2V communication, and this sidelink channel can be used for communication between vehicles. Configured grant (CG) resources can be used to perform sidelink communication. CG resources can be configured periodically, and they can be used to send periodic data (e.g., periodic sidelink data).

[0005] On the other hand, data retransmission procedures can be executed in sidelink communication. These procedures can be implemented based on various schemes. In this case, different operational methods for different retransmission schemes are required in sidelink communication. Summary of the Invention

[0006] Technical issues

[0007] The purpose of this disclosure in order to solve the above problems is to provide a method and apparatus for retransmitting data in sidelink communication.

[0008] Technical solution

[0009] According to a first exemplary embodiment of the present disclosure for achieving the purpose, an operation method of a transmitting terminal may include: transmitting first data to a receiving terminal based on a first retransmission scheme; switching the retransmission scheme from the first retransmission scheme to a second retransmission scheme in response to satisfying a pre-configuration condition; and transmitting second data to the receiving terminal based on the second retransmission scheme, wherein the first retransmission scheme and the second retransmission scheme are distinguished based on whether a Hybrid Automatic Repeat Request (HARQ) feedback is sent.

[0010] Pre-configured conditions can be configured from the base station via higher-layer signaling.

[0011] The pre-configuration conditions can be met when the negative acknowledgment (NACK) of the first data occurs more than n times, or when the channel state between the transmitting terminal and the receiving terminal meets the baseline, where n is a natural number.

[0012] The operation method of the transmitting terminal may further include sending a first indicator to the receiving terminal to indicate the switching of the retransmission scheme, wherein the transmission of second data is performed after the first indicator is sent.

[0013] The first indicator may be included in the first-stage side link control information (SCI) or the second-stage SCI sent from the sending terminal to the receiving terminal.

[0014] The operation method of the transmitting terminal may further include sending a second indicator to the base station indicating that the retransmission scheme has been switched when the retransmission scheme is switched.

[0015] The operation method of the transmitting terminal may further include: sending a third indicator to the base station requesting a switchover retransmission scheme; and receiving a fourth indicator from the base station approving the switchover retransmission scheme, wherein the retransmission scheme is switched upon receiving the fourth indicator.

[0016] The operation method of the transmitting terminal may further include receiving a fifth indicator from the base station requesting a switch of the retransmission scheme, wherein the retransmission scheme is switched upon receiving the fifth indicator.

[0017] Retransmission schemes can be switched on a per-transmission block (TB), per-code block group (CBG), or per-HARQ procedure.

[0018] When the first retransmission scheme is a HARQ retransmission scheme, the second retransmission scheme can be a blind retransmission scheme; when the first retransmission scheme is a blind retransmission scheme, the second retransmission scheme can be a HARQ retransmission scheme; when using the HARQ retransmission scheme, HARQ feedback can be sent; and when using the blind retransmission scheme, HARQ feedback can be omitted.

[0019] According to a second exemplary embodiment of the present disclosure for achieving the purpose, an operation method of a receiving terminal may include: receiving first data from a transmitting terminal based on a first retransmission scheme; receiving a first indicator from the transmitting terminal indicating a switch to a retransmission scheme; and receiving second data from the transmitting terminal based on a second retransmission scheme, wherein the first retransmission scheme and the second retransmission scheme are distinguished based on whether a Hybrid Automatic Repeat Request (HARQ) feedback is sent.

[0020] The first indicator may be included in the first-stage side link control information (SCI) or the second-stage SCI sent from the sending terminal to the receiving terminal.

[0021] The operation method of the receiving terminal may further include: determining that the second retransmission scheme has been switched to the first retransmission scheme in response to the fulfillment of the pre-configuration conditions; and receiving third data from the sending terminal based on the first retransmission scheme.

[0022] Pre-configured conditions can be configured from the base station via higher-layer signaling.

[0023] The pre-configuration conditions can be met when the negative acknowledgment (NACK) of the second data occurs more than n times, or when the channel state between the sending terminal and the receiving terminal meets the baseline, where n is a natural number.

[0024] When the first retransmission scheme is a HARQ retransmission scheme, the second retransmission scheme can be a blind retransmission scheme; when the first retransmission scheme is a blind retransmission scheme, the second retransmission scheme can be a HARQ retransmission scheme; when using the HARQ retransmission scheme, HARQ feedback can be sent; and when using the blind retransmission scheme, HARQ feedback can be omitted.

[0025] According to a third exemplary embodiment of this disclosure for achieving the purpose, a transmitting terminal may include: a processor; and a memory storing one or more instructions executable by the processor, wherein the one or more instructions are executed to perform: transmitting first data to a receiving terminal based on a first retransmission scheme; switching the retransmission scheme from the first retransmission scheme to a second retransmission scheme in response to satisfying a pre-configuration condition; and transmitting second data to the receiving terminal based on the second retransmission scheme, wherein the first retransmission scheme and the second retransmission scheme are distinguished based on whether a Hybrid Automatic Repeat Request (HARQ) feedback is sent.

[0026] The first indicator may be included in the first-stage side link control information (SCI) or the second-stage SCI sent from the sending terminal to the receiving terminal.

[0027] More than one instruction can be further executed: when the retransmission scheme is switched, a second indicator indicating that the retransmission scheme has been switched is sent to the base station.

[0028] More than one instruction can be further executed to perform: sending a third indicator to the base station requesting a handover retransmission scheme; and receiving a fourth indicator from the base station approving the handover retransmission scheme, wherein the retransmission scheme is switched upon receiving the fourth indicator.

[0029] Beneficial effects

[0030] According to this disclosure, the transmitting terminal can send data to the receiving terminal based on a first retransmission scheme, switch the first retransmission scheme to a second retransmission scheme, and then send data to the receiving terminal based on the second retransmission scheme. The switching of the retransmission scheme can be reported to the base station and / or the receiving terminal. The retransmission scheme can be switched when pre-configured conditions are met. Therefore, in sidelink communication, the retransmission scheme can be switched effectively, and the performance of the communication system can be improved. Attached Figure Description

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

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

[0033] Figure 3 This is a block diagram illustrating a first exemplary embodiment of a communication node constituting a cellular communication system.

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

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

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

[0037] Figure 7 This is a sequence diagram illustrating a first exemplary embodiment of a retransmission method based on a HARQ retransmission scheme in sidelink communication.

[0038] Figure 8 This is a sequence diagram illustrating a first exemplary embodiment of a retransmission method based on a blind retransmission scheme in sidelink communication.

[0039] Figure 9 This is a sequence diagram illustrating a first exemplary embodiment of a switching method for a retransmission scheme in sidelink communication.

[0040] Figure 10 This is a sequence diagram illustrating a second exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0041] Figure 11 This is a sequence diagram illustrating a third exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0042] Figure 12 This is a sequence diagram illustrating a fourth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0043] Figure 13 This is a sequence diagram illustrating a fifth exemplary embodiment of a switching method for a retransmission scheme in sidelink communication.

[0044] Figure 14 This is a sequence diagram illustrating a sixth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0045] Figure 15 This is a sequence diagram illustrating a seventh exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0046] Figure 16 This is a sequence diagram illustrating an eighth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0047] Figure 17This is a sequence diagram illustrating a ninth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0048] Figure 18 This is a sequence diagram illustrating a tenth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0049] Figure 19 This is a sequence diagram illustrating an eleventh exemplary embodiment of a switching method for retransmission schemes in sidelink communication. Detailed Implementation

[0050] While the invention may have various modifications and alternatives, specific embodiments are shown by way of example and described in detail in the accompanying drawings. However, it should be understood that this description is not intended to limit the invention to the specific embodiments, but rather, the invention is to encompass all modifications, equivalents, and alternatives that fall within the spirit and scope of the invention.

[0051] Although the terms “first,” “second,” etc., may be used herein to refer to various components, these components should not be construed as being limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be referred to as a second component, and a second component may be referred to as a first component, without departing from the scope of the invention. The term “and / or” includes any and all combinations of one or more of the related listed items.

[0052] What will be understood is that when a component is referred to as "connected" or "linked" to another component, that component can be directly connected to or linked to the other component, or there may be an intermediate component. Conversely, when a component is referred to as "directly connected" or "directly linked" to another component, there is no intermediate component.

[0053] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that, when used herein, the terms “comprising,” “including,” “containing,” and / or “comprising” specify the presence of the stated feature, integer, step, operation, component, part, and / or combination thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, parts, and / or combinations thereof.

[0054] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will be further understood that terms defined in general dictionaries shall be interpreted as having the same meaning as they have in the context of the relevant art, and shall not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0055] Preferred exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In describing the invention, for ease of overall understanding, the same reference numerals are used throughout the description of the drawings to refer to the same components, and repeated descriptions will be omitted.

[0056] Figure 1 This is a conceptual diagram illustrating a V2X communication scenario.

[0057] like Figure 1 As shown, 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. V2X communication can be supported by a cellular communication system (e.g., cellular communication network 140), and V2X communication supported by cellular communication system 140 can be referred to as "cellular-V2X (C-V2X) communication." Here, cellular communication system 140 can include 4G communication systems (e.g., LTE communication systems or LTE-A communication systems), 5G communication systems (e.g., NR communication systems), etc.

[0058] V2V communication can refer to 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 #1 100). Various driving information, such as speed, heading, time, and location, can be exchanged between vehicles 100 and 110 via V2V communication. Autonomous driving (e.g., platooning) can be supported based on the driving information exchanged via V2V communication. V2V communication supported in the cellular communication system 140 can be performed based on "sidelink" communication technologies (e.g., ProSe and D2D communication technologies). In this case, communication between vehicles 100 and 110 can be performed using at least one sidelink channel established between vehicles 100 and 110.

[0059] V2I communication can refer to communication between vehicle #1 100 and roadside infrastructure (e.g., roadside unit (RSU)) 120. Infrastructure 120 may include traffic lights or streetlights located on the roadside. For example, when performing V2I communication, communication can be performed between communication nodes located in vehicle #1 100 and communication nodes located in traffic lights. Traffic information, driving information, etc., can be exchanged between vehicle #1 100 and infrastructure 120 via V2I communication. V2I communication supported in cellular communication system 140 can also be performed based on sidelink communication technologies (e.g., ProSe communication technology and D2D communication technology). In this case, a sidelink channel can be used to perform communication between vehicle #1 100 and infrastructure 120.

[0060] V2P communication can represent communication between vehicle #1 100 (e.g., a communication node located in vehicle #1 100) and person 130 (e.g., a communication node carried by person 130). Driving information of vehicle #1 100 and motion information of person 130, such as speed, direction, time, and position, can be exchanged between vehicle #1 100 and person 130 via V2P communication. The communication node located in vehicle #1 100 or the communication node carried by person 130 can determine dangerous situations based on the obtained driving and motion information, thereby generating a warning indicating danger. V2P communication supported in cellular communication system 140 can be performed based on sidelink communication technology (e.g., ProSe communication technology and D2D communication technology). In this case, a sidelink channel can be used to perform communication between the communication node located in vehicle #1 100 or the communication node carried by person 130.

[0061] V2N communication can refer to communication between vehicle #1 100 (e.g., a communication node located in vehicle #1 100) and cellular communication system 140 (e.g., a cellular communication network). V2N communication can be performed based on 4G communication technologies (e.g., LTE or LTE-A as specified in the 3GPP standard) or 5G communication technologies (e.g., NR as specified in the 3GPP standard). Furthermore, V2N communication can be performed based on communication technologies defined in IEEE 802.11 (e.g., Wireless Access in Vehicular Environments (WAVE) communication technology, Wireless Local Area Network (WLAN) communication technology, etc.) and communication technologies defined in IEEE 802.15 (e.g., Wireless Personal Area Network (WPAN) communication technology, etc.).

[0062] On the other hand, the cellular communication system 140 that supports V2X communication can be configured as follows.

[0063] Figure 2 This is a conceptual diagram illustrating a first exemplary embodiment of a cellular communication system.

[0064] like Figure 2 As shown, a cellular communication system may include an access network, a core network, etc. The access network may include base station 210, repeater 220, user equipment (UE) 231 to 236, etc. UE 231 to 236 may include components located at... Figure 1 The communication nodes in vehicles 100 and 110, located Figure 1 Communication nodes in infrastructure 120 Figure 1 Personnel 130 carry communication nodes, 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.

[0065] When a cellular communication system supports 5G communication technology, the core network may include User Plane Function (UPF) 250, Session Management Function (SMF) 260, Access and Mobility Management Function (AMF) 270, etc. Alternatively, when the cellular communication system operates in Non-Stand Alone (NSA) mode, the core network consisting of S-GW 250, P-GW 260, and MME 270 can support both 4G and 5G communication technologies, while the core network consisting of UPF 250, SMF 260, and AMF 270 can support both 5G and 4G communication technologies.

[0066] Furthermore, when a cellular communication system supports network slicing technology, the core network can be divided into multiple logical network slices. For example, network slices that support V2X communication can be configured (e.g., V2V network slices, V2I network slices, V2P network slices, V2N network slices, etc.), and V2X communication can be supported through V2X network slices configured in the core network.

[0067] Communication nodes constituting a cellular communication system (e.g., base stations, repeaters, UEs, S-GW, P-GW, MME, UPF, SMF, AMF, etc.) can perform communication by utilizing at least one of the following communication technologies: Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiplexing (OFDM), Filtered OFDM, Single-Carrier FDMA (SC-FDMA), Non-Orthogonal Multiple Access (NOMA), Generalized Frequency Division Multiplexing (GFDM), and Filter Bank Multicarrier. Multi-Carrier (FBMC) technology, Universal Filtered Multi-Carrier (UFMC) technology, and Space Division Multiple Access (SDMA) technology.

[0068] The communication nodes that constitute a cellular communication system (e.g., base stations, repeaters, UEs, S-GWs, P-GWs, MMEs, UPFs, SMFs, AMFs, etc.) can be configured as follows.

[0069] Figure 3 This is a block diagram illustrating a first exemplary embodiment of a communication node constituting a cellular communication system.

[0070] like Figure 3 As shown, 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. Furthermore, 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 can be connected and communicate with each other via a bus 370.

[0071] However, the components included in communication node 300 can be connected to processor 310 via separate interfaces or separate buses instead of the common bus 370. For example, processor 310 can be connected via dedicated interfaces to at least one of memory 320, transceiver 330, input interface device 340, output interface device 350, and storage device 360.

[0072] Processor 310 can execute program instructions stored in at least one of memory 320 and storage device 360. Processor 310 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor that performs methods according to embodiments of the present disclosure. Each of memory 320 and storage device 360 ​​may include at least one of volatile storage media and non-volatile storage media. For example, memory 320 may include at least one of read-only memory (ROM) and random access memory (RAM).

[0073] Refer again Figure 2 In the communication system, base station 210 can form a macro cell or a small cell, and can connect to the core network via ideal backhaul or non-ideal backhaul. Base station 210 can transmit signals received from the core network to UEs 231 to 236 and repeater 220, and can also transmit signals received from UEs 231 to 236 and repeater 220 to the core network. UEs #1 231, UE #2 232, UE #4 234, UE #5 235, and UE #6 236 can be within the cell coverage area of ​​base station 210. UEs #1 231, UE #2 232, UE #4 234, UE #5 235, and UE #6 236 can connect to base station 210 by performing a connection establishment procedure with the base station. UE#1 231, UE#2 232, UE#4 234, UE#5 235 and UE#6 236 can communicate with base station 210 after connecting to base station 210.

[0074] Repeater 220 can be connected to base station 210 and can relay communication between base station 210 and UE#3 233 and UE#4 234. That is, repeater 220 can send signals received from base station 210 to UE#3 233 and UE#4 234, and can also send signals received from UE#3 233 and UE#4 234 to base station 210. UE#4 234 can be within the cell coverage area of ​​both base station 210 and repeater 220, while UE#3 233 can be within the cell coverage area of ​​repeater 220. That is, UE#3 233 can be located outside the cell coverage area of ​​base station 210. UE#3 233 and UE#4 234 can connect to repeater 220 by performing a connection establishment procedure. UE#3 233 and UE#4 234 can communicate with repeater 220 after connecting to it.

[0075] Base station 210 and repeater 220 can support multiple-input multiple-output (MIMO) technologies (e.g., single-user (SU)-MIMO, multi-user (MU)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) communication technologies, carrier aggregation (CA) communication technologies, unlicensed band communication technologies (e.g., licensed assisted access (LAA), enhanced LAA (eLAA), etc.), and sidelink communication technologies (e.g., ProSe communication technologies, D2D communication technologies). UE#1 231, UE#2 232, UE#5 235, and UE#6 236 can perform operations corresponding to base station 210 and operations supported by base station 210. UE#3 233 and UE#4 234 can perform operations corresponding to repeater 220 and operations supported by repeater 220.

[0076] Here, base station 210 can be referred to as Node B (NB), Evolved Node B (eNB), Base Transceiver Station (BTS), Radio Remote Head (RRH), Transmission Reception Point (TRP), Radio Unit (RU), Roadside Unit (RSU), Radio Transceiver, Access Point, Access Node, etc. Repeater 220 can be referred to as small base station, relay node, etc. Each of UE#1 231 to UE#6 236 can be referred to as terminal, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, On-Broad Unit (OBU), etc.

[0077] On the other hand, 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). Sidelink communication can be performed based on a one-to-one scheme or a one-to-many scheme. When using sidelink communication technology to perform V2V communication, UE#5 235 can be located at... Figure 1 The communication node in vehicle #1 100, UE #6 236 can be located in Figure 1 The communication node in vehicle #2 110. When performing V2I communication using sidelink communication technology, UE #5 235 can be located in Figure 1 The communication node in vehicle #1 100, UE #6 236 can be located in Figure 1 The communication node in infrastructure 120. When performing V2P communication using sidelink communication technology, UE#5 235 can be located in Figure 1 The communication node in vehicle #1100, UE#6 236 can be Figure 1 The personnel numbered 130 and carried communication nodes.

[0078] Based on the location of the UEs participating in sidelink communication (e.g., UE#5 235 and UE#6 236), the application sidelink communication scenarios can be classified as shown in Table 1 below. For example, Figure 2 The sidelink communication scenario between UE#5 235 and UE#6 236 shown can be sidelink communication scenario #C.

[0079] [Table 1]

[0080] Side link communication scenarios Location of UE#5 235 Location of UE#6 236 A Outside the coverage area of ​​base station 210 Outside the coverage area of ​​base station 210 B Within the coverage area of ​​base station 210 Outside the coverage area of ​​base station 210 C Within the coverage area of ​​base station 210 Within the coverage area of ​​base station 210 D Within the coverage area of ​​base station 210 Within the coverage area of ​​base station 210

[0081] On the other hand, the user plane protocol stack of the UE performing sidelink communication (e.g., UE#5 235 and UE#6 236) can be configured as follows.

[0082] Figure 4 This is a block diagram illustrating a first exemplary embodiment of the user plane protocol stack of a UE performing sidelink communication.

[0083] like Figure 4 As shown, UE#5 235 can be Figure 2 The UE#5 235 and UE#6 236 shown can be Figure 2 The example shown is UE#6 236. The sidelink communication scenario between UE#5 235 and UE#6 236 can be one of the sidelink communication scenarios #A to #D in Table 1. The user plane protocol stack of each of UE#5 235 and UE#6 236 may 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.

[0084] Sidelink communication between UE#5 235 and UE#6 236 can be performed using the PC5 interface (e.g., the PC5-U interface). Layer 2 identifiers (IDs) (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. Furthermore, hybrid Automatic Repeat Request (HARQ) feedback operations can be supported in sidelink communication, and RLC Acknowledged Mode (RLC AM) or RLC Unacknowledged Mode (RLC UM) can be supported.

[0085] On the other hand, the control plane protocol stack of the UE performing sidelink communication (e.g., UE#5 235 and UE#6 236) can be configured as follows.

[0086] Figure 5 This is a block diagram illustrating a first exemplary embodiment of the control plane protocol stack of a UE performing sidelink communication. Figure 6 This is a block diagram illustrating a second exemplary embodiment of the control plane protocol stack of a UE performing sidelink communication.

[0087] like Figure 5 and Figure 6 As shown, UE#5 235 can be Figure 2The UE#5 235 and UE#6 shown can be Figure 2 The sidelink communication scenario between UE#6 236 and UE#5 235 can be one of the sidelink communication scenarios #A to #D in Table 1. Figure 5 The control plane protocol stack shown can be a control plane protocol stack used for sending and receiving broadcast information (e.g., Physical Sidelink Broadcast Channel, PSBCH)).

[0088] Figure 5 The control plane protocol stack shown may include a PHY layer, a MAC layer, an RLC layer, and a Radio Resource Control (RRC) layer. Sidelink communication between UE#5 235 and UE#6 236 can be performed using a PC5 interface (e.g., a PC5-C interface). Figure 6 The control plane protocol stack shown can be a control plane protocol stack used for one-to-one side link communication. Figure 6 The control plane protocol stack shown may include the PHY layer, MAC layer, RLC layer, PDCP layer, and PC5 signaling protocol layer.

[0089] On the other hand, the channels used in sidelink communication between UE#5 235 and UE#6 236 may include the Physical Sidelink Shared Channel (PSSCH), the Physical Sidelink Control Channel (PSCCH), the Physical Sidelink Discovery Channel (PSDCH), and the Physical Sidelink Broadcast Channel (PSBCH). The PSSCH can be used to send and receive sidelink data and can be configured in the UE (e.g., UE#5 235 or UE#6 236) via higher-layer signaling. The PSCCH can be used to send and receive sidelink control information (SCI) and can also be configured in the UE (e.g., UE#5 235 or UE#6 236) via higher-layer signaling.

[0090] PSDCH can be used in the discovery process. For example, a discovery signal can be sent via PSDCH. PSBCH can be used to send and receive broadcast information (e.g., system information). Furthermore, demodulation reference signals (DMRS), synchronization signals, etc., can be used in sidelink communication between UE#5 235 and UE#6 236. Synchronization signals can include the primary sidelink synchronization signal (PSSS) and the secondary sidelink synchronization signal (SSSS).

[0091] On the other hand, the side link transmission modes (TM) can be classified as side link TM#1 to TM#4 as shown in Table 2 below.

[0092] [Table 2]

[0093]

[0094]

[0095] 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 base station 210 to perform sidelink communication. The resource pool can be configured for each item in the sidelink control information and sidelink data.

[0096] The resource pool for sidelink control information can be configured based on RRC signaling procedures (e.g., dedicated RRC signaling procedures, broadcast RRC signaling procedures). The resource pool for receiving sidelink control information can be configured via a broadcast RRC signaling procedure. When sidelink TM#3 is supported, the resource pool for sending sidelink control information can be configured via a dedicated RRC signaling procedure. In this case, sidelink control information can be sent using resources scheduled by base station 210 within the resource pool configured by the dedicated RRC signaling procedure. When sidelink TM#4 is supported, the resource pool for sending sidelink control information can be configured via either a dedicated RRC signaling procedure or a broadcast RRC signaling procedure. In this case, sidelink control information can be sent using resources autonomously selected by the UE (e.g., UE#5235 or UE#6236) within the resource pool configured by the dedicated RRC signaling procedure or the broadcast RRC signaling procedure.

[0097] When sidelink TM#3 is supported, a resource pool for transmitting and receiving sidelink data does not need to be configured. In this case, sidelink data can be transmitted and received using resources scheduled by base station 210. When sidelink TM#4 is supported, a resource pool for transmitting and receiving sidelink data can be configured using a dedicated RRC signaling procedure or a broadcast RRC signaling procedure. In this case, sidelink data can be transmitted and received using resources autonomously selected by the UE (e.g., UE#5 235 or UE#6 236) from the resource pool configured by the RRC signaling procedure or the broadcast RRC signaling procedure.

[0098] The following describes a sidelink communication method based on Discontinuous Reception (DRX) operation. Even when describing a method (e.g., signal transmission or reception) to be performed at a first communication node, the corresponding second communication node can also perform a method (e.g., signal reception or transmission) corresponding to the method performed at the first communication node. That is, when describing the operation of UE#1 (e.g., vehicle #1), its corresponding UE#2 (e.g., vehicle #2) can perform an operation corresponding to the operation of UE#1. Conversely, when describing the operation of UE#2, the corresponding UE#1 can perform an operation corresponding to the operation of UE#2. In the exemplary embodiments described below, the operation of the vehicle can be the operation of a communication node located in the vehicle.

[0099] In an exemplary embodiment, signaling can be one or a combination of two or more of higher-layer signaling, MAC signaling, and physical (PHY) signaling. Messages used for higher-layer signaling can be referred to as "high-layer messages" or "high-layer signaling messages." Messages used for MAC signaling can be referred to as "MAC messages" or "MAC signaling messages." Messages used for PHY signaling can be referred to as "PHY messages" or "PHY signaling messages." Higher-layer signaling can refer to the operation of sending and receiving system information (e.g., Master Information Block (MIB), System Information Block (SIB)) and / or RRC messages. MAC signaling can refer to the operation of sending and receiving MAC control elements (CE). PHY signaling can refer to the operation of sending and receiving control information (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI), or SCI).

[0100] Sidelink signals can be synchronization signals and reference signals used for sidelink communication. For example, synchronization signals can be Synchronization Signal / Physical Broadcast Channel (SS / PBCH) blocks, Sidelink Synchronization Signals (SLSS), Primary Sidelink Synchronization Signals (PSSS), Secondary Sidelink Synchronization Signals (SSSS), etc. Reference signals can be Channel State Information-Reference Signals (CSI-RS), DMRS, Phase Tracking-Reference Signals (PT-RS), Cell Specific Reference Signals (CRS), Sounding Reference Signals (SRS), Discovery Reference Signals (DRS), etc.

[0101] Sidelink channels can be PSSCH, PSCCH, PSDCH, PSBCH, Physical Sidelink Feedback Channel (PSFCH), etc. Additionally, a sidelink channel can refer to a sidelink channel that includes sidelink signals mapped to specific resources within the corresponding sidelink channel. Sidelink communication can support broadcast, multicast, and unicast services.

[0102] Sidelink communication can be performed using either a single SCI scheme or a multi-SCI scheme. When using a single SCI scheme, it can be based on one SCI (e.g., Phase 1 SCI (1...)). st -stage SCI) is used to perform data transmission (e.g., sidelink data transmission, sidelink-shared channel (SL-SCH) transmission). When using a multi-SCI scheme, two SCIs can be used (e.g., stage 1 SCI and stage 2 SCI). nd Data transmission is performed using a stage SCI. SCIs can be transmitted via PSCCH and / or PSSCH. When using a single SCI scheme, SCIs can be transmitted on the PSCCH (e.g., stage 1 SCI). When using a multi-SCI scheme, stage 1 SCIs can be transmitted on the PSCCH, and stage 2 SCIs can be transmitted on either the PSCCH or PSSCH. A stage 1 SCI can be referred to as "stage 1 SCI," and a stage 2 SCI can be referred to as "stage 2 SCI." The format of a stage 1 SCI can include SCI format 1-A, and the format of a stage 2 SCI can include SCI format 2-A and SCI format 2-B.

[0103] The first-stage SCI may include one or more of the following information elements: priority information, frequency resource allocation information, time resource allocation information, resource reservation period information, demodulation reference signal (DMRS) mode information, second-stage SCI format information, beta_offset indicator, number of DMRS ports, and modulation and coding scheme (MCS) information. The second-stage SCI may include one or more of the following information elements: HARQ processor identifier (ID), redundancy version (RV), source ID, destination ID, CSI request information, area ID, and communication range requirements.

[0104] On the other hand, data can be retransmitted in sidelink communication. Data (e.g., sidelink (SL) data) can be retransmitted based on a HARQ retransmission scheme or a blind retransmission scheme. The HARQ retransmission scheme may be referred to as the first retransmission scheme, and the blind retransmission scheme may be referred to as the second retransmission scheme. Alternatively, the HARQ retransmission scheme may be referred to as the second retransmission scheme, and the blind retransmission scheme may be referred to as the first retransmission scheme. When using the HARQ retransmission scheme, data can be retransmitted even if a negative acknowledgment (NACK) or discontinuous transmission (DTX) occurs. Using the HARQ retransmission scheme may mean that HARQ feedback is enabled. When using the blind retransmission scheme, data can be retransmitted regardless of the HARQ feedback (e.g., NACK or DTX). Using the blind retransmission scheme may mean that HARQ feedback is disabled.

[0105] Sidelink communication can support HARQ retransmission schemes and / or blind retransmission schemes. For example, a HARQ retransmission scheme can be used in sidelink communication, and the retransmission scheme can be switched from HARQ retransmission scheme to blind retransmission scheme when pre-configuration conditions (e.g., trigger conditions) are met. Alternatively, a blind retransmission scheme can be used in sidelink communication, and the retransmission scheme can be switched from blind retransmission scheme to HARQ retransmission scheme when pre-configuration conditions (e.g., trigger conditions) are met. The switching of retransmission schemes can be performed on a data, transport block (TB), code block group (CBG), or HARQ procedure basis.

[0106] Figure 7 This is a sequence diagram illustrating a first exemplary embodiment of a retransmission method based on a HARQ retransmission scheme in sidelink communication.

[0107] like Figure 7 As shown, a communication system may include a transmitting terminal and a receiving terminal. A transmitting terminal may refer to a terminal that transmits SL data, while a receiving terminal may refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5 235 shown is shown, and the receiving terminal can be... Figure 2The UE#6 236 shown is an example. Each of the transmitting and receiving terminals can be configured to work with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0108] Prior to step S701, configuration information for sidelink communication (e.g., HARQ retransmission scheme configuration information) can be sent to the sending terminal and / or receiving terminal via system information and / or higher-layer signaling (e.g., RRC messages and / or MAC CE). The sending terminal can send a first-stage SCI to the receiving terminal via PSCCH (S701). The receiving terminal can receive the first-stage SCI from the sending terminal and can identify the information elements included in the first-stage SCI. The sending terminal can send a second-stage SCI (e.g., a second-stage SCI related to the first-stage SCI sent in step S701) and data to the receiving terminal via PSSCH (S702). The receiving terminal can receive the second-stage SCI from the sending terminal and can identify the information elements included in the second-stage SCI. The receiving terminal can perform a data reception operation based on the first-stage SCI and / or the second-stage SCI.

[0109] When data reception fails (e.g., data decoding fails), the receiving terminal can send a NACK to the sending terminal via PSFCH (S703). Upon receiving a NACK from the receiving terminal, the sending terminal can determine that data reception failed at the receiving terminal. In this case, the sending terminal can retransmit the data to the receiving terminal (S704). In step S704, the second-stage SCI and data (e.g., retransmitted data) can be sent to the receiving terminal via PSSCH. Alternatively, in step S704, the data can be retransmitted without a second-stage SCI. In step S704, the receiving terminal can perform a reception operation for the retransmitted data.

[0110] In an exemplary embodiment, the second-stage SCI and data can be sent via the same PSSCH. Alternatively, the second-stage SCI and data can be sent via different PSSCHs. Alternatively, the second-stage SCI can be sent via PSCCH, while the data can be sent via PSSCH. When using a single SCI scheme, the retransmission procedure according to the HARQ retransmission scheme can be performed based on the first-stage SCI without the second-stage SCI. In this case, the retransmitted data can be sent along with the first-stage SCI instead of the second-stage SCI. Alternatively, the data can be retransmitted without the first-stage SCI.

[0111] Figure 8This is a sequence diagram illustrating a first exemplary embodiment of a retransmission method based on a blind retransmission scheme in sidelink communication.

[0112] like Figure 8 As shown, a communication system may include a transmitting terminal and a receiving terminal. A transmitting terminal may refer to a terminal that transmits SL data, while a receiving terminal may refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5 235 shown is shown, and the receiving terminal can be... Figure 2 The UE#6 236 shown. Each of the transmitting and receiving terminals can be configured to work with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0113] Prior to step S801, configuration information for sidelink communication (e.g., configuration information for a blind retransmission scheme) can be sent to the sending terminal and / or receiving terminal via system information and / or higher-layer signaling (e.g., RRC messages and / or MAC CE). The sending terminal can send a first-stage SCI to the receiving terminal via PSCCH (S801). The receiving terminal can receive the first-stage SCI from the sending terminal and can identify the information elements included in the first-stage SCI. The sending terminal can send a second-stage SCI (e.g., a second-stage SCI related to the first-stage SCI sent in step S801) and data to the receiving terminal via PSSCH (S802). The receiving terminal can receive the second-stage SCI from the sending terminal and can identify the information elements included in the second-stage SCI. The receiving terminal can perform a data reception operation based on the first-stage SCI and / or the second-stage SCI.

[0114] After sending the first-stage SCI and the second-stage SCI, the sending terminal can retransmit the data (S803). The sending terminal can perform duplicate data transmission based on blind retransmission information configured by system information, higher-layer signaling, the first-stage SCI, and / or the second-stage SCI. Additionally, the receiving terminal can perform retransmission data reception based on blind retransmission information configured by system information, higher-layer signaling, the first-stage SCI, and / or the second-stage SCI.

[0115] In step S803, the second-stage SCI and data (e.g., retransmitted data) can be sent to the receiving terminal via PSSCH. Alternatively, in step S803, the data can be retransmitted without the second-stage SCI.

[0116] In an exemplary embodiment, the second-stage SCI and data can be sent via the same PSSCH. Alternatively, the second-stage SCI and data can be sent via different PSSCHs. Alternatively, the second-stage SCI can be sent via PSCCH, while the data can be sent via PSSCH. When using a single SCI scheme, the retransmission procedure according to the blind retransmission scheme can be performed based on the first-stage SCI without the second-stage SCI. In this case, the retransmitted data can be sent along with the first-stage SCI instead of the second-stage SCI. Alternatively, the data can be retransmitted without the first-stage SCI.

[0117] Figure 9 This is a sequence diagram illustrating a first exemplary embodiment of a switching method for a retransmission scheme in sidelink communication.

[0118] like Figure 9 As shown, a communication system may include a transmitting terminal and a receiving terminal. A transmitting terminal may refer to a terminal that transmits SL data, while a receiving terminal may refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5 235 shown is shown, and the receiving terminal can be... Figure 2 The UE#6 236 shown. Each of the transmitting and receiving terminals can be configured to work with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0119] In sidelink communication, the retransmission scheme can be switched from HARQ retransmission to blind retransmission. In step S901, a retransmission procedure based on the HARQ retransmission scheme can be executed between the sending terminal and the receiving terminal. Step S901 may include... Figure 7 Steps S701 to S704 are shown. When n NACKs occur for the same data (e.g., TB or CBG) in step S901, or when the number of NACKs for the same data (e.g., TB or CBG) in step S901 is greater than or equal to a threshold, the transmitting terminal may send a retransmission switching indicator (S902) indicating a switching retransmission scheme to the receiving terminal. Alternatively, the retransmission switching indicator may be transmitted regardless of the above conditions. n can be a natural number. The threshold may be signaled to the transmitting terminal and / or receiving terminal via at least one of system information, RRC messages, MAC CE, or control information (e.g., DCI, SCI).

[0120] A retransmission handover indicator can indicate a switch from a HARQ retransmission scheme to a blind retransmission scheme. The retransmission handover indicator can be more than one bit in size. The retransmission handover indicator can be included in the second-stage SCI. When resources are available for the blind retransmission scheme, the retransmission handover indicator can be included in the second-stage SCI instead of the first-stage SCI. In this case, retransmitted data and the second-stage SCI including the retransmission handover indicator can be sent in step S902. When using a single SCI scheme, the retransmission handover indicator can be included in the first-stage SCI instead of the second-stage SCI.

[0121] In step S902, the receiving terminal can receive a retransmission switching indicator from the sending terminal. When the receiving terminal receives the retransmission switching indicator, it can determine that the retransmission scheme for sidelink communication has switched from HARQ retransmission to blind retransmission. The sending terminal can retransmit data based on blind retransmission related information configured by system information, RRC messages, MAC CE, first-stage SCI, and / or second-stage SCI (S903). The receiving terminal can perform a receiving operation for retransmitted data based on blind retransmission related information configured by system information, RRC messages, MAC CE, first-stage SCI, and / or second-stage SCI. The resources used for the first blind retransmission can be resources reserved by a previous SCI (e.g., the first-stage SCI in step S901). For example, the resources used for the first blind retransmission can be resources reserved for HARQ retransmission.

[0122] Figure 10 This is a sequence diagram illustrating a second exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0123] like Figure 10 As shown, a communication system may include a transmitting terminal and a receiving terminal. A transmitting terminal may refer to a terminal that transmits SL data, while a receiving terminal may refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5235 shown is shown, and the receiving terminal can be... Figure 2 The UE#6 236 shown. Each of the transmitting and receiving terminals can be configured to work with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0124] In sidelink communication, the retransmission scheme can be switched from HARQ retransmission to blind retransmission. In step S1001, a retransmission procedure based on the HARQ retransmission scheme can be executed between the sending terminal and the receiving terminal. Step S1001 may include... Figure 7 The steps S701 to S704 are shown. That is, step S1001 can be combined with... Figure 9 The same applies to step S901. When n NACKs occur for the same data (e.g., TB or CBG) in step S1001, or when the number of NACKs for the same data (e.g., TB or CBG) in step S1001 is greater than or equal to a threshold, the transmitting terminal may send a retransmission switching indicator (S1002) indicating a retransmission scheme to the receiving terminal. Alternatively, the retransmission switching indicator may be sent regardless of the above conditions. n can be a natural number. The threshold may be signaled to the transmitting terminal and / or receiving terminal via at least one of system information, RRC messages, MAC CE, or control information (e.g., DCI, SCI).

[0125] A retransmission switching indicator can indicate a switch from a HARQ retransmission scheme to a blind retransmission scheme. The retransmission switching indicator can be more than one bit in size. The retransmission switching indicator can be included in the first-stage SCI. When no resources are available for the blind retransmission scheme, the retransmission switching indicator can be included in the first-stage SCI instead of the second-stage SCI. Thereafter, the retransmission procedure according to the blind retransmission scheme can be performed using the resources allocated by the first-stage SCI sent in step S1002 (e.g., reserved resources). Alternatively, even when resources are available for the blind retransmission scheme, the retransmission switching indicator can be included in the first-stage SCI instead of the second-stage SCI. In this case, the first-stage SCI sent in step S1002 can indicate the release of resources configured for the HARQ retransmission scheme in step S1001. That is, the first-stage SCI sent in step S1002 can override the resources configured for the HARQ retransmission scheme in step S1001 using resources for the blind retransmission scheme. Alternatively, the first-stage SCI sent in step S1002 can be used to configure new blind retransmission resources.

[0126] In step S1002, the receiving terminal can receive a retransmission switching indicator from the sending terminal. When the receiving terminal receives the retransmission switching indicator, it can determine that the retransmission scheme for sidelink communication has switched from the HARQ retransmission scheme to the blind retransmission scheme. The sending terminal can retransmit data based on the blind retransmission related information configured by system information, RRC messages, MAC CE, first-stage SCI, and / or second-stage SCI (S1003 and S1004). The receiving terminal can perform the receiving operation for the retransmitted data based on the blind retransmission related information configured by system information, RRC messages, MAC CE, first-stage SCI, and / or second-stage SCI. Here, the retransmission switching indicator can be sent through the second-stage SCI.

[0127] Figure 11This is a sequence diagram illustrating a third exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0128] like Figure 11 As shown, a communication system may include a transmitting terminal and a receiving terminal. A transmitting terminal may refer to a terminal that transmits SL data, while a receiving terminal may refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5235 shown is shown, and the receiving terminal can be... Figure 2 The UE#6 236 shown. Each of the transmitting and receiving terminals can be configured to work with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0129] In sidelink communication, the retransmission scheme can be switched from a blind retransmission scheme to a HARQ retransmission scheme. In step S1101, a retransmission procedure based on the blind retransmission scheme can be executed between the sending terminal and the receiving terminal. Step S1101 may include... Figure 8 The steps S801 to S803 are shown below. The transmitting terminal may send a retransmission switching indicator (S1102) to the receiving terminal, indicating a retransmission scheme. The retransmission switching indicator may be sent when data has been retransmitted more than n times in step S1101. n can be a natural number. n may be signaled to the transmitting terminal and / or the receiving terminal via at least one of system information, RRC messages, MAC CE, or control information (e.g., DCI, SCI).

[0130] A retransmission handover indicator can indicate a switch from a blind retransmission scheme to a HARQ retransmission scheme. The retransmission handover indicator can be more than one bit in size. The retransmission handover indicator can be included in the second-stage SCI. When resources are available for the HARQ retransmission scheme, the retransmission handover indicator can be included in the second-stage SCI instead of the first-stage SCI. In this case, retransmitted data and the second-stage SCI including the retransmission handover indicator can be sent in step S1102. When using a single SCI scheme, the retransmission handover indicator can be included in the first-stage SCI instead of the second-stage SCI.

[0131] In step S1102, the receiving terminal can receive a retransmission switching indicator from the sending terminal. When the receiving terminal receives the retransmission switching indicator, it can determine that the retransmission scheme for sidelink communication is switching from a blind retransmission scheme to a HARQ retransmission scheme. Communication between the sending and receiving terminals can be performed based on HARQ retransmission related information configured by system information, RRC messages, MAC CE, first-stage SCI, and / or second-stage SCI. For example, if data reception fails in step S1102, the receiving terminal can send a NACK to the sending terminal (S1103). When the receiving terminal receives the NACK, the sending terminal can retransmit the data (S1104). In step S1104, the retransmitted data can be sent together with the second-stage SCI. The resources used for the first HARQ retransmission can be resources reserved by a previous SCI (e.g., the first-stage SCI in step S1101). For example, the resources used for the first HARQ retransmission can be resources reserved for blind retransmission.

[0132] Figure 12 This is a sequence diagram illustrating a fourth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0133] like Figure 12 As shown, a communication system may include a transmitting terminal and a receiving terminal. A transmitting terminal may refer to a terminal that transmits SL data, while a receiving terminal may refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5235 shown is shown, and the receiving terminal can be... Figure 2 The UE#6 236 shown. Each of the transmitting and receiving terminals can be configured to work with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0134] In sidelink communication, the retransmission scheme can be switched from a blind retransmission scheme to a HARQ retransmission scheme. In step S1201, a retransmission procedure based on the blind retransmission scheme can be executed between the sending terminal and the receiving terminal. Step S1201 may include... Figure 8 The steps S801 to S803 are shown. That is, step S1201 can be combined with... Figure 11 The steps shown in S1101 are the same. The transmitting terminal can transmit a retransmission switching indicator (S1202) to the receiving terminal, indicating a retransmission scheme. A retransmission switching indicator can be sent when data has been retransmitted more than n times in step S1201. n can be a natural number. n can be signaled to the transmitting terminal and / or the receiving terminal via at least one of system information, RRC messages, MAC CE, or control information (e.g., DCI, SCI).

[0135] A retransmission switching indicator can indicate a switch from a blind retransmission scheme to a HARQ retransmission scheme. The retransmission switching indicator can be more than one bit in size. The retransmission switching indicator can be included in the first-stage SCI. When no resources are available for the HARQ retransmission scheme, the retransmission switching indicator can be included in the first-stage SCI instead of the second-stage SCI. Thereafter, the retransmission procedure according to the HARQ retransmission scheme can be performed using the resources allocated by the first-stage SCI sent in step S1202 (e.g., reserved resources). Alternatively, even when resources are available for the HARQ retransmission scheme, the retransmission switching indicator can be included in the first-stage SCI instead of the second-stage SCI. In this case, the first-stage SCI sent in step S1202 can indicate the release of resources configured for the blind retransmission scheme in step S1201. That is, the first-stage SCI sent in step S1202 can overwrite the resources configured for the blind retransmission scheme in step S1201 with resources configured for the HARQ retransmission scheme. Alternatively, the first-stage SCI sent in step S1202 can be used to configure new HARQ retransmission resources. Here, the retransmission switching indicator can be sent via the second-stage SCI.

[0136] In step S1202, the receiving terminal can receive a retransmission switching indicator from the sending terminal. When the receiving terminal receives the retransmission switching indicator, it can determine that the retransmission scheme for sidelink communication has switched from a blind retransmission scheme to a HARQ retransmission scheme. Communication between the sending and receiving terminals can be performed based on HARQ retransmission-related information configured by system information, RRC messages, MAC CE, first-stage SCI, and / or second-stage SCI. For example, the sending terminal can send the second-stage SCI and retransmission data to the receiving terminal (S1203). When data reception fails in step S1203, the receiving terminal can send a NACK for the data to the sending terminal (S1204). When the sending terminal receives the NACK for the data, it can determine that data reception has failed in the receiving terminal. Therefore, the sending terminal can send the second-stage SCI and retransmission data (S1205). In step S1205, the receiving terminal can perform a monitoring operation to receive the retransmission data.

[0137] exist Figure 9 and Figure 11 In the exemplary embodiment shown, the amount of resources reserved for the previous retransmission scheme and / or the corresponding resources can be used as the initial configuration value of the retransmission scheme after the retransmission scheme is switched. For example, the resources used for the retransmission scheme to be switched can be configured as resources reserved for the previous retransmission scheme, and the initial value of the number of retransmissions in the retransmission scheme to be switched can be set to the number of retransmissions remaining in the previous retransmission scheme.

[0138] exist Figure 11 and Figure 12 In the exemplary embodiment shown, when the blind retransmission scheme is switched to the HARQ retransmission scheme and not all blind retransmissions have been completed in the previous retransmission procedure according to the blind retransmission scheme, the first data when performing a retransmission according to the HARQ retransmission scheme may be the last data sent in the blind retransmission scheme (e.g., retransmitted data). Alternatively, when switching from the blind retransmission scheme to the HARQ retransmission scheme is performed, the first data when performing a retransmission according to the HARQ retransmission scheme may always be the last data sent in the blind retransmission scheme (e.g., retransmitted data).

[0139] When the blind retransmission scheme is switched to the HARQ retransmission scheme and all blind retransmissions are completed in the previous retransmission procedure according to the blind retransmission scheme, the first data in the retransmission procedure according to the HARQ retransmission scheme may be new data following the last data sent in the blind retransmission scheme. Alternatively, regardless of whether blind retransmissions have been completed in the previous retransmission procedure according to the blind retransmission scheme, the first data to be sent after switching to the retransmission procedure according to the HARQ retransmission scheme may be new data following the last data sent in the blind retransmission scheme.

[0140] In a retransmission procedure according to a HARQ retransmission scheme, when the transmission of the first data begins with the transmission of the last data according to a blind retransmission scheme, the receiving terminal can combine the data received according to the previous blind retransmission scheme with the data received according to the HARQ retransmission scheme, and based on the result of the combination, the receiving terminal can determine the HARQ response (e.g., ACK or NACK). Alternatively, the receiving terminal can determine the HARQ response for the data received according to the HARQ retransmission scheme without combining it with the data received according to the previous blind retransmission scheme.

[0141] The retransmission switching indicator can be configured as a 1-bit switching bit. For example, a retransmission switching indicator set to a first value (e.g., 0) can indicate a switch to a different retransmission scheme, while a retransmission switching indicator set to a second value (e.g., 1) can indicate maintaining the current retransmission scheme. Alternatively, a retransmission switching indicator set to a first value (e.g., 0) can indicate that a retransmission procedure should be executed according to a blind retransmission scheme, while a retransmission switching indicator set to a second value (e.g., 1) can indicate that a retransmission procedure should be executed according to a HARQ retransmission scheme. The retransmission scheme switching procedure can be based on... Figures 9 to 12 The above-described exemplary embodiments are performed.

[0142] Fields included in the SCI (e.g., the first-stage SCI and / or the second-stage SCI) can be used to indicate retransmission switching indicators. For example, a HARQ feedback enable / disable field (e.g., a HARQ feedback enable / disable indicator) included in the second-stage SCI can be used. When the HARQ feedback enable / disable field indicates that HARQ feedback is enabled, this can indicate the use of a HARQ retransmission scheme. When the HARQ feedback enable / disable field indicates that HARQ feedback is disabled, this can indicate the use of a blind retransmission scheme.

[0143] As another example, the switching of retransmission schemes can be implicitly or explicitly indicated by fields related to the HARQ retransmission scheme included in the SCI (e.g., fields related to PSFCH resource allocation, fields indicating the maximum number of retransmissions, and / or New Data Indicator (NDI) fields). Alternatively, the switching of retransmission schemes can be implicitly or explicitly indicated by fields related to the blind retransmission scheme included in the SCI (e.g., fields indicating the number of blind retransmissions (e.g., the maximum number of retransmissions) and / or resource configuration fields).

[0144] The HARQ feedback enable / disable field can be used to indicate whether a switch from a HARQ retransmission scheme to a blind retransmission scheme is possible. When the HARQ feedback enable / disable field indicates that HARQ feedback is enabled, this indicates that only the HARQ retransmission scheme is used. When the HARQ feedback enable / disable field indicates that HARQ feedback is disabled, this indicates that a switch from a HARQ retransmission scheme to a blind retransmission scheme is possible. In this case, the retransmission scheme in sidelink communication can be switched from a HARQ retransmission scheme to a blind retransmission scheme as needed. When the HARQ feedback enable / disable field indicates that HARQ feedback is disabled, other fields included in the SCI can implicitly or explicitly indicate the switch of the retransmission scheme.

[0145] Alternatively, the HARQ feedback enable / disable field can be used to indicate whether a switch from a blind retransmission scheme to a HARQ retransmission scheme is possible. When the HARQ feedback enable / disable field indicates that HARQ feedback is enabled, this indicates that a switch from a blind retransmission scheme to a HARQ retransmission scheme is possible. In this case, the retransmission scheme in sidelink communication can be switched from a blind retransmission scheme to a HARQ retransmission scheme as needed. When the HARQ feedback enable / disable field indicates that HARQ feedback is enabled, other fields included in the SCI can implicitly or explicitly indicate a switch to a different retransmission scheme. When the HARQ feedback enable / disable field indicates that HARQ feedback is disabled, this indicates that only a blind retransmission scheme is used. That is, when HARQ feedback is disabled, this indicates that a switch from a blind retransmission scheme to a HARQ retransmission scheme is not possible.

[0146] After a retransmission scheme is switched, the transmitting terminal can report the switch to the base station. The transmitting terminal can send information indicating that the retransmission scheme has been switched (hereinafter referred to as a "switching report indicator") to the base station using uplink resources allocated for reporting the retransmission scheme switch (e.g., Physical Uplink Control Channel (PUCCH) or Physical Uplink Shared Channel (PUSCH)) or uplink resources allocated for sending sidelink communication-related information to the base station (e.g., PUCCH or PUSCH). The switching report indicator can be sent from the transmitting terminal to the base station via RRC messages, MAC CE, and / or control information (e.g., UCI). When the switching report indicator is included in control information (e.g., UCI), the switching report indicator can be configured as a 1-bit switching bit. For example, a switching report indicator set to a first value (e.g., 0) can indicate a switch of the retransmission scheme. A switching report indicator set to a second value (e.g., 1) can indicate that the current retransmission scheme is maintained. Alternatively, a handover report indicator set to a first value (e.g., 0) can indicate that the HARQ retransmission scheme is switched to a blind retransmission scheme. A handover report indicator set to a second value (e.g., 1) can indicate that the blind retransmission scheme is switched to the HARQ retransmission scheme.

[0147] When switching from a HARQ retransmission scheme to a blind retransmission scheme, a handover report indicator can be transmitted on the uplink channel allocated for reporting HARQ responses (e.g., ACK or NACK) according to the HARQ retransmission scheme. The HARQ response bits in the uplink channel (e.g., UCI) can be configured as the handover report indicator. Alternatively, a separate bit in the uplink channel (e.g., UCI) can be configured as the handover report indicator.

[0148] Figure 13 This is a sequence diagram illustrating a fifth exemplary embodiment of a switching method for a retransmission scheme in sidelink communication.

[0149] like Figure 13 As shown, a communication system may include a base station, a transmitting terminal, and a receiving terminal. A transmitting terminal can refer to a terminal that transmits SL data, while a receiving terminal can refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5 235 shown can be received by the receiving terminal. Figure 2 The UE#6 236 shown is shown, and the base station can be... Figure 2 The base station 210 is shown. Each of the base station, transmitting terminal, and receiving terminal can be configured to interact with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0150] A retransmission scheme switching procedure (S1301) can be executed between the sending terminal and the receiving terminal. The retransmission scheme switching procedure can be based on... Figures 9 to 12 This can be performed using one or more exemplary embodiments shown. In the retransmission scheme switching procedure, the HARQ retransmission scheme can be switched to a blind retransmission scheme. Alternatively, in the retransmission scheme switching procedure, the blind retransmission scheme can be switched to a HARQ retransmission scheme.

[0151] When the retransmission scheme handover is complete, the transmitting terminal can use uplink resources (e.g., PUCCH and / or PUSCH) to send a handover report indicator (S1302) to the base station indicating that the handover of the retransmission scheme handover is complete. The base station can receive the handover report indicator from the transmitting terminal, and based on the handover report indicator, the base station can determine that the retransmission scheme between the transmitting terminal and the receiving terminal has been switched. In addition, the base station can confirm the handover retransmission scheme (e.g., HARQ retransmission scheme or blind retransmission scheme) based on the handover report indicator.

[0152] Figure 14 This is a sequence diagram illustrating a sixth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0153] like Figure 14 As shown, a communication system may include a base station, a transmitting terminal, and a receiving terminal. A transmitting terminal can refer to a terminal that transmits SL data, while a receiving terminal can refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5 235 shown can be received by the receiving terminal. Figure 2 The UE#6 236 shown is shown, and the base station can be... Figure 2 The base station 210 is shown. Each of the base station, transmitting terminal, and receiving terminal can communicate with... Figure 3 The communication node 300 shown is configured identically or similarly. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0154] The transmitting terminal can confirm the necessity of switching the retransmission scheme. When it is determined that a switch of the retransmission scheme is necessary, the transmitting terminal can use uplink resources (e.g., PUCCH and / or PUSCH) to send a handover request indicator (S1401) to the base station requesting a switch of the retransmission scheme. The handover request indicator may include "request to switch from HARQ retransmission scheme to blind retransmission scheme" or "request to switch from blind retransmission scheme to HARQ retransmission scheme" and "retransmission scheme switching request".

[0155] The base station can receive a handover request indicator from the transmitting terminal and confirm the requested handover retransmission scheme based on the handover request indicator. Additionally, the base station can confirm the type of retransmission scheme to be switched (e.g., HARQ retransmission scheme or blind retransmission scheme). The base station can confirm whether to approve the handover retransmission scheme. When the handover of the retransmission scheme is approved, the base station can use downlink resources (e.g., PDCCH and / or PDSCH) to send a handover approval indicator (S1402) to the transmitting terminal indicating that the handover of the retransmission scheme has been approved. The handover approval indicator can indicate the approval of the handover retransmission scheme and the type of retransmission scheme to be switched.

[0156] The transmitting terminal can receive a handover approval indicator from the base station and determine, based on the handover approval indicator, that the retransmission scheme handover has been approved. In this case, a retransmission scheme handover procedure (S1403) can be executed between the transmitting terminal and the receiving terminal. The retransmission scheme handover procedure can be based on... Figures 9 to 12 The above-described exemplary embodiments are performed.

[0157] The transmitting terminal may send a handover request indicator to the base station using uplink resources (e.g., PUCCH or PUSCH) allocated for handover requests for retransmission schemes or for sending information related to sidelink communication to the base station. The handover request indicator may be sent from the transmitting terminal to the base station via RRC messages, MAC CE, and / or control information (e.g., UCI).

[0158] Upon receiving a handover request indicator, the base station can explicitly or implicitly notify the transmitting terminal of whether to approve or disapprove the handover retransmission scheme. The handover approval indicator (or handover disapproval indicator) can be transmitted using downlink resources (e.g., PDCCH or PDSCH). These indicators (e.g., handover request indicator, handover approval indicator, or handover disapproval indicator) can be configured as independent fields (e.g., independent fields within the DCI). Alternatively, the indicators can be explicitly or implicitly indicated in the transmission procedure of the configuration information for the HARQ retransmission scheme or blind retransmission scheme.

[0159] exist Figure 13 and 14In the exemplary embodiment shown, trigger conditions for switching retransmission schemes can be configured for the transmitting terminal to determine the necessity of switching retransmission schemes, and the retransmission scheme can be switched according to the trigger conditions. The base station can send the trigger conditions to the transmitting terminal and / or the receiving terminal using one or more combinations of system information, RRC messages, MAC CE, and control information (e.g., DCI). For example, multiple trigger conditions can be configured by higher-layer signaling (e.g., system information, RRC messages, and / or MAC CE), and the base station can select a specific trigger condition from among the multiple trigger conditions and notify the transmitting terminal and / or the receiving terminal of the selected specific trigger condition. The base station can notify the transmitting terminal and / or the receiving terminal of the selected specific trigger condition using higher-layer signaling, control information (e.g., DCI), or a data channel. Alternatively, a specific trigger condition among multiple trigger conditions can be selected by the transmitting terminal. In this case, the transmitting terminal can send the selected specific trigger condition to the receiving terminal using higher-layer signaling or a sidelink channel (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)).

[0160] Triggering conditions can be categorized into Type 1 triggering conditions for switching from a HARQ retransmission scheme to a blind retransmission scheme and Type 2 triggering conditions for switching from a blind retransmission scheme to a HARQ retransmission scheme. Type 1 triggering conditions may include one or more triggering conditions, and Type 2 triggering conditions may also include one or more triggering conditions. The base station can select Type 1 and / or Type 2 triggering conditions and notify the transmitting terminal and / or receiving terminal of the selected triggering conditions. In this case, the base station can use higher-layer signaling, control information, or data channels to send the selected triggering conditions to the transmitting terminal and / or receiving terminal. Alternatively, the transmitting terminal can select Type 1 and / or Type 2 triggering conditions and notify the receiving terminal of the selected triggering conditions. In this case, the transmitting terminal can use higher-layer signaling or sidelink channels (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)) to send the specific selected triggering conditions to the receiving terminal.

[0161] Type 1 triggering conditions may include the occurrence of consecutive NACKs or consecutive DTXs. A Type 1 triggering condition is satisfied when the number of consecutive NACKs or consecutive DTXs is greater than or equal to a threshold. When a Type 1 triggering condition is satisfied, the retransmission scheme can be switched from a HARQ retransmission scheme to a blind retransmission scheme. The aforementioned threshold can be set by the base station. In this case, the base station can notify the transmitting terminal and / or receiving terminal of the Type 1 triggering condition threshold using higher-layer signaling, control information, or data channels. Alternatively, the aforementioned threshold can be set by the transmitting terminal. In this case, the transmitting terminal can notify the receiving terminal of the Type 1 triggering condition threshold using higher-layer signaling or sidelink channels (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)).

[0162] For another example, the triggering condition may include a condition that the channel state (e.g., channel quality state) meets a specific benchmark. Channel state information can be reported to the base station from the transmitting terminal and / or the receiving terminal. Furthermore, channel state information can be reported from the receiving terminal to the transmitting terminal. Here, channel state may refer to the channel state in the side link between the transmitting and receiving terminals. The specific benchmark may be a benchmark value for the Channel Quality Indicator (CQI) or a benchmark value for the Reference Signal Received Power (RSRP). When the channel state is less than or equal to the benchmark value of the CQI or the benchmark value of the RSRP, a retransmission scheme may be switched. Alternatively, when the channel state exceeds the benchmark value of the CQI or RSRP, a retransmission scheme may be switched. The triggering condition may be configured based on benchmark indicators (e.g., channel state information (e.g., CQI, RSRP, Grade Indicator (RI), Precoding Matrix Indicator (PMI)) and a benchmark value for each channel state (e.g., a threshold)).

[0163] For another example, the triggering condition may include a channel occupancy state meeting a specific benchmark. Channel occupancy state information can be reported to the base station from the transmitting terminal and / or the receiving terminal. Additionally, channel occupancy state information can be reported from the receiving terminal to the transmitting terminal. Here, channel occupancy state may refer to the channel occupancy state in the sidelink between the transmitting and receiving terminals. When the channel occupancy state is less than or equal to the benchmark value, a retransmission scheme can be switched. Alternatively, when the channel occupancy state exceeds the benchmark value, a retransmission scheme can be switched. The benchmark value for the channel occupancy state can be configured to the terminal (e.g., the transmitting and / or receiving terminal) through one or more combinations of system information, RRC messages, MAC CE, and control information.

[0164] Multiple triggering conditions can be configured by higher-layer signaling. A base station or transmitting terminal can select a specific triggering condition from these conditions and transmit it to other communication nodes (e.g., transmitting terminal and / or receiving terminal). The base station can transmit the selected specific triggering condition to the transmitting terminal and / or receiving terminal using higher-layer signaling, control information, or data channels. The transmitting terminal can transmit the specific triggering condition to the receiving terminal using higher-layer signaling or sidelink channels (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)). Multiple triggering conditions can be configured by higher-layer signaling according to combinations and / or extensions of the exemplary embodiments described above.

[0165] The base station or transmitting terminal can select multiple trigger conditions from the trigger conditions configured via higher-layer signaling and notify other communication nodes of the selected trigger conditions. In this case, the retransmission scheme can be switched even if only one of the selected trigger conditions is met. Alternatively, the retransmission scheme can be switched if all of the selected trigger conditions are met.

[0166] A single trigger condition can be configured by higher-layer signaling. For example, each of Type 1 and Type 2 trigger conditions can include one trigger condition. In this case, the base station or transmitting terminal may not need to perform the operation of selecting the trigger condition or transmitting the selected trigger condition.

[0167] After a preset time period has elapsed since the retransmission scheme was switched, the retransmission scheme can switch back to the previous retransmission scheme.

[0168] Figure 15 This is a sequence diagram illustrating a seventh exemplary embodiment of a method for switching retransmission schemes in sidelink communication. Figure 16 This is a sequence diagram illustrating an eighth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0169] like Figure 15 and Figure 16 As shown, a communication system may include a transmitting terminal and a receiving terminal. A transmitting terminal may refer to a terminal that transmits SL data, while a receiving terminal may refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5 235 shown is shown, and the receiving terminal can be... Figure 2 The UE#6 236 shown. Each of the transmitting and receiving terminals can be configured to work with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0170] Figure 15Steps S1501 to S1503 in the exemplary embodiment shown can be combined with Figure 9 Steps S901 to S903 in the exemplary embodiment shown are performed in the same or similar manner. Figure 16 Steps S1601 to S1604 in the exemplary embodiment shown can be combined with Figure 10 Steps S1001 to S1004 in the exemplary embodiment shown are performed in the same or similar manner. Figure 15 and 16 In the exemplary embodiment shown, the HARQ retransmission scheme can be switched to a blind retransmission scheme, and the blind retransmission scheme can be switched back to the HARQ retransmission scheme. When a trigger condition is met, the transmitting terminal can switch the blind retransmission scheme to the HARQ transmission scheme. The receiving terminal can determine that the blind retransmission scheme has switched to the HARQ transmission scheme when the trigger condition is met. The retransmission procedure according to the HARQ retransmission scheme can be executed again after the retransmission procedure according to the blind retransmission scheme (S1504 and S1605).

[0171] When data is transmitted n times in the retransmission procedure according to the blind retransmission scheme, the retransmission scheme can be switched from the blind retransmission scheme to the HARQ retransmission scheme. n can be a threshold for the number of data retransmissions and can be a natural number. n can be set by higher-layer signaling. For example, the base station can determine n and notify the sending terminal and / or receiving terminal of n using higher-layer signaling, control information, or data channels. The sending terminal can receive n from the base station and notify the receiving terminal of n using higher-layer signaling or sidelink channels (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)). Alternatively, n can be determined by the sending terminal. In this case, the sending terminal can notify the receiving terminal of n using higher-layer signaling or sidelink channels (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)). Additionally, the sending terminal can... Figure 13 In step S1302 shown, the n determined by the transmitting terminal and the handover report indicator are sent together to the base station. Alternatively, the transmitting terminal can... Figure 14 In step S1401 shown, n, determined by the transmitting terminal, is sent to the base station along with a handover request indicator. In the exemplary embodiment described above, not only n, but also information required for the blind retransmission scheme can be sent together.

[0172] Figure 17 This is a sequence diagram illustrating a ninth exemplary embodiment of a switching method for retransmission schemes in sidelink communication. Figure 18 This is a sequence diagram illustrating a tenth exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0173] like Figure 17 and Figure 18As shown, a communication system may include a transmitting terminal and a receiving terminal. A transmitting terminal may refer to a terminal that transmits SL data, while a receiving terminal may refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5 235 shown is shown, and the receiving terminal can be... Figure 2 The UE#6 236 shown. Each of the transmitting and receiving terminals can be configured to work with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0174] Figure 17 Steps S1701 to S1704 in the exemplary embodiment shown can be combined with Figure 11 Steps S1101 to S1104 in the exemplary embodiment shown are performed in the same or similar manner. Figure 18 Steps S1801 to S1805 in the exemplary embodiment shown can be combined with Figure 12 Steps S1201 to S1205 in the exemplary embodiment shown are performed in the same or similar manner. Figure 17 and Figure 18 In the exemplary embodiment shown, the blind retransmission scheme can be switched to the HARQ retransmission scheme, and the HARQ retransmission scheme can be switched back to the blind retransmission scheme. When a trigger condition is met, the transmitting terminal can switch the HARQ retransmission scheme to the blind retransmission scheme. The receiving terminal can determine that the HARQ retransmission scheme has been switched to the blind retransmission scheme when the trigger condition is met. After the retransmission procedure according to the HARQ retransmission scheme, the retransmission procedure according to the blind retransmission scheme can be executed again (S1806).

[0175] In a retransmission procedure based on a HARQ retransmission scheme, when more than n NACKs or DTXs occur for a single data item, or when more than n NACKs or DTXs occur for multiple data items, the retransmission scheme can switch from a HARQ retransmission scheme to a blind retransmission scheme. n can be a natural number and can be a threshold for consecutive NACKs or consecutive DTXs. The criteria for n, the number of NACKs and / or DTXs, and information about n can operate in the same manner as in the exemplary embodiment based on the triggering conditions. The aforementioned conditions and values ​​(e.g., n) can be configured by higher-layer signaling.

[0176] The base station can determine a setting value (e.g., n). In this case, the base station can notify the transmitting terminal and / or receiving terminal of n using higher-layer signaling, control information, or data channels. The transmitting terminal can receive n from the base station and notify the receiving terminal of n using higher-layer signaling or sidelink channels (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)). Alternatively, n can be determined by the transmitting terminal. In this case, the transmitting terminal can notify the receiving terminal of n using signaling or sidelink channels (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)).

[0177] In addition, the sending terminal can Figure 13 In step S1302 shown, the n determined by the transmitting terminal and the handover report indicator are sent together to the base station. Alternatively, the transmitting terminal can... Figure 14 In step S1401, the n determined by the transmitting terminal and the handover request indicator are sent together to the base station. In the exemplary embodiment described above, not only n can be sent, but also the information required for the blind retransmission scheme can be sent together. When the triggering condition is not met (e.g., when more than n of NACK or DTX does not occur), the retransmission procedure according to the HARQ retransmission method can be executed without switching the retransmission scheme.

[0178] Figure 19 This is a sequence diagram illustrating an eleventh exemplary embodiment of a switching method for retransmission schemes in sidelink communication.

[0179] like Figure 19 As shown, a communication system may include a base station, a transmitting terminal, and a receiving terminal. A transmitting terminal can refer to a terminal that transmits SL data, while a receiving terminal can refer to a terminal that receives SL data. For example, the transmitting terminal could be... Figure 2 The UE#5 235 shown can be received by the receiving terminal. Figure 2 The UE#6 236 shown is shown, and the base station can be... Figure 2 The base station 210 is shown. Each of the base station, transmitting terminal, and receiving terminal can be configured to interact with... Figure 3 The communication node 300 shown is the same or similar. Each of the sending and receiving terminals can support... Figures 4 to 6 The protocol stack shown.

[0180] The base station can determine the retransmission scheme handover based on the aforementioned triggering conditions. When the retransmission scheme handover is determined, the base station can send a retransmission handover indicator indicating the handover scheme to the transmitting terminal (S1901). The retransmission handover indicator can be sent from the base station to the transmitting terminal using higher-layer signaling, control information, or data channels. The transmitting terminal can receive the retransmission handover indicator from the base station and can determine that a retransmission scheme handover is requested based on the retransmission handover indicator. The transmitting terminal sends the retransmission handover indicator to the receiving terminal using higher-layer signaling or sidelink channels (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)) (S1902). The receiving terminal can receive the retransmission handover indicator from the transmitting terminal and can determine that a retransmission scheme handover is requested based on the retransmission handover indicator. Thereafter, a retransmission scheme handover procedure can be performed between the transmitting terminal and the receiving terminal (S1903). The retransmission scheme handover procedure (e.g., step S1903) can be performed by... Figures 9 to 12 and Figures 15 to 18 It may be performed by one or more of the exemplary embodiments shown, a combination of the exemplary embodiments described above, or an extension of the exemplary embodiments described above.

[0181] The retransmission handover indicator can be indicated using the upper-layer message or sidelink channel (e.g., PSCCH (e.g., Phase 1 SCI), PSSCH (e.g., Phase 2 SCI)) first sent in the retransmission scheme handover procedure. Figure 19 In the exemplary embodiment shown, the retransmission switching indicator can be Figures 9 to 12 The retransmission switching indicator in the exemplary embodiments shown, a combination of the above retransmission switching indicators, or an extension of the above retransmission switching indicator.

[0182] Exemplary embodiments of this disclosure can be implemented as program instructions executable by various computers and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, or combinations thereof. The program instructions recorded on the computer-readable medium may be specifically designed and configured for this disclosure, or may be well-known and available to those skilled in the art of computer software.

[0183] Examples of computer-readable media may include hardware devices such as ROM, RAM, and flash memory, 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 that can be executed by a computer using an interpreter. The aforementioned exemplary hardware devices may be configured to operate as at least one software module to perform embodiments of this disclosure, and vice versa.

[0184] Although exemplary embodiments and advantages of this disclosure have been described in detail, it should be understood that those skilled in the art to which this invention pertains may make various changes, substitutions and alterations herein without departing from the spirit and scope of this disclosure as set forth in the claims.

Claims

1. An operation method for a transmitting terminal, which is an operation method for a transmitting terminal in a communication system, comprising: Based on the first retransmission scheme, the first data is sent to the receiving terminal; Based on the result of comparing the channel occupancy status between the transmitting terminal and the receiving terminal with the pre-configured reference value, the retransmission scheme is switched from the first retransmission scheme to the second retransmission scheme. Send first-level side link control information, i.e., first-level SCI, to the receiving terminal. The first-level SCI includes a first indicator, resource allocation information, and resource release information. The first indicator indicates switching the retransmission scheme. The resource allocation information indicates new resources allocated for the second retransmission scheme as the new retransmission scheme. The resource release information indicates the release of resources allocated for the first retransmission scheme as the previous retransmission scheme. as well as Based on the second retransmission scheme, second data is sent to the receiving terminal using the resources indicated by the resource allocation information. The first retransmission scheme and the second retransmission scheme are distinguished by whether or not a Hybrid Automatic Repeat Request (HARQ) feedback is sent.

2. The operating method according to claim 1, further comprising: When the retransmission scheme is switched, a second indicator indicating that the retransmission scheme has been switched is sent to the base station.

3. The operating method according to claim 1, further comprising: Send a third indicator to the base station requesting a switch to the retransmission scheme; as well as Receive a fourth indicator from the base station approving the handover of the retransmission scheme. The retransmission scheme is switched when the fourth indicator is received.

4. The operating method according to claim 1, further comprising: The fifth indicator received from the base station requests a switch to the retransmission scheme. The retransmission scheme is switched when the fifth indicator is received.

5. The operating method according to claim 1, wherein, The retransmission scheme is switched on a unit basis, namely, transport block (TB), code block group (CBG), or HARQ process.

6. The operating method according to claim 1, wherein, When the first retransmission scheme is a HARQ retransmission scheme, the second retransmission scheme is a blind retransmission scheme, and when the first retransmission scheme is a blind retransmission scheme, the second retransmission scheme is a HARQ retransmission scheme. When using the HARQ retransmission scheme, HARQ feedback is sent; when using the blind retransmission scheme, the HARQ feedback is not sent.

7. A method for operating a receiving terminal, which is a method for operating a receiving terminal in a communication system, comprising: Based on the first retransmission scheme, the first data is received from the sending terminal; The first-level side link control information, i.e., the first-level SCI, is received from the sending terminal. The first-level SCI includes a first indicator, resource allocation information, and resource release information. The first indicator indicates a switching retransmission scheme. The resource allocation information indicates new resources allocated for the second retransmission scheme as a new retransmission scheme. The resource release information indicates the release of resources allocated for the first retransmission scheme as a previous retransmission scheme. as well as Based on the second retransmission scheme, second data is received from the sending terminal using the resources indicated by the resource allocation information. Based on the comparison between the channel occupancy status between the receiving terminal and the transmitting terminal and a pre-configured reference value, it is determined to switch the second retransmission scheme to the first retransmission scheme. Based on the first retransmission scheme, third data is received from the sending terminal. The first retransmission scheme and the second retransmission scheme are distinguished by whether or not a Hybrid Automatic Repeat Request (HARQ) feedback is sent.

8. The operating method according to claim 7, wherein, When the first retransmission scheme is a HARQ retransmission scheme, the second retransmission scheme is a blind retransmission scheme, and when the first retransmission scheme is a blind retransmission scheme, the second retransmission scheme is a HARQ retransmission scheme. When using the HARQ retransmission scheme, HARQ feedback is sent; when using the blind retransmission scheme, HARQ feedback is not sent.

9. A transmitting terminal, which is a transmitting terminal in a communication system, comprising: processor; as well as The memory stores one or more instructions that can be executed by the processor. One or more instructions are executed to perform the following operations: Based on the first retransmission scheme, the first data is sent to the receiving terminal; Based on the result of comparing the channel occupancy status between the transmitting terminal and the receiving terminal with the pre-configured reference value, the retransmission scheme is switched from the first retransmission scheme to the second retransmission scheme. The receiving terminal is sent first-level sidelink control information, i.e., first-level SCI. The first-level SCI includes a first indicator, resource allocation information, and resource release information. The first indicator indicates a switch to the retransmission scheme. The resource allocation information indicates new resources allocated for the second retransmission scheme as the new retransmission scheme. The resource release information indicates the release of resources allocated for the first retransmission scheme as the previous retransmission scheme. Based on the second retransmission scheme, second data is sent to the receiving terminal using the resources indicated by the resource allocation information. The first retransmission scheme and the second retransmission scheme are distinguished by whether or not a Hybrid Automatic Repeat Request (HARQ) feedback is sent.

10. The transmitting terminal according to claim 9, wherein, The one or more instructions are further executed to perform the following operations: when the retransmission scheme is switched, a second indicator indicating that the retransmission scheme has been switched is sent to the base station.

11. The transmitting terminal according to claim 9, wherein, The one or more instructions are further executed to perform the following operations: Send a third indicator to the base station requesting a switch to the retransmission scheme; as well as Receive a fourth indicator from the base station approving the handover of the retransmission scheme. The retransmission scheme is switched when the fourth indicator is received.

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