Method and apparatus for relay communication in sidelink

Abstract

A method and apparatus for relay communication in sidelink are disclosed. A transmitting terminal operation method includes the steps of: performing a first relay communication with a receiving terminal through a first relay terminal; receiving a first message including a relay release indicator from the first relay terminal; setting a connection between the transmitting terminal and a second relay terminal when the first message is received; and transmitting a second message to the receiving terminal through the first relay terminal, the second message including a first relay setup completion indicator for indicating that the connection setup between the transmitting terminal and the second relay terminal is completed.

Description

Technical Field

[0001] This invention relates to a sidelink (SL) communication technology, and more specifically, to a technology for supporting SL relay communication through a new relay terminal. Background Technology

[0002] To handle the surge in wireless data following the commercialization of 4th Generation (4G) communication systems (e.g., Long Term Evolution (LTE) and Advanced LTE-A), it's necessary to consider not only the frequency bands of 4G systems (e.g., below 6 GHz) but also 5th Generation (5G) communication systems (e.g., New Radio (NR) systems) that utilize higher frequency bands (e.g., above 6 GHz). 5G communication 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. V2X communication supported in cellular communication systems (e.g., 4G, 5G, etc.) can be called "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, and vehicle-to-network (V2N) communication, etc.

[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 the sidelink channel can be used to perform communication between vehicles. Configured grant (CG) resources can be used to perform sidelink communication. CG resources can be configured periodically, and CG resources can be used to transmit periodic data (e.g., periodic sidelink data).

[0005] On the other hand, side-link (SL) communication between the sending terminal and the receiving terminal can be performed via relay. Relay communication performed via a side-link is called SL relay communication. For SL relay communication, the connection between the sending terminal and the relay terminal can be configured, and the connection between the relay terminal and the receiving terminal can also be configured. The relay terminal can relay SL communication between the sending terminal and the receiving terminal. During SL relay communication, there may be situations where the relay terminal cannot support SL relay communication. In this case, a new relay terminal is needed to perform the SL relay communication. Summary of the Invention

[0006] Technical issues

[0007] The present invention aims to provide a method and apparatus for performing SL relay communication through a new relay terminal.

[0008] Technical solution

[0009] An operation method of a transmitting terminal according to a first exemplary embodiment of the present invention for achieving the above objectives may include: performing a first side link (SL) relay communication with a receiving terminal via a first relay terminal; receiving a first message including a relay release indicator from the first relay terminal; configuring a connection between the transmitting terminal and a second relay terminal in response to receiving the first message; sending a second message to the receiving terminal via the first relay terminal, the second message including a first relay configuration completion indicator indicating that the connection configuration between the transmitting terminal and the second relay terminal has been completed; receiving a third message via the first relay terminal, the third message including a second relay configuration completion indicator indicating that the connection configuration between the receiving terminal and the second relay terminal has been completed; and performing a second SL relay communication with the receiving terminal via the second relay terminal in response to receiving the third message.

[0010] Upon receiving the first message, the data transmission operation of the sending terminal through the first relay terminal can be stopped.

[0011] Even when the first message is received, the data transmission operation of the sending terminal through the first relay terminal can be performed, and the transmission operation can be stopped after the third message is received.

[0012] The second message may further include at least one of the following: information about the second relay terminal or a number used to identify the data last sent from the sending terminal to the receiving terminal via the first relay terminal.

[0013] The third message may further include at least one of the following: information about the receiving terminal, information about the second relay terminal, or a number used to identify the last data received by the receiving terminal.

[0014] The configuration of the connection between the transmitting terminal and the second relay terminal may include: discovering one or more neighboring relay terminals; identifying one of the one or more discovered neighboring relay terminals as the second relay terminal; and configuring the connection with the second relay terminal.

[0015] Performing a second SL relay communication may include: sending data lost in the first SL relay communication to a receiving terminal via the second relay terminal; and sending new data to the receiving terminal via the second relay terminal.

[0016] When a third message is received, the connection configuration between the sending terminal and the first relay terminal can be terminated.

[0017] An operation method of a first relay terminal according to a second exemplary embodiment of the present invention for achieving the above objectives may include: performing side-link (SL) relay communication between a transmitting terminal and a receiving terminal; when SL relay communication is not supported, sending a first message including a relay release indicator to the transmitting terminal; receiving a second message from the transmitting terminal, the second message including a first relay configuration completion indicator indicating that the connection configuration between the transmitting terminal and the second relay terminal has been completed; sending the second message to the receiving terminal; receiving a third message from the receiving terminal, the third message including a second relay configuration completion indicator indicating that the connection configuration between the receiving terminal and the second relay terminal has been completed; sending the third message to the transmitting terminal; and after sending the third message, releasing the connection configuration between the transmitting terminal and the first relay terminal and the connection configuration between the receiving terminal and the first relay terminal.

[0018] After sending the first message, the relay operation of the sending terminal can be stopped.

[0019] Even after the first message is sent, data relay operations can be performed on the sending terminal, and relay operations can be stopped after the third message is sent.

[0020] The second message may further include at least one of the following: information about the sending terminal, information about the second relay terminal, or a number used to identify data that was last sent from the sending terminal to the receiving terminal via the first relay terminal.

[0021] The third message may further include at least one of the following: information about the receiving terminal, information about the second relay terminal, or a number used to identify the last data received by the receiving terminal.

[0022] An operation method of a receiving terminal according to a third exemplary embodiment of the present invention for achieving the above objectives may include: performing a first side link (SL) relay communication with a transmitting terminal via a first relay terminal; receiving a second message via the first relay terminal, the second message including a first relay configuration completion indicator indicating that the connection configuration between the transmitting terminal and the second relay terminal has been completed; configuring a connection with the second relay terminal indicated by the second message; sending a third message to the transmitting terminal via the first relay terminal, the third message including a second relay configuration completion indicator indicating that the connection configuration between the receiving terminal and the second relay terminal has been completed; and after sending the third message, performing a second SL relay communication with the transmitting terminal via the second relay terminal.

[0023] The operation method may further include receiving a first message including a relay release indicator from the first relay terminal before receiving the second message.

[0024] Upon receiving the first message, the receiving operation of the sending terminal relayed by the first relay terminal can be stopped.

[0025] Even when the first message is received, the receiving operation of the sending terminal relayed by the first relay terminal can be performed, and the receiving operation can be stopped after the third message is sent.

[0026] The second message may further include at least one of the following: information about the sending terminal, information about the second relay terminal, or a number used to identify data that was last sent from the sending terminal to the receiving terminal via the first relay terminal.

[0027] The third message may further include at least one of the information of the second relay terminal or a number used to identify the last data received by the receiving terminal.

[0028] Performing a second SL relay communication may include: receiving data lost in the first SL relay communication via a second relay terminal; and receiving new data from the sending terminal via a second relay terminal.

[0029] Beneficial effects

[0030] According to the present invention, SL relay communication between a transmitting terminal and a receiving terminal can be performed through a first relay terminal. When SL relay communication through the first relay terminal is not supported, a connection between the transmitting terminal and a second relay terminal (i.e., a new relay terminal) can be configured, and a connection between the receiving terminal and the second relay terminal can also be configured. In this case, SL relay communication between the transmitting terminal, the second relay terminal, and the receiving terminal can be performed. Therefore, SL relay communication can be performed efficiently. 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 an exemplary implementation of a cellular communication system.

[0033] Figure 3 This is a conceptual diagram illustrating an exemplary implementation of a communication node constituting a cellular communication system.

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

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

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

[0037] Figure 7a and Figure 7b A sequence diagram of a first exemplary embodiment of a method for SL relay communication via a new relay terminal is shown.

[0038] Figure 8a and Figure 8b A sequence diagram of a second exemplary embodiment of a method for SL relay communication via a new relay terminal is shown. Detailed Implementation

[0039] Since the present invention can be modified in various ways and has several forms, specific exemplary embodiments will be shown in the accompanying drawings and described in detail in the specific specification. However, it should be understood that this is not intended to limit the invention to the specific exemplary embodiments; on the contrary, the invention will cover all modifications and alternatives that fall within the spirit and scope of the invention.

[0040] Relational terms such as "first," "second," etc., can be used to describe various elements, but these elements should not be limited by the terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the invention, a first component may be named a second component, and a second component may similarly be named a first component. The term "and / or" refers to any one or a combination of a plurality of related and described items.

[0041] In an exemplary embodiment of the present invention, "at least one of A and B" may refer to "at least one of A or B" or "at least one combination of one or more of A and B". Furthermore, "one or more of A and B" may refer to "one or more of A or B" or "one or more combinations of one or more of A and B".

[0042] In an exemplary embodiment of the present invention, (re)transmission can mean “transmission”, “retransmission”, or “transmission and retransmission”; (re)configuration can mean “configuration”, “reconfiguration”, or “configuration and reconfiguration”; (re)connection can mean “connection”, “reconnection”, or “connection and reconnection”; and (re)access can mean “access”, “reaccess”, or “access and reaccess”.

[0043] When it is said that one component is "joined" or "connected" to another component, it should be understood that one component is directly "joined" or "connected" to another component, or that other components may be arranged between them. Conversely, when it is said that one component is "directly joined" or "directly connected" to another component, it should be understood that no other components are arranged between them.

[0044] The terminology used in this invention is for describing specific exemplary embodiments only and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly specifies otherwise. In this invention, terms such as “comprising” or “having” are intended to indicate the presence of features, values, steps, operations, components, parts or combinations thereof described in the specification, but it should be understood that these terms do not exclude the presence or addition of one or more features, values, steps, operations, components, parts or combinations thereof.

[0045] 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. Terms that are commonly used and appear in dictionaries shall be interpreted as having the meaning appropriate to the context in this art. In this specification, terms are not necessarily construed as having a formal meaning unless explicitly defined.

[0046] The form of the invention will be described in detail below with reference to the accompanying drawings. In describing the invention, for the purpose of providing a full understanding of the invention, the same reference numerals refer to the same elements throughout the description of the drawings, and repeated descriptions will be omitted.

[0047] Figure 1 This is a conceptual diagram illustrating a V2X communication scenario.

[0048] 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 system 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.

[0049] V2V communication can include communication between a first vehicle 100 (e.g., a communication node located in vehicle 100) and a second vehicle 110 (e.g., a communication node located in vehicle 110). Various driving information, such as speed, direction of travel, time, and position, can be exchanged between vehicles 100 and 110 via V2V communication. For example, 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.

[0050] V2I communication may include communication between a first vehicle 100 (e.g., a communication node located in vehicle 100) and roadside infrastructure (e.g., a roadside unit (RSU)) 120. Infrastructure 120 may also include traffic lights or streetlights located on the roadside. For example, when performing V2I communication, communication can occur between a communication node located in the first vehicle 100 and a communication node located in a traffic light. Traffic information, driving information, etc., can be exchanged between the first vehicle 100 and infrastructure 120 via V2I communication. V2I communication supported in the cellular communication system 140 can also be performed based on sidelink communication technologies (e.g., ProSe and D2D communication technologies). In this case, communication between vehicle 100 and infrastructure 120 can be performed using at least one sidelink channel established between vehicle 100 and infrastructure 120.

[0051] V2P communication can include communication between a first vehicle 100 (e.g., a communication node located in vehicle 100) and a person 130 (e.g., a communication node carried by person 130). V2P communication can be used to exchange driving information of the first vehicle 100 and movement information of the person 130, such as speed, direction of travel, time, and location. Based on the obtained driving and movement information, a dangerous situation can be determined, and the communication node located in vehicle 100 or the communication node carried by person 130 can generate an alarm indicating danger. V2P 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 the communication node located in vehicle 100 and the communication node carried by person 130 can be performed using at least one sidelink channel established between the communication nodes.

[0052] V2N communication can be communication between a first vehicle 100 (e.g., a communication node located in vehicle 100) and a server connected via a cellular communication system 140. V2N communication can be performed based on 4G communication technologies (e.g., LTE or LTE-A) or 5G communication technologies (e.g., NR). Furthermore, V2N communication can be performed based on Wireless Access in Vehicular Environments (WAVE) communication technologies, or Wireless Local Area Network (WLAN) communication technologies as defined in IEEE 802.11, or Wireless Personal Area Network (WPAN) communication technologies as defined in IEEE 802.15.

[0053] On the other hand, the cellular communication system 140 that supports V2X communication can be configured as follows.

[0054] Figure 2 This is a conceptual diagram illustrating an exemplary implementation of a cellular communication system.

[0055] 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, relay station 220, user equipment (UE) 231 to 236, etc. UE 231 to UE 236 may include [missing information - likely related to a specific location or component]. Figure 1 The communication nodes in vehicles 100 and 110, located in Figure 1 The communication nodes in the infrastructure 120, by Figure 1 The core network may include communication nodes carried by the person 130, etc. When the cellular communication system supports 4G communication technology, the core network may include a serving gateway (S-GW) 250, a packet data network (PDN) gateway (P-GW) 260, a mobility management entity (MME) 270, etc.

[0056] When the 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-standalone (NSA) mode, the core network consisting of S-GW 250, P-GW 260, and MME 270 can support both 5G and 4G communication technologies, and the core network consisting of UPF 250, SMF 260, and AMF 270 can support both 4G and 5G communication technologies.

[0057] 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.

[0058] Communication nodes in cellular communication systems (e.g., base stations, relay stations, UEs, S-GWs, P-GWs, MMEs, UPFs, SMFs, AMFs, etc.) can perform communication by utilizing at least one of the following communication technologies: Code Division Multiple Access (CDMA), 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), Filter Bank Multicarrier (FBMC), Universal Filtered Multicarrier (UFMC), and Space Division Multiple Access (SDMA).

[0059] The communication nodes of the cellular communication system (e.g., base stations, relay stations, UEs, S-GWs, P-GWs, MMEs, UPFs, SMFs, AMFs, etc.) can be configured as follows.

[0060] Figure 3 This is a conceptual diagram illustrating an exemplary implementation of a communication node constituting a cellular communication system.

[0061] like Figure 3As shown, the communication node 300 may include at least one processor 310, a memory 320, and a transceiver 330 connected to a network for performing communication. Furthermore, the communication node 300 may further include an input interface device 340, an output interface device 350, and a storage device 360, etc. Each component included in the communication node 300 can communicate with each other when connected via a bus 370.

[0062] However, each component included in the communication node 300 can be connected to the processor 310 via a separate interface or a separate bus instead of the common bus 370. For example, the processor 310 can be connected to at least one of the memory 320, transceiver 330, input interface device 340, output interface device 350, and storage device 360 ​​via a dedicated interface.

[0063] Processor 310 can execute at least one instruction stored in at least one of memory 320 and storage device 360. Processor 310 can refer to a central processing unit (CPU), graphics processing unit (GPU), or dedicated processor that performs methods according to embodiments of the present invention thereon. Each of memory 320 and storage device 360 ​​may include at least one volatile storage medium and a non-volatile storage medium. For example, memory 320 may include at least one read-only memory (ROM) and random access memory (RAM).

[0064] Refer again Figure 2 In the communication system, base station 210 can form macro cells or small cells 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 UE 236 and relay station 220, and can also transmit signals received from UEs 231 to UE 236 and relay station 220 to the core network. UEs #1 231, UE #2 232, UE #4 234, UE #5 235, and UE #6 236 can belong to 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 base station 210. 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.

[0065] Relay station 220 can connect to base station 210 and relay communication between base station 210 and UE#3 233 and UE#4 234. That is, relay station 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 relay station 220, and UE#3 233 can be within the cell coverage area of ​​relay station 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 relay station 220 by performing a connection establishment procedure. After connecting to relay station 220, UE#3 233 and UE#4 234 can communicate with relay station 220.

[0066] Base station 210 and relay station 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 relay station 220 and operations supported by relay station 220.

[0067] Here, base station 210 can refer to Node B (NB), evolved Node B (eNB), base transceiver station (BTS), radio remote headend (RRH), transmit receiver point (TRP), radio unit (RU), roadside unit (RSU), radio transceiver, access point, access node, etc. Relay station 220 can refer to small base station or relay node, etc. Each of UE#1 231 to UE#6 236 can refer to terminal, access terminal, mobile terminal, station, user station, mobile station, portable user station, node, device, on-broad unit (OBU), etc.

[0068] On the other hand, communication between UE#5 235 and UE#6 236 can be performed based on sidelink communication technology. Sidelink communication can be performed using a one-to-one or one-to-many scheme. When performing V2V communication using sidelink communication technology, UE#5 235 can be located at... Figure 1 The communication node in the first vehicle 100, and UE#6 236 may be located in Figure 1 The communication node in the second vehicle 110. When performing V2I communication using sidelink communication technology, UE#5 235 can be located in Figure 1 The communication node in the first vehicle 100, and UE#6 236 may 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 the first vehicle 100, and UE#6 236 can be... Figure 1 The communication node carried by person 130.

[0069] The scenarios for applying sidelink communication can be categorized based on the location of the UEs participating in the sidelink communication (e.g., UE#5 235 and UE#6 236), as shown in Table 1 below. For example, Figure 2 The sidelink communication scenario between UE#5 235 and UE#6 236 shown in the figure can be sidelink communication scenario C.

[0070] [Table 1]

[0071]

[0072] On the other hand, the user plane protocol stack of a UE performing sidelink communication (e.g., UE#5 235 and UE#6 236) can be configured as follows.

[0073] Figure 4 This is a block diagram illustrating an exemplary implementation of the user plane protocol stack of a UE performing sidelink communication.

[0074] like Figure 4 As shown, the UE on the left can be Figure 2 The UE shown is UE#5 235, and the UE on the right 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 for 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.

[0075] Sidelink communication between UE#5 235 and UE#6 236 can be performed using a PC5 interface (e.g., PC5-U interface). Layer 2 identifiers (IDs) (e.g., source Layer 2 ID, destination Layer 2 ID) can be used for sidelink communication, and these IDs can be IDs configured for V2X communication (e.g., V2X services). Furthermore, hybrid Automatic Repeat Request (HARQ) feedback operations can be supported in sidelink communication, and both RLC acknowledged mode (RLC AM) and RLC unacknowledged mode (RLC UM) can be supported.

[0076] 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.

[0077] Figure 5 This is a block diagram illustrating a first exemplary implementation of the control plane protocol stack of a UE performing sidelink communication. Figure 6 This is a block diagram illustrating a second exemplary implementation of the control plane protocol stack of a UE performing sidelink communication.

[0078] like Figure 5 and Figure 6 As shown, the UE on the left can be Figure 2 The UE shown is UE#5 235, and the UE on the right can be... Figure 2 The UE#6 236 shown is an example. 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. 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)).

[0079] 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.

[0080] 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.

[0081] PSDCH can be used in the discovery process. For example, discovery signals can be transmitted via PSDCH. PSBCH can be used to send and receive broadcast information (e.g., system information). Furthermore, demodulation reference signals (DM-RS), 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).

[0082] On the other hand, the side link transmission mode (TM) can be classified into side link TM#1 to TM#4, as shown in Table 2 below.

[0083] [Table 2]

[0084] Side Link™ illustrate #1 Transmission utilizing resources scheduled by the base station #2 Automatic transmission of UE without base station scheduling #3 Transmission that utilizes resources scheduled by the base station in V2X communication #4 Automatic UE transmission in V2X communication without base station scheduling

[0085] 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. A resource pool can be configured for each sidelink control information and sidelink data.

[0086] Resource pools for receiving 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 using a broadcast RRC signaling procedure. When sidelink TM#3 is supported, the resource pool for transmitting sidelink control information can be configured using a dedicated RRC signaling procedure. In this case, sidelink control information can be transmitted 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 transmitting sidelink control information can be configured using either a dedicated RRC signaling procedure or a broadcast RRC signaling procedure. In this case, sidelink control information can be transmitted using resources automatically selected by the UE (e.g., UE#5 235 or UE#6 236) within the resource pool configured by the dedicated RRC signaling procedure or the broadcast RRC signaling procedure.

[0087] 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 automatically selected by the UE (e.g., UE#5 235 or UE#6 236) within the resource pool configured by the dedicated RRC signaling procedure or the broadcast RRC signaling procedure.

[0088] The sidelink communication method will be described below. Even when describing a method to be performed at a first communication node (e.g., transmitting or receiving a signal), the corresponding second communication node can also perform a method corresponding to the method performed at the first communication node (e.g., receiving or transmitting a signal). 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 embodiment described below, the operation of the vehicle can be the operation of a communication node located in the vehicle.

[0089] In an exemplary implementation, 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 “higher-layer messages” or “higher-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 element (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).

[0090] Sidelink signals can be synchronization signals and reference signals used for sidelink communication. For example, synchronization signals can be synchronization signal / physical broadcast channel (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), DM-RS, phase tracking reference signals (PT-RS), cell specific reference signals (CRS), sounding reference signals (SRS), discovery reference signals (DRS), etc.

[0091] 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.

[0092] Sidelink communication can be performed using either a single SCI scheme or a multi-SCI scheme. When using a single SCI scheme, data transmission (e.g., sidelink data transmission, sidelink shared channel (SL-SCH) transmission) can be performed based on one SCI (e.g., a first-stage SCI). When using a multi-SCI scheme, data transmission can be performed using two SCIs (e.g., a first-stage SCI and a second-stage SCI). SCIs can be transmitted on the PSCCH and / or PSSCH. When using a single SCI scheme, SCIs (e.g., first-stage SCIs) can be transmitted on the PSCCH. When using a multi-SCI scheme, a first-stage SCI can be transmitted on the PSCCH, and a second-stage SCI can be transmitted on either the PSCCH or PSSCH. The first-stage SCI can be referred to as "first-stage SCI," and the second-stage SCI can be referred to as "second-stage SCI." The first-stage SCI format can include SCI format 1-A, and the second-stage SCI format can include SCI format 2-A and SCI format 2-B.

[0093] The first-stage SCI may include one or more information elements such as 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 information elements such as HARQ processor identifier (ID), redundancy version (RV), source ID, destination ID, CSI request information, area ID, and communication range requirements.

[0094] On the other hand, the sending terminal can perform SL communication with the receiving terminal. SL communication between the sending and receiving terminals can be performed in a unicast scheme. The sending terminal can refer to a terminal that sends data (e.g., SL data) via a side link. That is, the sending terminal can refer to the source terminal. The receiving terminal can refer to a terminal that receives SL data via a side link. That is, the receiving terminal can refer to the destination terminal. When relay communication (e.g., SL relay communication) is required during SL communication between the sending and receiving terminals, a connection between the sending terminal and the relay terminal can be configured, and a connection between the receiving terminal and the relay terminal can also be configured. When the above connection configuration is completed, SL relay communication can be performed.

[0095] A relay terminal can support SL relay communication between a sending terminal and a receiving terminal. When a specific event occurs, the relay terminal may determine that it does not support relay functions (e.g., SL relay communication). Alternatively, there may be situations where the relay terminal cannot support relay functions (e.g., SL relay communication). In such cases, it may be necessary to perform SL relay communication through a new relay terminal. The method for SL relay communication through a new relay terminal will be described below.

[0096] Figure 7a and Figure 7b A sequence diagram of a first exemplary embodiment of a method for SL relay communication via a new relay terminal is shown.

[0097] like Figure 7a and Figure 7b As shown, the communication system may include a transmitting terminal, a receiving terminal, a first relay terminal, and a second relay terminal. Each of the transmitting terminal, receiving terminal, first relay terminal, and second relay terminal can communicate with... Figure 3 The communication nodes 300 shown are configured identically or similarly. The transmitting terminal, receiving terminal, first relay terminal, and second relay terminal can support... Figures 4 to 6 The protocol stack is shown. The sending terminal can be a terminal that sends data (e.g., SL data), and the receiving terminal can be a terminal that receives data (e.g., SL data). Each of the first and second relay terminals can be a terminal that relays SL communication between the sending and receiving terminals. The second relay terminal can be a new relay terminal.

[0098] A connection (e.g., a unicast link) can be configured between the sending terminal and the first relay terminal, and SL communication between the sending terminal and the first relay terminal can be performed in a unicast scheme. A connection (e.g., a unicast link) can be configured between the receiving terminal and the first relay terminal, and SL communication between the receiving terminal and the first relay terminal can be performed in a unicast scheme. In step S701, SL relay communication can be performed between the sending terminal, the first relay terminal, and the receiving terminal.

[0099] When a specific event occurs, the first relay terminal may determine that it does not support relay functions (e.g., SL relay communication). Alternatively, it is possible that the first relay terminal cannot support relay functions (e.g., SL relay communication). In the above situation, the first relay terminal may send a first message (S702) to the sending terminal and / or receiving terminal, including a "relay cancellation indicator" indicating that SL relay communication is not supported by the first relay terminal. The relay cancellation indicator may indicate that the first relay terminal will stop SL relay communication. In addition, the relay cancellation indicator may be used to request the sending terminal and / or receiving terminal to configure a connection with a new relay terminal (e.g., a second relay terminal).

[0100] The first message can be an RRCReconfigurationRequestSidelink message, and the RRCReconfigurationRequestSidelink message can include one or more information elements listed in Table 3 below. In step S702, another RRC message (e.g., an existing RRC message or a new RRC message) can be used instead of the RRCReconfigurationRequestSidelink message. Alternatively, the first message can be a MAC control element (CE) or control information (e.g., SCI). In Table 3 below, RelayRelease-indication can be a relay release indicator. The RRCReconfigurationRequestSidelink message can be used to convey the RelayRelease-indication.

[0101] [Table 3]

[0102]

[0103] The sending terminal and / or receiving terminal may receive a first message from the first relay terminal and may determine, based on a relay cancellation indicator included in the first message, that the first relay terminal does not support (e.g., does not perform) SL relay communication. In this case, the sending terminal may stop sending data (e.g., SL data, unicast traffic) to the first relay terminal. Furthermore, the first relay terminal may stop relaying data from the sending terminal, and the receiving terminal may stop receiving data from the first relay terminal.

[0104] The transmitting terminal can perform a new relay terminal discovery process (S703). For example, the transmitting terminal can identify a neighboring relay terminal by receiving a signal and / or channel from a neighboring relay terminal. Here, the signal can be at least one of a discovery signal, a reference signal, or a synchronization signal, and the channel can be a discovery channel. The transmitting terminal can select one neighboring relay terminal (e.g., the best neighboring relay terminal) from the identified neighboring relay terminals, and can determine the selected neighboring relay terminal as a new relay terminal. Here, the new relay terminal can be a second relay terminal.

[0105] The transmitting terminal can configure a connection with the second relay terminal (e.g., a PC5 connection or a PC5-S connection) (S704). In step S704, the transmitting terminal can identify the identifier of the second relay terminal. The identifier of the second relay terminal can be a Layer 2 (L2) identifier and / or a ProSe UE ID (e.g., a ProSe application code or a ProSe application ID). The ProSe UE ID can correspond to the L2 identifier. The ProSe UE ID can be an identifier recognizable by a higher layer. Since the transmission operation of discovery messages (e.g., discovery signal or discovery channel) can be performed in higher and / or lower layers (e.g., PDCP, RRC, or MAC layers), in order to support the transmission operation of discovery messages, the identifier of the second relay terminal can be an L2 identifier, a ProSe UE ID, or a combination of an L2 identifier and a ProSe UE ID.

[0106] When the connection configuration between the sending terminal and the second relay terminal is complete, the sending terminal can send a second message to the first relay terminal. The second message includes information about the second relay terminal (e.g., its identifier) ​​and / or a relay configuration completion indicator (S705) indicating that the connection configuration between the sending terminal and the second relay terminal is complete. The relay configuration completion indicator can indicate that the sending terminal's data is relayed to the receiving terminal via the second relay terminal. The second message can be sent to the receiving terminal via the first relay terminal. In other words, the second message can be used to notify the receiving terminal of the information about the second relay terminal (i.e., the new relay terminal).

[0107] The second message can be the RRCReconfigurationSidelink message as defined in Table 4 below, and may include one or more information elements listed in Table 4 below. In step S705, another RRC message (e.g., a new RRC message) can be used instead of the RRCReconfigurationSidelink message. Alternatively, the second message can be a MAC CE and / or control information.

[0108] [Table 4]

[0109]

[0110]

[0111] In Table 4, sl-RelayUE-Identity can be the identifier of the second relay terminal (i.e., the new relay terminal). In Table 4, RelayLinkRefresh-Indication can be a relay configuration completion indicator. RelayLinkRefresh-Indication indicates that the connection configuration between the transmitting terminal and the relay terminal indicated by sl-RelayUE-Identity has been completed. RelayLinkRefresh-Indication can be represented using either an enumeration (ENUMERATED) type or a boolean (BOOLEAN) type.

[0112] Furthermore, the second message may include a number (hereinafter referred to as the "last data number") used to identify the data last sent from the sending terminal to the receiving terminal via the first relay terminal. The last data number may be a superframe number. The last data number can be used by the receiving terminal to determine whether data has been lost. Alternatively, when receiving an RRCReconfigurationComplete message from the receiving terminal via the first relay terminal, the sending terminal may send a separate message including the last data number (e.g., a superframe number) to the receiving terminal via the first relay terminal. The receiving terminal may receive the separate message from the first relay terminal after sending the RRCReconfigurationComplete message, identify the last data number included in the separate message, and determine whether data has been lost based on the last data number.

[0113] On the other hand, the first relay terminal can receive a second message from the sending terminal. The first relay terminal can identify information elements included in the second message (e.g., information of the second relay terminal, relay configuration completion indicator, and / or last data number). The first relay terminal can send the second message to the receiving terminal (S706). The information elements included in the second message sent from the first relay terminal can be the same as the information elements included in the second message sent from the sending terminal. Alternatively, the information elements included in the second message sent from the first relay terminal can be different from the information elements included in the second message sent from the sending terminal. For example, the second message sent from the first relay terminal can further include information (e.g., an identifier) ​​of the sending terminal that transmits information about a new relay terminal (e.g., the second relay terminal). The second message sent from the first relay terminal can be an RRCReconfigurationSidelink message as defined in Table 5 below, and can include one or more information elements described in Table 5 below. In Table 5 below, sl-SourceUE-Identity can be the identifier of the sending terminal. The identifier of the transmitting terminal can be an L2 identifier, a ProSe UE ID, a ProSe application code, and / or a ProSe application ID.

[0114] [Table 5]

[0115]

[0116]

[0117] The receiving terminal can receive a second message from the sending terminal from the first relay terminal and identify the information elements included in the second message (e.g., information about the second relay terminal, a relay configuration completion indicator, the last data number, and / or information about the sending terminal). The receiving terminal can identify, based on the information elements included in the second message, that the configuration of the connection (e.g., a unicast link) between the sending terminal and the second relay terminal (e.g., a new relay terminal) has been completed. The receiving terminal can perform a discovery process for the second relay terminal indicated by the information elements included in the second message (S707). For example, the receiving terminal can identify the identifier of a neighboring relay terminal by receiving signals and / or channels from neighboring relay terminals. The signals can be discovery signals, synchronization signals, and / or reference signals, and the channels can be discovery channels.

[0118] The receiving terminal can compare the identifier of the adjacent relay terminal with the identifier of the second relay terminal included in the second message. Here, a higher layer of the receiving terminal can compare the Prose UE ID (e.g., ProSe application code or ProSe application ID) of the adjacent relay terminal with the Prose UE ID (e.g., ProSe application code or ProSe application ID) of the second relay terminal. Alternatively, a lower layer (e.g., L2) of the receiving terminal can compare the L2 identifier of the adjacent relay terminal with the L2 identifier of the second relay terminal.

[0119] When a neighboring relay terminal with the same identifier as the second relay terminal is identified, the receiving terminal can determine the identified neighboring relay terminal as the second relay terminal. The receiving terminal can configure a connection with the second relay terminal (e.g., a PC5 connection, a PC5-S connection, or a unicast link) (S708). When the connection configuration between the receiving terminal and the second relay terminal is complete, the receiving terminal can send a third message to the first relay terminal, the third message including information about the second relay terminal (e.g., the identifier of the second relay terminal) and / or a relay configuration completion indicator indicating that the connection configuration between the receiving terminal and the second relay terminal is complete (S709). The third message can be sent from the first relay terminal to the sending terminal. The third message can be the RRCReconfigurationCompleteSidelink message as defined in Table 6 below, and can include one or more information elements listed in Table 6 below. In S709, another RRC message (e.g., a new RRC message) can be used instead of the RRCReconfigurationCompleteSidelink message. Alternatively, the third message can be MAC CE and / or control information. In Table 6 below, sl-RelayUE-Identity can be the identifier of the second relay terminal, and in Table 6 below, RelayLinkRefresh-Indication can be the relay configuration completion indicator. RelayLinkRefresh-Indication can be represented by an enumeration type or a boolean type.

[0120] [Table 6]

[0121]

[0122]

[0123] On the other hand, the receiving terminal can identify whether data has been lost in SL relay communication via the first relay terminal based on the last data number included in the second message. When the number used to identify the last data received from the first relay terminal is the same as the last data number included in the second message, the receiving terminal can determine that no data was lost in the SL relay communication. When the number used to identify the last data received from the first relay terminal is different from the last data number included in the second message, the receiving terminal can determine that data has been lost in the SL relay communication. In this case, the receiving terminal can notify the sending terminal of the number used to identify the last data received from the first relay terminal (e.g., the last data number). The receiving terminal can request the sending terminal to retransmit the data corresponding to the last data number by notifying the sending terminal of the last data number. The last data number can be included in a third message (e.g., an RRCReconfigurationCompleteSidelink message).

[0124] Alternatively, the receiving terminal can generate a separate message including the last data number and send the separate message to the sending terminal via the first relay terminal. Alternatively, when the connection configuration between the receiving terminal and the second relay terminal fails, the receiving terminal can send an RRCReconfigurationFailure message to the sending terminal via the first relay terminal. Here, the RRCReconfigurationFailure message may include the last data number of the receiving terminal. The sending terminal can identify the last data number of the receiving terminal by receiving a third message, the separate message, and / or the RRCReconfigurationFailure message from the first relay terminal, and resend the data corresponding to the last data number to the receiving terminal. The data retransmission operation can be performed by either the first relay terminal or the second relay terminal. The data retransmission operation can be performed when the number used to identify the last data sent by the sending terminal via the first relay terminal is different from the last data number received from the receiving terminal.

[0125] On the other hand, the first relay terminal can receive a third message from the receiving terminal. The first relay terminal can identify information elements included in the third message (e.g., information about the second relay terminal, a relay configuration completion indicator, and / or the last data number). The first relay terminal can send the third message to the sending terminal (S710). After sending the third message to the sending terminal, the first relay terminal can disconnect the connection between the sending terminal and itself (e.g., unicast link) and the connection between the receiving terminal and itself (e.g., unicast link). Furthermore, the sending terminal can disconnect the connection configuration between itself and the first relay terminal after receiving the third message. The receiving terminal can disconnect the connection configuration between itself and the first relay terminal after sending the third message.

[0126] Information elements included in a third message transmitted from a first relay terminal may be the same as information elements included in a third message transmitted from a receiving terminal. Alternatively, information elements included in a third message transmitted from a first relay terminal may be different from information elements included in a third message transmitted from a receiving terminal. For example, the third message transmitted from the first relay terminal may further include information (e.g., an identifier) ​​of the receiving terminal that transmits information about a new relay terminal (e.g., a second relay terminal). The third message transmitted from the first relay terminal may be an RRCReconfigurationCompleteSidelink message as defined in Table 7 below, and may include one or more information elements described in Table 7 below. In Table 7 below, sl-DestinationUE-Identity may be the identifier of the receiving terminal. The identifier of the receiving terminal may be an L2 identifier, ProSe UE ID, ProSe application code, and / or ProSe application ID.

[0127] [Table 7]

[0128]

[0129]

[0130] The sending terminal can receive a third message from the first relay terminal and identify the information elements included in the third message (e.g., information about the second relay terminal, a relay configuration completion indicator, the last data number, and / or information about the receiving terminal). The sending terminal can identify that the connection configuration between the receiving terminal and the second relay terminal has been completed based on the information elements included in the third message. In this case, SL relay communication (S711) can be performed between the sending terminal, the second relay terminal, and the receiving terminal. The sending terminal can send new data to the receiving terminal through the second relay terminal, and the receiving terminal can receive new data from the sending terminal through the second relay terminal. When data is lost during SL relay communication through the first relay terminal, the sending terminal can retransmit the lost data to the receiving terminal through the second relay terminal before sending new data. On the other hand, if the third message from the receiving terminal is not received, the sending terminal may not be able to perform SL relay communication through the second relay terminal.

[0131] At the same time, Figure 7a and Figure 7b In the exemplary embodiment shown, when it is determined that the first relay terminal cannot support SL relay communication, data transmission through the first relay terminal can be stopped. Alternatively, even when it is determined that the first relay terminal cannot support SL relay communication, data transmission through the first relay terminal can continue uninterrupted. The SL relay communication described above can be performed as follows. That is, in the following... Figure 8a and Figure 8b In the exemplary embodiment shown, even when it is determined that the first relay terminal cannot support SL relay communication, data transmission through the first relay terminal can be performed before data transmission through a new relay terminal (e.g., a second relay terminal) is performed.

[0132] Figure 8a and Figure 8b A sequence diagram of a second exemplary embodiment of a method for SL relay communication via a new relay terminal is shown.

[0133] like Figure 8a and Figure 8b As shown, the communication system may include a transmitting terminal, a receiving terminal, a first relay terminal, and a second relay terminal. Each of the transmitting terminal, receiving terminal, first relay terminal, and second relay terminal can communicate with... Figure 3 The communication nodes 300 shown are configured identically or similarly. The transmitting terminal, receiving terminal, first relay terminal, and second relay terminal can support... Figures 4 to 6The protocol stack is shown. The sending terminal can be a terminal that sends data (e.g., SL data), and the receiving terminal can be a terminal that receives data (e.g., SL data). Each of the first and second relay terminals can be a terminal that relays SL communication between the sending and receiving terminals. The second relay terminal can be a new relay terminal.

[0134] The connection between the sending terminal and the first relay terminal can be configured (e.g., a unicast link), and SL communication between the sending terminal and the first relay terminal can be performed in a unicast scheme. The connection between the receiving terminal and the first relay terminal can be configured (e.g., a unicast link), and SL communication between the receiving terminal and the first relay terminal can be performed in a unicast scheme. SL relay communication between the sending terminal, the first relay terminal, and the receiving terminal can be performed (S801).

[0135] When a specific event occurs, the first relay terminal may determine that it does not support relay functions (e.g., SL relay communication). Alternatively, it is possible that the first relay terminal cannot support relay functions (e.g., SL relay communication). In the above situation, the first relay terminal may send a first message (S802) to the sending terminal and / or receiving terminal, including a "relay release indicator" indicating that the first relay terminal does not support SL relay communication. The relay release indicator may indicate that data transmission through the first relay terminal is permitted until the connection configuration with a new relay terminal (e.g., the second relay terminal) is completed. In this case, the sending terminal can send data through the first relay terminal until the connection configuration between the receiving terminal and the new relay terminal is completed (e.g., until a third message including a relay configuration completion indicator is received). Furthermore, the relay release indicator may be used to request the sending terminal and / or receiving terminal to configure the connection with the new relay terminal (e.g., the second relay terminal).

[0136] The first message can be an RRCReconfigurationRequestSidelink message, and the RRCReconfigurationRequestSidelink message can include one or more information elements listed in Table 8 below. In step S802, another RRC message (e.g., an existing RRC message or a new RRC message) can be used instead of the RRCReconfigurationRequestSidelink message. Alternatively, the first message can be a MAC CE or control information. In Table 3 below, ADCS-RelayRelease-indication can be a relay release indicator. The RRCReconfigurationRequestSidelink message can be used to convey the ADCS-RelayRelease-indication. “ADCS” can refer to “after dual-connection setup”.

[0137] [Table 8]

[0138]

[0139]

[0140] The sending terminal and / or receiving terminal can receive a first message from the first relay terminal and can determine, based on the relay release indicator included in the first message, that the first relay terminal does not support (e.g., does not perform) SL relay communication. When the relay release indicator is ADCS-RelayRelease-Indication, the sending terminal can continue to send data (e.g., SL data, unicast traffic) through the first relay terminal. Data transmission through the first relay terminal can be performed until a connection with a new relay terminal is configured. Furthermore, the first relay terminal can relay the sending terminal's data until a connection between the sending / receiving terminal and the new relay terminal is configured. The receiving terminal can perform the operation of receiving data from the first relay terminal until a connection with the new relay terminal is configured.

[0141] The transmitting terminal can perform a new relay terminal discovery process (S803). For example, the transmitting terminal can identify a neighboring relay terminal by receiving a signal and / or channel from a neighboring relay terminal. Here, the signal can be at least one of a discovery signal, a reference signal, or a synchronization signal, and the channel can be a discovery channel. The transmitting terminal can select one neighboring relay terminal from the identified neighboring relay terminals (e.g., the best neighboring relay terminal) and can determine the selected neighboring relay terminal as a new relay terminal. Here, the new relay terminal can be a second relay terminal.

[0142] The transmitting terminal can configure a connection with the second relay terminal (e.g., a PC5 connection or a PC5-S connection) (S804). In step S804, the transmitting terminal can identify the identifier of the second relay terminal. The identifier of the second relay terminal can be an L2 identifier and / or a ProSe UE ID (e.g., a ProSe application code or a ProSe application ID). The ProSe UE ID can correspond to the L2 identifier. The ProSe UE ID can be an identifier recognizable by a higher layer. Since the transmission operation of discovery messages (e.g., discovery signal or discovery channel) can be performed in higher and / or lower layers (e.g., PDCP, RRC, or MAC layers), in order to support the transmission operation of discovery messages, the identifier of the second relay terminal can be an L2 identifier, a ProSe UE ID, or a combination of an L2 identifier and a ProSe UE ID.

[0143] When the connection configuration between the sending terminal and the second relay terminal is complete, the sending terminal can send a second message to the first relay terminal (S805). The second message includes information about the second relay terminal (e.g., an identifier of the second relay terminal) and / or a relay configuration completion indicator indicating that the connection configuration between the sending terminal and the second relay terminal is complete. Additionally, the second message may further include ADCS-RelayRelease-Indication to indicate that data transmission through the first relay terminal will continue until data transmission through the new relay terminal is executed. The second message can be sent to the receiving terminal through the first relay terminal. In other words, the second message can be used to notify the receiving terminal of information about the second relay terminal (i.e., the new relay terminal).

[0144] The second message can be the RRCReconfigurationSidelink message as defined in Table 9 below, and may include one or more information elements listed in Table 9 below. In S805, another RRC message (e.g., a new RRC message) can be used instead of the RRCReconfigurationSidelink message. Alternatively, the second message can be MACCE and / or control information.

[0145] [Table 9]

[0146]

[0147]

[0148] In Table 9, sl-RelayUE-Identity can be the identifier of the second relay terminal (i.e., the new relay terminal). In Table 9, RelayLinkRefresh-Indication can be a relay configuration completion indicator. RelayLinkRefresh-Indication indicates that the connection configuration between the transmitting terminal and the relay terminal indicated by sl-RelayUE-Identity has been completed. RelayLinkRefresh-Indication can be represented by an enumeration type or a Boolean type.

[0149] The first relay terminal can receive a second message from the sending terminal. The first relay terminal can identify information elements included in the second message (e.g., information about the second relay terminal, a relay configuration completion indicator, and / or a relay cancellation indicator). The first relay terminal can send the second message to the receiving terminal (S806). The information elements included in the second message sent from the first relay terminal can be the same as those included in the second message sent from the sending terminal. Alternatively, the information elements included in the second message sent from the first relay terminal can be different from those included in the second message sent from the sending terminal. For example, the second message sent from the first relay terminal can further include information (e.g., an identifier) ​​of the sending terminal that transmits information about a new relay terminal (e.g., the second relay terminal). The second message sent from the first relay terminal can be an RRCReconfigurationSidelink message as defined in Table 10 below, and can include one or more information elements listed in Table 10 below. In Table 10 below, sl-SourceUE-Identity can be the identifier of the sending terminal. The identifier of the transmitting terminal can be an L2 identifier, a ProSe UE ID, a ProSe application code, and / or a ProSe application ID.

[0150] [Table 10]

[0151]

[0152]

[0153] The receiving terminal can receive a second message from the sending terminal from the first relay terminal and identify the information elements included in the second message (e.g., information about the second relay terminal, a relay configuration completion indicator, a relay cancellation indicator, and / or information about the sending terminal). The receiving terminal can identify, based on the information elements included in the second message, that the configuration of the connection (e.g., a unicast link) between the sending terminal and the second relay terminal (e.g., a new relay terminal) has been completed. The receiving terminal can perform a discovery process for the second relay terminal indicated by the information elements included in the second message (S807). For example, the receiving terminal can identify the identifier of a neighboring relay terminal by receiving signals and / or channels from neighboring relay terminals. The signals can be discovery signals, synchronization signals, and / or reference signals, and the channels can be discovery channels.

[0154] The receiving terminal can compare the identifier of the adjacent relay terminal with the identifier of the second relay terminal included in the second message. Here, a higher layer of the receiving terminal can compare the Prose UE ID (e.g., ProSe application code or ProSe application ID) of the adjacent relay terminal with the Prose UE ID (e.g., ProSe application code or ProSe application ID) of the second relay terminal. Alternatively, a lower layer (e.g., L2) of the receiving terminal can compare the L2 identifier of the adjacent relay terminal with the L2 identifier of the second relay terminal.

[0155] When a neighboring relay terminal with the same identifier as the second relay terminal is identified, the receiving terminal can determine the identified neighboring relay terminal as the second relay terminal. The receiving terminal can configure a connection with the second relay terminal (e.g., a PC5 connection, a PC5-S connection, or a unicast link) (S808). When the connection configuration between the receiving terminal and the second relay terminal is complete, the receiving terminal can send information about the second relay terminal (e.g., the identifier of the second relay terminal) and / or a relay configuration completion indicator indicating that the connection configuration between the receiving terminal and the second relay terminal is complete (S809). A third message can be sent from the first relay terminal to the sending terminal. The third message can be the RRCReconfigurationCompleteSidelink message defined in Table 11 below, and can include one or more information elements listed in Table 11 below. In step S809, another RRC message (e.g., a new RRC message) can be used instead of the RRCReconfigurationCompleteSidelink message. Alternatively, the third message can be a MAC CE and / or control information. In Table 11 below, sl-RelayUE-Identity can be the identifier of the second relay terminal, and in Table 11 below, RelayLinkRefresh-Indication can be the relay configuration completion indicator. RelayLinkRefresh-Indication can be represented by an enumeration type or a boolean type.

[0156] [Table 11]

[0157]

[0158]

[0159] On the other hand, during and / or after the connection configuration operation between the receiving terminal and the second relay terminal, the receiving terminal can receive data from the sending terminal through the first relay terminal. In this case, the number used to identify the last data received from the sending terminal can continue to change. Therefore, the number used to identify the last data received from the sending terminal may not be included in the third message.

[0160] The first relay terminal can receive a third message from the receiving terminal. The first relay terminal can identify information elements included in the third message (e.g., information of the second relay terminal and / or relay configuration completion indicator). The first relay terminal can send the third message to the sending terminal (S810). The information elements included in the third message sent from the first relay terminal can be the same as the information elements included in the third message sent from the receiving terminal. Alternatively, the information elements included in the third message sent from the first relay terminal can be different from the information elements included in the third message sent from the receiving terminal. For example, the third message sent from the first relay terminal can further include information (e.g., an identifier) ​​of the receiving terminal that transmits information of a new relay terminal (e.g., a second relay terminal). The third message sent from the first relay terminal can be an RRCReconfigurationCompleteSidelink message as defined in Table 12 below, and can include one or more information elements listed in Table 12 below. In Table 12 below, sl-DestinationUE-Identity can be the identifier of the receiving terminal. The identifier of the receiving terminal can be an L2 identifier, a ProSe UE ID, a ProSe application code, and / or a ProSe application ID.

[0161] [Table 12]

[0162]

[0163]

[0164] On the other hand, after sending the third message to the sending terminal, the first relay terminal may send a number identifying the last data received from the sending terminal and / or a number identifying the last data sent to the receiving terminal during a pre-configured time period. The pre-configured time period may be the period from the time the first relay terminal sends the third message to the time the sending terminal receives the third message. The first relay terminal may use at least one of an RRC message, a MAC CE, or control information to notify the receiving terminal of the last data number. The above operations may be performed before disconnecting the connection (e.g., unicast link) between the sending terminal and the first relay terminal, and before disconnecting the connection (e.g., unicast link) between the receiving terminal and the first relay terminal. For example, the first relay terminal may disconnect the connection between the sending terminal and the first relay terminal, and the connection between the receiving terminal and the first relay terminal, after notifying the receiving terminal of the last data number.

[0165] The receiving terminal can receive information about the last data number from the first relay terminal, and based on the last data number, the receiving terminal can identify whether data has been lost in the SL relay communication via the first relay terminal. When the number used to identify the last data received from the first relay terminal is the same as the last data number indicated by the first relay terminal, the receiving terminal can determine that no data was lost in the SL relay communication. When the number used to identify the last data received from the first relay terminal is different from the last data number indicated by the first relay terminal, the receiving terminal can determine that data has been lost in the SL relay communication. In this case, the receiving terminal can notify the sending terminal of the number used to identify the last data received from the first relay terminal (e.g., the last data number).

[0166] After notifying the sending terminal of the last data number, the first relay terminal can disconnect the connection between itself and the sending terminal, as well as the connection between the receiving terminal and the first relay terminal. Furthermore, the sending terminal can disconnect the connection configuration between itself and the first relay terminal after receiving a third message and / or data corresponding to the last data number. The receiving terminal can disconnect the connection configuration between itself and the first relay terminal after sending a third message and / or data corresponding to the last data number. The receiving terminal can request the sending terminal to retransmit the data corresponding to the last data number by notifying it of the last data number. The last data number can be sent using at least one of an RRC message, a MAC CE, or a control message. Based on the above operations, service continuity can be guaranteed even if the relay terminal changes.

[0167] On the other hand, the sending terminal can receive a third message from the first relay terminal and identify the information elements included in the third message (e.g., information of the second relay terminal, a relay configuration completion indicator, and / or information of the receiving terminal). The sending terminal can identify that the connection configuration between the receiving terminal and the second relay terminal has been completed based on the information elements included in the third message. In this case, SL relay communication (S811) can be performed between the sending terminal, the second relay terminal, and the receiving terminal. The sending terminal can send new data to the receiving terminal through the second relay terminal, and the receiving terminal can receive the new data from the sending terminal through the second relay terminal. When data is lost during SL relay communication through the first relay terminal, the sending terminal can retransmit the lost data to the receiving terminal through the second relay terminal before sending new data. On the other hand, if the third message from the receiving terminal is not received, the sending terminal may not be able to perform SL relay communication through the second relay terminal.

[0168] Exemplary embodiments of the present invention can be implemented as program instructions that are computer-executable 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 the present invention, or may be known and available to those skilled in the art of computer software.

[0169] 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 machine code produced by, for example, a compiler, and high-level language code executable 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 the present invention, and vice versa.

[0170] While exemplary embodiments of the invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of the invention.

Claims

1. An operation method for a transmitting terminal in a communication system, the operation method comprising: The first relay terminal performs first-side link relay communication with the receiving terminal; Receive a first message from a first relay terminal including a relay release indicator, the relay release indicator including information indicating that data transmission is permitted through the first relay terminal until the connection configuration with the new relay terminal is completed; In response to receiving the first message, the connection between the sending terminal and the second relay terminal, which is the new relay terminal, is configured; A second message is sent from the first relay terminal to the receiving terminal, the second message including a first relay configuration completion indicator indicating that the connection configuration between the sending terminal and the second relay terminal has been completed; A third message is received via a first relay terminal, the third message including a second relay configuration completion indicator indicating that the connection configuration between the receiving terminal and the second relay terminal has been completed; and In response to receiving the third message, a second-side link relay communication is performed between the second relay terminal and the receiving terminal. The sending terminal continuously transmits data through the first relay terminal until the connection configuration between the sending terminal and the second relay terminal is completed. The first relay terminal transmits a number used to identify the last data sent by the sending terminal to the receiving terminal, and after sending the number used to identify the data, the connection configuration between the sending terminal and the first relay terminal is terminated.

2. The operating method according to claim 1, wherein, Upon receiving the first message, the data transmission operation of the sending terminal through the first relay terminal is stopped.

3. The operating method according to claim 1, wherein, Even when the first message is received, the data transmission operation of the sending terminal through the first relay terminal is performed, and the transmission operation is stopped after the third message is received.

4. The operating method according to claim 1, wherein, The second message further includes information about the second relay terminal.

5. The operating method according to claim 1, wherein, The third message further includes at least one of the information from the receiving terminal or the second relay terminal.

6. The operating method according to claim 1, wherein, The configuration of the connection between the transmitting terminal and the second relay terminal includes: Detect one or more adjacent relay terminals; Identify one of the adjacent relay terminals among one or more discovered adjacent relay terminals as the second relay terminal; and Configure the connection with the second relay terminal.

7. The operating method according to claim 1, wherein, Performing second-side link relay communication includes: The data lost in the first-side link relay communication is transmitted to the receiving terminal via the second relay terminal; and New data is sent to the receiving terminal via a second relay terminal.

8. The operating method according to claim 1, wherein, When a third message is received, the connection configuration between the sending terminal and the first relay terminal is terminated.

9. A method for operating a first relay terminal in a communication system, the method comprising: Perform sidelink relay communication between the sending terminal and the receiving terminal; When sidelink relay communication is not supported, a first message including a relay release indicator is sent to the sending terminal. The relay release indicator includes information indicating that data transmission is allowed through the first relay terminal until the connection configuration with the new relay terminal is completed. Receive a second message from the sending terminal, the second message including a first relay configuration completion indicator indicating that the connection configuration between the sending terminal and a second relay terminal, which is a new relay terminal, has been completed; Send a second message to the receiving terminal; A third message is received from the receiving terminal, the third message including a second relay configuration completion indicator indicating that the connection configuration between the receiving terminal and the second relay terminal has been completed; Send a third message to the sending terminal; and After sending the third message, the connection configuration between the sending terminal and the first relay terminal, as well as the connection configuration between the receiving terminal and the first relay terminal, are terminated. The second message further includes at least one piece of information from the sending terminal or the second relay terminal. The first relay terminal continuously transmits data received from the sending terminal to the receiving terminal until the first connection configuration between the sending terminal and the second relay terminal and the second connection configuration between the receiving terminal and the second relay terminal are completed. The first relay terminal transmits a number used to identify the last data sent by the sending terminal to the receiving terminal, and after sending the number used to identify the data, both the first connection configuration and the second connection configuration are terminated.

10. The operating method according to claim 9, wherein, After sending the first message, stop relaying data from the sending terminal.

11. The operating method according to claim 9, wherein, Even after the first message is sent, the data relay operation of the sending terminal is performed, and the relay operation is stopped after the third message is sent.

12. The operating method according to claim 9, wherein, The third message further includes at least one of the information from the receiving terminal or the second relay terminal.

13. An operation method for a receiving terminal in a communication system, the operation method comprising: The first relay terminal performs first-side link relay communication with the sending terminal; Receive a first message from a first relay terminal including a relay release indicator, the relay release indicator including information indicating that data transmission is permitted through the first relay terminal until the connection configuration with the new relay terminal is completed; The second message is received through the first relay terminal, the second message including a first relay configuration completion indicator indicating that the connection configuration between the sending terminal and the second relay terminal has been completed; Configure the connection with the second relay terminal indicated by the second message; A third message is sent from the first relay terminal to the sending terminal, the third message including a second relay configuration completion indicator indicating that the connection configuration between the receiving terminal and the second relay terminal has been completed; and After sending the third message, perform second-side link relay communication between the second relay terminal and the sending terminal. In this process, the receiving terminal continuously receives data through the first relay terminal until the connection configuration between the receiving terminal and the second relay terminal is completed. The receiving terminal receives a number used to identify the last data sent by the sending terminal through the first relay terminal, and after receiving the number used to identify the data, it disconnects the connection configuration between the receiving terminal and the first relay terminal.

14. The operating method according to claim 13, wherein, Upon receiving the first message, the receiving operation of the sending terminal relayed by the first relay terminal is stopped.

15. The operating method according to claim 13, wherein, Even when the first message is received, the receiving operation of the sending terminal relayed by the first relay terminal is performed, and the receiving operation is stopped after the third message is sent.

16. The operating method according to claim 13, wherein, The second message further includes at least one of the information of the sending terminal or the information of the second relay terminal.

17. The operating method according to claim 13, wherein, The third message further includes information about the second relay terminal.

18. The operating method according to claim 13, wherein, Performing second-side link relay communication includes: Data lost in the first-side link relay communication is received via a second relay terminal; and The new data is received from the sending terminal via the second relay terminal.

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