Method and apparatus for adjusting CW size in sidelink communication of unlicensed spectrum

Abstract

Methods and apparatus for adjusting CW size in sidelink communications of unlicensed spectrum are disclosed. The method performed by the transmitting UE comprises the steps of: performing a first LBT operation based on a CW having a first CW size; when the first LBT operation is successful, sending first data to the receiving UE; adjusting the first CW size based on the reference parameter instead of HARQ feedback for the first data; performing a second LBT operation based on the CW having the adjusted CW size; and transmitting second data to the receiving UE when the second LBT operation is successful.

Description

Technical Field

[0001] The present invention relates to a side link communication technology, and more particularly, to a technology for adjusting a contention window (CW) size for a listen before talk (LBT) operation. Background Art

[0002] Communication networks (e.g., 5G communication networks or 6G communication networks) are being developed to provide enhanced communication services compared to existing communication networks (e.g., long term evolution (LTE), LTE-Advanced, etc.). 5G communication networks (e.g., New Radio (NR) communication networks) can support frequency bands below 6 GHz and frequency bands above 6 GHz. In other words, 5G communication networks can support frequency region 1 (FR1) bands and / or FR2 bands. Compared with LTE communication networks, 5G communication networks can support various communication services and scenarios. For example, usage scenarios of 5G communication networks may include enhanced Mobile BroadBand (eMBB), UltraReliable Low Latency Communication (URLLC), massive Machine Type Communication (mMTC), etc.

[0003] Compared with 5G communication networks, 6G communication networks can support a wide variety of communication services and scenarios. 6G communication networks can meet the requirements of ultra-performance, ultra-bandwidth, ultra-space, ultra-precision, ultra-intelligence and / or ultra-reliability. 6G communication networks can support multiple broadband bands and can be applied to various usage scenarios, such as terrestrial communication, non-terrestrial communication, sidelink communication, etc.

[0004] On the other hand, in order to enhance sidelink communication, carrier aggregation (CA) operation, unlicensed band operation, FR2 band operation and / or operation for coexistence between LTE and NR may be considered. In particular, when sidelink communication is performed in an unlicensed band, a method for supporting sidelink communication may be required. For operation in an unlicensed band, optimization of the sidelink physical channel structure may be required. In addition, it may be necessary to improve the listen-before-talk (LBT) operation for sidelink communication in an unlicensed band, as well as a method for adjusting the size of the contention window (CW) for LBT operation. Summary of the invention

[0005] Technical issues

[0006] The present invention is directed to providing a method and apparatus for adjusting a contention window (CW) size for a listen-before-talk (LBT) operation in an unlicensed band sidelink communication.

[0007] Technical Solution

[0008] According to an exemplary embodiment of the present invention, a method for a transmitting user equipment (UE) to achieve the above-mentioned purpose may include: performing a first listen-before-talk (LBT) operation based on a CW having a first contention window (CW) size; sending first data to a receiving UE in response to the success of the first LBT operation; adjusting the first CW size based on a reference parameter instead of a hybrid automatic repeat request (HARQ) feedback for the first data; performing a second LBT operation based on the CW having the adjusted CW size; and sending second data to the receiving UE in response to the success of the second LBT operation.

[0009] The method may further include: receiving a first signaling message including configuration information of a plurality of channel access priority categories (CPAC)-CW tables from a base station; and receiving a second signaling message including configuration information indicating one CAPC-CW table among the plurality of CAPC-CW tables from the base station, wherein the first CW size is a CW size corresponding to the CAPC of the sending UE within the one CAPC-CW table.

[0010] Adjusting the first CW size may include: estimating a distance between a transmitting UE and a receiving UE; and increasing the first CW size in response to the estimated distance being greater than or equal to a threshold, and maintaining or decreasing the first CW size in response to the estimated distance being less than the threshold, wherein the reference parameter is the distance.

[0011] Adjusting the first CW size may include: estimating a reference signal received power (RSRP) based on a signal received from a receiving UE; and increasing the first CW size in response to the estimated RSRP being less than a threshold, and maintaining or decreasing the first CW size in response to the estimated RSRP being greater than or equal to the threshold, wherein the reference parameter is RSRP.

[0012] Adjusting the first CW size may include: identifying the second region where the receiving UE is located; and increasing the first CW size in response to the first region where the sending UE is located being different from the second region, and maintaining or reducing the first CW size in response to the first region being the same as the second region, wherein the reference parameter is the region where each of the sending UE and the receiving UE is located.

[0013] Adjusting the first CW size may include: measuring a channel busy rate (CBR) of a channel between a transmitting UE and a receiving UE; and increasing the first CW size in response to the measured CBR being greater than or equal to a threshold, and maintaining or decreasing the first CW size in response to the measured CBR being less than the threshold, wherein the reference parameter is the CBR.

[0014] Adjusting the first CW size may include: identifying candidate resources that can be utilized by the transmitting UE by performing a resource sensing operation within a resource sensing window; and increasing the first CW size in response to a ratio of the candidate resources to the total resources belonging to the resource sensing window being less than a threshold, and maintaining or reducing the first CW size in response to a ratio of the candidate resources to the total resources being greater than or equal to a threshold, wherein the reference parameter is the number of candidate resources.

[0015] Adjusting the first CW size may include: identifying resources reserved by other UEs by performing a resource sensing operation within a resource sensing window; and increasing the first CW size in response to a ratio of reserved resources to total resources belonging to the resource sensing window being greater than or equal to a threshold, and maintaining or reducing the first CW size in response to a ratio of reserved resources to total resources being less than a threshold, wherein the reference parameter is the number of reserved resources.

[0016] The method may further include: receiving CW configuration information from the base station, wherein the CW configuration information may include at least one information indicating a reference parameter or a threshold for adjusting the first CW size.

[0017] According to an exemplary embodiment of the present invention, a sending user equipment (UE) for achieving the above-mentioned purpose may include: at least one processor, wherein the at least one processor may enable the sending UE to perform: performing a first listen-before-talk (LBT) operation based on a CW having a first contention window (CW) size; sending first data to a receiving UE in response to the success of the first LBT operation; adjusting the first CW size based on a reference parameter instead of a hybrid automatic repeat request (HARQ) feedback for the first data; performing a second LBT operation based on the CW having the adjusted CW size; and sending second data to the receiving UE in response to the success of the second LBT operation.

[0018] At least one processor may further cause the sending UE to execute: receiving a first signaling message including configuration information of a plurality of channel access priority categories (CPAC)-CW tables from the base station; and receiving a second signaling message including configuration information indicating one CAPC-CW table among the plurality of CAPC-CW tables from the base station, wherein the first CW size may be a CW size corresponding to the CAPC of the sending UE within the one CAPC-CW table.

[0019] When adjusting the first CW size, at least one processor can cause the sending UE to perform: estimating the distance between the sending UE and the receiving UE; and increasing the first CW size in response to the estimated distance being greater than or equal to a threshold, and maintaining or reducing the first CW size in response to the estimated distance being less than the threshold, wherein the reference parameter is the distance.

[0020] When adjusting the first CW size, at least one processor may cause the transmitting UE to perform: estimating a reference signal received power (RSRP) based on a signal received from the receiving UE; and increasing the first CW size in response to the estimated RSRP being less than a threshold, and maintaining or reducing the first CW size in response to the estimated RSRP being greater than or equal to the threshold, wherein the reference parameter is RSRP.

[0021] When adjusting the first CW size, at least one processor can cause the sending UE to perform: identifying the second region where the receiving UE is located; and increasing the first CW size in response to the first region where the sending UE is located being different from the second region, and maintaining or reducing the first CW size in response to the first region being the same as the second region, wherein the reference parameter is the region where each of the sending UE and the receiving UE is located.

[0022] When adjusting the first CW size, at least one processor may cause the sending UE to perform: measuring a channel busy rate (CBR) of a channel between the sending UE and the receiving UE; and increasing the first CW size in response to the measured CBR being greater than or equal to a threshold, and maintaining or reducing the first CW size in response to the measured CBR being less than the threshold, wherein the reference parameter is the CBR.

[0023] When adjusting the first CW size, at least one processor can cause the sending UE to perform: identifying candidate resources that can be utilized by the sending UE by performing a resource sensing operation within a resource sensing window; and increasing the first CW size in response to a ratio of the candidate resources to the total resources belonging to the resource sensing window being less than a threshold, and maintaining or reducing the first CW size in response to a ratio of the candidate resources to the total resources being greater than or equal to a threshold, wherein the reference parameter is the number of candidate resources.

[0024] When adjusting the first CW size, at least one processor can cause the sending UE to perform: identifying resources reserved by other UEs by performing a resource sensing operation within a resource sensing window; and increasing the first CW size in response to a ratio of reserved resources to total resources belonging to the resource sensing window being greater than or equal to a threshold, and maintaining or reducing the first CW size in response to a ratio of reserved resources to total resources being less than a threshold, wherein the reference parameter is the number of reserved resources.

[0025] The at least one processor may further cause the transmitting UE to execute: receiving CW configuration information from the base station, wherein the CW configuration information may include at least one information indicating a reference parameter or a threshold for adjusting the first CW size.

[0026] Beneficial Effects

[0027] According to the present invention, in sidelink unlicensed (SL-U) communication, a transmitting terminal can adjust a contention window (CW) size based on a parameter other than hybrid automatic repeat request (HARQ) feedback, and perform a listen-before-talk (LBT) operation based on a CW with the adjusted CW size. Through this operation, the CW size can be adjusted even when HARQ feedback is not received, thereby improving the performance of the communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a conceptual diagram showing a scenario of vehicle-to-everything (V2X) communication.

[0029] Figure 2 is a conceptual diagram illustrating a first exemplary embodiment of a communication system.

[0030] Figure 3 is a conceptual diagram showing a first exemplary embodiment of a communication node constituting a communication system.

[0031] Figure 4 is a block diagram illustrating a first exemplary embodiment of a communication node performing communications.

[0032] Figure 5a is a block diagram illustrating a first exemplary implementation of a transmit path.

[0033] Figure 5b is a block diagram illustrating a first exemplary implementation of a receive path.

[0034] Figure 6 is a block diagram illustrating a first exemplary implementation of a user plane protocol stack of a UE performing sidelink communications.

[0035] Figure 7 is a block diagram illustrating a first exemplary implementation of a control plane protocol stack of a UE performing sidelink communications.

[0036] Figure 8 is a block diagram illustrating a second exemplary embodiment of a control plane protocol stack of a UE performing sidelink communications.

[0037] Fig. 9 is a timing diagram illustrating a first exemplary embodiment of a communication method in an unlicensed band.

[0038] Fig.10 is a sequence listing illustrating a first exemplary embodiment of the SL-U communication method. DETAILED DESCRIPTION

[0039] Since the present invention can be variously modified and can have multiple forms, specific exemplary embodiments will be shown in the drawings and described in detail in the specific embodiments. However, it should be understood that it is not intended to limit the present invention to specific exemplary embodiments, but on the contrary, the present invention covers all modifications and alternative forms that fall within the spirit and scope of the present 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 element. For example, without departing from the scope of the present invention, a first component can be named as a second component, and the second component can also be similarly named as the first component. The term "and / or" means any one or combination of multiple related and described matters.

[0041] In the present invention, "at least one of A and B" may mean "at least one of A or B" or "at least one of a combination of one or more of A and B". In addition, "one or more of A and B" may mean "one or more of A or B" or "one or more of a combination of one or more of A and B".

[0042] In the present invention, "(re)transmission" may refer to "transmission", "retransmission" or "transmission and retransmission", "(re)configuration" may refer to "configuration", "reconfiguration" or "configuration and reconfiguration", "(re)connection" may refer to "connection", "reconnection" or "connection and reconnection", and "(re)access" may refer to "access", "reaccess" or "access and reaccess".

[0043] When it is mentioned that a certain component is "coupled" or "connected" to another component, it should be understood that the certain component is directly "coupled" or "connected" to the other component, or another component may be provided therebetween. On the contrary, when it is mentioned that a certain component is "directly coupled" or "directly connected" to another component, it should be understood that no other component is provided therebetween.

[0044] The terms used in the present invention are only used to describe specific exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as "including" or "having" are intended to indicate the presence of features, quantities, 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, quantities, steps, operations, components, parts, or combinations thereof.

[0045] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the present invention belongs. Terms commonly used in dictionaries and already in dictionaries should be interpreted as having meanings that match the contextual meanings in the art. In this specification, unless explicitly defined, terms are not necessarily interpreted as having formal meanings.

[0046] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, in order to facilitate a comprehensive understanding of the present invention, the same reference numerals refer to the same elements in the description of the entire accompanying drawings, and repeated descriptions thereof will be omitted. Operations of the exemplary embodiments clearly described in the present invention and combinations of the exemplary embodiments, expansions of the exemplary embodiments, and / or variants of the exemplary implementations may be performed. Some operations may be omitted, and the sequence of operations may be changed.

[0047] Even when a method (e.g., transmission or reception of a signal) performed at a first communication node among communication nodes is described in an exemplary embodiment, a corresponding second communication node may perform a method (e.g., reception or transmission of a signal) corresponding to the method performed at the first communication node. That is, when the operation of a user equipment (UE) is described, a base station corresponding thereto may perform an operation corresponding to the operation of the UE. Conversely, when the operation of a base station is described, a corresponding UE may perform an operation corresponding to the operation of the base station.

[0048] A base station may be referred to by various terms, such as node B, evolved node B, next generation node B (gNodeB), gNB, equipment, device, node, communication node, 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. User equipment (UE) may be referred to by various terms, such as terminal, equipment, device, node, communication node, end node, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, on-board unit (OBU), etc.

[0049] In the present invention, signaling may be one of higher layer signaling, MAC signaling and physical (PHY) signaling, or a combination of two or more. A message for higher layer signaling may be referred to as a "higher layer message" or a "higher layer signaling message". A message for MAC signaling may be referred to as a "MAC message" or a "MAC signaling message". A message for PHY signaling may be referred to as a "PHY message" or a "PHY signaling message". Higher layer signaling may refer to the operation of sending and receiving system information (e.g., a master information block (MIB), a system information block (SIB)) and / or an RRC message. MAC signaling may refer to the operation of sending and receiving a MAC control element (CE). PHY signaling may refer to the operation of sending and receiving control information (e.g., downlink control information (DCI), uplink control information (UCI) or sidelink control information (SCI)).

[0050] In the present invention, "configuration of an operation (e.g., sending an operation)" may refer to configuration information (e.g., information element, parameter) required for the operation and / or signaling of information indicating the execution of the operation. "Configuration of an information element (e.g., parameter)" may refer to signaling of an information element. In the present invention, "signal and / or channel" may refer to a signal, a channel, or both a signal and a channel, and "signal" may be used to mean "signal and / or channel".

[0051] The communication network to which the exemplary embodiment is applied is not limited to the communication network described below, and the exemplary embodiment can be applied to various communication networks (e.g., 4G communication network, 5G communication network and / or 6G communication network). Here, "communication network" can be used interchangeably with the term "communication system".

[0052] Figure 1 It is a conceptual diagram showing a scenario of vehicle-to-everything (V2X) communication.

[0053] like Figure 1 As shown, V2X communication may include vehicle-to-vehicle (V2V) communication, vehicle-to-infrastructure (V2I) communication, vehicle-to-pedestrian (V2P) communication, vehicle-to-network (V2N) communication, etc. V2X communication may be supported by a communication system (e.g., a communication network) 140, and V2X communication supported by the communication system 140 may be referred to as "cellular-V2X (C-V2X) communication". Here, the communication system 140 may include a 4G communication system (e.g., an LTE communication system or an LTE-A communication system), a 5G communication system (e.g., an NR communication system), etc.

[0054] V2V communication may include communication between a first vehicle 100 (e.g., a communication node located in the vehicle 100) and a second vehicle 110 (e.g., a communication node located in the vehicle 110). Various driving information such as speed, heading, time, location, etc. may be exchanged between the vehicle 100 and the vehicle 110 through V2V communication. For example, autonomous driving (e.g., platoon driving) may be supported based on the driving information exchanged through V2V communication. V2V communication supported by the communication system 140 may be performed based on a sidelink communication technology (e.g., based on Proximity Based Services (ProSe) and Device-to-Device (D2D) communication technology, etc.). In this case, communication between the vehicle 100 and the vehicle 110 may be performed using at least one sidelink channel.

[0055] V2I communication may include communication between the first vehicle 100 and an infrastructure (e.g., a roadside unit (RSU)) 120 located on the roadside. The infrastructure 120 may include a traffic light or a street light located on the roadside. For example, when performing V2I communication, communication may be performed between a communication node located in the first vehicle 100 and a communication node located in a traffic light. Traffic information, driving information, and the like may be exchanged between the first vehicle 100 and the infrastructure 120 through V2I communication. V2I communication supported by the communication system 140 may be performed based on a sidelink communication technology (e.g., ProSe and D2D communication technology, etc.). In this case, communication between the vehicle 100 and the infrastructure 120 may be performed using at least one sidelink channel.

[0056] V2P communication may include communication between the first vehicle 100 (e.g., a communication node located in the vehicle 100) and the person 130 (e.g., a communication node carried by the person 130). Driving information of the first vehicle 100 and movement information of the person 130, such as speed, forward direction, time, location, etc., may be exchanged between the vehicle 100 and the person 130 through V2P communication. By judging a dangerous situation based on the obtained driving information and movement information, the communication node located in the vehicle 100 or the communication node carried by the person 130 may generate an alarm indicating the danger. V2P communication supported by the communication system 140 may be performed based on a sidelink communication technology (e.g., ProSe and D2D communication technology, etc.). In this case, communication between the communication node located in the vehicle 100 and the communication node carried by the person 130 may be performed using at least one sidelink channel.

[0057] V2N communication may be communication between the first vehicle 100 (e.g., a communication node located in the vehicle 100) and a communication system (e.g., a communication network) 140. V2N communication may be performed based on 4G communication technology (e.g., LTE or LTE-A as described in the 3GPP standard) or 5G communication technology (e.g., NR as described in the 3GPP standard). In addition, V2N communication may be performed based on Wireless Access in Vehicular Environments (WAVE) communication technology or Wireless Local Area Network (WLAN) communication technology defined in Institute of Electrical and Electronics Engineers (IEEE) 802.11, Wireless Personal Area Network (WPAN) communication technology defined in IEEE 802.15, and the like.

[0058] On the other hand, the communication system 140 supporting V2X communication may be configured as follows.

[0059] Figure 2 is a conceptual diagram illustrating a first exemplary embodiment of a communication system.

[0060] like Figure 2 As shown, the communication system may include an access network, a core network, etc. The access network may include a base station 210, a relay station 220, user equipments (UEs) 231 to 236, etc. UEs 231 to 236 may include a Figure 1 The communication nodes in the vehicle 100 and the vehicle 110 are located Figure 1 The communication nodes in the infrastructure 120 are Figure 1 When the 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, and the like.

[0061] When the communication system supports 5G communication technology, the core network may include a user plane function (UPF) 250, a session management function (SMF) 260, an access and mobility management function (AMF) 270, etc. Alternatively, when the communication system operates in a non-standalone (NSA) mode, the core network composed of the S-GW 250, the P-GW 260, and the MME 270 may support 5G communication technology as well as 4G communication technology, and the core network composed of the UPF 250, the SMF 260, and the AMF 270 may support 4G communication technology as well as 5G communication technology.

[0062] In addition, when the communication system supports network slicing technology, the core network can be divided into multiple logical network slices. For example, a network slice supporting V2X communication (e.g., V2V network slice, V2I network slice, V2P network slice, V2N network slice, etc.) can be configured, and V2X communication can be supported by the V2X network slice configured in the core network.

[0063] The communication nodes constituting the communication system (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) technology, time division multiple access (TDMA) technology, frequency division multiple access (FDMA) technology, orthogonal frequency division multiplexing (OFDM) technology, filtered OFDM technology, orthogonal frequency division multiple access (OFDMA) technology, single carrier FDMA (SC-FDMA) technology, non-orthogonal multiple access (NOMA) technology, generalized frequency division multiplexing (GFDM) technology, filter bank multi-carrier (FBMC) technology, universal filtered multi-carrier (UFMC) technology, and space division multiple access (SDMA) technology. access, SDMA) technology.

[0064] The communication nodes constituting the communication system (e.g., base stations, relay stations, UE, S-GW, P-GW, MME, UPF, SMF, AMF, etc.) may be configured as follows.

[0065] Figure 3 is a conceptual diagram showing a first exemplary embodiment of a communication node constituting a communication system.

[0066] 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 for performing communication. In addition, 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 communicate with each other when connected through a bus 370.

[0067] However, each component included in the communication node 300 may 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 may be connected to at least one of the memory 320, the transceiver 330, the input interface device 340, the output interface device 350, and the storage device 360 ​​via a dedicated interface.

[0068] The processor 310 may execute at least one program instruction stored in at least one of the memory 320 and the storage device 360. The processor 310 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the method according to the exemplary embodiment of the present invention is executed. Each of the memory 320 and the storage device 360 ​​may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 320 may include at least one of a read-only memory (ROM) and a random access memory (RAM).

[0069] Reference again Figure 2 In the communication system, the base station 210 may form a macro cell or a small cell and may be connected to the core network via an ideal backhaul or a non-ideal backhaul. The base station 210 may send a signal received from the core network to UE 231 to UE 236 and the relay station 220, and may send a signal received from UE 231 to UE 236 and the relay station 220 to the core network. UE#1 231, UE#2 232, UE#4 234, UE#5 235, and UE#6 236 may belong to the cell coverage of the base station 210. UE#1 231, UE#2 232, UE#4 234, UE#5 235, and UE#6 236 may be connected to the base station 210 by performing a connection establishment process with the base station 210. UE#1 231 , UE#2 232 , UE#4 234 , UE#5 235 , and UE#6 236 may communicate with the base station 210 after being connected to the base station 210 .

[0070] The relay station 220 may be connected to the base station 210, and may relay communication between the base station 210 and UE#3 233 and UE#4 234. That is, the relay station 220 may transmit a signal received from the base station 210 to the UE#3 233 and UE#4 234, and may transmit a signal received from the UE#3 233 and UE#4 234 to the base station 210. The UE#4 234 may belong to both the cell coverage of the base station 210 and the cell coverage of the relay station 220, and the UE#3 233 may belong to the cell coverage of the relay station 220. That is, the UE#3 233 may be located outside the cell coverage of the base station 210. The UE#3 233 and UE#4 234 may be connected to the relay station 220 by performing a connection establishment procedure with the relay station 220. The UE#3 233 and UE#4 234 may communicate with the relay station 220 after being connected to the relay station 220.

[0071] The base station 210 and the relay station 220 may support multiple-input multiple-output (MIMO) technology (e.g., single-user (SU)-MIMO, multi-user (MU)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) communication technology, carrier aggregation (CA) communication technology, unlicensed band communication technology (e.g., Licensed Assisted Access (LAA), enhanced LAA (eLAA), etc.), side link communication technology (e.g., ProSe communication technology, D2D communication technology), etc. UE#1 231, UE#2 232, UE#5 235, and UE#6 236 may perform operations corresponding to the base station 210 and operations supported by the base station 210. UE#3 233 and UE#4 234 may perform operations corresponding to the relay station 220 and operations supported by the relay station 220.

[0072] Here, the base station 210 may refer to a Node B (NB), an evolved Node B (eNB), a base transceiver station (BTS), a radio remote head (RRH), a transmit receive point (TRP), a radio unit (RU), a road side unit (RSU), a radio transceiver, an access point, an access node, etc. The relay station 220 may refer to a small base station, a relay node, etc. Each of the UEs 231 to 236 may refer to a terminal, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, an on-board unit (OBU), etc.

[0073] On the other hand, a communication node that performs communication in a communication network may be configured as follows. Figure 4 The communication nodes shown may be Figure 3 A specific exemplary embodiment of a communication node is shown.

[0074] Figure 4 is a block diagram illustrating a first exemplary embodiment of a communication node performing communications.

[0075] like Figure 4 As shown, each of the first communication node 400a and the second communication node 400b can be a base station or a UE. The first communication node 400a can send a signal to the second communication node 400b. The transmission processor 411 included in the first communication node 400a can receive data (e.g., data unit) from the data source 410. The transmission processor 411 can receive control information from the controller 416. The control information may include at least one of system information, RRC configuration information (e.g., information configured by RRC signaling), MAC control information (e.g., MAC CE) or PHY control information (e.g., DCI, SCI).

[0076] The transmit processor 411 may generate data symbols by performing processing operations on data (e.g., encoding operations, symbol mapping operations, etc.). The transmit processor 411 may generate control symbols by performing processing operations on control information (e.g., encoding operations, symbol mapping operations, etc.). In addition, the transmit processor 411 may generate synchronization / reference symbols for synchronization signals and / or reference signals.

[0077] The Tx MIMO processor 412 may perform spatial processing operations (e.g., precoding operations) on data symbols, control symbols, and / or synchronization / reference symbols. The output (e.g., symbol stream) of the Tx MIMO processor 412 may be provided to a modulator (MOD) included in the transceiver 413a to the transceiver 413t. The modulator may generate modulation symbols by performing processing operations on the symbol stream, and may generate signals by performing additional processing operations (e.g., analog conversion operations, amplification operations, filtering operations, up-conversion operations, etc.) on the modulation symbols. The signals generated by the modulators of the transceivers 413a to the transceivers 413t may be transmitted through the antennas 414a to the antennas 414t.

[0078] The signal transmitted by the first communication node 400a may be received at the antenna 464a to the antenna 464r of the second communication node 400b. The signal received at the antenna 464a to the antenna 464r may be provided to a demodulator (DEMOD) included in the transceiver 463a to the transceiver 463r. The demodulator (DEMOD) may obtain samples by performing processing operations (e.g., filtering operations, amplification operations, down-conversion operations, digital conversion operations, etc.) on the signal. The demodulator may perform additional processing operations on the samples to obtain symbols. The MIMO detector 462 may perform MIMO detection operations on the symbols. The receiving processor 461 may perform processing operations (e.g., deinterleaving operations, decoding operations, etc.) on the symbols. The output of the receiving processor 461 may be provided to the data sink. 460 and controller 466. For example, data may be provided to data sink 460, and control information may be provided to controller 466.

[0079] On the other hand, the second communication node 400b can send a signal to the first communication node 400a. The transmission processor 469 included in the second communication node 400b can receive data (e.g., data unit) from the data source 467, and perform processing operations on the data to generate data symbols. The transmission processor 468 can receive control information from the controller 466, and perform processing operations on the control information to generate control symbols. In addition, the transmission processor 468 can generate reference symbols by performing processing operations on reference signals.

[0080] The Tx MIMO processor 469 may perform spatial processing operations (e.g., precoding operations) on data symbols, control symbols, and / or reference symbols. The output (e.g., symbol stream) of the Tx MIMO processor 469 may be provided to a modulator (MOD) included in the transceiver 463a to the transceiver 463t. The modulator may generate modulation symbols by performing processing operations on the symbol stream, and may generate signals by performing additional processing operations (e.g., analog conversion operations, amplification operations, filtering operations, up-conversion operations) on the modulation symbols. The signals generated by the modulators of the transceivers 463a to the transceivers 463t may be transmitted via the antennas 464a to the antennas 464t.

[0081] The signal transmitted by the second communication node 400b can be received at the antenna 414a to the antenna 414r of the first communication node 400a. The signal received at the antenna 414a to the antenna 414r can be provided to the demodulator (DEMOD) included in the transceiver 413a to the transceiver 413r. The demodulator can obtain samples by performing processing operations (e.g., filtering operations, amplification operations, down-conversion operations, digital conversion operations) on the signal. The demodulator can perform additional processing operations on the samples to obtain symbols. The MIMO detector 420 can perform MIMO detection operations on the symbols. The receiving processor 419 can perform processing operations (e.g., deinterleaving operations, decoding operations, etc.) on the symbols. The output of the receiving processor 419 can be provided to the data sink 418 and the controller 416. For example, data can be provided to the data sink 418, and control information can be provided to the controller 416.

[0082] Memory 415 and storage 465 may store data, control information and / or program codes. Scheduler 417 may perform scheduling operations for communications. Figure 4 The processors 411, 412, 419, 461, 468, 469 and the controllers 416 and 466 shown may be Figure 3 The processor 310 shown may be used to execute the methods described in the present invention.

[0083] Figure 5a is a block diagram illustrating a first exemplary embodiment of a transmit path, Figure 5b is a block diagram illustrating a first exemplary implementation of a receive path.

[0084] like Figure 5a and Figure 5bAs shown, the transmission path 510 can be implemented in a communication node that transmits a signal, and the reception path 520 can be implemented in a communication node that receives a signal. The transmission path 510 may include a channel coding and modulation block 511, a serial-to-parallel (S to P) block 512, an N-point inverse fast Fourier transform (N-point IFFT) block 513, a parallel-to-serial (P to S) block 514, a cyclic prefix (CP) adding block 515, and an up-converter (UC) 516. The reception path 520 may include a down-converter (DC) 521, a CP deletion block 522, an S to P block 523, an N-point FFT block 524, a P to S block 525, and a channel decoding and demodulation block 526. Here, N may be a natural number.

[0085] In the transmission path 510, the information bits may be input to the channel coding and modulation block 511. The channel coding and modulation block 511 may perform coding and decoding operations (e.g., low-density parity check (LDPC) coding and decoding operations, polar coding and decoding operations, etc.) and modulation operations (e.g., quadrature phase shift keying (OPSK), quadrature amplitude modulation (QAM), etc.) on the information bits. The output of the channel coding and modulation block 511 may be a modulation symbol sequence.

[0086] The S to P block 512 may convert the frequency domain modulation symbols into parallel symbol streams to generate N parallel symbol streams. N may be an IFFT size or an FFT size. The N-point IFFT block 513 may generate a time domain signal by performing an IFFT operation on the N parallel symbol streams. The P to S block 514 may convert the output (e.g., parallel signals) of the N-point IFFT block 513 into a serial signal to generate a serial signal.

[0087] The CP adding block 515 may insert a CP into the signal. The UC 516 may up-convert the frequency of the output of the CP adding block 515 to a radio frequency (RF) frequency. In addition, the output of the CP adding block 515 may be filtered in baseband before up-conversion.

[0088] The signal transmitted from the transmission path 510 may be input to the reception path 520. The operation in the reception path 520 may be the reverse operation of the operation in the transmission path 510. The DC 521 may down-convert the frequency of the received signal to the baseband frequency. The CP removal block 522 may remove the CP from the signal. The output of the CP removal block 522 may be a serial signal. The S to P block 523 may convert the serial signal into a parallel signal. The N-point FFT block 524 may generate N parallel signals by performing an FFT algorithm. The P to S block 525 may convert the parallel signal into a modulation symbol sequence. The channel decoding and demodulation block 526 may perform a demodulation operation on the modulation symbol, and may recover the data by performing a decoding operation on the result of the demodulation operation.

[0089] exist Figure 5a and Figure 5b In the present invention, discrete Fourier transform (DFT) and inverse DFT (IDFT) can be used to replace FFT and IFFT. Figure 5a and Figure 5b Each of the blocks (eg, components) in the embodiment may be implemented by at least one of hardware, software, or firmware. Figure 5a and Figure 5b Some blocks in the can be implemented by software, and other blocks can be implemented by hardware or a combination of hardware and software. Figure 5a and Figure 5b In the , a block can be subdivided into multiple blocks, multiple blocks can be integrated into one block, some blocks can be omitted, and blocks that support other functions can be added.

[0090] On the other hand, the communication between UE#5 235 and UE#6 236 may be performed based on a sidelink communication technology (e.g., ProSe communication technology, D2D communication technology). The sidelink communication may be performed based on a one-to-one scheme or a one-to-many scheme. When V2V communication is performed using the sidelink communication technology, UE#5 235 may refer to a UE located at Figure 1 The communication node in the first vehicle 100, and UE#6 236 may refer to a communication node located at Figure 1 When V2I communication is performed using the sidelink communication technology, UE#5 235 may refer to a communication node located in the second vehicle 110. Figure 1 The communication node in the first vehicle 100, and UE#6236 may refer to a communication node located at Figure 1 When V2P communication is performed using the sidelink communication technology, UE#5 235 may refer to a communication node located in Figure 1The communication node in the first vehicle 100, and UE#6 236 may refer to a communication node carried by the person 130.

[0091] The scenarios in which the side link communication is applied can be classified according to the locations of the UEs (e.g., UE#5 235 and UE#6 236) participating in the side link communication, as shown in Table 1 below. For example, Figure 2 The scenario of sidelink communication between UE#5 235 and UE#6 236 shown may be sidelink communication scenario #C.

[0092] [Table 1]

[0093] Sidelink communication scenario UE#5 235 location UE#6 236 location #A Outside the coverage of base station 210 Outside the coverage of base station 210 #B Within the coverage area of ​​base station 210 Outside the coverage 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 In the coverage area of ​​other base stations

[0094] On the other hand, the user plane protocol stack of the UEs (eg, UE#5 235 and UE#6 236) performing sidelink communication may be configured as follows.

[0095] Figure 6 is a block diagram illustrating a first exemplary implementation of a user plane protocol stack of a UE performing sidelink communications.

[0096] like Figure 6 As shown, UE#5 235 may be Figure 2 UE#5 235 is shown, and UE#6 236 may be Figure 2 UE#6 236 is shown. The scenario of the sidelink communication 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 can include a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer.

[0097] A PC5 interface (e.g., PC5-U interface) may be used to perform sidelink communication between UE#5 235 and UE#6 236. A layer 2 identifier (ID) (e.g., source layer 2 ID, destination layer 2 ID) may be used for sidelink communication, and the layer 2 ID may be an ID configured for V2X communication. In addition, in the sidelink communication, a hybrid automatic repeat request (HARQ) feedback operation may be supported, and an RLC acknowledged mode (AM) or an RLC unacknowledged mode (UM) may be supported.

[0098] On the other hand, the control plane protocol stack of the UEs (eg, UE#5 235 and UE#6 236) performing sidelink communication may be configured as follows.

[0099] Figure 7 is a block diagram illustrating a first exemplary embodiment of a control plane protocol stack of a UE performing sidelink communications, Figure 8 is a block diagram illustrating a second exemplary embodiment of a control plane protocol stack of a UE performing sidelink communications.

[0100] like Figure 7 and Figure 8 As shown, UE#5 235 may be Figure 2 UE#5 235 is shown, and UE#6 236 may be Figure 2 UE#6 236 is shown. The scenario of the side link communication between UE#5 235 and UE#6 236 can be one of the side link communication scenarios #A to #D in Table 1. Figure 7 The control plane protocol stack shown may be a control plane protocol stack for sending and receiving broadcast information (eg, Physical Sidelink Broadcast Channel (PSBCH)).

[0101] Figure 7 The control plane protocol stack shown may include a PHY layer, a MAC layer, an RLC layer, and a radio resource control (RRC) layer. A sidelink communication between UE#5 235 and UE#6 236 may be performed using a PC5 interface (eg, PC5-C interface). Figure 8 The control plane protocol stack shown may be a control plane protocol stack for one-to-one sidelink communications. Figure 8 The control plane protocol stack shown may include a PHY layer, a MAC layer, an RLC layer, a PDCP layer, and a PC5 signaling protocol layer.

[0102] On the other hand, channels utilized in the sidelink communication between UE#5 235 and UE#6 236 may include a physical sidelink shared channel (PSSCH), a physical sidelink control channel (PSCCH), a physical sidelink discovery channel (PSDCH), and a physical sidelink broadcast channel (PSBCH). PSSCH may be used to transmit and receive sidelink data and may be configured in a UE (e.g., UE#5 235 or UE#6 236) through higher layer signaling. PSCCH may be used to transmit and receive sidelink control information (SCI) and may also be configured in a UE (e.g., UE#5 235 or UE#6 236) through higher layer signaling.

[0103] PSDCH can be used for discovery process. For example, discovery signal can be transmitted via PSDCH. PSBCH can be used to send and receive broadcast information (e.g., system information). In addition, demodulation reference signal (DM-RS), synchronization signal, etc. can be used in sidelink communication between UE#5 235 and UE#6 236. The synchronization signal can include primary sidelink synchronization signal (PSSS) and secondary sidelink synchronization signal (SSSS).

[0104] On the other hand, the side link transmission mode (TM) can be divided into side links TM#1 to TM#4, as shown in Table 2 below.

[0105] [Table 2]

[0106] SidelinkTM illustrate #1 Transmission using resources scheduled by the base station #2 UE automatic transmission without base station scheduling #3 Transmission using resources scheduled by a base station in V2X communications #4 UE automatic transmission without base station scheduling in V2X communication

[0107] When supporting sidelink TM#3 or TM#4, each of UE#5 235 and UE#6 236 may perform sidelink communication using a resource pool configured by base station 210. A resource pool may be configured for each of sidelink control information and sidelink data.

[0108] A resource pool for side link control information may be configured based on an RRC signaling process (e.g., a dedicated RRC signaling process, a broadcast RRC signaling process). A resource pool for receiving side link control information may be configured by a broadcast RRC signaling process. When side link TM#3 is supported, a resource pool for transmitting side link control information may be configured by a dedicated RRC signaling process. In this case, the side link control information may be transmitted via resources scheduled by the base station 210 within a resource pool configured by a dedicated RRC signaling process. When side link TM#4 is supported, a resource pool for transmitting side link control information may be configured by a dedicated RRC signaling process or a broadcast RRC signaling process. In this case, the side link control information may be transmitted via resources automatically selected by a UE (e.g., UE#5 235 or UE#6 236) within a resource pool configured by a dedicated RRC signaling process or a broadcast RRC signaling process.

[0109] When side link TM#3 is supported, a resource pool for sending and receiving side link data may not be configured. In this case, the side link data may be sent and received through resources scheduled by the base station 210. When side link TM#4 is supported, a resource pool for sending and receiving side link data may be configured through a dedicated RRC signaling process or a broadcast RRC signaling process. In this case, the side link data may be sent and received via resources automatically selected by a UE (e.g., UE#5 235 or UE#6 236) within a resource pool configured through a dedicated RRC signaling process or a broadcast RRC signaling process.

[0110] In the following, the side link communication method will be described. Even when describing a method performed at a first communication node in a communication node (e.g., sending or receiving a signal), the corresponding second communication node may also perform a method corresponding to the method performed at the first communication node (e.g., receiving or sending a signal). That is, when describing the operation of UE#1 (e.g., vehicle #1), the corresponding UE#2 (e.g., vehicle #2) may perform an operation corresponding to the operation of UE#1. Conversely, when describing the operation of UE#2, the corresponding UE#1 may perform an operation corresponding to the operation of UE#2. In the exemplary embodiment described below, the operation of the vehicle may be the operation of a communication node located in the vehicle.

[0111] The sidelink signal may be a synchronization signal and a reference signal for sidelink communication. For example, the synchronization signal may be a synchronization signal / physical broadcast channel (SS / PBCH) block, a sidelink synchronization signal (SLSS), a primary sidelink synchronization signal (PSSS), a secondary sidelink synchronization signal (SSSS), etc. The reference signal may be a channel state information-reference signal (CSI-RS), a DM-RS, a phase tracking-reference signal (PT-RS), a cell specific reference signal (CRS), a sounding reference signal (SRS), a discovery reference signal (DRS), etc.

[0112] The sidelink channel may be a PSSCH, a PSCCH, a PSDCH, a PSBCH, a physical sidelink feedback channel (PSFCH), etc. In addition, a sidelink channel may refer to a sidelink channel including a sidelink signal mapped to a specific resource in a corresponding sidelink channel. Sidelink communications may support broadcast services, multicast services, groupcast services, and unicast services.

[0113] The base station may send system information (e.g., SIB12, SIB13, SIB14) and an RRC message including configuration information for sidelink communication (i.e., sidelink configuration information) to the UE. The UE may receive the system information and the RRC message from the base station, identify the sidelink configuration information included in the system information and the RRC message, and perform sidelink communication based on the sidelink configuration message. SIB12 may include sidelink communication / discovery configuration information. SIB13 and SIB14 may include configuration information for V2X sidelink communication.

[0114] Sidelink communications may be performed within a SL bandwidth part (BWP). The base station may configure the SL BWP to the UE using higher layer signaling. The higher layer signaling may include SL-BWP-Config and / or SL-BWP-ConfigCommon. SL-BWP-Config may be used to configure the SL BWP for UE-specific sidelink communications. SL-BWP-ConfigCommon may be used to configure cell-specific configuration information.

[0115] In addition, the base station may configure a resource pool to the UE using higher layer signaling. The higher layer signaling may include SL-BWP-PoolConfig, SL-BWP-PoolConfigCommon, SL-BWP-DiscPoolConfig and / or SL-BWP-DiscPoolConfigCommon. SL-BWP-PoolConfig may be used to configure a sidelink communication resource pool. SL-BWP-PoolConfigCommon may be used to configure a cell-specific sidelink communication resource pool. SL-BWP-DiscPoolConfig may be used to configure a resource pool dedicated to UE-specific sidelink discovery. SL-BWP-DiscPoolConfigCommon may be used to configure a resource pool dedicated to cell-specific sidelink discovery. The UE may perform sidelink communication within a resource pool configured by the base station.

[0116] Sidelink communication may support SL discontinuous reception (DRX) operation. The base station may send a higher layer message (e.g., SL-DRX-Config) including parameters related to SL DRX to the UE. The UE may perform SL DRX operation based on the SL-DRX-Config received from the base station. Sidelink communication may support inter-UE coordination operation. The base station may send a higher layer message (e.g., SL-InterUE-CoordinationConfig) including inter-UE coordination parameters to the UE. The UE may perform inter-UE coordination operation based on the SL-InterUE-CoordinationConfig received from the base station.

[0117] The side link communication may be performed based on a single SCI scheme or a multi-SCI scheme. When a single SCI scheme is used, the side link communication may be performed based on one SCI (e.g., the first-stage SCI (1 st -stage SCI)) to perform data transmission (e.g., sidelink data transmission, sidelink shared channel (SL-SCH) transmission). When a multi-SCI scheme is used, two SCIs (e.g., first-stage SCI and second-stage SCI (2 nd-stage SCI)) to perform data transmission. SCI can be transmitted on PSCCH and / or PSSCH. When a single SCI scheme is utilized, SCI (e.g., first-stage SCI) can be transmitted on PSCCH. When a multi-SCI scheme is utilized, first-stage SCI can be transmitted on PSCCH, and second-stage SCI can be transmitted on PSCCH or PSSCH. The first-stage SCI can be referred to as "first-stage SCI (first-stage SCI)", and the second-stage SCI can be referred to as "second-stage SCI (second-stage SCI)". The format of the first-stage SCI may include SCI format 1-A, and the format of the second-stage SCI may include SCI format 2-A, SCI format 2-B, and SCI format 2-C.

[0118] SCI format 1-A can be used to schedule PSSCH and second-stage SCI. SCI format 1-A may include 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, modulation and coding scheme (MCS) information, additional MCS table indicator, PSFCH overhead indicator, or at least one of a conflict information receiver flag.

[0119] SCI format 2-A may be used for decoding of PSSCH. SCI format 2-A may include at least one of a HARQ processor number, a new data indicator (NDI), a redundancy version (RV), a source ID, a destination ID, a HARQ feedback enable / disable indicator, a cast type indicator, or a CSI request.

[0120] SCI format 2-B may be used for decoding of PSSCH. SCI format 2-B may include at least one of the number of HARQ processors, NDI, RV, source ID, destination ID, HARQ feedback enable / disable indicator, zone ID, or communication range requirement.

[0121] SCI format 2-C may be used for decoding of PSSCH. In addition, SCI format 2-C may be used to provide or request inter-UE coordination information. SCI format 2-C may include at least one of the number of HARQ processors, NDI, RV, source ID, destination ID, HARQ feedback enable / disable indicator, CSI request, or provide / request indicator.

[0122] When the value of the provide / request indicator is set to 0, this may indicate that SCI format 2-C is used to provide inter-UE coordination information. In this case, SCI format 2-C may include at least one of a resource combination, a first resource position, a reference time slot position, a resource set type, or a lowest subchannel index.

[0123] When the value of the offer / request indicator is set to 1, this may indicate that the SCI format 2-C is used to request inter-UE coordination information. In this case, the SCI format 2-C may include at least one of a priority, a number of subchannels, a resource reservation period, a resource selection window position, a resource set type, or a padding bit.

[0124] On the other hand, side link communication may be performed in a licensed band and / or an unlicensed band. Side link communication performed in an unlicensed band may be referred to as side link-unlicensed band (SL-U) communication or unlicensed band-side link (U-SL) communication. In SL-U communication, the first terminal may communicate with the second terminal according to mode 1 or mode 2. When mode 1 is used, the first terminal may communicate with the second terminal based on scheduling by the base station. When mode 2 is used, the first terminal may communicate with the second terminal without scheduling by the base station. Mode 1 may correspond to side link TM#1 or TM#3 disclosed in Table 2 above. Mode 2 may correspond to side link TM#2 or TM#4 disclosed in Table 2 above.

[0125] Fig. 9 is a timing diagram illustrating a first exemplary embodiment of a communication method in an unlicensed band.

[0126] like Fig. 9As shown, the base station may perform a listen-before-talk (LBT) operation to perform a downlink (DL) transmission, and if the result of the LBT operation indicates an idle state (e.g., a clean state) of the channel, the base station may perform a DL transmission. The terminal may perform an LBT operation to perform an uplink (UL) transmission, and if the result of the LBT operation indicates an idle state of the channel, the terminal may perform an UL transmission. If the result of the LBT operation indicates a busy state of the channel, DL transmission and / or UL transmission may not be performed. DL transmission and / or UL transmission may be performed within a channel occupancy time (COT). COT may be initiated by a base station or a terminal. The LBT operation may be performed based on one of the categories disclosed in Table 3 below.

[0127] [Table 3]

[0128]

[0129] The LBT operation may be referred to as a clear channel assessment (CCA) operation. The CCA operation may be performed during the CCA period. When performing the CCA operation, a communication node (e.g., a base station and / or a terminal) may identify a channel state based on an energy detection (ED) scheme. In other words, the communication node may determine whether there is another signal in the channel. If the energy detected during the CCA period is less than a threshold value (e.g., an ED threshold value), the communication node may determine the channel state to be an idle state. In other words, the communication node may determine that there are no other signals in the channel. If the channel state is determined to be an idle state, the communication node may access a channel within the COT. If the energy detected during the CCA period is equal to or greater than a threshold value, the communication node may determine the channel state to be a busy state. In other words, the communication node may determine that there is another signal in the channel. If the channel state is a busy state, the communication node will not access a channel within the COT.

[0130] In an unlicensed band, a communication node may perform an LBT operation and transmit data when the result of the LBT operation indicates an idle state of the channel. In this case, the base station may transmit a DL transmission burst within the COT, and the terminal may transmit a UL transmission burst within the COT. The COT may be configured within the maximum COT (maximum COT, MCOT). The time slot duration of the CCA may be 5μs to 9μs. The duration of the MCOT may be 8ms. The base station may initiate and / or configure the COT based on a higher layer parameter SemiStaticChannelAccessConfig. SemiStaticChannelAccessConfig may include information about the period of the COT. The terminal may identify the COT initiated by the base station based on the SemiStaticChannelAccessConfig.

[0131] The terminal may initiate and / or configure COT based on a higher layer parameter SemiStaticChannelAccessConfigUE. SemiStaticChannelAccessConfigUE may include information about a period and offset of COT. The terminal may identify COT initiated by the terminal based on SemiStaticChannelAccessConfigUE.

[0132] The terminal can initiate and / or configure COT based on SemiStaticChannelAccessConfigUE in the unlicensed band. As another method, the base station can signal the terminal SemiStaticChannelAccessConfigSL-U of the COT used for SL-U communication. The COT used for SL-U communication may be referred to as a side link (SL)-COT. SemiStaticChannelAccessConfigSL-U may include information about the period and offset of the SL-COT. The terminal can configure the SL-COT based on SemiStaticChannelAccessConfig-U. Another terminal can identify the COT initiated based on SemiStaticChannelAccessConfigSL-U.

[0133] In the unlicensed band, the terminal may perform an LBT operation before SL communication (e.g., transmission of SL data) in order to perform SL communication. If the LBT operation is successful, a COT may be initiated in the unlicensed band, and SL communication may be performed within the COT. "LBT operation success" may mean that the result of the LBT operation indicates an idle state.

[0134] In an unlicensed band, a channel access process may be classified into a DL channel access process and a UL channel access process. The DL channel access process may be classified into a type 1 DL channel access process and a type 2 DL channel access process. A type 1 DL channel access process may be performed for initiation of a COT. A type 2 DL channel access process may be performed for transmission within a COT (e.g., a shared COT). The channel access process may refer to an LBT operation. A type 1 DL channel access process may be performed for at least one of a physical downlink shared channel (PDSCH) transmission initiated by an eNB, a physical downlink control channel (PDCCH) transmission, or an enhanced PDCCH (EPDCCH) transmission, and / or any transmission initiated by a gNB. An eNB may refer to a base station in a 4G communication system, and a gNB may refer to a base station in a 5G communication system.

[0135] A type 2 DL channel access procedure may be performed on at least one of a discovery burst transmission initiated by an eNB or a transmission not including a PDSCH and / or a discovery burst transmission or a discovery transmission multiplexed with non-unicast information initiated by a gNB. The type 2 DL channel access procedure may be classified into a type 2A DL channel access procedure, a type 2B DL ​​channel access procedure, and a type 2C DL channel access procedure. The length of the sensing period (e.g., sensing interval) in the type 2A DL channel access procedure, the type 2B DL ​​channel access procedure, and the type 2C DL channel access procedure may be different. The length of the sensing period in the type 2A DL channel access procedure may be 25 μs. The length of the sensing period in the type 2B DL ​​channel access procedure may be 16 μs. No sensing operation may be performed in the type 2C DL channel access procedure.

[0136] The UL channel access procedure may be classified into a type 1 UL channel access procedure and a type 2 UL channel access procedure. A type 1 UL channel access procedure may be performed for initiation of a COT. A type 2 UL channel access procedure may be performed for transmissions within a COT (e.g., a shared COT). A type 1 UL channel access procedure may be performed for at least one of a physical uplink shared channel (PUSCH) transmission or a sounding reference signal (SRS) transmission scheduled or configured by an eNB, at least one of a PUSCH transmission or an SRS transmission scheduled or configured by a gNB, a PUCCH transmission scheduled or configured by a gNB, and / or a transmission associated with a random access (RA) procedure.

[0137] The type 2 UL channel access procedure may be classified into a type 2A UL channel access procedure, a type 2B UL channel access procedure, and a type 2C UL channel access procedure. The lengths of the sensing periods for the type 2A UL channel access procedure and the type 2B UL channel access procedure may be different. The length of the sensing period in the type 2A UL channel access procedure may be 25 μs. The length of the sensing period in the type 2B UL channel access procedure may be 16 μs. The sensing operation may not be performed in the type 2C UL channel access procedure.

[0138] Type 1 DL channel access procedure, type 2 DL channel access procedure, type 1 UL channel access procedure and / or type 2 UL channel access procedure can be used for SL-U communication. In this case, in the description of type 1 DL channel access procedure, type 2 DL channel access procedure, type 1 UL channel access procedure and / or type 2 UL channel access procedure, the downlink channel and / or the uplink channel can be interpreted as a side link channel. The LBT operation can be interpreted as a type 1 DL channel access procedure, a type 2 DL channel access procedure, a new DL channel access procedure, a type 1 UL channel access procedure, a type 2 UL channel access procedure and / or a new UL channel access procedure.

[0139] In SL-U communication, the terminal may perform an LBT operation (e.g., a CCA operation) during a sensing duration (e.g., a contention window (CW)). The CW size may be determined based on a channel access priority class (CAPC). The CW size according to the CAPC may be determined based on Table 4 below. Table 4 may be applied to DL communication and / or SL communication (e.g., SL-U communication). Table 4 may be defined as a CAPC-CW table. In other words, a table defining a mapping relationship between a CAPC and a CW size may be referred to as a CAPC-CW table.

[0140] [Table 4]

[0141]

[0142] Here, CW min,p represents the minimum CW size for CAPC(p), and CW max,p Represents the maximum CW size used for CAPC(p). mcot,p Represents the maximum COT for CAPC(p). In UL communication and / or SL communication (eg, SL-U communication), a CW size according to CAPC may be defined based on the following Table 5. Table 5 may also be defined as a CAPC-CW table.

[0143] [Table 5]

[0144]

[0145] The terminal may determine the allowed CW sizes defined in Table 4 and / or Table 5 (eg, allowed CW p The CW size within the unlicensed band can be adjusted based on the reception of the ACK. The reception of the ACK can indicate good channel conditions, thereby allowing the terminal to select a smaller CW size. In other words, the terminal can reduce the CW size. When a smaller CW size is used, the opportunity to transmit data (e.g., SL data) can be increased. In the unlicensed band, the data transmission opportunity can be increased by CW size adjustment, and accordingly, the system throughput can be improved.

[0146] In SL-U communication, the LBT operation may be a type 1 channel access process, a type 2 channel access process, and / or a type 3 channel access process (e.g., a new type of channel access process). In SL-U communication, a type 1 channel access process may be referred to as a type 1 SL channel access process, a type 2 channel access process may be referred to as a type 2 SL channel access process, and a type 3 channel access process may be referred to as a type 3 SL channel access process. A type 1 channel access process (e.g., a type 1 SL channel access process) may be the same or similar to a type 1 DL channel access process and / or a type 1 UL channel access process. A type 2 channel access process (e.g., a type 2 SL channel access process) may be the same or similar to a type 2 DL channel access process and / or a type 2 UL channel access process. A type 2 SL channel access process may be classified into a type 2 ASL channel access process, a type 2 BSL channel access process, and a type 2 C SL channel access process.

[0147] The criteria for CAPC may vary depending on the mode of SL communication (e.g., Mode 1 or Mode 2). CAPC used in SL communication may be defined as SL CAPC, CAPC used in DL communication may be defined as DL CAPC, and CAPC used in UL communication may be defined as UL CAPC. In Mode 1, all or part of the DL CAPC may be used as the SL CAPC. In Mode 2, all or part of the UL CAPC may be used as the SL CAPC. Alternatively, depending on specific conditions, all or part of the DL CAPC may be used as the SL CAPC, and under certain conditions, all or part of the UL CAPC may also be used as the SL CAPC.

[0148] In SL-U communication, the terminal can perform LBT operations (e.g., channel access process) to transmit data. LBT operations can be performed within a CW, and a process of adjusting the CW size may be required to enhance system performance. In SL-U communication, the terminal can adjust the CW size based on whether an ACK is received. However, in SL-U communication, there may be situations where an ACK is not sent or received. For example, if the HARQ feedback operation is disabled, the receiving terminal may not send HARQ feedback (e.g., ACK or NACK) to the transmitting terminal for the data of the transmitting terminal. In multicast option 1 using a NACK-only scheme, when data reception fails, the receiving terminal may send a NACK to the transmitting terminal, but when data reception is successful, an ACK may not be sent to the transmitting terminal. In SL-U communication, when HARQ feedback (e.g., ACK) is not sent, the following methods may be considered to adjust the CW size:

[0149] In SL-U communication, when HARQ feedback is not sent, the CW size adjustment process (e.g., configuration process) may not be performed. In this case, the terminal (e.g., the transmitting terminal) may use the CW size based on the CAPC without adjustment. The terminal may use the CW size based on the minimum CAPC or the maximum CAPC that can be used for multicast communication.

[0150] In SL-U communication, when HARQ feedback is not sent, the CW size can be adjusted (e.g., configured) based on information other than ACK (e.g., other parameters). For example, in SL-U communication, the CW size can be adjusted based on the location of the terminal (e.g., the distance between the transmitting terminal and the receiving terminal).

[0151] [Table 6]

[0152]

[0153] The CAPC-CW table defined in Table 6 can be configured or indicated to the terminal through signaling (e.g., SI signaling, RRC signaling, MAC signaling, and / or PHY signaling). In the CAPC-CW table, the distance d can represent the distance between the transmitting terminal and the receiving terminal. The distance d between the transmitting terminal and the receiving terminal can be estimated based on various methods. If the distance d is less than or equal to A, the transmitting terminal can use the CW size corresponding to CAPC=1. If the distance d is greater than A and less than or equal to B, the transmitting terminal can use the CW size corresponding to CAPC=2. A can be less than B. If the distance d is greater than B and less than or equal to C, the transmitting terminal can use the CW size corresponding to CAPC=3. B can be less than C. If the distance d is greater than C and less than or equal to D, the transmitting terminal can use the CW size corresponding to CAPC=4. C can be less than D.

[0154] The transmitting terminal may measure a reference signal received power (RSRP) based on a signal (e.g., a reference signal) received from the receiving terminal, estimate a distance d between the transmitting terminal and the receiving terminal based on the measured RSRP, and select a CW size corresponding to the CAPC mapped to the estimated distance d from the CAPC-CW table. The transmitting terminal may perform an LBT operation within a CW having the selected CW size, and after a successful LBT operation, perform SL transmission to the receiving terminal. In order to estimate the distance d between the transmitting terminal and the receiving terminal, parameters other than RSRP (e.g., received signal strength indicator (RSRI), reference signal received quality (RSRQ), signal-to-interference-plus-noise ratio (SINR)) may also be used.

[0155] As another method, the CW size may be configured on a per-region basis. Terminals in the same region may use the same CW size. To support this operation, a region-specific CW size (eg, an allowed CW size) may be configured or indicated to the terminal via signaling.

[0156] In SL-U communication, there may be multiple CAPC-CW tables. In other words, multiple CAPC-CW tables may be configured or indicated to the terminal through signaling. For example, multiple CAPC-CW tables may be configured or indicated to the terminal through higher layer signaling, and the CAPC-CW tables used by the terminals in the multiple CAPC-CW tables may be indicated to the terminal through MAC signaling and / or PHY signaling. Multiple CAPC-CW tables may include a CAPC-CW table for unicast communication, a CAPC-CW table for multicast communication, and a CAPC-CW table for broadcast communication. In unicast communication, the sending terminal may use the CAPC-CW table for unicast communication. In multicast communication, the sending terminal may use the CAPC-CW table for multicast communication. In broadcast communication, the sending terminal may use the CAPC-CW table for broadcast communication.

[0157] A CAPC-CW table based on a distance d between terminals may be configured. In this case, the transmitting terminal may estimate the distance d between the transmitting terminal and the receiving terminal, identify a CAPC-CW table mapped to the estimated distance d in the CAPC-CW table, determine a CW size corresponding to a CAPC of the transmitting terminal (e.g., for SL transmission of the transmitting terminal) within the identified CAPC-CW table, and perform an LBT operation based on a CW having the determined CW size. The distance between the transmitting terminal and the receiving terminal may be determined based on an information element (e.g., an area ID) included in the SCI.

[0158] A CAPC-CW table based on RSRP may also be configured. In this case, the transmitting terminal may estimate RSRP based on a signal (e.g., a reference signal) received from the receiving terminal, identify a CAPC-CW table mapped to the estimated RSRP in the CAPC-CW table, determine a CW size corresponding to the CAPC of the transmitting terminal (e.g., for SL transmission of the transmitting terminal) within the identified CAPC-CW table, and perform LBT operation based on the CW with the determined CW size. Instead of RSRP, other parameters (e.g., RSSI, RSRQ, SINR) may also be used.

[0159] A CAPC-CW table based on a region may be configured. In this case, the transmitting terminal may determine the region where the transmitting terminal and / or the receiving terminal is located, identify the CAPC-CW table mapped to the identified region in the CAPC-CW table, determine the CW size corresponding to the CAPC of the transmitting terminal (e.g., for SL transmission of the transmitting terminal) in the identified CAPC-CW table, and perform an LBT operation based on the CW with the determined CW size. The region where the transmitting terminal and / or the receiving terminal is located may be determined based on an information element (e.g., region ID) included in the SCI.

[0160] In SL-U communication, the CAPC may be determined based on the priority information. The priority information may be included in the SCI, and the size of the priority information may be 3 bits. The terminal may identify the CAPC corresponding to the priority based on Table 7 below, determine the CW size corresponding to the identified CAPC from the CAPC-CW table, and perform the LBT operation based on the CW with the determined CW size.

[0161] [Table 7]

[0162] Priority CAPC 000 or 001 1 010 or 011 1 or 2 100 or 101 1, 2, or 3 110 or 111 1, 2, 3 or 4

[0163] A priority-based CAPC-CW table may be configured. For example, multiple CAPC-CW tables may be configured or indicated to the terminal through higher layer signaling, and a CAPC-CW table used by the terminal in the multiple CAPC-CW tables may be indicated to the terminal through MAC signaling and / or PHY signaling.

[0164] In SL-U communication, the terminal may determine (e.g., adjust) the CW size based on whether HARQ feedback (e.g., NACK) is received. For example, if N or more NACKs are received for multicast transmission in SL-U communication, if the ratio of the number of received NACKs to the predicted number of HARQ feedbacks for multicast transmission in SL-U communication is equal to or greater than a threshold, or if the ratio of the number of received NACKs to the number of terminals (e.g., receiving terminals) participating in multicast transmission in SL-U communication is equal to or greater than a threshold, the transmitting terminal may increase the CW size, perform an LBT operation based on the CW with the increased CW size, and send data if the LBT operation is successful. The CW size may be adjusted within the range of a minimum CW size and a maximum CW size.

[0165] In SL-U communication, the terminal can adjust the CW size based on the channel busy ratio (CBR) (or channel occupancy ratio (CR)). A high CBR (or CR) can indicate that there are many terminals around the transmitting terminal. Therefore, when the CBR (or CR) is high, the CW size can be increased. A low CBR (or CR) can indicate that there are fewer terminals around the transmitting terminal. Therefore, when the CBR (or CR) is low, the CW size can be reduced.

[0166] The transmitting terminal may measure the CBR (or CR) and compare the measured CBR (or CR) with a threshold. If the measured CBR (or CR) is equal to or greater than the threshold, the transmitting terminal may increase the CW size. If the measured CBR (or CR) is less than the threshold, the transmitting terminal may reduce the CW size. The transmitting terminal may perform an LBT operation based on the CW with the adjusted CW size, and if the LBT operation is successful, send data to the receiving terminal.

[0167] In SL-U communication, CAPC may be determined based on CBR (or CR). Priority information may be included in SCI, and the size of the priority information may be 3 bits. The terminal may identify the CAPC corresponding to the CBR (or CR) based on Table 8 below, determine the CW size corresponding to the identified CAPC from the CAPC-CW table, and perform LBT operation based on the CW with the determined CW size.

[0168] [Table 8]

[0169] CBR (or CR) CAPC CBR (or CR) ≤ A 1 A < CBR (or CR) ≤ B 1 or 2 B < CBR (or CR) ≤ C 1, 2, or 3 C < CBR (or CR) ≤ D 1, 2, 3 or 4

[0170] If the CBR (or CR) is less than or equal to A, the transmitting terminal may use a CW size corresponding to CAPC=1. If the CBR (or CR) is greater than A and less than or equal to B, the transmitting terminal may use a CW size corresponding to CAPC=1 or 2. A may be less than B. If the CBR (or CR) is greater than B and less than or equal to C, the transmitting terminal may use a CW size corresponding to CAPC=1, 2, or 3. B may be less than C. If the CBR (or CR) is greater than C and less than or equal to D, the transmitting terminal may use a CW size corresponding to CAPC=1, 2, 3, or 4. C may be less than D.

[0171] A CAPC-CW table based on CBR (or CR) may be configured. For example, a plurality of CAPC-CW tables may be configured or indicated to the terminal through higher layer signaling, and a CAPC-CW table used by the terminal in a plurality of CAPC-CW tables may be indicated to the terminal through MAC signaling and / or PHY signaling. The terminal may determine a CW size based on an indicated CAPC-CW table in a plurality of CAPC-CW tables, and perform an LBT operation based on a CW having the determined CW size.

[0172] Configuration information for the CW size (e.g., an indicator for enabling / disabling HARQ feedback for the CW size configuration (e.g., a 1-bit indicator) and / or an indicator indicating whether the CW size configuration is applied (e.g., a 1-bit indicator)) may be included in the SCI. A new SCI format may be configured for SL-U communication. Alternatively, the configuration information for the CW size may be transmitted via higher layer signaling (e.g., RRC signaling and / or MAC signaling). Some or all of the above exemplary embodiments may be performed based on the configuration information for the CW size.

[0173] Alternatively, the CW size may be adjusted based on the ratio of resources reserved by other terminals to resources within the resource sensing window. For example, the transmitting terminal may perform an LBT operation based on a CW having a minimum CW size corresponding to a CAPC of the transmitting terminal (e.g., for SL transmission of the transmitting terminal), and if the LBT operation is successful, data is sent to the receiving terminal. The transmitting terminal may then perform a resource sensing operation within the resource sensing window for SL transmission to the receiving terminal. Through the resource sensing operation, the transmitting terminal may identify candidate resources that may be used for SL transmission and resources reserved by other terminals.

[0174] The transmitting terminal may adjust the CW size based on the following equation 1. If the ratio of the reserved resources within the resource sensing window to all resources is equal to or greater than the threshold, the transmitting terminal may increase the CW size. On the other hand, if the ratio of the reserved resources within the resource sensing window to all resources is less than the threshold, the transmitting terminal may maintain or reduce the CW size.

[0175] [Equation 1]

[0176]

[0177] Alternatively, the transmitting terminal may adjust the CW size based on the following equation 2. If the ratio of the candidate resources within the resource sensing window to all resources is less than a threshold, the transmitting terminal may increase the CW size. On the other hand, if the ratio of the candidate resources within the resource sensing window to all resources is equal to or greater than the threshold, the transmitting terminal may maintain or reduce the CW size.

[0178] [Equation 2]

[0179]

[0180] The transmitting terminal may determine the final transmission resource by performing a resource selection operation on the candidate resource identified by the resource sensing operation. In order to perform SL transmission in the final transmission resource, the transmitting terminal may perform an LBT operation before the final transmission resource. The LBT operation may be performed based on a CW having a CW size adjusted according to Equation 1 or Equation 2. If the LBT operation is successful, the transmitting terminal may send data to the receiving terminal. If the LBT operation fails, the transmitting terminal may not send data to the receiving terminal.

[0181] Fig.10 is a sequence listing illustrating a first exemplary embodiment of the SL-U communication method.

[0182] like Fig.10 As shown, SL-U communication can be performed between a transmitting terminal and a receiving terminal. SL-U communication can be unicast communication, multicast communication, or broadcast communication. The base station can send CW configuration information to the transmitting terminal and / or the receiving terminal. The CW configuration information can be transmitted based on at least one of SI signaling, RRC signaling, MAC signaling, or PHY signaling.

[0183] The transmitting terminal and / or the receiving terminal may receive CW configuration information from the base station and identify information elements included in the CW configuration information. The CW configuration information may include at least one of configuration information of a CAPC-CW table, mapping information between a priority and a CAPC, mapping information between a CBR (or CR) and a CAPC, a reference parameter for CW size adjustment, or a threshold for CW size adjustment.

[0184] The reference parameter for CW size adjustment may include at least one of the distance d between the transmitting terminal and the receiving terminal, RSRP (or RSSI, RSRQ, SINR), the region (e.g., area) where the transmitting terminal and / or the receiving terminal is located, CBR (or CR), the number of NACKs, the NACK ratio, the number of candidate resources, the ratio of candidate resources, the number of reserved resources, or the ratio of reserved resources. Information indicating one of the reference parameters for CW size adjustment may be included in the CW configuration information.

[0185] One of the reference parameters for CW size adjustment may be explicitly or implicitly indicated. For example, if the threshold value included in the CW configuration information is a CBR threshold value, it may implicitly indicate that the CBR is a reference parameter. Similarly, if the threshold value included in the CW configuration information is a reserved resource threshold value, it may implicitly indicate that the number of reserved resources or the ratio of reserved resources is a reference parameter.

[0186] As another method, the CW configuration information may be transmitted by a transmitting terminal instead of a base station. For example, the transmitting terminal may generate the CW configuration information based on at least one of RRC signaling, MAC signaling, or PHY signaling and send the CW configuration information to the receiving terminal. The receiving terminal may receive the CW configuration information and identify the information element included in the CW configuration information.

[0187] The transmitting terminal may determine a CW size (e.g., a minimum CW size) corresponding to a CAPC of the transmitting terminal (e.g., for SL transmission of the transmitting terminal) from a CAPC-CW table (S1001). The transmitting terminal may perform an LBT operation based on a CW having a minimum CW size, and if the LBT operation is successful, transmit data to the receiving terminal (S1002). The receiving terminal may receive data from the transmitting terminal. If the HARQ feedback operation is disabled, the receiving terminal may not send HARQ feedback for the data to the transmitting terminal. If the HARQ feedback operation is enabled, a NACK-only scheme is used, and data of the transmitting terminal is successfully received, the receiving terminal may not send HARQ feedback (e.g., ACK) for the data to the transmitting terminal.

[0188] In case that HARQ feedback (eg, ACK and / or NACK) is not received, the transmitting terminal may adjust the CW size based on a parameter (eg, a reference parameter) other than the HARQ feedback (S1003).

[0189] CW size adjustment when the reference parameter is distance d

[0190] The transmitting terminal may estimate the distance d between the transmitting terminal and the receiving terminal. For example, if the estimated distance d is less than a threshold, the transmitting terminal may increase the CW size. If the estimated distance d is equal to or greater than the threshold, the transmitting terminal may maintain or reduce the CW size. The above operation may also be performed in the opposite manner. If the transmitting terminal and / or the receiving terminal has mobility, adjusting the CW size based on the estimated distance d may improve the performance of the communication system.

[0191] CW size adjustment when the reference parameter is RSRP (or RSSI, RSRQ, SINR)

[0192] The transmitting terminal may estimate RSRP (or RSSI, RSRQ, SINR) based on a signal (e.g., a reference signal) received from the receiving terminal. For example, if the estimated RSRP is less than a threshold, the transmitting terminal may increase the CW size. If the estimated RSRP is equal to or greater than the threshold, the transmitting terminal may maintain or reduce the CW size. The above operation may also be performed in the opposite manner.

[0193] CW Sizing When the Reference Parameter is a Region (eg, Area)

[0194] The transmitting terminal may determine the region where the receiving terminal is located. For example, if the region where the transmitting terminal is located is different from the region where the receiving terminal is located, the transmitting terminal may increase the CW size. If the region where the transmitting terminal is located is the same as the region where the receiving terminal is located, the transmitting terminal may maintain or reduce the CW size. The above operation may also be performed in the opposite manner.

[0195] CW size adjustment when the reference parameter is CBR (or CR)

[0196] The transmitting terminal may measure the CBR (or CR). The CBR may be the CBR for a channel between the transmitting terminal and the receiving terminal. For example, if the measured CBR is equal to or greater than a threshold, the transmitting terminal may increase the CW size. If the measured CBR is less than the threshold, the transmitting terminal may maintain or reduce the CW size. The above operation may also be performed in the opposite manner.

[0197] CW Sizing When Reference Parameters Are Candidate Resources

[0198] The transmitting terminal may identify available candidate resources by performing a resource sensing operation within a resource sensing window. If the ratio of the number of candidate resources to the total number of resources within the resource sensing window (or the number of candidate resources / the total number of resources within the resource sensing window × 100) is less than a threshold, the transmitting terminal may increase the CW size. If the ratio of the number of candidate resources to the total number of resources within the resource sensing window (or the number of candidate resources / the total number of resources within the resource sensing window × 100) is equal to or greater than a threshold, the transmitting terminal may maintain or reduce the CW size. The above operation may also be performed in the opposite manner.

[0199] CW size adjustment when the reference parameter is reserved resources

[0200] The transmitting terminal may identify resources reserved by other terminals by performing a resource sensing operation within a resource sensing window. The reserved resources may include resources occupied by other terminals. If the ratio of the number of reserved resources to the total number of resources within the resource sensing window (or the number of reserved resources / the total number of resources within the resource sensing window × 100) is equal to or greater than a threshold, the transmitting terminal may increase the CW size. If the ratio of the number of reserved resources to the total number of resources within the resource sensing window (or the number of reserved resources / the total number of resources within the resource sensing window × 100) is less than a threshold, the transmitting terminal may maintain or reduce the CW size. The above operations may also be performed in the opposite manner.

[0201] In step S1003, the CW size may be adjusted within the range of the minimum CW size and the maximum CW size corresponding to the CAPC. After performing step S1003, the transmitting terminal may perform an LBT operation based on the CW with the adjusted CW size (S1004). If the LBT operation is successful, the transmitting terminal may send data to the receiving terminal (S1005). If the LBT operation fails, the transmitting terminal may not send the data. The receiving terminal may receive the data from the transmitting terminal and perform a HARQ feedback transmission operation on the data according to the HARQ feedback scheme.

[0202] In the present invention, the situation where ACK is not received may refer to a situation where TB decoding fails in unicast transmission and therefore ACK is not transmitted, a situation where SCI is not received in unicast transmission and therefore HARQ feedback (e.g., ACK) is not transmitted, a situation where TB decoding fails in multicast option 2 and therefore ACK is not transmitted, and / or a situation where SCI is not received in multicast transmission and therefore HARQ feedback (e.g., ACK) is not transmitted.

[0203] In SL-U communication, the CW size may be configured for each resource pool. Alternatively, in SL-U communication, the CW size may be configured service-specifically. The CW size configuration method may be applied differently depending on the broadcast type (e.g., unicast, multicast, broadcast).

[0204] In the above-mentioned SL-U communication, CW configuration information (e.g., CW size configuration information) may be specifically, independently or jointly configured based on at least one of a resource pool, a service type, a priority, whether to perform a power saving operation, a QoS parameter (e.g., reliability, delay), a broadcast type or a terminal type (e.g., a vehicle (V)-UE or a pedestrian (P)-UE). The above-mentioned configuration may be performed by a network and / or a base station. Alternatively, the above-mentioned information may be implicitly determined based on pre-configured parameters.

[0205] In the above exemplary embodiments, whether to apply each method (e.g., each rule) can be configured based on at least one of a condition, a combination of conditions, a parameter, or a combination of parameters. Whether to apply each method can be configured by the network and / or the base station. Whether to apply each method can be configured specific to a resource pool or a service. Alternatively, whether to apply each method can be configured by PC5-RRC signaling between terminals.

[0206] The operation of the method according to the exemplary embodiment of the present invention can be implemented as a computer-readable program or code in a computer-readable recording medium. The computer-readable recording medium may include a recording device of all types having data that can be read by a computer system. In addition, the computer-readable recording medium can store and execute programs or codes, which can be distributed in a computer system connected via a network and read by a computer in a distributed manner.

[0207] Computer readable recording media may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM or flash memory. Program instructions may include not only machine language codes created by a compiler, but also high-level language codes that can be executed by a computer using an interpreter.

[0208] Although some aspects of the present invention have been described in the context of a device, these aspects may indicate the corresponding description according to the method, and a block or device may correspond to the step of the method or the feature of the step. Similarly, the aspects described in the context of the method may be represented as the feature of a corresponding block or project or a corresponding device. Some or all steps of the method may be performed by (or using) a hardware device such as a microprocessor, a programmable computer or an electronic circuit. In some embodiments, one or more of the most important steps of the method may be performed by such a device.

[0209] In some exemplary embodiments, a programmable logic device such as a field programmable gate array can be used to perform some or all of the functions of the methods described herein. In some exemplary embodiments, the field programmable gate array can be operated with a microprocessor to perform one of the methods described herein. Typically, the method is preferably performed by a specific hardware device.

[0210] The description of the present invention is merely exemplary in nature, and therefore variant forms that do not deviate from the essence of the present invention are intended to be within the scope of the present invention. Such variant forms should not be considered as departing from the spirit and scope of the present invention. Therefore, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope defined by the appended claims.

Claims

1. A method for transmitting a user equipment (UE), comprising: performing a first listen-before-talk (LBT) operation based on a contention window (CW) having a first CW size; In response to the first LBT operation being successful, sending first data to a receiving UE; adjusting the first CW size based on a reference parameter instead of a hybrid automatic repeat request (HARQ) feedback for the first data; performing a second LBT operation based on the CW having the adjusted CW size; and In response to the second LBT operation being successful, second data is sent to the receiving UE.

2. The method according to claim 1, further comprising: receiving, from a base station, a first signaling message including configuration information of a plurality of channel access priority classes (CPAC)-CW tables; as well as receiving, from the base station, a second signaling message including configuration information indicating one CAPC-CW table among the plurality of CAPC-CW tables, The first CW size is a CW size corresponding to the CAPC of the sending UE in a CAPC-CW table.

3. The method according to claim 1, wherein: Adjusting the first CW size includes: estimating the distance between the transmitting UE and the receiving UE; and increasing the first CW size in response to the estimated distance being greater than or equal to a threshold, and maintaining or decreasing the first CW size in response to the estimated distance being less than the threshold, Wherein, the reference parameter is distance.

4. The method according to claim 1, wherein: Adjusting the first CW size includes: estimating a reference signal received power (RSRP) based on a signal received from a receiving UE; and In response to the estimated RSRP being less than a threshold, increasing the first CW size, and in response to the estimated RSRP being greater than or equal to the threshold, maintaining or decreasing the first CW size, Wherein, the reference parameter is RSRP.

5. The method according to claim 1, wherein: Adjusting the first CW size includes: identifying a second region where the receiving UE is located; and In response to a first region where the sending UE is located being different from a second region, the first CW size is increased, and in response to the first region being the same as the second region, the first CW size is maintained or decreased, The reference parameter is the region where each of the sending UE and the receiving UE is located.

6. The method according to claim 1, wherein: Adjusting the first CW size includes: measuring a channel busy rate (CBR) for a channel between a transmitting UE and a receiving UE; and increasing the first CW size in response to the measured CBR being greater than or equal to a threshold, and maintaining or decreasing the first CW size in response to the measured CBR being less than the threshold, Wherein, the reference parameter is CBR.

7. The method according to claim 1, wherein: Adjusting the first CW size includes: identifying candidate resources available to the transmitting UE by performing a resource sensing operation within a resource sensing window; and increasing the first CW size in response to a ratio of the candidate resources to the total resources belonging to the resource sensing window being less than a threshold, and maintaining or decreasing the first CW size in response to a ratio of the candidate resources to the total resources being greater than or equal to the threshold, The reference parameter is the number of candidate resources.

8. The method according to claim 1, wherein: Adjusting the first CW size includes: identifying resources reserved by other UEs by performing a resource sensing operation within a resource sensing window; and increasing the first CW size in response to a ratio of the reserved resources to the total resources belonging to the resource sensing window being greater than or equal to a threshold, and maintaining or decreasing the first CW size in response to a ratio of the reserved resources to the total resources being less than the threshold, The reference parameter is the quantity of reserved resources.

9. The method according to claim 1, further comprising: CW configuration information is received from a base station, wherein the CW configuration information includes at least one information indicating a reference parameter or a threshold for adjusting a first CW size.

10. A transmitting user equipment (UE), comprising at least one processor, wherein: The at least one processor causes the sending UE to execute: performing a first listen-before-talk (LBT) operation based on a contention window (CW) having a first CW size; In response to the first LBT operation being successful, sending first data to a receiving UE; adjusting the first CW size based on a reference parameter instead of a hybrid automatic repeat request (HARQ) feedback for the first data; performing a second LBT operation based on the CW having the adjusted CW size; and In response to the second LBT operation being successful, second data is sent to the receiving UE.

11. The sending UE according to claim 10, wherein: The at least one processor further causes the sending UE to execute: receiving a first signaling message including configuration information of a plurality of channel access priority class (CPAC)-CW tables from a base station; and receiving, from the base station, a second signaling message including configuration information indicating one CAPC-CW table among the plurality of CAPC-CW tables, The first CW size is a CW size corresponding to the CAPC of the sending UE in a CAPC-CW table.

12. The sending UE according to claim 10, wherein: When adjusting the first CW size, the at least one processor causes the sending UE to perform: Estimating the distance between the sending UE and the receiving UE; as well as increasing the first CW size in response to the estimated distance being greater than or equal to a threshold, and maintaining or decreasing the first CW size in response to the estimated distance being less than the threshold, Wherein, the reference parameter is distance.

13. The sending UE according to claim 10, wherein: When adjusting the first CW size, the at least one processor causes the sending UE to perform: estimating a reference signal received power (RSRP) based on a signal received from a receiving UE; and In response to the estimated RSRP being less than a threshold, increasing the first CW size, and in response to the estimated RSRP being greater than or equal to the threshold, maintaining or decreasing the first CW size, Wherein, the reference parameter is RSRP.

14. The sending UE according to claim 10, wherein: When adjusting the first CW size, the at least one processor causes the sending UE to perform: identifying a second region where the receiving UE is located; and In response to a first region where the sending UE is located being different from a second region, the first CW size is increased, and in response to the first region being the same as the second region, the first CW size is maintained or decreased, The reference parameter is the region where each of the sending UE and the receiving UE is located.

15. The sending UE according to claim 10, wherein: When adjusting the first CW size, the at least one processor causes the sending UE to perform: measuring a channel busy rate (CBR) for a channel between a transmitting UE and a receiving UE; and increasing the first CW size in response to the measured CBR being greater than or equal to a threshold, and maintaining or decreasing the first CW size in response to the measured CBR being less than the threshold, Wherein, the reference parameter is CBR.

16. The sending UE according to claim 10, wherein: When adjusting the first CW size, the at least one processor causes the sending UE to perform: identifying candidate resources available to the transmitting UE by performing a resource sensing operation within a resource sensing window; and increasing the first CW size in response to a ratio of the candidate resources to the total resources belonging to the resource sensing window being less than a threshold, and maintaining or decreasing the first CW size in response to a ratio of the candidate resources to the total resources being greater than or equal to the threshold, The reference parameter is the number of candidate resources.

17. The sending UE according to claim 10, wherein: When adjusting the first CW size, the at least one processor causes the sending UE to perform: identifying resources reserved by other UEs by performing a resource sensing operation within a resource sensing window; and increasing the first CW size in response to a ratio of the reserved resources to the total resources belonging to the resource sensing window being greater than or equal to a threshold, and maintaining or decreasing the first CW size in response to a ratio of the reserved resources to the total resources being less than the threshold, The reference parameter is the quantity of reserved resources.

18. The sending UE according to claim 10, wherein: The at least one processor further causes the transmitting UE to execute: receiving CW configuration information from a base station, wherein the CW configuration information includes at least one information indicating a reference parameter or a threshold for adjusting the first CW size.

Images