Method and apparatus for sidelink channel access in unlicensed band

Abstract

A method and apparatus for sidelink channel access in an unlicensed frequency band are disclosed. The method of the first terminal comprises the steps of: transmitting data to the plurality of terminals based on a multicast method; receiving one or more HARQ-ACK (Hybrid Automatic Repeat reQuest-Acknowledgement) feedbacks on the data from one or more terminals in a plurality of terminals; adjusting a CW size based on a comparison result between an ACK ratio of the one or more HARQ-ACK feedbacks and a threshold value; and performing SL communication based on the CW having the adjusted CW size.

Description

Technical Field

[0001] The present disclosure relates to sidelink communication techniques, and more particularly, to techniques for accessing a sidelink channel in an unlicensed band. Background Art

[0002] A communication system (e.g., a new radio (NR) communication system) using a higher frequency band (e.g., a frequency band of 6 GHz or higher) than that of a long term evolution (LTE) communication system (or LTE-A communication system) (e.g., a frequency band of 6 GHz or lower) is being considered for handling the surge in wireless data. The NR system can support not only a frequency band of 6 GHz or lower but also a frequency band of 6 GHz or higher, and can support various communication services and scenarios compared to the LTE system. In addition, requirements for the NR system may include enhanced mobile broadband (eMBB), ultra-reliable low latency communication (URLLC), and massive machine type communication (mMTC).

[0003] In addition, the NR communication system may support side link (SL) communication, and SL communication of the NR communication system may be performed in an unlicensed band. In this case, the transmitting terminal may perform SL communication based on a listen before conversation (LBT) operation. For example, the transmitting terminal may select a backoff value within a content window (CW), and if the channel is idle during a time corresponding to the backoff value, SL communication is performed. In order to efficiently perform SL communication, a method for adjusting the size of the CW is required. Summary of the invention

[0004] Technical issues The present disclosure is directed to a method and apparatus for accessing a sidelink channel in an unlicensed frequency band.

[0005] Technical Solution According to an exemplary embodiment of the present disclosure, a method for a first terminal to achieve the above-mentioned purpose may include: sending data to multiple terminals based on a multicast scheme; receiving one or more hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedbacks for the data from one or more terminals among the multiple terminals; adjusting a content window (CW) size based on a comparison result between a threshold and an ACK ratio of the one or more HARQ-ACK feedbacks; and performing side link (SL) communication based on the CW with the adjusted CW size.

[0006] When the ACK ratio is equal to or greater than the threshold, the CW size may be reduced, and when the ACK ratio is less than the threshold, the CW size may be increased.

[0007] When the ACK ratio is equal to or greater than the threshold, the CW size may be adjusted to a minimum CW size.

[0008] The method may further include receiving a higher layer message including information about the threshold from a base station.

[0009] The threshold may be set in a user equipment (UE) specific manner or in a cell specific manner.

[0010] The threshold may be set independently for each resource pool.

[0011] The minimum CW size and the maximum CW size of the CW sizes may be independently set according to a channel access priority level (CAPC), respectively.

[0012] When at least one HARQ-ACK feedback is not received from at least one terminal among the plurality of terminals, the at least one HARQ-ACK feedback for the at least one terminal may be regarded as a negative ACK (NACK).

[0013] According to an exemplary embodiment of the present disclosure, a method for a first terminal to achieve the above-mentioned purpose may include: using a first contention window (CW) having a first CW size to perform a first side link (SL) communication; and when a hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedback function is disabled, using the first CW having the first CW size as the latest size to perform a second SL communication.

[0014] The method may further include: adjusting the first CW size to a second CW size larger than the first CW size when the first CW size is used x times; and performing a third SL communication using a second CW having the second CW size, wherein x is a natural number.

[0015] The method may further include receiving a higher layer message including information about x from the base station.

[0016] x may be set in a user equipment (UE) specific manner or in a cell specific manner.

[0017] The method may further include: when the first CW size is a maximum CW size and the maximum CW size is used x times, adjusting the first CW size to a minimum CW size; and performing a fourth SL communication using a minimum CW having the minimum CW size, wherein x is a natural number.

[0018] The minimum CW size and the maximum CW size of the first CW size may be independently set according to a channel access priority level (CAPC), respectively.

[0019] According to an exemplary embodiment of the present disclosure, a first terminal for achieving the above-mentioned purpose may include at least one processor, and the at least one processor may enable the first terminal to execute: sending data to multiple terminals based on a multicast scheme; receiving one or more hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedbacks for the data from one or more of the multiple terminals; adjusting a content window (CW) size based on a comparison result between a threshold and an ACK ratio of the one or more HARQ-ACK feedbacks; and performing side link (SL) communication based on the CW with the adjusted CW size.

[0020] When the ACK ratio is equal to or greater than the threshold, the CW size may be reduced, and when the ACK ratio is less than the threshold, the CW size may be increased.

[0021] The at least one processor may further cause the first terminal to perform: receiving a higher layer message including information about the threshold from a base station.

[0022] The threshold may be set in a user equipment (UE) specific manner or in a cell specific manner.

[0023] The minimum CW size and the maximum CW size of the CW sizes may be independently set according to a channel access priority level (CAPC), respectively.

[0024] When at least one HARQ-ACK feedback is not received from at least one terminal among the plurality of terminals, the at least one HARQ-ACK feedback for the at least one terminal may be regarded as a negative ACK (NACK).

[0025] Beneficial Effects According to the present disclosure, a transmitting terminal may perform SL communication with a receiving terminal in an unlicensed band. The transmitting terminal may send data to the receiving terminal and receive HARQ-ACK feedback for the data. The transmitting terminal may adjust the CW size based on the ACK ratio or negative ACK (NACK) ratio of the HARQ-ACK feedback, and may perform SL communication with the receiving terminal based on the CW with the adjusted CW size. The CW size may be appropriately adjusted according to the communication state between the transmitting terminal and the receiving terminal, so that SL communication may be effectively performed and the performance of the communication system may be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a conceptual diagram illustrating a first exemplary embodiment of a communication system.

[0027] Figure 2 is a block diagram showing a first exemplary embodiment of a communication node constituting a communication system.

[0028] Figure 3 is a conceptual diagram illustrating a first exemplary embodiment of a type 1 frame.

[0029] Figure 4 is a conceptual diagram illustrating a first exemplary embodiment of a type 2 frame.

[0030] Figure 5 is a conceptual diagram illustrating a first exemplary embodiment of a transmission method of an SS / PBCH block in a communication system.

[0031] Figure 6 is a conceptual diagram illustrating a first exemplary embodiment of an SS / PBCH block in a communication system.

[0032] Figure 7 is a conceptual diagram illustrating a second exemplary embodiment of a method of transmitting an SS / PBCH block in a communication system.

[0033] Figure 8 is a conceptual diagram showing a first exemplary embodiment of an SSB burst configuration.

[0034] Figure 9a is a conceptual diagram showing RMSI CORESET mapping mode #1 in a communication system.

[0035] Figure 9b is a conceptual diagram showing RMSI CORESET mapping mode #2 in a communication system.

[0036] Fig.9c is a conceptual diagram showing RMSI CORESET mapping mode #3 in a communication system.

[0037] Fig.10 is a conceptual diagram showing a first exemplary embodiment of a configuration of a time slot configuring a PSFCH.

[0038] Fig.11 is a conceptual diagram showing a first exemplary embodiment of a PSFCH for ACK / NACK transmission.

[0039] Fig.12 is a conceptual diagram illustrating an exemplary embodiment of a method for multiplexing a control channel and a data channel in sidelink communication.

[0040] Fig.13 is a conceptual diagram illustrating a first exemplary embodiment of a resource selection operation.

[0041] Fig.14 is a conceptual diagram illustrating a first exemplary embodiment of a resource reselection operation.

[0042] Fig.15ais a conceptual diagram illustrating a first exemplary embodiment of a COT sharing method in SL communication.

[0043] Fig.15b is a conceptual diagram illustrating a second exemplary embodiment of a COT sharing method in SL communication.

[0044] Fig.16 is a conceptual diagram of a first exemplary embodiment showing different offsets for a shared terminal.

[0045] Fig.17a is a conceptual diagram illustrating a first exemplary embodiment of SL transmission.

[0046] Fig.17b is a conceptual diagram illustrating a second exemplary embodiment of SL transmission. DETAILED DESCRIPTION

[0047] Exemplary embodiments of the present disclosure are disclosed herein. However, for the purpose of describing the embodiments of the present disclosure, the specific structural and functional details disclosed herein are only representative. Therefore, the embodiments of the present disclosure can be implemented in many alternative forms and should not be interpreted as being limited to the embodiments of the present disclosure set forth herein.

[0048] It should be understood that although the terms first, second, etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element. As used herein, the term "and / or" includes any one of the associated listed items and all combinations of one or more of the listed items.

[0049] In an exemplary embodiment of the present disclosure, “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”. Furthermore, in an exemplary embodiment of the present disclosure, “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”.

[0050] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or intervening elements may be present. Conversely, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other words used to describe the relationship between elements should be interpreted in a similar manner (i.e., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0051] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, unless the context clearly states otherwise, the singular form is intended to also include the plural form. It will be further understood that the terms "include", "comprise", "contain", and / or "comprises" specify the presence of stated features, integers, steps, operations, elements, and / or components when used herein, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0052] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. It will be further understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such in this article.

[0053] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. In order to facilitate general understanding when describing the present disclosure, the same components in the drawings are denoted by the same reference numerals, and repeated description thereof will be omitted.

[0054] A communication system to which an exemplary embodiment according to the present disclosure is applied will be described. The communication system may be a 4G communication system (e.g., a long term evolution (LTE) communication system or an LTE-A communication system), a 5G communication system (e.g., a new radio (NR) communication system), a sixth generation (6G) communication system, etc. The 4G communication system may support communications in a frequency band of 6 GHz or lower, and the 5G communication system may support communications in a frequency band of 6 GHz or higher and a frequency band of 6 GHz or lower. The communication system to which the exemplary embodiment according to the present disclosure is applied is not limited to the contents described below, and the exemplary embodiments according to the present disclosure may be applied to various communication systems. Here, the communication system may be used in the same sense as the communication network, and "LTE" may refer to a "4G communication system", "LTE communication system" or "LTE-A communication system", and "NR" may refer to a "5G communication system" or "NR communication system".

[0055] In an exemplary embodiment, “an operation (e.g., a transmission operation) is configured” may mean “configuration information (e.g., an information element or parameter) for the operation and / or information indicating the execution of the operation is notified by signaling”. “An information element (e.g., a parameter) is configured” may mean “a corresponding information element is notified by signaling”. The signaling may be at least one of system information (SI) signaling (e.g., transmission of a system information block (SIB) and / or a master information block (MIB)), RRC signaling (e.g., transmission of RRC parameters and / or higher layer parameters), MAC control element (CE) signaling, or PHY signaling (e.g., transmission of downlink control information (DCI), uplink control information (UCI), and / or sidelink control information (SCI)).

[0056] In the following, even when describing a method (e.g., transmission or reception of a signal) performed at a first communication node among communication nodes, the corresponding second communication node may also perform a method (e.g., reception or transmission of a signal) corresponding to the method performed at the first communication node. That is, when describing the operation of a terminal, a base station corresponding to the terminal may perform an operation corresponding to the operation of the terminal. Conversely, when describing the operation of a base station, a terminal corresponding to the base station may perform an operation corresponding to the operation of the base station. In addition, when describing the operation of a first terminal, a second terminal corresponding to the first terminal may perform an operation corresponding to the operation of the first terminal. Conversely, when describing the operation of a second terminal, a first terminal corresponding to the second terminal may perform an operation corresponding to the operation of the second terminal.

[0057] Figure 1 is a conceptual diagram illustrating a first exemplary embodiment of a communication system.

[0058] refer to Figure 1 , the communication system 100 may include a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. In addition, the communication system 100 may also include a core network (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), and a mobile management entity (MME)). When the communication system 100 is a 5G communication system (e.g., a new radio (NR) system), the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), and the like.

[0059] The plurality of communication nodes 110 to 130 may support a communication protocol defined by the third generation partnership project (3GPP) specification (e.g., LTE communication protocol, LTE-A communication protocol, NR communication protocol, etc.). The plurality of communication nodes 110 to 130 may support code division multiple access (CDMA) technology, wideband CDMA (WCDMA) technology, time division multiple access (TDMA) technology, frequency division multiple access (FDMA) technology, orthogonal frequency division multiplexing (OFDM) technology, filtered OFDM technology, cyclic prefix OFDM (CP-OFDM) technology, discrete Fourier transform spread OFDM (DFT-s-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 band multi-carrier (FBMC) technology, universal filter multi-carrier (UFMC) technology, space division multiple access (SDMA) technology, etc. Each of the plurality of communication nodes may have the following structure.

[0060] Figure 2 is a block diagram showing a first exemplary embodiment of a communication node constituting a communication system.

[0061] refer to Figure 2 , the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network for performing communication. In addition, the communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, etc. Each component included in the communication node 200 can communicate with each other because it is connected through the bus 270.

[0062] However, each component included in the communication node 200 may not be connected to the common bus 270, but may be connected to the processor 210 via a separate interface or a separate bus. For example, the processor 210 may be connected to at least one of the memory 220, the transceiver 230, the input interface device 240, the output interface device 250, and the storage device 260 via a dedicated interface.

[0063] The processor 210 may execute a program stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the method according to an embodiment of the present disclosure is executed. Each of the memory 220 and the storage device 260 may be composed of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may include at least one of a read-only memory (ROM) and a random access memory (RAM).

[0064] Reference again Figure 1, the communication system 100 may include a plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 and a plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell, and each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the cell coverage of the first base station 110-1. In addition, the second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the cell coverage of the second base station 110-2. In addition, the fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5 and the sixth terminal 130-6 may belong to the cell coverage of the third base station 110-3. In addition, the first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1, and the sixth terminal 130-6 may belong to the cell coverage of the fifth base station 120-2.

[0065] Here, each of the multiple base stations 110-1, 110-2, 110-3, 120-1 and 120-2 may refer to a node B (NB), an evolved node B (eNB), a gNB, an advanced base station (ABS), a high reliability base station (HR-BS), a base transceiver station (BTS), a radio base station, a radio transceiver, an access point, an access node, a radio access station (RAS), a mobile multi-hop relay base station (MMR-BS), a relay station (RS), an advanced relay station (ARS), a high reliability relay station (HR-RS), a home node B (HNB), a home eNodeB (HeNB), a road side unit (RSU), a remote radio head (RRH), a transmission point (TP), a transmit and receive point (TRP), etc.

[0066] Each of the multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5 and 130-6 may refer to a user equipment (UE), a terminal equipment (TE), an advanced mobile station (AMS), a high reliability mobile station (HR-MS), 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.

[0067] Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in the same frequency band or in different frequency bands. The plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other via an ideal backhaul or a non-ideal backhaul, and exchange information with each other via an ideal backhaul or a non-ideal backhaul. In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to a core network via an ideal backhaul or a non-ideal backhaul. Each of the multiple base stations 110-1, 110-2, 110-3, 120-1 and 120-2 can send a signal received from the core network to the corresponding terminal 130-1, 130-2, 130-3, 130-4, 130-5 or 130-6, and send a signal received from the corresponding terminal 130-1, 130-2, 130-3, 130-4, 130-5 or 130-6 to the core network.

[0068] In addition, each of the multiple base stations 110-1, 110-2, 110-3, 120-1 and 120-2 can support multiple-input multiple-output (MIMO) transmission (e.g., single-user MIMO (SU-MIMO), multi-user MIMO (MU-MIMO), massive MIMO, etc.), coordinated multi-point (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, device-to-device (D2D) communication (or proximity service (ProSe)), Internet of Things (IoT) communication, dual connectivity (DC), etc. Here, each of the multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5 and 130-6 can perform operations corresponding to the operations of the multiple base stations 110-1, 110-2, 110-3, 120-1 and 120-2 (i.e., operations supported by the multiple base stations 110-1, 110-2, 110-3, 120-1 and 120-2). For example, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 in SU-MIMO mode, and the fourth terminal 130-4 may receive a signal from the second base station 110-2 in SU-MIMO mode. Optionally, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 in MU-MIMO mode, and the fourth terminal 130-4 and the fifth terminal 130-5 may receive a signal from the second base station 110-2 in MU-MIMO mode.

[0069] The first base station 110-1, the second base station 110-2 and the third base station 110-3 can send signals to the fourth terminal 130-4 in a CoMP transmission manner, and the fourth terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2 and the third base station 110-3 in a CoMP manner. In addition, each of the multiple base stations 110-1, 110-2, 110-3, 120-1 and 120-2 can exchange signals with the corresponding terminal 130-1, 130-2, 130-3, 130-4, 130-5 or 130-6 belonging to its cell coverage in a CA manner. Each of base stations 110-1, 110-2, and 110-3 may control D2D communication between the fourth terminal 130-4 and the fifth terminal 130-5, and thus the fourth terminal 130-4 and the fifth terminal 130-5 may perform D2D communication under the control of the second base station 110-2 and the third base station 110-3.

[0070] In addition, the communication system may support three types of frame structures. A type 1 frame structure may be applied to a frequency division duplex (FDD) communication system, a type 2 frame structure may be applied to a time division duplex (TDD) communication system, and a type 3 frame structure may be applied to an unlicensed band-based communication system (e.g., a licensed assisted access (LAA) communication system).

[0071] Figure 3 is a conceptual diagram illustrating a first exemplary embodiment of a type 1 frame.

[0072] refer to Figure 3 , the radio frame 300 may include 10 subframes, and the subframe may include 2 time slots. Therefore, the radio frame 300 may include 20 time slots (e.g., time slot #0, time slot #1, time slot #2, time slot #3, ..., time slot #18, and time slot #19). The length T of the radio frame 300 is f The length of a subframe may be 1 ms, and the length of a time slot may be 10 ms. slot It can be 0.5ms. Here, T s The sampling time may be indicated and may be 1 / 30,720,000s.

[0073] A time slot may consist of a plurality of OFDM symbols in the time domain and may consist of a plurality of resource blocks (RBs) in the frequency domain. An RB may consist of a plurality of subcarriers in the frequency domain. The number of OFDM symbols constituting a time slot may vary depending on the configuration of a cyclic prefix (CP). CP may be classified into a normal CP and an extended CP. If a normal CP is used, a time slot may consist of 7 OFDM symbols, in which case a subframe may consist of 14 OFDM symbols. If an extended CP is used, a time slot may consist of 6 OFDM symbols, in which case a subframe may consist of 12 OFDM symbols.

[0074] Figure 4 is a conceptual diagram illustrating a first exemplary embodiment of a type 2 frame.

[0075] refer to Figure 4 , the radio frame 400 may include two half frames, and the half frame may include 5 subframes. Therefore, the radio frame 400 may include 10 subframes. The length T of the radio frame 400 f The length of a half frame can be 5 ms. The length of a subframe can be 1 ms. Here, T s It can be 1 / 30,720,000s.

[0076] The radio frame 400 may include at least one downlink subframe, at least one uplink subframe, and at least one special subframe. Each of the downlink subframe and the uplink subframe may include two time slots. The length of the time slot T slot It may be 0.5 ms. Among the subframes included in the radio frame 400, each of subframe #1 and subframe #6 may be a special subframe. For example, when the switching period between the downlink and the uplink is 5 ms, the radio frame 400 may include 2 special subframes. Alternatively, the switching period between the downlink and the uplink is 10 ms, and the radio frame 400 may include one special subframe. The special subframe may include a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS).

[0077] The downlink pilot time slot may be regarded as a downlink interval and may be used for cell search, time-frequency synchronization acquisition of a terminal, channel estimation, etc. The guard period may be used to solve the interference problem of uplink data transmission caused by the delay of downlink data reception. In addition, the guard period may include the time required to switch from a downlink data reception operation to an uplink data transmission operation. The uplink pilot time slot may be used for uplink channel estimation, time-frequency synchronization acquisition, etc. The transmission of a physical random access channel (PRACH) or a sounding reference signal (SRS) may be performed in the uplink pilot time slot.

[0078] The lengths of the downlink pilot slot, the guard period, and the uplink pilot slot included in the special subframe may be variably adjusted as needed. In addition, the number and position of each of the downlink subframe, the uplink subframe, and the special subframe included in the radio frame 400 may be changed as needed.

[0079] In a communication system, a transmission time interval (TTI) may be a basic time unit for sending coded data through a physical layer. Short TTI may be used to support low latency requirements in a communication system. The length of a short TTI may be less than 1 ms. A traditional TTI with a length of 1 ms may be referred to as a basic TTI or a conventional TTI. That is, a basic TTI may be composed of one subframe. In order to support transmission based on a basic TTI, signals and channels may be configured based on subframes. For example, a cell-specific reference signal (CRS), a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), etc. may be present in each subframe.

[0080] On the other hand, for every 5 subframes, there may be a synchronization signal (e.g., a primary synchronization signal (PSS) and a secondary synchronization signal (SSS)), and for every 10 subframes, there may be a physical broadcast channel (PBCH). In addition, each radio frame may be identified by an SFN, and the SFN may be used to define the transmission of a signal longer than one radio frame (e.g., a paging signal, a reference signal for channel estimation, a signal for channel state information, etc.). The period of the SFN may be 1024.

[0081] In an LTE system, PBCH may be a physical layer channel for transmitting system information, such as a master information block (MIB). PBCH may be transmitted once every 10 subframes. That is, the transmission period of PBCH may be 10ms, and PBCH may be transmitted once in a radio frame. The same MIB may be transmitted during 4 consecutive radio frames, and after 4 consecutive radio frames, the MIB may be changed according to the situation of the LTE system. The transmission period for transmitting the same MIB may be referred to as a "PBCH TTI", and the PBCH TTI may be 40ms. That is, the MIB may be changed for each PBCH TTI.

[0082] The MIB may be composed of 40 bits. Among the 40 bits constituting the MIB, 3 bits may be used to indicate a system frequency band, 3 bits may be used to indicate physical hybrid automatic repeat request (ARQ) indicator channel (PHICH) related information, 8 bits may be used to indicate SFN, 10 bits may be configured as reserved bits, and 16 bits may be used for a cyclic redundancy check (CRC).

[0083] The SFN used to identify the radio frame may consist of a total of 10 bits (B9 to B0), and the most significant bits (MSB) 8 bits (B9 to B2) of the 10 bits may be indicated by the PBCH (i.e., MIB). The MSB 8 bits (B9 to B2) of the SFN indicated by the PBCH (i.e., MIB) may be the same during 4 consecutive radio frames (i.e., PBCH TTI). The least significant bits (LSB) 2 bits (B1 to B0) of the SFN may change during 4 consecutive radio frames (i.e., PBCH TTI) and may not be explicitly indicated by the PBCH (i.e., MIB). The LSB (2 bits (B1 to B0)) of the SFN may be implicitly indicated by the scrambling sequence of the PBCH (hereinafter referred to as "PBCH scrambling sequence").

[0084] The gold sequence generated by being initialized according to the cell ID may be used as a PBCH scrambling sequence, and the PBCH scrambling sequence may be initialized for every four consecutive radio frames (e.g., each PBCH TTI) based on the operation of "mod(SFN, 4)". The PBCH transmitted in a radio frame corresponding to a SFN having LSB 2 bits (B1 to B0) set to "00" may be scrambled by the gold sequence generated by being initialized according to the cell ID. Thereafter, the gold sequence generated according to the operation of "mod(SFN, 4)" may be used to scramble the PBCH transmitted in a radio frame corresponding to a SFN having LSB 2 bits (B1 to B0) set to "01", "10", and "11".

[0085] Therefore, the terminal that has acquired the cell ID in the initial cell search process can identify the value of the LSB 2 bits (B1 to B0) of the SFN (for example, "00", "01", "10" or "11") based on the PBCH scrambling sequence obtained in the decoding process of the PBCH (ie, MIB). The terminal can use the LSB 2 bits (B1 to B0) of the SFN obtained based on the PBCH scrambling sequence and the MSB 8 bits (B9 to B2) of the SFN indicated by the PBCH (ie, MIB) to identify the SFN (ie, all bits B9 to B0 of the SFN).

[0086] On the other hand, the communication system can not only support high transmission rates, but also support the technical requirements of various service scenarios. For example, the communication system can support enhanced mobile broadband (eMBB) services, ultra-reliable low-latency communication (URLLC) services, massive machine type communication (mMTC) services, etc.

[0087] The subcarrier spacing of a communication system (e.g., an OFDM-based communication system) may be determined based on a carrier frequency offset (CFO), etc. The CFO may be generated by a Doppler effect, a phase drift, etc., and may be increased in proportion to the operating frequency. Therefore, in order to prevent performance degradation of the communication system due to the CFO, the subcarrier spacing may be increased in proportion to the operating frequency. On the other hand, as the subcarrier spacing increases, the CP overhead may increase. Therefore, the subcarrier spacing may be configured based on channel characteristics, radio frequency (RF) characteristics, etc., according to the frequency band.

[0088] The communication system may support the parameter sets defined in Table 1 below.

[0089] [Table 1]

[0090] For example, the subcarrier spacing of the communication system can be configured to be 15kHz, 30kHz, 60kHz, or 120kHz. The subcarrier spacing of the LTE system can be 15kHz, and the subcarrier spacing of the NR system can be 1, 2, 4, or 8 times the traditional subcarrier spacing of 15kHz. If the subcarrier spacing increases in exponential units of 2 of the traditional subcarrier spacing, the frame structure can be easily designed.

[0091] The communication system may support FR1 as well as FR2. FR2 may be classified into FR2-1 and FR2-2. FR1 may be a frequency band of 6 GHz or lower, FR2-1 may be a frequency band of 24.25 to 52.6 GHz, and FR2-2 may be a frequency band of 52.6 to 71 GHz. In an exemplary embodiment, FR2 may be FR2-1, FR2-1, or a frequency band including FR2-1 and FR2-2. In each of FR1, FR2-1, and FR2-2, the subcarrier spacing available for data transmission may be defined as shown in Table 2 below. In each of FR1, FR2-1, and FR2-2, the SCS available for synchronization signal block (SSB) transmission may be defined as shown in Table 3 below. In each of FR1, FR2-1, and FR2-2, the SCS available for RACH transmission (e.g., Msg1 or Msg-A) may be defined as shown in Table 4 below.

[0092] [Table 2]

[0093] [Table 3]

[0094] [Table 4]

[0095] The communication system can support broadband (e.g., hundreds of MHz to tens of GHz). Since the diffraction characteristics and reflection characteristics of radio waves are poor in high frequency bands, the propagation loss (e.g., path loss, reflection loss, etc.) in the high frequency bands can be greater than the propagation loss in the low frequency bands. Therefore, the cell coverage of the communication system supporting the high frequency bands can be less than the cell coverage of the communication system supporting the low frequency bands. In order to solve such problems, the beamforming scheme based on multiple antenna elements can be used to increase the cell coverage in the communication system supporting the high frequency bands.

[0096] The beamforming scheme may include a digital beamforming scheme, an analog beamforming scheme, a hybrid beamforming scheme, etc. In a communication system using a digital beamforming scheme, a plurality of RF paths may be used based on a digital precoder or a codebook to obtain beamforming gain. In a communication system using an analog beamforming scheme, an analog RF device (e.g., a phase shifter, a power amplifier (PA), a variable gain amplifier (VGA), etc.) and an antenna array may be used to obtain beamforming gain.

[0097] Since an expensive digital-to-analog converter (DAC) or analog-to-digital converter (ADC) is required for the digital beamforming scheme and a transceiver unit corresponding to the number of antenna elements, in order to increase the beamforming gain, the complexity of the antenna implementation will increase. In the case of a communication system using an analog beamforming scheme, since multiple antenna elements are connected to one transceiver unit through a phase shifter, the complexity of the antenna implementation will not increase greatly even if the beamforming gain increases. However, the beamforming performance of the communication system using the analog beamforming scheme will be lower than that of the communication system using the digital beamforming scheme. In addition, in a communication system using an analog beamforming scheme, since the phase shifter is adjusted in the time domain, frequency resources may not be used effectively. Therefore, a hybrid beamforming scheme, which is a combination of a digital scheme and an analog scheme, can be used.

[0098] When the cell coverage is increased by using a beamforming scheme, a common control channel and a common signal (e.g., a reference signal and a synchronization signal) for all terminals belonging to the cell coverage and a control channel and a data channel for each terminal may also be sent based on the beamforming scheme. In this case, a common control channel and a common signal for all terminals belonging to the cell coverage may be sent based on a beam scanning scheme.

[0099] In addition, in the NR system, a synchronization signal / physical broadcast channel (SS / PBCH) block can also be sent in a beam scanning scheme. The SS / PBCH block may be composed of PSS, SSS, PBCH, etc. In the SS / PBCH block, PSS, SSS, and PBCH may be configured in a time division multiplexing (TDM) manner. The SS / PBCH block may also be referred to as a "SS block (SSB)". One SS / PBCH block may be sent using N consecutive OFDM symbols. Here, N may be an integer equal to or greater than 4. The base station may periodically send SS / PBCH blocks, and the terminal may acquire frequency / time synchronization, cell ID, system information, etc. based on the SS / PBCH blocks received from the base station. The SS / PBCH block may be sent as follows.

[0100] Figure 5 is a conceptual diagram illustrating a first exemplary embodiment of a transmission method of an SS / PBCH block in a communication system.

[0101] refer to Figure 5 , one or more SS / PBCH blocks may be sent in a beam scanning scheme within an SS / PBCH block burst set. Up to L SS / PBCH blocks may be sent within one SS / PBCH block burst set. L may be an integer equal to or greater than 2 and may be defined in the 3GPP standard. L may vary depending on the region of the system frequency. Within an SS / PBCH block burst set, SS / PBCH blocks may be positioned continuously or dispersedly. Continuous SS / PBCH blocks may be referred to as "SS / PBCH block bursts". SS / PBCH block burst sets may be repeated periodically, and system information (e.g., MIB) sent via the PBCH of SS / PBCH blocks within an SS / PBCH block burst set may be the same. The index of the SS / PBCH block, the index of the SS / PBCH block burst, the index of the OFDM symbol, the index of the time slot, and the like may be indicated explicitly or implicitly via the PBCH.

[0102] Figure 6 is a conceptual diagram illustrating a first exemplary embodiment of an SS / PBCH block in a communication system.

[0103] refer to Figure 6 , signals and channels follow the "PSS PBCH SSS The PSS, SSS, and PBCH in the SS / PBCH block are arranged in the order of "PBCH" and "SS / PBCH" in one SS / PBCH block. The PSS, SSS, and PBCH in the SS / PBCH block can be configured in a TDM scheme. In the symbol where the SSS is located, the PBCH can be located in the frequency resources above the SSS and the frequency resources below the SSS. That is, the PBCH can be transmitted in two end bands adjacent to the frequency band in which the SSS is transmitted. When the maximum number of SS / PBCH blocks in the sub-6 GHz band is 8, the SS / PBCH block index can be identified based on a demodulation reference signal (hereinafter referred to as "PBCH DMRS") for demodulating the PBCH. When the maximum number of SSBs in the band exceeding 6 GHz is 64, the LSB 3 bits of the 6 bits representing the SS / PBCH block index are identified based on the PBCH DMRS, and the remaining MSB 3 bits are identified based on the payload of the PBCH.

[0104] The maximum system bandwidth supportable in the NR system may be 400 MHz. The size of the maximum bandwidth supportable by the terminal may vary according to the capabilities of the terminal. Therefore, the terminal may perform an initial access procedure (e.g., an initial connection procedure) by using some system bandwidths of the NR system supporting a wideband. In order to support access procedures for terminals supporting various bandwidth sizes, SS / PBCH blocks may be multiplexed in the frequency domain within the system bandwidth of the NR system supporting a wideband. In this case, the SS / PBCH blocks may be sent as follows.

[0105] Figure 7 is a conceptual diagram illustrating a second exemplary embodiment of a method of transmitting an SS / PBCH block in a communication system.

[0106] refer to Figure 7 , a wideband component carrier (CC) may include multiple bandwidth parts (BWPs). For example, a wideband CC may include 4 BWPs. The base station may send SS / PBCH blocks in each BWP#0 to BWP#3 belonging to the wideband CC. The terminal may receive SS / PBCH blocks from one or more BWPs among BWP#0 to BWP#3, and may perform an initial access procedure using the received SS / PBCH blocks.

[0107] After detecting the SS / PBCH block, the terminal may acquire system information (e.g., remaining minimum system information (RMSI)), and may perform a cell access procedure based on the system information. RMSI may be sent on a PDSCH scheduled by a PDCCH. Configuration information of a control resource set (CORESET) may be sent on a PBCH within an SS / PBCH block, wherein the PDCCH includes scheduling information of a PDSCH through which RMSI is sent. Multiple SS / PBCH blocks may be sent throughout the system frequency band, and one or more SS / PBCH blocks among the multiple SS / PBCH blocks may be one or more SS / PBCH blocks associated with RMSI. The remaining SS / PBCH blocks may not be associated with RMSI. The SS / PBCH blocks associated with RMSI may be defined as "cell definition SS / PBCH blocks". The terminal may perform a cell search procedure and an initial access procedure by using a cell definition SS / PBCH block. SS / PBCH blocks not associated with RMSI may be used for a synchronization procedure and / or a measurement procedure in a corresponding BWP. The BWP through which the SS / PBCH block is sent may be limited to one or more BWPs within a wide bandwidth.

[0108] The position where the SSB is sent in the time domain may be defined differently depending on the values ​​of the SCS and L. In an exemplary embodiment, the SCS may represent a subcarrier size. The SSB may be sent in some symbols within a time slot, and short UL transmission (e.g., uplink control information (UCI) transmission) may be performed in the remaining symbols not used for SSB transmission within a time slot. When the SSB is sent in a radio resource to which a large SCS (e.g., 120kHz SCS or 240kHz SCS) is applied, a gap may be configured in the middle of consecutive time slots including the SSB so that a long UL transmission (e.g., transmission of a URLLC service) may be performed at least every 1ms.

[0109] Figure 8 is a conceptual diagram showing a first exemplary embodiment of an SSB burst configuration.

[0110] refer to Figure 8 , during transmission of SSB (e.g., SSB burst) in radio resources applying 120kHz SCS, the base station may send SSB in 8 consecutive time slots. During transmission of SSB in radio resources applying 240kHz SCS, the base station may send SSB in 16 consecutive time slots. In radio resources applying 120kHz SCS or 240kHz SCS, gaps for UL transmission may be configured.

[0111] The RMSI may be obtained by performing an operation for obtaining configuration information of a CORESET from an SS / PBCH block (e.g., PBCH), an operation for detecting a PDCCH based on the configuration information of the CORESET, an operation for obtaining scheduling information of a PDSCH from a PDCCH, and an operation for receiving RMSI on a PDSCH. The transmission resources of the PDCCH may be configured by the configuration information of the CORESET. The mapping mode of the RMSI CORESET mode may be defined as follows. The RMSI CORESET may be a CORESET for transmission and reception of RMSI.

[0112] Figure 9a is a conceptual diagram showing RMSI CORESET mapping mode #1 in a communication system, Figure 9b is a conceptual diagram showing RMSI CORESET mapping mode #2 in a communication system, and Fig.9c is a conceptual diagram showing RMSI CORESET mapping mode #3 in a communication system.

[0113] refer to Figures 9a to 9c , one RMSI CORESET mapping mode among RMSI CORESET mapping modes #1 to #3 may be used, and a detailed configuration according to the one RMSI CORESET mapping mode may be determined. In RMSI CORESET mapping mode #1, the SS / PBCH block, CORESET (i.e., RMSI CORESET), and PDSCH (i.e., RMSIPDSCH) may be configured in a TDM scheme. RMSI PDSCH may represent a PDSCH through which RMSI is transmitted. In RMSI CORESET mapping mode #2, the CORESET (i.e., RMSI CORESET) and PDSCH (i.e., RMSI PDSCH) may be configured in a TDM scheme, and the PDSCH (i.e., RMSI PDSCH) and SS / PBCH blocks may be configured in a frequency division multiplexing (FDM) scheme. In RMSI CORESET mapping mode #3, CORESET (ie, RMSI CORESET) and PDSCH (ie, RMSI PDSCH) may be configured in a TDM scheme, and may be multiplexed with SS / PBCH blocks in an FDM scheme.

[0114] In frequency bands of 6 GHz or lower, only RMSI CORESET mapping mode #1 may be used. In frequency bands of 6 GHz or higher, all RMSI CORESET mapping modes #1, #2, and #3 may be used. The configuration parameters of the SS / PBCH block may be different from the configuration parameters of the RMSICORESET and RMSI PDSCH. Here, the configuration parameter may be the subcarrier spacing. In RMSICORESET mapping mode #1, a combination of all configuration parameters may be used. In RMSI CORESET mapping mode #2, a combination of configuration parameters (120 kHz, 60 kHz) or (240 kHz, 120 kHz) may be used for the SS / PBCH block and the RMSI CORESET / PDSCH. In RMSI CORESET mapping mode #3, a combination of configuration parameters (120 kHz, 120 kHz) may be used for the SS / PBCH block and the RMSI CORESET / PDSCH.

[0115] A RMSI CORESET mapping mode may be selected from RMSI CORESET mapping modes #1 to #3 according to a combination of configuration parameters of the SS / PBCH block and configuration parameters of the RMSI CORESET / PDSCH. The configuration parameters of the RMSI CORESET may include Table A and Table B. Table A may indicate the number of resource blocks (RBs) of the RMSI CORESET, the number of symbols of the RMSI CORESET, and the offset between the RBs (e.g., the starting RB or the ending RB) of the SS / PBCH block and the RBs (e.g., the starting RB or the ending RB) of the RMSI CORESET. Table B may indicate the number of search space sets per time slot, the offset of the RMSI CORESET, and the OFDM symbol index in each of the RMSI CORESET mapping modes. Table B may indicate information for configuring the monitoring timing of the RMSI PDCCH. Each of Table A and Table B may consist of a plurality of sub-tables. For example, Table A may include sub-tables 13-1 to 13-8 defined in Technical Specification (TS) 38.213, and Table B may include sub-tables 13-9 to 13-13 defined in TS 38.213. The size of each of Table A and Table B may be 4 bits.

[0116] In the NR system, PDSCH may be mapped to the time domain according to PDSCH mapping type A or PDSCH mapping type B. PDSCH mapping types A and B may be defined as shown in Table 5 below.

[0117] [Table 5]

[0118] Type A (ie, PDSCH mapping type A) may be a slot-based transmission. When type A is used, the position of the starting symbol of the PDSCH may be configured as one of {0, 1, 2, 3}. When type A and a normal CP are used, the number of symbols constituting the PDSCH (eg, the duration of the PDSCH) may be configured as one of 3 to 14 within a range not exceeding the slot boundary. Type B (ie, PDSCH mapping type B) may be a non-slot-based transmission. When type B is used, the position of the starting symbol of the PDSCH may be configured as one of 0 to 12. When type B and a normal CP are used, the number of symbols constituting the PDSCH (eg, the duration of the PDSCH) may be configured as one of {2, 4, 7} within a range not exceeding the slot boundary. The DMRS (hereinafter referred to as "PDSCH DMRS") used to demodulate the PDSCH (eg, data) may be determined by the PDSCH mapping type (eg, type A or type B) and an ID indicating the length. The ID may be defined differently according to the PDSCH mapping type.

[0119] In addition, NR-Unlicensed (NR-U) is being discussed in the NR standardization meeting. The NR-U system can increase network capacity by improving the utilization of limited frequency resources. The NR-U system can support operations in unlicensed frequency bands (e.g., unlicensed spectrum).

[0120] In the NR-U system, the terminal can determine whether the signal is sent from the base station based on the discovery reference signal (DRS) received from the corresponding base station in the same manner as the general NR system. In the NR-U system in independent networking (SA) mode, the terminal can obtain synchronization information and / or system information based on DRS. In the NR-U system, DRS can be sent according to the provisions of the unlicensed band (e.g., transmission band, transmission power, transmission time, etc.). For example, according to the occupied channel bandwidth (OCB) provision, the signal can be configured and / or sent to occupy 80% of the total channel bandwidth (e.g., 20MHz).

[0121] In the NR-U system, a communication node (e.g., a base station, a terminal) may perform a pre-talk listen (LBT) process before sending a signal and / or channel for coexistence with another system. The signal may be a synchronization signal, a reference signal (e.g., DRS, DMRS, channel state information (CSI)-RS, phase tracking (PT)-RS, sounding reference signal (SRS)), etc. The channel may be a downlink channel, an uplink channel, a side link channel, etc. In an exemplary embodiment, the signal may represent "signal", "channel", or "signal and channel". The LBT process may be an operation for checking whether a signal is sent by another communication node. If it is determined by the LBT process that there is no transmission signal (e.g., when the LBT process is successful), the communication node may send a signal in an unlicensed band. If it is determined by the LBT process that there is a transmission signal (e.g., when the LBT fails), the communication node may not be able to send a signal in an unlicensed band. The communication node may perform an LBT process according to one of various categories before sending a signal. The category of LBT may vary depending on the type of transmission signal.

[0122] Depending on the presence and scheme of the idle channel assessment (CCA), the LBT operation can be performed in various ways. For example, a communication node (e.g., a terminal or a base station) may send a signal without performing CCA. The above operation may be referred to as the first category LBT. For another example, a communication node may perform CCA in a sensing period of fixed length, and send a signal immediately after the sensing section according to the result of the CCA. Specifically, the communication node may sense the channel in at least a portion of the sensing period (e.g., at least one sensing time slot), and if the received signal strength is equal to or less than a threshold value for more than a reference time (e.g., 4 μs), the channel may be determined to be in an idle state. The length of the sensing period may be fixed to one of 25 μs, 16 μs, and 9 μs. The above operation may be referred to as the second category LBT, and may also be referred to as "one-time LBT" because it includes one CCA.

[0123] The length of the sensing period may be variable. The communication node may perform CCA in an initial sensing period, and if the channel is determined to be in an idle state based on the result of the CCA, a signal may be sent immediately after the sensing period. On the other hand, if the channel is determined to be in a busy state based on the result of the CCA, the communication node may extend the sensing period and perform additional sensing operations in the extended sensing period. The sensing period may be extended by a random backoff scheme, and the length of the extended sensing period may be proportional to the random backoff value. The random backoff value may be determined within a contention window (CW). For example, if the random backoff value and the size of the CW are N, respectively. init and CW p , then N init Select 0 and CW p A random value between Ninit and CW p Each of N may be an integer. For example, the communication node may additionally init CCA is performed in a continuous postponement period, and if the channel is idle during all sensing time slots, the signal is sent immediately after the sensing period. In addition, if there is a difference between the completion time of the sensing operation (e.g., the time when the backoff counter value becomes 0) and the time when the signal will be sent, the communication node may perform a self-postponement operation and perform an additional sensing operation immediately before sending, and send a signal according to the result of the additional sensing operation. In the above-mentioned LBT operation, the initial sensing operation may be omitted. The above-mentioned operation may be referred to as a third category LBT or a fourth category LBT. For the third category LBT, the size of the CW may be fixed. For the fourth category LBT, the size of the CW may be adjusted according to a predefined process. For example, the size of the CW may be changed according to the type of signal to be sent, the channel access priority level (CAPC), the frequency adjustment, whether the previous transmission was successful (e.g., HARQ-ACK reception), etc.

[0124] In an NR communication system or an LTE communication system, the above-mentioned LBT operation scheme may be applied to a channel access procedure for a load-based device (LBE). For example, the first category LBT may be applied to a type 2C channel access procedure, the second category LBT may be applied to a type 2A channel access procedure and a type 2B channel access procedure, and the fourth category LBT may be applied to a type 1 channel access procedure. Instead of the first category LBT, the second category LBT, the third category LBT, and the fourth category LBT, they may be expressed as a type 1 channel access procedure or a type 2 channel access procedure. The above-mentioned LBT operation scheme may be applied to a channel access procedure for a frame-based device (FBE).

[0125] In addition, NR vehicle-to-everything (V2X) communication technology is being discussed in NR standardization meetings. NR V2X communication technology can be based on device-to-device (D2D) communication technology, supporting communication between vehicles, between vehicles and infrastructure, between vehicles and pedestrians, etc. Technology for reducing power consumption and improving reliability is being discussed for NR V2C communication.

[0126] NR V2X communication (e.g., side link communication) can be performed according to three transmission schemes (e.g., unicast scheme, broadcast scheme, multicast scheme). When using the unicast scheme, a PC5-RRC connection can be established between a first terminal (e.g., a transmitting terminal that sends data) and a second terminal (e.g., a receiving terminal that receives data), and the PC5-RRC connection can refer to a logical connection for pairing between a source ID of the first terminal and a destination ID of the second terminal. The first terminal can send data (e.g., side link data) to the second terminal. When using the broadcast scheme, the first terminal can send data to all terminals. When using the multicast scheme, the first terminal can send data to a group consisting of multiple terminals (e.g., a multicast group). In SL communication (e.g., SL-U communication), the transmitting terminal can represent a terminal that sends data, and the receiving terminal can represent a terminal that receives data.

[0127] When using a unicast scheme, the second terminal may send feedback information (e.g., confirmation (ACK) or negative ACK (NACK)) to the first terminal in response to data received from the first terminal. In the following exemplary embodiments, the feedback information may be referred to as "HARQ-ACK", "feedback signal", "physical side link feedback channel (PSFCH) signal", etc. When ACK is received from the second terminal, the first terminal may determine that the data has been successfully received at the second terminal. When NACK is received from the second terminal, the first terminal may determine that the second terminal has failed to receive the data. In this case, the first terminal may send additional information to the second terminal based on the HARQ scheme. Optionally, the first terminal can increase the probability of receiving the data at the second terminal by resending the same data to the second terminal.

[0128] When a broadcast scheme is used, a process for sending feedback information for data may not be performed. For example, system information may be sent in a broadcast scheme, and the terminal may not send feedback information for the system information to the base station. Therefore, the base station may not be able to identify whether the system information has been successfully received at the terminal. To solve this problem, the base station may periodically broadcast the system information.

[0129] When a multicast scheme is used, the process for sending feedback information for data may not be performed. For example, in the absence of a process for sending feedback information, necessary information may be periodically sent in a multicast scheme. However, when the number of candidates for terminals participating in communications based on a multicast scheme and / or the number of terminals participating in communications based on a multicast scheme is limited, and the data sent in the multicast scheme is data that should be received within a preconfigured time (e.g., data that is sensitive to delay), it may be necessary to also send feedback information in the multicast side link communication. The multicast side link communication may represent a side link communication performed in a multicast scheme. When the feedback information transmission process is performed in the multicast side link communication, data may be sent and received efficiently and reliably.

[0130] In multicast sidelink communication, two HARQ-ACK feedback schemes (i.e., the transmission process of feedback information) may be supported. When the number of receiving terminals in the sidelink group is large and service scenario 1 is supported, some receiving terminals belonging to a specific range within the sidelink group may send NACK through PSFCH when data reception fails. The scheme may be multicast HARQ-ACK feedback option 1. In service scenario 1, some receiving terminals belonging to a specific range may be allowed to perform reception in a best-effort manner instead of all receiving terminals in the sidelink group performing reception. Service scenario 1 may be an extended sensor scenario, wherein, in the extended sensor scenario, some receiving terminals belonging to a specific range need to receive the same sensor information from a transmitting terminal. In an exemplary embodiment, a transmitting terminal may refer to a terminal that sends data, and a receiving terminal may refer to a terminal that receives data.

[0131] When the number of receiving terminals in the side link group is limited and service scenario 2 is supported, each of all receiving terminals belonging to the side link group can report HARQ-ACK for data separately through a separate PSFCH. This scheme can be multicast HARQ-ACK feedback option 2. In service scenario 2, since PSFCH resources are sufficient, the transmitting terminal can monitor the HARQ-ACK feedback of all receiving terminals belonging to the side link group, and data reception can be guaranteed at all receiving terminals belonging to the side link group.

[0132] For example, in broadcast side link communication, data may be sent and received without a HARQ-ACK feedback process in unicast side link communication and multicast side link communication. In this case, in order to increase the probability of receiving data, the transmitting terminal may resend the data a preset number of times.

[0133] In all transmission schemes (e.g., unicast transmission, multicast transmission, and broadcast transmission), whether the HARQ-ACK feedback process is applied can be statically or semi-statically configured to the terminal through signaling (e.g., system information signaling, PC5-RRC signaling, UE-specific RRC signaling, control information signaling). In sidelink communication, HARQ-ACK feedback information can be sent on PSFCH. If the reception of PSSCH is successful, the receiving terminal can send an ACK for PSSCH (e.g., data) on PSFCH. If the reception of PSSCH fails, the receiving terminal can send a NACK for PSSCH (e.g., data) on PSFCH. PSFCH can be a channel for reporting ACK / NACK information (e.g., HARQ-ACK feedback) to the transmitting terminal. A resource area (e.g., PSFCH resource area) for PSFCH transmission (e.g., transmission of HARQ-ACK feedback) can be pre-configured in a specific resource pool. PSFCH (e.g., PSFCH resources or PSFH resource areas) can be periodically configured. The PSFCH period for the PSFCH resource may be k slots (eg, logical side link (SL) slots). k may be a natural number. For example, k may be 1, 2, or 4.

[0134] Fig.10 is a conceptual diagram showing a first exemplary embodiment of a configuration of a time slot configuring a PSFCH.

[0135] refer to Fig.10 , PSFCH (e.g., HARQ-ACK feedback) may be repeatedly transmitted in two symbols (e.g., two OFDM symbols) within a time slot (e.g., SL time slot). The first symbol of the two symbols for transmitting PSFCH may be used for automatic gain control (AGC) for correct PSFCH receive power level adjustment.

[0136] The PSFCH may be transmitted within a frequency resource region preconfigured by system information. In this case, the frequency resource region used for PSFCH transmission may be indicated (e.g., signaled) in the form of a bitmap within a resource pool. The receiving terminal may implicitly select the location of the frequency resource region used for PSFCH transmission based on the index of the time slot and subchannel in which the PSSCH is received. The receiving terminal may identify the number of resource blocks (RBs) and the number of multiplexed PSFCH resources based on the cyclic shift of the PSFCH sequence within the frequency resource region. The receiving terminal may implicitly select the PSFCH index of the PSFCH resource based on the source identifier (ID) and the member ID. The source ID may be a physical layer source ID. The source ID may be the ID of the transmitting terminal that has transmitted the PSSCH.

[0137] The member ID may be used in the groupcast HARQ-ACK feedback option 2. When the groupcast HARQ-ACK feedback option 2 is applied, each of all receiving terminals in the group may send HARQ-ACK feedback for SL data separately through a separate PSFCH (e.g., a PSFCH resource). In cases other than the above exemplary embodiments, the member ID may be set to 0.

[0138] Fig.11 is a conceptual diagram showing a first exemplary embodiment of a PSFCH for ACK / NACK transmission.

[0139] refer to Fig.11 , the transmission time of the PSFCH may be a preset time (eg, sl-MinTimeGapPSFCH ) can be the first time slot (e.g., PSFCH time slot) in which PSFCH transmission can be performed after receiving the PSSCH. The PSFCH time slot can be a time slot in which PSFCH can be sent and / or a time slot in which PSFCH is configured. The time required to process PSSCH after receiving PSSCH and the time required to prepare ACK / NACK (e.g., HARQ-ACK feedback) can be set according to whether the reception of PSSCH is successful. sl-MinTimeGapPSFCH . sl-MinTimeGapPSFCH It can be set to 2 or 3 time slots. A terminal (eg, a receiving terminal) can receive the PSSCH from the receiving time. sl-MinTimeGapPSFCH The PSFCH is transmitted in slot #n+12 after (e.g., 3 slots), where slot #n+12 is a slot capable of PSFCH transmission. n may be an integer greater than or equal to 0. In the present disclosure, the reception time may represent the reception start time and / or the reception end time, and the transmission time may represent the transmission start time and / or the transmission end time. The time may represent a moment and / or a duration.

[0140] The data reliability at the receiving terminal can be improved by appropriately adjusting the transmit power of the transmitting terminal according to the transmission environment. The interference to other terminals can be reduced by appropriately adjusting the transmit power of the transmitting terminal. Energy efficiency can be improved by reducing unnecessary transmit power. The power control scheme can be classified into an open-loop power control scheme and a closed-loop power control scheme. In the open-loop power control scheme, the transmitting terminal can determine the transmit power considering the configuration, the measured environment, etc. In the closed-loop power control scheme, the transmitting terminal can determine the transmit power based on the transmit power control (TPC) command received from the receiving terminal.

[0141] Due to various reasons including multipath fading channels, interference, etc., it may be difficult to predict the received signal strength at the receiving terminal. Therefore, the receiving terminal may adjust the received power level (e.g., received power range) by performing an automatic gain control (AGC) operation to prevent quantization errors of the received signal and maintain appropriate received power. In a communication system, the terminal may perform an AGC operation using a reference signal received from a base station. However, in sidelink communication (e.g., V2X communication), a reference signal may not be sent from a base station. That is, in sidelink communication, communication between terminals may be performed without a base station. Therefore, it may be difficult to perform an AGC operation in a sidelink communication. In sidelink communication, a transmitting terminal may first send a signal (e.g., a reference signal) to a receiving terminal before sending data, and the receiving terminal may adjust the received power range (e.g., received power level) by performing an AGC operation based on a signal received from the transmitting terminal. Thereafter, the transmitting terminal may send sidelink data to the receiving terminal. The signal used for the AGC operation may be a signal copied from a signal to be sent later or a signal pre-configured between terminals.

[0142] The time period required for ACG operation may be 15 μs. When a subcarrier spacing of 15 kHz is used in the NR system, the time period (e.g., length) of one symbol (e.g., OFDM symbol) may be 66.7 μs. When a subcarrier spacing of 30 kHz is used in the NR system, the time period of one symbol (e.g., OFDM symbol) may be 33.3 μs. In the following exemplary embodiments, a symbol may represent an OFDM symbol. That is, the time period of one symbol may be twice or more the time period required for ACG operation.

[0143] For sidelink communication, it may be necessary to send a data channel for data transmission and a control channel including scheduling information for data resource allocation. In sidelink communication, the data channel may be a physical sidelink shared channel (PSSCH), and the control channel may be a physical sidelink control channel (PSCCH). The data channel and the control channel may be multiplexed in a resource domain (e.g., a time and frequency resource domain).

[0144] Fig.12 is a conceptual diagram illustrating an exemplary embodiment of a method for multiplexing a control channel and a data channel in sidelink communication.

[0145] Reference Fig.12 , sidelink communication may support Option 1A, Option 1B, Option 2, and Option 3. When Option 1A and / or Option 1B are supported, the control channel and the data channel may be multiplexed in the time domain. When Option 2 is supported, the control channel and the data channel may be multiplexed in the frequency domain. When Option 3 is supported, the control channel and the data channel may be multiplexed in the time domain and the frequency domain. Sidelink communication may basically support Option 3.

[0146] In sidelink communication (e.g., NR-V2X sidelink communication), the basic unit of resource configuration may be a subchannel. A subchannel may be defined by time and frequency resources. For example, a subchannel may be composed of a plurality of symbols (e.g., OFDM symbols) in the time domain, and may be composed of a plurality of resource blocks (RBs) in the frequency domain. A subchannel may be referred to as an RB set. In a subchannel, a data channel and a control channel may be multiplexed based on Option 3.

[0147] In sidelink communication (e.g., NR-V2X sidelink communication), transmission resources may be allocated based on mode 1 or mode 2. When using mode 1, the base station may allocate sidelink resources for data transmission within a resource pool to a transmitting terminal, and the transmitting terminal may use the sidelink resources allocated by the base station to send data to a receiving terminal. Here, the transmitting terminal may be a terminal that sends data in the sidelink communication, and the receiving terminal may be a terminal that receives data in the sidelink communication.

[0148] When using mode 2, the transmitting terminal can autonomously select the side link resource to be used for data transmission by performing a resource sensing operation and / or a resource selection operation in the resource pool. The base station can configure a resource pool for mode 1 and a resource pool for mode 2 to the terminal. The resource pool for mode 1 and the resource pool for mode 2 can be configured separately. Optionally, a common resource pool can be configured for mode 1 and mode 2.

[0149] When using mode 1, the base station may schedule resources for sidelink data transmission for the transmitting terminal, and the transmitting terminal may send sidelink data to the receiving terminal by using the resources scheduled by the base station. Therefore, resource conflicts between terminals can be prevented. When using mode 2, the transmitting terminal may select any resource by performing a resource sensing operation and / or a resource selection operation, and may send sidelink data by using any selected resource. Since the above process is performed based on a separate resource sensing operation and / or resource selection operation for each transmitting terminal, conflicts between selected resources may occur.

[0150] Fig.13 is a conceptual diagram illustrating a first exemplary embodiment of a resource selection operation.

[0151] refer to Fig.13 , the terminal (e.g., the transmitting terminal) may perform a resource sensing operation within the sensing window, and may perform a resource selection operation on the sensed resources (e.g., candidate resources) within the selection window. When the resource selection operation is triggered at time n, the terminal may select a resource based on the resource selected in the sensing window (e.g., from time n-T0 to time nT proc,0 Based on the sensing results within the time period (for example, from time n+T1 to time n+T2), appropriate resources are selected within the selection window (for example, the time period from time n+T1 to time n+T2).

[0152] Based on the result of the resource sensing operation, the terminal may exclude candidate resources that do not meet the conditions within the selection window. In other words, the terminal may determine the remaining candidate resources other than unsuitable candidate resources from all candidate resources. When the ratio of the remaining candidate resources among all resources within the selection window is less than the reference ratio, the terminal may relax the conditions for excluding candidate resources. For example, the terminal may increase the reference signal received power (RSRP) threshold used as a condition for excluding candidate resources by 3dB. Thereafter, the terminal may perform the resource selection operation again. For each priority level, the reference ratio may be preset to one of 20%, 35%, or 50%. When the ratio of the remaining candidate resources is greater than or equal to the reference ratio, the terminal may randomly select the final resource to be used for SL transmission from among the remaining candidate resources. The terminal may perform SL transmission using the final resource.

[0153] Fig.14 is a conceptual diagram illustrating a first exemplary embodiment of a resource reselection operation.

[0154] refer to Fig.14 After the resource selection operation, the terminal may perform a resource reselection operation by considering non-periodic data transmission, etc. Fig.13 After the operation shown, the terminal may perform a resource reselection operation by additionally considering the result of sensing at time m-T3 before the actual SL transmission. The resource reselection operation may be performed within the reselection window. The terminal may further determine the suitability of the resources reserved at time m. When it is determined that the resources reserved at time m are suitable, the terminal may perform SL transmission using the reserved resources. When it is determined that the resources reserved at time m are not suitable, the terminal may reselect the resources for SL transmission and perform SL transmission using the reselected resources.

[0155] When an independent SL carrier is not configured for SL communication, some of the UL resources in the UL resources may be configured as SL resources through the SL resource pool configuration process. The bitmap may be repeatedly applied to the remaining time slots among the time slots within a specific time period except for the time slots that are not configured with at least X or more UL symbols and the time slots for transmitting the side link (S)-SSB. X may be a natural number. The bitmap may indicate the time slots used as SL resources. For example, the time slots corresponding to the bits set to 1 among the bits in the bitmap may be used as SL resources.

[0156] It may be assumed that a 15kHz subcarrier spacing (SCS) is applied and X or more UL symbols are configured in all time slots. When 10240 time slots are available in a direct frame number (DFN), the transmission period of S-SSB is 160ms, and 2 time slots are used for S-SSB transmission in each S-SSB transmission period, the number of time slots used for S-SSB transmission in DFN may be 128. The bitmap for configuring SL time resources may include 10 bits. When a bitmap (e.g., a bitmap including 10 bits) is repeatedly applied to the remaining 10112 time slots other than the 128 time slots used for S-SSB transmission among the 10240 time slots, there may be two time slots (e.g., reserved time slots) to which the bitmap is not applied. It may be necessary to exclude these two reserved time slots. When these two reserved time slots are excluded from the 10112 time slots, 10110 time slots may be reserved. A bitmap (e.g., a bitmap including 10 bits) may be repeatedly applied 1011 times to 10110 time slots. When the bitmap is set to "1111000000" and the time slots corresponding to the bits set to 1 are used as SL resources, 4044 time slots may be configured as SL resources within the DFN. In other words, 4044 time slots out of 10240 time slots may be used for SL communication by configuring an SL resource pool.

[0157] The side link communication system supporting version 16 may be designed for terminals with no restrictions on battery capacity (e.g., vehicle-mounted terminals, vehicle UE (V-UE)). Therefore, power saving may not be considered too much in the resource sensing / selection operation for such terminals. However, in order to perform side link communication with terminals with limited battery capacity (e.g., terminals carried by pedestrians, terminals mounted on bicycles, terminals mounted on motorcycles, pedestrian UE (P-UE)) in the side link communication system supporting version 17, a power saving method will be required. In the present disclosure, "V-UE" may refer to a terminal with no significant restrictions on battery capacity, "P-UE" may refer to a terminal with restrictions on battery capacity, and "resource sensing / selection operation" may refer to a resource sensing operation and / or a resource selection operation. The resource sensing operation may refer to a partial sensing operation or a full sensing operation. The resource selection operation may refer to a random selection operation. In addition, in the present disclosure, "the operation of the terminal" may be interpreted as "the operation of the V-UE" and / or "the operation of the P-UE".

[0158] In order to save power in LTE V2X, partial sensing operation and / or random selection operation are introduced. When partial sensing operation is supported, the terminal can perform resource sensing operation in a partial period within the sensing window instead of the entire period, and can select resources based on the results of the partial sensing operation. According to such operation, the power consumption of the terminal can be reduced.

[0159] In Release 14 LTE V2X, only periodic data transmission and reception operations are feasible. In Release 14 LTE V2X, the terminal may arbitrarily select a candidate time slot within a resource selection period (e.g., a selection window) considering a preset minimum number, and perform partial sensing operations considering a period of k×100 ms. k may be signaled via a bitmap (e.g., a bitmap including 10 bits). k may be determined based on the position of the bits included in the bitmap. For example, the 10 bits included in the bitmap may correspond to values ​​1 to 10 starting from the MSB, respectively, and the periodicity may be determined based on the value corresponding to the bit set to 1. The value corresponding to the bit set to 1 may be k.

[0160] When the MSB is set to 1 in the bitmap, k may be 1. In this case, the terminal may consider a period of 100ms (=1×100ms) to perform a partial sensing operation. When the bit next to the MSB in the bitmap is set to 1, k may be 2. In this case, the terminal may consider a period of 200ms (=2×100ms) to perform a partial sensing operation. When the LSB is set to 1 in the bitmap, k may be 10. In this case, the terminal may consider a period of 1000ms (=10×100ms) to perform a partial sensing operation.

[0161] In Release 14 LTE V2X, the period (e.g., the period of some sensing operations) may be set to 20ms or 50ms. Periods of 20ms or 50ms may not be supported in the resource pool of the P-UE. In the NR communication system, in addition to {0, 100ms, 200ms, ..., 1000ms}, shorter periods may also be supported. The short period may be {1ms, 2ms, ..., 99ms}. Up to 16 periods may be selected from the resource pool, and the selected period may be preconfigured to the terminal. The terminal may use one or more of the configured periods to perform resource sensing operations and / or resource (re)selection operations. When a random selection operation is supported, the terminal may randomly select resources without performing a resource sensing operation. Optionally, the random selection operation may be performed together with the resource sensing operation. For example, the terminal may determine the resources by performing a resource sensing operation, and may select the resources by performing a random selection operation within the determined resources.

[0162] In LTE V2X supporting Release 14, a resource pool that can perform a partial sensing operation and / or a random selection operation can be configured independently of a resource pool that can perform a full sensing operation. A resource pool that can perform a random selection operation, a resource pool that can perform a partial sensing operation, and a resource pool that can perform a full sensing operation can be configured separately. In other words, a random selection operation, a partial sensing operation, or both a random selection operation and a partial sensing operation can be configured for each resource pool. When both a random selection operation and a partial sensing operation are configured for a resource pool, the terminal can select one operation from the random selection operation and the partial sensing operation, select resources by performing the selected operation, and perform SL communication using the selected resources.

[0163] In LTE V2X supporting Release 14, side link (SL) data may be periodically sent based on a broadcast scheme. In an NR communication system, SL data may be sent based on a broadcast scheme, a multicast scheme, a groupcast scheme, or a unicast scheme. In addition, in an NR communication system, SL data may be sent periodically or non-periodically. A transmitting terminal may send SL data to a receiving terminal, and the receiving terminal may send HARQ feedback (e.g., acknowledgment (ACK) or negative ACK (NACK)) for the SL data to the transmitting terminal on the PSFCH. In the present disclosure, a transmitting terminal may refer to a terminal that sends SL data, and a receiving terminal may refer to a terminal that receives SL data.

[0164] Terminals with reduced capabilities (hereinafter referred to as "RedCap terminals") may operate in specific usage environments. The capabilities of RedCap terminals may be lower than those of New Radio (NR) ordinary terminals, and may be higher than those of LTE Machine Type Communication (LTE-MTC) terminals, narrowband (NB) Internet of Things (IoT) terminals, and low power wide area (LPWA) terminals. For example, there may be terminals that require high data rates and non-high latency conditions (e.g., surveillance cameras) and / or terminals that require non-high data rates, high latency conditions, and high reliability (e.g., wearable devices). In order to support the above terminals, the maximum carrier bandwidth in FR1 may be reduced from 100MHz to 20MHz, and the maximum carrier bandwidth in FR2 may be reduced from 400MHz to 100MHz. The number of receiving antennas of a RedCap terminal may be less than the number of receiving antennas of an NR ordinary terminal. When the carrier bandwidth and the number of receiving antennas are reduced, the reception performance at the RedCap terminal may be reduced, and therefore, the coverage of the RedCap terminal may be reduced.

[0165] A communication system (e.g., an NR system) may operate in a frequency band higher than the 52.6 GHz band. As the frequency of the frequency band in which the communication system operates increases, frequency offset error and phase noise may increase. The use of a large SCS may be necessary for robust operation in such an environment. In the FR2 band, 60 kHz SCS and / or 120 kHz SCS may be supported, and 480 kHz SCS and / or 960 kHz SCS may be additionally supported. In addition, physical layer signals and channels and physical layer processes may need to be designed according to the new SCS. Regarding the initial access process, 120 kHz SSB and / or 240 kHz SSB may be supported in the FR2 band, and 480 kHz SSB and / or 960 kHz SSB may be additionally supported. Here, 120 kHz SSB may refer to an SSB sent in a radio resource to which 120 kHz SCS is applied, and 240 kHz SSB may refer to an SSB sent in a radio resource to which 240 kHz SCS is applied. A method for configuring an initial BWP and an SSB burst set mode for supporting a new SCS may be required.

[0166] In Release 18, technologies may be discussed for: carrier aggregation (CA) for increasing data transmission rates on the sidelink, supporting operation in unlicensed spectrum, performance improvements in FR2 licensed spectrum, and / or co-channel coexistence between LTE SL and NR SL.

[0167] For side link (SL) communication in an unlicensed band (e.g., unlicensed spectrum), as in the NR-U system, the transmission band, transmission power, and / or transmission time according to the use of the unlicensed band shall comply with regulations. The communication node may perform an LBT operation before SL communication to identify the occupancy state of the channel. The LBT operation and process for channel access applicable to SL communication may preferably be defined in the same manner as the NR-U system.

[0168] Contention Window (CW) Adjustment The channel access process in the unlicensed band can be classified into a type 1 channel access process and a type 2 channel access process. In the case of a type 1 channel access process, if it is determined that the channel is occupied by another communication node while performing a sensing operation to identify the channel occupancy state, the communication node can extend the sensing period within the CW by using a random backoff scheme, and perform additional sensing operations in the extended sensing period. The size of the CW (i.e., the CW size) can be adjusted based on the HARQ-ACK / NACK feedback information. For example, when an ACK for data is received, the communication node can set the CW size to the minimum value among the allowed values. When a NACK for data is received, the communication node can set the CW size to the next value greater than the current value among the allowed values. Since the HARQ-ACK / NACK feedback operation is supported in the SL unicast communication, the above operation can be applied. The above operation may not be directly applied to SL multicast communication and / or SL broadcast communication. SL unicast communication may represent SL communication performed based on a unicast scheme. SL groupcast communication may represent SL communication performed based on a multicast scheme. SL broadcast communication may represent SL communication performed based on a broadcast scheme.

[0169] In the case of groupcast HARQ ACK / NACK feedback option 1, each terminal in the group may send NACK through a common PSFCH resource only when data reception fails. If data reception is successful, the terminals in the group may not send ACK (e.g., PSFCH). The above-mentioned HARQ ACK / NACK feedback scheme may be a NACK-only scheme. In this case, the transmitting terminal (e.g., the terminal that sends data) cannot know which terminal in the group has not received the data. When all terminals in the group successfully receive data or when all terminals in the group do not receive the SCI of the transmitting terminal, a situation where NACK is not received may occur. If NACK is not received, the transmitting terminal may not be able to distinguish between a situation when all terminals in the group successfully receive data and a situation when all terminals in the group do not receive the SCI of the transmitting terminal. Generally, in the case of groupcast HARQ ACK / NACK feedback option 1, only terminals within a specific range may perform NACK feedback. If NACK feedback is not detected, the probability that all terminals within a specific range successfully receive data may be higher than the probability that all terminals within a specific range do not receive SCI. Therefore, if NACK feedback is not detected, the transmitting terminal may determine that the HARQ ACK / NACK feedback for the data is ACK, and set the CW size to the minimum value among the allowed values.

[0170] In the case of multicast HARQ ACK / NACK feedback option 1, the condition that only terminals within a specific range perform NACK feedback may not be applied. In this case, even if NACK feedback is not detected, it may be difficult to determine that the probability that all terminals in the group successfully receive data is higher than the probability that all terminals in the group do not receive SCI. Optionally, if NACK feedback is not detected, the transmitting terminal may maintain the current CW size (e.g., the latest CW size). If NACK feedback is detected, the transmitting terminal may set the CW size to a value that is one step larger than the current CW size in the allowed value, similar to the unicast scheme. In the present disclosure, the value that is one step larger than the CW size may be the next value larger than the CW size.

[0171] The above method can also be applied similarly even when a conflict indicator (e.g., a conflict prediction indicator) is sent instead of NACK feedback or in addition to NACK feedback. Optionally, a fixed CW size can be applied, and the fixed CW size can be set according to the priority of the sidelink transmission data or CAPC (e.g., CAPC value). For example, the fixed CW size can be set differently according to the priority of the sidelink transmission data or CAPC. In the present disclosure, CAPC can represent a CAPC value or a CAPC level. When the CAPC is smaller, the CAPC can have a higher priority, and when the CAPC is larger, the CAPC can have a lower priority.

[0172] For example, if the data has a high priority or a small CAPC value, the terminal may set a small CW size. If the data has a low priority or a large CAPC value, the terminal may set a large CW size. A fixed CW size considering a priority or CAPC value may be pre-set or defined through a signaling message (e.g., system information, UE-specific RRC message, PC5-RRC message, high-layer signaling message, MAC CE, and / or control information (DCI or SCI)). A fixed CW size considering a priority or CAPC value may be set differently for each resource pool.

[0173] In the case of multicast HARQ ACK / NACK feedback option 2, each terminal in the group can send ACK / NACK feedback information through each PSFCH resource. Therefore, the transmitting terminal can identify whether the data reception at each terminal (e.g., each receiving terminal) is successful. In the present disclosure, the transmitting terminal may refer to a terminal that sends data, and the receiving terminal may refer to a terminal that receives data. When using multicast HARQ ACK / NACK feedback option 2, similar to the unicast scheme, the transmitting terminal can perform CW size adjustment. However, since the transmitting terminal receives multiple ACK / NACK feedbacks according to one data transmission, it may be necessary to additionally consider multiple ACK / NACK feedbacks when adjusting the CW size.

[0174] For example, when multiple ACK / NACK feedbacks are received and one or more of the multiple ACK / NACK feedbacks are ACKs, the transmitting terminal may set the CW size to the minimum value among the allowable values. Optionally, when the number of ACKs in the multiple ACK / NACK feedbacks is equal to or greater than a specific value N, the transmitting terminal may set the CW size to the minimum value among the allowable values. N may be a natural number. When the above conditions are not met, the transmitting terminal may set the CW size to a value in the allowable value that is one step larger than the current CW size. Optionally, when the above conditions are not met, the transmitting terminal may maintain the current CW size.

[0175] Optionally, in the case where all of the multiple ACK / NACK feedbacks are NACK, the transmitting terminal may also set the CW size to a value in the allowed value that is one step larger than the current CW size. Optionally, when the number of NACKs in the multiple ACK / NACK feedbacks is equal to or greater than a specific value M, the transmitting terminal may set the CW size to a value in the allowed value that is one step larger than the current CW size. M may be a natural number. When the above conditions are not met, the transmitting terminal may set the CW size to the minimum value in the allowed value. Optionally, when the above conditions are not met, the transmitting terminal may maintain the current CW size.

[0176] Instead of N and M, a ratio threshold (%) for ACK or NACK in multiple ACK / NACK feedbacks may be applied. The ACK ratio threshold and the NACK ratio threshold may be considered separately. For example, when the CW size is set to a minimum value, an ACK-related condition (e.g., an ACK ratio threshold) may be applied. When the CW size is set to a value one step larger, a NACK-related condition (e.g., a NACK ratio threshold) may be applied. When both the ACK-related condition and the NACK-related condition are not met, the transmitting terminal may maintain the current CW size. Multiple ACK / NACK feedbacks may be defined by the number of ACK / NACK feedbacks actually received from the receiving terminal.

[0177] In the case of groupcast HARQ ACK / NACK feedback option 2, the number of ACK / NACK feedbacks to be fed back can be predicted in advance, and thus multiple ACK / NACK feedbacks can be defined by the predicted number of ACK / NACK feedbacks. When (the total number of members in the group - 1) is defined as the predicted number of ACK / NACK feedbacks, the situation where there is no HARQ ACK / NACK feedback due to the terminal in the group not receiving the SCI can be considered as NACK. All members in the group can be all terminals in the group or all receiving terminals. N, M, ACK ratio threshold (%), NACK ratio threshold (%) and / or (ACK+NACK) ratio threshold (%) can be pre-set or defined by a signaling message (e.g., system information, UE-specific RRC message, PC5-RRC message, high-layer signaling message, MAC CE and / or control information (e.g., DCI or SCI)).

[0178] N, M, ACK ratio threshold (%), NACK ratio threshold (%) and / or (ACK+NACK) ratio threshold (%) are set differently for each resource pool. When one or more ACK / NACK feedbacks are ACK (hereinafter referred to as "Alt 1"), or when the number of ACKs in multiple ACK / NACK feedbacks is greater than or equal to the ACK ratio threshold (hereinafter referred to as "Alt 2"), the transmitting terminal may apply a method of setting the CW size to the minimum value among the allowed values ​​according to the situation. For example, if the ACK ratio threshold is not set, the transmitting terminal may adjust the CW size according to Alt 1. If the ACK ratio threshold is set, the transmitting terminal may adjust the CW size according to Alt 2. If the corresponding condition is not met in Alt 1 or Alt 2, the transmitting terminal may set the CW size to a value that is one step larger than the allowed value. Optionally, if the corresponding condition is not met in Alt 1 or Alt 2, the transmitting terminal may maintain the CW size.

[0179] The CW size adjustment method based on the ACK ratio and / or the ACK ratio threshold may be applied identically or similarly to the CW size adjustment method based on the NACK ratio and / or the NACK ratio threshold. The CW size adjustment method based on the NACK ratio and / or the NACK ratio threshold may be applied identically or similarly to the CW size adjustment method based on the ACK ratio and / or the ACK ratio threshold.

[0180] In the present disclosure, HARQ-ACK information, HARQ-ACK feedback, HARQ ACK / NACK information, HARQ ACK / NACK feedback, ACK / NACK information, ACK / NACK feedback, HARQ response, HARQ-ACK response and / or HARQ ACK / NACK response may be used with the same meaning.

[0181] The HARQ ACK / NACK feedback function may not be supported in the broadcast scheme. Therefore, the method for CW size adjustment in the unicast scheme and / or the multicast scheme may not be applied to the broadcast scheme. In the unicast method and / or the multicast scheme, the HARQ ACK / NACK feedback function may be disabled. Considering the case where the HARQ ACK / NACK feedback function is disabled, a method for CW size adjustment may be required. In SL communication, the HARQ ACK / NACK feedback function may be disabled according to two methods. In the first method, PSFCH resources may not be configured in the resource pool, in which case the HARQ ACK / NACK feedback function for all communication schemes (e.g., unicast scheme, multicast scheme) may not be supported in the resource pool. In the second method, PSFCH resources may be configured in the resource pool, and the HARQ ACK / NACK feedback function may be disabled through the second-level SCI.

[0182] In SL broadcast communication, SL unicast communication that does not support the HARQ ACK / NACK feedback function, and / or SL multicast communication that does not support the HARQ ACK / NACK feedback function, a fixed CW size may be preferably used. Here, "HARQ ACK / NACK feedback function is not supported" may mean that PSFCH resources are not configured in the corresponding resource pool. The fixed CW size may be set differently according to the priority or CAPC of the SL data. In other words, the fixed CW size may be set independently according to the priority or CAPC of the SL data. When the SL data has a high priority or a small CAPC, a small CW size may be used. When the SL data has a low priority or a large CAPC, a large CW size may be used.

[0183] The fixed CW size considering priority or CAPC may be set based on at least one of system information, UE-specific RRC message, PC5-RRC message, MAC CE, or control information (e.g., DCI, SCI). Optionally, the fixed CW size considering priority or CAPC may be predefined in the technical specification. The fixed CW size may be set independently for each resource pool. For example, the fixed CW size may be set differently for each resource pool.

[0184] When PSFCH resources are configured in the resource pool and the HARQ ACK / NACK feedback function is disabled by the second-level SCI, it may be preferred not to change the CW size. In other words, it may be preferred to keep the CW size at the previous CW size (e.g., the latest CW size). When the second-level SCI indicates that the HARQ ACK / NACK feedback function is disabled during the transmission of data, the previous CW size (e.g., the latest CW size) may be used during the (re)transmission of data. When the HARQ ACK / NACK feedback function is enabled, the CW size may be adjusted based on the ACK and / or NACK for the data.

[0185] Optionally, when the HARQ ACK / NACK feedback function is disabled, a fixed CW size or a previous CW size (e.g., the latest CW size) set according to the priority may be used. In the present disclosure, an allowed value and / or allowed range for CW size adjustment may be configured based on at least one of system information, UE-specific RRC message, PC5-RRC message, MAC CE, or control information (e.g., DCI, SCI). Optionally, an allowed value and / or allowed range for CW size adjustment may be predefined in a technical specification. An allowed value and / or allowed range for CW size adjustment may be independently configured for each resource pool. For example, an allowed value and / or allowed range for CW size adjustment may be configured differently for each resource pool.

[0186] After the CW size is set to the maximum CW size among the allowed values, even when it is necessary to adjust to a value one step larger than the maximum CW size, it is preferable to maintain the maximum CW size. If the maximum CW size is used continuously, a delay in data transmission may occur. Therefore, if the maximum CW size is used K times continuously, it is preferable to adjust the maximum CW size to the minimum CW size among the allowed values. K may be set differently according to the priority (e.g., the priority of the data) and / or the CAPC. In other words, K may be set independently according to the priority (e.g., the priority of the data) and / or the CAPC. K may be a natural number. K for a high priority may be set to a small value within the allowed range. K for a low priority may be set to a high value within the allowed range.

[0187] In order to adjust the CW size, it may be necessary to define a reference duration for determining valid HARQ ACK / NACK feedback. The reference duration may consist of consecutive physical time slots or logical time slots. Some physical time slots may be configured as logical time slots. Therefore, even when the reference duration consists of logical time slots, the time slots included in the reference duration may not be consecutive. When the reference duration consists of physical time slots, some physical time slots may be configured as logical time slots for SL communication. Therefore, a sufficient number of logical time slots may not be configured. Preferably, the reference duration consists of physical time slots, from which a minimum number of logical time slots can be obtained. For example, the reference duration may include a minimum number of physical time slots, which includes at least X logical time slots. X may be a natural number.

[0188] In a SL system (e.g., an NRSL system), a logical time slot may be periodically configured by bitmap signaling based on a physical time slot. Therefore, the reference duration may be configured in consideration of bitmap signaling (e.g., signaling of a bitmap pattern) and / or SSB periodicity. X may be set to an appropriate value in consideration of a bitmap (e.g., a bitmap pattern) used to configure the logical time slot. For example, X may be set by signaling (e.g., SI signaling, RRC signaling, MAC signaling, and / or PHY signaling). Optionally, X may be predefined in a technical specification. X may be set for each resource pool.

[0189] Depending on the bitmap pattern, the number of physical time slots required to obtain at least X logical time slots may be too large. In view of the above, a maximum number of physical time slots (e.g., Y) may be set. The number of physical time slots used to obtain at least X logical time slots may not exceed Y. If X logical time slots are not obtained within Y physical time slots, the duration including Y physical time slots may not be considered as a reference duration. Y may be a natural number.

[0190] The reference duration may be defined in different ways. For example, the reference duration may be defined as the duration starting from the channel occupancy time (COT) initiated by the terminal sending the PSSCH to the end of the first time slot in which at least one PSSCH with HARQ ACK / NACK feedback enabled is sent. In this case, the scheme for HARQ ACK / NACK feedback may be an ACK / NACK feedback scheme and / or a NACK-only feedback scheme. The ACK / NACK feedback scheme may be an ACK / NACK feedback scheme in SL unicast communication or a multicast HARQ-ACK feedback option 2. The NACK-only feedback scheme may be a multicast HARQ-ACK feedback option 1.

[0191] If there is no PSSCH transmission with HARQ ACK / NACK feedback enabled within the COT, the terminal may determine that the condition of the reference duration is not met and the reference duration may not be used. Optionally, if there is no PSSCH transmission with HARQ ACK / NACK feedback enabled within the COT, the reference duration may be defined as a duration from the start of the COT to the end of the COT. Determinations related to CW size adjustment may be performed within the reference duration. If the condition of the reference duration is not met (for example, if the reference duration is not configured), the terminal may maintain the latest CW size, set the CW size to the next CW size that is one step larger than the current CW size, or set the CW size to a CW size preset based on priority.

[0192] If the condition of the reference duration is not met, the latest CW size may be maintained. In the above case, if the latest CW size is small and the latest CW size is used continuously, the fair channel access process between the terminals may not be performed. Therefore, in the case where the latest CW size is maintained due to the condition of the reference duration not being met, the latest CW size may be maintained K times. After the latest CW size is maintained K times, the latest CW size may be preferably set to the next CW size with a larger step size. After the maximum CW size is used K times, the maximum CW size may be reset to the minimum CW size. K may be a natural number. K may be preset. For example, K may be set to the terminal by signaling (e.g., high-layer signaling). The above configuration may be applied only to a resource pool for which PSFCH resources are not configured. When SL transmission is not associated with HARQ ACK / NACK feedback, the above configuration may be applied regardless of whether the PSFCH resources are configured. When the HARQ ACK / NACK feedback function is disabled, the above exemplary embodiment (e.g., a method for adjusting the CW size in consideration of K) may be applied.

[0193] In the channel access process of the unlicensed band, the COT duration after the sensing period and / or channel occupancy may vary according to the CAPC. The lower the CAPC, the higher the probability of success of the channel access process, and the shorter the COT duration occupied by the channel access process. Therefore, it is preferable to set a low CAPC for high priority transmission. In SL unlicensed (U) communication, it may be necessary to set an appropriate CAPC according to the priority of the SL transmission. An appropriate CAPC may be set according to the priority of the data (e.g., SL data) in the SL transmission (e.g., PSCCH transmission and / or PSSCH transmission).

[0194] The mapping relationship between the priority of SL data and the CAPC may be configured in the terminal through signaling (e.g., system information (SI) signaling, RRC signaling (e.g., UE-specific RRC signaling), MAC signaling, PHY signaling). Optionally, the mapping relationship between the priority of SL data and the CAPC may be defined in a technical specification. Optionally, the priority and CAPC for SL transmission may be set in the terminal through signaling (e.g., high-layer signaling) before performing SL transmission.

[0195] The PSFCH used to send HARQ ACK / NACK feedback for data may be a channel that carries important information for determining whether to perform a retransmission process. The CAPC (e.g., CAPC level) for PSFCH transmission may preferably be set to 1. Optionally, the CAPC of the PSSCH transmission corresponding to the PSFCH transmission may be used for the PSFCH transmission. The CAPCs of multiple PSFCH transmissions corresponding to multiple PSSCH transmissions may be different. In the above case, the minimum CAPC or the maximum CAPC among the CAPCs may be set to a common CAPC, and the common CAPC may be applied to multiple PSFCH transmissions. Optionally, the terminal may practicably select an arbitrary CAPC and use the arbitrary CAPC for PSFCH transmission.

[0196] The S-SSB used for time and / or frequency synchronization can be an important signal for synchronization between terminals in SL communication. The CAPC for the S-SSB (e.g., CAPC level) may preferably be set to 1. Optionally, the CAPC for the S-SSB may be set according to the priority of the terminal (e.g., synchronization reference (SyncRef) terminal, synchronization terminal) that sends the S-SSB. The CAPC for the S-SSB may be set to the terminal through signaling (e.g., SI signaling, RRC signaling (e.g., UE-specific RRC signaling), MAC signaling, and / or PHY signaling). Optionally, the CAPC for the S-SSB may be defined in the technical specification. Optionally, the terminal (e.g., synchronization reference terminal, synchronization terminal) may practicably select an arbitrary CAPC and use the arbitrary CAPC for S-SSB transmission.

[0197] COT Sharing In unlicensed band communication (e.g., NR-U communication, SL-U communication), a first communication node (e.g., a base station, a terminal) may occupy a channel within a specific time period by performing an LBT process. The time period occupied by the first communication node may be a COT. The first communication node may acquire the COT by performing an LBT process and share the COT with the second communication node. The operation may be a COT sharing operation. The second communication node may send a signal during the duration of the shared COT. In this case, the second communication node may increase the probability of signal transmission within the shared COT by performing a type 2 channel access process instead of a type 1 channel access process. The first communication node (e.g., a base station or a terminal) may acquire the COT and notify the second communication node (e.g., a terminal or a base station) of information about the acquired COT through signaling.

[0198] In SL-U communication, the first terminal may acquire the COT and share the acquired COT with the second terminal. The first terminal may send information about the acquired COT to the second terminal through signaling (e.g., RRC signaling (e.g., PC5-RRC signaling), MAC CE signaling, PHY signaling). The PHY signaling may be a transmission of the first level SCI and / or the second level SCI. The information about the acquired COT may be sent from the first terminal to one or more terminals.

[0199] In unicast SL communication, the first terminal can acquire COT by performing an LBT process (e.g., a type 1 channel access process). When the LBT process is successful, the COT can be acquired. The first terminal can perform SL communication (e.g., unicast SL communication) with the second terminal within the acquired COT. The first terminal can send information about the remaining COT after SL communication with the second terminal. The information about the remaining COT can be sent to the second terminal and / or the third terminal, and the remaining COT can be shared with the second terminal and / or the third terminal. The second terminal that is the transmission target of the first terminal or a terminal other than the second terminal (e.g., the third terminal) can perform SL communication within the COT shared by the first terminal. In this case, it is preferred that the second terminal performs SL communication with the first terminal within the COT shared by the first terminal. It is preferred that the third terminal performs SL communication with the first terminal within the COT shared by the first terminal.

[0200] In SL communication based on COT sharing, the first terminal may refer to the terminal that initiates the COT, the second terminal may refer to the terminal that performs SL communication with the first terminal within the COT initiated by the first terminal, the third terminal may refer to the terminal that does not perform SL communication with the first terminal within the COT initiated by the first terminal, and the COT initiated by the first terminal may be shared with the second terminal and / or the third terminal.

[0201] If the terminal using the shared COT (hereinafter referred to as a "shared terminal" or "responding terminal") is a second terminal, information about the shared terminal may be indicated by a destination identifier (ID) (e.g., the ID of the second terminal) included in the SCI sent by the first terminal. In this case, additional information indicating the shared terminal may not be required. If the shared terminal is a third terminal, information about the shared terminal (e.g., the ID of the third terminal) may preferably be included in the COT shared information (e.g., information about the remaining COT). When the remaining COT is shared with multiple third terminals, the COT shared information (e.g., information about the remaining COT) may include the IDs of multiple third terminals. In this case, the shared terminal may be indicated according to the order of the IDs included in the COT shared information. The COT shared information may include a source ID and a destination ID. In this case, the source ID may be the source ID of the second terminal or the third terminal, and the destination ID may be the destination ID of the first terminal. In addition, the COT shared information may include a propagation type indicator, and the propagation type indicator may indicate that SL unicast communication, SL multicast communication, or SL broadcast communication is performed. In other words, the propagation type indicator may indicate the propagation type of SL communication.

[0202] Alternatively, the third terminal may be limited to terminals located within a specific range. In this case, the COT shared information may include information about a reference to a specific range, rather than information about the ID of the third terminal. The information about the reference to a specific range may be information about the communication range. The communication range may be determined based on the distance between the first terminal and the third terminal and / or the distance between the second terminal and the third terminal. The distance between the first terminal and the third terminal may be calculated based on the area ID included in the SCI (e.g., the first level SCI and / or the second level SCI). The area ID of the first terminal may be included in the COT information (e.g., COT shared information) instead of the SCI. In this case, the distance between the first terminal and the third terminal may be calculated based on the area ID included in the COT information. The area ID of the second terminal may be included in the COT information. In this case, the distance between the second terminal and the third terminal may be calculated based on the area ID included in the COT information.

[0203] Whether the shared terminal is the second terminal or the third terminal may be determined based on whether the COT information includes information about the ID of the third terminal and / or information about a reference for selecting the third terminal (e.g., information about the communication range). For example, when the COT information does not include information about the ID of the third terminal and / or information about a reference for selecting the third terminal, the second terminal may be a shared terminal. When the COT information includes information about the ID of the third terminal and / or information about a reference for selecting the third terminal, the third terminal may be a shared terminal. In this case, the second terminal and the third terminal may be shared terminals.

[0204] An additional indication (e.g., a separate indicator) may notify whether the COT information includes information about a third terminal (e.g., information about the ID of the third terminal and / or information about a reference for selecting the third terminal). As another method, a 2-bit indication (e.g., a 2-bit indicator) may indicate that only the second terminal may be a shared terminal, only the third terminal may be a shared terminal, or both the second terminal and the third terminal may be shared terminals. The indication may be included in the COT information and / or the SCI. Both the second terminal and the third terminal may be implicitly configured to be shared terminals and the priority of the second terminal may be higher than that of the third terminal. Alternatively, both the second terminal and the third terminal may be configured to be shared terminals and the priority of the second terminal may be higher than that of the third terminal by means of an additional indication. When a shared terminal performs SL communication within the remaining COT, the target terminal for SL communication may be limited to the first terminal that originally shared the COT. Alternatively, when a shared terminal performs SL communication within the remaining COT, the target terminal for SL communication may be a terminal other than the first terminal that originally shared the COT. The target terminal may be a terminal that performs SL communication with a shared terminal within the remaining COT.

[0205] When performing SL multicast communication or SL broadcast communication, multiple terminals may have the same destination ID. In this case, there may be multiple second terminals, and the multiple second terminals may be shared terminals. In other words, when COT information (e.g., COT sharing information) is sent, multiple second terminals may become shared terminals. When a shared terminal performs SL multicast communication or SL broadcast communication within the remaining COT, the target terminal for SL multicast communication or SL broadcast communication may be limited to one or more terminals (e.g., one or more second terminals) having the same destination ID as the shared terminal. The first terminal may also have the same destination ID as the shared terminal. The COT information of SL multicast communication or SL broadcast communication may include only the destination ID, excluding the source ID. In this case, the source ID part may be reserved. In addition, the COT information may include a propagation type indicator. The propagation type indicator may indicate that SL unicast communication, SL multicast communication, or SL broadcast communication is performed. In other words, the propagation type indicator may indicate the propagation type of SL communication.

[0206] In SL broadcast communication, all terminals may have the same destination ID. Therefore, the target terminal of SL broadcast communication may not be limited to a specific terminal or a specific terminal group. The target terminal of SL multicast communication may be limited to a specific terminal group with the same destination ID. When the shared terminal performs SL multicast communication within the remaining COT, the target terminal for SL multicast communication may be a terminal other than a terminal having the same destination ID as the shared terminal.

[0207] In SL unicast communication, the COT information may include information about the ID of the third terminal, information about a reference for selecting the third terminal, and / or an indication for setting a priority between the second terminal and the third terminal. The above operations in SL multicast communication or SL broadcast communication may be applied to SL unicast communication. Multiple terminals (e.g., multiple second terminals) with the same destination ID may become shared terminals. If coordination is not performed between shared terminals, conflicts between shared terminals may occur.

[0208] Fig.15a is a conceptual diagram showing a first exemplary embodiment of a COT sharing method in SL communication, Fig.15b is a conceptual diagram illustrating a second exemplary embodiment of a COT sharing method in SL communication.

[0209] refer to Fig.15a and Fig.15b , the second terminal may be a shared terminal in SL unicast communication, SL multicast communication and / or SL broadcast communication. Fig.15a In the SL unicast communication shown in , there may be one second terminal, and the one second terminal may be a shared terminal. Fig.15bIn the SL multicast communication and / or SL broadcast communication shown in , there may be multiple second terminals, and a separate reference or signaling for indicating or configuring a shared terminal between the multiple second terminals may be required. When there is no separate reference or signaling, it can be determined that all of the multiple second terminals are shared terminals, and when the multiple second terminals perform SL communication within the remaining COT, conflicts (e.g., data conflicts) may frequently occur between the transmissions of the terminals.

[0210] In SL unicast communication, multiple third terminals may be shared terminals. In this case, conflicts (e.g., data conflicts) may frequently occur between the transmissions of the terminals. When multiple terminals (e.g., the second terminal and / or the third terminal) are configured as shared terminals in SL unicast communication, or when multiple terminals (e.g., the second terminal and / or the third terminal) are configured as shared terminals in SL multicast communication and / or SL broadcast communication, additional signaling information for setting priorities to prevent conflicts between terminals may be included in the COT information.

[0211] When SL multicast communication is performed based on a management multicast scheme, the priority between terminals can be set by signaling of the member ID in the group. In the management multicast scheme, the terminal can know information about all terminals in the group. For example, the COT information may include the member ID of the terminal with priority (e.g., high priority), and the COT information may be sent. If there are multiple terminals with priority (e.g., high priority), the COT information may include the member IDs of the multiple terminals. The priority may be determined according to the order of the member IDs in the COT information. For example, the terminal corresponding to the first member ID in the member ID in the COT information may have the highest priority. Alternatively, the terminal corresponding to the last member ID in the member ID in the COT information may have the highest priority.

[0212] When SL multicast communication is performed based on a connectionless multicast scheme or when multiple third terminals can be shared terminals regardless of the type of SL communication (e.g., unicast, multicast, broadcast), it may be difficult to configure a specific terminal to have a priority (e.g., a high priority). In a connectionless multicast scheme, the terminal may not know information about the terminals in the group. In order to prevent conflicts between terminals in the above situation, the start time of the cyclic prefix extension (CPE) can be set differently by applying different start time offsets to multiple candidate shared terminals.

[0213] For example, if the start time of the CPE of a specific terminal (e.g., terminal #A) is the earliest among multiple candidate shared terminals, terminal #A may occupy the COT and perform SL communication within the COT. In this case, terminals other than terminal #A among the multiple candidate shared terminals may not be able to successfully perform LBT operations, and therefore may not be able to perform SL communication. In the above case, conflicts between terminals can be prevented. The offset of the start time of the CPE of multiple candidate shared terminals may be randomly set. The offset of the start time of the CPE of multiple candidate shared terminals may be set according to the CAPC of the SL data. Optionally, the offset of the start time of the CPE of multiple candidate shared terminals may be randomly set within multiple candidate values ​​set according to the CAPC of the SL data.

[0214] The lower the CAPC, the higher the transmission priority of the data may be. Therefore, it may be preferred to set the start time or start range of the CPE earlier in the time domain for a low CAPC. The start time or start range of the CPE may be set based on priority rather than CAPC. The offset of the start time of the CPE may be set in units of 9 μs. The offset of the start time of the CPE may be set in a range of up to 72 μs.

[0215] Fig.16 is a conceptual diagram of a first exemplary embodiment showing different offsets for a shared terminal.

[0216] refer to Fig.16 In order to prevent conflicts between terminals, different offsets may be applied to different shared terminals (e.g., terminal #A and terminal #B). A first terminal (e.g., an initiating terminal) may initiate a COT and share the initiated COT. Different offsets within the COT initiated by the first terminal may be applied to shared terminals (e.g., candidate shared terminals). By applying different offsets, terminal #A may perform a channel sensing operation (e.g., an LBT operation) before terminal #B, and may perform SL communication when a channel is sensed to be idle.

[0217] Terminal #B may perform a channel sensing operation, and if the channel is sensed to be busy, terminal #B may postpone or abandon SL communication. Since terminal #A occupies the channel, terminal #B may determine that the channel is busy. The start time of each channel sensing operation of terminal #A and terminal #B may be determined based on an offset. When different offsets are applied, conflicts between terminals may be prevented. The reference for applying different offsets may be random selection, CAPC, and / or priority.

[0218] In addition to the COT sharing method for general data transmission, a method for transmitting specific signals and / or specific channels may also be required. S-SSB can be used to obtain time synchronization and / or frequency synchronization of the terminal. If S-SSB transmission is required without distinguishing between the second terminal and the third terminal, the S-SSB can be sent within the COT shared by the first terminal. If one or more PSFCHs of the multiple PSFCHs sent by the second terminal include HARQ ACK / NACK feedback for the data sent by the first terminal, the second terminal may send PSFCH within the COT shared by the first terminal. PSFCH may refer to a channel for transmitting HARQ ACK / NACK feedback for data. PSFCH may represent HARQ ACK / NACK feedback for data.

[0219] Optionally, if the PSFCH sent by the second terminal and / or the third terminal does not include HARQ ACK / NACK feedback for the data sent by the first terminal, the second terminal and / or the third terminal may send PSFCH within the COT shared by the first terminal. Additional signaling (e.g., 1-bit indication) indicating whether the above operation is supported may be required. The above operation may be performed without distinguishing between the second terminal and the third terminal. When the operation of sending PSFCH within the COT shared by the first terminal without distinguishing between the second terminal and the third terminal is enabled by additional signaling, the second terminal and / or the third terminal may send PSFCH (e.g., HARQ ACK / NACK feedback) for data sent by terminals other than the first terminal within the COT shared by the first terminal. When the operation of sending PSFCH within the COT shared by the first terminal without distinguishing between the second terminal and the third terminal is disabled by additional signaling, the second terminal and / or the third terminal may not send PSFCH (e.g., HARQ ACK / NACK feedback) for data sent by terminals other than the first terminal within the COT shared by the first terminal. The additional signaling information may be included in the COT sharing information (eg, COT information).

[0220] The first terminal may obtain COT and send COT information (e.g., COT sharing information) to other terminals (e.g., the second terminal and / or the third terminal) to share COT with other terminals. The COT information may include information about the remaining COT duration. The COT information may only include information about the remaining COT duration. In this case, the remaining duration of the COT after the SL transmission of the first terminal may be signaled by the starting offset and / or the sharing offset. In the case of signaling the starting offset and / or the sharing offset, when the PSFCH of the sharing terminal (e.g., the second terminal and / or the third terminal) is sent to the first terminal in the time slot before the starting offset and / or the sharing offset, the above operation (e.g., COT sharing operation) may be feasible. Even when the PSFCH of the sharing terminal (e.g., the second terminal and / or the third terminal) is sent to another terminal instead of the first terminal, the above operation (e.g., COT sharing operation) may also be feasible.

[0221] The remaining COT may be a portion remaining after the SL communication of the first terminal within the COT acquired by the first terminal. The information about the duration of the remaining COT may be time information. The duration of the remaining COT may be defined in units of time (e.g., ms). Alternatively, the duration of the remaining COT may be defined by the number of symbols or the number of time slots (e.g., the number of physical time slots or the number of logical time slots).

[0222] The COT information may include information about the frequency of the COT (frequency information). The frequency information of the COT may include at least one of the starting position of the subchannel, the number of consecutive subchannels, the starting index of the interlace, the number of consecutive interlaces, the index of the resource pool, or the index of the RB set. If the COT information does not include the frequency information, all frequency regions (e.g., all subchannels, all interlaces, all RB sets) within the RB set or resource pool in which the COT information is transmitted may be interpreted as the frequency region of the COT.

[0223] The COT information may include information for selecting a shared terminal. The information for selecting a shared terminal may include the ID of a third terminal and / or information (e.g., distance information) for selecting a reference of a third terminal. Information indicating whether information for selecting a shared terminal is included may be included in the COT information. An indication of which terminal may become a shared terminal may be included in the COT information. CAPC may be included in the COT information. A smaller CAPC may have a higher priority, and a larger CAPC may have a lower priority. CAPC may be a reference indicating the priority according to the QoS of the data. When the COT information includes a specific CAPC and the CAPC of the SL communication of the shared terminal is less than or equal to the specific CAPC, the shared terminal may perform SL communication within the corresponding COT. For the above operation, the priority of the SL data may be used instead of the CAPC. If there are multiple CPE starting positions, the specific CPE starting position may be included in the COT sharing information (e.g., COT information). If there is a PSFCH transmission period within the COT, and there is a common interlacing of the PSFCH instead of the CPE in the PSFCH transmission period, the PSFCH transmission may be replaced by the transmission of the common interlacing.

[0224] Cyclic Prefix Extension (CPE) In an unlicensed band, the communication node may extend the CP from the time when the LBT operation is successful to maintain the channel occupied due to the success of the LBT operation until the actual transmission time. The CPE may be sent from the starting position of the CPE (hereinafter referred to as the "CPE starting position") until the start time of the next AGC symbol. One or more CPE starting positions may be configured. If one CPE starting position is configured, all terminals may have the same CPE starting position. Therefore, when multiple terminals perform SL communication using non-overlapping resources, frequency division multiplexing (FDM) operation may be feasible. When all terminals start the CPE at the same time and all terminals perform initial SL transmission, if information about the resources of the terminal is not obtained in advance, resource overlap between the terminals may not be identified. In the above case, a SL transmission with a high priority may conflict with a SL transmission with a low priority. In addition, SL transmission in all resources may conflict with SL transmission in some resources. Due to the conflict of SL transmission, the performance of SL communication may be reduced.

[0225] The CPE start position may be set differently according to the priority. For example, for a high priority SL transmission, the CPE start position may be configured as an earlier position in the time domain. Multiple CPE start positions may be configured, and a SL transmission with a high priority may be performed based on an earlier CPE start position. Therefore, the performance of a SL transmission with a high priority may be preferentially guaranteed.

[0226] Even when the resource areas of multiple terminals do not overlap, high priority SL transmission is performed based on an earlier CPE starting position, so FDM operation may not be possible. Therefore, resource efficiency may be reduced. In order to solve the above problem, when multiple CPE starting positions are configured, an earlier CPE starting position among the multiple CPE starting positions may be configured to be applied only to SL transmissions with a priority equal to or higher than a specific priority. Among the multiple CPE starting positions, the earlier starting position may be configured to be applied when the resources required for SL transmission are the entire resource pool and / or RB set or when the resources required for SL transmission are equal to or greater than X% of the resource pool and / or RB set. X can be a natural number.

[0227] Optionally, an earlier CPE starting position among multiple CPE starting positions may be configured to be applied when the priority of SL transmission is equal to or higher than a specific priority and the resources required for SL transmission are the entire resource pool and / or RB set. Optionally, an earlier starting position among multiple CPE starting positions may be configured to be applied when the priority of SL transmission is equal to or higher than a specific priority and the resources required for SL transmission are equal to or greater than X% of the resource pool and / or RB set. If the above conditions are not met, a default CPE starting position may be applied. In this case, FDM operation between multiple terminals may be feasible and resource efficiency may be improved.

[0228] Optionally, multiple CPE starting positions may be configured to be applied when the resources required for SL transmission are the entire resource pool and / or RB set or when the resources required for SL transmission are equal to or greater than X% of the resource pool and / or RB set. The default CPE starting position may be configured to be applied when the resources required for SL transmission are less than X% of the resource pool and / or RB set. In this case, FDM operation between multiple terminals may be feasible. When multiple CPE starting positions are applied, SL transmission with high priority may be performed based on an earlier CPE starting position. The default CPE starting position may be set to a specific CPE starting position among multiple CPE starting positions. For example, the default CPE starting position may be set to the earliest CPE starting position, the latest CPE starting position, or the middle CPE starting position among multiple CPE starting positions.

[0229] Optionally, regardless of the size of the resources required for SL transmission, SL transmission can be performed based on the CPE starting position preconfigured according to the priority. The default CPE starting position can be applied to the reserved resources. When the reservation information of the resources to which the default CPE starting position is to be applied is identified, the default CPE starting position can be applied. Since the terminal can identify the reserved resources by performing a resource sensing operation, the FDM operation can be performed relatively easily when the reserved resources are part of the frequency resources. Therefore, resource efficiency can be improved.

[0230] Based on the result of the resource sensing operation, the transmitting terminal can identify that the resources available for transmission do not overlap with the reserved resources of other terminals. In this case, the transmitting terminal can perform SL transmission based on the default CPE starting position. If the SL transmission of the transmitting terminal and the SL transmission of other terminals are performed simultaneously, the other terminals can also perform SL transmission based on the default CPE starting position. Therefore, FDM operation between multiple terminals may be feasible.

[0231] The CPE starting position may be configured according to the priority. One CPE starting position or multiple CPE starting positions may be configured for each priority. When multiple CPE starting positions are configured for each priority, the terminal may randomly select one CPE starting position from the multiple CPE starting positions. In order to support FDM operation between multiple terminals, SL transmission of multiple terminals may be performed based on the CPE starting position corresponding to the highest priority for SL transmission.

[0232] The priority and / or X may be set or indicated to the terminal through signaling (e.g., SI signaling, UE-specific RRC signaling, PC5-RRC signaling, MAC CE signaling, PHY signaling (e.g., DCI and / or SCI)). Optionally, the priority and / or X may be predefined in the technical specification. The priority and / or X may be set for each resource pool. Whether to support one CPE starting position or multiple CPE starting positions may be configured for each resource pool.

[0233] Even when multiple CPE starting positions are configured, PSFCH transmission and / or S-SSB transmission may be performed based on a common CPE starting position. The common CPE starting position may be the earliest CPE starting position or the latest CPE starting position among the multiple CPE starting positions. When multiple CPE starting positions are configured, it may be preferred to send S-SSB based on the common CPE starting position. Even when one common CPE starting position is configured for S-SSB transmission, the one common CPE starting position may vary depending on the situation. For example, a common CPE starting position for S-SSB transmission within a COT may be different from a common CPE starting position for S-SSB transmission outside a COT.

[0234] A common CPE starting position for a specific situation may be configured, and the common CPE starting position may be configured differently according to each situation. A plurality of CPE starting positions may be configured according to the priority of the synchronization reference terminal that performs S-SSB transmission. For example, a synchronization reference terminal with a higher priority may perform SL transmission (e.g., S-SSB transmission) based on an earlier CPE starting position, and a synchronization reference terminal with a lower priority may perform SL transmission (e.g., S-SSB transmission) based on a later CPE starting position. By configuring the above operations, S-SSB transmission of a synchronization reference terminal with a higher priority may be guaranteed.

[0235] A plurality of CPE start positions may be configured for each priority level. Optionally, a plurality of CPE start positions may be configured for each priority set. When the priority of PSFCH transmission is equal to or higher than a specific priority level, PSFCH transmission may be preferably performed based on an earlier CPE start position among the plurality of CPE start positions. When a plurality of CPE start positions are configured for each priority level, PSFCH transmission with a higher priority may be performed based on an earlier CPE start position, and PSFCH transmission with a lower priority may be performed based on a later CPE start position. According to the above operation, PSFCH transmission with a higher priority may be guaranteed.

[0236] The priority may be replaced by CAPC. The present disclosure may be applied when two or more CPE starting positions are configured. When N CPE starting positions are configured, the priority and / or X for each CPE starting position may be set individually. Optionally, the priority for each CPE starting position may be set individually, and one X for N CPE starting positions may be applied in common. A technique for preventing conflicts between terminals based on the configuration of multiple CPE starting positions may be applied between shared terminals (e.g., candidate shared terminals). In this case, the terminal (e.g., a shared terminal) may perform SL transmission based on the CPE starting position.

[0237] Multiple Continuous Slot Transmission (MCSt) When SL transmission is performed within a COT acquired by a terminal or a COT shared by another terminal, it may happen that SL transmission is interrupted. In this case, during the time period when SL transmission is interrupted, another terminal or communication node supporting another radio access technology (RAT) may occupy the channel by performing an LBT operation. In this case, COT may be lost. In order to maintain COT, continuous SL transmission may be required, and SL transmission may preferably be enabled in continuous time slots. When SL transmission is performed in continuous time slots, resource selection operations may be required to support the above operations.

[0238] One transport block (TB) or multiple TBs may be sent in a time slot. In an existing resource selection operation, a high layer of a terminal may transmit a parameter set including a priority of a TB, a remaining packet delay budget (PDB), the number of required subchannels, and / or a resource reservation periodicity to a physical layer of the terminal when generating a TB. When the parameter set is transmitted from the high layer to the physical layer, a resource selection operation may be triggered. The physical layer of the terminal may report a candidate resource set including candidate resources to the high layer of the terminal by referring to the parameter set. The high layer of the terminal may randomly select a candidate resource from the candidate resource set, and perform SL transmission using the selected candidate resource.

[0239] When different TBs are sent in consecutive time slots, the parameter sets used for resource selection for different TBs may be the same or different. If the parameter sets used for resource selection for multiple TBs are the same, the terminal may perform a resource selection operation based on one parameter set. If the parameter sets used for resource selection for multiple TBs are different, the terminal may perform a resource selection operation based on multiple parameter sets. When the terminal selects candidate resources in consecutive time slots based on multiple parameter sets, the complexity of the terminal may increase.

[0240] When the times of generating multiple TBs are different, the high-level trigger for each of the multiple parameter sets may be performed sequentially. In this case, a candidate resource set suitable for each of the multiple parameter sets may be configured, and the candidate resource set may be reported to the high-level layer. The high-level layer may give priority to selecting candidate resources in consecutive time slots based on each of the candidate resource sets. When it is difficult to select candidate resources in consecutive time slots in which multiple TBs are sent, candidate resources for TBs with higher priorities among the multiple TBs may be preferentially selected, and SL transmission (e.g., TB transmission) may be performed using the selected candidate resources. The resource selection operation for the remaining TBs among the multiple TBs may be abandoned. Optionally, the resource selection operation for the remaining TBs among the multiple TBs may be postponed to a later transmission time.

[0241] If the time to generate multiple TBs is almost the same, high-level triggering for sequential resource selection operations may not be feasible. In this case, the high-level layer of the terminal may preferentially trigger the resource selection operation for the TB with a higher priority among the multiple TBs. The resource selection operation for the remaining TBs among the multiple TBs may be abandoned. Optionally, the resource selection operation for the remaining TBs among the multiple TBs may be postponed to a later transmission time.

[0242] When the resource selection operation for the remaining TBs among the plurality of TBs is abandoned or when the resource selection operation for the remaining TBs among the plurality of TBs is postponed, SL transmission may preferably be continuously performed in order to maintain the COT. Therefore, the transmitting terminal may maintain the COT by performing repeated SL transmission for the preferentially selected TBs. If the receiving terminal knows that repeated SL transmission is performed, the receiving terminal may improve the reception performance by receiving the repeated SL transmission.

[0243] If one SL transmission among repeated SL transmissions (e.g., the first SL transmission, the SL transmission in the first time slot) is successfully received, the receiving terminal may or may not perform a receiving operation on the remaining SL transmissions. Whether the receiving terminal performs a receiving operation on the remaining SL transmissions may be determined by an implementation. The transmitting terminal may send an SCI (e.g., a first-level SCI and / or a second-level SCI) including information indicating whether to perform repeated SL transmissions.

[0244] Optionally, the transmitting terminal may perform repeated SL transmission to maintain the COT. In this case, the SL transmission in the first time slot among the repeated SL transmissions may be the transmission of actual data, and the SL transmission in the remaining time slots other than the first time slot among the repeated SL transmissions may be the transmission of virtual signals. The transmitting terminal may send an SCI including information indicating whether to perform repeated SL transmissions and / or information indicating whether to send a virtual signal. The above information may be explicitly signaled by a 1-bit indication included in the SCI. Optionally, the above information may be implicitly signaled by a specific value of a specific field included in the SCI. The receiving terminal may perform a receiving operation of actual data in the first time slot among the continuous time slots, and may omit the receiving operation in the remaining time slots among the continuous time slots.

[0245] When continuous time slots are configured, at least one of the continuous time slots may include a guard symbol for TX-RX switching and a guard symbol for RX-TX switching. In a time slot where PSFCH is not configured, the last symbol may be a guard symbol. In a time slot where PSFCH is configured, the symbol before PSFCH (or AGC symbol) and the symbol after PSFCH may be a guard symbol. Even when SL transmission is performed in continuous time slots within the COT, the COT may be lost due to the interruption of SL transmission in the remaining guard symbols of the last time slot except the last guard symbol. When SL transmission is performed in continuous time slots within the COT, the problem of discontinuous periods caused by the guard symbols in the time slots may preferably be solved by CPE.

[0246] CPE may be applied to SL transmission in a symbol after the protection symbol, and accordingly, SL transmission may also be performed in the protection symbol. Optionally, cyclic suffix extension (COE) may be applied to SL transmission in a symbol preceding the protection symbol, and accordingly, SL transmission may also be performed in the protection symbol. Whether CPE and / or COE are applied to SL transmission may be indicated by SCI. Optionally, the terminal may implementably apply CPE and / or COE to SL transmission.

[0247] As another method, the terminal may perform repeated SL transmission in the guard symbol and the next symbol of the guard symbol. Alternatively, the terminal may perform repeated SL transmission in the guard symbol and the symbol before the guard symbol. Whether to perform repeated SL transmission may be indicated by SCI. Alternatively, the terminal may practicably determine whether to perform repeated SL transmission.

[0248] In order to solve the problem of discontinuous periods caused by guard symbols in continuous time slots, guard symbols may be converted into data symbols. Data symbols may be symbols that can send and receive data (e.g., PSSCH). For example, the terminal may consider the guard symbol as a data symbol, and may perform SL transmission in the symbol including the considered data symbol. The number of data symbols included in the time slot to which the above method is applied may be more than the number of data symbols included in the existing time slot. Therefore, the terminal may send and receive data through PSSCH rate matching. The transmitting terminal may send SCI (e.g., first-level SCI and / or second-level SCI) including information indicating whether the guard symbol is considered as a data symbol and / or information indicating whether PSSCH rate matching is performed, and may send data based on the information included in the SCI. The receiving terminal may receive the SCI from the transmitting terminal and receive data based on the information included in the SCI. In this case, the receiving terminal may perform PSSCH rate matching based on the information included in the SCI during data reception.

[0249] When SL transmission is performed in continuous time slots, the remaining AGC symbols except the first AGC symbol may be converted into data symbols, and SL transmission may be performed in the converted data symbols. The existing AGC symbol may be used to repeat the SL transmission of the symbol after the existing AGC symbol. In this case, the existing AGC symbol may not help to improve the transmission efficiency. If the AGC symbol is converted into a data symbol that can send new data, the transmission efficiency and performance can be improved. In view of the above operations, SCI signaling may be necessary for smooth data transmission and reception. For example, information indicating whether the protection symbol and / or AGC symbol is converted into a data symbol may be included in the SCI.

[0250] When SL transmission is performed in continuous time slots, conversion of guard symbols and / or AGC symbols to data symbols may be necessary. Information indicating that the guard symbols are converted to data symbols and / or information indicating that the AGC symbols are converted to data symbols may be included in the SCI. Optionally, information indicating that the guard symbols and the AGC symbols are converted to data symbols may be included in the SCI. The information indicating conversion to data symbols may be a 2-bit indicator, and the 2-bit indicator may be configured as shown in Table 6 below.

[0251] [Table 6]

[0252] The protection symbol converted to the data symbol may be the remaining protection symbols except the last protection symbol of the last time slot among the multiple time slots. The AGC symbol converted to the data symbol may be the remaining AGC symbols except the first AGC symbol of the first time slot among the multiple time slots. The terminal may identify the data symbol based on the indicator in Table 6 and perform SL communication in the data symbol. Optionally, the information indicating the conversion to the data symbol may be a 1-bit indicator. In this case, a 1-bit indicator set to a first value (e.g., 0) may indicate that the protection symbol and the AGC symbol are not converted to the data symbol, and a 1-bit indicator set to a second value (e.g., 0) may indicate that the protection symbol and the AGC symbol are converted to the data symbol.

[0253] Fig.17a is a conceptual diagram showing a first exemplary embodiment of SL transmission, and Fig.17b is a conceptual diagram illustrating a second exemplary embodiment of SL transmission.

[0254] refer to Fig.17a and Fig.17b , SL transmission can be performed in consecutive time slots. Fig.17a The time slot shown may be an existing time slot and Fig.17b In the time slot shown, the guard symbol and the AGC symbol may be converted into data symbols, and SL transmission (e.g., PSSCH transmission) may be performed in the converted data symbols. The SL transmission in the converted data symbols may be a repeated transmission of the SL transmission in the previous symbol of the converted data symbols or a repeated transmission of the SL transmission in the subsequent symbol of the converted data symbols. Rate matching may be applied to the SL transmission in the data symbols including the converted data symbols.

[0255] The guard symbol and / or AGC symbol may not be converted into a data symbol, and SL transmission may be performed in the guard symbol and / or AGC symbol by applying CPE or COE to SL transmission. When one TB is transmitted in a continuous time slot, the guard symbol and / or AGC symbol may be preferably converted into a data symbol for the transmission operation of the one TB. When different TBs are transmitted in a continuous time slot, CPE or COE may be preferably applied to the transmission operations of different TBs.

[0256] In addition to the protection symbol and / or AGC symbol, the PSCCH symbol may also be converted into a data symbol. The PSCCH symbol may be a symbol used for PSCCH transmission. When all control information for SL transmission in consecutive time slots is sent in the first PSCCH, the remaining PSCCH may not be used for control information transmission. In this case, the symbol used to transmit the remaining PSCCH may be converted into a data symbol. Information indicating whether the PSCCH symbol is converted into a data symbol may be included in the SCI.

[0257] When SL transmission is performed in continuous time slots, in addition to protection symbols and / or AGC symbols, PSFCH symbols may also need to be considered. PSFCH symbols can be symbols used for PSFCH transmission. When a terminal performs PSFCH transmission in a PSFCH symbol configured in a continuous time slot, COT can be maintained. In the above case, if another terminal requires PSFCH transmission in a PSFCH symbol, the other terminal may perform an LBT operation for PSFCH transmission. If the LBT operation fails, the other terminal may not be able to perform PSFCH transmission.

[0258] Even when PSFCH transmission is not needed in PSFCH symbols in continuous time slots, the terminal may send an arbitrary signal in the PSFCH symbol to maintain the COT. When one terminal continuously performs SL transmission in the COT, other terminals may not perform SL transmission in the COT (for example, the period in which the one terminal performs SL transmission). Therefore, there may be no other terminals that need PSFCH transmission in the PSFCH symbol within the COT. If there are other terminals that need PSFCH transmission in the PSFCH symbol within the COT, the other terminals may not be able to perform PSFCH transmission due to the failure of the LBT operation. In this case, PSFCH resources may be wasted.

[0259] In order to solve the above problem, a terminal that maintains COT by performing SL transmission in continuous time slots may stop SL transmission in PSFCH symbols (e.g., PSFCH symbols of PSFCH time slots) in continuous time slots. Even when the maximum occupancy time of COT is not reached, the terminal may stop SL transmission in PSFCH symbols within COT. In this case, COT can be terminated. Optionally, when a common CPE starting position for PSFCH transmission is configured, the terminal may perform SL transmission (e.g., data transmission) until a guard symbol before the PSFCH symbol, stop SL transmission from the guard symbol, and perform PSFCH transmission based on the guard symbol and the common CPE starting position in the PSFCH symbol. According to the above operation, COT can be maintained.

[0260] The time period from the time when SL transmission stops to the common CPE start position can be configured to be short enough to meet the conditions for maintaining COT. A terminal that performs SL transmission in continuous time slots can send an arbitrary signal at the common CPE start position to maintain COT, even when PSFCH transmission is not required in the PSFCH symbol. In this case, in order to prevent a conflict between an arbitrary signal and PSFCH transmission of other terminals, SL transmission can be performed in an arbitrary resource that is not configured as a PSFCH resource (e.g., a PSFCH symbol).

[0261] For example, since PSFCH transmission is configured to be performed in some frequency regions within the resource pool, when the terminal knows the remaining frequency regions other than the some frequency regions or knows the frequency regions where PSFCH transmission is not actually performed in the PSFCH resources, the terminal can send an arbitrary signal in the corresponding frequency region. Additional transmission can be performed together with PSFCH transmission to meet the OCB requirements for PSFCH transmission. Additional transmission can be performed in a common redundant RB (e.g., an interleaved RB). The arbitrary signal can be the same signal as PSFCH or a similar signal. Optionally, the arbitrary signal can be configured as a specific signal. The terminal can implementably select an arbitrary signal.

[0262] Optionally, PSFCH resources may not be configured in the resource pool for which MCSt is configured. Even when PSFCH resources are configured in the resource pool for which MCSt is configured, the HARQ ACK / NACK feedback function may be disabled in the time period for MCSt. Whether MCSt operation is supported may be configured based on the resource pool or SL BWP. Even when MCSt operation is configured to be supported, MCSt operation may be allowed when y or more RBs in the resource pool are configured as resources for SL transmission to improve resource efficiency, and the priority of SL transmission is higher than a specific priority. A specific priority may be indicated or configured to the terminal through signaling (e.g., SI signaling, UE-specific RRC signaling, PC5-RRC signaling, MAC CE signaling, PHY signaling (e.g., DCI and / or SCI)). Optionally, y and / or a specific priority may be predefined in the technical specification. y may be a natural number.

[0263] When multiple TBs are transmitted based on the MCSt operation, each of the multiple TBs may have a different CAPC. In this case, in the type 1 channel access process for the MCSt operation, the CAPC may be set to the maximum CAPC or the minimum CAPC among the CAPCs corresponding to the multiple TBs. The maximum CAPC value may represent the lowest CAPC level, and the minimum CAPC value may represent the highest CAPC level.

[0264] When one TB is sent based on the MCSt operation, HARQ ACK / NACK feedback for the one TB may not be sent while the MCSt operation is performed. Therefore, it may be difficult to meet the round trip time (RTT) of the HARQ ACK / NACK feedback. In this case, in the MCSt operation, HARQ ACK / NACK feedback only for the last PSCCH and / or PSSCH transmission may be enabled, and HARQ ACK / NACK feedback for the last PSCCH and / or PSSCH transmission may be performed.

[0265] Multi-channel access process Multi-channel transmission operation in an unlicensed band may be advantageous for large-capacity data transmission. When there are multiple RB sets in an unlicensed band, a communication node may perform an LBT operation on a channel corresponding to each of the multiple RB sets, and send and receive data according to the result of the LBT operation. In NR-U communication, the multi-channel access procedure for DL ​​communication and the multi-channel access procedure for UL communication may be different. The channel access procedure for DL ​​communication may be classified into a type A multi-channel access procedure and a type B multi-channel access procedure.

[0266] When a type A multi-channel access procedure is used in DL communication, the communication node may perform a type 1 channel access procedure in each of a plurality of channels, and send data in a channel in which the type 1 channel access procedure is successful. When a type B multi-channel access procedure is used in DL communication, the communication node may perform a type 1 channel access procedure in one of a plurality of channels, and perform a type 2 channel access procedure in the remaining channels, and send data in a channel in which the type 1 channel access procedure and / or the type 2 channel access procedure is successful. In the type 2 channel access procedure, the communication node may perform a sensing operation in a preconfigured period (e.g., a minimum of 25 μs).

[0267] In UL communication, the communication node may perform a type 1 channel access procedure (e.g., LBT operation) in all channels among the multiple channels, and transmit data when the type 1 channel access procedure succeeds in all channels among the multiple channels. If the type 1 channel access procedure fails in at least one channel among the multiple channels, the communication node may not transmit data.

[0268] The multi-channel access procedure for UL communication of NR-U can be applied to SL communication. When the multi-channel access procedure for DL ​​communication of NR-U is applied to SL communication, the receiving terminal may not know in which channel of the multiple channels the transmitting terminal successfully performs the LBT operation. Therefore, when a TB is sent in multiple channels, the receiving terminal can perform a receiving operation by considering various situations according to whether the LBT operation is successful in the channel. According to the above operation, the receiving complexity of the receiving terminal may increase. Since PSFCH transmission and / or S-SSB transmission are performed independently for each channel, the receiving terminal may not need to consider various situations according to whether the LBT operation is successful in different channels. Therefore, for PSFCH transmission and / or S-SSB transmission, it is preferred to apply type A multi-channel access procedure and / or type B multi-channel access procedure to DL communication in NR-U communication.

[0269] Resource Selection Process Since the LBT operation is performed before the transmission in the unlicensed band, it is preferred that in the resource selection process, not only the reserved resources of other terminals but also the resources used to perform the LBT operation for transmission in the reserved resources are excluded. The type 2 channel access process can be fully performed within the guard symbol of the previous time slot of the reserved resources. For the type 1 channel access process, the entire period of the previous time slot of the reserved resources may be required. When selecting (e.g., reserving) resources for SL transmission in the resource selection process, it is preferred to identify whether the type 1 channel access process can be performed until the SL transmission is performed using the selected resources (e.g., the reserved resources). Before performing SL transmission using the selected resources, a type 1 channel access process may be required to occupy a channel for the terminal.

[0270] If the previous resource of the resource selected in the time domain is occupied by the transmission of another terminal, the type 1 channel access process for channel occupancy may fail. If the type 1 channel access process fails, the communication node may not be able to use the selected resource. Therefore, in the resource selection process for SL transmission, it can be identified whether not only a specific resource but also a previous resource of the specific resource has been reserved or occupied by another terminal. If the previous resource of the specific resource is reserved or occupied by another terminal, the specific resource can be excluded from the resource selection process. The amount of resources that are considered as previous resources for specific resources can be preset through system information and / or RRC signaling (e.g., UE-specific RRC signaling).

[0271] In order not to interfere with the channel access process for SL transmission of another terminal, the previous resources of the resources reserved by another terminal in the time domain may be excluded from the resource selection process. The amount of resources (e.g., the number of time slots) of the previous resources regarded as resources reserved by another terminal may be pre-configured through system information and / or RRC signaling (e.g., UE-specific RRC signaling). Based on the comparison result between the priority of the terminal and the priority of the other terminal, the terminal may determine whether to exclude the resources reserved by the other terminal during the resource selection process. If the priority of the other terminal is higher than the priority of the terminal, the terminal may exclude the resources reserved by the other terminal during the resource selection process. If the priority of the terminal is higher than the priority of the other terminal, the terminal may not exclude the resources reserved by the other terminal during the resource selection process. The priority may be the priority of the data or the CAPC.

[0272] Optionally, whether to share the COT may be considered in the resource selection process. If the COT is shared by another terminal, the shared terminal may perform a type 2 channel access procedure instead of a type 1 channel access procedure before SL transmission. If the COT can be shared by another terminal, the terminal (e.g., the shared terminal) may give priority to selecting the next resource of the reserved resources of the other terminal. If the CAPC of the SL transmission of the terminal is less than or equal to the CAPC of the SL transmission of the other terminal, or if the priority of the SL transmission of the terminal is higher than the priority of the SL transmission of the other terminal, the COT initiated by the other terminal may be shared with the terminal.

[0273] The terminal may share the COT with other terminals. After performing SL transmission, the terminal may share the COT with another terminal, and the other terminal may perform SL transmission after performing a type 2 channel access procedure in the shared COT. The terminal that may share the COT with another terminal may preferentially select a previous resource of the reserved resource of the other terminal in the time domain. The conditions of the CAPC and / or priority for COT sharing may be applied in the same or similar manner as the above-described exemplary embodiments.

[0274] Each of the above different methods may be supported according to the capabilities of the terminal. The enabling or disabling of each of the above different methods may be pre-configured through system information and / or RRC signaling (eg, UE-specific RRC signaling).

[0275] Since the CW size may vary and a random backoff operation is applied in the Type 1 channel access procedure, it may not be preferred to exclude the previous and / or subsequent resources of the reserved resources of another terminal in the resource selection process. Considering various parameters for the Type 1 channel access procedure, it may be preferred to exclude continuous resources.

[0276] Short Control Signaling Transport (SCSt) Depending on the conditions of the transmission cycle and / or transmission time for the unlicensed band, the transmission of control signals in a short transmission period may be performed without performing an LBT operation. The above conditions may include a condition that the number of transmissions in a 50ms period is less than 50 times and / or a condition that the total transmission time is less than 2500us. In view of the above operations, PSFCH and / or S-SSB may be considered as short control signals, and PSFCH and / or S-SSB may be sent without performing an LBT operation. S-SSB transmission may meet the above conditions. If the PSFCH transmission cycle is short, the PSFCH transmission may not meet the above conditions.

[0277] PSFCH transmission and S-SSB transmission can satisfy the above conditions separately, but if PSFCH transmission and S-SSB transmission are considered together, the above conditions may not be satisfied. Therefore, the communication node can preferentially send S-SSB without performing LBT operation according to the above conditions, and then perform PSFCH transmission within a feasible range.

[0278] Mode 1 Operation If SL-U communication supports mode 1 operation, the terminal may send information about whether the LBT operation is successful to the base station to assist the base station in resource allocation. The terminal may perform LBT operation for SL transmission in the resources allocated by the base station, and if the LBT operation fails, SL transmission may not be performed. In this case, the terminal may send NACK to the base station. The base station may receive NACK from the terminal. The base station may not be able to distinguish whether the NACK of the terminal is a NACK caused by the failure of the LBT operation or a NACK caused by the failure of data transmission. Therefore, in addition to ACK and NACK, a new state indicating the failure of the LBT operation may be defined. The new state may indicate the failure of data transmission due to the failure of the LBT operation. In addition to the cyclic shift pair representing the ACK / NACK information, the new state may be expressed by setting a separate cyclic shift value.

[0279] When reporting the failure of an LBT operation, it may be necessary to distinguish the resource units (e.g., RB sets, resource pools, BWPs) on which the failed LBT operation has been performed. The unit (e.g., resource unit) for reporting the failure of the LBT operation may be set by signaling (e.g., SI signaling, UE-specific RRC signaling, PC5-RRC signaling). Optionally, the unit for reporting the failure of the LBT operation may be predefined in the technical specification. Optionally, a separate cyclic shift pair may be applied for each resource unit for reporting the failure of the LBT operation. The failure of the LBT operation may be reported by a bit indication rather than in the form of a sequence.

[0280] The operation of the method according to the exemplary embodiment of the present disclosure can be implemented as a computer-readable program or code in a computer-readable recording medium. The computer-readable recording medium may include all kinds of recording devices for storing data that can be read by a computer system. In addition, the computer-readable recording medium can store and execute a program or code that can be distributed in a computer system connected via a network and read by a computer in a distributed manner.

[0281] The computer readable recording medium may include a hardware device specifically configured to store and execute program commands, such as ROM, RAM or flash memory. The program command may include not only the machine language code created by the compiler, but also the high-level language code that can be executed by the computer using an interpreter.

[0282] Although some aspects of the present disclosure have been described in the context of a device, these aspects may indicate the corresponding description according to the method, and the box or device may correspond to the steps of the method or the features of the steps. Similarly, the aspects described in the context of the method may be expressed as the features of the corresponding boxes or items or corresponding devices. 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.

[0283] In some exemplary embodiments, a programmable logic device such as a field programmable gate array may be used to perform some or all of the functions of the methods described herein. In some exemplary embodiments, the field programmable gate array may be operated with a microprocessor to perform one of the methods described herein. Typically, the method is preferably performed by a specific hardware device.

[0284] The description of the present disclosure is only exemplary in nature, and therefore, changes that do not depart from the essence of the present disclosure are intended to fall within the scope of the present disclosure. These changes should not be considered to be out of the spirit and scope of the present disclosure. 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 of a first terminal, comprising: Send data to multiple terminals based on a multicast solution; receiving one or more hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedbacks for the data from one or more terminals among the plurality of terminals; adjusting a content window CW size based on a comparison result between a threshold and an ACK ratio of the one or more HARQ-ACK feedbacks; as well as Side link SL communication is performed based on the CW with the adjusted CW size.

2. The method according to claim 1, wherein: When the ACK ratio is equal to or greater than the threshold, the CW size is reduced, and when the ACK ratio is less than the threshold, the CW size is increased.

3. The method according to claim 2, wherein: When the ACK ratio is equal to or greater than the threshold, the CW size is adjusted to a minimum CW size.

4. The method according to claim 1, further comprising: A higher layer message including information about the threshold is received from a base station.

5. The method according to claim 1, wherein: The threshold is set in a user equipment UE-specific manner or a cell-specific manner.

6. The method according to claim 1, wherein: The threshold is set independently for each resource pool.

7. The method according to claim 1, wherein: The minimum CW size and the maximum CW size of the CW sizes are independently set according to channel access priority levels (CAPCs), respectively.

8. The method according to claim 1, wherein: When at least one HARQ-ACK feedback is not received from at least one terminal among the plurality of terminals, the at least one HARQ-ACK feedback for the at least one terminal is regarded as negative ACK (NACK).

9. A method of a first terminal, comprising: performing a first side link SL communication using a first CW having a first contention window CW size; as well as When a hybrid automatic repeat request HARQ-acknowledgement ACK feedback function is disabled, a second SL communication is performed using the first CW having the first CW size as a latest size.

10. The method according to claim 9, further comprising: When the first CW size is used x times, adjusting the first CW size to a second CW size that is larger than the first CW size; as well as performing a third SL communication using a second CW having the second CW size, Where x is a natural number.

11. The method according to claim 10, further comprising: A higher layer message including information about x is received from a base station.

12. The method according to claim 10, wherein: x is set in a user equipment UE-specific manner or a cell-specific manner.

13. The method according to claim 9, further comprising: When the first CW size is a maximum CW size and the maximum CW size is used x times, adjusting the first CW size to a minimum CW size; as well as performing a fourth SL communication using a minimum CW having the minimum CW size, Where x is a natural number.

14. The method according to claim 9, wherein: The minimum CW size and the maximum CW size of the first CW size are independently set according to a channel access priority level CAPC, respectively.

15. A first terminal, comprising at least one processor, in, The at least one processor causes the first terminal to execute: Send data to multiple terminals based on a multicast solution; receiving one or more hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedbacks for the data from one or more terminals among the plurality of terminals; adjusting a content window CW size based on a comparison result between a threshold and an ACK ratio of the one or more HARQ-ACK feedbacks; as well as Side link SL communication is performed based on the CW with the adjusted CW size.

16. The first terminal according to claim 15, wherein: When the ACK ratio is equal to or greater than the threshold, the CW size is reduced, and when the ACK ratio is less than the threshold, the CW size is increased.

17. The first terminal according to claim 15, wherein: The at least one processor further causes the first terminal to perform: receiving a higher layer message including information about the threshold from a base station.

18. The first terminal according to claim 15, wherein: The threshold is set in a user equipment UE-specific manner or a cell-specific manner.

19. The first terminal according to claim 15, wherein: The minimum CW size and the maximum CW size of the CW sizes are independently set according to the channel access priority level CAPC, respectively.

20. The first terminal according to claim 15, wherein: When at least one HARQ-ACK feedback is not received from at least one terminal among the plurality of terminals, the at least one HARQ-ACK feedback for the at least one terminal is regarded as negative ACK (NACK).

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