Method and apparatus for performing sidelink communication in wireless communication system

Abstract

A method and an apparatus for performing communication in a wireless communication system are disclosed. A method for performing communication by a first terminal according to one embodiment of the present disclosure may comprise the steps of: receiving, from a base station, first setting information related to a sidelink (SL)-specific listen before talk (LBT) failure detection timer and second setting information related to an SL-specific LBT failure counter; triggering a consistent SL-specific LBT failure based on the SL-specific failure detection timer and the SL-specific LBT failure counter; releasing an SL connection between the second terminals associated with the triggered consistent SL-specific LBT failure; and transmitting, to the base station, information indicating at least one of the triggered consistent SL-specific LBT failure or SL connection release.

Description

Technical Field

[0001] The present disclosure relates to a wireless communication system, and more particularly, to a method and apparatus for performing sidelink communication in a wireless communication system. Background Art

[0002] A mobile communication system has been developed to provide voice services while ensuring user mobility. However, the mobile communication system has been extended to data services as well as voice services, and currently, the explosive growth of services has led to resource shortages, and users have demanded faster services, thus requiring more advanced mobile communication systems.

[0003] The overall requirements of the next generation mobile communication system should be able to support the accommodation of explosive data services, a significant increase in the transmission rate per user, the accommodation of a significantly increased number of connected devices, very low end-to-end latency and high energy efficiency. To this end, a variety of technologies such as dual connectivity, massive multiple-input multiple-output (massive MIMO), in-band full-duplex, non-orthogonal multiple access (NOMA), ultra-wideband support, and device networking have been studied. Summary of the invention

[0004] Technical issues

[0005] The technical problem of the present disclosure is to provide a method and apparatus for performing side link communication in a wireless communication system.

[0006] The technical problem of the present disclosure is to provide a method and apparatus for detecting / triggering SL-specific LBT failure based on a SL-specific LBT failure related counter and a SL-specific LBT failure detection timer.

[0007] The technical problem of the present disclosure is to provide a method and apparatus for releasing a SL connection associated with a triggered / detected SL-specific LBT failure.

[0008] The technical objectives to be achieved by the present disclosure are not limited to the above-mentioned technical objectives, and those skilled in the art can clearly understand other technical objectives not described herein through the following description.

[0009] Technical Solution

[0010] According to one embodiment of the present disclosure, a method performed by a first user equipment (UE) in a wireless communication system may include: receiving first configuration information related to a sidelink (SL) specific LBT (listen before talk) failure detection timer and second configuration information related to a SL specific LBT failure counter from a base station; triggering a consistent SL specific LBT failure based on the SL specific failure detection timer and the SL specific LBT failure counter; releasing the SL connection of a second UE related to the triggered consistent SL specific LBT failure; and sending information to the base station indicating at least one of the triggered consistent SL specific LBT failure or the release of the SL connection.

[0011] According to one embodiment of the present disclosure, a method performed by a base station in a wireless communication system may include: sending first configuration information related to a sidelink (SL) specific LBT (listen before talk) failure detection timer and second configuration information related to a SL specific LBT failure counter to a user equipment (UE); and receiving information from a first UE indicating at least one of a consistent SL specific LBT failure triggered by the first UE or a release of a SL connection between the first UE and a second UE, and a consistent SL specific LBT failure can be triggered based on the SL specific failure detection timer and the SL specific LBT failure counter, and the SL connection between the first UE and the second UE related to the triggered consistent SL specific LBT failure can be released.

[0012] Technical Effects

[0013] According to one embodiment of the present disclosure, a method and apparatus for performing sidelink communication in a wireless communication system may be provided.

[0014] According to various embodiments of the present disclosure, a method and apparatus for detecting / triggering a SL-specific LBT failure based on a SL-specific LBT failure related counter and a SL-specific LBT failure detection timer may be provided.

[0015] According to various embodiments of the present disclosure, a method and apparatus for releasing and reporting a SL connection associated with a triggered / detected SL-specific LBT failure may be provided.

[0016] According to one embodiment of the present disclosure, by receiving information reporting whether the SL connection between terminals is released, the base station can operate the side link resources more efficiently.

[0017] Effects achievable by the present disclosure are not limited to the above-described effects, and other effects not described herein may be clearly understood by those skilled in the art through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are included as a part of the detailed description for understanding the present disclosure, provide embodiments of the present disclosure and describe technical features of the present disclosure through the detailed description.

[0019] Figure 1 The structure of a wireless communication system to which the present disclosure can be applied is illustrated.

[0020] Figure 2 The frame structure in a wireless communication system to which the present disclosure can be applied is illustrated.

[0021] Figure 3 A resource grid in a wireless communication system to which the present disclosure can be applied is illustrated.

[0022] Figure 4 The physical resource blocks in a wireless communication system to which the present disclosure can be applied are illustrated.

[0023] Figure 5 The time slot structure in a wireless communication system to which the present disclosure can be applied is illustrated.

[0024] Figure 6 Physical channels used in a wireless communication system to which the present disclosure can be applied and a general signal transmission and reception method using the physical channels are illustrated.

[0025] Figure 7 A process of performing V2X or SL communication according to a transmission mode in a wireless communication system to which the present disclosure can be applied is illustrated.

[0026] Figure 8 The broadcast types used for V2X or SL communication in a wireless communication system to which the present disclosure can be applied are illustrated.

[0027] Fig. 9 is a diagram for explaining a process in which a first UE performs communication according to an embodiment of the present disclosure.

[0028] Fig.10 is a diagram for explaining a process in which a base station performs communication according to an embodiment of the present disclosure.

[0029] Fig.11 is a diagram for explaining signaling procedures of a base station, a first UE, and a second UE according to an embodiment of the present disclosure.

[0030] Fig.12 is a diagram for explaining a (SL) LBT failure MAC CE structure according to an embodiment of the present disclosure.

[0031] Fig.13 A block diagram of a wireless communication device according to an embodiment of the present disclosure is illustrated. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. The detailed description disclosed by the accompanying drawings is intended to describe exemplary embodiments of the present disclosure, rather than to represent the only embodiment in which the present disclosure can be implemented. The following detailed description includes specific details to provide a complete understanding of the present disclosure. However, those skilled in the relevant art know that the present disclosure can be implemented without these specific details.

[0033] In some cases, well-known structures and devices may be omitted, or may be shown in the form of a block diagram based on the core functions of each structure and device in order to prevent ambiguity in the concepts of the present disclosure.

[0034] In the present disclosure, when an element is referred to as being "connected", "combined" or "linked" to another element, it may include an indirect connection relationship between another element and a direct connection relationship. In addition, in the present disclosure, the term "comprising" or "having" specifies the presence of the mentioned features, steps, operations, components and / or elements, but does not exclude the presence or addition of one or more other features, stages, operations, components, elements and / or groups thereof.

[0035] In the present disclosure, terms such as "first", "second", etc. are only used to distinguish one element from another element and are not used to limit the elements, and unless otherwise specified, they do not limit the order or importance between elements, etc. Therefore, within the scope of the present disclosure, the first element in an embodiment may be referred to as the second element in another embodiment, and similarly, the second element in an embodiment may be referred to as the first element in another embodiment.

[0036] The terms used in this disclosure are intended to describe specific embodiments, rather than to limit the claims. As used in the description of the embodiments and the appended claims, the singular form is intended to include the plural form, unless the context clearly indicates otherwise. The term "and / or" used in this disclosure may refer to one of the related enumerated items, or mean that it refers to and includes any and all possible combinations of two or more of them. In addition, unless otherwise stated, the " / " between words in the present invention has the same meaning as "and / or".

[0037] The present disclosure describes a wireless communication network or a wireless communication system, and operations performed in the wireless communication network can be performed in a process in which a device (e.g., a base station) controlling the corresponding wireless communication network controls the network and sends or receives signals, or can be performed in a process in which a terminal associated with the corresponding wireless network sends or receives signals between the network or the terminal.

[0038] In the present disclosure, sending or receiving a channel includes the meaning of sending or receiving information or signals through the corresponding channel. For example, sending a control channel means sending control information or control signals through the control channel. Similarly, sending a data channel means sending data information or data signals through the data channel.

[0039] In the following, downlink (DL) means communication from a base station to a terminal, and uplink (UL) means communication from a terminal to a base station. In the downlink, the transmitter may be part of a base station, and the receiver may be part of a terminal. In the uplink, the transmitter may be part of a terminal, and the receiver may be part of a base station. The base station may be expressed as a first communication device, and the terminal may be expressed as a second communication device. The base station (BS) may be replaced by terms such as a fixed station, a node B, an eNB (evolved node B), a gNB (next generation node B), a BTS (base station transceiver system), an access point (AP), a network (5G network), an AI (artificial intelligence) system / module, an RSU (roadside unit), a robot, a drone (UAV: unmanned aerial vehicle), an AR (augmented reality) device, a VR (virtual reality) device, and the like. In addition, the terminal can be fixed or mobile, and can be replaced by terms such as UE (user equipment), MS (mobile station), UT (user terminal), MSS (mobile subscriber station), SS (subscriber station), AMS (advanced mobile station), WT (wireless terminal), MTC (machine type communication) device, M2M (machine to machine) device, D2D (device to device) device, vehicle, RSU (roadside unit), robot, AI (artificial intelligence) module, drone (UAV: unmanned aerial vehicle), AR (augmented reality) device, VR (virtual reality) device, etc.

[0040] The following description can be used for various radio access systems, such as CDMA, FDMA, TDMA, OFDMA, SC-FDMA, etc. CDMA can be implemented by UTRA (Universal Terrestrial Radio Access) or CDMA2000. TDMA can be implemented by radio technologies such as GSM (Global System for Mobile Communications) / GPRS (General Packet Radio Service) / EDGE (Data Rate Enhanced GSM Evolution). OFDMA can be implemented by radio technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802-20, E-UTRA (Evolved UTRA), etc. UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is part of E-UMTS (Evolved UMTS) using E-UTRA, and LTE-A (Advanced) / LTE-A pro is an advanced version of 3GPP LTE. 3GPP NR (New Radio or New Radio Access Technology) is an advanced version of 3GPP LTE / LTE-A / LTE-A pro.

[0041] In order to make the description clearer, the description is based on the 3GPP communication system (e.g., LTE-A, NR), but the technical idea of ​​the present disclosure is not limited to this. LTE means the technology after 3GPP TS (Technical Specification) 36.xxx version 8. Specifically, the LTE technology in or after 3GPP TS 36.xxx version is called LTE-A, and the LTE technology in or after 3GPP TS 36.xxx version 13 is called LTE-A pro. 3GPP NR means the technology in or after TS 38.xxx version. LTE / NR can be referred to as a 3GPP system. "xxx" means the detailed number of the standard document. LTE / NR can generally be referred to as a 3GPP system. For the background technology, terms, abbreviations, etc. used to describe the present disclosure, reference can be made to the matters described in the standard documents disclosed before the present disclosure. For example, reference can be made to the following documents.

[0042] For 3GPP LTE, reference may be made to TS 36.211 (Physical Channels and Modulation), TS 36.212 (Multiplexing and Channel Coding), TS 36.213 (Physical Layer Procedures), TS 36.300 (Overall Description), and TS 36.331 (Radio Resource Control).

[0043] For 3GPP NR, you can refer to TS 38.211 (Physical channels and modulation), TS 38.212 (Multiplexing and channel coding), TS 38.213 (Physical layer procedures for control), TS 38.214 (Physical layer procedures for data), TS 38.300 (NR and NG-RAN (Next Generation Radio Access Network) overall description), and TS 38.331 (Radio Resource Control Protocol Specification).

[0044] Abbreviations of terms that may be used in the present disclosure are defined as follows.

[0045] -BM: Beam Management

[0046] -CQI: Channel Quality Indicator

[0047] -CRI: Channel State Information-Reference Signal Resource Indicator

[0048] -CSI: Channel State Information

[0049] -CSI-IM: Channel State Information-Interference Measurement

[0050] -CSI-RS: Channel State Information-Reference Signal

[0051] -DMRS: Demodulation Reference Signal

[0052] -FDM: Frequency Division Multiplexing

[0053] -FFT: Fast Fourier Transform

[0054] -IFDMA: Interleaved Frequency Division Multiple Access

[0055] -IFFT: Inverse Fast Fourier Transform

[0056] -L1-RSRP: Layer 1 reference signal received power

[0057] -L1-RSRQ: Layer 1 reference signal reception quality

[0058] -MAC: Media Access Control

[0059] -NZP: Non-Zero Power

[0060] -OFDM: Orthogonal Frequency Division Multiplexing

[0061] -PDCCH: Physical Downlink Control Channel

[0062] -PDSCH: Physical Downlink Shared Channel

[0063] -PMI: Precoding matrix indicator

[0064] -RE: Resource Element

[0065] -RI: Rank Indicator

[0066] -RRC: Radio Resource Control

[0067] -RSSI: Received Signal Strength Indicator

[0068] -Rx: Receive

[0069] -QCL: Quasi-Co-located

[0070] -SINR: Signal to Interference and Noise Ratio

[0071] -SSB (or SS / PBCH block): synchronization signal block (including PSS (primary synchronization signal), SSS (secondary synchronization signal) and PBCH (physical broadcast channel))

[0072] -TDM: Time Division Multiplexing

[0073] -TRP: Transmit and Receive Point

[0074] -TRS: Tracking Reference Signal

[0075] -Tx: Send

[0076] -UE: User Equipment

[0077] -ZP: Zero Power

[0078] Overall system

[0079] As more communication devices require higher capacity, there has been a demand for improved mobile broadband communications compared to existing radio access technologies (RATs). In addition, large-scale MTC (machine type communication) that provides various services anytime and anywhere by connecting multiple devices and things is also one of the main issues to be considered in the next generation of communications. In addition, the design of communication systems considering services / terminals that are sensitive to reliability and latency is also discussed. Therefore, the introduction of next-generation RATs considering eMBB (enhanced mobile broadband communication), mMTC (massive MTC), URLLC (ultra-reliable low-latency communication), etc. is discussed, and for convenience, the corresponding technology is referred to as NR in this disclosure. NR is an expression representing an example of 5G RAT.

[0080] The new RAT system including NR uses an OFDM transmission method or a transmission method similar thereto. The new RAT system may follow OFDM parameters different from those of LTE. Alternatively, the new RAT system follows the parameters of the existing LTE / LTE-A as is, but may support a wider system bandwidth (e.g., 100 MHz). Alternatively, a cell may support multiple parameter sets. In other words, terminals operating according to different parameter sets may coexist in one cell.

[0081] A parameter set corresponds to one subcarrier spacing in the frequency domain. As the reference subcarrier spacing is scaled by an integer N, different parameter sets can be defined.

[0082] Figure 1 The structure of a wireless communication system to which the present disclosure can be applied is illustrated.

[0083] Reference Figure 1 , NG-RAN is configured with gNBs that provide the control plane (RRC) protocol side for the NG-RA (NG Radio Access) user plane (i.e., the new AS (Access Stratum) sublayer / PDCP (Packet Data Convergence Protocol) / RLC (Radio Link Control) / MAC / PHY) and the UE. The gNBs are interconnected through the Xn interface. In addition, the gNBs are connected to the NGC (Next Generation Core) through the NG interface. More specifically, the gNB is connected to the AMF (Access and Mobility Management Power) through the N2 interface, and to the UPF (User Plane Function) through the N3 interface.

[0084] Figure 2 The frame structure in a wireless communication system to which the present disclosure can be applied is illustrated.

[0085] The NR system may support multiple parameter sets. Here, the parameter set may be defined by subcarrier spacing and cyclic prefix (CP) overhead. Here, multiple subcarrier spacings may be derived by scaling the basic (reference) subcarrier spacing by an integer N (or, μ). In addition, although it is assumed that very low subcarrier spacings are not used in very high carrier frequencies, the parameter set used may be selected independently of the frequency band. In addition, various frame structures according to multiple parameter sets may be supported in the NR system.

[0086] In the following, OFDM parameter sets and frame structures that can be considered in the NR system are described. Multiple OFDM parameter sets supported in the NR system can be defined as shown in Table 1 below.

[0087] [Table 1]

[0088] μ <![CDATA[Δf=2 μ ·15[kHz]]]> CP 0 15 normal 1 30 normal 2 60 Normal, Extended 3 120 normal 4 240 normal

[0089] NR supports multiple parameter sets (or subcarrier spacing (SCS)) for supporting various 5G services. For example, when the SCS is 15kHz, the wide area of ​​the traditional cellular band is supported; and when the SCS is 30kHz / 60kHz, dense cities, lower latency and wider carrier bandwidth are supported; and when the SCS is 60kHz or higher, bandwidths exceeding 24.25GHz are supported to overcome phase noise. The NR band is defined as two types of frequency ranges (FR1, FR2). FR1 and FR2 can be configured as shown in Table 2 below. In addition, FR2 can mean millimeter wave (mmW).

[0090] [Table 2]

[0091] Frequency range specification Corresponding frequency range Subcarrier spacing FR1 410MHz–7125MHz 15,30,60kHz FR2 24250MHz–52600MHz 60,120,240kHz

[0092] Regarding the frame structure in the NR system, the sizes of various fields in the time domain are expressed as T c =1 / (Δf max ·N f ) is a multiple of the time unit. Here, Δf max 480·10 3 Hz, and N f is 4096. Downlink and uplink transmissions are configured (organized) to have duration T f =1 / Δf max N f / 100)·T c =10ms radio frame. Here, the radio frame is configured with 10 subframes, each of which has T sf =(Δf max N f / 1000)·T c =1 ms duration. In this case, there may be one frame set for the uplink and one frame set for the downlink. Furthermore, the transmission in the i-th uplink frame from the terminal should start T earlier than the corresponding downlink frame in the corresponding terminal. TA =(N TA +N TA,offset )T c For subcarrier spacing configuration μ, the time slots are arranged in n subframes. s μ ∈{0,...,N slot subframe,μ -1} and in the radio frame the number is incremented by n s,f μ ∈{0,...,N slot frame,μ -1}. A time slot is configured with N symb slotconsecutive OFDM symbols, and N symb slot Determined according to CP. Time slot n in a subframe s μ The beginning of the OFDM symbol n in the same subframe s μ N symb slot All terminals may not perform transmission and reception at the same time, which means that all OFDM symbols of a downlink time slot or an uplink time slot may not be used. Table 3 shows the number of OFDM symbols per time slot in a normal CP (N symb slot ), the number of time slots per radio frame (N slot frame,μ ) and the number of time slots per subframe (N slot subframe,μ ), and Table 4 represents the number of OFDM symbols per slot, the number of slots per radio frame, and the number of slots per subframe in the extended CP.

[0093] [Table 3]

[0094] μ <![CDATA[N symb slot ]]> <![CDATA[N slot frame,μ ]]> <![CDATA[N slot subframe,μ ]]> 0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

[0095] [Table 4]

[0096] μ <![CDATA[N symb slot ]]> <![CDATA[N slot frame,μ ]]> <![CDATA[N slot subframe,μ ]]> 2 12 40 4

[0097] Figure 2 is an example of μ=2 (SCS is 60kHz), see Table 3, 1 subframe can include 4 time slots. Figure 2 1 subframe = {1, 2, 4} shown in is an example, and the number of time slots that can be included in 1 subframe is defined in Table 3 or Table 4. In addition, a micro-time slot may include 2, 4, or 7 symbols or more or less symbols. Regarding physical resources in the NR system, antenna ports, resource grids, resource elements, resource blocks, carrier parts, etc. may be considered. Hereinafter, the physical resources that may be considered in the NR system will be described in detail.

[0098] First, with respect to antenna ports, the antenna ports are defined so that the channel carrying the symbol in the antenna port can be inferred from the channel carrying the other symbol in the same antenna port. When the large-scale properties of the channel on which the symbol in one antenna port is carried can be inferred from the channel carrying the symbol of another antenna port, the two antenna ports can be said to be in a QC / QCL (quasi-co-located or quasi-co-located) relationship. In this case, the large-scale properties include at least one of delay spread, Doppler spread, frequency shift, average received power, and receive timing.

[0099] Figure 3A resource grid in a wireless communication system to which the present disclosure can be applied is illustrated.

[0100] Reference Figure 3 , exemplarily describing a resource grid configuration with N in the frequency domain RB μ N sc RB subcarriers, and one subframe is configured with 14·2 μ OFDM symbols, but not limited to this. In the NR system, the transmitted signal consists of 2 μ N symb (μ) OFDM symbols and N RB μ N sc RB Here, N RB μ ≤N RB max,μ . N RB max,μ represents the maximum transmission bandwidth, which may differ between uplink and downlink and between parameter sets. In this case, one resource grid can be configured for each μ and antenna port p. Each element of the resource grid for μ and antenna port p is called a resource element and is uniquely identified by an index pair (k, l'). Here, k = 0, ..., N RB μ N sc RB -1 is the index in the frequency domain, and l'=0,...,2 μ N symb (μ) -1 refers to the symbol position in the subframe. When referencing a resource element in a slot, an index pair (k, l) is used.

[0101] Here, l = 0, ..., N symb μ -1. The resource element (k, l') for μ and antenna port p corresponds to the complex value a k,l' (p,μ) When there is no risk of aliasing or when no specific antenna port or parameter set is specified, the indices p and μ may be dropped and the complex value may be ak,l'(p) or ak,l'. In addition, a resource block (RB) is defined as N in the frequency domain. sc RB =12 consecutive subcarriers.

[0102] Point A serves as a common reference point for the resource block grid and is obtained as follows.

[0103] -OffsetToPointA for the primary cell (PCell) downlink represents the frequency offset between point A and the lowest subcarrier of the lowest resource block overlapping the SS / PBCH block used by the terminal for initial cell selection. Assuming a subcarrier spacing of 15kHz for FR1 and a subcarrier spacing of 60kHz for FR2, it is expressed in resource blocks.

[0104] -absoluteFrequencyPointA represents the frequency position of point A, expressed in ARFCN (Absolute Radio Frequency Channel Number).

[0105] For subcarrier spacing configuration μ, the common resource blocks are numbered from 0 upwards in the frequency domain. The center of subcarrier 0 of common resource block 0 for subcarrier spacing configuration μ is the same as "point A". Common resource block number n for subcarrier spacing configuration μ in the frequency domain CRB μ The relationship between and resource element (k, l) is given as in Equation 1 below.

[0106] [Equation 1]

[0107]

[0108] In Equation 1, k is defined relative to point A, so that k=0 corresponds to a subcarrier centered at point A. Physical resource blocks are spaced from 0 to N in a bandwidth part (BWP). BWP,i size,μ -1 numbering and i is the number of BWP. Physical resource block n in BWPi PRB and public resource block n CRB The relationship between is given by the following equation 2.

[0109] [Equation 2]

[0110]

[0111] is the common resource block where the BWP starts relative to common resource block 0.

[0112] Figure 4 The physical resource blocks in the wireless communication system to which the present disclosure can be applied are illustrated. Figure 5 The time slot structure in a wireless communication system to which the present disclosure can be applied is illustrated.

[0113] Reference Figure 4 and Figure 5 , a slot includes a plurality of symbols in the time domain. For example, for a normal CP, 1 slot includes 7 symbols, but for an extended CP, 1 slot includes 6 symbols.

[0114] A carrier includes multiple subcarriers in the frequency domain. An RB (resource block) is defined as multiple (e.g., 12) consecutive subcarriers in the frequency domain. A BWP (bandwidth part) is defined as multiple consecutive (physical) resource blocks in the frequency domain and may correspond to a parameter set (e.g., SCS, CP length, etc.). A carrier may include up to N (e.g., 5) BWPs. Data communication may be performed through an activated BWP, and only one BWP may be activated for a terminal. In a resource grid, each element is called a resource element (RE) and may map a complex symbol.

[0115] In the NR system, each component carrier (CC) can support up to 400MHz. If a terminal operating in such a wideband CC always operates to turn on the radio frequency (FR) chip for the entire CC, the terminal battery consumption may increase. Alternatively, when considering multiple application scenarios operating in a wideband CC (e.g., eMBB, URLLC, Mmtc, V2X, etc.), different parameter sets (e.g., subcarrier spacing, etc.) can be supported in each frequency band in the corresponding CC. Alternatively, each terminal may have different capabilities for the maximum bandwidth. Taking this into account, the base station can instruct the terminal to operate only in part of the bandwidth instead of the full bandwidth of the wideband CC, and for convenience, the corresponding partial bandwidth is defined as a bandwidth part (BWP). The BWP can be configured with continuous RBs on the frequency axis and can correspond to a parameter set (e.g., subcarrier spacing, CP length, slot / microslot duration).

[0116] At the same time, even in one CC configured to the terminal, the base station can configure multiple BWPs. For example, a BWP occupying a relatively small frequency domain can be configured in the PDCCH monitoring time slot, and the PDSCH indicated by the PDCCH can be scheduled in a larger BWP. Alternatively, when the UE is congested in a specific BWP, other BWPs can be configured for some terminals for load balancing. Alternatively, considering the frequency domain inter-cell interference elimination between adjacent cells, etc., some full-bandwidth intermediate spectrums can be excluded, and BWPs on two edges can be configured in the same time slot. In other words, the base station can configure at least one DL / UL BWP to a terminal associated with a broadband CC. The base station can activate at least one DL / UL BWP in the configured DL / UL BWP at a specific time (via L1 signaling or MAC CE (control element) or RRC signaling, etc.). In addition, the base station can indicate switching to other configured DL / UL BWPs (via L1 signaling or MAC CE or RRC signaling, etc.). Alternatively, based on a timer, when the timer value expires, it can switch to a determined DL / UL BWP. Here, the activated DL / UL BWP is defined as the active DL / UL BWP. However, when the terminal performs the initial access procedure or establishes the RRC connection before, the configuration on the DL / UL BWP may not be received, so the DL / UL BWP assumed by the terminal in these cases is defined as the initial active DL / UL BWP.

[0117] Figure 6 Physical channels used in a wireless communication system to which the present disclosure can be applied and a general signal transmission and reception method using the physical channels are illustrated.

[0118] In a wireless communication system, a terminal receives information from a base station through a downlink and transmits information to the base station through an uplink. The information sent and received by the base station and the terminal includes data and various control information, and there are various physical channels according to the type / purpose of the information they send and receive.

[0119] When the terminal is turned on or newly enters a cell, it performs an initial cell search including synchronization with a base station (S601). For the initial cell search, the terminal can synchronize with the base station by receiving a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the base station, and obtain information such as a cell identifier (ID). Then, the terminal can obtain broadcast information in the cell by receiving a physical broadcast channel (PBCH) from the base station. At the same time, the terminal can check the downlink channel status by receiving a downlink reference signal (DLRS) in the initial cell search phase.

[0120] The terminal that has completed the initial cell search may obtain more detailed system information by receiving a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) according to information carried in the PDCCH (S602).

[0121] Meanwhile, when the terminal accesses the base station for the first time or has no radio resources for signal transmission, it may perform a random access (RACH) procedure (S603 to S606) on the base station. For the random access procedure, the terminal may send a specific sequence as a preamble through a physical random access channel (PRACH) (S603 and S605), and may receive a response message to the preamble through a PDCCH and a corresponding PDSCH (S604 and S606). The contention-based RACH may additionally perform a contention resolution procedure.

[0122] The terminal that subsequently performs the above process may perform PDCCH / PDSCH reception (S607) and PUSCH (Physical Uplink Shared Channel) / PUCCH (Physical Uplink Control Channel) transmission (S608) as a general uplink / downlink signal transmission process. Specifically, the terminal receives downlink control information (DCI) through PDCCH. Here, DCI includes control information such as resource allocation information for the terminal, and the format varies according to its purpose of use.

[0123] At the same time, the control information sent by the terminal to the base station through the uplink or received by the terminal from the base station includes downlink / uplink ACK / NACK (acknowledgement / non-acknowledgement) signal, CQI (channel instruction indicator), PMI (precoding matrix indicator), RI (rank indicator), etc. For the 3GPP LTE system, the terminal can send the above-mentioned CQI / PMI / RI and other control information through PUSCH and / or PUCCH.

[0124] Table 5 shows an example of the DCI format in the NR system.

[0125] [Table 5]

[0126]

[0127] Referring to Table 5, DCI formats 0_0, 0_1 and 0_2 may include resource information (e.g., UL / SUL (supplementary UL), frequency resource allocation, time resource allocation, frequency hopping, etc.), information related to transport blocks (TBs) (e.g., MCS (modulation and coding scheme), NDI (new data indicator), RV (redundancy version)), etc.), information related to HARQ (Hybrid-Automatic Repeat and Request) (e.g., process number, DAI (downlink assignment index), PDSCH-HARQ feedback timing, etc.), information related to multiple antennas (e.g., DMRS sequence initialization information, antenna port, CSI request, etc.), power control information related to the scheduling of PUSCH (e.g., PUSCH power control, etc.), and the control information included in each DCI format may be predefined.

[0128] DCI format 0_0 is used to schedule PUSCH in one cell. Information included in DCI format 0_0 is CRC (Cyclic Redundancy Check) scrambled by C-RNTI (Cell Radio Network Temporary Identifier) ​​or CS-RNTI (Configured Scheduling RNTI) or MCS-C-RNTI (Modulation Coding Scheme Cell RNTI) and transmitted.

[0129] DCI format 0_1 ​​is used to indicate the scheduling of one or more PUSCHs or to configure grant (CG) downlink feedback information to a terminal in a cell. The information included in DCI format 0_1 ​​is scrambled and transmitted by C-RNTI or CS-RNTI or SP-CSI-RNTI (semi-persistent CSIRNTI) or MCS-C-RNTI.

[0130] DCI format 0_2 is used to schedule PUSCH in one cell. Information included in DCI format 0_2 is scrambled and transmitted by C-RNTI, CS-RNTI, SP-CSI-RNTI, or MCS-C-RNTI.

[0131] Next, DCI formats 1_0, 1_1 and 1_2 may include resource information (e.g., frequency resource allocation, time resource allocation, VRB (virtual resource block) -PRB (physical resource block) mapping, etc.), information related to transport blocks (TBs) (e.g., MCS, NDI, RV, etc.), information related to HARQ (e.g., process number, DAI, PDSCH-HARQ feedback timing, etc.), information related to multiple antennas (e.g., antenna ports, TCI (transmission configuration indicator), SRS (sounding reference signal) request, etc.), information related to PUCCH scheduling regarding PDSCH (e.g., PUCCH power control, PUCCH resource indicator, etc.), and the control information included in each DCI format may be predefined.

[0132] DCI format 1_0 is used to schedule PDSCH in one DL cell. Information included in DCI format 1_0 is CRC scrambled and transmitted by C-RNTI or CS-RNTI or MCS-C-RNTI.

[0133] DCI format 1_1 is used to schedule PDSCH in one cell. Information included in DCI format 1_1 is CRC scrambled and transmitted by C-RNTI or CS-RNTI or MCS-C-RNTI.

[0134] DCI format 1_2 is used to schedule PDSCH in one cell. Information included in DCI format 1_2 is CRC scrambled and transmitted by C-RNTI, CS-RNTI, or MCS-C-RNTI.

[0135] V2X (Vehicle to Everything) / Sidelink (SL) communication

[0136] Figure 7 A process of performing V2X or SL communication according to a transmission mode in a wireless communication system to which the present disclosure can be applied is illustrated.

[0137] Figure 7 The embodiments of the present disclosure may be combined with various embodiments of the present disclosure. In various embodiments of the present disclosure, the transmission mode may be referred to as a mode or a resource allocation mode. In the following, for ease of explanation, the transmission mode in LTE may be referred to as an LTE transmission mode, and the transmission mode in NR may be referred to as an NR resource allocation mode.

[0138] For example, Figure 7 (a) illustrates the operation of the UE related to LTE transmission mode 1 or LTE transmission mode 3. Alternatively, for example, Figure 7 (a) illustrates the operation of the UE related to NR resource allocation mode 1. For example, LTE transmission mode 1 can be applied to general SL communication, and LTE transmission mode 3 can be applied to V2X communication.

[0139] For example, Figure 7 (b) illustrates the operation of a UE associated with LTE transmission mode 2 or LTE transmission mode 4. Alternatively, for example, Figure 7 (b) illustrates the operation of a UE associated with NR resource allocation mode 2.

[0140] Reference Figure 7(a), in LTE transmission mode 1, LTE transmission mode 3, or NR resource allocation mode 1, the base station may schedule SL resources for UE to use for SL transmission (S8000). For example, the base station may send information related to SL resources and / or information related to UL resources to the first UE. For example, the UL resources may include PUCCH resources and / or PUSCH resources. For example, the UL resources may be resources for reporting SL HARQ feedback to the base station.

[0141] For example, the first UE may receive information related to dynamic grant (DG) resources and / or information related to configuration grant (CG) resources from the base station. For example, the CG resources may include CG type 1 resources or CG type 2 resources. In the present disclosure, DG resources may be resources that the base station configures / allocates to the first UE via DCI. In the present disclosure, CG resources may be (periodic) resources that the base station configures / allocates to the first UE via DCI and / or RRC messages. For example, in the case of CG type 1 resources, the base station may send an RRC message including information related to the CG resources to the first UE. For example, in the case of CG type 2 resources, the base station may send an RRC message including information related to the CG resources to the first UE, and the base station may send a DCI related to the activation or release of the CG resources to the first UE.

[0142] The first UE may send a PSCCH (eg, sidelink control information (SCI) or first-stage SCI) to the second UE based on resource scheduling (S8010).

[0143] The first UE may transmit a PSSCH (eg, a second stage SCI, a MAC protocol data unit (PDU), data, etc.) related to the PSCCH to the second UE (S8020).

[0144] The first UE may receive a PSFCH related to the PSCCH / PSSCH from the second UE (S8030). For example, HARQ feedback information (eg, NACK information or ACK information) may be received from the second UE via the PSFCH.

[0145] The first UE may send / report HARQ feedback information to the base station via PUCCH or PUSCH (S8040). For example, the HARQ feedback information reported to the base station may be information generated by the first UE based on the HARQ feedback information received from the second UE. For example, the HARQ feedback information reported to the base station may be information generated by the first UE according to a pre-set rule. For example, the DCI may be a DCI for scheduling a SL. For example, the format of the DCI may be DCI format 3_0 or DCI format 3_1.

[0146] Reference Figure 7(b), in LTE transmission mode 2, LTE transmission mode 4 or NR resource allocation mode 2, the UE can determine the SL resources set by the base station / network or the SL transmission resources within the preset SL resources. For example, the set SL resources or pre-configured SL resources can be a resource pool. For example, the UE can autonomously select or schedule resources for SL transmission. For example, the UE can perform SL communication by selecting resources by itself within the configured resource pool. For example, the UE can perform a sensing and resource (re)selection process to select resources by itself within the selection window. For example, sensing can be performed on a subchannel basis.

[0147] The first UE, which has selected resources in the resource pool, may send a PSCCH (eg, SCI or first-stage SCI) to the second UE using the resources ( S8010 ).

[0148] The first UE may send a PSSCH (eg, second stage SCI, MAC PDU, data, etc.) related to the PSCCH to the second UE (S8020).

[0149] The first UE may receive a PSFCH related to the PSCCH / PSSCH from the second UE ( S8030 ).

[0150] Reference Figure 7 (a) or Figure 7 (b), for example, the first UE may send SCI to the second UE on the PSCCH. Alternatively, for example, the first UE may send two consecutive SCIs (e.g., second-stage SCI) to the second UE on the PSCCH and / or PSSCH. In this case, the second UE may decode two consecutive SCIs (e.g., second-stage SCI) to receive the PSSCH from the first UE. In the present disclosure, the SCI sent on the PSCCH may be referred to as the first (first) SCI, the first SCI, the first-stage SCI, or the first-stage SCI format, and the SCI sent on the PSSCH may be referred to as the second (second) SCI, the second SCI, the second-stage SCI, or the second-stage SCI format. For example, the first-stage SCI format may include SCI format 1-A, and the second-stage SCI format may include SCI format 2-A and / or SCI format 2-B.

[0151] Reference Figure 7 (a) or Figure 7 (b), in step S8030, the first UE may receive the PSFCH based on the following description. For example, the first UE and the second UE may determine the PSFCH resources based on the following description, and the second UE may send HARQ feedback to the first UE using the PSFCH resources.

[0152] Describes the UE procedure for reporting HARQ-ACK on the sidelink as specified in TS 38.213.

[0153] The UE may be instructed to send a PSFCH including HARQ-ACK information in response to PSSCH reception in an SCI format through scheduling PSSCH reception. The UE provides HARQ-ACK information including ACK or NACK or only NACK.

[0154] A number of time slots within a resource pool may be provided to the UE during the period of the PSFCH transmission opportunity resource indicated by sl-PSFCH-Period. If the number of time slots is 0, PSFCH transmission within the resource pool is disabled for the UE.

[0155] If k mod N PSSCH PSFCH =0, then the UE expects time slot t' k SL (0≤k <T' max ) includes PSFCH transmission opportunity resources, where t' k SL Defined in TS 38.214, T' max is the number of time slots belonging to the resource pool within 10240 ms according to TS 38.214, and N PSSCH PSFCH Provided by sl-PSFCH-Period.

[0156] The UE may be instructed by higher layers not to send a PSFCH containing HARQ-ACK information in response to receiving a PSSCH.

[0157] The UE provides HARQ-ACK information in a PSFCH transmission from the resource pool when the UE receives a PSSCH from the resource pool and the HARQ Feedback Enable / Disable Indicator field of the associated SCI format 2-A / 2-B / 2-C has a value of 1. The UE sends the PSFCH in a first slot that includes PSFCH resources and corresponds to at least a number of slots provided by sl-MinTimeGapPSFCH of the resource pool after the last slot of PSSCH reception.

[0158] The UE may be provided with a physical resource block (PRB) in the resource pool indicated by sl-PSFCH-RB-Set. PRB,set PSFCH A set of PRBs in a resource pool indicated by sl-RB-SetPSFCH may be provided to the UE. PRB,setPSFCH A set of PRBs for PSFCH transmission including contention information. The UE expects to (pre)set different PRBs for contention information and HARQ-ACK information. For the resource pool N provided by sl-NumSubchannel SUBCH The number of subchannels and less than or equal to N PSSCH PSFCH The number of PSSCH time slots associated with the PSFCH time slots, the UE allocates the PSFCH time slots and PSSCH time slots associated with subchannel j to time slot i from M PRB,set PSFCH PRB [(i+j N PSSCH PSFCH )M subch,slot' PSFCH (i+1+j N PSSCH PSFCH )M subch,slot PSFCH -1] PRB. Here, M subch,slot PSFCH =M PRB,set PSFCH / (N subch N PSSCH PSFCH ), 0≤i <N PSSCH PSFCH , 0≤j <N subch , and the allocation starts in ascending order of i and continues in ascending order of j. The UE expects M PRB，set PSFCH N subch ·N PSSCH PSFCH multiples of.

[0159] The UE determines the number of available PSFCH resources for multiplexing HARQ-ACK or conflicting information in PSFCH transmission as R based on the indication of sl-PSFCH-CandidateResourceType. PRB,CS PSFCH =N type PSFCH ·M subch,slot PSFCH ·N CS PSFCH , where N CS PSFCH is the number of cyclic shift pairs in the resource pool provided by sl-NumMuxCS-Pair.

[0160] -When sl-PSFCH-CandidateResourceType is set to startSubCH, N typePSFCH =1, and M subch,slot PSFCH The PRBs are associated with the starting subchannel of the corresponding PSSCH.

[0161] -When sl-PSFCH-CandidateResourceType is set to allocSubCH, N type PSFCH =N subch PSSCH , and N subch PSSCH ·M subch,slot PSFCH PRBs and corresponding PSSCH N subch PSSCH sub-channels are associated.

[0162] -For conflicting information, the corresponding PSSCH is determined based on sl-PSFCH-Occasion.

[0163] PSFCH resources are first allocated in ascending order of PRB index from N type PSFCH ·M subch,slot PSFCH PRB indices, and then in ascending order of cyclic shift indexes from N CS PSFCH Rotate the pair index.

[0164] The UE determines the index of the PSFCH resource for transmitting the PSFCH including the HARQ-ACK information or the contention information in response to the PSSCH reception as (P ID +M ID )mod RPRB,CS PSFCH , which corresponds to the reserved resources. Here, P ID The physical layer source identifier provided by SCI format 2-A / 2-B / 2-C for scheduling PSSCH reception or SCI format 2-A / 2-B / 2-C for reserving resources for conflicting information to be provided from other UEs. For HARQ-ACK information, if the UE detects SCI format 2-A with a broadcast type indicator field value of "01", M ID M is the identifier of the UE receiving the PSSCH indicated by the upper layer, otherwise ID is 0. For conflicting information, M ID is 0.

[0165] For PSFCH transmissions including HARQ-ACK information or contention information, the UE uses the following Table 6 to obtain the cyclic shift pair index and N corresponding to the PSFCH resource index: CS PSFCHThe value m0 is determined to calculate the value α of the cyclic shift.

[0166] Table 6 illustrates a set of cyclic shift pairs.

[0167] [Table 6]

[0168]

[0169] For PSFCH transmission including HARQ-ACK information, if the UE detects SCI format 2-A or SCI format 2-C with a broadcast type indicator field value of "01" or "10" to calculate the value of the cyclic shift α, the UE determines m as shown in Table 7 below cs value, and if the UE detects SCI format 2-B or 2-A with a broadcast type indicator field value of "11", the UE determines m as shown in the following Table 8 cs For PSFCH transmission including collision information, the UE determines m as shown in Table 9 below cs The UE applies one cyclic shift from the cyclic shift pair to the sequence for PSFCH transmission. Table 7 illustrates the mapping of the cyclic shift of the sequence for PSFCH transmission from the cyclic shift pair to the HARQ-ACK information bit value when the HARQ-ACK information includes ACK or NACK.

[0170] [Table 7]

[0171] HARQ-ACK value 0(NACK) 1(ACK) Sequential cyclic shift 0 6

[0172] Table 8 illustrates the mapping of cyclic shifts of a sequence for PSFCH transmission from a cyclic shift pair to HARQ-ACK information bit values ​​when the HARQ-ACK information contains only NACK.

[0173] [Table 8]

[0174] HARQ-ACK value 0(NACK) 1(ACK) Sequential cyclic shift 0 N / A

[0175] Table 9 illustrates the mapping of cyclic shifts and collision information bit values ​​of sequences for PSFCH transmission from cyclic shift pairs.

[0176] [Table 9]

[0177] Conflicting Information Conflict information of the next reserved resource in SCI Sequence cyclic shift 0

[0178] Figure 8 The broadcast types used for V2X or SL communication in a wireless communication system to which the present disclosure can be applied are illustrated. Figure 8 The embodiments of can be combined with various embodiments of the present disclosure. Figure 8 , Figure 8(a) indicates broadcast type SL communication, Figure 8 (b) indicates unicast type SL communication, Figure 8 (c) represents multicast type SL communication. In the case of unicast type SL communication, the UE can communicate one-to-one with another UE. In the case of multicast type SL communication, the UE can perform SL communication with one or more UEs in the group to which it belongs. In various embodiments of the present disclosure, SL multicast communication may be referred to as SL multicast communication, SL one-to-many communication, etc.

[0179] Hereinafter, a HARQ (Hybrid Automatic Repeat Request) process is described.

[0180] For example, SL HARQ feedback may be enabled for unicast. In this case, in non-code block group (CBG) operation, if the receiving UE decodes a PSCCH targeted to the receiving UE and the receiving UE successfully decodes a transport block associated with the PSCCH, the receiving UE may generate an ACK. The receiving UE may then send a HARQ-ACK to the transmitting UE. On the other hand, if the receiving UE fails to successfully decode a transport block associated with the PSCCH after decoding the PSCCH targeted to the receiving UE, the receiving UE may generate a NACK. The receiving UE may then send a NACK to the transmitting UE.

[0181] In addition, for example, SL HARQ feedback may be enabled for multicast. For example, in non-CBG operation, two HARQ feedback options may be supported for multicast.

[0182] (1) Multicast Option 1: If the receiving UE fails to decode the transmission associated with the PSCCH after decoding the PSCCH targeted at the receiving UE, the receiving UE may send a NACK to the transmitting UE via the PSFCH. On the other hand, if the receiving UE decodes the PSCCH targeted at the receiving UE and the receiving UE successfully decodes the transport block associated with the PSCCH, the receiving UE may not send an ACK to the transmitting UE.

[0183] (2) Multicast Option 2: If the receiving UE fails to decode the transport block associated with the PSCCH after decoding the PSCCH targeted to the receiving UE, the receiving UE may send a NACK to the sending UE via the PSFCH. Then, if the receiving UE decodes the PSCCH targeted to the receiving UE and the receiving UE successfully decodes the transport block associated with the PSCCH, the receiving UE may send an ACK to the sending UE via the PSFCH.

[0184] For example, if multicast option 1 is used for SL HARQ feedback, all UEs performing multicast communication may share PSFCH resources. For example, UEs belonging to the same group may use the same PSFCH resources to send HARQ feedback.

[0185] For example, if multicast option 2 is used for SL HARQ feedback, each UE performing multicast communication may use different PSFCH resources for HARQ feedback transmission. For example, UEs belonging to the same group may use different PSFCH resources to send HARQ feedback.

[0186] In the present disclosure, ACK may be referred to as HARQ-ACK, ACK information, or positive ACK information, and NACK may be referred to as HARQ-NACK, NACK information, or negative ACK information.

[0187] The sidelink grant may be semi-persistently configured by RRC or dynamically received on PDCCH, which is autonomously selected by the MAC entity. The MAC entity may have a sidelink grant on an active SL BWP to determine the set of PSCCH periods in which SCI transmissions occur and the set of PSSCH periods in which SL-SCH transmissions associated with SCI occur.

[0188] When the MAC entity is configured for sidelink resource allocation mode 1, the MAC entity may perform actions based on each PDCCH opportunity and each grant received for that PDCCH opportunity.

[0189] UE / base station behavior for consistent LBT failure in SL transmission

[0190] NR Unlicensed (NR-U) refers to a mode that provides the technology required by cellular operators to integrate unlicensed spectrum into their wireless communication systems. NR-U enables uplink and downlink operations in unlicensed spectrum.

[0191] In NR-U, channel access for uplink and downlink relies on LBT functionality. The UE and / or base station may first sense the communication channel before transmission to determine whether there is no communication. If the communication channel is a broadband unlicensed carrier, the channel sensing process of NR-U may rely on sensing energy levels in multiple subbands of the communication channel. The base station may configure LBT parameters (e.g., type / duration, idle channel assessment parameters, etc.) for the UE.

[0192] In NR-U, the UE can determine the time and location of transmission and reception based on the indication of the COT (channel occupancy time) structure. The COT consists of multiple time slots, and each time slot can consist of downlink resources, uplink resources or flexible resources.

[0193] In the NR-U system, both continuous uplink resource allocation and interleaved uplink resource allocation can be supported while complying with regulations. In interleaved uplink resource allocation, the basic unit of resource allocation for NR unlicensed channels can be an interlace. For example, a single interlace can consist of ten equally spaced resource blocks within a 20 MHz frequency bandwidth for a 15 kHz subcarrier spacing.

[0194] For NR-U, the physical layer may perform an LBT process. The LBT process refers to a process of not performing transmission when determining that a channel is occupied. If the channel is identified as occupied according to the LBT process, the physical layer may not perform transmission. If the physical layer performs an LBT process before transmission and does not perform transmission, the physical layer may send an LBT failure indication to the MAC entity.

[0195] Unless otherwise specified, the operations specified in the present disclosure may be performed regardless of whether an LBT failure indication is received from the physical layer when performing an LBT process for transmission. If the physical layer does not perform LBT, an LBT failure indication may not be received from the physical layer.

[0196] When SL transmission is supported in an unlicensed band, the UE can perform LBT for SL transmission. Here, LBT failure can occur not only in UL transmission but also in SL transmission. When SL mode 2 is configured, the UE can autonomously (re)select SL resources for SL transmission. In this case, when continuous LBT failures occur in SL transmission, there is no method defined in the basic wireless communication system for avoiding LBT failure of SL transmission (for example, LBT failure for SL transmission when SL mode 2 is configured).

[0197] Hereinafter, operations of a terminal / base station when consecutive LBT failures occur for SL transmission are described.

[0198] exist Fig. 9 In the example, for ease of explanation, the side link Tx (transmitting) UE is referred to as the first UE, and the side link Rx (receiving) UE is referred to as the second UE. Fig. 9 In the present invention, the sidelink operation between the first UE and the second UE can be operated in an unlicensed band / spectrum or a shared spectrum.

[0199] Fig. 9 is a diagram for explaining a process in which a first UE performs communication according to one embodiment of the present disclosure.

[0200] The first UE may receive first configuration information related to a sidelink (SL) specific LBT (Listen Before Talk) failure detection timer (eg, 'sl-lbt-FailureDetectionTimer') and second configuration information related to a SL specific LBT failure counter from a base station (S910).

[0201] For example, the first UE may receive, from the base station, first configuration information and second configuration information included in upper layer signaling (eg, RRC signaling) related to SL-specific LBT failure recovery.

[0202] For example, the second configuration information may include information related to the maximum number of SL-specific LBT failure instances (i.e., SL-specific maximum LBT failure instance count threshold) for consistent SL-specific LBT detection (e.g., 'sl-lbt-FailureInstanceMaxCount') and / or a counter counting SL-specific failure indications (e.g., 'SL_LBT_COUNTER').

[0203] For example, a SL-specific failure detection timer and a SL-specific LBT failure counter may be configured for the first UE in each serving cell.

[0204] Based on the SL-specific failure detection timer and the SL-specific LBT failure counter, the first UE may trigger a consistent SL-specific LBT failure ( S920 ).

[0205] For example, a SL-specific LBT failure may be triggered based on a SL-specific failure detection timer and a SL-specific LBT failure counter for at least one of one or more RB sets or one or more resource pools.

[0206] Specifically, when an LBT failure indication is received from the lower layer, when the SL-specific failure detection timer is (re)started, the SL-specific LBT failure counter value may be increased by 1. If the SL-specific LBT failure counter value is greater than or equal to the SL-specific maximum LBT failure instance count threshold, the first terminal may trigger a consistent SL-specific LBT failure (for activated SL BWPs within the serving cell).

[0207] Here, based on resetting at least one of the SL-specific failure detection timer and the SL-specific LBT failure counter for the UE, the value of the SL-specific failure detection timer may be set to 0. In addition, based on expiration of the SL-specific failure detection timer, the value of the SL-specific failure detection timer may be set to 0.

[0208] The first UE may release the SL connection between the second UE and the first UE associated with the triggered consistent SL specific LBT failure (S930).

[0209] For example, the SL connection between the second UE may include a PC5-RRC connection and / or a unicast sidelink connection.

[0210] The first UE may send information indicating at least one of a triggered consistent SL-specific LBT failure or a release of the SL connection to the base station (S940).

[0211] For example, the first UE may send higher layer signaling (e.g., a PC5-RRC release message) to the second UE, the higher layer signaling including information for releasing the SL connection between the second UEs associated with the SL-specific LBT failure, thereby releasing the SL connection between the second UEs.

[0212] Additionally or alternatively, the first UE may send information indicating at least one of a triggered consistent SL-specific LBT failure or a release of the SL connection to the base station via the PUCCH by triggering a scheduling request (SR).

[0213] As another example, the first UE may send information indicating the release of the SL connection to the base station through upper layer signaling related to the sidelink UE information (eg, 'SidelinkUEInformation').

[0214] As another example, the first UE may send information to the base station via a MAC CE indicating a triggered consistent SL specific LBT failure. If the SL LBT failure granularity is SL BWP, the UE may declare SL RLF (radio link failure) and existing RRC messages may be used to indicate SL RLF to all other UEs connected to it.

[0215] As another example, if the SL LBT failure granularity is resource pool / RB set, if the UE triggers a consistent SL LBT failure across all resource pools / RB sets, the UE may trigger SL RLF for connections of all other terminals.

[0216] Depend on Fig. 9 The method performed by the first UE described in the example may be performed by Fig.13 The first device (100) executes.

[0217] For example, Fig.13One or more processors (102) of the first device (100) may be configured to receive first configuration information related to a SL-specific LBT failure detection timer and second configuration information related to a SL-specific LBT failure counter from a base station through one or more transceivers (106). One or more processors (102) may be configured to trigger a consistent SL-specific LBT failure based on the SL-specific failure detection timer and the SL-specific LBT failure counter, and release a SL connection between a second terminal associated with the triggered consistent SL-specific LBT failure. One or more processors (102) may be configured to send information indicating at least one of the triggered consistent SL-specific LBT failure or the release of the SL connection to the base station through one or more transceivers (106).

[0218] In addition, the one or more memories (104) of the first device (100) may store commands that, when executed by the one or more processors (102), are used to perform Fig. 9 The method described in the example.

[0219] Fig.10 is a diagram for explaining a process in which a base station performs communication according to one embodiment of the present disclosure.

[0220] The base station may send first configuration information related to a SL-specific LBT failure detection timer and second configuration information related to a SL-specific LBT failure counter to the first UE (S1010).

[0221] Already referenced Fig. 9 Features related to the first configuration information and the second configuration information are described, and thus any repeated description will be omitted.

[0222] The base station may receive information indicating at least one of the following items from the first UE: i) a consistent SL-specific LBT failure triggered by the first UE, or ii) a release of the SL connection between the first UE and the second UE (S1020).

[0223] Here, the first UE can trigger a consistent SL-specific LBT failure based on the SL-specific failure detection timer and the SL-specific LBT failure counter. Then, the SL connection between the second UE and the first UE related to the triggered consistent SL-specific LBT failure can be released. That is, the base station can receive a report from the first UE that the SL connection between the first UE and the second UE is released due to a consistent SL-specific LBT failure.

[0224] Depend on Fig.10 The method performed by the base station described in the example may be performed by Fig.13 The second device (200) is executed.

[0225] For example, Fig.13 One or more processors (202) of the second device (200) may be configured to send first configuration information related to a SL-specific LBT failure detection timer and second configuration information related to a SL-specific LBT failure counter to the first terminal via one or more transceivers (206). One or more processors (202) may be configured to receive information indicating at least one of the following items from the first UE via one or more transceivers (206): i) a consistent SL-specific LBT failure triggered by the first terminal, or ii) a release of a SL connection between the first terminal and the second UE.

[0226] In addition, one or more memories (204) of the second device (200) may store instructions that, when executed by one or more processors (202), are used to perform Fig.10 The method described in the example.

[0227] Fig.11 is a diagram for explaining a method for performing resource reselection for a side link based on LBT failure according to one embodiment of the present disclosure.

[0228] Fig.11 The examples are for convenience of explanation and do not limit the scope of the present disclosure. Depending on the situation and / or setting, the Fig.11 In addition, Fig.11 The transmitting (Tx) terminal / receiving (Rx) terminal / base station in the embodiment are only examples and the following Fig.13 It is implemented by the device shown in .

[0229] For example, Fig.13 The processor (102 / 202) can control the use of the transceiver (106 / 206) to send and receive channels / signals / data / information, etc. In addition, Fig.13 The processor (102 / 202) can control the storage of channels / signals / data / information to be transmitted in the memory (104 / 204), and can also control the storage of received channels / signals / data / information in the memory (104 / 204).

[0230] The network (or base station) may transmit side link configuration information to a transmitting UE (ie, Tx UE) via system information or / and terminal-specific RRC signaling ( S1110 ).

[0231] When the sidelink configuration information is received from the network, one or more carriers and one or more resource pools may be configured for each carrier for at least one of the sidelink resource allocation mode 1 or mode 2 of the Tx UE.

[0232] Here, the number of HARQ processes may be configured based on each resource pool on each carrier. A resource pool may be used for uplink or sidelink transmission. Each resource pool may be associated with a pool index. The maximum number of HARQ processes per resource pool may be configured. The number of HARQ retransmissions may correspond to the number of each HARQ process and / or the SL RSRP or DL ​​RSRP measured by the (Tx)UE.

[0233] In the Tx UE, RRC can configure the MAC entity to sidelink resource allocation mode 2 to transmit using a resource pool of a carrier based on detection or random selection. The MAC entity (of the Tx UE) can then perform each sidelink process.

[0234] For example, the TX UE may establish a PC5-RRC connection with the RX UE for unicast SL transmission.

[0235] At step S1120, the (Tx)UE checks the transmission resource (re)selection, (re)selects the transmission resources for generating the selected side link grant, performs a channel access procedure with LBT type 1 or 2, and can generate a new MAC PDU for the selected side link grant within the interval of COT.

[0236] If the MAC entity (of the Tx UE) has chosen to generate a selected sidelink grant corresponding to the transmission of multiple MAC PDUs and there is SL data available on the logical channel; or

[0237] If the MAC entity chooses to generate the selected sidelink grant corresponding to the transmission of a single MAC PDU and there is SL data available on the logical channel or SL-CSI reporting is triggered;

[0238] If the MAC entity does not select a resource pool for the logical channel:

[0239] - If 'sl-HARQ-FeedbackEnabled' for a logical channel is set to enabled, the (Tx)UE selects a resource pool consisting of PSFCH resources from the resource pool;

[0240] - If 'sl-HARQ-FeedbackEnabled' for a logical channel is not set to enabled, the (Tx) UE may select a specific resource pool from the resource pools.

[0241] When the MAC entity in the (Tx)UE selects a new resource pool as described above or the MAC entity triggers Tx resource (re)selection, the MAC entity can perform TX resource (re)selection according to the transmission resource (re)selection method described below to generate a selected side link grant for the selected resource pool.

[0242] -The MAC entity may select one of the allowed values ​​configured by RRC in 'sl-ResourceReservePeriodList' and set the resource reservation interval (P rsvp_TX ) is set to the selected value;

[0243] - If the resource reservation interval is greater than or equal to 100 ms, the MAC entity may randomly select an integer value from the interval [5,15] with equal probability, or if the resource reservation interval is less than 100 ms, the MAC entity may randomly select an integer value from the interval Randomly select an integer value from and set SL_RESOURCE_RESELECTION_COUNTER to the selected value;

[0244] - The MAC entity selects the number of HARQ retransmissions from the allowed number configured by RRC in 'sl-MaxTxTransNumPSSCH' included in 'sl-PSSCH-TxConfigList', and if configured by RRC, it may be an overlap between 'sl-MaxTxTransNumPSSCH' indicated in 'sl-CBR-PriorityTxConfigList' and the CBR measured by lower layers (if CBR measurement results are available) for the highest priority logical channel allowed on the carrier, or it may overlap with the corresponding 'sl-defaultTxConfigIndex' configured by RRC (if CBR measurement results are not available);

[0245] -The MAC entity selects the amount of frequency resources within the range configured by RRC from among 'sl-MinSubChannelNumPSSCH' and 'sl-MaxSubchannelNumPSSCH' included in 'sl-PSSCH-TxConfigList', and if configured by RRC, it may overlap between 'MinSubChannelNumPSSCH' and 'MaxSubchannelNumPSSCH' indicated in 'sl-CBR-PriorityTxConfigList' and the CBR measured by the lower layer (if a CBR measurement result exists), or may overlap with the corresponding 'sl-defaultTxConfigIndex' configured by RRC.

[0246] -The MAC entity may arbitrarily select time and frequency resources from the resources indicated by the physical layer for a transmission opportunity, depending on the amount of selected frequency resources and the remaining PDBs of SL data available on the allowed logical channels on the carrier;

[0247] -The MAC entity may use the randomly selected resources to select a set of contiguous resources for transmission of PSCCH and PSSCH corresponding to multiple transmission opportunities of multiple MAC PDUs or one or more transmission opportunities of a single MAC PDU;

[0248] - If one or more HARQ retransmissions are selected and resources are still available for further transmission opportunities as indicated by the physical layer:

[0249] The MAC entity may randomly select time and frequency resources for one or more transmission opportunities from available resources according to the remaining PDB of SL data available on the logical channels allowed in the carrier, thereby ensuring the amount of selected frequency resources, the number of selected HARQ retransmissions, and the minimum time interval between two selected resources. The above operation may be performed when PSFCH is set for the corresponding resource pool, and the retransmission resources may be indicated by the time resource allocation of the previous SCI;

[0250] - The MAC entity may use the randomly selected resources to select a set of periodic resources separated by a resource reservation interval for PSCCH and PSSCH transmissions corresponding to the determined number of retransmission opportunities of the MAC PDU;

[0251] - The MAC entity may regard the first transmission opportunity set as an initial transmission opportunity, and may regard other transmission opportunity sets as retransmission opportunities;

[0252] - The MAC entity may consider the set of initial transmission opportunities and retransmission opportunities as the selected sidelink grant.

[0253] If one or more HARQ retransmissions are not selected, the MAC entity may consider the set as the selected sidelink grant.

[0254] The MAC entity may use the selected sidelink grant to determine a set of PSCCH durations and a set of PSSCH durations.

[0255] Alternatively, at the Tx UE, when the MAC entity selects a new resource pool or the MAC entity triggers TX resource (re)selection, the MAC entity may perform TX resource (re)selection according to the following Tx resource (re)selection manner to generate the selected side link grant for the selected resource pool:

[0256] -The MAC entity selects the number of HARQ retransmissions from the allowed number configured by RRC in 'sl-MaxTxTransNumPSSCH' included in 'sl-PSSCH-TxConfigList', and if configured by RRC, it may overlap between 'sl-MaxTxTransNumPSSCH' indicated in 'sl-CBR-PriorityTxConfigList' and the CBR measured by the lower layer, and if the CBR measurement result is not available, it may be the corresponding 'sl-defaultTxConfigIndex' configured by RRC.

[0257] - The MAC entity selects the amount of frequency resources within the range configured by RRC among 'sl-MinSubChannelNumPSSCH' and 'sl-MaxSubchannelNumPSSCH' included in 'sl-PSSCH-TxConfigList', and if set by RRC, it may overlap between 'MinSubChannelNumPSSCH' and 'MaxSubchannelNumPSSCH' indicated in 'sl-CBR-PriorityTxConfigList' and the CBR measured by the lower layer, and if the CBR measurement result is not available, it may be the corresponding 'sl-defaultTxConfigIndex' set by RRC;

[0258] - The MAC entity may arbitrarily select time and frequency resources from the resources indicated by the physical layer for a transmission opportunity, depending on the amount of selected frequency resources and the remaining PDBs of SL data available on the allowed logical channels on the carrier.

[0259] - The MAC entity may use the randomly selected resources to select a set of contiguous resources for transmission of PSCCH and PSSCH corresponding to multiple transmission opportunities of multiple MAC PDUs or one or more transmission opportunities of a single MAC PDU.

[0260] For transmission of PSCCH and PSSCH corresponding to one of multiple transmission opportunities of multiple MAC PDUs, the MAC entity may periodically select a series of consecutive resources based on a resource reservation interval.

[0261] Here, one of the allowed values ​​configured by RRC in 'sl-ResourceReservePeriodList' may be selected as the resource reservation interval. For each resource reservation interval, a set of continuous resources may be reserved.

[0262] One or more HARQ processes may be allocated to a single contiguous resource set in each resource reservation interval.The number of HARQ processes may be determined by the (maximum or fixed) number of HARQ processes for each contiguous resource set or each resource reservation interval.

[0263] The number of (maximum or fixed) HARQ processes per contiguous resource set or per resource reservation interval may be configured or preconfigured / defined by the base station.

[0264] The (maximum or fixed) number of HARQ processes can be (pre-)configured per resource pool, per SL BWP, per serving cell, per selected sidelink grant, or per logical channel priority of the SL logical channel used to trigger resource selection.

[0265] For each continuous resource set or resource reservation interval, for one or more HARQ process IDs indicated in one or more SCIs, different SCIs may indicate the same or different HARQ process IDs (as described below) to schedule different PSSCH transmissions in the same TB or different TBs.

[0266] For multiple TBs sent to the same destination UE, the UE may assign different HARQ process IDs to different HARQ processes for each consecutive resource set or resource reservation interval.

[0267] When multiple TBs are sent to different destination UEs, the UE may assign the same or different HARQ process IDs to different HARQ processes for each consecutive resource set or resource reservation interval.

[0268] One or more PSFCH resources may be reserved for each set of consecutive resources or resource reservation interval.

[0269] - Option 1: One or more PSFCH resources in a resource reservation interval may be used to send one or more HARQ-ACKs on a series of consecutive PSSCH resources always in the same resource reservation interval.

[0270] - Option 2: One or more PSFCH resources in a resource reservation interval may be used to send one or more HARQ-ACKs on a series of consecutive PSSCH resources in a previous resource reservation interval.

[0271] Other PSFCH resources in the resource reservation interval may be used to send one or more HARQ-ACKs to consecutive sets of PSSCH resources in the same resource reservation interval.

[0272] The MAC entity may regard the set as the selected sidelink grant. The MAC entity may use the selected sidelink grant to determine the PSCCH period set and the PSSCH period set.

[0273] Thereafter, in the steps described later, the UE may perform SL transmission on the selected sidelink grant using the PSCCH duration set and the PSSCH duration set.

[0274] In S1130, the Tx UE may perform sidelink (re)transmission of the MAC PDU on the selected resources and receive SL ACK / NACK on the PSFCH. Here, if SL NACK is received on the PSFCH, the Tx UE may (re)select Tx resources or reserve additional resources for retransmission of the MAC PDU.

[0275] RRC can establish a consistent (or continuous) LBT failure recovery process for the MAC entity of the (Tx)UE. If the UE's physical layer fails to access the channel before the expected UL or SL transmission to the base station, the physical layer can notify the MAC layer of the channel access failure (i.e., LBT failure).

[0276] The UE can detect / detect consistent (or continuous) LBT failure (S1140) per SL BWP or per UL BWP or per serving cell by counting LBT failure indications for all SL transmissions and / or all UL transmissions from the physical layer to the MAC entity based on at least one of the embodiments described below.

[0277] The Tx UE may send a PUCCH for SR to the base station (S1150). At step S1160, the Tx UE may send a message / information for SL connection release to the Rx terminal, and the Rx UE may send a SL ACK to the Tx UE on the PSFCH. For example, based on detecting a consistent SL LBT failure, the Tx UE may send a message for SL connection release to the Rx UE.

[0278] The Tx UE may transmit sidelink UE information (including information related to disconnection based on LBT failure) to the base station (S1170).

[0279] The above operations of the Tx UE are described in detail below.

[0280] Implementation 1: Integrated UL / SL LBT failure detection and recovery process

[0281] For each serving cell, the UE may count the LBT_COUNTER based on LBT failures for both UL transmissions via UL BWP and SL transmissions via SL BWP. An LBT Failure MAC CE may be generated and shared for LBT failures in both UL and SL. An SR (Scheduling Request) may be triggered and shared for LBT failures in both UL and SL. The SR configuration and resources may be common for both UL LBT failure reporting and SL LBT failure reporting. The parameters of 'lbt-FailureRecoveryConfig' (e.g., 'lbt-FailureInstanceMaxCount' and 'lbt-FailureDetectionTimer') may be shared between UL and SL and may be configured by RRC.

[0282] A consistent LBT failure recovery procedure for the MAC entity of the UE may be established by the RRC. A consistent LBT failure per UL BWP, per SL BWP, or per BWP overlapping with a UL BWP and a SL BWP may be detected by counting LBT failure indications for all UL transmissions and / or all SL transmissions from the lower layer (i.e., physical layer) to the MAC entity.

[0283] LBT_COUNTER (per serving cell) can be used for a consistent LBT failure detection process. LBT_COUNTER is a counter for LBT failure indications, which is initially set to 0. For each serving cell, LBT_COUNTER can be used to count LBT failure indications for UL transmissions only for the UL BWP of the serving cell, or LBT failure indications for SL transmissions only for the SLBWP of the serving cell, or LBS failure indications for UL transmissions and LBS failure indications for SL transmissions for both the uplink BWP and SL BWP of the serving cell.

[0284] For each activated serving cell configured with "lbt-FailureRecoveryConfig", the UE's MAC entity may perform the following actions:

[0285] 1> If an LBT failure indication has been received from the lower layer:

[0286] 2> Start or restart lbt-FailureDetectionTimer;

[0287] 2>Increment LBT_COUNTER by 1;

[0288] 2>If LBT_COUNTER>=lbt-FailureInstanceMaxCount:

[0289] 3> trigger consistent LBT failure for active UL BWP on the serving cell;

[0290] 3> trigger consistent LBT failure for active SL BWP on the serving cell;

[0291] 3> If the serving cell is SpCell:

[0292] 4> If consistent LBT failure is triggered on all UL BWPs configured as PRACH opportunities on the same carrier of the serving cell; or

[0293] 4> If a consistent LBT fails to be triggered on the corresponding SL BWP, and the PRACH opportunity is configured on the UL BWP of the same carrier as the SLBWP in the corresponding serving cell:

[0294] 5>Indicate consistent LBT failure to higher layers (ie, RRC layer).

[0295] 4> Otherwise:

[0296] 5> Stop the ongoing random access process on the serving cell;

[0297] 5> Switch the active UL BWP to the (target) UL BWP configured with PRACH opportunity and without triggering consistent LBT failure on the same carrier of the serving cell;

[0298] 5> Switch the active SL BWP to a (target) SL BWP configured with a PRACH opportunity and without triggering a consistent LBT failure on the same carrier of the serving cell, where the target SL BWP is associated with or overlaps the target UL BWP.

[0299] 5>Initiate random access process.

[0300] 1> If all triggered consistent LBT failures on the serving cell are cancelled; or

[0301] 1>If lbt-FailureDetectionTimer expires; or

[0302] 1> If lbt-FailureDetectionTimer or lbt-FailureInstanceMaxCount is reconfigured by higher layers:

[0303] 2>Set LBT_COUNTER to 0.

[0304] The UE's MAC entity shall:

[0305] 1> If a consistent LBT failure is triggered in SpCell and the consistent LBT failure is not canceled; and

[0306] 1> If there are UL-SCH resources available for new transmission in the SpCell, and due to logical channel priority, the UL-SCH resources can accommodate the LBT failure MAC CE and its subheader:

[0307] 2> Indicates the multiplexing and assembly process to generate LBT failure MAC CE.

[0308] 1> If a consistent LBT failure is triggered on at least one SCell and the consistent LBT failure is not canceled:

[0309] 2> If there are UL-SCH resources available for new transmissions in the serving cell where a consistent LBT failure has not been triggered, and due to logical channel priority, the UL-SCH resources can accommodate the LBT failure MAC CE and its subheader:

[0310] 3> Indicates the multiplexing and assembly process to generate LBT failure MAC CE.

[0311] 2> Otherwise:

[0312] 3>Trigger the scheduling request of LBT failed MAC CE.

[0313] 1> When a MAC PDU is sent and no LBT failure indication is received from the lower layers and the PDU contains an LBT failure MAC CE:

[0314] 2> Cancel all consistent LBT failures triggered on the SCell indicated by the sent LBT Failure MAC CE.

[0315] 1> If a consistent LBT failure is triggered in SpCell and the consistent LBT failure is not canceled; and

[0316] 1> If the random access process in SpCell is considered to have been successfully completed:

[0317] 2>Cancel all consistent LBT errors triggered in SpCell.

[0318] 1> If lbt-FailureRecoveryConfig is reconfigured by the upper layer of the serving cell:

[0319] 2>Cancel all consistent LBT failures triggered on this serving cell.

[0320] Implementation Method 1-1

[0321] Implementation 1-1 relates to the LBT failure MAC CE of Example 1.

[0322] An octet LBT Failure MAC CE may be identified by a MAC subheader with a specific LCID (e.g., an LCID mapped to index / codepoint 43 or / and 49). Fig.12 As shown in (a), the size of an octet LBT Failure MAC CE is fixed and may consist of a single octet including eight C fields.

[0323] The 4-octet LBT Failure MAC CE may be identified by a MAC subheader with a specific LCID (e.g., an LCID mapped to index / codepoint 42 or / and 48). Fig.12 As shown in (b), the size of the 4-octet LBT Failure MAC CE is fixed and may consist of 4 octets containing 32 C fields.

[0324] If the highest 'ServCellIndex' of the serving cell of the MAC entity detecting the LBT failure is less than 8, then the single octet format is used, otherwise the four octet format may be used.

[0325] If in Fig.12 If there is a serving cell with 'ServCellIndex'i configured for the MAC entity in (a) and (b), and a consistent LBT failure is triggered across UL and SL on the serving cell and the consistent LBT failure is not canceled, Ci may be set to 1. Otherwise, Ci may be set to 0.

[0326] Implementation 2: SL-specific LBT failure detection and recovery process

[0327] That is, embodiment 2 involves separate LBT failure detection and recovery procedures for SL LBT failure and UL LBT failure, and possible interaction between SL LBT failure and UL LBT failure.

[0328] The UE may separately count an existing LBT_COUNTER based on LBT failure of UL transmission in UL BWP and a new LBT_COUNTER_SL based on LBT failure of SL transmission in SL BWP for each serving cell.

[0329] The existing LBT failure MAC CE and the new LBT failure MAC CE can be generated separately for UL LBT failure and SL LBT failure, respectively. The SR for UL LBT failure and the SR for SL LBT failure can be triggered separately. The SR configuration and resources can be configured and allocated separately for UL LBT failure and SL LBT failure reporting.

[0330] Parameters of 'lbt-FailureRecoveryConfig' (eg, 'lbt-FailureInstanceMaxCount' and 'lbt-FailureDetectionTimer') may be configured separately for UL LBT failure and SL LBT failure via RRC, respectively.

[0331] Additionally or alternatively, as implementation 2, the existing LBT failure MAC CE can be reused for SL LBT failure reporting and UL LBT failure reporting. That is, the same MAC CE format can be used to indicate SL LBT failure or UL LBT failure based on different LC (Logical Channel) ID values.

[0332] The parameters in 'lbt-FailureRecoveryConfig' (e.g., 'lbt-FailureInstanceMaxCount' and 'lbt-FailureDetectionTimer') can be reused for SL LBT failure detection and UL LBT failure detection. That is, 'lbt-FailureInstanceMaxCount' or 'lbt-FailureDetectionTimer' can operate based on the configuration of the same corresponding parameter in 'lbt-FailureRecoveryConfig'.

[0333] Here, the SR configuration and resources may be common for both UL LBT failure reporting and SL LBT failure reporting.

[0334] Since the BWP can be composed of one or more RB sets (i.e., 20mHz LBT bandwidth) on which the UE performs LBT, the UE can perform LBT failure detection and recovery procedures for SL or UL specific RB sets instead of SL BWP or UL BWP. In this case, in each embodiment, the BWP can be replaced by an RB set.

[0335] The MAC entity of the UE may be configured by RRC with a consistent LBT failure recovery procedure. Consistent LBT failures per UL BWP, per SL BWP, or per BWP overlapping with UL BWP and SL BWP may be detected by counting LBT failure indications for all UL transmissions or all SL transmissions from the lower layers to the MAC entity.

[0336] RRC may be configured with the following parameters in 'lbt-FailureRecoveryConfig' for UL LBT failure detection.

[0337] -lbt-FailureInstanceMaxCount for consistent LBT failure detection in UL

[0338] -lbt-FailureDetectionTimer for consistent LBT failure detection in UL

[0339] RRC may be configured with the following parameters in 'lbt-FailureRecoveryConfigSL' to detect SL LBT failure.

[0340] - 'lbt-FailureInstanceMaxCountSL' for consistent LBT failure detection in SL

[0341] - 'lbt-FailureDetectionTimerSL' for consistent LBT failure detection in SL

[0342] The following UE parameters may be used for a consistent LBT failure detection procedure for UL LBT failure.

[0343] - LBT_COUNTER (per serving cell): counter of LBT failure indication, initially set to 0 for UL.

[0344] The following UE parameters can be used for a consistent LBT failure detection procedure for SL LBT failure.

[0345] - LBT_COUNTER_SL (per serving cell): counter of LBT failure indication, initially set to 0 for SL.

[0346] For each activated serving cell set to 'lbt-FailureRecoveryConfig', the UE's MAC entity may detect UL LBT failure:

[0347] 1> If an LBT failure indication for UL transmission is received from the lower layer:

[0348] 2> Start or restart lbt-FailureDetectionTimer;

[0349] 2>Increment LBT_COUNTER by 1;

[0350] 2>If LBT_COUNTER>=lbt-FailureInstanceMaxCount:

[0351] 3> trigger consistent LBT failure for active UL BWP on the serving cell;

[0352] 3> If the serving cell is SpCell:

[0353] 4> If consistent LBT failure is triggered in all UL BWPs configured as PRACH opportunities on the same carrier of the serving cell:

[0354] 5>Indicate consistent LBT failure to the upper layer (i.e., RRC layer).

[0355] 4> Otherwise:

[0356] 5> Stop the ongoing random access process on the serving cell;

[0357] 5> Switch the active UL BWP to the (target) UL BWP configured with PRACH opportunity and without triggering consistent LBT failure on the same carrier of the serving cell;

[0358] 5> Switch the active SL BWP to a (target) SL BWP that does not trigger a consistent LBT failure on the same carrier of the serving cell, where the target SL BWP is associated with or overlaps the target UL BWP;

[0359] 5>Initiate random access process.

[0360] 1> If the SL LBT fails, set LBT_COUNTER_SL to 0; or

[0361] 1> If the cancellation of all consistent LBT triggered in SL transmission fails on the serving cell; or

[0362] 1> If lbt-FailureDetectionTimerSL expires; or

[0363] 1> If lbt-FailureDetectionTimerSL or lbt-FailureInstanceMaxCountSL is reconfigured by the upper layer; or

[0364] 1> If all consistent LBTs triggered on the serving cell fail to be cancelled; or

[0365] 1>If lbt-FailureDetectionTimer expires; or

[0366] 1> If lbt-FailureDetectionTimer or lbt-FailureInstanceMaxCount is reconfigured by the upper layer:

[0367] 2>Set LBT_COUNTER to 0.

[0368] For each activated serving cell configured with lbt-FailureRecoveryConfigSL, the UE's MAC entity can detect SL LBT failure.

[0369] 1> If an LBT failure indication for SL transmission is received from the lower layer:

[0370] 2> Start or restart lbt-FailureDetectionTimerSL;

[0371] 2>Increment LBT_COUNTER_SL by 1;

[0372] 2>If LBT_COUNTER_SL>=lbt-FailureInstanceMaxCountSL:

[0373] 3> trigger consistent LBT failure for active SL BWP on the serving cell;

[0374] 3> If the serving cell is SpCell:

[0375] 4> If triggering consistent LBT on all SL BWPs fails, and PRACH triggering is configured on the UL BWP of the same carrier as the SL BWP in this serving cell:

[0376] 5>Indicate consistent LBT failure to the upper layer (i.e., RRC layer).

[0377] 4>Otherwise;

[0378] 5> Stop any random access process in progress in the serving cell;

[0379] 5> Switch the active SL BWP to the (target) SL BWP on the same carrier of the serving cell that is configured with a PRACH opportunity and does not trigger a consistent LBT failure in UL or SL.

[0380] 5> Switch the active UL BWP to a (target) UL BWP that does not trigger a consistent LBT failure on the same carrier of the serving cell, where the target UL BWP is associated with or overlaps the target SL BWP;

[0381] 5>Initiate random access process.

[0382] 1> If UL LBT fails, set LBT_COUNTER to 0; or

[0383] 1> If UL LBT fails, lbt-FailureDetectionTimer expires; or

[0384] 1> If UL LBT fails, the upper layer reconfigures lbt-FailureDetectionTimer or lbt-FailureInstanceMaxCount;

[0385] 1> If cancellation of all consistent LBT triggered in UL transmissions on the serving cell fails; or

[0386] 1> If the cancellation of all consistent LBT triggered in SL transmission fails on the serving cell; or

[0387] 1> If lbt-FailureDetectionTimerSL expires; or

[0388] 1> If lbt-FailureDetectionTimerSL or lbt-FailureInstanceMaxCountSL is reconfigured by the upper layer:

[0389] 2>Set LBT_COUNTER_SL to 0.

[0390] To report UL LBT failure, the MAC entity of the terminal can perform the following actions:

[0391] 1> If a consistent LBT failure for UL is triggered in SpCell and the consistent LBT failure is not cancelled; and

[0392] 1> If there are UL-SCH resources available for new transmission in the SpCell, and due to logical channel priority, these UL-SCH resources can accommodate the LBT failure MAC CE and its subheader:

[0393] 2> Indicates the multiplexing and assembly process to generate LBT failure MAC CE.

[0394] 1> If a consistent LBT failure for UL is triggered on at least one SCell and the consistent LBT failure is not cancelled:

[0395] 2> If there are UL-SCH resources available for new transmissions in the consistent LBT failure serving cell where UL or SL has not been triggered yet, and if those UL-SCH resources can accommodate the LBT failure MAC CE and its subheader due to logical channel prioritization:

[0396] 3> Indicates the multiplexing and assembly process for generating LBT failure MAC CE.

[0397] 2> Otherwise:

[0398] 3>Trigger the scheduling request of LBT failed MAC CE.

[0399] 1> When a MAC PDU is sent and no LBT failure indication is received from lower layers and the PDU includes an LBT failure MAC CE:

[0400] 2> Cancel all consistent LBT failures triggered on the SCell that indicated consistent LBT failure in the sent LBT failure MAC CE.

[0401] 1> If a consistent LBT failure for UL is triggered in SpCell and the consistent LBT failure is not cancelled; and

[0402] 1> If the random access process in SpCell is considered to be successfully completed:

[0403] 2> (Alternative 1-1) Cancel all consistent LBT failures triggered on UL except SL in SpCell.

[0404] 2> (Alternative 1-2) Cancel all consistent LBT failures triggered on both UL and SL in SpCell.

[0405] 1> If the upper layer reconfigures lbt-FailureRecoveryConfig for the serving cell:

[0406] 2> Cancel all consistent LBT failures triggered for UL on this serving cell.

[0407] 2> Cancel all consistent LBT failures triggered for SL on this serving cell.

[0408] To report SL LBT failure, the terminal's MAC entity can perform the following actions:

[0409] 1> If a consistent LBT failure for SL is triggered in SpCell and the consistent LBT failure has not been cancelled; and

[0410] 1> If there are UL-SCH resources available for new transmission in the SpCell and due to logical channel prioritization, the UL-SCH resources can accommodate the SL LBT Failure MAC CE and its subheader:

[0411] 2> Indicates the multiplexing and assembly process to generate SL LBT failure MAC CE.

[0412] 1> If a consistent LBT failure for the SL has been triggered on at least one SCell and the consistent LBT failure has not been canceled:

[0413] 2> If there are UL-SCH resources available for new transmissions in the serving cell that has not triggered a consistent LBT failure for UL or SL, and due to logical channel prioritization, the UL-SCH resources can accommodate the SL LBT failure MAC CE and its subheader;

[0414] 3> Indicates the multiplexing and assembly process to generate SL LBT failure MAC CE.

[0415] 2> Otherwise:

[0416] 3>Trigger SL LBT fails the scheduling request of MAC CE.

[0417] 1> If a MAC PDU is sent and no SL LBT Failure indication is received from lower layers and the PDU includes a SL LBT Failure MAC CE:

[0418] 2> Cancel all consistent LBT failures triggered on the SCell that indicated consistent LBT failure in the sent LBT failure MAC CE.

[0419] 1> If a consistent LBT failure for SL is triggered in SpCell and the consistent LBT failure is not canceled; and

[0420] 1> If the random access process in SpCell is considered to be successfully completed:

[0421] 2> (Alternative 2-1) Cancel all consistent LBT failures triggered in SpCell for SLs other than UL.

[0422] 2> (Alternative 2-2) Cancel all consistent LBT failures triggered in SpCell for both UL and SL.

[0423] 1> If the upper layer reconfigures lbt-FailureRecoveryConfigSL for the serving cell:

[0424] 2>Cancel all consistent LBT failures triggered for SL on this serving cell

[0425] 2>Cancel all consistent LBT failures triggered for UL on this serving cell

[0426] Implementation Method 2-1

[0427] Implementation 2-1 involves the LBT failure MAC CE and SL LBT failure MAC CE of implementation 1.

[0428] An octet LBT Failure MAC CE and SL LBT Failure MAC CE may be identified by a MAC subheader with a specific LCID. Fig.12 As shown in (a), the size of an octet LBT Failure MAC CE is fixed and may consist of a single octet including eight C fields.

[0429] The 4-octet LBT Failure MAC CE and SL LBT Failure MAC CE can be identified by a MAC subheader with a specific LCID. Fig.12 As shown in (b), the size of the 4-octet LBT Failure MAC CE is fixed and may consist of 4 octets including 32 C fields.

[0430] The UCID value of UL-SCH can be defined as shown in Table 10 below.

[0431] [Table 10]

[0432] Codepoint / Index LCID value 42 SL LBT failed (4 octets) 43 SL LBT failed (1 octet) 48 UL LBT Failure (4 octets) 49 UL LBT Failure (1 octet)

[0433] If the highest 'ServCellIndex' of the serving cell of the MAC entity that detected the LBT failure is less than 8, then the single octet format is used, otherwise the four octet format may be used. Fig.12 In (a) and (b), if there is a serving cell with "ServCellIndex" i configured for the MAC entity, and a consistent LBT failure is triggered across UL and SL in the serving cell and the consistent LBT failure is not canceled, Ci can be set to 1. Otherwise, Ci can be set to 0.

[0434] Whether to use Implementation 1 or Implementation 2 may depend on the SL mode or the serving cell that performs SL transmission. For example, Implementation 1 may be used for SL mode 1, and Implementation 2 may be used for SL mode 2. Implementation 1 may be used for a serving cell that allows both UL transmission and SL transmission, and Implementation 2 may be used for a serving cell. In this case, only SL transmission may be allowed, and UL transmission may not be allowed.

[0435] Implementation 3

[0436] Embodiment 3 relates to the operation of the Tx terminal performed after Embodiment 1 and / or Embodiment 2.

[0437] At the TX UE, if the selected sidelink grant can be used for retransmission of a positively acknowledged MAC PDU, the UE can clear the PSCCH period and PSSCH period corresponding to the retransmission of the MAC PDU in the selected sidelink grant. Here, the selected sidelink grant can correspond to the transmission of a single MAC PDU or the transmission of multiple MAC PDUs.

[0438] At the TX UE, the MAC entity may continuously perform the TX resource (re)selection confirmation process until the RRC releases the corresponding resource pool or the MAC entity decides to cancel the generation of the selected sidelink grant corresponding to the transmission of multiple MAC PDUs or the transmission of a single MAC PDU.

[0439] The MAC entity may perform a TX resource (re)selection check from the selected resource pool for the corresponding side link process if one or more of the following conditions are met. The conditions are as follows:

[0440] - If SL_RESOURCE_RESELECTION_COUNTER = 0 and SL_RESOURCE_RESELECTION_COUNTER is 1, the MAC entity may randomly select a value in the interval [0, 1] with equal probability higher than the probability configured by RRC in 'sl-ProbResourceKeep', which applies to the following options;

[0441] Option 1: If the transmission corresponds to the last transmission of a MAC PDU, the UE may decrement the SL_RESOURCE_RESELECTION_COUNTER by 1 (if available) even if the last transmission was not sent due to SL LBT failure.

[0442] Option 2: If transmission of the MAC PDU is not performed due to LBT failure when the terminal determines the last transmission of the MAC PDU of SL_RESOURCE_RESELECTION_COUNTER, the failed transmission may not be included in the transmission number of the MAC PDU.

[0443] 'sl-ProbResourceKeep' may be scaled up or down based on consistent LBT failures of the SL. A certain number of LBT failures in a selected sidelink grant or SL BWP may increase or decrease the value of 'sl-ProbResourceKeep'. For example, by multiplying sl-ProbResourceKeep' by N / 10, where N may be determined by the number of LBT failures or consistent LBT failures triggered.

[0444] - if the resource pool is established or reconfigured by RRC; or

[0445] - if the selected sidelink grant does not exist in the selected resource pool; or

[0446] - if the resources of the selected sidelink grant are not within the COT (Channel Occupancy Time) duration determined by the channel access procedure performed by the UE or shared by any UE / gNB / eNB; or

[0447] - if a consistent LBT failure is triggered for the selected sidelink grant; or

[0448] - if a consistent LBT failure is triggered for the active SLBWP of the corresponding serving cell associated with the sidelink grant selected in the above step; or

[0449] - if a consistent LBT failure is triggered in all SL BWPs of the serving cell associated with the selected sidelink grant; or

[0450] - if a consistent LBT failed for SL or UL triggered and not cancelled in the corresponding serving cell associated with the selected sidelink grant; or

[0451] - if during the past 1 second, the MAC entity has not actually performed a transmission or retransmission on the resources indicated in the selected sidelink grant, then the following alternative applies; or

[0452] Alternative 1: If a MAC PDU transmission is not performed due to LBT failure, the failed transmission may not be considered as a real (re)transmission.

[0453] Alternative 2: If a MAC PDU transmission is not performed due to LBT failure, the failed transmission may be considered as an actual (re)transmission.

[0454] If 'sl-ReselectAfter' is configured and the number of consecutive unused transmission opportunities for the resource indicated in the selected sidelink grant is equal to 'sl-ReselectAfter', the following alternative applies; or

[0455] Alternative 1: If MAC PDU transmission is not performed due to LBT failure, the transmission opportunity of the failed transmission may not be considered as an unused transmission opportunity of 'sl-ReselectAfter'.

[0456] Alternative 2: If MAC PDU transmission is not performed due to LBT failure, the transmission opportunity of the failed transmission may be considered as an unused transmission opportunity of 'sl-ReselectAfter'.

[0457] - if the selected sidelink grant cannot accommodate the RLC SDU using the maximum allowable MCS configured by RRC in sl-MaxMCS-PSSCH and the UE chooses not to segment the RLC SDU; or

[0458] If transmission using the selected sidelink grant cannot meet the latency requirements of the data on the logical channel according to the associated priority, and the MAC entity chooses not to perform the transmission corresponding to the single MAC PDU:

[0459] If the TX UE receives a SL NACK in response to the transmission of a MAC PDU at the last transmission opportunity for a sidelink grant selected by the UE within the COT duration determined by the UE or by any UE / gNB / eNB shared channel access procedure, and one or more retransmissions of the MAC PDU are still needed (e.g. due to a maximum number of transmissions of the MAC PDU); or

[0460] If one or more retransmissions of the MAC PDU are still needed after the last transmission opportunity for the selected sidelink grant within the COT duration determined by the UE or by any UE / gNB / eNB shared channel access procedure (e.g. due to a maximum number of transmissions of a MAC PDU with disabled HARQ feedback),

[0461] - If the next transmission opportunity for the selected sidelink grant can meet the delay requirement or the remaining PDB of the MAC PDU (and the next transmission opportunity is within the next COT):

[0462] The UE may perform retransmission of the MAC PDU using the next transmission opportunity of the selected sidelink grant in the next COT.

[0463] - Otherwise (i.e., the next transmission opportunity of the selected sidelink grant cannot meet the delay requirement or the remaining PDB of the MAC PDU):

[0464] Alternative 1-1: The UE may reserve additional resources within the COT and add the additional reserved resources to the selected sidelink grant (ie, the UE may not clear the selected sidelink grant).

[0465] Alternative 1-2: The UE may clear the selected sidelink grant associated with the sidelink process and trigger TX resource (re)selection.

[0466] If the UE cannot reserve (additional) resources within the COT according to Alternative 1 or Alternative 1-2, and the next transmission opportunity of the selected sidelink grant cannot meet the delay requirements or the remaining PDB of the MAC PDU, the UE may discard the MAC PDU, clear the buffer of the HARQ process storing the MAC PDU, or consider that the UE has reached the maximum number of transmissions of the MAC PDU.

[0467] When the MAC entity performs a TX resource (re)selection check on the resource pool selected for the corresponding side link process, the TX UE may release the selected side link grant associated with the side link process if possible and trigger TX resource (re)selection.

[0468] As an example of the present disclosure, the UE may perform at least one of the alternatives described below.

[0469] If triggering consistent LBT fails for the selected sidelink grant; or

[0470] If consistent LBT fails according to the above method for the activation SLBWP triggering of the corresponding serving cell associated with the selected sidelink grant; or

[0471] If a consistent LBT failure is triggered for all SL BWPs of the corresponding serving cell associated with the selected sidelink grant; or

[0472] If a consistent LBT trigger for SL or UL on the corresponding serving cell associated with the selected sidelink grant fails and is not cancelled:

[0473] -Alternative 6-1: The UE may reselect from the old SL resource pool to the new resource pool that triggers the reselection to generate a sidelink grant newly selected by the UE. Here, the currently selected sidelink grant may remain in the old SL resource pool.

[0474] -Alternative 6-2: The UE may reselect from the old RB set of the active SL BWP to the new RB set of the active SL BWP that triggers the reselection to generate a sidelink grant newly selected by the terminal. Here, the currently selected sidelink grant may remain in the old RB set.

[0475] -Alternative 6-3: The UE may reselect from the old SL BWP to the new SL BWP that triggers the reselection to generate a new sidelink grant selected by the terminal. Here, the currently selected sidelink grant may be reserved in the old SL BWP set.

[0476] -Alternative 6-4: The UE may reselect from the previous cell to the new cell that triggered the reselection to generate a newly selected sidelink grant. Here, the currently selected sidelink grant may remain on the carrier of the previous cell.

[0477] In the above alternatives, the 'lbt-FailureInstanceMaxCount' for consistent LBT failure detection may be set to different values ​​for different alternatives.

[0478] Additionally or alternatively, the 'lbt-FailureDetectionTimer' for consistent LBT failure detection may be set to different values ​​for different alternatives.

[0479] For example, the base station may set different lbt-FailureInstanceMaxCount values ​​for different alternatives. For example, the 'lbt-FailureInstanceMaxCount' value of alternative 6-1 may be lower than the 'lbt-FailureInstanceMaxCount' value of alternative 6-3.

[0480] Alternatively, the base station may set different 'lbt-FailureDetectionTimer' values ​​for different alternatives, such that the 'lbt-FailureDetectionTimer' value of alternative 6-4 may be lower than the 'lbt-FailureDetectionTimer' value of alternative 6-3.

[0481] The "lbt-FailureInstanceMaxCount" for consistent LBT failure detection and the "lbt-FailureDetectionTimer" for consistent LBT failure detection may be set to different values ​​for SL mode 1 (ie, SL resource allocation mode 1) and SL mode 2 (ie, SL resource allocation mode 2), respectively.

[0482] For SL Mode 1, the above parameters may be used for SR reporting. For SL Mode 2, the above parameters may be used for resource reselection. Additionally or alternatively, SR may be triggered due to consistent LBT errors in the steps described above for both SL Mode 1 and SL Mode 2.

[0483] Additionally or alternatively, the UE may release the PC5-RRC connection based on consistent LBT failure, as described below.

[0484] If triggering consistent LBT fails for the selected sidelink grant; or

[0485] If, in the above steps, a consistent LBT failure is triggered for the active SLBWP of the corresponding serving cell associated with the selected sidelink grant; or

[0486] If a consistent LBT failure is triggered for all SL BWPs of the corresponding serving cell associated with the selected sidelink grant; or

[0487] If a consistent LBT failure is triggered for SL or UL and is not cancelled, then on the corresponding serving cell associated with the selected sidelink grant:

[0488] - If the TX UE establishes a PC5-RRC connection with the RX UE, then

[0489] Option 6-1: The MAC entity of the TX UE may consider that the sidelink RLF has been detected and may notify the RRC of the TX UE of 'Sidelink RLF Detection'.

[0490] Option 6-2: The MAC entity of the TX UE may consider that a consistent SL LBT failure has been detected and may notify the RRC of the TX UE of the consistent SL LBT failure.

[0491] The TX UE may send a PC5-RRC release message to the RX UE and release the PC5-RRC connection with the RX UE. The RX UE receiving the PC5-RRC release message may release the PC5-RRC connection with the TX UE.

[0492] The TX UE may send a PUCCH to the base station to indicate a persistent LBT failure or PC5-RRC disconnection by triggering an SR.

[0493] After PC5-RRC disconnection, the TX UE may send a 'SidelinkUEInformation' message to the base station to indicate PC5-RRC disconnection with the RX UE. The 'SidelinkUEInformation' message may indicate to the base station that the PC5-RRC with the RX terminal has been disconnected or should be disconnected due to consistent LBT failure detection.

[0494] The UE may perform re-evaluation or preemption according to the method described below.

[0495] The resources of the sidelink grant selected for transmission from the multiplexing and assembly entity for the MAC PDU may be re-evaluated by the physical layer in a T3 timeslot prior to the timeslot in which the SCI indicating the resources was first signaled. The resources of the sidelink grant selected for transmission from the multiplexing and assembly entity for the MAC PDU indicated by the previous SCI may be checked for preemption by the physical layer in a T3 timeslot prior to the timeslot in which the resources were located.

[0496] Re-evaluation or preemption before 'm-T3', or after 'm-T3' but before 'm' may vary depending on the terminal implementation. For re-evaluation, m refers to the timeslot in which the SCI indicating the resource was initially signaled. For preemption, m may refer to the timeslot in which the resource is located.

[0497] When the sidelink resource allocation mode 2 is set to use the resource pool of the carrier of the UE's MAC entity for transmission or to transmit based on detection or random selection, the UE's MAC entity may perform the following operations for each sidelink process:

[0498] 1> If the physical layer indicates to re-evaluate the resources of the selected sidelink grant that were not identified by the previous SCI;

[0499] 2> Remove resources from the selected side link grant associated with the side link process;

[0500] 2> If PSFCH is configured for the corresponding resource pool and resources can be used for retransmission as indicated by the time resource allocation of SCI, then based on the amount of selected frequency resources, the number of selected HARQ retransmissions and the remaining PDB of SL data available on the logical channel, randomly select time and frequency resources from the resources indicated by the physical layer for the removed or discarded resources by ensuring the minimum time interval between the two selected resources of the selected sidelink grant;

[0501] 2>Replace the selected resources (resources selected to be removed or deleted) with the selected side link authorized resources.

[0502] 1> if the resources of the selected sidelink grant are not within the COT (Channel Occupancy Time) duration determined by the channel access procedure performed by the UE or shared by any UE / gNB / eNB; or

[0503] 1> If the resources of the selected sidelink grant cannot be used for SL transmission due to LBT failure indication of L1;

[0504] 2> Remove resources from the selected side link grant associated with the side link process;

[0505] 2> If PSFCH is configured for the corresponding resource pool and resources can be used for retransmission as indicated by the time resource allocation of SCI, then based on the amount of selected frequency resources, the number of selected HARQ retransmissions and the remaining PDB of SL data available on the logical channel, randomly select time and frequency resources from the resources indicated by the physical layer for the removed or discarded resources by ensuring the minimum time interval between the two selected resources of the selected sidelink grant;

[0506] 2>Replace the selected resources (resources that have been removed or deleted) with the selected side link authorized resources.

[0507] 1> If the resources of the selected sidelink grant indicated by the previous SCI are marked as preempted by the physical layer;

[0508] 2> If more than one SL DRX is configured:

[0509] 3> Remove resources from the selected side link grant associated with the side link process;

[0510] 3> If PSFCH is configured for the corresponding resource pool and resources can be used for retransmission as indicated by the time resource allocation of the SCI, then randomly select time and frequency resources from resources later than the removed or missing resources indicated by the previous SCI by ensuring the minimum time interval between the two selected resources of the selected sidelink grant, the amount of frequency resources, the number of selected HARQ retransmissions, and the remaining PDB of SL data available on the logical channel;

[0511] 3>Replace the selected resources (resources selected to be removed or deleted) with the selected side link authorized resources.

[0512] 2> Otherwise:

[0513] 3> Remove resources from the selected side link grant associated with the side link process;

[0514] 3> If PSFCH is configured for the corresponding resource pool and resources can be used for retransmission as indicated by the time resource allocation of SCI, then randomly select time and frequency resources for the removed or discarded resources from the resources indicated by the physical layer by ensuring the minimum time interval between the two selected resources of the selected sidelink grant, the amount of frequency resources, the number of selected HARQ retransmissions, and the remaining PDB of SL data available on the logical channel;

[0515] 3>Replace the selected resources (resources selected to be removed or deleted) with the selected side link authorized resources.

[0516] Here, if it is not possible to select the retransmission resources by ensuring the resources indicated by the time resource allocation of the previous SCI, a method for selecting time and frequency resources for one or more transmission opportunities from available resources based on the UE can be implemented by ensuring a minimum time interval between two selected resources when the PSFCH is configured for the resource pool.

[0517] UE implementations may be permitted to reselect pre-selected but unreserved resources during a re-evaluation or pre-emption triggered by the physical layer, rather than resources indicated by the physical layer for pre-emption or re-evaluation.

[0518] Whether to set a resource reservation interval on the reselected resources to replace the preempted resources may vary by UE implementation. Whether to trigger resource reselection due to de-prioritization may vary by UE implementation.

[0519] If the selected sidelink grant corresponds to the transmission of multiple MAC PDUs, the UE implementation may decide whether to apply the re-evaluation check to resources of non-initial reservation periods that were not signaled in the previous or current period.

[0520] At the TX UE, for each SCI and SL grant corresponding to a new transmission, the MAC entity may perform a logical channel priority procedure to select a destination associated with one of the unicast, multicast, and broadcast logical channels, and a MAC CE with one of the logical channels and a MAC CE with the highest priority (for the SL grant associated with the SCI) that satisfies all of the following conditions:

[0521] Here, these conditions may include: i) SL data can be sent; ii) there is a logical channel with SBj (sidelink data bucket size / value in logical channel j)>0, and SBj>0; iii) if the SL grant is a configured grant type 1 (if set), then set its 'sl-configuredGrantType1Allowed' to 'true'; iv) 'sl-AllowedCG-List' contains the configured grant index associated with the SL grant (if set); and v) if PSFCH is not configured for SL grant associated with SCI, set 'sl-HARQ-FeedbackEnabled' to disabled.

[0522] If multiple destinations have logical channels with the same highest priority that satisfy all of the above conditions, or if multiple destinations have logical channels and / or MAC CEs with the same priority as the MAC CE that satisfy all of the above conditions, then selecting a specific destination among the above destinations may be based on terminal implementation.

[0523] If the PSFCH is configured at this step for a sidelink grant associated with an SCI, and any consecutive SL grants used to generate transmission of a MAC PDU for this procedure may satisfy the minimum time interval:

[0524] - If 'sl-HARQ-FeedbackEnabled' is set to enabled for the highest priority logical channel that meets the above conditions, the MAC entity sets 'sl-HARQ-FeedbackEnabled' to enabled; or

[0525] - If 'sl-HARQ-FeedbackEnabled' is set to disabled for a logical channel with the highest priority satisfying the above conditions, the MAC entity may set 'sl-HARQ-FeedbackEnabled' to disabled.

[0526] Meanwhile, if PSFCH is not configured for sidelink grant associated with SCI, or if consecutive SL grants for transmission of MAC PDU generated for this procedure cannot satisfy the minimum time interval, the MAC entity may set 'sl-HARQ-FeedbackEnabled' to disabled.

[0527] When the MAC entity sets 'sl-HARQ-FeedbackEnabled' to enabled, the MAC entity may choose to set 'sl-HARQ-FeedbackEnabled' to enabled logical channels. When the MAC entity sets 'sl-HARQ-FeedbackEnabled' to disabled, the MAC entity may choose to set 'sl-HARQ-FeedbackEnabled' to disabled logical channels.

[0528] And, for each SCI and SL grant corresponding to a new transmission, the MAC entity may generate a MAC PDU including SL data only on the logical channel selected for the HARQ entity. Here, logical channels for which 'sl-HARQ-FeedbackEnabled' is set to enabled and logical channels for which 'sl-HARQ-FeedbackEnabled' is set to disabled may not be multiplexed in the same MAC PDU.

[0529] At the sending UE, if the MAC entity determines that the sidelink grant is used for the initial transmission of each sidelink grant for the selected sidelink grant, or the sidelink grant is a configured sidelink grant and no MAC PDU is obtained in the 'sl-PeriodCG' of the configured sidelink grant, the MAC entity can obtain the MAC PDU generated in the above steps.

[0530] When acquiring a MAC PDU to be sent, the MAC entity may determine the sidelink transmission information of the TB for the source and destination pair of the MAC PDU as described below.

[0531] When a MAC PDU to be sent is obtained, the MAC entity may determine the sidelink transmission information of the TB for the source and destination pair of the MAC PDU as follows:

[0532] - The MAC entity may configure the Source Layer-1 ID as the 8LSBs of the Source Layer-2 ID of the MAC PDU.

[0533] - The MAC entity may configure the destination layer-1 ID as the 16LSBs of the destination layer-2 ID of the MAC PDU.

[0534] -The MAC entity may consider that the NDI is to be switched by comparing the sidelink identification information with the previously transmitted value of the sidelink process ID corresponding to the MAC PDU, and may set the NDI to the switched value.

[0535] - The MAC entity may configure the broadcast type indicator as one of broadcast, multicast and unicast as indicated by the upper layer.

[0536] - If HARQ feedback is enabled for a MAC PDU according to the logical channel priority procedure, the MAC entity may set the HARQ feedback enable / disable indicator to enabled.

[0537] - If HARQ feedback is disabled for a MAC PDU according to the logical channel priority procedure, the MAC entity may set the HARQ feedback enable / disable indicator to disabled.

[0538] - The MAC entity may configure the priority to be the highest priority value of the logical channel (if any) and MAC CE (if included) included in the MAC PDU.

[0539] - If both the group size and the member ID are provided by upper layers, and the group size is not greater than the number of candidate PSFCH resources associated with the corresponding sidelink grant, the MAC entity may choose to either positive-negative ACK or only negative grant. Otherwise, the MAC entity may choose to only negative grant.

[0540] - If Negative ACK Only is selected, the UE's location information is available, 'sl-TransRange' is set for the logical channel in the MAC PDU, and 'sl-ZoneConfig' is set, the MAC entity may configure the communication range requirement to the longest communication range value of the logical channel in the MAC PDU.

[0541] The MAC entity may determine a 'sl-ZoneLength' value corresponding to the communication range requirement, set 'Zone_id' to a 'Zone_id' value calculated using the determined 'sl-ZoneLength' value, and perform a new transmission of the MAC PDU on the PSSCH using a sidelink grant.

[0542] The TX UE may monitor the PSFCH occasions and determine a positive ACK or a negative ACK for the MAC PDU based on the PSFCH transmissions performed by the RX UE.

[0543] If the TX UE determines a negative ACK and the sidelink grant of the selected sidelink grant is retransmission-capable, the MAC entity may perform retransmission of the MAC PDU on the PSSCH using the sidelink grant.

[0544] When describing the present disclosure, sidelink transmissions, grants and resources may be replaced by uplink transmissions, grants and resources. (When the UE autonomously determines a new transmission or retransmission of up to N TB transmissions in a resource pool), the UE may change the resource pool or SL BWP or RB set or the serving cell performing SL transmission based on consistent SL LBT failures.

[0545] General devices to which the present disclosure can be applied

[0546] Fig.13 A block diagram of a wireless communication device according to an embodiment of the present disclosure is illustrated.

[0547] Reference Fig.13 , the first wireless device 100 and the second wireless device 200 can send and receive wireless signals through various radio access technologies (e.g., LTE, NR).

[0548] The first wireless device 100 may include one or more processors 102 and one or more memories 104, and may further include one or more transceivers 106 and / or one or more antennas 108. The processor 102 may control the memory 104 and / or the transceiver 106, and may be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operational flow charts disclosed in the present disclosure.

[0549] For example, the processor 102 may process the information in the memory 104 to generate first information / signal, and then transmit a wireless signal including the first information / signal through the transceiver 106. In addition, the processor 102 may receive a wireless signal including second information / signal through the transceiver 106, and then store information obtained from the signal processing of the second information / signal in the memory 104.

[0550] The memory 104 may be connected to the processor 102 and may store various information related to the operation of the processor 102. For example, the memory 104 may store software code including commands for executing all or part of the processing controlled by the processor 102 or for executing the descriptions, functions, processes, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. Here, the processor 102 and the memory 104 may be part of a communication modem / circuit / chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver 106 may be connected to the processor 102 and may send and / or receive wireless signals through one or more antennas 108. The transceiver 106 may include a transmitter and / or a receiver. The transceiver 106 may be used in conjunction with an RF (radio frequency) unit. In the present disclosure, a wireless device may refer to a communication modem / circuit / chip.

[0551] The second wireless device 200 may include one or more processors 202 and one or more memories 204, and may further include one or more transceivers 206 and / or one or more antennas 208. The processor 202 may control the memory 204 and / or the transceiver 206, and may be configured to implement the description, function, process, suggestion, method and / or operation flowchart disclosed in the present disclosure. For example, the processor 202 may generate third information / signal by processing the information in the memory 204, and then transmit the wireless signal including the third information / signal through the transceiver 206. In addition, the processor 202 may receive the wireless signal including the fourth information / signal through the transceiver 206, and then store the information obtained by the signal processing of the fourth information / signal in the memory 204. The memory 204 may be connected to the processor 202 and may store various information related to the operation of the processor 202. For example, the memory 204 may store software codes including commands for executing all or part of the processing controlled by the processor 202 or for executing the description, function, process, suggestion, method and / or operation flowchart disclosed in the present disclosure. Here, the processor 202 and the memory 204 may be part of a communication modem / circuit / chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver 206 may be connected to the processor 202 and may send and / or receive wireless signals through one or more antennas 208. The transceiver 206 may include a transmitter and / or a receiver. The transceiver 206 may be used in conjunction with an RF unit. In the present disclosure, a wireless device may refer to a communication modem / circuit / chip.

[0552] In the following, the hardware elements of the wireless device 100, 200 will be described in more detail. Without limitation thereto, one or more protocol layers may be implemented by one or more processors 102, 202. For example, one or more processors 102, 202 may implement one or more layers (e.g., functional layers such as PHY, MAC, RLC, PDCP, RRC, SDAP). One or more processors 102, 202 may generate one or more PDUs (protocol data units) and / or one or more SDUs (service data units) according to the descriptions, functions, processes, suggestions, methods, and / or operational flowcharts included in the present disclosure. One or more processors 102, 202 may generate messages, control information, data, or information according to the descriptions, functions, processes, suggestions, methods, and / or operational flowcharts disclosed in the present disclosure. One or more processors 102, 202 may generate a signal (e.g., a baseband signal) including a PDU, SDU, message, control information, data, or information according to the functions, procedures, suggestions, and / or methods disclosed in the present disclosure to provide it to one or more transceivers 106, 206. One or more processors 102, 202 may receive a signal (e.g., a baseband signal) from one or more transceivers 106, 206 according to the descriptions, functions, procedures, suggestions, methods, and / or operational flow charts disclosed in the present disclosure, and obtain the PDU, SDU, message, control information, data, or information.

[0553] One or more processors 102, 202 may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. One or more processors 102, 202 may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more ASICs (Application Specific Integrated Circuits), one or more DSPs (Digital Signal Processors), one or more DSPDs (Digital Signal Processing Devices), one or more PLDs (Programmable Logic Devices), or one or more FPGAs (Field Programmable Gate Arrays) may be included in one or more processors 102, 202. The descriptions, functions, processes, suggestions, methods, and / or operational flow charts disclosed in the present disclosure may be implemented using firmware or software, and the firmware or software may be implemented to include modules, processes, functions, etc. Firmware or software configured to execute the descriptions, functions, processes, suggestions, methods, and / or operational flow charts in the present disclosure may be included in one or more processors 102, 202, or may be stored in one or more memories 104, 204 and driven by one or more processors 102, 202. The descriptions, functions, processes, suggestions, methods and / or operational flow charts disclosed in the present disclosure may be implemented by using firmware or software in the form of codes, commands and / or command sets.

[0554] One or more memories 104, 204 may be connected to one or more processors 102, 202 and may store data, signals, messages, information, programs, codes, instructions, and / or commands in various forms. One or more memories 104, 204 may be configured with ROM, RAM, EPROM, flash memory, hard drive, registers, cache memory, computer-readable storage media, and / or combinations thereof. One or more memories 104, 204 may be located inside and / or outside one or more processors 102, 202. In addition, one or more memories 104, 204 may be connected to one or more processors 102, 202 via various technologies such as wired or wireless connections.

[0555] One or more transceivers 106, 206 may send user data, control information, wireless signals / channels, etc. mentioned in the method and / or operation flow chart of the present disclosure to one or more other devices. One or more transceivers 106, 206 may receive user data, control information, wireless signals / channels, etc. mentioned in the description, function, process, suggestion, method and / or operation flow chart disclosed in the present disclosure from one or more other devices. For example, one or more transceivers 106, 206 may be connected to one or more processors 102, 202 and may send and receive wireless signals. For example, one or more processors 102, 202 may control one or more transceivers 106, 206 to send user data, control information or wireless signals to one or more other devices. In addition, one or more processors 102, 202 may control one or more transceivers 106, 206 to receive user data, control information or wireless signals from one or more other devices. In addition, one or more transceivers 106, 206 may be connected to one or more antennas 108, 208, and one or more transceivers 106, 206 may be configured to transmit and receive user data, control information, wireless signals / channels, etc. mentioned in the description, functions, processes, suggestions, methods, and / or operation flow charts, etc. disclosed in the present disclosure through one or more antennas 108, 208. In the present disclosure, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers 106, 206 may convert received wireless signals / channels, etc. from RF band signals into baseband signals to process received user data, control information, wireless signals / channels, etc. by using one or more processors 102, 202. One or more transceivers 106, 206 may convert user data, control information, wireless signals / channels, etc. processed by using one or more processors 102, 202 from baseband signals into RF band signals. Thus, one or more of the transceivers 106 , 206 may include (analog) oscillators and / or filters.

[0556] The above-mentioned embodiments are to combine the elements and features of the present disclosure in a predetermined form. Unless otherwise explicitly mentioned, each element or feature should be regarded as optional. Each element or feature can be implemented in a form that is not combined with other elements or features. In addition, the embodiments of the present disclosure may include a combination of some elements and / or features. The order of the operations described in the embodiments of the present disclosure may be changed. Some elements or features of an embodiment may be included in other embodiments, or may be replaced by corresponding elements or features of other embodiments. Obviously, the embodiments may include claims that do not have a clear reference relationship in the combined claims, or may be included as new claims by modification after application.

[0557] It is clear to those skilled in the relevant art that the present disclosure can be implemented in other specific forms within the scope of the essential features of the present disclosure. Therefore, the above detailed description should not be interpreted restrictively in every aspect, but should be considered as illustrative. The scope of the present disclosure should be determined by the reasonable interpretation of the attached claims, and all changes within the equivalent scope of the present disclosure are included in the scope of the present disclosure.

[0558] The scope of the present disclosure includes software or machine executable commands (e.g., operating systems, applications, firmware, programs, etc.) that perform operations in a device or computer according to the methods of various embodiments, and non-transitory computer-readable media that enable software or commands, etc. to be stored and executable in a device or computer. Commands that can be used to program a processing system that performs the features described in the present disclosure can be stored in a storage medium or a computer-readable storage medium, and the features described in the present disclosure can be implemented by using a computer program product that includes such a storage medium. The storage medium may include a high-speed random access memory, such as, for example, DRAM, SRAM, DDR RAM, or other random access solid-state storage devices, but is not limited thereto, and it may include non-volatile memory, such as, for example, one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid-state storage devices. The memory optionally includes one or more storage devices located away from the processor. The memory, or alternatively, the non-volatile memory device in the memory includes a non-transitory computer-readable storage medium. The features described in this disclosure may be stored in any machine-readable medium to control the hardware of a processing system, and may be integrated into software and / or firmware that allows the processing system to interact with other mechanisms using the results from the embodiments of this disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0559] Here, the wireless communication technology implemented in the wireless devices 100 and 200 of the present disclosure may include narrowband Internet of Things for low-power communication, as well as LTE, NR and 6G. Here, for example, NB-IoT technology may be an example of LPWAN (Low Power Wide Area Network) technology, which may be implemented in standards such as LTE Cat NB1 and / or LTE Cat NB2 and is not limited to the above names. Additionally or alternatively, the wireless communication technology implemented in the wireless devices 100 and 200 of the present disclosure may perform communication based on LTE-M technology. Here, for example, LTE-M technology may be an example of LPWAN technology and may be referred to as various names such as eMTC (enhanced machine type communication). For example, LTE-M technology may be implemented in at least any one of various standards, including 1) LTE CAT 0; 2) LTE Cat M1; 3) LTE Cat M2; 4) LTE non-BL (non-bandwidth limited); 5) LTE-MTC; 6) LTE machine type communication; and / or 7) LTE M, etc., and is not limited to the above names. Additionally or alternatively, the wireless communication technology implemented in the wireless devices 100, 200 of the present disclosure may include at least any one of ZigBee, Bluetooth, and a low power wide area network (LPWAN) considering low power communication, and is not limited to the above names. For example, ZigBee technology can generate a PAN (Personal Area Network) related to small / low power digital communication based on various standards (e.g., IEEE 802.15.4, etc.), and can be called various names.

[0560] Industrial Applicability

[0561] The method proposed in the present disclosure is mainly described based on examples applied to 3GPP LTE / LTE-A and 5G systems, but can also be applied to various wireless communication systems other than 3GPP LTE / LTE-A and 5G systems.

Claims

1. A method performed by a first user equipment UE in a wireless communication system, the method comprising: receiving, from a base station, first configuration information related to a sidelink SL-specific listen-before-talk (LBT) failure detection timer and second configuration information related to an SL-specific LBT failure counter; triggering a consistent SL specific LBT failure based on a SL specific failure detection timer and the SL specific LBT failure counter; releasing the SL connection of the second UE associated with the triggered consistent SL specific LBT failure; and Information indicating at least one of a triggered consistent SL-specific LBT failure or the release of the SL connection is sent to the base station.

2. The method according to claim 1, wherein: High-layer signaling including information for releasing the SL connection of the second UE associated with the SL-specific LBT failure is sent by the first UE to the second UE, and the SL connection is released.

3. The method according to claim 1, wherein: The second configuration information includes information related to a maximum number of SL-specific LBT failure instances for consistent SL-specific LBT detection, and indicates receiving a counter counting SL-specific failures from the base station.

4. The method according to claim 1, wherein: The SL-specific failure detection timer and the SL-specific LBT failure counter are configured for the first UE per service cell.

5. The method according to claim 1, wherein: Information indicating at least one of a triggered consistent SL-specific LBT failure or a release of the SL connection is sent to the base station via a physical uplink control channel PUCCH by triggering a scheduling request SR.

6. The method according to claim 1, wherein: Information indicating the release of the SL connection is sent to the base station via high-layer signaling related to side link UE information.

7. The method according to claim 1, wherein: The first configuration information and the second configuration information are received from the base station via high-layer signaling related to SL-specific LBT failure recovery.

8. The method of claim 1, wherein: The SL-specific LBT failure is triggered based on the SL-specific failure detection timer and the SL-specific LBT failure counter for at least one of at least one RB set or at least one resource pool.

9. The method according to claim 1, wherein: Based on reconfiguring at least one of the SL-specific failure detection timer and the SL-specific LBT failure counter for the UE, setting the value of the SL-specific failure detection timer to 0.

10. The method of claim 1, wherein: Based on the expiration of the SL specific failure detection timer, the value of the SL specific failure detection timer is set to 0.

11. A first user equipment UE in a wireless communication system, the first UE comprising: at least one transceiver; as well as at least one processor connected to the at least one transceiver, Wherein, the at least one processor is configured to: receiving, by the at least one transceiver, first configuration information related to a sidelink SL-specific listen-before-talk (LBT) failure detection timer and second configuration information related to a SL-specific LBT failure counter from a base station; triggering a consistent SL specific LBT failure based on a SL specific failure detection timer and the SL specific LBT failure counter; releasing the SL connection of the second UE associated with the triggered consistent SL specific LBT failure; and Information indicating at least one of a triggered consistent SL-specific LBT failure or the release of the SL connection is sent to the base station through the at least one transceiver.

12. A method performed by a base station in a wireless communication system, the method comprising: Sending first configuration information related to a sidelink SL-specific listen-before-talk LBT failure detection timer and second configuration information related to a SL-specific LBT failure counter to a user equipment UE; and receiving, from a first UE, information indicating at least one of a consistent SL-specific LBT failure triggered by the first UE or a release of a SL connection between the first UE and a second UE, wherein the consistent SL specific LBT failure is triggered based on a SL specific failure detection timer and the SL specific LBT failure counter, and Release the SL connection between the first UE and the second UE associated with the triggered consistent SL specific LBT failure.

13. A base station in wireless communication, the base station comprising: at least one transceiver; as well as at least one processor connected to the at least one transceiver, Wherein, the at least one processor is configured to: Sending, through the at least one transceiver, first configuration information related to a sidelink SL-specific listen-before-talk LBT failure detection timer and second configuration information related to a SL-specific LBT failure counter to a user equipment UE; and receiving, by the at least one transceiver, from a first UE information indicating at least one of a consistent SL-specific LBT failure triggered by the first UE or a release of a SL connection between the first UE and a second UE, wherein the consistent SL specific LBT failure is triggered based on a SL specific failure detection timer and the SL specific LBT failure counter, and Release the SL connection between the first UE and the second UE associated with the triggered consistent SL specific LBT failure.

14. A processing device, the processing device being configured to control a first user equipment UE in a wireless communication system, the processing device comprising: at least one processor; as well as at least one computer memory operatively coupled to the at least one processor and storing instructions for performing operations when executed by the at least one processor, The operations include: receiving, from a base station, first configuration information related to a sidelink SL-specific listen-before-talk (LBT) failure detection timer and second configuration information related to an SL-specific LBT failure counter; triggering a consistent SL specific LBT failure based on a SL specific failure detection timer and the SL specific LBT failure counter; releasing the SL connection of the second UE associated with the triggered consistent SL specific LBT failure; and Information indicating at least one of a triggered consistent SL-specific LBT failure or the release of the SL connection is sent to the base station.

15. At least one non-transitory computer-readable medium storing at least one instruction, Based on the at least one instruction being executed by at least one processor, the device in the wireless communication system controls: receiving, from a base station, first configuration information related to a sidelink SL-specific listen-before-talk (LBT) failure detection timer and second configuration information related to an SL-specific LBT failure counter; triggering a consistent SL specific LBT failure based on a SL specific failure detection timer and the SL specific LBT failure counter; releasing the SL connection of the second UE associated with the triggered consistent SL specific LBT failure; and Information indicating at least one of a triggered consistent SL-specific LBT failure or the release of the SL connection is sent to the base station.

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