Wireless terminal, ran node, and methods therefor

Abstract

This wireless terminal takes into account a failure in channel access for a first type of sidelink transmission, in order to detect a consistent sidelink Listen-Before-Talk (LBT) failure, but ignores a failure in channel access for a second type of sidelink transmission in detecting a consistent sidelink LBT failure. This can contribute, for example, to the provision of an improved mechanism for detecting consistent sidelink LBT failures that is suitable for sidelink transmissions.

Description

WIRELESS TERMINAL, RAN NODE, AND METHOD THEREOF The present disclosure relates to wireless communication systems, and more particularly to device-to-device (D2D) communication between wireless terminals. A form in which a wireless terminal communicates directly with another wireless terminal without going through an infrastructure network such as a base station is generally called device-to-device (D2D) communication. D2D communication can be integrated with or supported by a cellular network. Proximity-based services (ProSe) defined in 3rd Generation Partnership Project (3GPP) Release 12 and subsequent releases provide a system architecture for D2D communication supported by a cellular network. Cellular Vehicle-to-Everything (V2X) services defined in 3GPP Release 14 and subsequent releases refer to ProSe and utilize D2D communication between wireless terminals. D2D communication supported by a cellular network can also be used for other applications and services (e.g., public safety applications) other than V2X services. The interface between 3GPP wireless terminals (i.e., User Equipments (UEs)) used for the control plane and user plane for D2D communication is called the PC5 interface (or reference point). D2D communication over the PC5 interface is called sidelink communication. The PC5 interface can be based on the Evolved Universal Terrestrial Radio Access (E-UTRA) sidelink capabilities and can also be based on the 5G New Radio (NR) sidelink capabilities. D2D communication (or sidelink communication) over the E-UTRA-PC5 (or Long Term Evolution (LTE) based PC5) interface is connectionless, i.e., in broadcast mode at the Access Stratum (AS) layer. In contrast, sidelink communication over the NR PC5 interface supports unicast, groupcast, and broadcast modes at the AS layer. Sidelink communication over the E-UTRA-PC5 interface is referred to as, for example, LTE sidelink communication. Sidelink communication over the NR PC5 interface is referred to as, for example, NR sidelink communication. 3GPP specifications specify architecture enhancements to facilitate vehicular communications for cellular V2X services. LTE sidelink communication and NR sidelink communication play an important role for the realization of cellular V2X communications. AS functionality using E-UTRA technology including LTE sidelink communication to enable V2X communications between UEs, or V2X communications over the E-UTRA-PC5 interface, is referred to as V2X sidelink communication or LTE V2X sidelink communication. AS functionality using NR technology including NR sidelink communication to enable V2X communications between UEs, or V2X communications over the NR PC5 interface, is referred to as NR V2X sidelink communication or simply NR sidelink communication. For Release 18, 3GPP is considering enhancements to the NR sidelink (SL). These enhancements include sidelink in unlicensed or shared spectrum (SL Unlicensed (SL-U)) (see, for example, Non-Patent Documents 4-7). The channel access mechanism of NR Unlicensed (NR-U) is reused for sidelink in unlicensed or shared spectrum. In the following, we first provide an overview of NR-U. 3GPP Release 16 and later releases support 5G NR (NR-U) in shared spectrum (see, for example, 3GPP RFC3111, Chapter 5.6 in 3GPP RFC3111, and Chapter 5.21 in 3GPP RFC3111). Shared spectrum is also called unlicensed spectrum. gNBs and UEs can apply Listen-Before-Talk (LBT) before transmitting in cells with shared frequency channel access. LBT is incorporated in the channel access procedure performed by the Physical (PHY) layer of the gNBs and UEs (see, for example, 3GPP RFC3111). The PHY layer supports multiple channel access procedures. The channel access procedure is a sensing-based procedure that evaluates the availability of a channel for transmissions. Here, a channel refers to a carrier or a part of a carrier consisting of a contiguous set of resource blocks (RBs) on which the channel access procedure is performed in the shared frequency. The basic unit of sensing in NR-U is a duration T of 9 microseconds (μs). sl The sensing slot duration T sl is a time slot duration during which the gNB or UE senses the channel and the detected power for at least 4 μs within the sensing slot duration is greater than or equal to the energy detection threshold XThresh If it is determined that the sensing slot period T sl is considered to be busy. The channel access procedure includes a downlink (DL) channel access procedure performed by the gNB and an uplink (UL) channel access procedure performed by the UE. The DL channel access procedure includes a Type 1 DL channel access procedure and multiple Type 2 DL channel access procedures. The UL channel access procedure includes a Type 1 UL channel access procedure and multiple Type 2 UL channel access procedures. In the Type 1 DL channel access procedure and the Type 1 UL channel access procedure, the time duration spanning multiple sensing slots sensed as idle before DL or UL transmission is random. In contrast, in the Type 2 DL channel access procedure and the Type 2 UL channel access procedure, the time duration spanning multiple sensing slots sensed as idle before DL or UL transmission is deterministic. The Type 2 DL channel access procedure includes Type 2A, Type 2B, and Type 2C. Similarly, the Type 2 UL channel access procedure includes Type 2A, Type 2B, and Type 2C. The Type 1 DL channel access procedure can be applied to any transmission initiated by the gNB. In the Type 1 DL channel access procedure, the gNB resets a counter N to an initial value N init Set the initial value N init 0 to CW p The gNB decrements the counter N when it senses that the channel is idle for a certain period of time. The gNB decrements the counter N when it senses that the channel is idle for a certain period of time. dAfter first sensing that the channel is idle for a sensing slot duration, and after counter N reaches zero, DL transmission can occur. The Type 2A DL channel access procedure is applicable for gNB initiated transmissions using discovery bursts only or multiplexed with non-unicast information. The duration of the transmissions is up to 1 ms and the duty cycle of the discovery bursts is up to 1 / 20. In addition, the Type 2A DL channel access procedure is applicable for shared channel occupancy where the gNB transmits with a gap of 25 μs following the UE transmissions. Channel occupancy refers to the transmission(s) on the channel by the gNB or UE after performing the channel access procedure. Channel occupancy time (COT) refers to the total time that the gNB or UE and the gNBs or UEs sharing the channel occupancy transmit on the channel after the gNB or UE performs the channel access procedure. The channel occupancy time can be shared between the gNB and the corresponding UE(s) for transmission. In the Type 2A DL channel access procedure, the gNB must maintain a sensing interval T short_dl After sensing that the channel is idle for T, DL transmission can be performed immediately. short_dl is the duration T of 16 μs. f and one sensing slot (9 μs) immediately following it. f is T f The sensing slot (9 μs) is included at the beginning of T short_dl If two sensing slots of are sensed as idle, the channel is short_dl is considered idle for The Type 2B DL ​​channel access procedure is applicable in shared channel occupation where the gNB transmits with a gap of 16 μs following the UE transmission(s). In the Type 2B DL ​​channel access procedure, the gNB f After sensing that the channel is idle within the T f is T f If at least 4 μs of sensing occurs in a sensing slot and the channel is sensed idle for a total of 5 μs, the channel is sensed idle for duration T f is considered idle for The Type 2C DL channel access procedure is applicable in shared channel occupation where the gNB transmits with a gap of up to 16 μs following the UE transmission(s). When the gNB performs DL transmission according to the Type 2C DL channel access procedure, the gNB does not sense the channel before the DL transmission. The corresponding DL transmission duration is up to 584 μs. The Type 1 UL channel access procedure applies to PUSCH / SRS transmissions scheduled or configured by the gNB, PUCCH transmissions scheduled or configured by the gNB, and transmissions related to random access procedures. Type 2 UL channel access procedures include Type 2A, Type 2B, and Type 2C. The UE performs Type 2A, Type 2B, or Type 2C UL channel access procedures when instructed by the gNB. In the Type 1 UL channel access procedure, the UE resets the counter N to the initial value N init Set the initial value N init 0 to CW p The counter N is a random number uniformly distributed between . The UE decrements the counter N when it senses that the channel is idle for a certain period of time. The UE decrements the counter N when it senses that the channel is idle for a certain period of time.d After first sensing that the channel is idle for a sensing slot duration, and after counter N reaches zero, a UL transmission can occur. In the Type 2A UL channel access procedure, the UE shall maintain a sensing interval T short_ul After sensing that the channel is idle for T, the UL transmission can be made immediately. short_ul is the duration T of 16 μs. f and one sensing slot (9 μs) immediately following it. f is T f The head of the T short_ul If two sensing slots of are sensed as idle, the channel is short_ul is considered idle for In the Type 2B UL channel access procedure, the UE f After sensing that the channel is idle within the T f is T f If at least 4 μs of sensing occurs in a sensing slot and the channel is sensed idle for a total of 5 μs, the channel is sensed idle for duration T f is considered idle for When a Type 2C UL channel access procedure is instructed for a UL transmission, the UE does not sense the channel before the UL transmission. The duration of the corresponding UL transmission is up to 584 μs. The UE Medium Access Control (MAC) layer supports consistent uplink LBT failure detection and recovery procedures (see, for example, Chapter 4.2 of 3GPP TS 2013-010012, Chapter 5.6.1 of 3GPP TS 2013-010012, and Chapter 5.21.2 of 3GPP TS 2013-010012). If the UE fails to access the channel before making an intended UL transmission to the gNB, Layer 1 (i.e., PHY layer) notifies the higher layer (i.e., MAC layer) of a channel access failure, i.e., an LBT failure. This notification sent from the UE PHY layer to the UE MAC layer is called an LBT failure indication. The UE MAC layer (specifically, the MAC entity) detects consistent uplink LBT failure based on receiving LBT failure indications from the PHY layer. The detection is performed per bandwidth part (BWP) and is based on all uplink transmissions within this BWP. Consistent uplink LBT failure recovery works as follows: If consistent LBT failure(s) is detected on a Secondary Cell(s) (SCell(s)), the UE (MAC entity) reports it to the corresponding gNB via a MAC Control Element (CE) on a serving cell different from the SCell(s) where the failure was detected. The corresponding gNB is the Master Node (MN) for the Master Cell Group (MCG) or the Secondary Node (SN) for the Secondary Cell Group (SCG). This MAC CE is called the LBT failure MAC CE. If there are no resources to transmit the LBT failure MAC CE, the UE can send a Scheduling Request (SR). If a consistent LBT failure is detected in a Special Cell (SpCell), the UE switches to another UL BWP with configured Random Access Channel (RACH) resources in that cell, initiates RACH, and reports the failure via an LBT failure MAC CE. The SpCell is the Primary Cell (PCell) of the MCG or the Primary SCG Cell (PSCell) of the SCG. In the case of a PSCell, if consistent LBT failures are detected in all UL BWP(s) with configured RACH resources, the UE declares a Radio Link Failure (RLF) for that SCG (SCG RLF) and reports the failure to the MN via an SCGFailureInformation message. In the case of a PCell, if consistent LBT failures are detected in all UL BWP(s) with configured RACH resources, the UE declares an RLF for that MCG (MCG RLF). The UE Radio Resource Control (RRC) layer receives configuration information (lbt-FailureRecoveryConfig) for consistent UL LBT failure detection and recovery from the gNB. The configuration information lbt-FailureRecoveryConfig is a per-BWP configuration, is included in BWP-UplinkDedicated in ServingCellConfig of each serving cell (SpCell or SCell) in CellGroupConfig, and is provided to the UE RRC layer via an RRCReconfiguration message. The configuration information lbt-FailureRecoveryConfig includes lbt-FailureInstanceMaxCount and lbt-FailureDetectionTimer for consistent LBT failure detection. The UE RRC layer configures FailureInstanceMaxCount and lbt-FailureDetectionTimer in the UE MAC layer. The parameter FailureInstanceMaxCount indicates the number of LBT failure indications that need to be received from the PHY layer for the MAC layer to detect or trigger a consistent LBT failure. On the other hand, the parameter lbt-FailureDetectionTimer defines the length of the LBT failure detection timer that is started by the MAC layer in response to receiving an LBT failure indication. The MAC layer (specifically, the MAC entity) increments an LBT failure indication counter (LBT_COUNTER) and starts or restarts the LBT failure detection timer in response to receiving an LBT failure indication from the PHY layer. When the LBT failure indication counter is equal to or greater than the value specified by FailureInstanceMaxCount, the MAC layer detects or triggers a consistent uplink LBT failure. On the other hand, the MAC layer resets the LBT failure indication counter in response to expiration of the LBT failure detection timer.That is, the MAC layer counts successively received LBT failure indications, each received at an interval shorter than the time defined by lbt-FailureDetectionTimer, and if the count reaches the value defined by FailureInstanceMaxCount, the MAC layer detects or triggers a consistent uplink LBT failure. The following paragraphs describe the current status of 3GPP discussions on sidelink in unlicensed or shared frequencies. The 3GPP Technical Specification Group (TSG) Radio Access Network (RAN) Working Group #2 (WG2) discussed consistent SL LBT failure detection and recovery procedures for SL-U and agreed on the following (see Non-Patent Document 5): (1) SL-specific LBT failure indication from the PHY layer is necessary for SL-specific consistent LBT failure detection at the MAC layer. (2) SL-specific consistent LBT failure detection and recovery procedures are supported in the SL-U MAC. (3) We further explore the granularity of SL LBT failure detection. (4) As a general principle, we reuse the NR-U consistent LBT failure detection procedure as a baseline for SL-specific consistent LBT failure detection in SL-U. (5) Similar to NR-U, for SL-specific consistent LBT failure detection in SL-U, the following parameters and variables are introduced as baseline: SL-specific LBT failure indication counter (e.g., SL_LBT_COUNTER), SL-specific maximum LBT failure instance count threshold (e.g., sl-LBT-FailureInstanceMaxCount), and SL-specific LBT failure detection timer (e.g., sl-LBT-FailureDetectionTimer). (6) The following MAC operations related to timer / counter processing in NR-U are reused as a baseline for the SL-U's SL-specific consistent LBT failure detection procedure. (6-1) Similar to NR-U, when an SL-specific LBT failure indication is received from a lower layer, an SL-specific LBT failure indication counter (e.g., SL_LBT_COUNTER) is incremented by one. (6-2) Similar to NR-U, when an SL-specific LBT failure indication is received from a lower layer, an SL-specific LBT failure detection timer (e.g., sl-LBT-FailureDetectionTimer) is started or restarted. (6-3) Similar to NR-U, if an SL-specific LBT failure indication counter is equal to or greater than an SL-specific threshold (e.g., sl-LBT-FailureInstanceMaxCount), a consistent LBT failure is triggered or declared by the MAC entity. (6-4) Similar to NR-U, when an SL-specific LBT failure detection timer (e.g., sl-LBT-FailureDetectionTimer) expires, an SL-specific LBT failure indication counter (e.g., SL_LBT_COUNTER) is reset to 0. (6-5) Similar to NR-U, when the SL-specific maximum LBT failure instance count threshold (e.g., sl-LBT-FailureInstanceMaxCount) or the SL-specific LBT failure detection timer (e.g., sl-LBT-FailureDetectionTimer) is reconfigured, the SL-specific LBT failure indication counter (e.g., SL_LBT_COUNTER) is reset to 0. 3GPP TSG-RAN WG2 is considering the granularity of the MAC layer's detection of SL-specific LBT failure indication, which is assumed to be per SL BWP, per SL resource pool, or per Resource Block (RB) set (see Non-Patent Document 6). Regarding this granularity, 3GPP TSG-RAN Working Group #1 (WG1) states that it is effective to indicate which SL resource pool or which RB set in the SL BWP a failure was detected for PSCCH / PSSCH / PSFCH, and which RB set(s) in the SL BWP a failure was detected for S-SSB (see Non-Patent Document 7). PSCCH is an abbreviation for Physical Sidelink Control Channel. PSSCH is an abbreviation for Physical Sidelink Shared Channel. PSFCH is an abbreviation for Physical Sidelink Feedback Channel. S-SSB is an abbreviation for Sidelink Synchronization Signal (SLSS) / Physical Sidelink Broadcast Channel (PSBCH) block, or sidelink synchronization signal block. 3GPP TS 37.213 V17.4.0 (2022-12) "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical layer procedures for shared spectrum channel access (Release 17)", January 2023 3GPP TS 38.300 V17.3.0 (2022-12) "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; NR and NG-RAN Overall Description; Stage 2 (Release 17)", January 2023 3GPP TS 38.321 V17.3.0 (2022-12) "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Medium Access Control (MAC) protocol specification (Release 17)", January 2023 OPPO, "WID revision: NR sidelink evolution", RP-222806, 3GPP TSG-RAN Meeting #98-e, December 12-16, 2022 vivo, "Summary of [AT119bis-e]

[0504] [V2X / SL] Consistent SL LBT failure (vivo)", R2-2210935, 3GPP TSG-RAN WG2 Meeting #119bis-e, October 2022RAN2, "LS on SL LBT failure indication and consistent SL LBT failure", R2-2210936, 3GPP TSG-RAN WG2 Meeting #119bis-e, October 2022vivo [RAN1], "[DRAFT] Reply LS on SL LBT failure indication and consistent SL LBT failure", R1-2212828, 3GPP TSG-RAN WG1 Meeting #111, Toulouse, November 14-18, 2022 The inventors have investigated consistent sidelink LBT failure detection and recovery and found various problems. One of these problems relates to providing an improved consistent LBT failure detection mechanism suitable for sidelink transmissions on shared frequencies. Specifically, in NR-U, LBT failures due to all types of uplink transmissions are considered for consistent uplink LBT failure detection. In contrast, in SL-U, it may not be appropriate or necessary to consider LBT failures due to all types of sidelink transmissions for consistent sidelink LBT failure detection. For example, it is not clear enough how to properly handle a channel access failure (or LBT failure) detected before an S-SSB transmission when the S-SSB is outside the sidelink resource pool or RB set. Specifically, the S-SSB is periodically transmitted in a slot not included in the resource pool within the SL BWP. Therefore, it is not clear whether the LBT failure related to the S-SSB transmission can be counted by a counter per resource pool or per RB set in the resource pool. In addition, the time and frequency domain location of the S-SSB is preset and cannot be arbitrarily changed. Therefore, even if an LBT failure occurs in the channel or resource where the S-SSB is transmitted, the time and frequency domain location of the S-SSB cannot be changed for recovery. For this reason, there may be little need to consider the LBT failure occurring for the S-SSB transmission for consistent SL LBT failure detection. Also, it is not clear enough how to properly handle channel access failure (or LBT failure) detected before PSFCH transmission. Specifically, if more than one PSFCH opportunity is configured per PSCCH / PSSCH transmission, this is like LBT failure recovery at the PHY layer. Therefore, it may be redundant for the MAC layer to detect consistent SL LBT failure and trigger recovery operation based on the LBT failure that occurred for PSFCH transmission. One of the objectives to be achieved by the embodiments disclosed in this specification is to provide an apparatus, a method, and a program that contribute to providing an improved consistent LBT failure detection mechanism suitable for sidelink transmission. It should be noted that this objective is only one of the objectives to be achieved by the embodiments disclosed in this specification. Other objectives or problems and novel features will become apparent from the description of this specification or the accompanying drawings. In a first aspect, a wireless terminal is configured to perform consistent sidelink LBT failure detection, more specifically, to take channel access failures for sidelink transmissions of a first type into account for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. In a second aspect, a method performed by a wireless terminal includes (a) taking into account channel access failures for sidelink transmissions of a first type for consistent sidelink LBT failure detection, and (b) ignoring channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. In a third aspect, the RAN node is configured to transmit configuration information for consistent sidelink LBT failure detection to a wireless terminal, the configuration information causing the wireless terminal to take channel access failures for sidelink transmissions of a first type into account for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. In a fourth aspect, a method performed by a RAN node includes transmitting configuration information for consistent sidelink LBT failure detection to a wireless terminal, the configuration information causing the wireless terminal to take channel access failures for sidelink transmissions of a first type into account for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. In a fifth aspect, a wireless terminal is configured to perform consistent sidelink LBT failure detection, more specifically, to take into account channel access failures detected in a sidelink channel access procedure of a first type in the consistent sidelink LBT failure detection and to ignore channel access failures detected in a sidelink channel access procedure of a second type in the consistent sidelink LBT failure detection. In a sixth aspect, a method performed by a wireless terminal includes (a) taking into account channel access failures detected in a sidelink channel access procedure of a first type in a consistent sidelink LBT failure detection, and (b) ignoring channel access failures detected in a sidelink channel access procedure of a second type in said consistent sidelink LBT failure detection. In a seventh aspect, the RAN node is configured to transmit configuration information for consistent sidelink LBT failure detection to a wireless terminal, the configuration information causing the wireless terminal to take channel access failures detected in a sidelink channel access procedure of a first type into account in the consistent sidelink LBT failure detection and to ignore channel access failures detected in a sidelink channel access procedure of a second type in the consistent sidelink LBT failure detection. In an eighth aspect, a method performed by a RAN node includes transmitting configuration information for consistent sidelink LBT failure detection to a wireless terminal, the configuration information causing the wireless terminal to take channel access failures detected in a sidelink channel access procedure of a first type into account in the consistent sidelink LBT failure detection and to ignore channel access failures detected in a sidelink channel access procedure of a second type in the consistent sidelink LBT failure detection. In a ninth aspect, the wireless terminal is configured to apply a specific type of sidelink channel access procedure to a second sidelink transmission of the wireless terminal following a first sidelink transmission of the other wireless terminal in a shared channel occupancy with the other wireless terminal, the wireless terminal not sensing the channel prior to the second sidelink transmission if the wireless terminal follows the specific type of sidelink channel access procedure. In a tenth aspect, a method performed by a wireless terminal includes, when in shared channel occupancy with another wireless terminal, applying a specific type of sidelink channel access procedure to a second sidelink transmission of the wireless terminal subsequent to a first sidelink transmission of the other wireless terminal, wherein the wireless terminal does not sense the channel prior to the second sidelink transmission if the wireless terminal follows the specific type of sidelink channel access procedure. In an eleventh aspect, a program includes a set of instructions (software code) that, when loaded into a computer, causes the computer to perform the operations or methods of the wireless terminal or RAN node described in the above aspects. According to the above-described aspects, it is possible to provide an apparatus, a method, and a program that contribute to providing an improved mechanism for consistent LBT failure detection suitable for sidelink transmission. FIG. 1 illustrates an example configuration of a wireless communication system according to one or more embodiments; FIG. 2 illustrates a flowchart of an example operation of a UE according to one or more embodiments; FIG. 3 illustrates a flowchart of an example operation of a UE PHY layer according to one or more embodiments; FIG. 4 illustrates a sequence diagram of an example operation of a UE PHY layer and a UE MAC layer according to one or more embodiments; FIG. 5 illustrates a sequence diagram of an example operation of a UE and a RAN node according to one or more embodiments; FIG. 6 illustrates a flowchart of an example operation of a UE according to one or more embodiments; FIG. 7 illustrates a flowchart of an example operation of a UE PHY layer according to one or more embodiments; FIG. 8 illustrates a sequence diagram of an example operation of a UE PHY layer and a UE MAC layer according to one or more embodiments; FIG. 9 illustrates a flowchart of an example operation of a UE MAC layer according to one or more embodiments; FIG. 10 illustrates a sequence diagram of an example operation of a UE PHY layer and a UE MAC layer according to one or more embodiments; FIG. 11 illustrates a block diagram of an example configuration of a UE according to one or more embodiments; FIG. 12 illustrates a block diagram of an example configuration of a RAN node according to one or more embodiments; In the following, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and duplicated descriptions will be omitted as necessary for clarity of explanation. The multiple embodiments described below can be implemented independently or in appropriate combination. These multiple embodiments have different novel features. Therefore, these multiple embodiments contribute to solving different objects or problems and provide different effects. Each drawing is merely an example for describing one or more embodiments. Each drawing may relate not only to one particular embodiment, but to one or more other embodiments. As will be understood by those skilled in the art, various features or steps described with reference to any one drawing may be combined with features or steps shown in one or more other drawings to create an embodiment not explicitly shown or described, for example. Not all features or steps shown in any one drawing are necessary to describe an exemplary embodiment, and some features or steps may be omitted. The order of steps described in any drawing may be changed as appropriate. The following embodiments are described mainly for the 3GPP 5th generation mobile communication system (5G system). However, these embodiments may be applied to other wireless communication systems that support D2D communication technologies similar to NR sidelink communication. As used herein, depending on the context, "if" may be interpreted as meaning "when," "at or around the time," "after," "upon," "in response to determining," "in accordance with a determination," or "in response to detecting." These expressions may be interpreted to have the same meaning, depending on the context. First, the configuration and operation of a number of network elements common to a number of embodiments will be described. Fig. 1 shows an example of the configuration of a wireless communication system related to a number of embodiments. Each element (network function) shown in Fig. 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an application platform. A Radio Access Network (RAN) node (e.g., gNB) 2 manages a cell 21 and can perform cellular communication (101 and 102) with multiple wireless terminals (UEs) 1 including UE 1A and UE 1B using a cellular communication technology (i.e., NR Radio Access Technology). The cellular communication 101 uses an air interface (e.g., Uu interface) between the RAN node 2 and the UE 1A. Similarly, the cellular communication 102 uses an air interface (e.g., Uu interface) between the RAN node 2 and the UE 1B. In the example of FIG. 1, for simplicity of explanation, the UE 1A and UE 1B are located in the same cell 21, but such an arrangement is only an example. For example, the UE 1A may be located in one cell of two adjacent cells managed by different RAN nodes 2, and the UE 1B may be located in the other cell. Alternatively, one or both of UE1A and UE1B may be located outside the coverage (i.e., partial coverage, out-of-coverage) of one or more RAN nodes 2. Hereinafter, when describing matters common to multiple UEs including UE1A and UE1B, UE1 will be referred to unless otherwise specified. UE1 may be UE1A, UE1B, or another UE. The RAN node 2 may be a Next generation Radio Access Network (NG-RAN) node. The NG-RAN node may be a gNB or an ng-eNB. The ng-eNB is a node that provides E-UTRA user plane and control plane protocol termination to the UE and is connected to a 5G Core Network (5GC) via an NG interface. The RAN node 2 may be a Central Unit (e.g. gNB-CU) in a cloud RAN (C-RAN) deployment, or a combination of a CU and one or more Distributed Units (e.g. gNB-DUs). The C-RAN is also referred to as a CU / DU split. Furthermore, the CU may include a Control Plane (CP) Unit (e.g. gNB-CU-CP) and one or more User Plane (UP) Units (e.g. gNB-CU-UP). Thus, the RAN node 2 may be a CU-CP or a combination of a CU-CP and a CU-UP. The CU may be a logical node that hosts the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols of the gNB (or the RRC and PDCP protocols of the gNB). The DU may be a logical node that hosts the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the gNB. UE 1 has at least one radio transceiver and is configured for cellular communication (101 or 102) with RAN node 2. UE 1A and UE 1B are configured for D2D communication (i.e., sidelink communication) over a UE-to-UE direct interface (i.e., NR PC5 interface or NR sidelink) 103. The sidelink communication includes unicast mode communication (sidelink unicast) and may further include one or both of groupcast mode communication and broadcast mode communication. As already explained, D2D communication can be integrated with or supported by a cellular network. D2D communication supported by a cellular network can be used for, for example, V2X services, and other applications and services (eg, public safety applications). The interface between UEs used for the control plane and user plane for D2D communication is called the PC5 interface (or reference point). D2D communication over the PC5 interface is called sidelink communication. The PC5 interface can be based on E-UTRA sidelink capabilities and can also be based on 5G NR sidelink capabilities. D2D communication over the E-UTRA-PC5 (or LTE-based PC5) interface (or sidelink communication) is connectionless, i.e., in broadcast mode at the AS layer. In contrast, sidelink communication over the NR PC5 interface supports unicast, groupcast, and broadcast modes at the AS layer. NR sidelink communication over the NR PC5 interface 103 supports two resource allocation modes: Mode 1 and Mode 2. In resource allocation Mode 1, the RAN node 2 (e.g., gNB) performs the resource allocation. For example, the RAN node 2 allocates or schedules SL radio resources to the UE 1 using the NR Uu interface 101. Resource allocation according to Mode 1 includes dynamic grants and configured grants. In the case of dynamic grant, the UE1 needs to request resources from the RAN node 2 for the transmission of every single transport block. More specifically, the UE1 transmits a MAC Control Element (CE) (i.e., Sidelink BSR MAC CE) indicating a sidelink buffer status report (BSR) to the RAN node 2 via the Uplink Shared Channel (UL-SCH) and the Physical Uplink Shared Channel (PUSCH), and the RAN node 2 transmits a Downlink Control Information (DCI) indicating a dynamic sidelink grant to the UE1 via the Physical Downlink Control Channel (PDCCH). The dynamic sidelink grant provides resource allocation for the transmission (and retransmission) of one transport block. Note that if sidelink carrier aggregation is configured, the dynamic sidelink grant may provide resource allocation for one transport block per sidelink (component) carrier. In the case of configured grant, the RAN node 2 grants the UE 1 periodic sidelink resources configured semi-statically by RRC. More specifically, the UE 1 may transmit UE assistance information to the RAN node 2 regarding the traffic pattern of the sidelink communication. Such UE assistance information, or the sidelink traffic pattern information sent in the UE assistance information, may be referred to as configured grant assistance information. The sidelink traffic pattern information (or configured grant assistance information) may indicate, for example, a maximum transport block size based on the observed traffic pattern, an estimated timing of packet arrival in the sidelink logical channel, and an estimated data arrival period in the sidelink logical channel. The UE 1 transmits the UE assistance information including the sidelink traffic pattern information using an RRC message (e.g., UE assistance information message). The RAN node 2 may generate the configured grant taking into account the sidelink traffic pattern information received from the UE 1. The RAN node 2 sends the configured grant to the UE1 using an RRC message (eg, RRCReconfiguration message). The configured grant indicates the allocation of time and frequency resources and the periodicity of the resource allocation. There are two types of configured grants for Mode 1. In configured grant type 1, the configured grant is configured or released to the UE1 by RRC signaling and can be used immediately. In configured grant type 2, the RAN node 2 configures the configured grant to the UE1 via RRC signaling and activates or deactivates the configured grant via DCI signaling. The UE1 can use the periodic resources allocated in the configured grant only after it is activated by the RAN node 2 and until it is deactivated. On the other hand, in resource allocation mode 2, UE1 autonomously selects radio resources based on sensing by UE1. In this case, both UE1A and UE1B performing sidelink communication can operate outside the network coverage. Resource allocation mode 2 is also called mode 2 resource selection. Here, the radio resources are one or more sub-channels. One sub-channel includes multiple resource blocks in one slot. Sensing is performed in a pre-configured resource pool. The resource pool is (pre-)configured by the network (i.e., RAN node 2) when UE1 is in network coverage. UE1 can select these resources for sidelink transmission and retransmission if the resources are not used by other UEs for high priority traffic. UE1 can transmit and retransmit a certain number of times on the selected resources until a cause for resource reselection is triggered. In resource allocation mode 2, inter-UE coordination may be performed to assist resource selection. The inter-UE coordination enables UE 1A to assist UE 1B in mode 2 resource selection. UE 1A and UE 1B may support at least inter-UE coordination scheme 1. UE 1A and UE 1B may support inter-UE coordination scheme 2. In the inter-UE coordination scheme 1, the inter-UE coordination information transmitted from UE 1A to UE 1B indicates one or both of a set of preferred and non-preferred resources for the transmission of UE 1B. In scheme 1, for example, UE 1B may (re)select resources for sidelink transmission by UE 1B based at least on the inter-UE coordination information from UE 1A. More specifically, UE 1B may select resources for sidelink transmission from an intersection of a set of candidate resources obtained by sensing by UE 1B and a set of recommended resources indicated in the inter-UE coordination information. Alternatively, UE 1B may exclude a set of non-recommended resources indicated in the inter-UE coordination information from the set of candidate resources obtained by sensing by UE 1B, and perform resource selection from the final candidate resource set. Meanwhile, in scheme 2, the inter-UE coordination information transmitted from UE 1A to UE 1B indicates the presence of an expected or potential resource conflict on the resource(s) indicated (or reserved) by the Sidelink Control Information (SCI) of UE 1B. Additionally or alternatively, in scheme 2, the inter-UE coordination information transmitted from UE 1A to UE 1B indicates the presence of a resource conflict detected by UE 1A on the resource(s) indicated (or reserved) by the SCI of UE 1B. In scheme 2, for example, UE 1B can determine the resource to be reselected or the need for retransmission based at least on the inter-UE coordination information from UE 1A. Physical channels and signals transmitted in the NR sidelink include S-SSB, PSCCH, PSSCH, and PSFCH, among other signals. The PSCCH includes the 1st-stage SCI (e.g., SCI format 1-A). The 1st-stage SCI includes control information associated with the PSSCH and the 2nd-stage SCI (e.g., SCI format 2-A, 2-B). The 1st-stage SCI indicates the frequency resources (e.g., subchannels) of the PSSCH for the current (re)transmission of a Transport Block (TB), as well as resource reservation for up to two retransmissions of the TB. The 1st-stage SCI includes the priority of the associated PSSCH, as well as the format and size of the 2nd-stage SCI I. Furthermore, the 1st-stage SCI indicates a resource reservation interval when UE1 reserves PSSCH resources for future transmissions of other transport blocks. The resource reservation interval is also called the resource reservation period. The resource reservation interval indicates that the same set of subchannels as indicated in the 1st-stage SCI are also reserved for PSSCH transmissions in multiple slots that occur periodically in the resource reservation interval. The 1st-stage SCI indicates the Modulation and Coding Scheme (MCS) of the data payload carried in the associated PSSCH. In addition, the 1st-stage SCI indicates which PSSCH Demodulation Reference Signal (DMRS) time pattern is used for the associated PSSCH and may indicate the number of ports of the PSSCH DMRS. The PSCCH is multiplexed in the same slot as the associated PSSCH and in resources (i.e., RBs) that do not overlap with the associated PSSCH. The PSSCH is used to transmit a data payload consisting of the 2nd-stage SCI and the TB. The 2nd-stage SCI carries information used to decode the PSSCH and to support hybrid automatic repeat request (HARQ) feedback and Channel State Information (CSI) reporting. The PSSCH is transmitted in the same slot as the associated PSCCH. The PSFCH is used to send HARQ feedback from the receiving UE to the transmitting UE. In the resource pool, a set of Physical RBs (PRBs) included in the PSFCH symbol available for the PSFCH is indicated using a bitmap. In the resource pool, the PSFCH resources are configured (pre-configured) with a period of 1, 2, or 4 slots. For one PSFCH transmission, one PRB in the PSFCH symbol is used to transmit a cyclic shift code (specifically, a Zadoff-Chu sequence). Code division multiplexing (CDM) using the cyclic shift code (i.e., Zadoff-Chu sequence) is used to distinguish ACK feedback from NACK feedback. Furthermore, CDM is used to multiplex multiple PSFCH transmissions of multiple receiving UEs into one PRB. That is, each PSFCH is mapped to a time resource (i.e., PSFCH symbol), a frequency resource (i.e., one PRB), and a code resource (i.e., Zadoff-Chu sequence) in a slot. The S-SSB is used to transmit the SLSS and PSBCH. The SLSS includes the Sidelink Primary Synchronization Signal (S-PSS) and the Sidelink Secondary Synchronization Signal (S-SSS). The S-SSB occupies one slot and uses the same numerology as configured in the SL BWP, i.e., the same numerology as the PSCCH and PSSCH. The S-SSB is not frequency multiplexed with any other sidelink physical channel in the SL BWP. In other words, the S-SSB is not transmitted in slots in the SL resource pool. In the frequency domain, the S-SSB spans 11 RBs, i.e., 132 subcarriers. The frequency location of the S-SSB is configured in the SL BWP. The UE1 and the RAN node 2 support unlicensed or shared frequency sidelink (SL-U). The UE1 uses a mechanism similar to the channel access of NR-U for unlicensed or shared frequency sidelink. The UE1 can apply LBT before performing transmission on the sidelink with shared frequency channel access. The LBT is incorporated in the channel access procedure performed by the PHY layer of the UE1. The PHY layer of the UE1 supports one or more channel access procedures. The channel access procedure is a sensing-based procedure that evaluates the availability of a channel for transmissions. Here, a channel refers to a carrier or a part of a carrier that consists of a contiguous set of Resource Blocks (RBs) on which the channel access procedure is performed in the shared frequency. In the following, the channel access procedure for SL-U is referred to as a sidelink (SL) channel access procedure. The SL channel access procedure may include a Type 1 SL channel access procedure and a Type 2 SL channel access procedure. In the Type 1 SL channel access procedure, the time duration across multiple sensing slots that are sensed as idle before SL transmission is random. In contrast, in the Type 2 SL channel access procedure, the time duration across multiple sensing slots that are sensed as idle before SL transmission is deterministic. The Type 2 SL channel access procedure may include Type 2A, Type 2B, and Type 2C, as well as Type 2 DL and UL channel access procedures. Examples of details of the Type 1 SL channel access procedure and the Type 2 SL channel access procedure are shown below. Note that these details may be modified as appropriate with future discussions and standardization of the SL channel access procedure in 3GPP. The Type 1 SL channel access procedure may be mainly applied to SL transmission by UE1 that does not have shared channel occupancy. Meanwhile, the Type 2 SL channel access procedure may be mainly used for transmission from UE1 that has shared channel occupancy time (COT) between UEs (i.e., responding UE). Channel occupancy refers to UE1 making SL transmission(s) on a channel after performing a channel access procedure. Channel occupancy time (COT) between UEs refers to the total time that UE1 (e.g., UE1A) and one or more other UEs1 (e.g., UE1B) that share the channel occupancy make SL transmission(s) on a channel after UE1 (e.g., UE1A) performs a channel access procedure. The channel occupancy time can be shared for SL transmission between multiple UEs. The sensing performed in the SL channel access procedure may be similar to that in the DL channel access procedure or the UL channel access procedure in NR-U described in the Background section. The basic unit of sensing in NR-U is a duration T of 9 microseconds (μs). sl The sensing slot duration T sl is a time slot duration during which the gNB or UE senses the channel and the detected power for at least 4 μs within the sensing slot duration is greater than or equal to the energy detection threshold X Thresh If it is determined that the sensing slot period T sl is considered to be busy. Details of the Type 1, Type 2A, Type 2B, and Type 2C SL channel access procedures may be the same as or similar to the Type 1, Type 2A, Type 2B, and Type 2C DL channel access procedures introduced in the Background section, respectively. Alternatively, details of the Type 1, Type 2A, Type 2B, and Type 2C SL channel access procedures may be the same as or similar to the Type 1, Type 2A, Type 2B, and Type 2C UL channel access procedures introduced in the Background section. By way of example and not limitation, details of the Type 1, Type 2A, Type 2B, and Type 2C SL channel access procedures may be as follows: In the Type 1 SL channel access procedure, UE1 sets a counter N to an initial value N init Set the initial value N init 0 to CW p UE1 decrements counter N when it senses that the channel is idle for a certain period of time. UE1 decrements counter N when it senses that the channel is idle for a certain period of time. UE1 decrements counter N when it senses that the channel is idle for a certain period of time. d After first sensing that the channel is idle for a sensing slot duration, and after the counter N reaches zero, a SL transmission can occur. In the Type 2A SL channel access procedure, UE1 must maintain a sensing interval T short_sl After sensing that the channel is idle, the SL transmission can be performed immediately. short_sl is the duration T of 16 μs. f and one sensing slot (9 μs) immediately following it. f is T f The head of the T short_sl If two sensing slots of are sensed as idle, the channel is short_sl is considered idle for In the Type 2B SL channel access procedure, UE1 receives a 16 μs duration Tf After sensing that the channel is idle within the T f is T f If at least 4 μs of sensing occurs in a sensing slot and the channel is sensed idle for a total of 5 μs, the channel is sensed idle for duration T f is considered idle for When UE1 performs SL transmission according to the Type 2C SL channel access procedure, UE1 does not sense the channel before the SL transmission, and the duration of the corresponding UL transmission is up to 584 μs. The MAC layer (specifically, the MAC entity) of UE1 supports consistent sidelink (SL) LBT failure detection and recovery procedures. When UE1 fails to access the channel before performing an intended SL transmission, layer 1 (i.e., PHY layer) of UE1 notifies higher layers (i.e., MAC layer) of a channel access failure, i.e., an LBT failure. This notification sent from the UE PHY layer to the UE MAC layer is called an LBT failure indication, an SL specific LBT failure indication, or an SL LBT failure indication. The UE MAC layer (specifically, the MAC entity) detects a consistent SL LBT failure based on receiving LBT failure indications from the PHY layer. In some implementations, consistent SL LBT failure detection may be performed per resource pool or per one or more RB sets within a SL BWP. An RB set includes contiguous RBs. Consistent SL LBT failure detection may be based on all types of SL transmissions, i.e. all types of sidelink physical channel and signal transmissions. Alternatively, consistent SL LBT failure detection may not take into account LBT failures that occur for some types of SL transmissions. The UE1 may receive configuration information for consistent SL LBT failure detection from the network (e.g., RAN node 2). The configuration information specifies parameters used for consistent sidelink LBT failure detection. These parameters may include an SL-specific maximum LBT failure instance count threshold (e.g., sl-lbt-FailureInstanceMaxCount) and a value of an SL-specific LBT failure detection timer (e.g., sl-lbt-FailureDetectionTimer). The parameter sl-LBT-FailureInstanceMaxCount indicates the number of SL LBT failure indications that need to be received from the PHY layer for the MAC layer of the UE1 to detect or trigger a consistent SL LBT failure. Meanwhile, the parameter sl-lbt-FailureDetectionTimer defines the length of the LBT failure detection timer that is started by the MAC layer in response to receiving an SL LBT failure indication. The MAC layer (specifically, the MAC entity) increments an LBT failure indication counter (SL_LBT_COUNTER) in response to receiving an SL LBT failure indication from the PHY layer, and starts or restarts an LBT failure detection timer. When the LBT failure indication counter is equal to or greater than the value specified by sl-lbt-FailureInstanceMaxCount, the MAC layer detects or triggers a consistent SL LBT failure. On the other hand, the MAC layer resets the LBT failure indication counter in response to expiration of the LBT failure detection timer. That is, the MAC layer counts SL LBT failure indications received one after the other at intervals shorter than the time defined by sl-lbt-FailureDetectionTimer. Then, when the count reaches the value defined by sl-lbtFailureInstanceMaxCount, the MAC layer detects or triggers a consistent SL LBT failure. The following embodiment provides details of consistent SL LBT failure detection. First Embodiment A configuration example of the wireless communication system according to the present embodiment may be the same as the configuration example described with reference to FIG. 1. The UE1 according to the present embodiment performs consistent sidelink LBT failure detection. The UE1 considers or counts channel access failures for the first type of SL transmission for consistent sidelink LBT failure detection. On the other hand, the UE1 ignores, does not consider, or does not count channel access failures (in other words, LBT failures) for the second type of SL transmission in the consistent sidelink LBT failure detection. The first type of SL transmission and the second type of SL transmission are different from each other in the physical channel or physical signal used for the transmission. The first type of SL transmission may include at least a PSSCH transmission. The first type of SL transmission may include at least a PSSCH transmission and a PSCCH transmission. The second type of SL transmission may include at least one or both of an S-SSB transmission and a PSFCH transmission. At least some of the first and second types of SL transmission may be distinguished by the corresponding transport channel instead of the physical channel. For example, the first type of SL transmission may include at least an SL transmission for a SL Shared Channel (SL-SCH), and the second type of SL transmission may include at least an SL for a SL Broadcast Channel (SL-BCH). As described above, UE1 may receive configuration information for consistent SL LBT failure detection from the network (e.g., RAN node 2). The configuration information may indicate whether channel access failures for the second type of SL transmission should be ignored for consistent SL LBT failure detection. UE1 may determine whether to consider or ignore channel access failures for the second type of SL transmission for consistent SL LBT failure detection based on the configuration information. FIG. 2 shows an example of the operation of UE1. In step 201, UE1 initiates consistent sidelink LBT failure detection. UE1 may initiate consistent sidelink LBT failure detection and recovery procedure for sidelinks in an active SL BWP configured with consistent sidelink LBT failure. In step 202, UE1 considers channel access failures for SL transmissions of the first type for consistent sidelink LBT failure detection. In step 203, UE1 ignores channel access failures for SL transmissions of the second type in consistent sidelink LBT failure detection. The order of steps 202 and 203 described in FIG. 2 is for convenience of explanation and is not limited thereto. According to the operation of the UE1 in this embodiment, the LBT failure caused by the second type of SL transmission, in other words, detected in the channel access procedure before the second type of SL transmission, is not considered for consistent SL LBT failure detection. As described above, in the SL-U, it may not be appropriate or necessary to consider the LBT failure caused by all types of SL transmission for consistent sidelink LBT failure detection. Specifically, it may be less necessary to consider the LBT failure caused by the S-SSB transmission for consistent SL LBT failure detection. Additionally or alternatively, it may be redundant for the MAC layer to detect the consistent SL LBT failure and trigger a recovery operation based on the LBT failure caused by the PSFCH transmission. The operation of the UE1 in this embodiment makes it possible to exclude these inappropriate or less necessary LBT failures from consistent SL LBT failure detection. The following provides two specific implementation examples of the operation of UE1 in this embodiment. In the first example, when the PHY layer of UE1 fails to access the channel (i.e., LBT) before the intended SL transmission, it determines whether to notify the MAC layer of UE1 of the channel access failure (i.e., LBT failure) depending on the type of the intended SL transmission. Figure 3 shows an example of the operation of the PHY layer of UE1 in the first example. In step 301, the PHY layer fails to access the channel before the intended SL transmission. If the intended SL transmission is a first type SL transmission, the PHY layer sends a failure indication to the MAC layer (step 302A). On the other hand, if the intended SL transmission is a second type SL transmission, the PHY layer does not notify the MAC layer of the channel access failure (step 302B). In other words, the PHY layer ignores the channel access failure caused by the second type SL transmission, or does not send a failure indication regarding the second type SL transmission to the MAC layer. FIG. 4 shows an example of the operation of the PHY and MAC layers of the UE 1 in the first example. The UE MAC layer 11 may be a MAC entity configured for transmission and reception in the sidelink. In step 410, the UE MAC layer 11 initiates and continues a consistent SL LBT failure detection and recovery procedure. The UE MAC layer 11 performs consistent SL LBT failure detection per resource pool or per one or more RB sets in the SL BWP. The UE MAC layer 11 manages an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer (sl-lbt-FailureDetectionTimer) per resource pool. Alternatively, the UE MAC layer 11 manages an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer (sl-lbt-FailureDetectionTimer) per RB set (set(s)). In step 420, the UE PHY layer 12 detects a channel access failure (LBT failure) before a PSCCH or PSSCH transmission. In response to this detection, in step 421, the UE PHY layer 12 sends a SL LBT failure indication to the UE MAC layer 11. The SL LBT failure indication indicates the SL resource pool identity (e.g., SL resource pool ID) or RB set identity (e.g., RB set identity) where the LBT failure was detected. This makes it easy for the UE MAC layer 11 to determine which LBT failure indication counters to increment and which LBT failure detection timers to restart in response to the SL LBT failure indication. In step 422, in response to receiving the SL LBT failure indication, the UE MAC layer 11 increments the corresponding LBT failure indication counters and starts or restarts the corresponding LBT failure detection timers. In step 430, the UE PHY layer 12 detects a channel access failure (LBT failure) before an S-SSB transmission. In step 431, the UE PHY layer 12 decides not to inform the UE MAC layer 11 of the LBT failure detected before the S-SSB transmission. In step 440, the UE PHY layer 12 detects a channel access failure (LBT failure) before a PSFCH transmission. In step 441, the UE PHY layer 12 decides not to inform the UE MAC layer 11 of the LBT failure detected before the PSFCH transmission. That is, in the example of FIG. 4, the first type of SL transmission is a PSSCH transmission (and a PSCCH transmission), and the second type of SL transmission is an S-SSB transmission and a PSFCH transmission. This classification is an example. For example, one of the S-SSB transmission and the PSFCH transmission may be classified as the first type of SL transmission. In the second example, the PHY layer of UE1 informs the MAC layer of UE1 of LBT failures caused by all types of SL transmissions. In other words, the MAC layer of UE1 sends an LBT failure indication to the MAC layer for every channel access failure (i.e., LBT failure). The MAC layer decides whether to consider the LBT failure indication received from the PHY layer for consistent sidelink LBT failure detection depending on which type of SL transmission the LBT failure indication is related to. One advantage of this example is that it is easy to change the behavior of consistent SL LTB failure detection in the MAC layer based on the configuration information for consistent SL LTB failure detection provided by the upper layer (i.e., RRC layer). 5 shows an example of the operation of the MAC layer of UE1 in the second example. In step 501, the MAC layer receives an LBT failure indication from the PHY layer. If the LBT failure indication is related to a failure occurring in a channel access before a first type of SL transmission, the MAC layer takes this failure indication into account or counts it for consistent sidelink LBT failure detection (step 502A). On the other hand, if the LBT failure indication is related to a failure occurring in a channel access before a second type of SL transmission, the MAC layer ignores, does not take this failure indication into account, or does not count it in consistent sidelink LBT failure detection (step 502B). FIG. 6 shows an example of the operation of the PHY and MAC layers of the UE 1 in the second example. The UE MAC layer 11 may be a MAC entity configured for transmission and reception in the sidelink. In step 610, the UE MAC layer 11 initiates and continues a consistent SL LBT failure detection and recovery procedure. The UE MAC layer 11 performs consistent SL LBT failure detection per resource pool or per one or more RB sets within the SL BWP. The UE MAC layer 11 manages an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer (sl-lbt-FailureDetectionTimer) per resource pool. Alternatively, the UE MAC layer 11 manages an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer (sl-lbt-FailureDetectionTimer) per RB set (set(s)). In step 620, the UE PHY layer 12 detects a channel access failure (LBT failure) before a PSCCH or PSSCH transmission. In response to this detection, in step 621, the UE PHY layer 12 sends an SL LBT failure indication to the UE MAC layer 11. The SL LBT failure indication indicates the SL resource pool ID or RB set identity for which the LBT failure was detected. This makes it easy for the UE MAC layer 11 to determine which LBT failure indication counters to increment and which LBT failure detection timers to restart (or reset) in response to the SL LBT failure indication. Furthermore, the SL LBT failure indication indicates the type of SL transmission intended at the channel access for which the LBT failure was detected. This makes it easy for the UE MAC layer 11 to determine whether to consider the SL LBT failure indication for consistent SL LBT failure detection in response to the SL LBT failure indication. In step 622, in response to receiving a SL LBT failure indication for a PSCCH or PSSCH transmission, the UE MAC Layer 11 increments a corresponding LBT failure indication counter and starts or restarts a corresponding LBT failure detection timer. In step 630, the UE PHY Layer 12 detects a channel access failure (LBT failure) before an S-SSB transmission. In response to this detection, in step 631, the UE PHY Layer 12 sends an SL LBT failure indication to the UE MAC Layer 11. Similar to that of step 621, the SL LBT failure indication indicates an identifier of the SL resource pool or RB set in which the LBT failure was detected. Note that in the case of an LBT failure before an S-SSB transmission, the UE PHY Layer 12 may indicate in the LBT failure indication that there is no corresponding resource pool (e.g., "resource pool Null") or no corresponding RB set (e.g., "RB set Null"). Furthermore, the SL LBT failure indication indicates the type of SL transmission intended at the channel access in which the LBT failure was detected. In step 632, in response to receiving the SL LBT failure indication for the S-SSB transmission, the UE MAC Layer 11 ignores the failure indication for the purpose of consistent SL LBT failure detection. The UE MAC Layer 11 does not increment the LBT failure indication counter in response to receiving the failure indication, nor does it (re)start the corresponding LBT failure detection timer. In step 640, the UE PHY Layer 12 detects a channel access failure (LBT failure) before a PSFCH transmission. In response to this detection, in step 641, the UE PHY Layer 12 sends an SL LBT failure indication to the UE MAC Layer 11. Similar to that of step 641, the SL LBT failure indication indicates an identifier of the SL resource pool or RB set for which the LBT failure was detected. Furthermore, the SL LBT failure indication indicates the type of SL transmission intended at the channel access for which the LBT failure was detected. In step 642, in response to receiving the SL LBT failure indication for the PSFCH transmission, the UE MAC Layer 11 ignores the failure indication for the purpose of consistent SL LBT failure detection. The UE MAC Layer 11 does not increment an LBT failure indication counter in response to receiving the failure indication, nor does it (re)start a corresponding LBT failure detection timer. That is, in the example of Fig. 6, the first type of SL transmission is PSSCH transmission (and PSCCH transmission), and the second type of SL transmission is S-SSB transmission and PSFCH transmission. This classification is an example. For example, one of S-SSB transmission and PSFCH transmission may be classified as the first type of SL transmission. The example of Fig. 6 shows a case where the LBT failure indication indicates the type of intended SL transmission. Alternatively, the LBT failure indication may indicate another identifier for identifying the MAC Protocol Data Unit (PDU) passed from the UE MAC layer 11 to the UE PHY layer 12 for the SL transmission. Alternatively, if the UE MAC layer 11 can determine which type of SL transmission the LBT failure indication relates to based on the reception timing of the LBT failure indication, the LBT failure indication does not need to include an indication for supporting this determination. Also, in case where the second type of SL transmission is only an S-SSB transmission, the UE MAC Layer 11 may recognize that the LBT failure indication is related to an S-SSB transmission based on an indication in the LBT failure indication indicating no corresponding resource pool (e.g., "resource pool Null") or no corresponding RB set (e.g., "RB set Null"). In this case, the LBT failure indication may not include an indication of the type of the planned SL transmission. 7 shows an example of the operation of UE1 and RAN node 2. In step 701, RAN node 2 sends configuration information for consistent SL LBT detection to UE1. The RAN node 2 may send the configuration information to UE1 via RRC signaling common to UEs (e.g., System Information Block (SIB)) or via UE-dedicated RRC signaling (e.g., RRCReconfiguration message). More specifically, the configuration information for consistent SL LBT detection may be included in a configuration related to SL BWP (e.g., SL-BWP-config or SL-BWP-ConfigCommon) or may be included in a configuration related to an SL resource pool in the configuration related to SL BWP (e.g., sl-BWP-PoolConfig or sl-BWP-PoolConfigCommon). In this case, configuration information for consistent SL LBT detection may be provided to UE1 in a SIB Type 12 (SIB12) carrying common configuration for SL BWP or an RRCReconfiguration message carrying individual configuration for SL BWP. The configuration information of step 701 may cause UE1 to consider channel access failures for SL transmissions of the first type for consistent sidelink LBT failure detection and ignore channel access failures for SL transmissions of the second type in consistent sidelink LBT failure detection. As already explained, the configuration information of step 701 may indicate whether channel access failures for SL transmissions of the second type should be ignored for consistent SL LBT failure detection. UE1 may decide based on this configuration information whether to consider or ignore channel access failures for SL transmissions of the second type for consistent SL LBT failure detection. The configuration information of step 701 may include an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer setting (e.g., sl-lbtFailureInstanceMaxCount and sl-lbt-FailureDetectionTimer) for each resource pool. Alternatively, the configuration information of step 701 may include an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer setting (e.g., sl-lbtFailureInstanceMaxCount and sl-lbt-FailureDetectionTimer) for each RB set (set(s)). Second Embodiment A configuration example of the wireless communication system according to the present embodiment may be the same as the configuration example described with reference to FIG. 1. The UE1 according to the present embodiment performs consistent sidelink LBT failure detection. The UE1 considers or counts channel access failures detected in the first type SL channel access procedure in the consistent sidelink LBT failure detection. Meanwhile, the UE1 ignores, does not consider, or does not count channel access failures detected in the second type SL channel access procedure in the consistent sidelink LBT failure detection. The first type SL channel access procedure may be the above-mentioned Type 1 SL channel access procedure. The second type SL channel access procedure may be the above-mentioned Type 2 SL channel access procedure. More specifically, the second type SL channel access procedure may include at least one of the above-mentioned Type 2A SL channel access procedure and Type 2B SL channel access procedure. When performing SL transmission according to the above-mentioned Type 2C SL channel access procedure, the PHY layer of the UE1 does not sense the channel before SL transmission. Therefore, it would be reasonable not to assume channel access failure (i.e., LBT failure) in the Type 2C SL channel access procedure. As described above, UE1 may receive configuration information for consistent SL LBT failure detection from the network (e.g., RAN node 2). The configuration information may indicate whether a channel access failure detected in the second type SL channel access procedure needs to be ignored for consistent SL LBT failure detection. UE1 may determine whether to consider or ignore a channel access failure detected in the second type SL channel access procedure for consistent sidelink LBT failure detection based on the configuration information. FIG. 8 illustrates an example of the operation of UE1. In step 801, UE1 initiates consistent sidelink LBT failure detection. UE1 may initiate consistent sidelink LBT failure detection and recovery procedure for sidelinks in an active SL BWP with consistent sidelink LBT failure configured. In step 802, UE1 considers channel access failures detected in the first type of SL channel access procedure in consistent SL LBT failure detection. In step 803, UE1 ignores channel access failures detected in the second type of SL channel access procedure in consistent SL LBT failure detection. The order of steps 802 and 803 described in FIG. 8 is for convenience of explanation and is not limited thereto. According to the operation of UE1 in this embodiment, the LBT failure detected in the second type channel access procedure is not considered for consistent SL LBT failure detection. As mentioned above, it may not be appropriate or necessary to consider LBT failures due to all types of SL transmissions for consistent sidelink LBT failure detection in SL-U. As mentioned above, it is assumed that the Type 1 SL channel access procedure is mainly applied to SL transmissions by UE1 that do not have shared channel occupancy. In contrast, it is assumed that the Type 2 SL channel access procedure is mainly used for transmissions from UE1 that have shared channel occupation time (COT) between UEs (i.e., responding UE). The failure rate of the Type 2 SL channel access procedure in COT sharing between UEs is considered to be significantly lower than that of the Type 1 SL channel access procedure. In addition, the selection and reservation of resources by UE1 is essentially based on sensing, especially when resource allocation mode 2 is used. Furthermore, it is fully assumed that one or both of the S-SSB transmission and the PSFCH transmission follow a Type 2 SL channel access procedure (e.g., Type 2A SL channel access procedure). Considering these SL-U-specific circumstances, it may be appropriate not to consider an LBT failure detected in a specific type of channel access procedure, specifically, a Type 2 SL channel access procedure, for consistent SL LBT failure detection. The operation of UE1 in this embodiment makes it possible to exclude these inappropriate or less necessary LBT failures from consistent SL LBT failure detection. The following provides two specific implementation examples of the operation of UE1 in this embodiment. In the first example, when the PHY layer of UE1 fails to access the channel (i.e., LBT) before the intended SL transmission, it determines whether to inform the MAC layer of UE1 of the channel access failure (i.e., LBT failure) depending on the type of channel access procedure used. Figure 9 shows an example of the operation of the PHY layer of UE1 in the first example. In step 901, the PHY layer fails to access the channel before the intended SL transmission. If the failure occurs in the first type of SL channel access procedure, the PHY layer sends a failure indication to the MAC layer (step 902A). On the other hand, if the failure occurs in the second type of SL channel access procedure, the PHY layer does not inform the MAC layer of the channel access failure (step 902B). In other words, the PHY layer ignores the channel access failure in the second type of channel access procedure, or does not send a failure indication for the second type of channel access procedure to the MAC layer. FIG. 10 shows an example of the operation of the PHY and MAC layers of the UE 1 in the first example. The UE MAC layer 11 may be a MAC entity configured for transmission and reception in the sidelink. In step 1010, the UE MAC layer 11 initiates and continues a consistent SL LBT failure detection and recovery procedure. The UE MAC layer 11 performs consistent SL LBT failure detection per resource pool or per one or more RB sets in the SL BWP. The UE MAC layer 11 manages an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer (sl-lbt-FailureDetectionTimer) per resource pool. Alternatively, the UE MAC layer 11 manages an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer (sl-lbt-FailureDetectionTimer) per RB set (set(s)). In step 1020, the UE PHY layer 12 detects a channel access failure (LBT failure) in the Type 1 SL channel access procedure. In response to this detection, in step 1021, the UE PHY layer 12 sends an SL LBT failure indication to the UE MAC layer 11. The SL LBT failure indication indicates the SL resource pool ID or RB set identity in which the LBT failure was detected. This makes it easy for the UE MAC layer 11 to determine which LBT failure indication counters to increment and which LBT failure detection timers to restart (or reset) in response to the SL LBT failure indication. In step 1022, in response to receiving the SL LBT failure indication, the UE MAC layer 11 increments the corresponding LBT failure indication counters and starts or restarts the corresponding LBT failure detection timers. In step 1030, the UE PHY layer 12 detects a channel access failure (LBT failure) in the Type 2 SL channel access procedure. In step 1031, the UE PHY layer 12 decides not to inform the UE MAC layer 11 of the LBT failure detected in the Type 2 SL channel access procedure. That is, in the example of Fig. 10, the first type of SL channel access procedure is a Type 1 SL channel access procedure, and the second type of SL channel access procedure is a Type 2 SL channel access procedure. This classification is an example. For example, one of the Type 2A SL channel access procedure and the Type 2B SL channel access procedure may be classified as the first type of SL transmission. In the second example, the PHY layer of UE1 informs the MAC layer of UE1 of LBT failures caused by all types of SL transmissions. In other words, the MAC layer of UE1 sends an LBT failure indication to the MAC layer every time there is a channel access failure (i.e., LBT failure). The MAC layer decides whether to consider the LBT failure indication received from the PHY layer for consistent sidelink LBT failure detection depending on which type of SL channel access procedure the LBT failure indication occurred in. One advantage of this example is that it is easy to change the operation of consistent SL LTB failure detection in the MAC layer based on the configuration information for consistent SL LTB failure detection provided by the upper layer (i.e., RRC layer). 11 shows an example of the operation of the MAC layer of UE1 in the second example. In step 1101, the MAC layer receives an LBT failure indication from the PHY layer. If the LBT failure indication is related to a failure occurring in the SL channel access procedure of the first type, the MAC layer considers or counts the failure indication for the consistent sidelink LBT failure detection (step 1102A). On the other hand, if the LBT failure indication is related to a failure occurring in the SL channel access procedure of the second type, the MAC layer ignores, does not consider, or does not count the failure indication in the consistent sidelink LBT failure detection (step 1102B). FIG. 12 shows an example of the operation of the PHY and MAC layers of the UE 1 in the second example. The UE MAC layer 11 may be a MAC entity configured for transmission and reception in the sidelink. In step 1210, the UE MAC layer 11 initiates and continues a consistent SL LBT failure detection and recovery procedure. The UE MAC layer 11 performs consistent SL LBT failure detection per resource pool or per one or more RB sets in the SL BWP. The UE MAC layer 11 manages an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer (sl-lbt-FailureDetectionTimer) per resource pool. Alternatively, the UE MAC layer 11 manages an LBT failure indication counter (SL_LBT_COUNTER) and an LBT failure detection timer (sl-lbt-FailureDetectionTimer) per RB set (set(s)). In step 1220, the UE PHY layer 12 detects a channel access failure (LBT failure) in the Type 1 SL channel access procedure. In response to this detection, in step 1221, the UE PHY layer 12 sends an SL LBT failure indication to the UE MAC layer 11. The SL LBT failure indication indicates the SL resource pool ID or RB set identity in which the LBT failure was detected. This makes it easy for the UE MAC layer 11 to determine which LBT failure indication counter to increment and which LBT failure detection timer to restart (or reset) in response to the SL LBT failure indication. Furthermore, the SL LBT failure indication indicates the type of the channel access procedure in which the LBT failure was detected (here, Type 1). This makes it easy for the UE MAC layer 11 to determine whether to consider the SL LBT failure indication for consistent SL LBT failure detection in response to the SL LBT failure indication. In step 1222, in response to receiving the SL LBT failure indication for the Type 1 SL channel access procedure, the UE MAC Layer 11 increments a corresponding LBT failure indication counter and starts or restarts a corresponding LBT failure detection timer. In step 1230, the UE PHY layer 12 detects a channel access failure (LBT failure) in the Type 2 SL channel access procedure. In response to this detection, in step 1231, the UE PHY layer 12 sends a SL LBT failure indication to the UE MAC layer 11. Similar to that in step 1221, this SL LBT failure indication indicates an identifier of the SL resource pool or RB set in which the LBT failure was detected. Note that in the case of an LBT failure before an S-SSB transmission, the UE PHY layer 12 may indicate that there is no corresponding resource pool (e.g., "resource pool Null") or that there is no corresponding RB set (e.g., "RB set Null") in the LBT failure indication. Furthermore, the SL LBT failure indication indicates the type of the SL channel access procedure in which the LBT failure was detected (here, Type 2). In step 1232, in response to receiving a SL LBT failure indication for the Type 2 SL channel access procedure, the UE MAC Layer 11 ignores the failure indication for purposes of consistent SL LBT failure detection, and does not increment an LBT failure indication counter in response to receiving the failure indication, nor (re)start a corresponding LBT failure detection timer. That is, in the example of Fig. 12, the first type of SL channel access procedure is a Type 1 SL channel access procedure, and the second type of SL channel access procedure is a Type 2 SL channel access procedure. This classification is an example. For example, one of the Type 2A SL channel access procedure and the Type 2B SL channel access procedure may be classified as the first type of SL transmission. The example of Fig. 12 shows a case where the LBT failure indication indicates the type of SL channel access procedure. Alternatively, if the UE MAC layer 11 can determine which type of channel access procedure the LBT failure indication relates to based on the reception timing of the LBT failure indication, the LBT failure indication does not need to include an indication to assist this determination. Also, in the case where the second type of SL channel access procedure is a Type 2A or Type 2B SL channel access procedure and these SL channel access procedures are used only for S-SSB transmission, the UE MAC Layer 11 may recognize that the LBT failure indication is related to the second type of SL channel access procedure based on an indication in the LBT failure indication indicating that there is no corresponding resource pool (e.g., "resource pool Null") or that there is no corresponding RB set (e.g., "RB set Null"). In this case, the LBT failure indication may not include an indication indicating the type of the SL channel access procedure. Third Embodiment A configuration example of the wireless communication system according to the present embodiment may be the same as the configuration example described with reference to FIG. 1. When a second SL transmission of the UE 1 is performed following a first SL transmission of the other UE in a shared channel occupancy with the other UE (eg, UE 1B), the UE 1 (eg, UE 1A) according to the present embodiment applies a specific type of SL channel access procedure to the second SL transmission. When the UE 1 follows the specific type of SL channel access procedure, the UE 1 does not sense the channel before the second SL transmission, in other words, does not perform LBT. The channel occupancy may be initiated by the other UE (eg, UE 1B) after the channel is sensed to be idle by a channel access procedure with LBT (eg, Type 1 SL channel access procedure) by the other UE (eg, UE 1B). The specific type of SL channel access procedure may be the Type 2C SL channel access procedure described above. In one example, the second sidelink transmission may include a PSSCH transmission (and a PSCCH transmission). This may be particularly beneficial when the consistent SL LBT failure detection considering the type of channel access procedure described in the second embodiment is used, and the first type of SL channel access procedure includes a Type 1 SL channel access procedure, while the second type of SL channel access procedure includes a Type 2A and a Type 2C SL channel access procedure. In this case, even if the Type 2A or Type 2C SL channel access procedure is applied to the PSSCH transmission (and the PSCCH transmission) in the COT sharing between UEs, the LBT failure that occurs is not taken into account in the consistent SL LBT failure detection. In addition, the failure rate of the Type 2 SL channel access procedure in the COT sharing between UEs is considered to be significantly lower than that of the Type 1 SL channel access procedure. For these reasons, it may be reasonable to apply the Type 2C SL channel access procedure without LBT to PSSCH transmissions (and PSCCH transmissions) that follow SL transmissions of other UEs in shared channel occupancy. Next, the following describes configuration examples of the UE 1 and the RAN node 2 according to the above-mentioned embodiments. FIG. 13 is a block diagram showing a configuration example of the UE 1. The Radio Frequency (RF) transceiver 1301 performs analog RF signal processing to communicate with other UEs 1 and the RAN node 2. The RF transceiver 1301 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 1301 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 1301 is coupled to the antenna array 1302 and the baseband processor 1303. The RF transceiver 1301 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1303, generates a transmission RF signal, and provides the transmission RF signal to the antenna array 1302. The RF transceiver 1301 also generates a baseband reception signal based on the reception RF signal received by the antenna array 1302, and provides the baseband reception signal to the baseband processor 1303. The RF transceiver 1301 may include an analog beamformer circuit for beamforming, which may include, for example, multiple phase shifters and multiple power amplifiers. The baseband processor 1303 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) generation / decomposition of transmission format (transmission frame), (d) transmission line coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management of layer 1 (e.g., transmission power control), layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and layer 3 (e.g., signaling related to attachment, mobility, and call management). For example, the digital baseband signal processing by the baseband processor 1303 may include signal processing of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer, and a Physical (PHY) layer. Also, the control plane processing by the baseband processor 1303 may include processing of a Non-Access Stratum (NAS) protocol, a Radio Resource Control (RRC) protocol, MAC Control Elements (CEs), and Downlink Control Information (DCIs). The control plane processing may include processing of PC5-S signaling and PC5-RRC signaling. The baseband processor 1303 may perform Multiple Input Multiple Output (MIMO) encoding and precoding for beamforming. The baseband processor 1303 may include a modem processor (e.g., Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 1304 described later. The application processor 1304 is also called a CPU, MPU, microprocessor, or processor core. The application processor 1304 may include multiple processors (multiple processor cores). The application processor 1304 executes a system software program (operating system (OS)) and various application programs (e.g., a call application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 1306 or other memories, thereby realizing various functions of the UE 1. In some implementations, the baseband processor 1303 and the application processor 1304 may be integrated on a single chip, as shown by the dashed line (1305) in Figure 13. In other words, the baseband processor 1303 and the application processor 1304 may be implemented as a single System on Chip (SoC) device 1305. An SoC device may also be called a system Large Scale Integration (LSI) or a chipset. The memory 1306 is a volatile memory or a non-volatile memory, or a combination thereof. The memory 1306 may include a plurality of physically independent memory devices. The volatile memory is, for example, a static random access memory (SRAM) or a dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is a mask read only memory (MROM), an electrically erasable programmable ROM (EEPROM), a flash memory, or a hard disk drive, or any combination thereof. For example, the memory 1306 may include an external memory device accessible from the baseband processor 1303, the application processor 1304, and the SoC 1305. The memory 1306 may include an internal memory device integrated in the baseband processor 1303, the application processor 1304, or the SoC 1305. Furthermore, the memory 1306 may include a memory in a Universal Integrated Circuit Card (UICC). The memory 1306 may store one or more software modules (computer programs) 1307 including instructions and data for performing the processes described in the above-mentioned embodiments by the UE 1. In some implementations, the baseband processor 1303 or the application processor 1304 may be configured to read the software modules 1307 from the memory 1306 and execute them to perform the processes by the UE 1 described in the above-mentioned embodiments with reference to the drawings. In addition, the control plane processing and operations performed by UE1 described in the above embodiment can be realized by elements other than the RF transceiver 1301 and the antenna array 1302, i.e., at least one of the baseband processor 1303 and the application processor 1304, and the memory 1306 storing the software module 1307. FIG. 14 is a block diagram showing an example of a configuration of a RAN node 2 according to the above embodiment. Referring to FIG. 14, the RAN node 2 includes a Radio Frequency (RF) transceiver 1401, a network interface 1403, a processor 1404, and a memory 1405. The RF transceiver 1401 performs analog RF signal processing to communicate with the UEs 1 and other UEs. The RF transceiver 1401 may include multiple transceivers. The RF transceiver 1401 is coupled to an antenna array 1402 and a processor 1404. The RF transceiver 1401 receives modulation symbol data from the processor 1404, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1402. The RF transceiver 1401 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1402, and provides the baseband receive signal to the processor 1404. The RF transceiver 1401 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers. The network interface 1403 is used to communicate with network nodes (e.g., other RAN nodes, and control and forwarding nodes of the core network). The network interface 1403 may include, for example, a network interface card (NIC) that complies with the IEEE 802.3 series. The processor 1404 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 1404 may include multiple processors. For example, the processor 1404 may include a modem processor (e.g., Digital Signal Processor (DSP)) performing digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) performing control plane processing. The processor 1404 may include a digital beamformer module for beamforming. The digital beamformer module may include a Multiple Input Multiple Output (MIMO) encoder and a precoder. The memory 1405 is configured by a combination of volatile memory and non-volatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. The memory 1405 may include storage located remotely from the processor 1404. In this case, the processor 1404 may access the memory 1405 via the network interface 1403 or other I / O interface. The memory 1405 may store one or more software modules (computer programs) 1406 including instructions and data for performing the processes of the RAN node 2 described in the above embodiments. In some implementations, the processor 1404 may be configured to read and execute the software modules 1406 from the memory 1405 to perform the processes of the RAN node 2 described in the above embodiments. In addition, when the RAN node 2 is a CU (eg, gNB-CU) or a CU-CP (eg, gNB-CU-CP), the RAN node 2 may not include the RF transceiver 1401 (and the antenna array 1402). As described with reference to FIG. 13 and FIG. 14, each of the processors included in the UE 1 and the RAN node 2 according to the above-mentioned embodiment can execute one or more programs including instructions for making a computer execute the algorithms described with reference to the drawings. The programs include instructions (or software codes) for making a computer execute one or more functions described in the embodiments when the programs are loaded into a computer. The programs may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable medium or tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray (registered trademark) disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The programs may be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, the transitory computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals. Furthermore, the above-described embodiment is merely an example of application of the technical idea obtained by the inventor of the present invention. In other words, the technical idea is not limited to the above-described embodiment, and various modifications are possible. For example, some or all of the above embodiments may be described as, but are not limited to, the following appendices. Some or all of the elements (e.g., configurations and functions) described in the appendices directed to an apparatus (e.g., wireless terminal, RAN node) may naturally be described as appendices directed to a method and a program. For example, some or all of the elements described in appendices 2-14 dependent on appendices 1 may also be described as appendices dependent on appendices 20 and 22 due to the same dependency relationship as appendices 2-14. Similarly, some or all of the elements described in appendices 16-19 dependent on appendices 15 may also be described as appendices dependent on appendices 21 and 23 due to the same dependency relationship as appendices 16-19. Some or all of the elements described in any appendice may be applied to various hardware, software, recording means for recording software, systems, and methods. (Appendix 1) A means for performing consistent sidelink Listen-Before-Talk (LBT) failure detection; the means is configured to take into account channel access failures for sidelink transmissions of a first type for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. Wireless terminal. (Appendix 2) the first type of sidelink transmission and the second type of sidelink transmission differ from each other in a physical channel or physical signal used for transmission. 2. The wireless terminal of claim 1. (Appendix 3) The first type of sidelink transmission includes at least a Physical Sidelink Shared Channel (PSSCH) transmission; The second type of sidelink transmission includes at least one or both of a Sidelink Synchronization Signal (S-SS) / Physical Sidelink Broadcast Channel (PSBCH) block (S-SSB) transmission and a Physical Sidelink Feedback Channel (PSFCH) transmission. 3. The wireless terminal of claim 1 or 2. (Appendix 4) The means is configured to perform the consistent sidelink LBT failure detection per resource pool or per one or more Resource Block (RB) sets within a sidelink Bandwidth Part (BWP). 4. A wireless terminal according to claim 1. (Appendix 5) The method further includes receiving configuration information for detecting the consistent sidelink LBT failure from a network, The configuration information indicates whether a channel access failure for the second type of sidelink transmission should be ignored for the consistent sidelink LBT failure detection. 5. A wireless terminal according to any one of claims 1 to 4. (Appendix 6) the means for performing consistent sidelink LBT failure detection is configured to determine, based on the configuration information, whether to take into account or ignore a channel access failure for the second type of sidelink transmission for the consistent sidelink LBT failure detection. 6. The wireless terminal of claim 5. (Appendix 7) The means is configured to provide a Physical (PHY) layer and a Medium Access Control (MAC) layer; the PHY layer is adapted to send a failure indication to the MAC layer upon each channel access failure for the first type of sidelink transmission; the PHY layer is adapted to not inform the MAC layer of a channel access failure for the second type of sidelink transmission; the MAC layer is adapted to detect one or more consistent LBT failures based on receipt of a failure indication from the PHY layer. 7. A wireless terminal according to any one of claims 1 to 6. (Appendix 8) the PHY layer is adapted to indicate, for each failure indication, a resource pool or one or more Resource Block (RB) sets in which a corresponding channel access failure was detected; 8. The wireless terminal of claim 7. (Appendix 9) The means is configured to provide a Physical (PHY) layer and a Medium Access Control (MAC) layer; The PHY layer is adapted to send a failure indication to the MAC layer upon each channel access failure; the MAC layer is adapted to take into account a failure indication received from the PHY layer for the first type of sidelink transmission for the consistent sidelink LBT failure detection, the MAC layer is adapted to ignore failure indications for the second type of sidelink transmission in the consistent sidelink LBT failure detection. 7. A wireless terminal according to any one of claims 1 to 6. (Appendix 10) the PHY layer is adapted to indicate upon each failure indication a type of intended sidelink transmission; 10. The wireless terminal of claim 9. (Appendix 11) the PHY layer is adapted to indicate, for each failure indication, a resource pool or one or more Resource Block (RB) sets in which a corresponding channel access failure was detected; 11. The wireless terminal of claim 9 or 10. (Appendix 12) the second type of sidelink transmission includes at least a Sidelink Synchronization Signal (S-SS) / Physical Sidelink Broadcast Channel (PSBCH) block (S-SSB) transmission; the PHY layer is adapted to indicate, upon each failure indication for an S-SSB transmission, that there is no corresponding resource pool; 11. The wireless terminal of claim 9 or 10. (Appendix 13) The MAC layer is adapted to determine whether to take into account or ignore channel access failures for the second type of sidelink transmission for the consistent sidelink LBT failure detection according to a configuration received from a Radio Resource Control (RRC) layer. 13. The wireless terminal according to any one of claims 9 to 12. (Appendix 14) The consistent sidelink LBT failure detection is related to channel access in a shared frequency. 14. A wireless terminal according to any one of claims 1 to 13. (Appendix 15) A means for transmitting configuration information for detecting a consistent sidelink Listen-Before-Talk (LBT) failure to a wireless terminal, The configuration information causes the wireless terminal to take channel access failures for sidelink transmissions of a first type into account for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. Radio Access Network (RAN) node. (Appendix 16) the first type of sidelink transmission and the second type of sidelink transmission differ from each other in a physical channel or physical signal used for transmission. 16. The RAN node of claim 15. (Appendix 17) The first type of sidelink transmission includes at least a Physical Sidelink Shared Channel (PSSCH) transmission; The second type of sidelink transmission includes at least one or both of a Sidelink Synchronization Signal (S-SS) / Physical Sidelink Broadcast Channel (PSBCH) block (S-SSB) transmission and a Physical Sidelink Feedback Channel (PSFCH) transmission. 17. The RAN node of claim 15 or 16. (Appendix 18) The configuration information indicates whether a channel access failure for the second type of sidelink transmission should be ignored for the consistent sidelink LBT failure detection. 18. The RAN node of any one of Supplementary Notes 15 to 17. (Appendix 19) The configuration information causes the wireless terminal to decide whether to take into account or ignore channel access failures for the second type of sidelink transmission for the consistent sidelink LBT failure detection. 19. The RAN node of claim 18. (Appendix 20) taking into account channel access failures for a first type of sidelink transmission for consistent sidelink Listen-Before-Talk (LBT) failure detection; and and ignoring channel access failures for a second type of sidelink transmission in the consistent sidelink LBT failure detection. A method performed by a wireless terminal comprising: (Appendix 21) transmitting configuration information for consistent sidelink Listen-Before-Talk (LBT) failure detection to a wireless terminal; The configuration information causes the wireless terminal to take channel access failures for sidelink transmissions of a first type into account for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. A method performed by a Radio Access Network (RAN) node. (Appendix 22) A program for causing a computer to perform a method for a wireless terminal, comprising: The method comprises: taking into account channel access failures for a first type of sidelink transmission for consistent sidelink Listen-Before-Talk (LBT) failure detection; and and ignoring channel access failures for a second type of sidelink transmission in the consistent sidelink LBT failure detection. A program that includes: (Appendix 23) A program for causing a computer to perform a method for a Radio Access Network (RAN) node, comprising: The method comprises transmitting configuration information for consistent sidelink Listen-Before-Talk (LBT) failure detection to a wireless terminal; The configuration information causes the wireless terminal to take channel access failures for sidelink transmissions of a first type into account for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. program. (Appendix 24) A means for performing consistent sidelink Listen-Before-Talk (LBT) failure detection; the means is configured to take into account a channel access failure detected in a sidelink channel access procedure of a first type in the consistent sidelink LBT failure detection and to ignore a channel access failure detected in a sidelink channel access procedure of a second type in the consistent sidelink LBT failure detection. Wireless terminal. (Appendix 25) the first type of sidelink channel access procedure is a Type 1 sidelink channel access procedure; The second type of sidelink channel access procedure includes at least one of a Type 2A sidelink channel access procedure and a Type 2B sidelink channel access procedure. 25. The wireless terminal of claim 24. (Appendix 26) The means is configured to perform the consistent sidelink LBT failure detection per resource pool or per one or more Resource Block (RB) sets within a sidelink Bandwidth Part (BWP). 26. The wireless terminal of claim 24 or 25. (Appendix 27) The method further includes receiving configuration information for detecting the consistent sidelink LBT failure from a network, The configuration information indicates whether a channel access failure detected in the second type sidelink channel access procedure should be ignored for the purpose of detecting the consistent sidelink LBT failure. 27. A wireless terminal according to any one of appendix 24 to 26. (Appendix 28) The means for performing consistent sidelink LBT failure detection is configured to determine, based on the configuration information, whether to take into account or ignore a channel access failure detected in the second type sidelink channel access procedure for the consistent sidelink LBT failure detection. 28. The wireless terminal of claim 27. (Appendix 29) The means is configured to provide a Physical (PHY) layer and a Medium Access Control (MAC) layer; the PHY layer is adapted to send a failure indication to the MAC layer for each channel access failure detected in the sidelink channel access procedure of the first type; the PHY layer is adapted to not inform the MAC layer of a channel access failure detected in the second type sidelink channel access procedure; the MAC layer is adapted to detect one or more consistent LBT failures based on receipt of a failure indication from the PHY layer. 29. The wireless terminal according to any one of appendix 24 to 28. (Appendix 30) the PHY layer is adapted to indicate, for each failure indication, a resource pool or one or more Resource Block (RB) sets in which a corresponding channel access failure was detected; 30. The wireless terminal of claim 29. (Appendix 31) The means is configured to provide a Physical (PHY) layer and a Medium Access Control (MAC) layer; The PHY layer is adapted to send a failure indication to the MAC layer upon each channel access failure; the MAC layer is adapted to take into account a failure indication for the first type of sidelink channel access procedure for the consistent sidelink LBT failure detection; The MAC layer is adapted to ignore a failure indication for the second type of sidelink channel access procedure in the consistent sidelink LBT failure detection. 29. The wireless terminal according to any one of appendix 24 to 28. (Appendix 32) the PHY layer is adapted to indicate, upon each failure indication, a type of sidelink channel access procedure; 32. The wireless terminal of claim 31 . (Appendix 33) the PHY layer is adapted to indicate, for each failure indication, a resource pool or one or more Resource Block (RB) sets in which a corresponding channel access failure was detected; 33. The wireless terminal of claim 31 or 32. (Appendix 34) The MAC layer is adapted to determine whether to take into account or ignore a channel access failure detected in the second type of sidelink channel access procedure for the consistent sidelink LBT failure detection according to a configuration received from a Radio Resource Control (RRC) layer. 34. The wireless terminal according to any one of appendix 31 to 33. (Appendix 35) The consistent sidelink LBT failure detection is related to channel access in a shared frequency. 35. The wireless terminal according to any one of appendix 24 to 34. (Appendix 36) A means for transmitting configuration information for detecting a consistent sidelink Listen-Before-Talk (LBT) failure to a wireless terminal, The configuration information causes the wireless terminal to take into account a channel access failure detected in a sidelink channel access procedure of a first type in the consistent sidelink LBT failure detection and to ignore a channel access failure detected in a sidelink channel access procedure of a second type in the consistent sidelink LBT failure detection. Radio Access Network (RAN) node. (Appendix 37) the first type of sidelink channel access procedure is a Type 1 sidelink channel access procedure; The second type of sidelink channel access procedure includes at least one of a Type 2A sidelink channel access procedure and a Type 2B sidelink channel access procedure. 37. The RAN node of claim 36. (Appendix 38) The configuration information indicates whether a channel access failure detected in the second type sidelink channel access procedure should be ignored for the purpose of detecting the consistent sidelink LBT failure. 38. The RAN node of claim 36 or 37. (Appendix 39) The configuration information causes the wireless terminal to determine whether to take into account or ignore a channel access failure detected in the second type of idlink channel access procedure for the consistent sidelink LBT failure detection. 39. The RAN node of claim 38. (Appendix 40) taking into account a channel access failure detected in a first type of sidelink channel access procedure in a consistent sidelink Listen-Before-Talk (LBT) failure detection; and ignoring a channel access failure detected in a second type sidelink channel access procedure in the consistent sidelink LBT failure detection. A method performed by a wireless terminal comprising: (Appendix 41) transmitting configuration information for consistent sidelink Listen-Before-Talk (LBT) failure detection to a wireless terminal; The configuration information causes the wireless terminal to take into account a channel access failure detected in a sidelink channel access procedure of a first type in the consistent sidelink LBT failure detection and to ignore a channel access failure detected in a sidelink channel access procedure of a second type in the consistent sidelink LBT failure detection. A method performed by a Radio Access Network (RAN) node. (Appendix 42) A wireless terminal, means for applying a particular type of sidelink channel access procedure to a second sidelink transmission of the wireless terminal when the second sidelink transmission of the wireless terminal follows a first sidelink transmission of the other wireless terminal in a shared channel occupancy with the other wireless terminal, if the wireless terminal follows the particular type of sidelink channel access procedure, the wireless terminal does not sense the channel prior to the second sidelink transmission. Wireless terminal. (Appendix 43) The second sidelink transmission comprises a Physical Sidelink Shared Channel (PSSCH) transmission. 43. The wireless terminal of claim 42. (Appendix 44) the channel occupation is initiated by the other wireless terminal after the channel is sensed as idle by a channel access procedure involving Listen-Before-Talk (LBT) by the other wireless terminal; 44. The wireless terminal of claim 42 or 43. (Appendix 45) The specific type of sidelink channel access procedure is a Type 2C sidelink channel access procedure. 45. The wireless terminal according to any one of appendix 42 to 44. (Appendix 46) 1. A method performed by a wireless terminal, comprising: applying a specific type of sidelink channel access procedure to a second sidelink transmission of the wireless terminal when the second sidelink transmission of the wireless terminal follows a first sidelink transmission of the other wireless terminal in a shared channel occupancy; if the wireless terminal follows the particular type of sidelink channel access procedure, the wireless terminal does not sense the channel prior to the second sidelink transmission. method. This application claims priority based on Japanese Patent Application No. 2023-021047, filed on February 14, 2023, the disclosure of which is incorporated herein in its entirety. 1A, 1B UE 2. RAN Node 21 Cell 1303 Baseband Processor 1304 application processor 1306 Memory 1307 Modules 1404 processor 1405 Memory 1406 Modules

Claims

1. Consistent sidelink Listen-Before-Talk (LBT) failure detection; the means is configured to consider channel access failures for sidelink transmissions of a first type for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type for the consistent sidelink LBT failure detection. Wireless terminal.

2. the first type of sidelink transmission and the second type of sidelink transmission differ from each other in physical channels or physical signals used for transmission. The wireless terminal of claim 1 .

3. the first type of sidelink transmission includes at least a Physical Sidelink Shared Channel (PSSCH) transmission; the second type of sidelink transmission includes at least one or both of a Sidelink Synchronization Signal (S-SS) / Physical Sidelink Broadcast Channel (PSBCH) block (S-SSB) transmission and a Physical Sidelink Feedback Channel (PSFCH) transmission; 3. The wireless terminal according to claim 1 or 2.

4. the means is configured to provide a Physical (PHY) layer and a Medium Access Control (MAC) layer; the PHY layer is adapted to send a failure indication to the MAC layer for each channel access failure for the first type of sidelink transmission; the PHY layer is adapted to not inform the MAC layer of a channel access failure for the second type of sidelink transmission; the MAC layer is adapted to detect one or more consistent LBT failures based on receiving a failure indication from the PHY layer; 3. The wireless terminal according to claim 1 or 2.

5. the means is configured to provide a Physical (PHY) layer and a Medium Access Control (MAC) layer; the PHY layer is adapted to send a failure indication to the MAC layer for each channel access failure; the MAC layer is adapted to take into account a failure indication received from the PHY layer for the first type of sidelink transmission for the consistent sidelink LBT failure detection; the MAC layer is adapted to ignore a failure indication for the second type of sidelink transmission in the consistent sidelink LBT failure detection.

3. The wireless terminal according to claim 1 or 2.

6. the PHY layer is adapted to indicate, upon each failure indication, the type of intended sidelink transmission.

6. The wireless terminal according to claim 5.

7. means for transmitting configuration information for consistent sidelink Listen-Before-Talk (LBT) failure detection to a wireless terminal; the configuration information causes the wireless terminal to consider channel access failures for sidelink transmissions of a first type for the consistent sidelink LBT failure detection and to ignore channel access failures for sidelink transmissions of a second type in the consistent sidelink LBT failure detection. Radio Access Network (RAN) node.

8. Considering channel access failures for a first type of sidelink transmission for consistent sidelink Listen-Before-Talk (LBT) failure detection; and and ignoring channel access failures for a second type of sidelink transmission in the consistent sidelink LBT failure detection. A method performed by a wireless terminal comprising:

9. A program for causing a computer to perform a method for a wireless terminal, comprising: The method comprises: Considering channel access failures for a first type of sidelink transmission for consistent sidelink Listen-Before-Talk (LBT) failure detection; and and ignoring channel access failures for a second type of sidelink transmission in the consistent sidelink LBT failure detection. A program that includes:

10. Consistent sidelink Listen-Before-Talk (LBT) failure detection; the means is configured to take into account channel access failures detected in a sidelink channel access procedure of a first type in the consistent sidelink LBT failure detection, and to ignore channel access failures detected in a sidelink channel access procedure of a second type in the consistent sidelink LBT failure detection. Wireless terminal.