Consistent Listen-Before-Talk Failure Recovery Procedure for Sidelink Operation in Unlicensed Bands

Abstract

Systems, methods, devices, and computer program products are provided for detecting consistent listen-before-talk failure cases and successfully recovering from such failure cases in a sidelink implementation for unlicensed bands. For example, the method may include monitoring a transmission resource pool in which the device is operating. The transmission resource pool may include resource block sets, and each resource block set may be monitored. The monitoring may apply to resource block sets for which a prohibition timer is not running or has expired. The monitoring may be performed to detect listen-before-talk failures of the device for each monitored resource block set of the plurality of resource block sets. The method may also include triggering or declaring a consistent listen-before-talk failure for the monitored resource block set when a count value of the detected failures exceeds a threshold.

Description

[Technical Field]

[0001] Some exemplary embodiments relate generally to communications involving mobile or wireless communication systems, such as Long Term Evolution (LTE) or fifth generation (5G) radio access technologies or new radio (NR) access technologies, or other communication systems including subsequent generations of the same or similar standards. For example, certain exemplary embodiments relate generally to consistent listen-before-talk failure case detection and successful recovery from such failure cases in sidelink implementations for unlicensed bands. [Background technology]

[0002] Examples of mobile communication systems or wireless communication systems include the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), LTE-Advanced (LTE-A), MultiFire, LTE-A Pro, and / or fifth-generation (5G) radio access technology or New Radio (NR) access technology. 5G radio systems refer to the next generation (NG) of radio systems and network architectures. 5G systems are primarily built on 5G New Radio (NR), but 5G (or NG) networks can also be built on E-UTRA radio. Since Release 18 (Rel-18), 5G has been referred to as 5G Advanced. NR is estimated to provide bit rates of 10–20 Gbit / s or more and support service categories such as enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine-based communications (mMTC). NR is expected to provide extremely high bandwidth, ultra-robust low-latency connectivity, and large-scale networking to support the Internet of Things (IoT). With the proliferation of IoT and machine-to-machine (M2M) communications, there will be a growing need for networks that meet the needs of low power consumption, low data rates, and long battery life. The term "Next Generation Radio Access Network" (NG-RAN) refers to the RAN for 5G and can provide both NR and LTE (and LTE Advanced) radio access. Note that in 5G, nodes that can provide radio access functionality to user equipment (i.e., similar to the Node B (NB) in UTRAN or the evolved NB (eNB) in LTE) may be named "Next Generation NB" (gNB) if they are built with NR radios, or "Next Generation eNB" (NG-eNB) if they are built with E-UTRA radios. 6G is currently under development and may replace 5G and 5G Advanced. Summary of the Invention

[0003] An embodiment may be directed to an apparatus. The apparatus may include at least one processor and at least a memory that stores instructions. When executed by the at least one processor, the instructions may cause the apparatus to at least monitor a transmission resource pool in which the apparatus is operating. The transmission resource pool may include a plurality of resource block sets. The monitoring may be performed for each resource block set of the plurality of resource block sets for which a prohibition timer is not running or has expired. The monitoring is executed to detect a listen-before-talk failure of the apparatus for each monitored resource block set of the plurality of resource block sets of the resource pool. When executed by the at least one processor, the instructions may also cause at least the apparatus to detect a listen-before-talk failure of the apparatus for a monitored resource block set of the plurality of resource block sets. When executed by the at least one processor, the instructions may further cause the apparatus to at least increment a failure counter to a count value. When executed by the at least one processor, the instructions may further cause at least the apparatus to start or restart a failure detection timer associated with the failure counter. The instructions, when executed by the at least one processor, may also cause the device to at least trigger or declare a consistent listen-before-talk failure for the monitored resource block set if the count value exceeds a threshold. The instructions, when executed by the at least one processor, may also cause the device to at least control communications of the device based on the consistent listen-before-talk failure being triggered or declared.

[0004] Embodiments are directed to a method. The method may include monitoring a transmission resource pool in which a user equipment is operating. The transmission resource pool may have multiple resource block sets. The monitoring may be performed for each resource block set of the multiple resource block sets for which a prohibition timer is not running or has expired. The monitoring may be performed to detect a listen-before-talk failure of the user equipment for each monitored resource block set of the multiple resource block sets of the resource pool. The method may also include detecting a listen-before-talk failure of the user equipment for the monitored resource block set of the multiple resource block sets. The method may further include incrementing a failure counter to a count value. The method may further include starting or restarting a failure detection timer associated with the failure counter. The method may also include triggering or declaring a consistent listen-before-talk failure for the monitored resource block set when the count value exceeds a threshold. The method may further include controlling communication of the user equipment based on the consistent listen-before-talk failure being triggered or declared.

[0005] An embodiment is directed to an apparatus. The apparatus may include means for monitoring a transmission resource pool in which the apparatus operates. The transmission resource pool may have multiple resource block sets. The monitoring may be performed for each resource block set of the multiple resource block sets for which a prohibition timer is not running or has expired. The monitoring may be performed to detect a listen-before-talk failure of the apparatus for each monitored resource block set of the multiple resource block sets of the resource pool. The apparatus may also include means for detecting a listen-before-talk failure of the apparatus for a monitored resource block set of the multiple resource block sets. The apparatus may further include means for incrementing a failure counter to a count value and means for starting or restarting a failure detection timer associated with the failure counter. The apparatus may further include means for triggering or declaring a consistent listen-before-talk failure for the monitored resource block set when the count value exceeds a threshold. The apparatus may also include means for controlling communication of the apparatus based on the consistent listen-before-talk failure being triggered or declared. [Brief explanation of the drawings]

[0006] For a proper understanding of the exemplary embodiments, reference should be made to the accompanying drawings. [Figure 1] FIG. 1 shows a flow chart of the method in the detection stage according to a particular embodiment. [Figure 2] FIG. 2 shows a flowchart of the method in the recovery phase according to a particular embodiment. [Figure 3] FIG. 3 illustrates an exemplary block diagram of a system in one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] It will be readily understood that the components of an example embodiment, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of several example embodiments of systems, methods, apparatuses, and computer program products for providing consistent listen-before-talk failure case detection and suitable recovery from such failure cases in sidelink implementations for unlicensed bands is not intended to limit the scope of the particular embodiments, but is instead representative of selected example embodiments.

[0008] The features, structures, or characteristics of the exemplary embodiments described throughout this specification may be combined in any suitable manner in one or more exemplary embodiments. For example, throughout this specification, the use of the phrase "particular embodiment," "some embodiments," or other similar phrases refers to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment. Thus, the appearances of "particular embodiment," "some embodiments," "other embodiments," or other similar phrases throughout this specification do not necessarily all refer to the same embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more exemplary embodiments.

[0009] Particular embodiments may have various aspects and features, which may be applied alone or in any desired combination with one another, and other features, procedures, and elements may also be applied in combination with some or all of the aspects and features disclosed herein.

[0010] Moreover, if desired, different functions or procedures described below can be performed in different orders and / or concurrently with one another. Moreover, if desired, one or more of the described functions or procedures can be optional or combined. As such, the following description should be considered illustrative of the principles and teachings of particular exemplary embodiments, and not in limitation thereof.

[0011] Certain embodiments relate to enhancements to the sidelink (SL), of which the sidelink in unlicensed bands (SL-U) is a part. The channel access mechanisms of New Radio (NR) (NR-U) in unlicensed bands can be reused for sidelink unlicensed operation. Although the physical channel design framework may differ, the channel structures of the NR sidelink and NR-U can be considered as baseline structures.

[0012] It may be valuable for the SL-U Medium Access Control (MAC) to support SL-specific consistent Listen-Before-Talk (LBT) failure detection and recovery procedures. The resource granularity at which SL-specific LBT failures can be considered detected could be, for example, per Resource Pool (RP), per Resource Block (RB) set, per SL Bandwidth Part (BWP), or some other resource granularity. Whatever resource granularity a consistent LBT failure is declared at, it is beneficial to have a procedure to follow to recover from the declared LBT failure.

[0013] It can be valuable to support both consistent LBT failure detection and recovery procedures. With regard to consistent LBT failure detection, a high-level description of the detection procedure could involve the use of timers and counters, but the granularity of this detection procedure can benefit from appropriate selection. For example, the detection procedure could be applied at the SL BWP, RB set, RP, or subchannel. The scope of the recovery procedure can depend heavily on the granularity of the detection procedure.

[0014] If the granularity is at the SL BWP level along the NR-U consistent LBT detection granularity, the recovery procedure may result in the SL device transitioning to another SL BWP. However, the SL-U may only support one SL BWP on the SL-U carrier. Therefore, the only outcome of the recovery procedure in this case is a switch to another SL carrier, unlicensed or licensed. Multi-carrier support has not yet been introduced into the NR SL design. Furthermore, LBT failures across different RB sets in the BWP may trigger consistent LBT failure detection even if the LBT failure rate is not high from any of these RB sets.

[0015] When the granularity is at the RP level, the outcome of the recovery procedure is to migrate SL devices to other RPs. A resource pool can contain multiple RB sets. Therefore, LBT failures across different RB sets of an RP may trigger consistent LBT failure detection even if the LBT failure rate is not high from any of these RB sets.

[0016] Finally, if the granularity is at the RB set level, e.g., the LBT bandwidth level, the outcome of the recovery procedure may be that the SL device migrates to another RB set, which, among all granularities, may be closest to the LBT procedure applied at the RB set level.

[0017] From an NR SL Mode 1 resource allocation perspective, where a next generation Node B (gNB) provides resource allocation, a switch to another RB set that is not currently experiencing consistent LBT failures may be triggered when the serving gNB receives a consistent LBT failure indication. However, from an NR SL Mode 2 resource allocation perspective, where each SL UE performs its own resource allocation, a method for efficiently and effectively switching to another RB set may be required.

[0018] Certain embodiments provide an enhancement to NR SL Mode 2 resource allocation that may enable SL-U UEs to recover from consistent LBT failures. More specifically, certain embodiments address consistent LBT failure detection and recovery procedures for SL-U devices operating in NR SL Mode 2, assuming that the granularity of consistent LBT failure detection is at the RB set level.

[0019]

[0013] Figure 1 shows a flowchart of a method according to a particular embodiment. The method of Figure 1 focuses on the detection phase of the method. In contrast, Figure 2 focuses on the recovery phase of the method. Thus, the methods of Figure 1 and Figure 2 can be used together.

[0020] In the detection phase, the transmission resource pool (RP) in which the SL device is operating may be included in N RB sets. The detection procedure in FIG. 1 illustrates the procedure using RB x as an example of the N RBs to be monitored. In this phase, consistent LBT failure detection may be performed for each RB set. Initially, monitoring may be performed 110 if no consistent LBT failures have been detected in the past for a period of time. For example, for an RB set, the associated sl-LBT-RBsetUse prohibit timer may not be running or may have expired. This timer is known as a prohibit timer. A prohibit timer may be associated with an instruction not to use the resource block set associated with the timer as long as the timer is running.

[0021] The SL device may monitor LBT failures for each of the N RB sets of the RP. For example, each time an LBT procedure is attempted and the procedure is not successfully completed for transmission on selected resources in the RB sets, regardless of whether the physical layer (PHY) is Type 1 or Type 2, the medium access control (MAC) layer may receive an indication at 115 that an LBT failure has occurred in the corresponding RB sets.

[0022] A failure of an LBT procedure in the context of SL may refer to the inability of an SL UE to acquire a channel, for example, if the SL UE fails to complete the LBT procedure before the last allowed transmission start position associated with the selected resource.

[0023] Upon receiving an LBT failure indication from the PHY associated with a particular RB set, at 120 the MAC layer may increment an associated SL-specific LBT failure indication counter, such as SL_LBT_COUNTER, for that RB set(s) and may start or restart an SL-specific LBT failure detection timer, such as sl-LBT-FailureDetectionTimer.

[0024] The failure detection timer can be counted only at the RB set level or at the resource pool and RB set level. If at least two resource pools are multiplexed in time, both resource pools and RB sets can be considered. In contrast, if resource pools are only multiplexed in frequency, counting only at the RB set level may be sufficient.

[0025] Furthermore, by using counters at the resource pool and RB set level, it is possible to avoid triggering a consistent LBT failure in one resource pool based on experiencing consistent LBT failures in other time-multiplexed resource pools, which may be beneficial to address cases where the cause of the LBT failure originates from intra-RAT interactions and is therefore specifically observed at the resource pool and RB set level.

[0026] When the LBT continuity timer, eg, sl-LBT-FailureDetectionTimer, expires, the MAC layer can reset the counter and the LBT detection timer at 130, and the device can continue monitoring.

[0027] For each N RB set being monitored, a determination can be made at 135 whether the associated SL-specific LBT failure indication counter value is equal to or greater than an SL-specific maximum LBT failure instance count threshold (e.g., sl-LBT-FailureInstanceMaxCount). If not, monitoring can continue. If the threshold is exceeded, a consistent LBT failure can be triggered or declared by the MAC entity associated with that RB set, per 140.

[0028] At 145, the MAC entity may start the sl-LBT-RBsetUseProhibitTimer associated with the RB set for which a consistent LBT failure has been declared. The system may check at 150 whether the prohibit timer has expired. If the timer has not expired, the resource block set remains prohibited and the prohibit timer may continue counting. Additionally, the sl-LBT-FailureDetectionTimer may be stopped and the counter reset. The prohibit timer may ensure that the MAC entity knows when it can again allow selection of resources in the RB set for which a consistent LBT failure has been declared.

[0029] For each N RB set being monitored, the device may check 135 whether an SL-specific LBT failure detection timer, e.g., sl-LBT-FailureDetectionTimer, has expired and whether an SL-specific LBT failure indication counter, e.g., SL_LBT_COUNTER, is below a maximum LBT failure instance count threshold, sl-LBT-FailureInstanceMaxCount. If so, the SL-specific LBT failure indication counter, SL_LBT_COUNTER, may be reset to 0.

[0030] For each set of N monitored RBs, if the maximum LBT failure instance count threshold, e.g., sl-LBT-FailureInstanceMaxCount, and / or the SL-specific LBT failure detection timer, e.g., sl-LBT-FailureDetectionTimer, is reset, the SL-specific LBT failure indication counter, e.g., SL_LBT_COUNTER, may be reset to 0.

[0031] In an exemplary embodiment, if the maximum LBT failure instance count threshold, e.g., sl-LBT-FailureInstanceMaxCount, is reset to a value higher than the current SL-specific LBT failure indication counter value, the SL-specific LBT failure indication counter, e.g., SL_LBT_COUNTER, may be maintained rather than reset to 0, and the newly set threshold may be applied to declare a consistent LBT failure. Otherwise, if the current counter is higher than the newly set threshold, the counter should be reset to 0 or a consistent LBT failure should be declared.

[0032] Similarly, if the SL-specific LBT failure detection timer, e.g., sl-LBT-FailureDetectionTimer, is reset and the elapsed time since the detection timer was started does not exceed the newly set detection timer, the SL-specific LBT failure indication counter, e.g., SL_LBT_COUNTER, may be maintained rather than reset to 0, and the detection timer may be extended / shortened by a delta equal to the difference between the previous detection timer and the newly set detection timer. Otherwise, if the elapsed time is greater than the newly set detection timer, the counter should be reset to 0 or a consistent LBT failure should be declared.

[0033] The above options apply if both parameters are reset at the same time.

[0034] If a consistent LBT failure indication has not been triggered by the MAC entity for any of the N RB sets(s) from the transmission resource pool, and if all timers associated with the RB sets for which a consistent LBT failure was previously declared (e.g., sl-LBT-RBsetUseProhibitTimer) have expired, the method may return to step 110.

[0035] In a particular embodiment, the MAC entity can measure the activity of an RB set for which a consistent LBT failure has been declared and, based on a determination of low activity, such as a continuous bit rate (CBR) below a threshold for the RB set, request the PHY to trigger an early termination of the sl-LBT-RBsetUseProhibitTimer timer. In a particular embodiment, based on a determination of high activity, such as a CBR above a threshold in the RB set, the sl-LBTRBsetUseProhibitTimer can be extended. These options can be used individually or in combination.

[0036] In certain embodiments, there may be no timer and the only condition for declaring the RB set available again may be the detection of low activity, e.g., the system may wait for the CBR to fall below a threshold in the RB set to declare the RB set available again.

[0037] 2 shows a flowchart of a method in a recovery phase according to a particular embodiment. As shown in FIG. 2, a recovery procedure may be triggered at 210 for all transmit (Tx) operations associated with RB x. If a consistent LBT failure is triggered by the MAC entity in at least one of the N RB sets(s) and the associated timer, e.g., sl-LBT-RBsetUseProhibitTimer, has not expired, further operations may be performed.

[0038] If the N RB sets(s) are the only RB sets indicated to have recently experienced an LBT failure, or if consistent LBT failures have been declared for all RB sets in the transmitting RP, then on the "No" branch from 220, the system may transition to another transmitting RP that includes at least one RB set that is not part of the RB set for which consistent LBT failures have been declared. If an alternative transmitting RP is not available, the system may switch to another SL carrier by triggering a report to higher layers and / or notifying the gNB that an RP switch is required. As another option, the system may trigger an indication to other frequencies of interest, for example, using the parameter sl-RxInterestedFreqList from SidelinkUEinformationNR, which may be selected from a list of frequencies sl-FreqInfoList broadcast on SIB12.

[0039] However, if N>1 and there is at least one remaining RB set of the transmitting RP for which a consistent LBT failure has not been declared, i.e., a "yes" branch from 220, for a future SL transmission for which a resource has already been selected and this resource is part of the RB set for which a consistent LBT failure has been declared, the system may trigger resource reselection at 240, e.g., toward another RB set for which a consistent LBT failure has not been declared and for which the associated sl-LBT-RBsetUseProhibitTimer has not run. This resource reselection may only be triggered for resources that satisfy one or more of the following: the resource is within a predetermined operation period according to the sl-LBT-RBsetUseProhibitTimer; resource reservation is indicated, e.g., via the "Resource Reservation Period" field in the first-stage sidelink control information (SCI) for a semi-persistent transmission or for a previous transmission; resource reservation has not yet been indicated by the first-stage SCI; or resource reservation is indicated by the first-stage SCI using the time resource allocation field.

[0040] At 250, for future SL transmissions for which no resources have been selected, e.g., if the MAC has not yet requested the PHY to initiate a resource selection procedure, the MAC may indicate to the PHY the fields prio_TX, remaining PDB, L_“subCH”, and / or P_“rsvp_TX” in connection with the resource selection to indicate the RB set for which resources are to be selected or the RB set to be excluded from the resource selection.

[0041] In a particular embodiment, when the prohibition timer expires, the MAC may indicate the excluded RB set along with the remaining time of the prohibition timer, and the PHY may also consider such RB set for resource selection after the prohibition timer expires.

[0042] For future SL transmissions for which a resource selection procedure is already in progress, upon receiving a candidate resource set from the PHY at 260, the MAC may exclude from the received set all resources that belong to the RB set for which a consistent LBT failure has been declared. Also, if the MAC has not received a candidate resource set from the PHY, the MAC may indicate to the PHY an RB set from which to select resources or an RB set to exclude from resource selection.

[0043] In certain embodiments, only traffic associated with a configured traffic priority, e.g., traffic with a low PC5 quality indicator (PQI) value or a low L1 priority, may trigger a consistent LBT failure indication and be prevented from being transmitted on RB set(s) whose associated timers, such as sl-LBT-RBsetUseProhibitTimer, have not expired.

[0044] 3 illustrates an example of a system including device 10, according to an exemplary embodiment. In an embodiment, device 10 is a node, host, or server in a communications network or provides a service to such a network. For example, device 10 may be a network node, satellite, base station, Node B, evolved Node B (eNB), 5G Node B or access point, next generation Node B (NG-NB or gNB), TRP, HAPS, integrated access and backhaul (IAB) node, and / or WLAN access point associated with a radio access network, such as an LTE network, 5G, or NR. In some exemplary embodiments, device 10 may be, for example, a gNB or other similar wireless node.

[0045] In some exemplary embodiments, apparatus 10 includes an edge cloud server as a distributed computing system. It should be understood that the server and wireless node may be standalone devices that communicate with each other via wireless paths or via wired connections, or may be located in the same entity that communicates via wired connections. For example, in a particular exemplary embodiment in which apparatus 10 represents a gNB, it may include a central unit (CU) and distributed unit (DU) architecture that divides the functions of the gNB. In such an architecture, the CU may be a logical node that includes gNB functions such as user data forwarding, mobility control, radio access network sharing, positioning, and / or session management. The CU may control the operation of DU(s) via a midhaul interface, referred to as the F1 interface, and the DU(s) may have one or more radio units (RUs) connected to the DU(s) via a fronthaul interface. The DU may be a logical node that includes a subset of gNB functions, depending on the functional division option. Note that those skilled in the art will understand that apparatus 10 may include components or functions not shown in FIG. 3 .

[0046] As in the example of FIG. 3, device 10 may include processor 12 for processing information and executing instructions or operations. Processor 12 may be any type of general-purpose or special-purpose processor. Indeed, processor 12 may include, for example, one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a processor based on a multi-core processor architecture, or any other processing means. While a single processor 12 is shown in FIG. 3, multiple processors may be utilized according to other embodiments. For example, it should be understood that in exemplary embodiments, device 10 may include two or more processors that may form a multiprocessor system that may support multiprocessing (e.g., processor 12 in this example may represent a multiprocessor). In particular embodiments, the multiprocessor system may be tightly coupled (e.g., to form a computer cluster) or loosely coupled.

[0047] The processor 12 may perform functions related to the operation of the device 10, including, for example, precoding of antenna gain / phase parameters, encoding and decoding of individual bits forming communication messages, formatting of information, and overall control of the device 10, including processes related to the detection of consistent listen-before-talk failure cases and suitable recovery from such failure cases in sidelink implementations for unlicensed bands.

[0048] Apparatus 10 may further include or be connected to processor 12 with memory 14 (internal or external) for storing information and instructions that may be executed by processor 12. Memory 14 may be one or more memories and may be of any type suitable for the local application environment and may be implemented using any suitable volatile or non-volatile data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and / or removable memory. For example, memory 14 may include random access memory (RAM), read-only memory (ROM), static storage devices such as magnetic or optical disks, hard disk drives (HDDs), or any other type of non-transitory machine- or computer-readable medium, or any combination of other suitable storage means. The instructions stored in memory 14 may include program instructions or computer program code that, when executed by processor 12, enable apparatus 10 to perform tasks as described herein.

[0049] In embodiments, device 10 may further include or be connected (internal or external) to a drive or port configured to accept and read an external computer-readable storage medium, such as an optical disk, a USB drive, a flash drive, or any other storage medium. For example, the external computer-readable storage medium may store a computer program or software for execution by processor 12 and / or device 10.

[0050] In some embodiments, device 10 may also include or be connected to one or more antennas 15 for transmitting and receiving signals and / or data to and from device 10. Device 10 may further include or be connected to a transceiver 18 configured to transmit and receive information. Transceiver 18 may include, for example, multiple wireless interfaces that may be connected to antenna(s) 15 or may comprise any other suitable transceiver means. The wireless interfaces may support multiple wireless access technologies, including one or more of Global System for Mobile Communications (GSM), Narrowband Internet of Things (NB-IoT), LTE, 5G, WLAN, Bluetooth (BT), Bluetooth Low Energy (BT-LE), Near Field Communication (NFC), Radio Frequency Identification (RFID), Ultra-Wideband (UWB), MulteFire, etc. The air interface may include components such as filters, converters (e.g., digital-to-analog converters), mappers, and Fast Fourier Transform (FFT) modules to generate symbols for transmission over one or more downlinks and receive symbols (e.g., over an uplink).

[0051] Thus, transceiver 18 may be configured to modulate information onto a carrier waveform for transmission by antenna 15, and to demodulate information received via antenna 15 for further processing by other elements of device 10. In other embodiments, transceiver 18 may transmit and receive signals or data directly. Additionally or alternatively, in some embodiments, device 10 may include input and / or output devices (I / O devices), or input / output means.

[0052] In this embodiment, memory 14 may store software modules that provide functionality when executed by processor 12. The modules may include, for example, an operating system that provides operating system functionality for device 10. The memory may also store one or more functional modules, such as applications or programs, for providing additional functionality to device 10. Components of device 10 may be implemented in hardware or any suitable combination of hardware and software.

[0053] According to some embodiments, the processor 12 and memory 14 may be included in or form part of a processing circuit / means or a control circuit / means. Further, in some embodiments, the transceiver 18 may be included in or form part of a transceiver circuit / means.

[0054] As used herein, the term “circuitry” may refer to a hardware-only circuit implementation (e.g., analog and / or digital circuitry), a combination of hardware circuitry and software, a combination of analog and / or digital hardware circuitry and software / firmware, any portion of a hardware processor(s) having software (including digital signal processors) that cooperate to cause a device (e.g., device 10) to perform various functions, and / or a hardware circuit(s) and / or processor(s), or portions thereof, that uses software for operation but may not be present if not necessary for operation. As a further example, the term “circuitry” in this embodiment may also cover simply a hardware circuit or processor (or processors), or a portion of a hardware circuit or processor, and its associated software and / or firmware implementation. The term circuitry may also cover, for example, a baseband integrated circuit in a server, a cellular network node or device, or other computing or network device.

[0055] As introduced above, in certain embodiments, apparatus 10 may be part of a network element or RAN node, such as a base station, access point, Node B, eNB, gNB, TRP, HAPS, IAB node, relay node, WLAN access point, satellite, etc. In an exemplary embodiment, apparatus 10 may be a gNB or other radio node, or may be a CU and / or DU of a gNB. According to certain embodiments, apparatus 10 is controlled by memory 14 and processor 12 and may perform functions associated with any of the embodiments described herein. For example, in exemplary embodiments, apparatus 10 may be configured to perform one or more of the processes depicted in any of the flowcharts or signaling diagrams described herein, such as those shown in FIGS. 1 and 2. In some embodiments, apparatus 10 may be configured to perform procedures associated with detecting consistent listen-before-talk failure cases and providing suitable recovery from such failure cases, e.g., in sidelink implementations for unlicensed bands.

[0056] 3 further illustrates an example of apparatus 20 in an exemplary embodiment. In one embodiment, apparatus 20 is a node or element in a communication network or associated with such a network, such as a UE, communication node, mobile equipment (ME), mobile station, mobile device, fixed device, IoT device, or other device. As described in this example, a UE may alternatively be, for example, a mobile station, mobile device, mobile unit, mobile equipment, user equipment, subscriber station, wireless terminal, tablet, smartphone, IoT device, sensor or NB-IoT device, watch or other wearable, head-mounted display (HMD), vehicle, drone, medical equipment and its applications (e.g., remote surgery), industrial equipment and its applications, industrial devices and its applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated processing chains), consumer electronics device, device operating in a commercial and / or industrial wireless network, etc. By way of example, apparatus 20 may be implemented in, for example, a wireless handheld device, a wireless plug-in accessory, etc.

[0057] In some exemplary embodiments, device 20 may include one or more processors, one or more computer-readable storage media (e.g., memory, storage, etc.), one or more wireless access components (e.g., modems, transceivers, etc.), and / or a user interface. In some embodiments, device 20 may be configured to operate using one or more wireless access technologies, such as GSM, LTE, LTE-A, NR, 5G, WLAN, WiFi, NB-IoT, Bluetooth, NFC, MulteFire, and / or any other wireless access technology. Note that one skilled in the art will understand that device 20 may include components or features not shown in FIG. 3 .

[0058] As in the example of FIG. 3 , device 20 may include or be connected to processor 22 for processing information and executing instructions or operations. Processor 22 may be any type of general-purpose or special-purpose processor. Indeed, processor 22 may include, by way of example, one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), and a processor based on a multi-core processor architecture. While a single processor 22 is shown in FIG. 3 , multiple processors may be utilized according to other embodiments. For example, it should be understood that in exemplary embodiments, device 20 may include two or more processors that may form a multiprocessor system that may support multiprocessing (e.g., processor 22 in this example may represent a multiprocessor). In particular embodiments, the multiprocessor system may be tightly coupled (e.g., to form a computer cluster) or loosely coupled.

[0059] The processor 22 may perform functions related to the operation of the device 20, including, as some examples, precoding of antenna gain / phase parameters, encoding and decoding of individual bits forming communication messages, formatting of information, and overall control of the device 20, including processes related to management of communication resources.

[0060] Apparatus 20 may further include or be connected to memory 24 (internal or external) that may be connected to processor 22 for storing information and instructions that may be executed by processor 22. Memory 24 may be one or more memories and may be of any type suitable for the local application environment and may be implemented using any suitable volatile or non-volatile data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and / or removable memory. For example, memory 24 may include any combination of random access memory (RAM), read-only memory (ROM), static storage devices such as magnetic or optical disks, hard disk drives (HDDs), or any other type of non-transitory machine- or computer-readable medium. The instructions stored in memory 24 may include program instructions or computer program code that, when executed by processor 22, enable apparatus 20 to perform the tasks described herein.

[0061] In embodiments, device 20 may further include or be connected (internal or external) to a drive or port configured to accept and read an external computer-readable storage medium, such as an optical disk, a USB drive, a flash drive, or any other storage medium. For example, the external computer-readable storage medium may store a computer program or software for execution by processor 22 and / or device 20.

[0062] In some embodiments, device 20 may also include or be connected to one or more antennas 25 for receiving downlink signals and for transmitting from device 20 via an uplink. Device 20 may further include a transceiver 28 configured to transmit and receive information. Transceiver 28 may also include a wireless interface (e.g., a modem) connected to antenna 25. The wireless interface may support multiple wireless access technologies, including one or more of GSM, LTE, LTE-A, 5G, NR, WLAN, NB-IoT, Bluetooth, BT-LE, NFC, RFID, UWB, etc. The wireless interface may include other components, such as filters, converters (e.g., digital-to-analog converters, etc.), symbol demappers, signal shaping components, inverse fast Fourier transform (IFFT) modules, etc., to process symbols, such as OFDM symbols, carried by the downlink or uplink.

[0063] For example, transceiver 28 may be configured to modulate information onto a carrier waveform for transmission by antenna(s) 25 and demodulate information received via antenna(s) 25 for further processing by other elements of device 20. In other embodiments, transceiver 28 may transmit and receive signals or data directly. Additionally or alternatively, in some embodiments, device 20 may include input and / or output devices (I / O devices). In particular embodiments, device 20 may further include a user interface, such as a graphical user interface or a touch screen.

[0064] In an embodiment, memory 24 stores software modules that provide functionality when executed by processor 22. The modules may include, for example, an operating system that provides operating system functionality for device 20. The memory may also store one or more functional modules, such as applications or programs, for providing additional functionality to device 20. Components of device 20 may be implemented as hardware or any suitable combination of hardware and software. According to an exemplary embodiment, device 20 may be configured to communicate with device 10 via a wireless or wired communication link 70, optionally according to any radio access technology, such as NR.

[0065] According to some embodiments, the processor 22 and memory 24 may be included in or form part of processing or control circuitry. Further, in some embodiments, the transceiver 28 may be included in or form part of transmitting and receiving circuitry.

[0066] As mentioned above, according to some embodiments, apparatus 20 may be, for example, a UE, a SL UE, a relay UE, a mobile device, a mobile station, a ME, an IoT device, and / or an NB-IoT device. According to particular embodiments, apparatus 20 may be controlled by memory 24 and processor 22 to perform functions associated with any of the embodiments described herein, e.g., one or more of the operations illustrated in or described with respect to FIGS. 1 and 2, perform functions associated with FIGS. 1 and 2, or any other method described herein. For example, in an exemplary embodiment, apparatus 20 may be controlled to perform processes associated with detecting consistent listen-before-talk failure cases and providing suitable recovery from such failure cases in sidelink implementations for unlicensed bands, as described in detail elsewhere herein.

[0067] In some embodiments, an apparatus (e.g., apparatus 10 and / or apparatus 20) may comprise means for performing any of the methods, processes, or variations described herein. Examples of means may include one or more processors, memories, controllers, transmitters, receivers, and / or computer program code for performing any of the operations described herein.

[0068] In view of the foregoing, certain exemplary embodiments provide several technical improvements, enhancements, and / or preferably advantages over existing technical processes, constituting improvements at least in the field of radio network control and / or management. Particular embodiments may have various advantages and / or merits. For example, exemplary embodiments may provide an enhancement to NR SL Mode 2 resource allocation. This enhancement may enable SL-U UEs to recover from consistent LBT failures. More specifically, certain embodiments may address consistent LBT failure detection and recovery procedures for SL-U devices operating in NR SL Mode 2, even assuming that the granularity of consistent LBT failure detection is at the RB set level.

[0069] In some exemplary embodiments, the functions of any of the methods, processes, signaling diagrams, algorithms or flowcharts described herein may be implemented by software and / or computer program code or portions of code stored in a memory or other computer-readable or tangible medium and executed by a processor.

[0070] In some exemplary embodiments, an apparatus may include or be associated with at least one software application, module, unit, or entity configured as arithmetic operation(s) or as a program or part of a program (including additional or updated software routines) that can be executed by at least one computing processor or controller. A program, also referred to as a program product or computer program, includes software routines, applets, and macros, and may be stored on any device-readable data storage medium and include program instructions for performing specific tasks. A computer program product may include one or more computer-executable components configured to perform exemplary embodiments when the program is executed. One or more computer-executable components may be at least one software code or part of code. Modifications and configurations necessary to implement the functionality of exemplary embodiments may be implemented as a routine(s) or as additional or updated software routine(s). The software routines in one example are downloaded to the apparatus.

[0071] As an example, the software or computer program code or portions of code may be in source code form, object code form, or some intermediate form, and may be stored on some carrier, distribution medium, or computer-readable medium. Such carriers may include, for example, recording media, computer memory, read-only memory, optical, electrical, and / or electrical carrier signals, telecommunications signals, and / or software distribution packages. Depending on the processing power required, the computer program may be executed in a single electronic digital computer or may be distributed across multiple computers. The computer-readable medium or computer-readable storage medium may be a non-transitory medium. As used herein, the term "non-transitory" refers to the medium itself (i.e., tangible, not a signal), as opposed to the data storage persistence (e.g., RAM vs. ROM).

[0072] In other exemplary embodiments, the functionality of the exemplary embodiments may be performed by hardware or circuitry included in the device, for example, through the use of an application specific integrated circuit (ASIC), a programmable gate array (PGA), a field programmable gate array (FPGA), or any other combination of hardware and software. In still other exemplary embodiments, the functionality of the exemplary embodiments may be implemented as a signal by non-tangible means, such as transmitted by electromagnetic signals downloaded from the Internet or other networks.

[0073] According to exemplary embodiments, an apparatus such as a node, device, or corresponding component may be configured as a circuit, computer, or microprocessor such as a single-chip computer element, or as a chipset, which may include at least a memory to provide storage capacity used for computational processing(s), and / or a computational processor to perform computational processing.

[0074] The exemplary embodiments in this example may apply to both singular and plural embodiments, regardless of whether singular or plural language is used in connection with describing a particular embodiment. For example, an exemplary embodiment describing the operation of a single network node may also apply to an exemplary embodiment including multiple instances of the network node, and vice versa.

[0075] Those skilled in the art will readily appreciate that the exemplary embodiments, such as those described above, may be implemented using a different sequence of steps and / or hardware elements in different configurations than those disclosed. Thus, while several embodiments have been described based on these exemplary embodiments, it will be apparent to those skilled in the art that certain modifications, variations, and alternative configurations will be apparent while remaining within the spirit and scope of the exemplary embodiments.

[0076] Partial Glossary LBT Listen Before Talk SL Side Link SL-U SL on unlicensed bands RP Resource Pool RB Resource Block BWP Bandwidth Portion RRC Radio Resource Control NR new radio NR-U NR on unlicensed bands gNB Next Generation Node B MAC Media Access Control PHY physical layer CBR Continuous Bitrate

Claims

1. 1. An apparatus comprising: at least one processor; When executed by the at least one processor, the device includes at least: monitoring a transmission resource pool in which the device is operating, the transmission resource pool having a plurality of resource block sets, the monitoring being performed for each resource block set of the plurality of resource block sets for which a prohibition timer is not running or has expired, the monitoring being performed to detect listen-before-talk failures of the device for each monitored resource block set of the plurality of resource block sets of the resource pool; detecting a listen-before-talk failure of the device for a monitored resource block set of the plurality of resource block sets; incrementing a failure counter to a count value; starting or restarting a failure detection timer associated with said failure counter; triggering or declaring a consistent listen-before-talk failure for the monitored set of resource blocks when the count value exceeds a threshold; controlling communication of the device based on the consistent listen-before-talk failure being triggered or declared; at least one memory storing instructions for executing the An apparatus comprising:

2. The apparatus of claim 1 , wherein the failure counter is configured to count listen-before-talk failures at a resource block set level only or at a resource pool and resource block set level.

3. The instructions, when executed by the at least one processor, cause the device to perform at least: starting the prohibit timer for the monitored resource block based on the consistent listen-before-talk failure being triggered or declared; The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

4. The instructions, when executed by the at least one processor, cause the device to perform at least: detecting an activity level of the monitored resource blocks; triggering early termination of the inhibit timer based on the activity level being below a threshold; The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

5. The instructions, when executed by the at least one processor, cause the device to perform at least: detecting an activity level of the monitored resource blocks; extending the inhibit timer based on the activity level exceeding a threshold; The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

6. The instructions, when executed by the at least one processor, cause the device to perform at least: stopping the failure detection timer for the monitored resource block based on the consistent listen-before-talk failure being triggered or declared; resetting the failure counter for the monitored resource block based on the consistent listen-before-talk failure being triggered or declared; The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

7. The instructions, when executed by the at least one processor, cause the device to perform at least: determining that each of the plurality of resource block sets in the transmission resource pool has been triggered as a consistent listen-before-talk failure and that an associated timer for each resource block set has not expired; switching to a different transmission resource based on said determining; The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

8. 8. The apparatus of claim 7, wherein the different transmission resources comprise at least one of a further transmission resource pool including at least one resource block set different from the transmission resource pool, a sidelink carrier different from a sidelink carrier of the transmission resource pool, or a frequency of interest different from a frequency corresponding to the transmission resource pool.

9. The instructions, when executed by the at least one processor, cause the device to perform at least: determining that a first subset of the plurality of resource block sets in the transmission resource pool has been triggered as a consistent listen-before-talk failure and an associated timer of each resource block set of the first subset has not expired, while a second subset of the plurality of resource block sets that does not have a consistent listen-before-talk failure has been triggered or an associated timer of each resource block set of the second subset has expired; - selecting resources and triggering resource selection of a resource block set of the second subset instead of the first subset for sidelink transmissions for which the resources are part of the transmission resource pool; The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

10. The apparatus of claim 9 , wherein the trigger is conditioned on a resource being within an operating period of the prohibit timer associated with the resource.

11. 10. The apparatus of claim 9, wherein the trigger is conditional on resource reservation already being indicated via a resource reservation duration field of a first stage sidelink control information or a previous transmission.

12. The apparatus of claim 9 , wherein the trigger is conditional on resource reservation not already being indicated by first-stage sidelink control information.

13. The apparatus of claim 9 , wherein the trigger is conditioned on resource reservation being indicated by first stage sidelink control information using a temporal resource allocation field.

14. The instructions, when executed by the at least one processor, cause the device to perform at least: determining that a first subset of the plurality of resource block sets in the transmission resource pool are triggered as consistent listen-before-talk failures and that an associated timer of each resource block set in the first subset has not expired; - triggering resource selection of a resource block set for each resource block set of the first subset for sidelink transmissions for which no resources have been selected, according to an indication of the remaining time of the associated timer of said respective resource block set; The apparatus of claim 1 , wherein the apparatus causes the execution of the following:

15. 15. The apparatus of claim 14, wherein the selection is from an indicated inclusion set of resource block sets to select or the selection excludes an indicated exclusion set of resource block sets to exclude from selection.

16. 15. The apparatus of claim 14, wherein a medium access control entity of the apparatus, upon receiving a candidate resource set from a physical layer of the apparatus, excludes from the received candidate resource set all resources that belong to a resource block set for which a consistent listen-before-talk failure is declared and for which the prohibition timer is running.

17. 15. The apparatus of claim 14, wherein if a medium access control entity of the apparatus has not received a candidate resource set from a physical layer of the apparatus, the medium access control entity indicates to the physical layer an indicated inclusion set of resource block sets to select from, or the selection excludes an indicated exclusion set of resource block sets to exclude from selection.

18. 15. The apparatus of claim 14, wherein the triggered selection of a resource is inhibited solely based on the prohibit timer not having expired if a configured traffic priority is below a threshold level.

19. monitoring a transmission resource pool in which a user equipment is operating, the transmission resource pool having a plurality of resource block sets, the monitoring being performed for each resource block set of the plurality of resource block sets for which a prohibition timer is not running or has expired, the monitoring being performed for each monitored resource block set of the plurality of resource block sets of the resource pool to detect listen-before-talk failures of the user equipment; detecting a listen-before-talk failure of the user equipment for a monitored resource block set of the plurality of resource block sets; incrementing a failure counter to a count value; starting or restarting a failure detection timer associated with said failure counter; triggering or declaring a consistent listen-before-talk failure for the monitored set of resource blocks when the count value exceeds a threshold; controlling communications of the user equipment based on the consistent listen-before-talk failure being triggered or declared; A method comprising:

20. 20. The method of claim 19, wherein the failure counter is configured to count listen-before-talk failures at a resource block set level only or at a resource pool and resource block set level.

21. starting the prohibit timer for the monitored resource block based on the consistent listen-before-talk failure being triggered or declared; 20. The method of claim 19, further comprising:

22. detecting an activity level of the monitored resource blocks; triggering early termination of the inhibit timer based on the activity level being below a threshold; 20. The method of claim 19, further comprising:

23. detecting an activity level of the monitored resource blocks; extending the inhibit timer based on the activity level exceeding a threshold; 20. The method of claim 19, further comprising:

24. stopping the failure detection timer for the monitored resource block based on the consistent listen-before-talk failure being triggered or declared; resetting the failure counter based on the consistent listen-before-talk failure being triggered or declared; 20. The method of claim 19, further comprising:

25. determining that each of the plurality of resource block sets in the transmission resource pool has been triggered as a consistent listen-before-talk failure and that an associated timer for each resource block set has not expired; switching to a different transmission resource based on said determining; 20. The method of claim 19, further comprising:

26. 26. The method of claim 25, wherein the different transmission resources comprise at least one of a further transmission resource pool including at least one resource block set different from the transmission resource pool, a sidelink carrier different from a sidelink carrier of the transmission resource pool, or a frequency of interest different from a frequency corresponding to the transmission resource pool.

27. determining that a first subset of the plurality of resource block sets in the transmission resource pool has been triggered as a consistent listen-before-talk failure and an associated timer of each resource block set of the first subset has not expired, while a second subset of the plurality of resource block sets that does not have a consistent listen-before-talk failure has been triggered or an associated timer of each resource block set of the second subset has expired; - selecting resources and triggering resource selection of a resource block set of the second subset instead of the first subset for sidelink transmissions for which the resources are part of the transmission resource pool; 20. The method of claim 19, further comprising:

28. 28. The method of claim 27, wherein the trigger is conditioned on a resource being within an operating period of the prohibit timer associated with the resource.

29. 28. The method of claim 27, wherein the trigger is conditional on resource reservation already being indicated via a resource reservation duration field of a first stage sidelink control information or a previous transmission.

30. 28. The method of claim 27, wherein the trigger is conditional on resource reservation not already being indicated by first stage sidelink control information.

31. 28. The method of claim 27, wherein the trigger is conditional on resource reservation being indicated by first stage sidelink control information using a time resource allocation field.

32. determining that a first subset of the plurality of resource block sets in the transmission resource pool are triggered as consistent listen-before-talk failures and that an associated timer of each resource block set in the first subset has not expired; - triggering resource selection of a resource block set for each resource block set of the first subset for sidelink transmissions for which no resources have been selected, according to an indication of the remaining time of the associated timer of said respective resource block set; 20. The method of claim 19, further comprising:

33. 33. The method of claim 32, wherein the selection is from an indicated inclusion set of resource block sets to select or the selection excludes an indicated exclusion set of resource block sets to exclude from selection.

34. 33. The method of claim 32, wherein the medium access control entity of the user equipment, upon receiving a candidate resource set from the physical layer of the user equipment, excludes from the received candidate resource set all resources that belong to a resource block set for which a consistent listen-before-talk failure is declared and for which the prohibit timer is running.

35. 33. The method of claim 32, wherein if a medium access control entity of the user equipment has not received a candidate resource set from a physical layer of the user equipment, the medium access control entity indicates to the physical layer an indicated inclusion set of resource block sets to select from, or the selection excludes an indicated exclusion set of resource block sets to exclude from selection.

36. 33. The method of claim 32, wherein the triggered selection of a resource is inhibited solely based on the prohibit timer not having expired if a configured traffic priority is below a threshold level.

37. 1. An apparatus comprising: means for monitoring a transmission resource pool in which the device is operating, the transmission resource pool having a plurality of resource block sets, the monitoring being performed for each resource block set of the plurality of resource block sets for which a prohibition timer is not running or has expired, the monitoring being performed to detect listen-before-talk failures of the device for each monitored resource block set of the plurality of resource block sets of the resource pool; means for detecting a listen-before-talk failure of the device for a monitored resource block set of the plurality of resource block sets; means for incrementing a failure counter to a count value; means for starting or restarting a failure detection timer associated with said failure counter; means for triggering or declaring a consistent listen-before-talk failure for the monitored set of resource blocks when the count value exceeds a threshold; means for controlling communications of the device based on the consistent listen-before-talk failure being triggered or declared; An apparatus comprising:

38. 38. The apparatus of claim 37, wherein the failure counter is configured to count listen-before-talk failures at a resource block set level only or at a resource pool and resource block set level.

39. means for starting the prohibit timer for the monitored resource block based on the consistent listen-before-talk failure being triggered or declared; 38. The apparatus of claim 37, further comprising:

40. means for detecting an activity level of the monitored resource blocks; means for triggering early expiration of the inhibit timer based on the activity level being below a threshold; 38. The apparatus of claim 37, further comprising:

41. means for detecting an activity level of the monitored resource blocks; means for extending the inhibit timer based on the activity level exceeding a threshold; 38. The apparatus of claim 37, further comprising:

42. means for stopping the failure detection timer for the monitored resource block based on the consistent listen-before-talk failure being triggered or declared; means for resetting the failure counter based on the consistent listen-before-talk failure being triggered or declared; 38. The apparatus of claim 37, further comprising:

43. means for determining that each of the plurality of resource block sets in the transmission resource pool has been triggered as a consistent listen-before-talk failure and an associated timer for each resource block set has not expired; means for switching to a different transmission resource based on said determining; 38. The apparatus of claim 37, further comprising:

44. 44. The apparatus of claim 43, wherein the different transmission resources comprise at least one of a further transmission resource pool including at least one resource block set different from the transmission resource pool, a sidelink carrier different from a sidelink carrier of the transmission resource pool, or a frequency of interest different from a frequency corresponding to the transmission resource pool.

45. means for determining that a first subset of the plurality of resource block sets in the transmission resource pool are triggered as consistent listen-before-talk failures and an associated timer of each resource block set in the first subset has not expired, while a second subset of the plurality of resource block sets that do not have consistent listen-before-talk failures are triggered or an associated timer of each resource block set in the second subset has expired; means for triggering resource selection of a set of resource blocks of the second subset instead of the first subset for sidelink transmissions for which resources are selected and for which the resources are part of the transmission resource pool; 38. The apparatus of claim 37, further comprising:

46. 46. ​​The apparatus of claim 45, wherein the trigger is conditioned on a resource being within an operating period of the prohibit timer associated with the resource.

47. 46. ​​The apparatus of claim 45, wherein the trigger is conditional on resource reservation already being indicated via a resource reservation duration field of a first stage sidelink control information or a previous transmission.

48. 46. ​​The apparatus of claim 45, wherein the trigger is conditional on resource reservation not already being indicated by first stage sidelink control information.

49. 46. ​​The apparatus of claim 45, wherein the trigger is conditioned on resource reservation being indicated by first stage sidelink control information using a temporal resource allocation field.

50. means for determining that a first subset of the plurality of resource block sets in the transmission resource pool are triggered as a consistent listen-before-talk failure and an associated timer of each resource block set in the first subset has not expired; - means for triggering resource selection of a resource block set for each resource block set of the first subset according to an indication of the remaining time of the associated timer for that resource block set for sidelink transmissions for which no resources have been selected; 38. The apparatus of claim 37, further comprising:

51. 51. The apparatus of claim 50, wherein the selection is from an indicated inclusion set of resource block sets to select, or the selection excludes an indicated exclusion set of resource block sets to exclude from selection.

52. 51. The apparatus of claim 50, wherein the medium access control entity of the apparatus, upon receiving the candidate resource set from the physical layer of the apparatus, excludes from the received candidate resource set all resources that belong to a resource block set for which a consistent listen-before-talk failure has been declared and for which the prohibit timer is running.

53. 51. The apparatus of claim 50, wherein if a medium access control entity of the apparatus has not received a candidate resource set from a physical layer of the apparatus, the medium access control entity indicates to the physical layer an indicated inclusion set of resource block sets to select from, or the selection excludes an indicated exclusion set of resource block sets to exclude from selection.

54. 51. The apparatus of claim 50, wherein the triggered selection of a resource is inhibited solely based on the prohibit timer not having expired if a configured traffic priority is below a threshold level.

55. A computer program product encoded with instructions for performing the method of any of claims 19 to 36.

56. A non-transitory computer readable medium encoded with instructions that, when executed in hardware, perform the method of any of claims 19 to 36.

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