Method and apparatus for handling persistent LBT failure

Abstract

The invention relates to a method and apparatus for handling a persistent listen before talk (LBT) failure. An embodiment of the present disclosure provides a user equipment (UE) comprising: a transceiver; and a processor coupled with the transceiver and configured to: detect a persistent LBT failure in a first sidelink (SL) bandwidth portion (BWP); performing at least one of the following: revoking the startup of the first SL BWP; the first SL BWP is reset; resuming SL transmissions in the first SL BWP in response to one or more conditions being satisfied; or resuming the SL transmission in the second SL BWP.

Description

Technical Field

[0001] The present disclosure relates to wireless transmissions, and more particularly to methods and apparatus for handling persistent listen-before-talk (LBT) failures. Background Art

[0002] In the New Radio Unlicensed (NRU) spectrum, a large number of unlicensed bands or channels are available for wireless transmission (e.g., WiFi, Bluetooth, 3G, 4G, etc.). The LBT process is performed before each transmission to determine whether the unlicensed band or channel is available. If LBT fails, which means that the channel is already occupied, an LBT failure indication is sent from the lower layer (e.g., the physical (PHY) layer) to the medium access control (MAC) entity. The MAC entity can then count the number of LBT failure indications from the lower layer within a time period, and when the number of LBT failure indications exceeds a threshold (e.g., a preconfigured maximum number within the time period), a persistent LBT failure is triggered.

[0003] The sidelink (SL) is a direct link for communication between devices for several applications, such as proximity services (device-to-device (D2D)), vehicle-to-vehicle (V2V), vehicle-to-passenger (V2P), Internet of Things (IoT), wearable devices, etc. SL transmissions that can also operate on unlicensed bands for public safety or commercial purposes need to perform similar LBT procedures defined in the NRU as discussed above. However, if a persistent LBT failure is detected or triggered for the sidelink bandwidth part (SL BWP), the SL transmission will not be started because only one SL BWP is supported for the sidelink. That is, if LBT failures are counted for the SL BWP, then after the persistent LBT failure is triggered, the entire SL BWP is considered to have failed and the SL transmission cannot be performed. The failure of SL transmission may endanger public safety or commercial interests.

[0004] It would therefore be desirable to provide a solution for handling persistent LBT failures in SL BWPs in a SL-U system; furthermore, it would be advantageous to provide a solution for recovering SL communications. Summary of the invention

[0005] An embodiment of the present disclosure provides a user equipment (UE), comprising: a transceiver; and a processor, which is coupled to the transceiver and configured to: detect a persistent LBT failure in a first SL bandwidth part (BWP); perform at least one of the following: deactivate the first SL BWP; reset the first SL BWP; resume SL transmission in the first SL BWP in response to satisfying one or more conditions; or resume the SL transmission in a second SL BWP.

[0006] In some embodiments, the processor is further configured to: determine to autonomously deactivate the first SLBWP; or determine to deactivate the first SL BWP based on an indication from the BS instructing the UE to deactivate the first SL BWP.

[0007] In some embodiments, the processor is further configured to perform at least one of the following in the first SL BWP: suspending the PC5 interface radio resource control (PC5-RRC) connection of all established unicast connections; triggering a SL radio link failure (RLF) for all established unicast connections; or releasing all established unicast connections and indicating the release to the upper layer.

[0008] In some embodiments, suspending the PC5-RRC connection of all established unicast connections further comprises at least one of: storing the PC5-RRC configuration of all suspended unicast connections; or indicating all suspended unicast connections to the upper layer.

[0009] In some embodiments, the processor is further configured to resume all suspended unicast connections in response to the first SL BWP being resumed.

[0010] In some embodiments, the processor is further configured to: determine to autonomously reset the first SL BWP; or determine to reset the first SL BWP based on an indication from the BS instructing the UE to reset the first SL BWP.

[0011] In some embodiments, the processor is further configured to perform at least one of the following in the first SL BWP: releasing data resource blocks (DRBs) for all destinations; releasing signaling resource blocks for all destinations; discarding SL communication-related configurations for all destinations; resetting SL-specific MACs for all destinations; or treating the PC5-RRC connection as released for all unicast destinations.

[0012] In some embodiments, the one or more conditions include: expiration of a timer; a number of LBT successes associated with the first SL BWP is higher than a first threshold; a number of LBT failures associated with the first SL BWP is lower than a second threshold; a result of a channel busy rate (CBR) measurement of the first SL BWP is lower than a third threshold; or an indication from the BS indicating that the first SL BWP has been reconfigured.

[0013] In some embodiments, the processor is further configured to perform at least one of: indicating the persistent LBT failure in the first SL BWP to an upper layer; transmitting an indication indicating the persistent LBT failure in the first SL BWP to the BS; or triggering a cell segmentation process or a cell resection process.

[0014] In some embodiments, the upper layer is configured to perform at least one of: stop SL transmission to all destinations; suspend or release all unicast connections; or configure the second SL BWP.

[0015] In some embodiments, the indication indicating the persistent LBT failure in the first SL BWP comprises a medium access control (MAC) control element (CE) or a radio resource control (RRC) signaling.

[0016] In some embodiments, the RRC signaling indicating the persistent LBT failure in the first SL BWP includes at least one of the following: an RRC establishment request message, which includes a cause or information element (IE) indicating the persistent LBT failure in the first SL BWP; an RRC establishment completion message, which includes an IE indicating the persistent LBT failure in the first SL BWP; an RRC recovery message, which includes an IE indicating the persistent LBT failure in the first SL BWP; an RRC recovery completion message, which includes an IE indicating the persistent LBT failure in the first SL BWP; an RRC reconstruction message, which includes an IE indicating the persistent LBT failure in the first SL BWP; an RRC reconstruction completion message, which includes an IE indicating the persistent LBT failure in the first SLBWP; a SL UE information message, wherein the SL UE information message includes a SL failure IE with a destination parameter, which indicates that the persistent LBT failure is associated with all destinations or with the first SL BWP, and includes an cause indicating the persistent LBT failure in the first SL BWP; or wherein the SL UE information message includes an IE indicating the persistent LBT failure in the first SL BWP.

[0017] In some embodiments, the processor is further configured to: receive a system information block or dedicated signaling indicating the second SL BWP.

[0018] In some embodiments, the processor is further configured to perform at least one of: releasing a stored PC5-RRC configuration; applying a PC5-RRC configuration for the second SL BWP; or resuming all suspended unicast connections.

[0019] In some embodiments, the processor is further configured to: select a cell with a higher priority during the cell segmentation process or the cell excision process, wherein the cell with a higher priority is associated with SL communication in an unlicensed band.

[0020] Another embodiment of the present disclosure provides a base station (BS), comprising: a transceiver; and a processor, which is coupled with the transceiver and configured to: receive an indication indicating a persistent LBT failure in a first SL BWP from a UE; and transmit a second SL BWP to the UE in a system information block or dedicated signaling.

[0021] In some embodiments, the indication comprises a MAC CE or a radio resource control (RRC) signaling.

[0022] Another embodiment of the present disclosure provides a method performed by a UE, which includes: detecting a persistent LBT failure in a first SL BWP; performing at least one of the following: deactivating the first SL BWP; resetting the first SL BWP; resuming SL transmission in the first SL BWP in response to satisfying one or more conditions; or resuming the SL transmission in a second SL BWP.

[0023] Yet another embodiment of the present disclosure provides a method performed by a base station (BS), comprising: receiving an indication indicating a persistent LBT failure in a first SL BWP from a UE; and transmitting a second SLBWP to the UE in a system information block or dedicated signaling. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to describe the manner in which the advantages and features of the present application can be obtained, the description of the present application is presented with reference to specific embodiments thereof, which are illustrated in the accompanying drawings. These drawings depict only example embodiments of the present application and therefore should not be considered to limit the scope thereof.

[0025] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present disclosure.

[0026] Figure 2 A method for handling persistent LBT failure performed by a SL UE according to some embodiments of the present disclosure is described.

[0027] Figures 3A to 3C A method for handling persistent LBT failure performed by a SL UE according to some embodiments of the present disclosure is described.

[0028] Figure 4 A method for handling persistent LBT failure performed by a SL UE according to some embodiments of the present disclosure is described.

[0029] Figure 5 A method for handling persistent LBT failure performed by a SL UE according to some embodiments of the present disclosure is described.

[0030] Figure 6 A method for handling persistent LBT failure performed by a BS according to some embodiments of the present disclosure is described.

[0031] Figure 7 A simplified block diagram illustrating an apparatus according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0032] The detailed description of the drawings is intended as a description of the currently preferred embodiments of the present invention and is not intended to represent the only form in which the present invention can be practiced. It should be understood that the same or equivalent functions can be achieved by different embodiments intended to be included in the spirit and scope of the present invention.

[0033] Although the operations are depicted in a particular order in the figures, those skilled in the art will readily recognize that such operations need not be performed in the particular order shown or in a sequential order, or that all of the illustrated operations need not be performed to achieve a desired result; one or more operations may sometimes be skipped. In addition, the accompanying drawings may schematically depict one or more example processes in the form of a flow chart. However, other operations not depicted may be incorporated into the example processes schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. In some cases, multitasking and parallel processing may be advantageous.

[0034] Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. For ease of understanding, embodiments are provided under specific network architectures and new service scenarios, such as cellular telephone networks, networks based on time division multiple access (TDMA), networks based on code division multiple access (CDMA), networks based on orthogonal frequency division multiple access (OFDMA), LTE networks, networks based on the third generation partnership project (3GPP), LTE, advanced LTE (LTE-A), 3GPP 4G, 3GPP 5G NR, 3GPP Release 16 and higher, satellite communication networks, high altitude platform networks, etc. It is considered that with the development of network architectures and new service scenarios, all embodiments in the present disclosure are also applicable to similar technical problems; and in addition, the terms cited in the present disclosure may be changed, which should not affect the principles of the present disclosure.

[0035] The UE in the NR SL-U scenario may be referred to as a SL UE. A SL UE transmitting data on a side link in an unlicensed spectrum may be referred to as a transmitting UE, a transmitting UE, a transmitting SL UE, a Tx SL UE, a Tx UE, a SL Tx UE, a SL BWP Tx UE, a UE, or the like. A SL UE receiving data on a side link in an unlicensed spectrum may be referred to as a receiving UE, a receiving UE, a receiving SL UE, a Rx UE, a Rx SL UE, a SL Rx UE, a UE, or the like.

[0036] SL UEs may include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart TVs (e.g., TVs connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle-mounted computers, network devices (e.g., routers, switches, and modems), Internet of Things (IoT) devices, personal computers (PCs), gaming consoles, extended reality (XR) devices, or the like.

[0037] According to some embodiments of the present disclosure, the SL UE may include a portable wireless communication device, a smart phone, a cellular phone, a flip phone, a device with a subscriber identification module, a personal computer, a selective call receiver, or any other device capable of sending and receiving communication signals on a wireless network.

[0038] According to some embodiments of the present disclosure, the SL UE may include a wearable device, such as a smart watch, a fitness band, an optical head-mounted display, or the like. In addition, the SL UE may be referred to as a subscriber unit, a mobile device, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device or described using other terms used in the art. The SL UE may communicate directly with the BS via a communication signal.

[0039] The BS in the NR SL-U scenario may be referred to as a base unit, base, access point, access terminal, macro cell, Node B, enhanced Node B (eNB), gNB, home Node B, relay node, device, remote unit or any other term used in the art. The BS may be distributed throughout a geographic area. Typically, a BS is part of a radio access network, which may include one or more controllers communicatively coupled to one or more corresponding base stations.

[0040] The BS is typically communicatively coupled to one or more packet core networks (PCNs), which may be coupled to other networks, such as a packet data network (PDN) (e.g., the Internet) and a public switched telephone network, among other networks. These and other elements of the radio access and core networks are not illustrated, but are generally well known to those of ordinary skill in the art. For example, one or more BSs can be communicatively coupled to a mobility management entity (MME) or access and mobility management function (AMF), a serving gateway (SGW), a packet data network gateway (PGW), and / or a user plane function (UPF).

[0041] A BS may serve several SL UEs in a service area, such as a cell or a cell sector, via wireless communication links. A BS may communicate directly with one or more SL UEs via communication signals. For example, a BS may serve SL UEs in a macro cell.

[0042] In the NR SL-U scenario, the sidelink communication between the Tx UE and the receiving (Rx) UE includes multicast communication, unicast communication or broadcast communication.

[0043] Figure 1 A wireless communication system 100 (eg, a SL-U communication system) according to some embodiments of the present disclosure is described.

[0044] like Figure 1 As shown in , the wireless communication system 100 includes a base station (e.g., BS102) and some UEs (e.g., UE 101-A, UE 101-B, UE 101-C, and UE 101-D). UE 101-A and UE 101-B are within the coverage of BS102, and UE 101-C and UE 101-D are outside the coverage of BS102. UE 101-A, UE 101-B, UE 101-C, and UE 101-D may perform sidelink unicast transmission, sidelink multicast transmission, or sidelink broadcast transmission in an unlicensed spectrum, such as SL BWP. UE 101-A, UE 101-B, UE 101-C, and UE 101-D may be referred to as SL UEs. It is contemplated that according to some other embodiments of the present disclosure, the SL-U communication system may include more BSs and more or fewer SL UEs.

[0045] In addition, despite Figure 1 The SL UE shown in the figure is illustrated in the shape of a mobile phone, but it is considered that according to some other embodiments of the present disclosure, the SL communication system may include any type of UE (e.g., a roadmap device, a mobile phone, a computer, a laptop computer, an IoT device, or other types of devices).

[0046] according to Figure 1In some embodiments, UE 101-A may be used as a Tx UE, and UE 101-B, UE 101-C, and UE 101-D may be used as Rx UEs. UE 101-A may exchange SL messages with UE 101-B or UE 101-C via a side link using, for example, NR technology or LTE technology via a PC5 interface as defined in a 3GPP document. UE 101-A may transmit information or data to other UEs within the SL-U communication system via side link unicast, side link multicast, or side link broadcast. For example, UE 101-A may transmit data to UE 101-B in a side link unicast session. UE 101-A may transmit data to UE 101-B and UE 101-C in a multicast group via a side link multicast transmission session. In addition, UE 101-A may transmit data to UE 101-B and UE 101-C via a side link broadcast transmission session.

[0047] Alternatively, according to Figure 1 In some other embodiments, UE 101-B or UE 101-C may function as a Tx UE and transmit information or data, and UE 101-A may function as a Rx UE and receive information or data from UE 101-B or UE 101-C.

[0048] Figure 1 Both UE 101-A and UE 101-B in the embodiment of can transmit information to BS 102 and receive control information from BS 102, for example, via a Uu interface. BS 102 can define one or more cells, and each cell can have a coverage area. Figure 1 As shown in , both UE 101-A and UE 101-B are within the coverage of BS 102, while UE 101-C and UE 101-D are not within the coverage of BS 102.

[0049] like Figure 1 BS102 described and shown in the figure may not be a specific base station, but may be any base station in the SL-U communication system. For example, assuming that the SL-U communication system includes two BSs, a situation where UE 101-A is within the coverage area of ​​either of the two BSs may be referred to as a situation where UE 101-A is within the coverage area of ​​the BS in the SL-U communication system; and a situation where only UE 101-A is outside the coverage areas of the two BSs may be referred to as a situation where UE 101-A is outside the coverage area of ​​the BS in the SL-U communication system.

[0050] The UE may operate in different modes. At least the following two sidelink resource allocation modes are defined for sidelink communication: Resource Allocation Mode 1: The BS may schedule sidelink resources for the UE to use for sidelink transmission; and Resource Allocation Mode 2: The UE may determine the sidelink transmission resources within the sidelink resources configured by the BS or the network or the pre-configured sidelink resources. In Resource Allocation Mode 2, the BS may not schedule sidelink resources for the UE. Figure 1 In some embodiments, UE 101-A and UE 101-B may be in resource allocation mode 1, and UE 101-C and UE 101-D may be in resource allocation mode 2. In some other cases, UE 101-A and UE 101-B may also operate in resource allocation mode 2. In the following of the present disclosure, "mode 1" may refer to resource allocation mode 1, and "mode 2" may refer to resource allocation mode 2.

[0051] A persistent LBT failure may be detected for a SL BWP, a SL carrier, a SL frequency band, etc. A SL BWP or a SL carrier with a persistent LBT failure may be referred to as a "problematic SL BWP" or a "problematic SL carrier." In the following of this disclosure, the terms "SL carrier" or "SL BWP" may be used interchangeably where appropriate.

[0052] For the NR side link, only one carrier can be configured, and one carrier supports only one BWP. In the case of a persistent LBT failure detected for the SL BWP, the entire SL communication may be suspended. In the NR side link, there may be a SL RLF procedure to handle the radio link failure problem. However, the SL RLF procedure may only target the unicast link, which does not completely solve the problem. Therefore, a solution for handling persistent LBT failures in the SL BWP or SL carrier and a solution for recovering SL communications are needed.

[0053] In particular, the solution of the present disclosure involves two aspects, 1): a solution for handling persistent LBT failure in SL BWP or SL carrier; and 2): a solution for recovering SL communication.

[0054] Regarding how to handle persistent LBT failure in SL BWP (or SL carrier, in the following of this disclosure, only the term "SL BWP" is used, and it should be noted that the term "SL BWP" can be replaced with "SL carrier"), the following solutions are proposed:

[0055] Solution 1-1:

[0056] In this solution, when a persistent LBT failure in the SL BWP is detected, or a persistent LBT failure is triggered for the SL BWP, the deactivation of the SL BWP may be triggered. In other words, the SL UE may deactivate the SL BWP.

[0057] In one embodiment, the SL UE may be in RRC_IDLE state, RRC_INACTIVE state or resource allocation mode 2, or the SL UE may be out of coverage. When a persistent LBT failure in the SL BWP is detected, or a persistent LBT failure is triggered for the SL BWP, the SL UE may autonomously deactivate the SL BWP.

[0058] In another embodiment, the SL UE may be in RRC_CONNECTED state, resource allocation mode 1, or the SL UE may be within coverage. When a persistent LBT failure in the SL BWP is detected, or a persistent LBT failure is triggered for the SL BWP, the SL UE may report the persistent LBT failure about the SL BWP to the BS. The BS may transmit an indication to the UE, the indication instructing the UE to deactivate the SLBWP. Upon receiving an indication of deactivation of the SL BWP from the BS, the SL UE may deactivate the SL BWP.

[0059] Specifically, deactivation of SL BWP may include the following operations:

[0060] -SL UE may perform at least one of the following:

[0061] Stop transmitting or receiving the side link;

[0062] Suspension of CG Type 1 authorization;

[0063] Clear CG Type 2 authorization; or

[0064] Cancel Scheduling Request (SR), Buffer Status Report (BSR), SL - Channel State Information (CSI) (if triggered).

[0065] - In case the SL UE has been configured with only one SL BWP, the SL UE may handle the unicast connection with at least one of the following options:

[0066] Option 1-1: The SL UE may suspend the PC5-RRC connection of all established unicast connections. Specifically, the SL UE may store the PC5-RRC configuration of all suspended unicast connections per unicast connection. The SL UE may report (or indicate) the suspended unicast connection to a higher layer (e.g., a V2X layer).

[0067] In some embodiments, when the problematic SL BWP is restored, the SL UE can restore all suspended unicast connections. In some other embodiments, a new SL BWP can be used to indicate the SL UE, and SL-U communication can be restored in the new SL BWP, and the SLUE can release all stored PC5-RRC configurations and apply the PC5-RRC configurations to the new SL BWP, thereby restoring all suspended unicast connections.

[0068] • Option 1-2: The SL UE may consider the sidelink radio link failure and may trigger SL RLF for all established unicast connections.

[0069] Option 1-3: The SL UE may release the SL data RBs and SL signaling RBs, discard the corresponding radio configuration, reset the MAC layer, consider releasing the PC5-RRC connection for all unicast connections, and report (or indicate) to the higher layers of the UE.

[0070] Solution 1-2:

[0071] In this solution, when a persistent LBT failure in the SL BWP is detected, or a persistent LBT failure is triggered for the SL BWP, a SL BWP reset may be triggered.

[0072] In one embodiment, the SL UE may be in RRC_IDLE state, RRC_INACTIVE state or resource allocation mode 2, or the SL UE may be out of coverage. When a persistent LBT failure in the SL BWP is detected or a persistent LBT failure is triggered for the SL BWP, the SL UE may autonomously reset the SL BWP.

[0073] In another embodiment, the SL UE may be in RRC_CONNECTED state, resource allocation mode 1, or the SL UE may be within coverage. When a persistent LBT failure in the SL BWP is detected, or a persistent LBT failure is triggered for the SL BWP, the SL UE may report to the BS indicating the persistent LBT failure of the SL BWP. The BS may transmit an indication to the UE, the indication instructing the UE to reset the SLBWP. When receiving an indication for resetting the SL BWP from the BS, the SL UE may reset the SL BWP.

[0074] Specifically, the reset of the SL BWP may include the following operations:

[0075] - Release the DRBs for all destinations, which may include all unicast destinations, all broadcast destinations, all multicast destinations, or any other destinations;

[0076] - Release the SRBs of all destinations;

[0077] - discard NR sidelink communication related configurations of all destinations;

[0078] - Reset the sidelink-specific MAC for all destinations; or

[0079] - The PC5-RRC connection is considered released for all unicast destinations.

[0080] Regarding how to recover SL communication after a persistent LBT failure is triggered in the SL BWP, the present disclosure proposes that SL communication can be recovered in the problematic SL BWP, or in a new SL BWP, and the details are described in the following solution.

[0081] Solution 2-1:

[0082] In solution 2-1, SL communication can be restored in the problematic SL BWP. The SL UE can take the following options to restore SL communication in the problematic SL BWP as follows:

[0083] Option 2-1A:

[0084] Option 2-1A involves a SL UE operating in resource allocation mode 1 or resource allocation mode 2. When a persistent LBT failure is triggered for the SL BWP, the SL UE may start a timer, and the length of the timer may be indicated by the network, for example, via an indication from the BS, or may be preconfigured or configured. The SL UE may also deactivate the SL BWP as described in Option 1 above.

[0085] When the timer is running, that is, during the time period of the timer, the SL UE may be prohibited from performing SL communication in the SL BWP, in other words, the resources in the SL BWP may be prohibited from being used for SL communication. When the timer expires, the SL UE may consider that the problematic SLBWP is restored, that is, the SL BWP can be used for SL communication, and the SL UE may restore all suspended unicast connections. When the timer expires, the SL BWP may also be called available.

[0086] Option 2-1B:

[0087] Option 2-1B involves a SL UE operating in resource allocation mode 1 or resource allocation mode 2. When a persistent LBT failure is triggered for the SL BWP, the SL UE may continuously perform the LBT process on the SL BWP. For example, the SL UE may perform the LBT process on the SL BWP in a periodic manner. The LBT process may be any type of LBT process, for example, LBT type 1, LBT type 2a, LBT type b, LBT category 1 (category 1), LBT category 2, LBT category 4, etc. The periodicity for performing the LBT process may be indicated by the BS, by the network, or may be configured or preconfigured.

[0088] In some embodiments, a first threshold and a time period may be used to determine whether the SL BWP is recovered. The first threshold may be associated with the cumulative number of LBT successes (or the number of consecutive LBT successes). The value of the first threshold and / or the time period may be indicated by the BS, by the network, or may be configured or preconfigured. During the time period, if the cumulative number of LBT successes (or the number of consecutive LBT successes) is higher (or greater) than the first threshold, the SL BWP is considered to be recovered or available and can be used for SL transmission.

[0089] In some embodiments, a second threshold and a time period may be used to determine whether the SL BWP is recovered. The second threshold may be associated with the number of accumulated LBT failures. The value of the second threshold and / or the time period may be indicated by the BS, by the network, or may be configured or preconfigured. If the number of accumulated LBT failures during the time period is less than the second threshold, the SL BWP is considered recovered or available and can be used for SL transmission.

[0090] Option 2-1C:

[0091] Option 2-1C involves a SL UE operating in resource allocation mode 1 or resource allocation mode 2. When a persistent LBT failure is triggered for the SL BWP, the SL UE may continuously, for example, perform CBR measurement on the SL BWP in a periodic manner. The threshold associated with the CBR measurement may be indicated by the BS, by the network, or may be configured or preconfigured. When the CBR measurement result is lower than the threshold, that is, the load of the SL BWP is lower than the threshold, the SL BWP is considered to be recovered or available and can be used for SL transmission.

[0092] Option 2-1D

[0093] Option 2-1D involves a SL UE operating in resource allocation mode 1. When a persistent LBT failure is triggered for a SL BWP, the SL UE in mode 1 may receive an indication from the BS, which may indicate that the SL BWP is recovered, or reconfigured, or available. The UE may then consider the SL BWP to be recovered or available. The BS may determine whether the SL BWP is recovered or available by collecting other SL-UE transmission information on the SL BWP.

[0094] When recovering the SL BWP, in the case where the UE may have marked the SL BWP as problematic, or determined that the SL BWP is associated with a lower priority (e.g., "low"), after the SL BWP is recovered, the UE may remove the problematic label, or determine that the SL BWP is associated with a higher priority (e.g., "high").

[0095] Solution 2-2:

[0096] In solution 2-2, SL communication may be resumed in the new SL BWP. The SL UE may take the following options to resume SL communication in the new SL BWP, as described in the following options:

[0097] Option 2-2A

[0098] Option 2-2A involves a SL UE that is out of coverage. The SL UE may indicate to an upper layer (e.g., a V2X layer or a NAS layer) a persistent LBT failure of the SL BWP. For example, the AS layer may report a persistent LBT failure to the NAS layer. Upon receiving the indication, the NAS layer may stop SL transmission to all destinations and suspend or release the corresponding unicast connection. The NAS layer may reconfigure a new SL BWP for the AS layer to resume SL communication in the AS layer.

[0099] Figure 2 A method for handling persistent LBT failure performed by a SL UE according to some embodiments of the present disclosure is described.

[0100] In operation 201, when a persistent LBT failure is triggered on the SL BWP (or the UE detects a persistent LBT failure on the SL BWP), the SL UE may handle the problematic BWP. For example, the SL UE may handle the problematic BWP as described in Option 1 or Option 2 above, that is, the SL UE may autonomously deactivate the SL BWP, or may autonomously reset the SL BWP.

[0101] At operation 202, the SL UE may report (or indicate) a persistent LBT failure of the SL BWP to an upper layer (eg, a V2X layer or a NAS layer).

[0102] The upper layer may reconfigure a new SL BWP in operation 203. The UE may resume SL communication in the new SL BWP.

[0103] Option 2-2B

[0104] Option 2-2B involves a SL UE in RRC_CONNECTED state, resource allocation mode 1, or the SL UE may be within coverage.

[0105] When a persistent LBT failure is triggered on a SL BWP (or the UE detects a persistent LBT failure on a SL BWP), the SL UE may report the persistent LBT failure of the SL BWP to the BS. Specifically, the SL UE may transmit an indication to the BS indicating the persistent LBT failure of the SL BWP. The indication may be a MAC CE or RRC signaling.

[0106] In some embodiments, the indication may be a MAC CE, and the SL UE may transmit a MAC CE indicating that a persistent LBT failure is triggered in the SL BWP, or indicating that the SL UE has detected a persistent LBT failure in the SL BWP, or indicating that the SL BWP has failed and cannot be used. The MAC CE may be a zero-bit MAC CE, for example, a MAC CE containing only a subheader.

[0107] In some other embodiments, the indication may be RRC signaling.

[0108] When the SL UE is in the RRC_IDLE state or the RRC_INACTIVE state, it may be triggered to establish (or re-establish) an RRC connection with the BS and enter the RRC CONNECTED state. In this case, the RRC signaling may include the following:

[0109] - an RRC setup request message, such as an RRCsetupRequest message; wherein an IE is included in the message, or a cause (which may be an IE) is included in the message, to indicate a persistent LBT failure in the SL BWP;

[0110] -RRC setup complete message, such as RRCSetupComplete message, where an IE (or cause) is included in the message to indicate persistent LBT failure in SL BWP;

[0111] -RRC recovery message, such as RRCResume message, where an IE (or cause) is included in the message to indicate a persistent LBT failure in SLBWP;

[0112] -RRC recovery complete message, such as RRCResumeComplete message, where an IE (or cause) is included in the message to indicate the persistent LBT failure in the SL BWP;

[0113] -RRC re-establishment message, such as RRCReestablishment message, where an IE (or cause) is included in the message to indicate a persistent LBT failure in the SL BWP;

[0114] -RRC re-establishment complete message, such as RRCReestablishmentComplete message, where an IE (or cause) is included in the message to indicate persistent LBT failure in SL BWP.

[0115] When the SL UE enters the RRC CONNECTED state from the RRC_IDLE state or the RRC_INACTIVE state, or when the SL UE is already in the RRC CONNECTED state, once the persistent LBT failure in the SL BWP is triggered, the SL UE may be triggered to send a SL UE information message, such as a SidelinkUEInformationNR message, to the BS.

[0116] The RRC signaling message may include a SL failure IE (eg, SL-Failure IE). In the SL failure IE, the SL UE may set the default destination ID to sl-DestinationIdentity-r16, which indicates that all destinations of SL communications have failed, or indicates a persistent LBT failure in the SL BWP.

[0117] In addition, the SL UE may set the cause of sl-Failure-r16 (e.g., consistentLBTfailure) to indicate that a persistent LBT failure has occurred in the SL BWP. Alternatively, the SL UE may use an IE (e.g., SidelinkUEInformationNR) in an RRC signaling message to indicate a persistent LBT failure of the corresponding SL BWP. The BS may configure a new SL carrier for the UE to resume SL communication (e.g., via an RRC Reconfiguration message).

[0118] Figures 3A to 3C A method for handling persistent LBT failure performed by a SL UE according to some embodiments of the present disclosure is described.

[0119] exist Figure 3A , SL UE may be within coverage and operate in resource allocation mode 1.

[0120] In operation 301A, when a persistent LBT failure is triggered on the SL BWP (or the UE detects a persistent LBT failure on the SL BWP), the SL UE may handle the problematic BWP. For example, the SL UE may handle the problematic BWP as described in Solution 1-1 or Solution 1-2 above, that is, the SL UE may undo the start of the SL BWP, or reset the SL BWP.

[0121] At operation 302A, the SL UE may indicate to the BS the persistent LBT failure of the SL BWP, for example, the SL UE may transmit an indication, such as RRC signaling or MAC CE.

[0122] In operation 303A, the BS may configure a new SL BWP, and transmit a SIB or dedicated signaling indicating the new SL BWP to the SL UE.

[0123] exist Figure 3B , SL UE can operate within the coverage area and in resource allocation mode 1.

[0124] At operation 301B, when persistent LBT failure is triggered on the SL BWP (or the UE detects persistent LBT failure on the SL BWP), the SL UE may indicate the persistent LBT failure of the SL BWP to the BS. For example, the SL UE may transmit an indication via RRC signaling or MACCE.

[0125] At operation 302B, the BS may configure a new SL BWP, and transmit a SIB or dedicated signaling indicating the new SL BWP to the SL UE.

[0126] exist Figure 3C , SL UE can operate within the coverage area and in resource allocation mode 2.

[0127] In operation 301C, the SL UE may handle the problematic BWP. For example, the SL UE may handle the problematic BWP as described in the above solution 1-1 or solution 1-2, that is, the SL UE may undo the activation of the SL BWP or reset the SL BWP.

[0128] At operation 302C, the SL UE may establish (or re-establish) an RRC connection with the BS and enter an RRC CONNECTED mode. The SL UE may transmit RRC signaling to request a new SL BWP.

[0129] In operation 303C, the BS may configure a new SL BWP, and transmit a SIB or dedicated signaling indicating the new SL BWP to the SL UE.

[0130] Option 2-3B

[0131] Option 2-3B involves a SL UE in RRC IDLE state or RRC INACTIVE state.

[0132] When a persistent LBT failure is triggered on the SL BWP (or the UE detects a persistent LBT failure on the SL BWP), the SL UE may be triggered to perform a cell selection procedure or a cell reselection procedure.

[0133] During the cell selection process (or cell reselection process), for example, some cells may provide frequencies and sidelink configurations for SL communications on unlicensed bands, and the cells may be determined to have a higher priority than other cells. Therefore, the SL UE may select a cell with a higher priority than other cells.

[0134] Figure 4 A method for handling persistent LBT failure performed by a SL UE according to some embodiments of the present disclosure is described.

[0135] Figure 4 , SL UE is within coverage and operates in mode 2.

[0136] In operation 401, when a persistent LBT failure is triggered on the SL BWP (or the UE detects a persistent LBT failure on the SL BWP), the SL UE may handle the problematic BWP. For example, the SL UE may handle the problematic BWP as described in Solution 1-1 or Solution 1-2 above, that is, the SL UE may undo the start of the SL BWP, or reset the SL BWP.

[0137] At operation 402, the SL UE may trigger a cell selection procedure (or a cell reselection procedure).

[0138] Figure 5 A method for handling persistent LBT failure performed by a SL UE according to some embodiments of the present disclosure is described.

[0139] In operation 501, the SL UE may detect a persistent LBT failure in the first SL BWP. In operation 502, the SL UE may perform at least one of the following: deactivate the first SL BWP; reset the first SL BWP; resume SL transmission in the first SL BWP in response to satisfying one or more conditions; or resume SL transmission in the second SL BWP.

[0140] In some embodiments, the UE may determine to autonomously deactivate the first SL BWP; or determine to deactivate the first SL BWP based on an instruction from the BS instructing the UE to deactivate the first SL BWP.

[0141] In some embodiments, the UE may perform at least one of the following in the first SL BWP: suspend the PC5-RRC connection of all established unicast connections; trigger SL RLF for all established unicast connections; or release all established unicast connections and indicate the release to the upper layer.

[0142] In some embodiments, suspending the PC5-RRC connections of all established unicast connections further includes at least one of: storing the PC5-RRC configurations of all suspended unicast connections; or indicating all suspended unicast connections to an upper layer.

[0143] In some embodiments, in response to the first SL BWP being resumed, the UE may resume all suspended unicast connections.

[0144] In some embodiments, the UE may determine to reset the first SL BWP autonomously; or determine to reset the first SL BWP based on an indication from the BS instructing the UE to reset the first SL BWP.

[0145] In some embodiments, the UE may perform at least one of the following in the first SL BWP:

[0146] - Release the DRBs of all destinations;

[0147] - Release the SRBs of all destinations;

[0148] -Discard all SL communication related configurations of the destination;

[0149] - Reset the SL-specific MAC for all destinations; or

[0150] - The PC5-RRC connection is considered released for all unicast destinations.

[0151] In some embodiments, one or more conditions include: expiration of a timer (e.g., the condition described in option 2-1A above); the number of LBT successes associated with the first SL BWP is higher than a first threshold (e.g., the condition described in option 2-1B above); the number of LBT failures associated with the first SL BWP is lower than a second threshold (e.g., the condition described in option 2-1B above); the CBR measurement result on the first SL BWP is lower than a third threshold (e.g., the condition described in option 2-1C above); or an indication from the BS indicating that the first SL BWP has been reconfigured (e.g., the condition described in option 2-1D above).

[0152] In some embodiments, the UE may perform at least one of the following: indicate to the upper layer the persistent LBT failure in the first SL BWP; transmit to the BS an indication indicating the persistent LBT failure in the first SL BWP; or trigger a cell segmentation procedure or a cell resection procedure.

[0153] In some embodiments, upper layers are configured to perform at least one of: stop SL transmission to all destinations; suspend or release all unicast connections; or configure a second SL BWP.

[0154] In some embodiments, the indication of persistent LBT failure in the first SL BWP includes MAC CE or RRC signaling.

[0155] In some embodiments, the RRC signaling indicating the persistent LBT failure in the first SL BWP includes at least one of the following:

[0156] -RRC Setup Request message including a cause or IE indicating a persistent LBT failure in the first SL-BWP;

[0157] -RRC Setup Complete message including an IE indicating a persistent LBT failure in the first SL-BWP;

[0158] -RRC Recovery message including an IE indicating a persistent LBT failure in the first SL-BWP;

[0159] -RRC Recovery Complete message including an IE indicating a persistent LBT failure in the first SL-BWP;

[0160] -RRC Re-establishment message including an IE indicating a persistent LBT failure in the first SL-BWP;

[0161] -RRC Reestablishment Complete message including an IE indicating a persistent LBT failure in the first SL-BWP; or

[0162] -SL UE information message, wherein the SL UE information message includes a SL failure IE with a destination parameter, which indicates that the persistent LBT failure is associated with all destinations or is associated with the first SL-BWP, and includes a cause indicating the persistent LBT failure in the first SL-BWP; or wherein the SL UE information message includes an IE indicating the persistent LBT failure in the first SL-BWP.

[0163] In some embodiments, the UE may receive a system information block or dedicated signaling indicating the second SL BWP.

[0164] In some embodiments, the UE may perform at least one of: releasing the stored PC5-RRC configuration; applying the PC5-RRC configuration for the second SL BWP; or resuming all suspended unicast connections.

[0165] In some embodiments, the UE may select a cell with a higher priority during a cell segmentation procedure or a cell excision procedure, wherein the cell with a higher priority is associated with SL communication in an unlicensed band.

[0166] Figure 6 A method for handling persistent LBT failure performed by a BS according to some embodiments of the present disclosure is described.

[0167] In operation 601, the BS may receive an indication indicating a persistent LBT failure in a first SL BWP from a UE. In operation 602, the BS may transmit a second SL BWP to the UE in a system information block or dedicated signaling.

[0168] In some embodiments, the indication comprises MAC CE or RRC signaling.

[0169] Figure 7 A simplified block diagram illustrating exemplary apparatus according to some embodiments of the present disclosure.

[0170] like Figure 7 , an example of an apparatus 700 may include at least one processor 704 and at least one transceiver 702 coupled to the processor 704. The apparatus 700 may be a UE, a SL UE, a Tx SL UE, a Rx SL UE, a BS, a RAN node, or any other device having similar functionality.

[0171] Although in this figure, elements such as at least one transceiver 702 and processor 704 are described in the singular, the plural is also contemplated unless limitation to the singular is explicitly stated. In some embodiments of the present disclosure, the transceiver 702 may be divided into two devices, such as a receive circuit system and a transmit circuit system. In some embodiments of the present disclosure, the device 700 may further include an input device, a memory, and / or other components.

[0172] In some embodiments of the present disclosure, the device 700 may be a UE. The transceiver 702 and the processor 704 may interact with each other to perform Figures 1 to 6 In some embodiments of the present disclosure, the device 700 may be a node. The transceiver 702 and the processor 704 may interact with each other to perform the operations of the UE described in any of the embodiments. Figures 1 to 6 The operation of a node described in any of .

[0173] In some embodiments of the present disclosure, the apparatus 700 may further include at least one non-transitory computer-readable medium.

[0174] For example, in some embodiments of the present disclosure, a non-transitory computer-readable medium may store computer-executable instructions to enable the processor 704 to implement the method for the UE as described above. For example, when the computer-executable instructions are executed, the processor 704 interacting with the transceiver 702 executes Figures 1 to 6 Operation of the UE described in any one of .

[0175] In some embodiments of the present disclosure, a non-transitory computer-readable medium may store computer-executable instructions to cause the processor 704 to implement the method for the node as described above. For example, when the computer-executable instructions are executed, the processor 704 interacting with the transceiver 702 executes Figures 1 to 6 The operation of a node described in any of .

[0176] The methods of the present disclosure may be implemented on a programmed processor. However, the controller, flow charts, and modules may also be implemented on a general or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit components, integrated circuits, hardware electronic or logic circuits (e.g., discrete element circuits, programmable logic devices, or the like). In general, any device having a finite state machine capable of implementing the flow charts shown in the figures may be used to implement the processing functions of the present disclosure.

[0177] Although the present disclosure has been described with its specific embodiments, it is apparent that those skilled in the art will appreciate many alternatives, modifications and variations. For example, the various components of the embodiments may be interchanged, added or replaced in other embodiments. In addition, all elements shown in each figure are not necessary for the operation of the disclosed embodiments. For example, those skilled in the art of the disclosed embodiments will be able to make and use the teachings of the present disclosure by simply adopting the elements of the independent claims. Therefore, the embodiments of the present disclosure as described herein are intended to be illustrative, not restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0178] In the present disclosure, relational terms, such as "first", "second" and the like can only be used to distinguish one entity or action from another entity or action, and do not necessarily require or imply any actual relationship or order between such entities or actions. The term "comprises, comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also may include other elements that are not explicitly listed or inherent to this process, method, article or equipment. In the absence of more restrictions, elements starting with "one", "one" or the like do not exclude the presence of additional identical elements in the process, method, article or equipment including the elements. In addition, the term "another" is defined as at least the second or more. The terms "include", "have" and the like as used herein are defined as "include".

Claims

1. A user equipment UE, comprising: Transceiver; and a processor coupled to the transceiver and configured to: Detect failure of continuous listen-before-talk LBT in the first side link SL bandwidth part BWP; Do at least one of the following: Unactivate the first SL BWP; Reset the first SL BWP; Resuming SL transmission in the first SL BWP in response to one or more conditions being satisfied; or The SL transmission in the second SL BWP is resumed.

2. The UE of claim 1, wherein the processor is further configured to: Determine the autonomous cancellation of initiation of the first SL BWP; or Determining to deactivate the first SL BWP is based on an instruction from the BS instructing the UE to deactivate the first SL BWP.

3. The UE of claim 2, wherein the processor is further configured to perform, in the first SL BWP, at least one of the following: Suspend the PC5 interface radio resource control PC5-RRC connection of all established unicast connections; Triggering SL Radio Link Failure RLF for all established unicast connections; or All established unicast connections are released and the release is indicated to upper layers.

4. The UE according to claim 3, wherein suspending the PC5-RRC connection of all established unicast connections further comprises at least one of the following: storing the PC5-RRC configuration for all suspended unicast connections; or All suspended unicast connections are indicated to the upper layers. 5 . The UE of claim 3 , wherein the processor is further configured to resume all suspended unicast connections in response to the first SL BWP being resumed.

6. The UE of claim 1, wherein the processor is further configured to: Determine to autonomously reset the first SL BWP; or Determining to reset the first SLBWP based on an indication from the BS instructing the UE to reset the first SL BWP.

7. The UE of claim 1, wherein the one or more conditions include: The timer expires; The number of LBT successes associated with the first SL BWP is above a first threshold; a number of LBT failures associated with the first SL BWP is below a second threshold; A result of measuring the channel busy rate CBR of the first SL BWP is lower than a third threshold; or An indication from the BS indicating that the first SL BWP is reconfigured.

8. The UE of claim 1, wherein the processor is further configured to perform at least one of the following: Indicating to an upper layer the persistent LBT failure in the first SL BWP; transmitting an indication to the BS indicating the persistent LBT failure in the first SL BWP; or Triggering the cell segmentation process or cell removal process.

9. The UE of claim 8, wherein the upper layer is configured to perform at least one of: Stop SL launches to all destinations; Suspend or release all unicast connections; or Configure the second SL BWP. 10 . The UE of claim 8 , wherein the indication indicating the persistent LBT failure in the first SL BWP comprises a Medium Access Control (MAC) control element (CE) or a Radio Resource Control (RRC) signaling.

11. The UE of claim 10, wherein the RRC signaling indicating the persistent LBT failure in the first SL BWP comprises at least one of the following: An RRC setup request message including a cause or information element IE indicating the continued LBT failure in the first SL-BWP; an RRC setup complete message including an IE indicating the continued LBT failure in the first SL-BWP; an RRC recovery message including an IE indicating the continued LBT failure in the first SL-BWP; an RRC recovery complete message including an IE indicating the continued LBT failure in the first SL-BWP; an RRC reestablishment message including an IE indicating the continued LBT failure in the first SL-BWP; An RRC Reestablishment Complete message comprising an IE indicating the persistent LBT failure in the first SL-BWP; or A SL UE information message, wherein the SL UE information message includes a SL failure IE with a destination parameter, indicating that the persistent LBT failure is associated with all destinations or is associated with the first SL-BWP, and includes a cause indicating the persistent LBT failure in the first SL-BWP; or wherein the SL UE information message includes an IE indicating the persistent LBT failure in the first SL-BWP.

12. The UE of claim 8, wherein the processor is further configured to: A system information block or dedicated signaling indicating the second SL BWP is received.

13. The UE of claim 8, wherein the processor is further configured to: A cell with a higher priority is selected during the cell segmentation procedure or the cell excision procedure, wherein the cell with a higher priority is associated with SL communication in an unlicensed frequency band.

14. A base station BS, comprising: Transceiver; and a processor coupled to the transceiver and configured to: receiving an indication from a user equipment UE indicating failure of continuous listen-before-talk LBT in the first side link SL bandwidth part BWP; and The second SL BWP is transmitted to the UE in a system information block or dedicated signaling.

15. A method performed by a user equipment UE, comprising: Detect failure of continuous listen-before-talk LBT in the first side link SL bandwidth part BWP; Do at least one of the following: Unactivate the first SL BWP; Reset the first SL BWP; Resuming SL transmission in the first SL BWP in response to one or more conditions being satisfied; or The SL transmission in the second SL BWP is resumed.

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