Method and apparatus for handling LBT for sidelink communication

Abstract

The present disclosure relates to a 5th-Generation (5G) or 6th-Generation (6G) communication system for supporting higher data transmission rates. A method performed by a user equipment (UE) in a wireless communication system is provided. The method includes receiving configuration information associated with a sidelink (SL) listen before talk (LBT) failure recovery from a base station; identifying a counter value associated with the SL LBT failure detection based on the SL LBT failure indication received from the lower layer; and when the counter value is greater than or equal to the threshold value, triggering the SL to continue LBT failure.

Description

Technical Field

[0001] The present disclosure relates to a wireless communication system, and more particularly, to a method and apparatus for handling a listen-before-talk (LBT) failure in a wireless communication system. Background Art

[0002] The fifth generation (5G) mobile communication technology defines a wide frequency band so that high transmission rates and new services are possible, and can be implemented not only in the "below 6 GHz" band such as 3.5 GHz, but also in the "above 6 GHz" band called millimeter waves including 28 GHz and 39 GHz. In addition, in order to achieve a transmission rate fifty times faster than that of 5G mobile communication technology and an ultra-low latency one-tenth of that of 5G mobile communication technology, the implementation of the sixth generation (6G) mobile communication technology (called a super 5G system) in the terahertz band (e.g., 95 GHz to 3 THz band) has been considered.

[0003] In the early stages of 5G mobile communication technology development, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra reliable low latency communication (URLLC), and massive machine-type communication (mMTC), standardization has been underway on the following: beamforming and massive multiple-input multiple-output (MIMO) for mitigating radio wave path loss and increasing radio wave transmission distance in millimeter waves; support for basic parameter sets (e.g., operating multiple subcarrier spacings) for efficient use of millimeter wave resources and dynamic operation of time slot formats; initial access technology for supporting multi-beam transmission and broadband; definition and operation of bandwidth part (BWP); new channel coding methods such as low density parity check (LDPC) codes for large-volume data transmission and polar codes for highly reliable transmission of control information; layer 2 (L2) preprocessing; and network slicing for providing dedicated networks dedicated to specific services.

[0004] Currently, discussions are ongoing on improvements and performance enhancements of initial 5G mobile communication technologies in view of the services that 5G mobile communication technologies will support, and there is already physical layer standardization on technologies such as: vehicle-to-everything (V2X), for assisting driving determination of autonomous vehicles based on information about the positioning and status of the vehicle sent by the vehicle, and for enhancing user convenience; new radio unlicensed (NR-U), for system operation in compliance with various regulatory-related requirements in unlicensed bands; new radio user equipment (NR UE) energy saving; non-terrestrial network (NTN), i.e., UE-satellite direct communication for providing coverage in areas where communication with terrestrial networks is unavailable; and positioning.

[0005] In addition, standardization is already underway in the air interface architecture / protocol area on technologies such as: industrial internet of things (IIoT) for supporting new services through networking and convergence with other industries; integrated access and backhaul (IAB) for providing nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner; mobility enhancement, including conditional handover and dual active protocol stack (DAPS) handover; and two-step random access for simplifying the random access procedure (2-step RACH for NR). Standardization is also already underway in the system architecture / service area on the following: 5G baseline architecture (e.g., service-based architecture or service-based interface) for combining network functions virtualization (NFV) and software-defined networking (SDN) technologies; and mobile edge computing (MEC) for receiving services based on UE positioning.

[0006] With the commercialization of 5G mobile communication systems, the number of connected devices, which has been increasing exponentially, will be connected to the communication network, and accordingly, it is expected that enhanced functions and performance of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research related to the following items is planned: extended reality (XR) for efficiently supporting augmented reality (AR), virtual reality (VR), mixed reality (MR), etc.; improving 5G performance and reducing complexity by utilizing artificial intelligence (AI) and machine learning (ML); AI service support; metaverse service support; and drone communication.

[0007] Furthermore, such developments in 5G mobile communication systems will serve not only as a basis for developing new waveforms for providing coverage of the terahertz band for 6G mobile communication technology, multi-antenna transmission technologies (such as full dimensional MIMO (FD-MIMO), array antennas, and massive antennas), metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional spatial multiplexing technologies using orbital angular momentum (OAM), and reconfigurable intelligent surfaces (RIS), but also as a basis for developing full-duplex technologies for improving frequency efficiency and improving system networks for 6G mobile communication technology, AI-based communication technologies for implementing system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technologies for implementing services with a level of complexity that exceeds the limits of UE operating capabilities by utilizing ultra-high performance communication and computing resources.

[0008] The above information is presented as background information only to assist in understanding the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present disclosure. Summary of the invention

[0009] Solution to the problem

[0010] The present disclosure provides a method and apparatus for handling a listen-before-talk (LBT) failure in a wireless communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings, in which:

[0012] Figure 1 The architecture of a sidelink communication system according to an embodiment of the present disclosure is shown;

[0013] Figure 2 A flowchart describing a method performed by a user equipment (UE) according to an embodiment of the present disclosure is shown;

[0014] Figure 3 A diagram showing a UE 300 according to an embodiment of the present disclosure; and

[0015] Figure 4 A diagram of a base station 400 according to an embodiment of the present disclosure is shown.

[0016] Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. DETAILED DESCRIPTION

[0017] Aspects of the present disclosure seek to address at least the above-mentioned problems and / or disadvantages and provide at least the advantages described below. Accordingly, one aspect of the present disclosure provides both a method and an apparatus for efficiently providing a service in a wireless communication system.

[0018] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments.

[0019] According to one aspect of the present disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided. The method includes: receiving configuration information associated with sidelink (SL) listen-before-talk (LBT) failure recovery from a base station; identifying a counter value associated with SL LBT failure detection based on an SL LBT failure indication received from a lower layer; and triggering SL continuous LBT failure when the counter value is greater than or equal to a threshold.

[0020] According to another aspect of the present disclosure, a user equipment (UE) in a wireless communication system is provided. The UE includes: a transceiver; and at least one processor, the at least one processor is coupled to the transceiver and is configured to: receive configuration information associated with side link (SL) listen-before-talk (LBT) failure recovery from a base station via the transceiver; identify a counter value associated with SL LBT failure detection based on an SL LBT failure indication received from a lower layer; and trigger SL continuous LBT failure when the counter value is greater than or equal to a threshold.

[0021] Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure.

[0022] It may be helpful to set forth definitions of certain words and phrases used throughout this patent document: the terms "include" and "comprising" and their derivatives mean unlimited inclusion; the term "or" is inclusive, meaning "and / or"; the phrases "associated with" and "associated with" and their derivatives may mean including, included within, interconnected with, containing, contained within, connected to or connected with, coupled to or coupled with, communicable with, cooperating with, intertwined, juxtaposed, proximate to, bound to or bound with, having, having the property of, and the like; and the term "controller" means any device, system, or portion thereof that controls at least one operation, such device being implemented in hardware, firmware, or software, or some combination of at least two thereof. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.

[0023] In addition, the various functions described below may be implemented or supported by one or more computer programs, each of which is formed by a computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, programs, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation with a suitable computer-readable program code. The phrase "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as a read-only memory (ROM), a random access memory (RAM), a hard drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. "Non-transitory" computer-readable media do not include wired links, wireless links, optical links, or other communication links that transmit temporary electrical or other signals. Non-transitory computer-readable media include media in which data can be permanently stored and media in which data can be stored and overwritten later (such as rewritable optical disks or erasable memory devices).

[0024] Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

[0025] Discussed below Figures 1 to 4 The various embodiments used to describe the principles of the present disclosure in this patent document are only illustrated and should not be interpreted in any way as limiting the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented with any suitably arranged system or device.

[0026] Throughout the present disclosure, the expression "at least one of a, b, or c" indicates: only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof. Throughout the specification, a layer (or layer arrangement) may also be referred to as an entity. Hereinafter, the operating principle of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or configurations are not described in detail because they would obscure the present disclosure with unnecessary detail. The terms used in the specification are defined in consideration of the functions used in the present disclosure and may be changed according to the intention or common method of the user or operator. Accordingly, the definition of the terms is understood based on the overall description of the present specification.

[0027] For the same reason, some elements may be exaggerated, omitted or roughly shown in the drawings. Moreover, the size of each element does not exactly correspond to the actual size of each element. In each figure, the same or corresponding elements are presented with the same reference numerals.

[0028] By referring to the following detailed description of the embodiments and drawings of the present disclosure, the advantages and features of the present disclosure and the methods for achieving them can be more easily understood. However, the present disclosure can be embodied in many different forms and should not be interpreted as being limited to the embodiments set forth herein; more precisely, these embodiments of the present disclosure are provided so that the present disclosure will be thorough and complete, and the concept of the present disclosure will be fully conveyed to those of ordinary skill in the art. Therefore, the scope of the present disclosure is defined by the appended claims. Throughout the specification, similar reference numerals refer to similar elements. It will be understood that the blocks in the flowchart or the combination of flowcharts can be executed by computer program instructions. Because these computer program instructions can be loaded into a processor of a general-purpose computer, a special-purpose computer, or another programmable data processing device, the instructions executed by the processor of the computer or another programmable data processing device create units for performing the functions described in (multiple) flowchart blocks.

[0029] The computer program instructions may be stored in a computer-usable or computer-readable memory capable of directing a computer or another programmable data processing apparatus to implement functions in a specific manner, and thus the instructions stored in the computer-usable or computer-readable memory may also be capable of producing an article of manufacture containing instruction means for performing the functions described in the flowchart block(s). The computer program instructions may also be loaded into a computer or another programmable data processing apparatus, and thus the instructions for operating the computer or another programmable data processing apparatus by generating a computer-implemented process when a series of operations are performed in the computer or another programmable data processing apparatus may provide operations for performing the functions described in the flowchart block(s).

[0030] In addition, each block may represent a module, a fragment or a portion of code that includes one or more executable instructions for performing (multiple) specified logical functions. It should also be noted that in some alternative embodiments, the functions mentioned in the blocks may not occur in order. For example, two consecutive blocks may also be executed simultaneously or in reverse order, depending on the corresponding functions.

[0031] As used herein, the term "unit" means a software element or a hardware element, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), and performs a certain function. However, the term "unit" is not limited to software or hardware. A "unit" can be formed so as to be located in an addressable storage medium, or can be formed so as to operate one or more processors. Thus, for example, the term "unit" can include elements (e.g., software elements, object-oriented software elements, class elements, and task elements), processes, functions, attributes, programs, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, or variables.

[0032] The functions provided by the elements and "units" may be combined into a smaller number of elements and "units", or may be divided into additional elements and "units". Further, the elements and "units" may be embodied as reproducing one or more central processing units (CPUs) in a device or a secure multimedia card. Moreover, in an embodiment of the present disclosure, a "unit" may include at least one processor. In the following description of the present disclosure, well-known functions or configurations are not described in detail because they would obscure the present disclosure with unnecessary detail.

[0033] Hereinafter, for convenience of explanation, the present disclosure uses terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) standard. However, the present disclosure is not limited to these terms and names and may also be applied to systems complying with other standards.

[0034] In the present disclosure, for the convenience of explanation, an evolved node B (eNB) may be used interchangeably with a next-generation node B (gNB). That is, a base station (BS) described by an eNB may represent a gNB. In the following description, the term "base station" refers to an entity for allocating resources to a user equipment (UE), and may be used interchangeably with at least one of a gNode B, an eNode B, a node B, a base station (BS), a radio access unit, a base station controller (BSC), or a node on a network. The term "terminal" may be used interchangeably with a UE, a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system capable of performing a communication function. However, the present disclosure is not limited to the foregoing examples. Specifically, the present disclosure is applicable to the 3GPP New Radio (NR) (or 5th Generation (5G)) mobile communication standard. In the following description, for the convenience of explanation, the term eNB may be used interchangeably with the term gNB. That is, a base station interpreted as an eNB may also indicate a gNB. The term UE may also refer to mobile phones, NB-IoT devices, sensors and other wireless communication devices.

[0035] The present disclosure relates to wireless communication systems. In particular, the present disclosure relates to apparatus, methods and systems for determining a listen-before-talk category for sidelink communications on an unlicensed carrier.

[0036] The fifth generation (5G) mobile communication technology defines a wide frequency band so that high transmission rates and new services are possible, and can be implemented not only in the "below 6 GHz" band such as 3.5 GHz, but also in the "above 6 GHz" band called millimeter waves including 28 GHz and 39 GHz. In addition, in order to achieve a transmission rate fifty times faster than that of 5G mobile communication technology and an ultra-low latency one-tenth of that of 5G mobile communication technology, the implementation of the sixth generation (6G) mobile communication technology (called a super 5G system) in the terahertz band (e.g., 95 GHz to 3 THz band) has been considered.

[0037] In the early stages of 5G mobile communication technology development, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine type communications (mMTC), standardization is already underway on the following: beamforming and massive multiple-input multiple-output (MIMO) for mitigating radio wave path loss and increasing radio wave transmission distance in millimeter waves; support for basic parameter sets (e.g., operating multiple subcarrier spacings) for efficient utilization of millimeter wave resources and dynamic operation of time slot formats; initial access technology for supporting multi-beam transmission and broadband; definition and operation of bandwidth parts (BWPs); new channel coding methods such as low-density parity-check (LDPC) codes for large amounts of data transmission and polar codes for highly reliable transmission of control information; layer 2 (L2) preprocessing; and network slicing for providing dedicated networks dedicated to specific services.

[0038] Currently, discussions are ongoing on improvements and performance enhancements of initial 5G mobile communication technologies in view of the services that 5G mobile communication technologies will support, and there is already physical layer standardization on technologies such as: Vehicle-to-Everything (V2X), for assisting driving determination of autonomous vehicles based on information about the positioning and status of vehicles sent by the vehicles, and for enhancing user convenience; New Radio Unlicensed (NR-U), for system operation complying with various regulatory-related requirements in unlicensed bands; New Radio User Equipment (NR UE) energy saving; Non-Terrestrial Network (NTN), i.e., UE-satellite direct communication for providing coverage in areas where communication with terrestrial networks is unavailable; and positioning.

[0039] In addition, standardization is already underway in the air interface architecture / protocol area on technologies such as: Industrial Internet of Things (IIoT) for supporting new services through networking and convergence with other industries; Integrated Access and Backhaul (IAB) for providing nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner; Mobility Enhancement, including conditional handover and dual active stack (DAPS) handover; and Two-step Random Access for simplifying the random access procedure (2-step RACH for NR). Standardization is also already underway in the system architecture / service area on the following: 5G baseline architecture (e.g., service-based architecture or service-based interface) for combining network function virtualization (NFV) and software-defined networking (SDN) technologies; and Mobile Edge Computing (MEC) for receiving services based on UE positioning.

[0040] With the commercialization of 5G mobile communication systems, the already exponentially increasing number of connected devices will be connected to the communication network, and accordingly, it is expected that enhanced functionality and performance of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research related to the following items is planned: Extended Reality (XR) for efficient support of Augmented Reality (AR), Virtual Reality (VR), Hybrid Radio (MR), etc.; Improving 5G performance and reducing complexity by utilizing Artificial Intelligence (AI) and Machine Learning (ML); AI service support; Metaverse service support; and UAV communication.

[0041] Further, such developments in 5G mobile communication systems will serve not only as a basis for developing new waveforms for providing coverage of the terahertz band for 6G mobile communication technology, multi-antenna transmission technologies (such as full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas), metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional spatial multiplexing technologies using orbital angular momentum (OAM), and reconfigurable smart surfaces (RIS), but also as a basis for developing full-duplex technologies for improving frequency efficiency and improving system networks for 6G mobile communication technology, AI-based communication technologies for implementing system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technologies for implementing services with a level of complexity that exceeds the limits of UE operating capabilities by utilizing ultra-high performance communication and computing resources.

[0042] In recent years, several broadband wireless technologies have been developed to meet the growing number of broadband subscribers and to provide more and better applications and services. The second generation of wireless communication systems has been developed to provide voice services while ensuring the mobility of users. The third generation of wireless communication systems supports not only voice services but also data services. In recent years, the fourth generation of wireless communication systems has been developed to provide high-speed data services. However, at present, the fourth generation of wireless communication systems suffers from a lack of resources to meet the growing demand for high-speed data services. Accordingly, the fifth generation of wireless communication systems (also called next generation radio or NR) are being developed to meet the growing demand for high-speed data services that support ultra-reliability and low-latency applications.

[0043] The fifth generation wireless communication system supports not only lower frequency bands but also higher frequency (millimeter wave) bands (e.g., 10 GHz to 100 GHz bands) in order to achieve higher data rates. In order to mitigate the propagation loss of radio waves and increase the transmission distance, beamforming technologies involving massive multiple input multiple output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas and / or analog beamforming, massive antennas are being considered in the design of the fifth generation wireless communication system. In addition, the fifth generation wireless communication system is expected to address different use cases with completely different requirements in terms of data rate, latency, reliability, mobility, etc. However, it is expected that the design of the air interface of the fifth generation wireless communication system will be flexible enough to serve UEs with completely different capabilities, depending on the use cases and market segments that the UE serves for the end customers. Several example use cases that the fifth generation wireless communication system is expected to address are enhanced mobile broadband (eMBB), massive machine type communication (m-MTC), ultra-reliable low latency communication (URLL), etc. eMBB requirements (such as tens of Gbps data rates, low latency, high mobility, etc.) address the market segment representing traditional wireless broadband subscribers who need ubiquitous, always-on, and on-the-go Internet connectivity. m-MTC requirements (such as very high connection density, infrequent data transfers, very long battery life, low mobility address, etc.) address the market segment representing the Internet of Things (IoT) / Internet of Everything (IoE) that envisions the connectivity of billions of devices. URLL requirements (such as very low latency, very high reliability, and variable mobility, etc.) address the market segment representing industrial automation applications (vehicle-to-vehicle / vehicle-to-infrastructure communications that are envisioned as an enabler for autonomous vehicles).

[0044] In the fifth generation wireless communication system operating at a higher frequency band (millimeter wave), UE and gNB communicate with each other using beamforming. Beamforming technology is used to mitigate propagation path loss and increase propagation distance for communication at a higher frequency band. Beamforming uses a high-gain antenna to enhance transmission performance and reception performance. Beamforming can be classified into transmit (TX) beamforming performed at the transmitting end and receive (RX) beamforming performed at the receiving end. In general, TX beamforming increases directivity by allowing the area reached by propagation to be densely located in a specific direction using multiple antennas. In this case, the aggregation of multiple antennas can be referred to as an antenna array, and each antenna included in the array can be referred to as an array element. The antenna array can be configured in various forms, such as a linear array, a planar array, and the like. The use of TX beamforming results in an increase in the directivity of the signal, thereby increasing the propagation distance. In addition, since the signal is hardly transmitted in a direction other than the directional direction, the signal interference acting on the other receiving end is significantly reduced. The receiving end can perform beamforming on the RX signal by using an RX antenna array. RX beamforming increases the strength of the RX signal transmitted in a specific direction by allowing propagation to be concentrated in a specific direction, and excludes signals transmitted in directions other than the specific direction from the RX signal, thereby providing the effect of blocking interference signals. By using beamforming technology, the transmitter can make multiple transmit beam patterns in different directions. Each of these transmit beam patterns can also be referred to as a transmit (TX) beam. Wireless communication systems operating at high frequencies use multiple narrow TX beams to transmit signals in a cell because each narrow TX beam provides coverage for a portion of the cell. The narrower the TX beam, the higher the antenna gain, and therefore the greater the propagation distance of the signal transmitted using beamforming. The receiver can also make multiple receive (RX) beam patterns in different directions. Each of these receive patterns can also be referred to as a receive (RX) beam.

[0045] The fifth generation wireless communication system (NR) supports independent operation mode and dual connectivity (DC). In DC, a multi-Rx / Tx UE can be configured to utilize resources provided by two different nodes (or NBs) connected via a non-ideal backhaul. One node acts as a master node (MN) and the other node acts as a secondary node (SN). MN and SN are connected via a network interface, and at least MN is connected to the core network. NR also supports multi-RAT dual connectivity (MR-DC) operation, whereby a UE in RRC_CONNECTED is configured to utilize radio resources provided by two different schedulers, where the two different schedulers are located in two different nodes connected via a non-ideal backhaul and either provide E-UTRA (if the node is an ng-eNB) or provide NR access (if the node is a gNB). In NR, for a UE in RRC_CONNECTED and without CA / DC configured, there is only one serving cell, including the primary cell (PCell). For a UE in RRC_CONNECTED and configured with CA / DC, the term "serving cell" is used to refer to the set of cells including (multiple) special cells (SpCells) and all secondary cells (SCells). In NR, the term mastercell group (MCG) refers to a set of serving cells associated with a master node, including PCell and optionally one or more SCells. In NR, the term secondary cell group (SCG) refers to a set of serving cells associated with a secondary node, including a primary SCG cell (PSCell) and optionally one or more SCells. In NR, PCell refers to a serving cell in an MCG operating at the primary frequency, where the UE either performs an initial connection establishment procedure or initiates a connection reestablishment procedure. In NR, for a UE configured with CA, an SCell is a cell that provides additional radio resources on top of the SpCell. PSCell refers to a serving cell in an SCG where the UE performs random access when performing a synchronization reconfiguration procedure. For dual connectivity operation, the term SpCell refers to the PCell of the MCG or the PSCell of the SCG, otherwise the term SpCell refers to the PCell.

[0046] In the fifth generation wireless communication system, the physical downlink control channel (PDCCH) is used to schedule downlink (DL) transmission on the physical downlink shared channel (PDSCH) and uplink (UL) transmission on the physical uplink shared channel (PUSCH), wherein the downlink control information (DCI) on the PDCCH includes: downlink assignment, which at least includes the modulation and coding format, resource allocation and hybrid ARQ information related to the downlink shared channel (DL-SCH); uplink scheduling authorization, which at least includes the modulation and coding format, resource allocation and hybrid ARQ information related to the uplink shared channel (UL-SCH). In addition to scheduling, the PDCCH can also be used for: activation and deactivation of PUSCH transmissions configured by configuration grants; activation and deactivation of PDSCH semi-persistent transmissions; notification of the slot format to one or more UEs; notification of (multiple) physical resource blocks (PRBs) and (multiple) orthogonal frequency division multiplexing (OFDM) symbols to one or more UEs, where the UE can assume that there are no transmissions for the UE; transmission of transmit power control (TPC) commands for the physical uplink control channel (PUCCH) and PUSCH; transmission of one or more TPC commands for signaling route set (SRS) transmissions for one or more UEs; switching the active bandwidth part of the UE; and initiating a random access procedure. According to the corresponding search space configuration, the UE monitors the PDCCH candidate set in the configured monitoring opportunities in one or more configured control resource sets (CORESETs). A CORESET consists of a set of PRBs with a duration of 1 to 3 OFDM symbols. Resource units, resource element groups (REGs) and control channel elements (CCEs) are defined within a CORESET, where each CCE consists of a set of REGs.The control channel is formed by aggregation of CCEs. Different code rates for the control channel are achieved by aggregating different numbers of CCEs. Interleaved and non-interleaved CCE to REG mapping is supported in CORESET. Polarization coding is used for PDCCH. Each resource element group carrying PDCCH carries its own demodulation reference signal (DMRS). Quadrature phase shift keying (QPSK) modulation is used for PDCCH.

[0047] In the fifth generation wireless communication system, a list of search space configurations is signaled by the gNB for each configured BWP, where each search space configuration is uniquely identified by an identifier (ID). The identifier of the search space configuration used for a specific purpose (such as paging reception, self-interference (SI) reception, and random access response reception) is explicitly signaled by the gNB. In NR, the search space configuration includes parameters such as Monitoring-periodicity-PDCCH-slot, Monitoring-offset-PDCCH-slot, Monitoring-symbols-PDCCH-within-slot, and duration. The UE uses these parameters to determine the PDCCH monitoring occasion(s) within a slot: PDCCH monitoring period (Monitoring-periodicity-PDCCH-slot), PDCCH monitoring offset (Monitoring-offset-PDCCH-slot), and PDCCH monitoring pattern (Monitoring-symbols-PDCCH-within-slot). The PDCCH monitoring occasions are in slots "x" to "x+duration", where the slot with number "x" in the radio frame with number "y" satisfies the following equation:

[0048] (y (number of slots in a radio frame) + x - Monitoring-offset-PDCCH-slot) mod (Monitoring-periodicity-PDCCH-slot) = 0;

[0049] The starting symbol of the PDCCH monitoring opportunity in each slot with a PDCCH monitoring opportunity is given by Monitoring-symbols-PDCCH-within-slot. The length of the PDCCH monitoring opportunity (in symbols) is given in the CORESET associated with the search space. The search space configuration includes an identifier of the CORESET configuration associated with it. A list of CORESET configurations is signaled by the gNB for each configuration BWP, where each CORESET configuration is uniquely identified by an identifier. Note that each radio frame is of 10ms duration. A radio frame is identified by a radio frame number or a system frame number. Each radio frame consists of several slots, where the number of slots in a radio frame and the slot duration depends on the subcarrier spacing (SCS). The number of slots in a radio frame and the slot duration are predefined in the NR for each supported SCS. Each CORESET configuration is associated with a list of transmission configuration indicator (TCI) states. A DL reference signal (RS) ID (single sideband (SSB) or channel state information reference signal (CSI RS)) is configured per TCI state. The TCI state list corresponding to the CORESET configuration is signaled by the gNB via radio resource control (RRC) signaling. One TCI state in the TCI state list is activated and indicated to the UE by the gNB. The TCI state indicates the DL TX beam used by the gNB for PDCCH transmission in the PDCCH monitoring occasions of the search space (the DL TX beam is quasi co-located with the SSB / CSI RS of the TCI state).

[0050] In the fifth generation wireless communication system, bandwidth adaptation (BA) is supported. In the case of BA, the reception bandwidth and transmission bandwidth of the UE do not need to be as large as the bandwidth of the cell and can be adjusted. For example, the width can be ordered to change (for example, to shrink during low activity periods to save power); the position can be moved in the frequency domain (for example, to increase scheduling flexibility); and the subcarrier spacing can be ordered to change (for example, to allow different services). A subset of the total cell bandwidth of a cell is called a bandwidth part (BWP). BA is achieved by configuring (multiple) BWPs for RRC-connected UEs and telling the UE which configured BWP is currently the active BWP. When BA is configured, the UE only needs to monitor the PDCCH on one active BWP (ie, it does not have to monitor the PDCCH on the entire DL frequency of the serving cell). In the RRC connected state, for each configured serving cell (ie, PCell or SCell), the UE is configured with one or more DL BWPs and UL BWPs. For an activated serving cell, there is always one active UL BWP and DL BWP at any point in time. BWP switching for the serving cell is used to activate the inactive BWP and deactivate the active BWP at a specific time. BWP switching is controlled by the PDCCH indicating the downlink assignment or uplink grant, by the bwp-InactivityTimer, by RRC signaling, or by the MAC entity itself when initiating the random access procedure. When adding a SpCell or activating an SCell, the DL BWP and UL BWP indicated by firstActiveDownlinkBWP-Id and firstActiveUplinkBWP-Id, respectively, are active without receiving a PDCCH indicating a downlink assignment or uplink grant. The active BWP for the serving cell is indicated by RRC or PDCCH. For unpaired spectrum, the DL BWP is paired with the UL BWP, and the BWP switching is common to both UL and DL. When the BWP inactivity timer expires, the UE can switch to the active DL BWP, the default DL BWP, or the initial DLBWP (if the default DL BWP is not configured).

[0051] 4G and 5G wireless communication systems support vehicle communication services. Vehicle communication services, represented by V2X services, can consist of four different types: V2V, V2I, V2N, and V2P. In the fifth generation (also known as NR or New Radio) wireless communication system, V2X communication is being enhanced to support enhanced V2X use cases, where enhanced V2X use cases are roughly arranged into four use case groups:

[0052] Vehicle platooning enables vehicles to dynamically form a convoy traveling together. All vehicles in the convoy receive information from the lead vehicle to manage the convoy. This information allows vehicles to drive closer than normal in a coordinated manner, heading in the same direction and traveling together.

[0053] Extended sensors enable the exchange of raw or processed data or real-time video images collected by local sensors between vehicles, roadside units, pedestrian devices and V2X application servers. Vehicles can increase their perception of their environment beyond what their own sensors can detect and have a wider and more comprehensive view of the local situation. High data rate is one of the key features.

[0054] Advanced driving enables semi-autonomous or fully autonomous driving. Each vehicle and / or road side unit (RSU) shares its own perception data obtained from its local sensors with nearby vehicles, and this allows the vehicles to synchronize and coordinate their trajectories or maneuvers. Each vehicle also shares its driving intentions with nearby vehicles.

[0055] Remote driving enables remote drivers or V2X applications to operate a remote vehicle for passengers who cannot drive themselves, or to operate a remote vehicle in a hazardous environment. For situations where changes are limited and routes are predictable, such as public transportation, cloud-based driving can be used. High reliability and low latency are the main requirements.

[0056] Figure 1 The architecture of the sidelink communication system is shown.

[0057] V2X services may be provided over the PC5 interface and / or the Uu interface. Support for V2X services via the PC5 interface is provided by NR sidelink communication or V2X sidelink communication, where NR sidelink communication or V2X sidelink communication is a communication mode whereby UEs may communicate with each other directly over the PC5 interface using NR technology or E-UTRA technology, respectively, without traversing any network node. This communication mode is supported when the UE is served by a radio access network (RAN) and when the UE is outside of RAN coverage. Only UEs authorized for V2X services may perform NR or V2X sidelink communications. The next generation radio access network (NG-RAN) architecture supports the PC5 interface, such as Figure 1 As shown. When the UE is within NG-RAN coverage (regardless of the RRC state of the UE) and when the UE is outside NG-RAN coverage, sidelink transmission and reception over the PC5 interface are supported. Support for V2X services via the PC5 interface can be provided by NR sidelink communications and / or V2X sidelink communications. NR sidelink communications can be used to support services other than V2X services.

[0058] NR or V2X sidelink communication can support three types of transmission modes. The first type can be unicast transmission, characterized by: supporting at least one PC5-RRC connection between peer UEs; sending and receiving control information and user traffic between peer UEs in the side link; supporting sidelink hybrid automatic repeat request (HARQ) feedback; supporting radio link control acknowledge mode (RLC AM); and supporting sidelink radio link monitoring (RLM) for two peer UEs to detect radio link failure (RLF). The second type can be multicast transmission, characterized by: sending and receiving user traffic between UEs belonging to a group in the side link; and supporting HARQ feedback. The third type can be broadcast transmission, characterized by sending and receiving user traffic between UEs in the side link.

[0059] The AS protocol stack for the control plane in the PC5 interface consists of the RRC sublayer, the packet data convergence protocol (PDCP) sublayer, the RLC sublayer, the media access control (MAC) sublayer, and the physical layer. The AS protocol stack for the user plane in the PC5 interface consists of the service data adaptation protocol (SDAP) sublayer, the PDCP sublayer, the RLC sublayer, the MAC sublayer, and the physical layer. Sidelink radio bearers (SLRBs) are classified into two groups: sidelink data radio bearers (SL DRBs) for user plane data and sidelink signaling radio bearers (SL SRBs) for control plane data. Separate SL SRBs using different sidelink control channels (SCCHs) are configured for PC5-RRC signaling and PC5-S signaling, respectively.

[0060] The MAC sublayer provides the following services and functions through the PC5 interface: radio resource selection; packet filtering; priority handling between uplink transmissions and sidelink transmissions for a given UE; and sidelink CSI reporting. Due to the link control protocol (LCP) constraints in the MAC, for each unicast transmission, multicast transmission, and broadcast transmission associated with a destination, only the sidelink logical channels belonging to the same destination can be multiplexed into the MAC protocol data unit (PDU). NG-RAN can also control whether the sidelink logical channels can utilize the resources allocated to the configured sidelink grant type 1. For packet filtering, a sidelink shared channel (SL-SCH) MAC header including two parts, the source layer 2 ID and the destination layer 2 ID, is added to each MAC PDU. The logical channel identifier (LCID) included in the MAC subheader uniquely identifies a logical channel within the combined range of the source layer 2 ID and the destination layer 2 ID. The following logical channels are used in the sidelink:

[0061] Sidelink Control Channel (SCCH): A sidelink channel used to send control information from one UE to (multiple) other UEs;

[0062] Sidelink traffic channel (STCH): a sidelink channel used to send user information from one UE to (multiple) other UEs; and

[0063] Sidelink broadcast control channel (SBCCH): A sidelink channel used to broadcast sidelink system information from one UE to (multiple) other UEs.

[0064] The following connections exist between logical channels and transport channels:

[0065] SCCH can be mapped to SL-SCH;

[0066] STCH may be mapped to SL-SCH; and

[0067] SBCCH can be mapped to the sidelink broadcast channel (SL-BCH).

[0068] Sidelink operation involves the following physical layer channels and signals:

[0069] The physical sidelink control channel (PSCCH) indicates the resources and other transmission parameters used by the UE for PSSCH. PSCCH transmission is associated with DM-RS.

[0070] The physical sidelink shared channel (PSSCH) transmits the TB of the data itself as well as control information for HARQ procedures and CSI feedback triggers. At least 6 OFDM symbols in a time slot are used for PSSCH transmission. PSSCH transmission is associated with DM-RS and can be associated with a phase tracking reference signal (PT-RS).

[0071] The physical sidelink feedback channel (PSFCH) carries HARQ feedback over the sidelink from the UE that is the intended recipient of the PSSCH transmission to the UE performing the transmission. The PSFCH sequence is sent in one PRB repeated over two OFDM symbols near the end of the sidelink resource in a slot.

[0072] The sidelink synchronization signal consists of the sidelink primary synchronization signal (S-PSS) and the sidelink secondary synchronization signal (S-SSS), where S-PSS and S-SSS each occupy 2 symbols and 127 subcarriers. For the normal cyclic prefix (CP) case and the extended CP case, the physical sidelink broadcast channel (PSBCH) occupies 9 symbols and 5 symbols respectively, including the associated DM-RS.

[0073] For unicast, Channel State Information Reference Signal (CSI-RS) is supported for CSI measurement and reporting in the sidelink. The CSI report is carried in the sidelink MAC CE.

[0074] The RRC sublayer provides the following services and functions through the PC5 interface:

[0075] Transmission of PC5-RRC messages between peer UEs;

[0076] Maintenance and release of a PC5-RRC connection between two UEs; and

[0077] Detection of sidelink radio link failure for PC5-RRC connection.

[0078] A PC5-RRC connection is a logical connection between two UEs for a pair of source Layer 2 ID and destination Layer 2 ID, which is considered to be established after the corresponding PC5 unicast link is established, as specified by TS 23.287. There is a one-to-one correspondence between PC5-RRC connections and PC5 unicast links. A UE may have multiple PC5-RRC connections with one or more UEs for different multiple pairs of source Layer 2 ID and destination Layer 2 ID. Separate PC5-RRC procedures and messages are used for the UE to communicate UE capabilities and sidelink configuration including SLRB configuration to a peer UE. Both peer UEs may exchange their own UE capabilities and sidelink configuration in both sidelink directions using separate bidirectional procedures. The UE releases the PC5-RRC connection if it is not interested in sidelink transmission, if the sidelink RLF on the PC5-RRC connection is declared, or if the Layer 2 link release procedure is completed, as specified by TS 23.287.

[0079] For resource allocation in the sidelink, the UE can operate in two modes:

[0080] The scheduled resource allocation is characterized by:

[0081] The UE needs to be in RRC_CONNECTED in order to send data; and

[0082] NG-RAN schedules transmission resources.

[0083] UE autonomous resource selection, characterized by:

[0084] The UE may send data when within NG-RAN coverage (regardless of the UE’s RRC state) and when outside NG-RAN coverage; and

[0085] The UE autonomously selects transmission resources from the resource pool.

[0086] For NR sidelink communications, the UE performs sidelink transmissions on a single carrier only.

[0087] Scheduled resource allocation : The NG-RAN can dynamically allocate resources for NR sidelink communications to the UE via the sidelink radio network temporary identifier (SL-RNTI) on (multiple) PDCCHs. In addition, the NG-RAN can allocate sidelink resources to the UE using two types of configured sidelink grants:

[0088] In case of Type 1, RRC directly provides the configuration sidelink grant for NR sidelink communication.

[0089] In the case of type 2, RRC provides the periodicity of the configured sidelink grant, while PDCCH can signal and activate the configured sidelink grant, or deactivate the configured sidelink grant. PDCCH provides the actual grant to be used (i.e., resources). PDCCH is addressed to the sidelink configured scheduling radio network temporary identifier (SL-CS-RNTI) for NR sidelink communication and the SL semi-persistent scheduling vehicle radio network temporary identifier (V-RNTI) for V2X sidelink communication.

[0090] For UEs performing NR sidelink communications, more than one configured sidelink grant may be active at a time on a carrier configured for sidelink transmission. When beam failure or physical layer issues occur on the NR Uu, the UE may continue to use configured sidelink grant type 1. During handover, a configured sidelink grant may be provided to the UE via the handover command, regardless of the type. If provided, the UE activates configured sidelink grant type 1 upon receipt of the handover command. The UE may send a sidelink buffer status report to support scheduler operations in the NG-RAN. The sidelink buffer status report refers to the data buffered in the UE for each destination for a logical channel group (LCG). Eight LCGs are used to report the sidelink buffer status report. Two formats are used: sidelink buffer status report (SL BSR) and truncated SL BSR.

[0091] UE autonomous resource allocation : The UE autonomously selects the sidelink grant from a resource pool provided by broadcast system information or dedicated signaling when within NG-RAN coverage, or from a resource pool provided by pre-configuration when outside NG-RAN coverage.

[0092] For NR sidelink communications, a resource pool may be provided for a given validity region, and the UE does not need to acquire a new resource pool while moving within the validity region (e.g., reusing the validity region of the NR SIB), at least when the new resource pool is provided by a system information block (SIB). Reuse the NR SIB validity mechanism to enable validity regions for SL resource pools configured via broadcast system information. Allow the UE to temporarily use UE autonomous resource selection with random selection for sidelink transmissions based on the configuration of an exception transmission resource pool.

[0093] For V2X sidelink transmission, during handover, the transmission resource pool configuration including the exception transmission resource pool for the target cell can be signaled in the handover command to reduce transmission interruption. In this way, the UE can use the V2X sidelink transmission resource pool of the target cell before the handover is completed, as long as synchronization is performed with the target cell if the eNB is configured as the synchronization source, or synchronization is performed with the global navigation satellite system (GNSS) if the GNSS is configured as the synchronization source. If the exception transmission resource pool is included in the handover command, the UE uses resources randomly selected from the exception transmission resource pool from the receipt of the handover command. If scheduled resource allocation is configured for the UE in the handover command, the UE continues to use the exception transmission resource pool while the timer associated with the handover is running. If autonomous resource selection is configured for the UE in the target cell, the UE continues to use the exception transmission resource pool until sensing results are available regarding the transmission resource pool for autonomous resource selection. For exceptional cases (e.g., during RLF, during transition from RRC IDLE to RRC CONNECTED, or during change of dedicated V2X sidelink resource pool within a cell), the UE may select resources from the exceptional pool provided in the SIB21 or dedicated signaling of the serving cell based on random selection and use them temporarily. During cell reselection, an RRC_IDLE UE may use resources randomly selected from the exceptional transmission resource pool of the reselected cell until sensing results regarding the transmission resource pool for autonomous resource selection are available.

[0094] The design of 5G wireless sidelink communication systems needs to support operation on (multiple) licensed carriers as well as unlicensed carriers. Listen before talk (LBT) procedures are critical for fair and friendly coexistence of devices and technologies operating in unlicensed spectrum. The LBT procedure performed by a UE attempting to transmit on a sidelink carrier in the unlicensed spectrum requires the UE to perform a clear channel assessment to determine whether the channel is free for use. The various types or categories of LBT procedures for sidelink transmissions are as follows:

[0095] Type 1: LBT with random backoff with contention window : During the extension duration T d After sensing the channel idle for the first time during the time slot duration of , and after the counter N is zero in step 4 below, the UE may send a transmission using a Type 1 channel access procedure. The counter N is adjusted by sensing the channel for additional time slot durations according to the steps described below.

[0096] Let N = N init , where N init is evenly distributed between 0 and Cw p A random number between , and go to step 4;

[0097] If N>0 and the UE chooses to decrement the counter, then set N=N-1;

[0098] Sensing the channel during the additional time slot duration, and if the additional time slot duration is idle, go to step 4; otherwise, go to step 5;

[0099] If N=0, stop; otherwise, go to step 2;

[0100] The sensing channel is not detected until an additional delay of duration T d A busy slot is detected within 1 second, or until an additional delay duration T is detected d All time slots of are free;

[0101] If the additional extension duration T d If the channel is sensed to be idle during all time slot durations, go to step 4; otherwise, go to step 5.

[0102] If after step 4 in the above procedure, the UE has not yet sent an UL transmission on the channel on which the UL transmission(s) are performed, then if at least the sensing slot duration T is reached when the UE is ready to send a transmission sl The channel is sensed to be idle in the delay time T immediately before the transmission. dIf the UE senses that the channel is idle during all time slot durations of T, the UE may send a transmission on the channel. If the UE senses that the channel is idle during all time slot durations of T when it is ready to transmit for the first time, the UE may send a transmission on the channel. sl or if the channel is not idle during the delay duration T immediately preceding the expected transmission. d If the channel is idle during any sensing time slot duration, then the delay duration T d After sensing that the channel is idle during the time slot duration of , the UE proceeds to step 1.

[0103] Delay duration T d Immediately followed by The duration of consecutive time slots The duration of each time slot is ,and exist Initially includes the idle slot duration .

[0104] is the competition window. Before step 1 of the above procedure, select and .

[0105] , and The channel access priority classes are based on the following Table 1 of.

[0106] Table 1

[0107]

[0108] Type 2A: LBT without random backoff : The UE may sense that the channel is idle for at least the sensing interval The transmission is sent immediately afterwards. The duration of the next sensing slot Composition, and exist The start includes a sensing time slot. If the If both sensing time slots are idle, the channel is considered idle. .

[0109] Type 2B : The UE can The transmission is sent immediately after the internal sensing detects that the channel is idle. Including those occurring in The End If the channel is idle for at least , of which at least The sensing occurs in the sensing time slot, then the channel is considered to be in duration The inside is free.

[0110] Type 2C: No LBT : The UE does not sense the channel before transmission. The corresponding UL transmission duration is at most .

[0111] The problem is that sidelink communication or discovery may be interrupted in the case where the UE cannot transmit due to LBT at several occasions. A method is needed to recover from these failures. Note that sidelink communication or discovery can be used for various use cases, such as for public safety, V2X, etc.

[0112] Figure 2 A flow chart describing a method performed by a user equipment (UE) according to an embodiment of the present disclosure is shown.

[0113] In step 201, a UE performing sidelink communication or discovery on a carrier in an unlicensed spectrum may be configured with a sidelink LBT failure recovery configuration. The configuration includes sL-lbt-FailureInstanceMaxCount for persistent sidelink LBT failure detection and sL-lbt-FailureDetectionTimer for persistent sidelink LBT failure detection. The sidelink LBT failure recovery configuration may be configured per SL BWP, or per SL carrier, or per SL resource pool, where a SL resource pool may also be referred to as a sidelink resource set or a sidelink resource block set. Note that a UE may be configured with one or more carriers for sidelink communication. The sidelink LBT failure recovery configuration may be signaled via an RRCReconfiguration message or a system information block (SIB), or in a SL pre-configuration, or in an RRC message, or in any other signaling sent by a peer UE. Note that the signaling of the sidelink LBT failure configuration by the gNB to the UE for sidelink communication is different from the signaling of the LBT failure configuration by the gNB to the UE for uplink communication toward the gNB.

[0114] In step 203, in the lower layer (ie, PHY layer), if the carrier used for sidelink communication or discovery is an unlicensed carrier, the UE performs a SL LBT procedure before SL transmission on the carrier.

[0115] In step 205, if the sidelink LBT failure recovery configuration is configured for the carrier, or the SL BWP for the carrier, or the SL resource pool / resource set / resource block set used for transmission, then when the lower layer performs the LBT procedure before the sidelink transmission and no sidelink transmission is performed (because the channel is not idle), a sidelink LBT failure indication is sent from the lower layer to the MAC entity. Note that this indication is different from the indication sent to the MAC layer when the UE detects an uplink LBT failure for an uplink transmission to the gNB. The lower layer indicates whether the LBT failure indication is for the uplink or for the sidelink. The MAC entity applies different procedures for the persistent LBT failure detection and recovery procedures for the sidelink and uplink (such as different LBT counters, different counter maximum values, different detection timer values, different indications from the lower layer, different actions upon persistent failure detection, etc.).

[0116] In step 207, the MAC entity in the UE may be configured with a persistent sidelink LBT failure recovery procedure. If the sidelink LBT failure recovery configuration is configured, the MAC entity performs a persistent sidelink LBT failure recovery procedure. Persistent sidelink LBT failures are detected per SL BWP, per SL carrier, or per SL resource pool / resource set / resource block set by counting the sidelink LBT failure indications received from the lower layer.

[0117] In an embodiment, a single counter is maintained per SL carrier, or per SL BWP, or per SL resource pool / resource set / resource block set, and counting is performed for all SL transmissions, which means that the lower layer sends a side link LBT failure indication regardless of the type of transmission in which the LBT failure is detected (PSSCH or PSCCH or PSFCH or PSBCH or S-PSS or S-SSS).

[0118] In an embodiment, a single counter is maintained per SL carrier, or per SL BWP, or per SL resource pool / resource set / resource block set, and counting is performed for SL transmissions associated with PSSCH, which means that when LBT failure is detected for transmissions associated with PSSCH, the lower layer sends a side link LBT failure indication. For SL transmissions on other SL channels, the lower layer does not send an LBT failure indication to the MAC entity.

[0119] In an embodiment, a single counter is maintained per SL carrier, or per SL BWP, or per SL resource pool / resource set / resource block set, and counting is performed for SL transmissions related to PSSCH and PSCCH, which means that when LBT failure is detected for transmissions related to PSSCH and PSCCH, the lower layer sends a side link LBT failure indication. For SL transmissions on other SL channels, the lower layer does not send an LBT failure indication to the MAC entity.

[0120] In an embodiment, a single counter is maintained per SL carrier, or SL BWP, or SL resource pool / resource set / resource block set, and counting is performed for SL transmissions associated with PSSCH, PSCCH, and PSFCH, which means that when LBT failure is detected for transmissions associated with PSSCH, PSCCH, and PSFCH, the lower layer sends a side link LBT failure indication. For SL transmissions on other SL channels, the lower layer does not send an LBT failure indication to the MAC entity.

[0121] In an embodiment, persistent sidelink LBT failure may be detected only for transmissions performed using scheduled resource allocations (or Mode 1).

[0122] In step 209, when the counter (SL_LBT_COUNTER) is greater than or equal to sL-lbt-FailureInstanceMaxCount, the MAC entity in the UE may trigger a persistent sidelink LBT failure for a SL BWP or SL carrier or SL resource pool / resource set / resource block set.

[0123] In step 211, the MAC entity in the UE may initiate a persistent sidelink LBT failure recovery procedure.

[0124] Continuous side link LBT failure detection : For a SL carrier or SLBWP or SL resource pool / resource set / resource block set configured with sidelink LBT failure recovery configuration, the MAC entity in the UE shall:

[0125] 1> If a sidelink LBT failure indication has been received from the lower layer:

[0126] 2> Start or restart sL-lbt-FailureDetectionTimer;

[0127] 2>Increment SL_LBT_COUNTER by 1;

[0128] 2> if SL_LBT_COUNTER >= sL-lbt-FailureInstanceMaxCount:

[0129] 3> Trigger persistent sidelink LBT failure for SL BWP or SL carrier or SL resource pool / resource set / resource block set.

[0130] Note that SL_LBT_COUNTER is maintained per carrier, or per SL BWP, or per SL resource pool / resource set / resource block set. In an embodiment, a persistent sidelink LBT failure for a SL BWP or SL carrier or SL resource pool / resource set / resource block set may be detected separately for each channel (PSSCH or PSCCH or PSFCH or PSBCH or S-PSS or S-SSS), and in this case, SL_LBT_COUNTER and sL-lbt-FailureDetectionTimer are maintained separately for each channel, and an LBT failure indication is sent separately for each channel by the lower layer. In an embodiment, persistent sidelink LBT failure for SL BWP or SL carrier or SL resource pool / resource set / resource block set can be detected separately for a first group of channels consisting of PSSCH / PSCCH / PSFCH and a second group of channels consisting of PSBCH / S-PSS / S-SSS, and in this case, SL_LBT_COUNTER and sL-lbt-FailureDetectionTimer are maintained separately for the first group of channels and the second group of channels, and LBT failure indication is sent separately by the lower layer for each group.

[0131] Reset SL_LBT_COUNTER :

[0132] 1 >If all triggered persistent SL LBT failures are cancelled; or

[0133] 1 >If sL-lbt-FailureDetectionTimer expires; or

[0134] 1> If sL-lbt-FailureDetectionTimer or sL-lbt-FailureInstanceMaxCount is reconfigured by the upper layer:

[0135] 2 > Set SL_LBT_COUNTER to 0.

[0136] When a persistent sidelink LBT failure is detected on a SL BWP or SL carrier or SL resource pool / resource set / resource block set, the UE may perform the following operations:

[0137] Option 1: The UE may send an RRC message to the gNB indicating a persistent sidelink LBT failure. The UE may additionally indicate to the gNB information about the SL carrier(s) and / or SL BWPID(s) and / or SL resource pool / resource set / resource block set index(es) on which the persistent sidelink LBT failure was detected. In an embodiment, the UE may perform this operation when the UE is in RRC_CONNECTED state. In an embodiment, the UE may send an RRC message indicating a persistent sidelink LBT failure in Msg3 or MsgA using a random access procedure when the UE is in RRC_IDLE or RRC_INACTIVE state.

[0138] Option 2 : The UE may send a SL LBT Failure MAC CE to the gNB. In the MAC CE, the UE may indicate the SL carrier(s) and / or SL BWP ID(s) and / or SL resource pool / resource set / resource block set index(es) of the resource pool / resource set / resource block set on which the persistent sidelink LBT failure is detected. In an embodiment, the UE may perform this operation when the UE is in RRC_CONNECTED state.

[0139] Scheduling request may be supported for reporting persistent sidelink LBT failure detection to the gNB. Scheduling request resources for SL LBT failure may be indicated via the RRCReconfiguration message. If UL-SCH resources are available for new transmission and as a result of logical channel prioritization, these UL-SCH resources can accommodate the SL LBT failure MAC CE plus its subheader, the MAC entity may indicate the multiplexing and assembly procedure to generate the SL LBT failure MAC CE. Otherwise, the MAC entity may trigger a scheduling request for the SL LBT failure MAC CE.

[0140] In response to the SL LBT failure indication according to Option 1 and Option 2, the network may configure / change the SL BWP or SL carrier or SL resource pool / resource set / resource block set.

[0141] In an embodiment, in both Option 1 and Option 2, the UE may be configured with a fallback carrier for sidelink communications (e.g., on a licensed spectrum or an unlicensed spectrum). When a persistent sidelink LBT failure is detected in an unlicensed sidelink carrier, the UE may switch to that carrier. The fallback carrier and the sidelink configuration on that carrier may be signaled via an RRCReconfiguration message or a System Information Block (SIB), or in a SL pre-configuration, or in an RRC message, or in any other signaling sent by a peer UE. In an embodiment, the switch may be performed upon receipt of an indication from the gNB in ​​response to a persistent sidelink LBT failure sent by the UE.

[0142] In an embodiment, Option 1 and Option 2 may only be applied to persistent sidelink LBT failures detected for transmissions performed using scheduled resource allocations (or Mode 1). In other words, Option 1 and Option 2 may be applied if the UE is performing sidelink communications using scheduled resource allocations (or Mode 1) (on the SL BWP or SL carrier or SL resource pool / resource set / resource block set where the persistent sidelink LBT failure was detected).

[0143] Option 3 : The UE deactivates the SL BWP or SL carrier or SL resource pool / resource set / resource block set for a specified duration (a timer may be started upon detection of a persistent sidelink LBT failure; the UE does not use the SL BWP or SL carrier or SL resource pool / resource set / resource block set for which the persistent sidelink LBT failure was detected, and upon expiration of the timer, the UE may start using the SL BWP or SL carrier or SL resource pool / resource set / resource block set for which the persistent sidelink LBT failure was detected again). The timer duration may be signaled by the gNB in ​​an SIB or RRC message or SL pre-configuration. In an embodiment, the UE may be configured with a fallback carrier (e.g., on a licensed spectrum or an unlicensed spectrum) or a fallback SL BWP or a fallback SL resource pool / resource set / resource block set for sidelink communication. When a persistent sidelink LBT failure is detected in an unlicensed sidelink carrier, the UE may switch to that fallback carrier or fallback SL BWP or fallback SL resource pool / resource set / resource block set and use it for sidelink communication while the timer is running.

[0144] Option 4: The UE may declare SL RLF and initiate the SL RLF procedure. SL RLF is declared for all destinations with which the UE is communicating using the carrier or SL BWP or SL resource pool / resource set / resource block set where the persistent sidelink LBT failure was detected. The UE may: release the DRBs, SRBs, PC5 relay RLC channels for these destinations; discard the NR sidelink communication related configuration for these destinations; reset the sidelink specific MAC for these destinations; consider releasing the PC5-RRC connection for these destinations; and indicate the release of the PC5-RRC connection to the upper layer for these destinations (i.e., PC5 is unavailable).

[0145] Option 5 : The UE may send an RRC message to a peer UE indicating a persistent sidelink LBT failure. The UE may additionally indicate to the peer UE information about the SL carrier(s) and / or SLBWP ID(s) and / or SL resource pool / resource set / resource block set index(es) on which the persistent sidelink LBT failure was detected.

[0146] Option 6 : The UE may send a SL LBT Failure MAC CE to the peer UE. In the MAC CE, the UE may indicate the SL carrier(s) and / or SL BWP ID(s) and / or SL resource pool / resource set / resource block set index(es) of the resource pool / resource set / resource block set on which the persistent sidelink LBT failure was detected.

[0147] Option 7 : If a persistent sidelink LBT failure is detected for a resource pool / resource set / resource block set, the UE may stop using the resource pool / resource set / resource block set for the timer duration as in option 3 above. The UE may then start using another SL resource pool / resource set / resource block set for which a persistent LBT failure has not been detected. If a sidelink LBT failure is detected for all SL resource pools / resource sets / resource block sets of the SL BWP of the SL carrier, the UE may notify the gNB as in options 1 and 2. If a sidelink LBT failure is detected for all SL resource pools / resource sets / resource block sets of the SL BWP of the SL carrier, the UE may switch to another SL BWP for which a persistent LBT failure has not been detected (if available). If another SL BWP is not available or a persistent LBT failure is detected for all configured SL BWPs, the UE may switch to another carrier or the UE may notify the gNB as in options 1 and 2.

[0148] Option 8: If a persistent sidelink LBT failure is detected for a SL BWP and multiple SLBWPs are configured for the SL carrier, the UE may switch to another SL BWP where no persistent LBT failure is detected. If a sidelink LBT failure is detected for all SLBWPs of the SL carrier, the UE may switch to another SL carrier or the UE may notify the gNB as in Option 1 and Option 2.

[0149] Option 9 : The UE can release the SL connection.

[0150] Option 10 : A UE in RRC_IDLE state and RRC_INACTIVE state can trigger cell reselection.

[0151] In Option 2 above, the MAC entity may perform the cancellation of the triggered persistent SL LBT failure(s) as follows:

[0152] 1> If a MAC PDU is sent and no LBT failure indication is received from the lower layers, and the PDU includes a SL LBT failure MAC CE:

[0153] 2> Cancel all(s) triggered persistent SL LBT failures which indicated persistent SL LBT failure in the sent SL LBT failure MAC CE.

[0154] 1> If sL-lbt-FailureRecoveryConfig is reconfigured by the upper layer for SL BWP or SL carrier:

[0155] 2> Continuous SL LBT failure to cancel all(multiple) triggers for SL BWP or SL carrier.

[0156] In Option 2 above, the MAC entity may perform RA cancellation based on SL LBT failure as follows: The MAC entity may stop the ongoing random access procedure (if any) due to a pending SR for persistent sidelink LBT failure recovery, where the pending SR is not configured with valid PUCCH resources, if the following is the case:

[0157] The MAC PDU is sent using an UL grant other than the UL grant provided by the random access response or the UL grant determined as specified in 3GPP clause 5.1.2a for transmission of MSGA payload. The PDU includes a SL LBT Failure MAC CE indicating a persistent SL LBT failure or carrier triggered persistent SL LBT failure for SL BWP.

[0158] In Option 2 above, the MAC entity may perform SR cancellation based on SL LBT failure as follows:

[0159] 1> if the SR is triggered by persistent SL LBT failure recovery and a MAC PDU is sent and the MAC PDU includes a SL LBT failure MAC CE indicating persistent SL LBT failure for the SL BWP or SL carrier; or

[0160] 1> If the SR is triggered by a persistent SL LBT failure recovery, and all (multiple) triggered persistent SL LBT failures are canceled:

[0161] 2>Cancel the pending SR and stop the corresponding sr-ProhibitTimer (if it is running).

[0162] In an embodiment, when the MAC is reset, the MAC entity in the UE stops the sL-lbt-FailureDetectionTimer and sets the SL_LBT_COUNTER to 0.

[0163] In Option 2 above, the MAC CE for SL LBT failure is reported to the gNB and while generating the MAC PDU to be sent to the gNB in ​​the UL grant, the selection of logical channels to be included in the MAC PDU shall be prioritized according to the following order (highest priority listed first):

[0164] MAC CE for C-RNTI, or data from UL-CCCH;

[0165] MAC CE for (enhanced) BFR, or MAC CE for configuration authorization confirmation, or MAC CE for multi-entry configuration authorization confirmation;

[0166] MAC CE for side link configuration authorization confirmation;

[0167] MAC CE for LBT failure;

[0168] MAC CE for SL LBT failure;

[0169] MAC CE for timing advance reporting;

[0170] MAC CE for SL-BSR prioritized according to 3GPP clause 5.22.1.6;

[0171] MAC CE for (extended) BSR, except for the BSR included for padding;

[0172] MAC CE for (enhanced) single-entry PHR, or MAC CE for (enhanced) multiple-entry PHR;

[0173] MAC CE for positioning measurement gap activation / deactivation request;

[0174] MAC CE for the desired number of protection symbols;

[0175] MAC CE for timing request in case 6;

[0176] MAC CE for (extended) preemptive BSR;

[0177] MAC CE for SL-BSRs, except for SL-BSRs prioritized according to 3GPP clause 5.22.1.6 and SL-BSRs included for padding;

[0178] MAC CE for IAB-MT recommended beam indication, or MAC CE for expected IAB-MT PSD range, or MAC CE for expected DL Tx power adjustment;

[0179] Data from any logical channel, except data from UL-CCCH;

[0180] MAC CE for recommended bit rate query;

[0181] MAC CE for the BSR included for padding; and

[0182] MAC CE for SL-BSR included for padding.

[0183] According to an embodiment of the present disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided. The method may include: receiving configuration information associated with side link (SL) listen-before-talk (LBT) failure recovery from a base station; identifying a counter value associated with SL LBT failure detection based on an SL LBT failure indication received from a lower layer; and triggering SL continuous LBT failure when the counter value is greater than or equal to a threshold.

[0184] In a further embodiment, upon receiving an SL LBT failure indication, the counter value is incremented by 1, and the method may further include: sending a SL LBT failure media access control (MAC) control element (CE) for the triggered SL persistent LBT failure to the base station.

[0185] In a further embodiment, the configuration information includes information associated with the threshold and information associated with a timer related to the above-mentioned SL LBT failure detection, and the method may also include: starting or restarting the timer in case of receiving an SL LBT failure indication.

[0186] In a further embodiment, the counter value is reset to zero in case the timer expires, or in case the information associated with the threshold value or the information associated with the timer is reconfigured.

[0187] In a further embodiment, the configuration information is received via a radio resource control (RRC) reconfiguration message or system information or SL preconfiguration information, and the configuration information is configured per SL bandwidth part (BWP).

[0188] In a further embodiment, the SL LBT failure indication is triggered when the UE fails to access the channel prior to SL transmission.

[0189] In a further embodiment, the identifying of the counter value comprises counting SL LBT failure indications for all SL transmissions.

[0190] In a further embodiment, the method may also include: if uplink shared channel (UL-SCH) resources are available for new transmission and the UL-SCH resources are able to accommodate the SL LBT failure media access control (MAC) control element (CE) and the sub-header of the SL LBT failure MAC CE, then: generating a SL LBT failure MAC CE indicating resource-related information for the SL persistent LBT failure; and otherwise, triggering a scheduling request for the SL LBT failure MAC CE.

[0191] In a further embodiment, the method may further include: selecting a logical channel based on the priority of the logical channel, wherein the SL LBT failure MAC CE has a higher priority than at least one MAC CE including a MAC CE for a timing advance report, and wherein the SL LBT failure MAC CE has a lower priority than at least one MAC CE including a MAC CE for a side link configuration authorization confirmation or a MAC CE for a beam failure report (BER).

[0192] In a further embodiment, the method may further include: canceling the scheduling request and stopping the timer associated with the scheduling request when a MAC protocol data unit (PDU) is sent and the MAC PDU includes a SL LBT failure MAC CE or the triggered SL continuous LBT failure is canceled.

[0193] In a further embodiment, the method may further include: in a case where the MAC PDU is sent and the MAC PDU includes a SLLBT failure MAC CE, cancelling the triggered SL continuous LBT failure.

[0194] In a further embodiment, the method may further include: canceling the triggered SL persistent LBT failure in a case where configuration information associated with SL LBT failure recovery is reconfigured.

[0195] In a further embodiment, the method may further include: receiving scheduling request configuration information associated with the SL continuous LBT failure report from the base station; and sending a scheduling request for the SL continuous LBT failure report to the base station based on the scheduling request configuration information.

[0196] In a further embodiment, the method may also include: based on the triggering of SL persistent LBT failure, declaring a radio link failure (RLF) and performing radio link failure (RLF) related operations for one or more destinations, and wherein the execution of the RLF related operations includes: releasing the data radio bearer (DRB), signaling radio bearer (SRB) and PC5 relay radio link control (RLC) channel of the destination; discarding the new radio (NR) SL communication related configuration of the destination; resetting the SL-specific MAC of the destination; and sending an indication of PC5-RRC connection release for the destination to the upper layer.

[0197] According to an embodiment of the present disclosure, a user equipment (UE) in a wireless communication system is provided. The UE may include: a transceiver; and at least one processor, the at least one processor being coupled to the transceiver and configured to: receive configuration information associated with sidelink (SL) listen-before-talk (LBT) failure recovery from a base station via the transceiver; identify a counter value associated with SL LBT failure detection based on an SL failure indication received from a lower layer; and trigger SL continuous LBT failure when the counter value is greater than or equal to a threshold.

[0198] Figure 3 is a diagram showing a UE 300 according to an embodiment of the present disclosure.

[0199] refer to Figure 3 UE 300 may include a processor 310, a transceiver 320, and a memory 330. However, not all of the components shown are required. UE 300 may include a processor 310, a transceiver 320, and a memory 330. Figure 3 Furthermore, according to another embodiment, the processor 310, the transceiver 320, and the memory 330 may be implemented as a single chip.

[0200] The aforementioned components will now be described in detail.

[0201] The processor 310 may include one or more processors or other processing devices that control the proposed functions, processes and / or methods. The operations of the UE 300 may be implemented by the processor 310.

[0202] The transceiver 320 may be connected to the processor 310 and transmit and / or receive a signal. In addition, the transceiver 320 may receive a signal through a wireless channel and output the signal to the processor 310. The transceiver 320 may transmit a signal output from the processor 310 through a wireless channel.

[0203] The memory 330 may store control information or data included in a signal obtained by the UE 300. The memory 330 may be connected to the processor 310 and store at least one instruction or protocol or parameter for the proposed function, process and / or method. The memory 330 may include a read-only memory (ROM) and / or a random access memory (RAM) and / or a hard disk and / or a CD-ROM and / or a DVD and / or other storage devices.

[0204] Figure 4 is a diagram showing a base station 400 according to an embodiment of the present disclosure.

[0205] refer to Figure 4 , the base station 400 may include a processor 410, a transceiver 420, and a memory 430. However, all the components shown are not required. The base station 400 may be composed of Figure 4 In addition, according to another embodiment, the processor 410, the transceiver 420 and the memory 430 may be implemented as a single chip. The aforementioned components will now be described in detail.

[0206] The processor 410 may include one or more processors or other processing devices to control the proposed functions, processes and / or methods. The operations of the base station 400 may be implemented by the processor 410.

[0207] The transceiver 420 may be connected to the processor 410 and transmit and / or receive signals. The signals may include control information and data. In addition, the transceiver 420 may receive signals through a wireless channel and output the signals to the processor 410. The transceiver 420 may transmit signals output from the processor 410 through a wireless channel.

[0208] The memory 430 may store control information or data included in a signal obtained by the base station 400. The memory 430 may be connected to the processor 410 and store at least one instruction or protocol or parameter for the proposed function, process and / or method. The memory 430 may include a read-only memory (ROM) and / or a random access memory (RAM) and / or a hard disk and / or a CD-ROM and / or a DVD and / or other storage devices.

[0209] The methods according to various embodiments of the present disclosure described in the claims or specification of the present disclosure may be implemented by hardware, software, or a combination of hardware and software.

[0210] When implemented with software, a computer-readable storage medium storing one or more programs (software modules) may be provided. One or more programs stored in the computer-readable storage medium are configured to be executed by one or more processors in an electronic device. One or more programs may include instructions that cause the electronic device to perform the methods of various embodiments of the present disclosure described in the claims or specification of the present disclosure.

[0211] The program (software module, software) may be stored in a random access memory (RAM), a non-volatile memory including flash memory, a read only memory (ROM), an electrically erasable programmable ROM (EEPROM), a magnetic disk storage device, a compact disk-ROM (CD-ROM), a digital versatile disk (DVD) or other types of optical storage devices and / or cassette tapes. Alternatively, the program may be stored in a memory including a combination of some or all of them. There may be multiple memories.

[0212] The program may also be stored in an attachable storage device that can be accessed through a communication network including the Internet, an intranet, a local area network (LAN), a wide area network (WAN), or a storage area network (SAN), or a combination thereof. The storage device may be connected to the apparatus for executing various embodiments of the present disclosure through an external port. In addition, a separate storage device in the communication network may be connected to the apparatus for executing various embodiments of the present disclosure.

[0213] In various embodiments of the present disclosure, components are represented in singular or plural form. However, it should be understood that for ease of explanation, singular or plural representation is appropriately selected according to the presented situation, and the present disclosure is not limited to components in singular or plural form. In addition, components expressed in plural form may also imply singular form, and vice versa.

[0214] While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

1. A method performed by a user equipment (UE) in a wireless communication system, the method comprising: receiving configuration information associated with sidelink (SL) listen-before-talk (LBT) failure recovery from a base station; identifying a counter value associated with SL LBT failure detection based on an SL LBT failure indication received from a lower layer; and When the counter value is greater than or equal to the threshold, SL continuous LBT failure is triggered.

2. The method according to claim 1, wherein: Upon receiving the SL LBT failure indication, the counter value is incremented by 1, and Wherein, the method further comprises: A SL LBT failure media access control (MAC) control element (CE) for the triggered SL persistent LBT failure is sent to the base station.

3. The method according to claim 1, wherein: The configuration information includes information associated with the threshold and information associated with a timer related to the SL LBT failure detection, and Wherein, the method further comprises: Upon receiving the SL LBT failure indication, start or restart the timer.

4. The method according to claim 3, wherein: In case the timer expires, or in case the information associated with the threshold or the information associated with the timer is reconfigured, the counter value is reset to zero.

5. The method according to claim 1, wherein: The configuration information is received via a radio resource control (RRC) reconfiguration message or system information or SL preconfiguration information, and The configuration information is configured according to each SL bandwidth part (BWP).

6. The method according to claim 1, wherein: The SL LBT failure indication is triggered when the UE fails to access the channel before SL transmission.

7. The method according to claim 1, wherein: The identifying of the counter value comprises: The SL LBT failure indications are counted for all SL transmissions.

8. The method according to claim 1, further comprising: If an uplink shared channel (UL-SCH) resource is available for new transmission and the UL-SCH resource can accommodate the SLLBT Failure MAC CE and the sub-header of the SLLBT Failure MAC CE, then: generating the SL LBT failure MAC CE, wherein the SL LBT failure MAC CE indicates resource-related information for the SL continuous LBT failure; and otherwise: Trigger a scheduling request for the SL LBT failure MAC CE.

9. The method according to claim 8, further comprising: The logical channel is selected based on the priority of the logical channel, wherein the SL LBT failure MAC CE has a higher priority than at least one MAC CE including a MAC CE for a timing advance report, and The SL LBT failure MAC CE has a lower priority than at least one MAC CE including a MAC CE for side link configuration authorization confirmation or a MAC CE for beam failure report (BFR).

10. The method according to claim 8, further comprising: In case a MAC protocol data unit (PDU) is sent and the MAC PDU includes the SL LBT failure MAC CE or the triggered SL persistent LBT failure is cancelled, the scheduling request is cancelled and a timer associated with the scheduling request is stopped.

11. The method according to claim 8, further comprising: In case a MAC PDU is sent and the MAC PDU includes the SL LBT failure MAC CE, the triggered SL continuous LBT failure is canceled.

12. The method according to claim 1, further comprising: In case the configuration information associated with the SL LBT failure recovery is reconfigured, the triggered SL persistent LBT failure is canceled.

13. The method according to claim 1, further comprising: receiving, from the base station, scheduling request configuration information associated with a SL persistent LBT failure report; as well as Based on the scheduling request configuration information, a scheduling request for the SL continuous LBT failure report is sent to the base station.

14. The method according to claim 1, further comprising: Based on said triggering of said SL persistent LBT failure, declaring a radio link failure (RLF) and performing RLF-related operations for one or more destinations, and The execution of the RLF-related operation includes: releasing a data radio bearer (DRB), a signaling radio bearer (SRB), and a PC5 relay radio link control (RLC) channel of the one or more destinations; discarding a New Radio (NR) SL communication related configuration of the one or more destinations; resetting the SL-specific MAC of the one or more destinations; and Send an indication of PC5-RRC connection release for the one or more destinations to an upper layer.

15. A user equipment (UE) in a wireless communication system, the UE comprising: Transceiver; as well as at least one processor coupled to the transceiver and configured to: receiving, via the transceiver, configuration information associated with sidelink (SL) listen-before-talk (LBT) failure recovery from a base station; identifying a counter value associated with SL LBT failure detection based on an SL failure indication received from a lower layer; and When the counter value is greater than or equal to the threshold, SL continuous LBT failure is triggered.

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