Coding with persistent listen-before-talk failures

Abstract

Example embodiments of the present disclosure relate to coping with persistent listen before talk (LBT) failures. A first terminal device may determine that a continuous listen before talk (LBT) failure on a sidelink resource set is detected; and transmitting information related to the persistent LBT failure to at least one of the second terminal device or the network device. In this manner, the reliability of sidelink communication may be improved even in the case of persistent LBT failure.

Description

Technical Field

[0001] Example embodiments of the present disclosure relate generally to the field of telecommunications, and more particularly to apparatus, methods, and computer-readable storage media for coping with persistent listen-before-talk (LBT) failures. Background Art

[0002] New Radio (NR) operation in unlicensed bands relies on the user equipment (UE) to sense the radio resources before starting transmission. This technique is called LBT. In NR in unlicensed spectrum (NR-U), in order to coexist with other wireless technologies in unlicensed bands, such as Wi-Fi systems, LBT procedures can be performed before each transmission to occupy the channel.

[0003] Sidelink (SL) transmission can also operate on unlicensed bands. An LBT mechanism in NR-U can be introduced for SL transmission to coexist with other wireless systems on unlicensed bands. Before each SL transmission, the SL UE can perform an LBT procedure and discard the SL transmission if LBT fails. Enhancements to SL in unlicensed spectrum (SL-U) are still needed. Summary of the Invention

[0004] In general, example embodiments of the present disclosure provide a solution for coping with persistent LBT failures.

[0005] In a first aspect, a first terminal device is provided. The first terminal device includes at least one processor and at least one memory storing instructions. The instructions, when executed by the at least one processor, cause the first terminal device to at least: determine that a persistent listen-before-talk (LBT) failure on a link resource set is detected; and send information related to the persistent LBT failure to at least one of a second terminal device or a network device.

[0006] In a second aspect, a second terminal device is provided. The second terminal device includes at least one processor and at least one memory storing instructions. The instructions, when executed by the at least one processor, cause the second terminal device to at least: receive information related to persistent listen-before-talk (LBT) failures detected by a first terminal device on a set of sidelink resources; and send at least one sidelink transmission to the first terminal device on at least one sidelink resource determined based on the received information.

[0007] In a third aspect, a network device is provided. The network device includes at least one processor and at least one memory storing instructions. When executed by the at least one processor, the instructions cause the network device to at least: receive first information related to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a sidelink resource set from a first terminal device; and send second information determined based on the first information to a second terminal device.

[0008] In a fourth aspect, a method is provided, comprising: determining, at a first terminal device, that a persistent listen-before-talk (LBT) failure on a sidelink resource set is detected; and sending information related to the persistent LBT failure to at least one of a second terminal device or a network device.

[0009] In a fifth aspect, a method is provided. The method comprises: receiving, at a first terminal device, information relating to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a set of sidelink resources; and sending, to the first terminal device, at least one sidelink transmission on at least one sidelink resource determined based on the received information.

[0010] In a sixth aspect, a method is provided, comprising: receiving, at a network device, first information from a first terminal device related to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a sidelink resource set; and sending, to a second terminal device, second information determined based on the first information.

[0011] In a seventh aspect, an apparatus is provided, comprising: means for determining that a persistent listen-before-talk (LBT) failure on a sidelink resource set is detected; and means for sending information related to the persistent LBT failure to at least one of a second terminal device or a network device.

[0012] In an eighth aspect, an apparatus is provided. The apparatus comprises: means for receiving information related to a persistent listen-before-talk (LBT) failure detected by a first terminal device on a set of sidelink resources; and means for sending at least one sidelink transmission to the first terminal device on at least one sidelink resource determined based on the received information.

[0013] In a ninth aspect, an apparatus is provided. The apparatus comprises: means for receiving, from a first terminal device, first information related to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a sidelink resource set; and means for sending, to a second terminal device, second information determined based on the first information.

[0014] In a tenth aspect, an apparatus is provided. The apparatus includes: circuitry configured to determine that a persistent listen-before-talk (LBT) failure on a sidelink resource set is detected; and circuitry configured to transmit information related to the persistent LBT failure to at least one of a second terminal device or a network device.

[0015] In an eleventh aspect, an apparatus is provided. The apparatus comprises: receive circuitry configured to receive information related to a persistent listen-before-talk (LBT) failure detected by a first terminal device on a set of sidelink resources; and transmit circuitry configured to transmit at least one sidelink transmission to the first terminal device on at least one sidelink resource determined based on the received information.

[0016] In a twelfth aspect, an apparatus is provided. The apparatus comprises: a receiving circuit system configured to receive, from a first terminal device, first information related to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a sidelink resource set; and a transmitting circuit system configured to transmit, to a second terminal device, second information determined based on the first information.

[0017] In a thirteenth aspect, a non-transitory computer-readable storage medium comprising program instructions is provided. When the program instructions are executed by a device, the device at least performs the method according to any one of the fourth to sixth aspects above.

[0018] In a fourteenth aspect, there is provided a computer program comprising instructions that, when executed by a first terminal device, cause the first terminal device to at least: determine that a persistent listen-before-talk (LBT) failure on a sidelink resource set is detected; and send information related to the persistent LBT failure to at least one of a second terminal device or a network device.

[0019] In a fifteenth aspect, there is provided a computer program comprising instructions that, when executed by a second terminal device, cause the second terminal device to at least: receive information relating to a persistent listen-before-talk (LBT) failure detected by a first terminal device on a set of sidelink resources; and send at least one sidelink transmission to the first terminal device on at least one sidelink resource determined based on the received information.

[0020] In a sixteenth aspect, there is provided a computer program comprising instructions that, when executed by a network device, cause the network device to at least: receive, from a first terminal device, first information related to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a sidelink resource set; and send, to a second terminal device, second information determined based on the first information.

[0021] It should be understood that the invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0023] Figure 1A illustrates an example of a network environment in which some example embodiments of the present disclosure may be implemented;

[0024] Figure 1B illustrates an example of a SL transmission process with hybrid automatic repeat request (HARQ) feedback in which some example embodiments of the present disclosure may be implemented;

[0025] Figure 1C illustrates an example of an SL time slot in which some example embodiments of the present disclosure may be implemented;

[0026] Figure 1D illustrates an example of channel mapping in SL transmission in which some example embodiments of the present disclosure may be implemented;

[0027] Figure 1E illustrates an example of an IUC information MAC CE for a first inter-UE coordination (IUC) scheme in which some example embodiments of the present disclosure may be implemented;

[0028] Figure 1F illustrates an example of an IUC request MAC CE for a first IUC scheme in which some example embodiments of the present disclosure may be implemented;

[0029] Figure 2 illustrates a flow chart illustrating a communication process according to some example embodiments of the present disclosure;

[0030] Figure 3 A flowchart is illustrated, which illustrates a process for the behavior of a first terminal device in different situations according to some example embodiments of the present disclosure;

[0031] Figure 4 A flowchart illustrating an example method implemented at a first terminal device according to some example embodiments of the present disclosure is illustrated;

[0032] Figure 5 A flowchart illustrating an example method implemented at a second terminal device according to some example embodiments of the present disclosure is illustrated;

[0033] Figure 6illustrates a flow chart of an example method implemented at a network device according to some example embodiments of the present disclosure;

[0034] Figure 7 illustrates a simplified block diagram of a device suitable for implementing some example embodiments of the present disclosure; and

[0035] Figure 8 A block diagram illustrating an example of a computer-readable medium according to some example embodiments of the present disclosure is illustrated.

[0036] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0037] The principles of the present disclosure will now be described with reference to some exemplary embodiments. It should be understood that these embodiments are described for illustrative purposes and to help those skilled in the art understand and implement the present disclosure, and do not represent any limitation on the scope of the present disclosure. The present disclosure described herein can be implemented in various other ways in addition to the ways described below.

[0038] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0039] In this disclosure, references to "one embodiment," "an embodiment," and "an example embodiment" indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment must include the particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, those skilled in the art believe that it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0040] It should be understood that although the terms "first" and "second" etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the example embodiments, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0041] The term used herein is used to describe the purpose of specific embodiment, but is not intended to limit example embodiment. The singular form "a", "an" and "the" used herein are also intended to include plural forms, unless the context clearly states otherwise. It will also be understood that the terms "comprises", "comprising", "has", "having", "includes" and / or "including" specify the existence of the features, elements and / or components when used in this article, but do not exclude the existence or addition of one or more other features, elements, components and / or their combinations. As used in this article, "at least one of the following: <list of two or more elements>" and "at least one of the list of two or more elements>" and similar wording (wherein the list of two or more elements is connected by "and" or "or") represent at least any one element in these elements, or at least any two or more elements in these elements, or at least all elements in these elements.

[0042] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0043] (a) hardware circuit implementations only (such as implementations using only analog and / or digital circuitry), and

[0044] (b) a combination of hardware circuitry and software such as (if applicable):

[0045] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0046] (ii) any portion of hardware processor(s) with software (including digital signal processor(s), software and memory(s) that work together to enable a device (such as a mobile phone or server) to perform various functions), and

[0047] (c) Hardware circuit(s) and / or processor(s) (such as microprocessor(s) or portion(s) of microprocessor(s)) that require software (e.g., firmware) for operation, but in which case the software may not be present when not required for operation.

[0048] This definition of circuitry applies to all uses of the term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers merely a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (their) accompanying software and / or firmware implementation. The term circuitry also covers (for example, and if applicable to a particular claim element) a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0049] As used herein, the term "communication network" refers to a network that complies with any suitable communication standard, such as Long Term Evolution (LTE), Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal equipment and the network equipment in the communication network can be performed according to any suitable generation of communication protocol, including but not limited to the fourth generation (4G), 4.5G, fifth generation (5G) communication protocols, and / or any other protocol currently known or to be developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communications, there will certainly be future types of communication technologies and systems that utilize them to embody the present disclosure. It should not be regarded as limiting the scope of the present disclosure to only the above-mentioned systems.

[0050] As used herein, the term "network device" refers to a node in a communication network, via which a terminal device accesses the network and receives services from the network. Depending on the terminology and technology used, a network device may refer to a base station (BS) or an access point (AP), for example, a Node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, a low-power node (such as a femto, pico), etc. In the following description, the terms "network device" and "network node" may be used interchangeably.

[0051] The term "terminal device" refers to any terminal device capable of wireless communication. By way of example and not limitation, a terminal device may also be referred to as a communication device, user equipment (UE), subscriber station (SS), portable subscriber station, mobile station (MS) or access terminal (AT). Terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image capture terminal devices (such as digital cameras), gaming terminal devices, music storage and playback applications, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop mounted devices (LMEs), USB dongles, smart devices, wireless customer premises equipment (CPEs), Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated process chain environments), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0052] As described above, the LBT mechanism in NR-U can be introduced into sidelink transmission, allowing sidelink transmission to coexist with other wireless systems on unlicensed bands. Before each sidelink transmission, the sidelink UE can perform the LBT process to occupy the channel, and if LBT fails, the sidelink transmission is discarded.

[0053] In RAN2#119bis-e, it was agreed that SL-U should support a continuous LBT failure detection procedure. During the continuous LBT failure detection procedure, the device can count the number of LBT failures. If the count exceeds a threshold (provided by the device, NW or resource-specific configuration), a continuous LBT failure is triggered. The counting occurs during a monitoring period or window, which can be started based on a device decision, triggered by the network or as a moving window. The duration of the monitoring window can be NW configuration, resource-specific configuration or depend on the device decision. SL-specific continuous LBT failure detection (and recovery procedure) is a device-centric event and therefore has an impact on any process in which two or more devices interact. For example, if a transmitting (Tx) UE is not experiencing a persistent LBT failure in a particular resource block (RB) set (or resource pool), the Tx UE is able to access resources in the RB set (or resource pool), i.e., by successfully performing LBT; and transmit its PSCCH / PSSCH transmission with the associated sidelink control information (SCI) requesting HARQ feedback via the PSFCH resources mapped to the PSCCH / PSSCH resources. However, the Rx UE may be experiencing a persistent LBT failure in the RB set (or resource pool) to which the PSFCH is mapped, and therefore cannot access the mapped PSFCH resources to provide HARQ feedback. In this case, the Tx UE will not know whether it should perform HARQ retransmission, and therefore the communication cannot be assumed to be reliable.

[0054] There is a need to enhance sidelink transmission.Accordingly, embodiments of the present disclosure provide a solution for coping with persistent LBT failures in sidelink communications.

[0055] Figure 1A The diagram illustrates an example of a network environment 100 in which some example embodiments of the present disclosure may be implemented. In the description of the example embodiments of the present disclosure, the network environment 100 may also be referred to as a communication system 100 (e.g., a portion of a communication network). For illustrative purposes only, various aspects of the example embodiments will be described in the context of one or more terminal devices and network devices communicating with each other. However, it should be understood that the description herein may be applicable to other types of devices or other similar devices referred to using other terms.

[0056] like Figure 1A As shown in FIG, a communication environment 100 includes a network device 110 (hereinafter also referred to as gNB 110), a first terminal device 120-1, and a second terminal device 120-2. The network device 110 is associated with one or more service areas (i.e., land areas referred to as “cells”). Figure 1AAs shown in FIG, network device 110 manages cell 105 and serves a first terminal device 120-1 and a second terminal device 120-2 (collectively referred to as terminal device 120) in cell 105. It should be understood that the number of network devices, terminal devices, and / or cells is provided for illustrative purposes only and does not represent any limitation on the scope of the present disclosure. Communication system 100 may include any suitable number of network devices, terminal devices, and / or cells suitable for implementing the present disclosure.

[0057] In order to transmit data and / or control information, the terminal devices 120-1 and 120-2 may respectively perform communication with the network device 110. Specifically, as Figure 1A As shown in the exemplary scenario of , first terminal device 120-1 can communicate with network device 110 via communication link 115-1, and second terminal device 120-2 can communicate with network device 110 via communication channel 115-2. For transmission from network device 110 to terminal device 120-1 or 120-2, communication link 115-1 or 115-2 can be referred to as a downlink, while for transmission from terminal device 120-1 or 120-2 to network device 110, the communication link can alternatively be referred to as an uplink.

[0058] In addition to the communication links 115-1 and 115-2, the first terminal device 120-1 and the second terminal device 120-2 may also perform sidelink transmission via a sidelink 125 between the first terminal device 120-1 and the second terminal device 120-2, which is also referred to as device-to-device (D2D) communication. Figure 1A In an exemplary scenario, a second terminal device 120-2 (hereinafter also referred to as Tx UE 120-2, SL Tx UE 120-2, or initiating terminal device 120-2) performs a sidelink transmission 125-1 to a first terminal device 120-1 (hereinafter also referred to as Rx UE 120-1, SL Rx UE 120-1, or responding terminal device 120-1) via a sidelink 125. In some example embodiments, the sidelink transmission 125-1 may be performed in an unlicensed frequency band, in which various wireless devices based on different wireless technologies share the same wireless spectrum.

[0059] As used herein, the term "sidelink transmission" generally refers to any transmission performed from one terminal device to another terminal device. Sidelink transmission can be used to send any data or control information associated with sidelink communication, such as sidelink data, sidelink control information, sidelink feedback information, etc. As used herein, the term "sidelink channel" generally refers to any channel used for sidelink communication, such as the Physical Sidelink Shared Channel (PSSCH), the Physical Sidelink Control Channel (PSCCH), the Physical Sidelink Discovery Channel (PSDCH), the Physical Sidelink Broadcast Channel (PSBCH), the Physical Sidelink Feedback Channel (PSFCH), and other existing or future sidelink channels.

[0060] Channel access in the sidelink can rely on a so-called LBT feature, in which, before performing a sidelink transmission 125-1, the second terminal device 120-2 can first "sense" the communication channel to detect that there is no communication on the communication channel before any transmission on the communication channel. For example, the "channel sensing" process can rely on detecting the energy level on the communication channel. LBT parameters (such as type / duration, clear channel assessment parameters, etc.) can be configured in the second terminal device 120-2, for example, by the network device 110.

[0061] In some example embodiments, network device 110 may not be in communication environment 100. For example, one or more of terminal devices 120-1 and 120-2 and other terminal devices (not shown) may be outside the coverage of network device 110 (i.e., outside cell 105). In this case, one or more of terminal devices 120-1, 120-2 may be outside the coverage of cell 105. Figure 1A Only sidelink communication can exist between possible other terminal devices not shown.

[0062] Despite Figure 1A The network device 110 and the terminal devices 120-1 and 120-2 are described in the communication environment 100 of FIG. 1 , but the embodiments of the present disclosure are also applicable to any other suitable communication devices that communicate with each other. That is, the embodiments of the present disclosure are not limited to Figure 1A In this regard it should be noted that although Figure 1A In the embodiment, the network device 110 is schematically depicted as a base station, and the terminal device 120 is schematically depicted as a vehicle-mounted terminal device, but it should be understood that these depictions are exemplary in nature and do not represent any limitation. In other embodiments, the network device 110 and the terminal device 120 can be any other communication device, such as any other wireless communication device.

[0063] In the case where the terminal devices 120-1 and 120-2 are vehicle-mounted terminal devices, the communication related thereto may be referred to as V2X communication. Figure 1A Although not shown, V2X communication related to the terminal device 120 may include a communication channel between the first terminal device 120-1 or the second terminal device 120-2 and any other communication device, including but not limited to infrastructure equipment, another vehicle-mounted terminal device, a pedestrian's device, a roadside unit, etc. In addition, although not shown, as Figure 1A All communication links shown in may be via one or more relays.

[0064] Communications in network environment 100 may be implemented according to any suitable communication protocol(s), including but not limited to fourth generation (4G) and fifth generation (5G) cellular communication protocols, wireless local area network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, and / or any other protocol currently known or to be developed in the future. Furthermore, communications may utilize any suitable wireless communication technology, including but not limited to: code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), frequency division duplex (FDD), time division duplex (TDD), multiple input multiple output (MIMO), orthogonal frequency division multiplexing (OFDM), discrete Fourier transform spread spectrum OFDM (DFT-s-OFDM), and / or any other technology currently known or to be developed in the future.

[0065] During 3GPP Rel-16, NR SL has been designed to facilitate UEs to communicate with nearby (multiple) other UEs via direct / SL communication. Two resource allocation modes have been specified, and a SL Tx UE can be configured with one of these modes to perform its NR SL transmissions. These modes are denoted as NR SL Mode 1 and NR SL Mode 2. In NR SL Mode 1, sidelink transmission resources can be allocated or scheduled to the terminal device by the network device, while in NR SL Mode 2, the terminal device can autonomously select its SL transmission resources.

[0066] In the unlicensed bands below 7 GHz, coexistence of New Radio (NR) with other systems (such as IEEE 802.11) is ensured via a listen-before-talk (LBT) channel access mechanism. Similarly, a terminal device intending to perform a sidelink (SL) transmission needs to first successfully complete the LBT check before being able to initiate the same transmission.

[0067] For a terminal device to pass the LBT check, it must observe the channel as available for a number of consecutive Clear Channel Assessment (CCA) slots. In bands below 7 GHz, these slots are 9 μs in duration. If the measured power or collected energy during the CCA slot is below a regulatory threshold (which may depend on the operating band and geographic region), the UE considers the channel available in the CCA slot.

[0068] In some exemplary embodiments, when Tx UE 120-2 initiates sidelink communication, Tx UE 120-2 must obtain "rights" to access the channel for a certain period of time (denoted in the specification as the channel occupancy time (COT)) by applying an "extended" LBT procedure, in which the channel must be considered idle for the entire duration of the contention window (CW). This "extended" LBT procedure is referred to as LBT Type 1. The duration of both the COT and the CW depends on the channel access priority level (CAPC) associated with the traffic of Rx UE 120-1. In some exemplary embodiments, Tx UE 120-2 (which initiates transmission after successfully completing LBT Type 1 and performs SL transmissions to Rx UE 120-1 in the PSCCH and PSSCH) obtains a COT1 with a duration associated with the corresponding CAPC. Even if Tx UE 120-2 suspends its transmission, the acquired COT1 is valid, although if Tx UE 120-2 wants to perform a new transmission (within the COT), it still needs to perform a "reduced" LBT procedure. This "reduced" LBT procedure may be referred to as LBT Type 2, as described in 3GPP specification TS 37.213, with the following variants:

[0069] Type 2A (25 μs LBT) is used for SL transmission within the COT acquired by the initiating device, and is also used for SL transmission following another SL transmission if the gap between two SL transmissions is ≥ 25 μs.

[0070] Type 2B (16 μs LBT) is used for SL transmission within the COT acquired by the initiating device, which can only be used for SL transmission after another SL with a gap exactly equal to 16 μs.

[0071] Type 2C (no LBT) can only be used for SL transmission after another SL, with a gap < 16 μs, and the allowed duration of SL transmission is ≤ 584 μs.

[0072] Figure 1B FIGURE 1 illustrates an example of a SL transmission process 130 with HARQ feedback in which some example embodiments of the present disclosure may be implemented. For discussion purposes, reference will be made to Figure 1ADescribe the SL transmission process 130. The SL transmission process 130 may involve Figure 1A It will be understood that although reference has been made to the Tx UE 120-2 and the Rx UE 120-1 shown in FIG. Figure 1A The communication process 130 is described with reference to the network environment 100, but the communication process 130 can also be applied to other similar communication scenarios.

[0073] like Figure 1B As shown in FIG, at 131, unicast setup may be performed between Tx UE 120-2 and Rx UE 120-1. At 132, Tx UE 120-2 may send an initial transmission to Rx UE 120-1. The initial transmission may include an SCI and a TB, the TB including one or more MAC protocol data units (PDUs). The SCI may follow a two-phase SCI structure and indicate a source ID, a destination ID, a transmission type (= unicast), a HARQ feedback enable / disable indicator, and HARQ parameters such as a HARQ process number, a new data indicator (NDI), and a redundancy version (RV). For example, the SCI may utilize a HARQ feedback enable / disable indicator to indicate that HARQ feedback is enabled. At 133, Rx UE 120-1 may decode the SCI. At 134, Rx UE 120-1 may attempt to decode the TB. At 135, if decoding of the TB fails, Rx UE 120-1 may send an indication of unsuccessful data transmission to Tx UE 120-2. For example, this indication may be represented as "NACK." At 136, Tx UE 120-2 may resend the SCI and TB. At 137, Rx UE 120-1 may decode the resent SCI. At 134, Rx UE 120-1 may attempt to decode the resent TB. At 138, if decoding of the TB succeeds, Rx UE 120-1 may send an indication of successful data transmission to Tx UE 120-2. For example, this indication may be represented as "ACK."

[0074] The PSFCH was introduced during Rel-16 to enable HARQ feedback on the sidelink from the Rx UE 120-1, the intended recipient of the PSSCH transmission, to the Tx UE 120-2 performing the transmission. Within the PSFCH, the Zadoff-Chu sequence in one physical resource block (PRB) is repeated over two OFDM symbols near the end of the SL resource in the slot, where the first OFDM symbol can be used for AGC. Figure 1C An example of an SL slot in which some example embodiments of the present disclosure may be implemented is illustrated. A Zadoff-Chu sequence as a basic sequence may be preconfigured per sidelink resource pool.

[0075] According to 3GPP TS 38.331, the time resources for the PSFCH are preconfigured to occur every 0, 1, 2, or 4 time slots. The HARQ feedback resources in the PSFCH are derived from the resource locations of the PSCCH / PSSCH. For PSSCH to HARQ timing, there is a configuration parameter K with units of time slots. The time timing for the PSFCH is determined from K. For a PSSCH transmission with its last symbol in time slot n, HARQ feedback is in time slot n+a, where a is the smallest integer greater than or equal to K, with the condition that time slot n+a contains PSFCH resources. A time interval of at least K time slots allows the processing delay of Rx UE 120-1 to be accounted for when decoding the PSCCH and generating HARQ feedback. K can be equal to 2 or 3, and a single K value can be preconfigured for each resource pool. This allows multiple Rx UEs using the same resource pool to utilize the same PSFCH resource mapping for HARQ feedback. Using the parameter K, N PSSCH slots associated with the slot with PSFCH can be determined.

[0076] Figure 1D The diagram illustrates an example of a channel mapping in which some example embodiments of the present disclosure may be implemented. The period of the PSFCH resource is configured as N=4, where there are 4 PSSCH time slots associated with the PSFCH, and K or sl-MinTimeGapPSFCH is configured as 2. In the case where there are L subchannels in the resource pool and there are N PSSCH time slots associated with the time slot containing the PSFCH, there are N*L subchannels associated with the PSFCH symbol. In the case where there are M PRBs available for PSFCH in the PSFCH symbol, there are M PRBs available for HARQ feedback for transmissions on the N*L subchannels.

[0077] When M is configured as a multiple of N*L, a different set of Mset=M / (N*L) PRBs may be associated with HARQ feedback for each subchannel within the PSFCH period. The first set of Mset PRBs of the M PRBs available for PSFCH is associated with HARQ feedback for transmissions in the first subchannel in the first slot. The second set of Mset PRBs is associated with HARQ feedback for transmissions in the first subchannel in the second slot, and so on.

[0078] In some example embodiments, Figure 1D In FIG, N=4, L=3, and all PRBs in a PSFCH symbol are available for PSFCH. In this example, the HARQ feedback for a transmission at PSSCH x is in the M in the corresponding PSFCH symbol. set The signal is transmitted on a set x of PRBs, where x=1, ..., 12.

[0079] In some example embodiments, in the case of ACK / NACK feedback for multicast communications or in the case of different PSSCH transmissions in the same subchannel, the M associated with the subchannel set A set of PRBs can be shared among multiple Rx UEs. For each PRB available for PSFCH, there are Q cyclic shift pairs available to support ACK or NACK feedback for Q Rx UEs within the PRB. For the resource pool, the number of cyclic shift pairs Q is preconfigured and can be equal to 1, 2, 3, or 6.

[0080] In some example embodiments, the number F of PSFCH resources available to support HARQ feedback for a given transmission may be calculated. In 3GPP TS 38.213, F is denoted as With each PSFCH resource used by one Rx UE, F available PSFCH resources can be used for ACK / NACK feedback of a maximum of F Rx UEs.

[0081] In some example embodiments, the F PSFCH resources available for multiplexing HARQ feedback for PSSCH may be determined based on two options:

[0082] Option 1: F is based on the L PSSCH subchannels used by PSSCH, where F can be calculated as: F = LPSSCH*M set *Q PSFCHs associated with L PSSCH subchannels of PSSCH. There are L PSSCH subchannels of PSSCH, M PSFCHs associated with each subchannel. set PRBs, and Q cyclic shift pairs are available in each PRB.

[0083] Option 2: F is based only on the starting subchannel used by PSSCH, or only on one subchannel for the case where L PSSCHs > 1. F = M set *Q PSFCHs, which are associated with the starting subchannel of the PSSCH. There are M PSFCHs associated with each subchannel. set PRBs; and Q cyclic shift pairs are available in each PRB.

[0084] In some example embodiments, the available F PSFCH resources may be indexed based on a PRB index in the frequency domain and a cyclic shift pair index in the code domain. The mapping of PSFCH index i (i=1, 2, ..., F) to PRBs and to Q cyclic shift pairs is such that the PSFCH index i first increases with increasing PRB index until the number of available PRBs for PSFCH is reached. It then increases with increasing cyclic shift pair indexes, again with increasing PRB indexes, and so on.

[0085] Among the F PSFCHs available for HARQ feedback for a given transmission, the Rx UE selects for its HARQ feedback the PSFCH with index i given by:

[0086] i=(T ID +R ID )mod F,

[0087] Where T ID is the layer 1 identifier of the Rx UE indicated in the second stage SCI. For unicast ACK / NACK feedback and multicast NACK-only feedback, R ID = 0. Multicast NACK-only feedback is multicast option 1.

[0088] For multicast ACK / NACK feedback or multicast option 2, R ID Equal to the Rx UE identifier within the group, as indicated by higher layers. For X number of Rx UEs within the group, the Rx UE identifier is an integer between 0 and X-1. The Rx UE determines which PRB and cyclic shift pair should be used to transmit its HARQ feedback based on PSFCH index i. The Rx UE uses the first or second cyclic shift from the cyclic shift pair associated with the selected PSFCH index i to transmit a NACK or ACK, respectively.

[0089] By selecting the PSFCH with index i by the Rx UE, the Tx UE can distinguish the HARQ feedback of different Rx UEs via the Rx UE identifier, such as for multicast option 2; and distinguish the HARQ feedback for the Tx UE via the layer 1 ID of the Tx UE, such as for unicast. ID = 0, Rx UE is based only on layer 1 ID Tx UE identifier T ID to select the same PSFCH index i for its NACK-only feedback.

[0090] In some example embodiments, SL UEs may support inter-UE coordination (IUC) in Mode 2, whereby UE-A sends coordination information about resources to UE-B, which UE-B then uses for resource (re)selection. Two inter-UE coordination schemes are supported. In the first IUC scheme, the coordination information sent from UE-A to UE-B is the preferred or non-preferred resources for UE-B's transmission. In the second IUC scheme, the coordination information sent from UE-A to UE-B is the presence of expected / potential resource conflicts on resources indicated by UE-B's SCI.

[0091] In the first IUC scheme, IUC can be triggered by an explicit request from UE-B or by conditions at UE-A. UE-A determines a set of resources reserved by other UEs or time slots where UE-A does not expect to perform SL reception from UE-B due to half-duplex operation when it is the intended recipient of UE-B. UE-A uses these resources as a non-preferred resource set or excludes them to determine a preferred resource set, and sends the preferred / non-preferred resources to UE-B. The resources used by UE-B for resource (re)selection can be based on UE-B's perception results (if available) and coordination information received from UE-A, or it can be based solely on coordination information received from UE-A. For the first IUC scheme, MAC CE and second-stage SCI or MAC CE can only be used to send IUC. Explicit requests and reports for IUC in a unicast manner are supported. TS 38.331 specifies that, through configuration, the triggering condition for sending the IUC scheme 1 preferred / non-preferred resource message or the IUC scheme 1 request message is implemented by UE-A or when UE-A has data to send.

[0092] In the second IUC scheme, UE-A determines expected / potential resource conflicts within resources indicated by UE-B's SCI as resources reserved by other UEs and identified by UE-A as fully / partially overlapping with resources indicated by UE-B's SCI, or timeslots indicating that UE-A is the intended recipient of UE-B and does not expect to perform SL reception on these timeslots due to half-duplex operation. UE-B uses the conflicting resources to determine resources to be reselected and excludes the conflicting resources from the reselected resources. For the second IUC scheme, the PSFCH is used to transmit IUC.

[0093] Figure 1EThe diagram illustrates an example of an IUC Information MAC CE for a first IUC scheme in which some example embodiments of the present disclosure may be implemented. The IUC Information MAC CE is identified by a MAC subheader with an LCID as specified in Table 6.2.4-1. The priority of the IUC Information MAC CE is fixed to '1'. It has a variable size and has the following fields: RT (resource set type, i.e., preferred resource set or non-preferred resource set); RSL (location of reference slot); LSI i (lowest subchannel index for the first resource position of each TRIV); RC i (resource combination); first resource location i-1 (first resource position) and R (reserved bit).

[0094] Figure 1F The diagram illustrates an example of an IUC Request MAC CE for a first IUC scenario, in which some example embodiments of the present disclosure may be implemented. The IUC Request MAC CE is identified by a MAC subheader with an LCID as specified in Table 6.2.4-1. The priority of the IUC Request MAC CE is fixed to '1'. It has a variable size and contains the following fields: RT (resource set type, i.e., preferred resource set or non-preferred resource set); RP (resource reservation period); priority (priority); RSWL (resource selection window position); number of subchannels (number of subchannels); and R (reserved bit).

[0095] As mentioned above, in RAN2#119bis-e, it was agreed that the SL-U should support a persistent LBT failure detection procedure. SL-specific persistent LBT failure detection (and recovery procedures) are device-centric events and therefore have an impact on any process in which two or more devices interact. For example, SL-specific persistent LBT failures may have an impact on the HARQ feedback process, which can be illustrated in the following use case.

[0096] In use case (a), the Tx UE is experiencing persistent LBT failures in specific RB sets (or resource pools) and is therefore blocked from accessing these specific RB sets (or resource pools). In sub-use case (ai), the Rx UE is experiencing persistent LBT failures in the same RB set (or resource pool) as the Tx UE. In sub-use case (a.ii), the Rx UE is not experiencing persistent LBT failures in the same RB set (or resource pool) as the Tx UE.

[0097] In use case (b), the Tx UE is not experiencing persistent LBT failure in a particular RB set (or resource pool), and therefore it is able to access resources in the RB set (or resource pool), for example by successfully performing LBT (type 1 or 2, depending on whether COT is available), and sends its PSCCH / PSSCH transmission with the associated SCI requesting HARQ feedback for the PSCCH / PSSCH transmission via the PSFCH resources mapped to the PSCCH / PSSCH resources. In sub-use case (bi), the Rx UE is not experiencing persistent LBT failure in the RB set (or resource pool) to which the PSFCH is mapped, and therefore the Rx UE is able to provide HARQ feedback using the mapped PSFCH resources. In sub-use case (b.ii), the Rx UE is experiencing persistent LBT failure in the RB set (or resource pool) to which the PSFCH is mapped, and therefore is unable to access the mapped PSFCH resources to provide HARQ feedback.

[0098] From these use cases, it can be seen that whenever use case (b.ii) occurs, the Tx UE will not know whether HARQ retransmission should be performed, so the communication cannot be assumed to be reliable. In this disclosure, a solution is provided to deal with the persistent LBT failure situation. This will be combined with Figure 2-Figure 8 Provide a description.

[0099] Figure 2 A flow chart is shown illustrating a communication process 200 according to some example embodiments of the present disclosure. For discussion purposes, reference will be made to Figure 1A Describes the communication process 200. It should be understood that although reference has been made to Figure 1A The communication process 200 is described with reference to the network environment 100, but the communication process 200 can also be applied to other similar communication scenarios.

[0100] In the communication process 200, the first terminal device 120-1 determines 202 that a persistent (LBT) failure on a sidelink resource set is detected. The first terminal device 120-1 sends information 206 related to the persistent LBT failure to at least one of the second terminal device 120-2 or the network device 110.

[0101] In some example embodiments, first terminal device 120-1 sends (204) information 206 related to a persistent LBT failure to network device 110. Network device 110 receives (208) information 206 from first terminal device 120-1 and sends (210) second information 212 determined based on information 206 to second terminal device 120-2. Second terminal device 120-2 receives (214) second information 212 from network device 110. Second terminal device 120-2 sends (220) at least one sidelink transmission 222 on at least one sidelink resource determined based on received second information 212.

[0102] Alternatively or additionally, the first terminal device 120-1 sends (216) information 206 related to the persistent LBT failure to the second terminal device 120-2. The second terminal device 120-2 receives (218) the information 206 from the first terminal device 120-1. The second terminal device 120-2 sends (220) at least one sidelink transmission 222 on at least one sidelink resource determined based on the received information 206.

[0103] In some example embodiments, information 206 may include an indication that a persistent LBT failure is detected on a set of sidelink resources. In other words, the second terminal device 120-2 or network device 110 that receives information 206 may know the occurrence of a persistent LBT failure on the first terminal device 120-1. Alternatively or additionally, information 206 may include an indication of the duration of the persistent LBT failure. In other words, the second terminal device 120-2 or network device 110 that receives information 206 may know how long the persistent LBT failure on the first terminal device 120-1 will last. Alternatively or additionally, information 206 may include an indication of a set of sidelink resources. In other words, the second terminal device 120-2 or network device 110 that receives information 206 may know on which sidelink resources the persistent LBT failure occurs.

[0104] In some example embodiments, the sidelink resource set may include at least one resource block (RB) set. Alternatively or additionally, the sidelink resource set may include at least one resource pool. Alternatively or additionally, the sidelink resource set may include at least one bandwidth part (BWP).

[0105] In some example embodiments, first terminal device 120-1 may send information 206 to network device 110 based on a determination that first terminal device 120-1 is within coverage of network device 110. In some example embodiments, network device 110 may send second information 212 to second terminal device 120-2 based on a determination that second terminal device 120-2 is within coverage of network device 110.

[0106] In some example embodiments, second information 212 may include an indication that a persistent LBT failure was detected on a sidelink resource set. Alternatively or additionally, second information 212 may include an indication of the duration of the persistent LBT failure. Alternatively or additionally, second information 212 may include an indication of the sidelink resource set. In other words, network device 110 may forward the contents of information 206 to second terminal device 120-2. In some example embodiments, network device 110 may send second information 212 to second terminal device 120-2 based on determining that second terminal device 120-2 is in the second resource allocation mode. In this way, second terminal device 120-2 may be aware of information related to the persistent LBT failure that occurred on first terminal device 120-1 and may therefore be able to determine at least one sidelink resource to use for at least one sidelink transmission 222.

[0107] In some example embodiments, second information 212 may include an indication of at least one sidelink resource allocated for at least one sidelink transmission 222 to be sent from second terminal device 120-2 to first terminal device 120-1. In some example embodiments, prior to receiving second information 212 from network device 110, based on determining that second terminal device 120-2 is in the first resource allocation mode, second terminal device 120-2 may send a request to network device 110 for allocation of resources for at least one sidelink transmission 222. Based on receiving the request, network device 110 may determine the at least one sidelink resource allocated for at least one sidelink transmission 222.

[0108] In some example embodiments, based on determining that first terminal device 120-1 is out of coverage of network device 110, first terminal device 120-1 may transmit information 206 to second terminal device 120-2. In other words, when first terminal device 120-1 is not under network control, first terminal device 120-1 may transmit information 206 to second terminal device 120-2. In some example embodiments, when first terminal device 120-1 is within coverage of network device 110, first terminal device 120-1 may transmit information 206 to second terminal device 120-2. In other words, regardless of whether first terminal device 120-1 is under network control, first terminal device 120-1 may always transmit information 206 to second terminal device 120-2. In this way, second terminal device 120-2 may be aware of information related to the persistent LBT failure occurring on first terminal device 120-1 and may therefore be able to determine at least one sidelink resource for at least one sidelink transmission 222.

[0109] In some example embodiments, when sending information 206 to second terminal device 120-2, first terminal device 120-1 may send an IUC message including the information based on determining an IUC between first terminal device 120-1 and second terminal device 120-2. In some example embodiments, the IUC message may include an indication of including non-preferred resources of the sidelink resource set. Alternatively or additionally, the IUC message may include an indication of excluding preferred resources from the sidelink resource set.

[0110] In some example embodiments, when sending information 206 to the second terminal device 120-2, the first terminal device 120-1 may send PC5 radio resource control (PC5-RRC) UE assistance information (UAI) including the information based on determining that there is no IUC between the first terminal device 120-1 and the second terminal device 120-2. Alternatively or additionally, the first terminal device 120-1 may send a media access control (MAC) control element (CE) including the information based on determining that there is no IUC between the first terminal device 120-1 and the second terminal device 120-2. For example, based on determining that a unicast link is established between the first terminal device 120-1 and the second terminal device 120-2, the first terminal device 120-1 may send a PC5-RRC including the information. Alternatively or additionally, based on determining that a unicast link is established between the first terminal device 120-1 and the second terminal device 120-2, the first terminal device 120-1 may send a MAC CE including the information. Alternatively or additionally, based on determining that a multicast link is established between the first terminal device 120 - 1 and the second terminal device 120 - 2 , the first terminal device 120 - 1 may send a MAC CE including this information.

[0111] In some example embodiments, the set of sidelink resources may be a first resource pool.The information 206 may be sent to the second terminal device 120-2 in a second resource pool different from the first resource pool, and the information 206 may include an indication of the first resource pool.

[0112] In some example embodiments, at least one sidelink resource determined by second terminal device 120-2 or allocated by network device 110 may be mapped to at least one PSFCH resource that is different from the sidelink resource set. In some example embodiments, when the at least one sidelink resource is allocated by network device 110, second information 212 may include an indication of enabling HARQ feedback for at least one sidelink transmission 222 from first terminal device 120-1 to second terminal device 120-2. In some example embodiments, second terminal device 120-2 may send an indication of enabling HARQ feedback for at least one sidelink transmission 222 to first terminal device 120-1. In some example embodiments, first terminal device 120-1 may receive (224) at least one sidelink transmission 222 from second terminal device 120-2 on the at least one sidelink resource and send HARQ feedback for the at least one sidelink transmission to second terminal device 120-2.

[0113] In some example embodiments, at least one sidelink resource determined by second terminal device 120-2 or allocated by network device 110 may be mapped to at least one PSFCH resource in the sidelink resource set. In some example embodiments, when the at least one sidelink resource is allocated by network device 110, second information 212 may include an indication to disable HARQ feedback from first terminal device 120-1 to second terminal device 120-2 for at least one sidelink transmission 222. In some example embodiments, second terminal device 120-2 may send an indication to first terminal device 120-1 to disable HARQ feedback for at least one sidelink transmission 222. In some example embodiments, first terminal device 120-1 may receive (224) the at least one sidelink transmission 222 from second terminal device 120-2 on the at least one sidelink resource and skip sending HARQ feedback for the at least one sidelink transmission to second terminal device 120-2.

[0114] In some example embodiments, when transmitting at least one sidelink transmission 222 on at least one sidelink resource mapped to at least one PSFCH resource in the sidelink resource set, second terminal device 120-2 may reduce a modulation and coding scheme (MCS) of at least one sidelink transmission 222. Alternatively or additionally, second terminal device 120-2 may enable repetition of at least one sidelink transmission 222. In some example embodiments, second information 212 may include an indication of a reduced MCS for at least one sidelink transmission 222. Alternatively or additionally, second information 212 may include an indication of a repetition of at least one sidelink transmission.

[0115] Through the process flow 200, the second terminal device 120-2 may be aware of information related to the persistent LBT failure on the first terminal device 120-1. Therefore, when sending a sidelink transmission to the first terminal device 120-1, the second terminal device 120-2 may be able to cope with the persistent LBT failure.

[0116] For example, the second terminal device 120-2 may send a sidelink transmission to the first terminal device 120-1 on a resource that is mapped to at least one PSFCH resource in which the first terminal device 120-1 is not experiencing a persistent LBT failure. In this case, the second terminal device 120-2 may be able to provide HARQ feedback using the mapped PSFCH resource, and the first terminal device 120-1 will know whether it should perform a HARQ retransmission.

[0117] Alternatively, the second terminal device 120-2 may send a sidelink transmission to the first terminal device 120-1 on a resource mapped to at least one PSFCH resource, in which resource the first terminal device 120-1 is not experiencing a persistent LBT failure. In this case, the second terminal device 120-2 will not require the first terminal device 120-1 to provide HARQ feedback, and the second terminal device 120-2 may increase the robustness of the transmission, for example, by reducing the MCS or enabling repetitions for the sidelink transmission, thereby increasing the probability of reception.

[0118] In other words, by considering whether the first terminal device 120-1 is experiencing a persistent LBT failure in the target RB set (or resource pool), the second terminal device 120-2 may be able to cope with the lack of HARQ feedback. In this way, the reliability of sidelink communications may be improved even in the event of a persistent LBT failure.

[0119] Figure 3 A flow chart is shown illustrating a process 300 for different scenarios of the behavior of the first terminal device 120-1 according to some example embodiments of the present disclosure. For the purpose of discussion, reference will be made to Figure 1A describe Figure 3 Example of .

[0120] As an example implementation, in process 300, at 301, Rx UE 120-1 may experience and report a persistent LBT failure. For example, after experiencing a persistent LBT failure, Rx UE 120-1 may indicate to its peer that it is experiencing a persistent LBT failure. At 302, it may be determined whether Rx UE 120-1 is within the coverage of gNB 110. If Rx UE 120-1 is outside the coverage of gNB 110 ("No" at 302), process 300 may continue to block 303, and Rx UE 120-1 may indicate to Tx UE 120-2 that it is experiencing a persistent LBT failure. At 303, it may be determined whether an IUC exists between Rx UE 120-1 and Tx UE 120-2. If there is no IUC between Rx UE 120-1 and Tx UE 120-2 ("NO" at 303), process 300 may proceed to block 304. At 304, it may be determined whether a unicast link or a broadcast link is established between Rx UE 120-1 and Tx UE 120-2.

[0121] In some example embodiments, if a unicast link is established between Rx UE 120-1 and Tx UE 120-2, process 300 may proceed to block 305. At 305, Rx UE 120-1 may indicate in a PC5-RRC UAI or MAC-CE that a persistent LBT failure has occurred in a specific RB and its duration. In other words, when Rx UE 120-1 is in a non-NW controlled setting (i.e., out of coverage and using Mode 2) and without inter-UE coordination, for unicast, Rx UE 120-1 may indicate to Tx UE 120-2 via a PC5-RRC UAI message or MAC CE that it is experiencing a persistent LBT failure in a specific RB set (and resource pool) and its duration (or an estimate of the duration). For example, a MAC CE may be sent outside the affected RB set, which may occur in a different resource pool. In the case where LBT persistent failure is declared at the resource pool level, the working assumption may be that the restriction that MAC CEs must be sent on the same resource pool is relaxed in the context of the SL-U MAC specification. In other words, the MAC CE will need to include information about which resource pool the information in the MAC CE is related to.

[0122] In some example embodiments, if a multicast link is established between Rx UE 120-1 and Tx UE 120-2, process 300 may proceed to block 306. At 306, Rx UE 120-1 may indicate a persistent LBT failure occurring in a specific RB and its duration using a MAC-CE. In other words, when Rx UE 120-1 is in a non-NW controlled setting (i.e., out of coverage and using Mode 2) and without inter-UE coordination, for multicast, Rx UE 120-1 may indicate to Tx UE 120-2 via a MAC CE that it is experiencing a persistent LBT failure in a specific RB set (and resource pool) and its duration (or an estimate of the duration). For example, the MAC CE may be sent outside the affected RB set, which may occur in different resource pools. Similar to the unicast case, in the case where a persistent LBT failure is declared at the resource pool level, the restriction that the MAC CE must be sent on the same resource pool is relaxed in the context of the SL-U MAC specification. In other words, the MAC CE will need to include information about which resource pool the information in the MAC CE is related to.

[0123] In some example embodiments, if there is IUC between Rx UE 120-1 and Tx UE 120-2 ("YES" at 303), process 300 may proceed to block 307. At 307, Rx UE 120-1 may use an IUC message to indicate preferred or non-preferred RB sets to avoid RB sets in which Rx UE 120-1 is experiencing persistent LBT failures. In other words, when Rx UE 120-1 is in a non-NW controlled setting with IUC (i.e., out of coverage and using Mode 2, and with inter-UE coordination), when Rx UE 120-1 plays the role of UE-A in the IUC framework, Rx UE 120-1 may indicate all RB sets in which it is currently experiencing persistent LBT failures as non-preferred resources. Alternatively, Rx UE 120-1 may indicate all RB sets in which it is not currently experiencing persistent LBT failures as preferred resources.

[0124] In some example embodiments, the IUC message exchange may occur on resources where the persistent LBT failure is not declared. The IUC message may also indicate the RB set as non-preferred PSCCH / PSSCH resources, which are those resources associated with PSFCH that would be in the RB set with the persistent LBT failure.

[0125] In some example embodiments, if an LBT persistent failure is declared at the resource pool level, it is assumed that the IUC framework is extended so that it can be sent in resource pools other than the resource pool to which the non-preferred resources are associated. In other words, an IUC message associated with resource pool A can be sent using resources in resource pool B. This extension means that the IUC message needs to include the relevant resource pool ID in its payload.

[0126] In some example embodiments, if Rx UE 120-1 is within the coverage of gNB 110 ("YES" at 302), process 300 may proceed to block 308. At 308, Rx UE 120-1 may send an indication of the persistent LBT failure to gNB 110 (e.g., via an RRC message in a PUSCH or a MAC-CE). At 309, it may be determined whether Tx UE 120-2 is within the coverage of gNB 110. If Tx UE 120-2 is within the coverage of gNB 110 ("YES" at 309), then at 310, it may be determined whether Tx UE 120-2 is in Mode 1 or Mode 2. If Tx UE 120-2 is in Mode 2, gNB 110 may forward the indication received from Rx UE 120-1 to Tx UE 120-2.

[0127] In other words, when Tx UE 120-2 is in a non-NW controlled setting, where both Rx UE 120-1 and Tx UE 120-2 are within coverage, but Tx UE 120-2 uses mode 2, Rx UE 120-1 may send an indication of persistent LBT failure to gNB 110 (e.g., via an RRC message or MAC-CE in PUSCH) after experiencing consecutive LBT failures, and gNB 110 may then forward the indication to Tx UE 120-2.

[0128] Alternatively or additionally, when Rx UE 120-1 is in NW coverage, Rx UE 120-1 may directly send the indication to Tx UE 120-2. In some example embodiments, any implementation of Rx UE 120-1 being out of coverage in a non-NW controlled setting may also be applied to embodiments where Rx UE 120-1 is in coverage. This is particularly effective for the case where only Rx UE 120-1 is in NW coverage and the Tx UE is out of NW coverage (i.e., "No" at 309).

[0129] In some example embodiments, if Tx UE 120-2 is in Mode 1, then upon a resource request from Tx UE 120-2, gNB 110 may allocate PSSCH / PSCCH resources mapped to PSFCH resources in which Rx UE 120-1 is not experiencing a persistent LBT failure at 312. Alternatively, gNB 110 may indicate disabling of HARQ feedback for the allocated PSSCH / PSCCH resources mapped to PSFCH resources in which Rx UE 120-1 is experiencing a persistent LBT failure.

[0130] In other words, when Tx UE 120-2 is in an NW control setting (i.e., within NW coverage and using Mode 1), for both unicast and multicast, after Tx UE 120-2 requests resources to transmit to Rx UE 120-1, gNB 110 (if it has received an indication of a persistent LBT failure from Rx UE 120-1) may allocate resources mapped to PSFCH locations in which Rx UE 120-1 is not experiencing a persistent LBT failure. Alternatively, gNB 110 may disable HARQ feedback for transmissions allocated in resources mapped to PSFCH locations affected by a persistent LBT failure.

[0131] In some embodiments, Rx UE 120-1 may send an indication of the experienced persistent LBT failure over a Uu interface (e.g., via an RRC message or MAC-CE in a PUSCH) to gNB 110. Alternatively or additionally, Rx UE 120-1 may send an indication of the experienced persistent LBT failure to Tx UE 120-2 over SL resources (i.e., over RB sets or resource pools) in which no persistent LBT failure is experienced.

[0132] From the perspective of Tx UE 120-2, after acquiring information about the persistent LBT failure occurring in RX UE 120-1, Tx UE 120-2 may send a sidelink transmission to Rx UE 120-1 based on the acquired information.

[0133] In some example embodiments, when Tx UE 120-2 is in non-NW control mode (i.e., Mode 2), or when Rx UE 120-1 is outside NW coverage, Tx UE 120-2 may determine which PSCCH / PSSCH resources are mapped to the PSFCH in the RB set (or resource pool) affected by the persistent LBT failure. In some example embodiments, Tx UE 120-2 may exclude the determined PSCCH / PSSCH resources from the resource selection process. In other words, Tx UE 120-2 may not use these determined PSCCH / PSSCH resources for transmission, otherwise it would be impossible to determine whether Rx UE 120-1 has received the transmission.

[0134] In some example embodiments, if Tx UE 120-2 utilizes the determined PSCCH / PSSCH resources, Tx UE 120-2 may disable HARQ feedback. Additionally, Tx UE 120-2 may also increase the robustness of the transmission, for example, by reducing the MCS or enabling repetitions for transmissions to Rx UE 120-1 to increase the probability of reception.

[0135] In some example embodiments, when Tx UE 120-2 is in NW control mode (i.e., Mode 1), Tx UE 120-2 may follow resource allocations provided by gNB 110. For example, Tx UE 120-2 may utilize resources allocated by gNB 110 for sidelink transmissions to Rx UE 110, which are mapped to PSFCH locations where Rx UE 110 is not experiencing a persistent LBT failure. Since Rx UE 110 is not experiencing a persistent LBT failure at the mapped PSFCH locations, Rx UE 110 may provide HARQ feedback to Tx UE 120-2, and Tx UE 120-2 may know whether HARQ retransmissions are required. Alternatively, based on the indication received from gNB 110, Tx UE 120-2 may disable HARQ feedback for transmissions allocated in resources mapped to the PSFCH location affected by the persistent LBT failure and may increase the robustness of the transmission, e.g., by reducing the MCS or enabling repetitions for transmissions to the RX UE to increase the probability of reception.

[0136] In other words, by considering whether Rx UE 120-1 is experiencing persistent LBT failure in the target RB set (or resource pool), Tx UE 120-2 may be able to cope with the lack of HARQ feedback. In this way, the reliability of sidelink communications may be improved even in the event of persistent LBT failure.

[0137] Figure 4 FIGURE 4 is a flow chart illustrating an example method 400 implemented at a first terminal device according to some example embodiments of the present disclosure. For the purpose of discussion, reference will be made to Figure 1A The method 400 is described from the perspective of the first terminal device 120 .

[0138] At block 410, the first terminal device 120-1 determines that a persistent LBT failure on the sidelink resource set is detected. At block 420, the first terminal device 120-1 sends information related to the persistent LBT failure to the network device 110. Alternatively or additionally, the first terminal device 120-1 sends information related to the persistent LBT failure to the second terminal device 120-2.

[0139] In some example embodiments, when sending the information to second terminal device 120-2, first terminal device 120-1 may send the information to second terminal device 120-2 based on determining that first terminal device 120-1 is outside the coverage of network device 110. In some example embodiments, first terminal device 120-1 may send an IUC message including the information based on determining that an IUC exists between first terminal device 120-1 and second terminal device 120-2. In some example embodiments, the information may include an indication of including non-preferred resources in the sidelink resource set. Alternatively or additionally, the information may include an indication of excluding preferred resources from the sidelink resource set.

[0140] In some example embodiments, based on determining that there is no IUC between first terminal device 120-1 and second terminal device 120-2, first terminal device 120-1 may send a PC5-RRC UAI including this information. Alternatively or additionally, based on determining that there is no IUC between first terminal device 120-1 and second terminal device 120-2, first terminal device 120-1 may send a MAC CE including this information.

[0141] In some example embodiments, based on determining that a unicast link is established between first terminal device 120-1 and second terminal device 120-2, first terminal device 120-1 may send a PC5-RRC UAI. Alternatively or additionally, based on determining that a unicast link is established between first terminal device 120-1 and second terminal device 120-2, first terminal device 120-1 may send a MAC CE. In some example embodiments, based on determining that a group link is established between first terminal device 120-1 and second terminal device 120-2, first terminal device 120-1 may send a MAC CE.

[0142] In some example embodiments, the set of sidelink resources may be a first resource pool.The information may be sent to the second terminal device 120-2 in a second resource pool different from the first resource pool, and the information may include an indication of the first resource pool.

[0143] In some example embodiments, first terminal device 120 - 1 may send the information to network device 110 based on determining that first terminal device 120 - 1 is within coverage of network device 110 .

[0144] In some example embodiments, the information may include an indication that a persistent LBT failure was detected on a sidelink resource set. Alternatively or additionally, the information may include an indication of a duration of the persistent LBT failure. Alternatively or additionally, the information may include an indication of a sidelink resource set.

[0145] In some example embodiments, first terminal device 120-1 may also receive at least one sidelink transmission from second terminal device 120-2 on at least one sidelink resource determined based on the information.

[0146] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource that is different from the sidelink resource set.The first terminal device 120-1 may also send HARQ feedback for the at least one sidelink transmission to the second terminal device 120-2.

[0147] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource in the sidelink resource set.The first terminal device 120-1 may also receive an indication from the second terminal device 120-2 to de-enable HARQ feedback from the first terminal device 120-1 to the second terminal device 120-2 for the at least one sidelink transmission.

[0148] In some example embodiments, the sidelink resource set may include at least one resource block (RB) set. Alternatively or additionally, the sidelink resource set may include at least one resource pool. Alternatively or additionally, the sidelink resource set may include at least one bandwidth portion.

[0149] Figure 5 Another flow chart of an example method 500 implemented at a network device according to some example embodiments of the present disclosure is illustrated. For discussion purposes, reference will be made to Figure 1A The method 500 is described from the perspective of the second terminal device 120 - 2 .

[0150] At block 510, the second terminal device 120-2 receives information related to a persistent LBT failure detected by the first terminal device 120-1 on a set of sidelink resources. At block 520, the second terminal device 120-2 sends at least one sidelink transmission to the first terminal device 120-1 on at least one sidelink resource determined based on the received information.

[0151] In some example embodiments, the information may include an indication that a persistent LBT failure has been detected on a sidelink resource set. Alternatively or additionally, the information may include an indication of a duration of the persistent LBT failure. Alternatively or additionally, the information may include an indication of a sidelink resource set. Alternatively or additionally, the information may include an indication of a non-preferred resource included in the sidelink resource set. Alternatively or additionally, the information may include an indication of a preferred resource excluded from the sidelink resource set.

[0152] In some example embodiments, the information may be received from first terminal device 120-1. Alternatively or additionally, the information may be received from network device 110. In some example embodiments, when first terminal device 120-1 and second terminal device 120-2 are within coverage of network device 110, the information may be received from network device 110. In some example embodiments, when at least one of first terminal device 120-1 and second terminal device 120-2 is outside coverage of network device 110, the information may be received from first terminal device 120-1.

[0153] In some example embodiments, the information may be received from first terminal device 120-1 via PC5-RRC UAI. Alternatively or additionally, the information may be received from first terminal device 120-1 via MAC CE. Alternatively or additionally, the information may be received from first terminal device 120-1 via an IUC message.

[0154] In some example embodiments, the information may include an indication of the at least one sidelink resource, and the information is received from network device 110. In some example embodiments, prior to receiving the information from network device 110, second terminal device 120-2 may send a request to network device 110 for allocation of resources for the at least one sidelink transmission based on determining that second terminal device 120-2 is in the first resource allocation mode.

[0155] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource that is different from the sidelink resource set.The second terminal device 120-2 may also send an indication to the first terminal device 120-1 enabling HARQ feedback from the first terminal device 120-1 to the second terminal device 120-2 for the at least one sidelink transmission.

[0156] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource in the sidelink resource set.The second terminal device 120-2 may also send an indication to the first terminal device 120-1 to enable HARQ feedback from the first terminal device 120-1 to the second terminal device 120-2 for the at least one sidelink transmission.

[0157] In some example embodiments, second terminal device 120-2 may be caused to transmit at least one sidelink transmission by reducing a modulation and coding scheme (MCS) of the at least one sidelink transmission. Alternatively or additionally, second terminal device 120-2 may be caused to transmit at least one sidelink transmission by enabling repetition of the at least one sidelink transmission.

[0158] In some example embodiments, the sidelink resource set may include at least one resource block (RB) set. Alternatively or additionally, the sidelink resource set may include at least one resource pool. Alternatively or additionally, the sidelink resource set may include at least one bandwidth portion.

[0159] In some example embodiments, the set of sidelink resources may be a first resource pool.The information may be received from the first terminal device 120-1 in a second resource pool different from the first resource pool, and the information may include an indication of the first resource pool.

[0160] Figure 6 Another flow chart of an example method 600 implemented at a network device according to some example embodiments of the present disclosure is illustrated. For discussion purposes, reference will be made to Figure 1A Method 600 is described from the perspective of network device 110 .

[0161] At block 610, network device 110 receives first information related to a persistent LBT failure detected by first terminal device 120-1 on a sidelink resource set from first terminal device 120-1. At block 620, network device 110 sends second information determined based on the first information to second terminal device 120-2.

[0162] In some example embodiments, the information may include an indication that a persistent LBT failure was detected on a sidelink resource set. Alternatively or additionally, the information may include an indication of a duration of the persistent LBT failure. Alternatively or additionally, the information may include an indication of a sidelink resource set.

[0163] In some example embodiments, the sidelink resource set may include at least one resource block (RB) set. Alternatively or additionally, the sidelink resource set may include at least one resource pool. Alternatively or additionally, the sidelink resource set may include at least one bandwidth portion. In some example embodiments, when first terminal device 120-1 is within coverage of network device 110, the first information may be received from first terminal device 120-1.

[0164] In some example embodiments, when transmitting the second information to second terminal device 120 - 2 , network device 110 may transmit the second information to second terminal device 120 - 2 based on determining that second terminal device 120 - 2 is within coverage of network device 110 .

[0165] In some example embodiments, the second information may include an indication that a persistent LBT failure was detected on a sidelink resource set. Alternatively or additionally, the second information may include an indication of a duration of the persistent LBT failure. Alternatively or additionally, the second information may include an indication of a sidelink resource set.

[0166] In some example embodiments, when sending the second information to second terminal device 120 - 2 , network device 110 may send the second information to second terminal device 120 - 2 based on determining that second terminal device 120 - 2 is in the second resource allocation mode.

[0167] In some example embodiments, the second information may include an indication of at least one sidelink resource allocated for at least one sidelink transmission to be sent from second terminal device 120-2 to first terminal device 120-1. In some example embodiments, network device 110 may determine the at least one sidelink resource allocated for the at least one sidelink transmission based on receiving a request for resources for sending the at least one sidelink transmission. In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource that is different from the sidelink resource set.

[0168] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource in a sidelink resource set, and the second information may further include an indication to disable HARQ feedback from the first terminal device 120-1 to the second terminal device 120-2 for the at least one sidelink transmission. In some example embodiments, the second information may further include an indication of a reduced MCS for the at least one sidelink transmission. Alternatively or additionally, the second information may further include an indication of a repetition of the at least one sidelink transmission.

[0169] In some example embodiments, an apparatus capable of executing method 400 (e.g., first terminal device 120) may include components for executing the corresponding steps of method 400. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit system or a software module.

[0170] In some example embodiments, the apparatus includes: means for determining that a persistent listen-before-talk (LBT) failure on a sidelink resource set is detected; and means for sending information related to the persistent LBT failure to at least one of a second terminal device or a network device.

[0171] In some example embodiments, the means for transmitting the information to the second terminal device may include: means for transmitting the information to the second terminal device based on determining that the first terminal device is outside the coverage of the network device. In some example embodiments, the apparatus may further include means for transmitting an IUC message including the information based on determining that an IUC exists between the first terminal device and the second terminal device.

[0172] In some example embodiments, the information may comprise an indication of non-preferred resources that include the sidelink resource set. Alternatively or additionally, the information may comprise an indication of preferred resources that exclude the sidelink resource set.

[0173] In some example embodiments, the apparatus may further include: means for transmitting at least one of a PC5-RRC UAI or a MAC CE, wherein the at least one of the PC5-RRC UAI or the MAC CE includes the information. In some example embodiments, the apparatus may further include: means for transmitting at least one of the PC5-RRC UAI or the MAC CE based on determining that a unicast link is established between the first terminal device and the second terminal device. In some example embodiments, the apparatus may further include: means for transmitting the MAC CE based on determining that a multicast link is established between the first terminal device and the second terminal device.

[0174] In some example embodiments, the sidelink resource set may be a first resource pool.The means for sending the information may comprise means for sending the information to the second terminal device in a second resource pool different from the first resource pool, and the information may comprise an indication of the first resource pool.

[0175] In some example embodiments, the means for sending the information to the network device may include means for sending the information to the network device based on determining that the first terminal device is within coverage of the network device.

[0176] In some example embodiments, the information may include an indication that a persistent LBT failure was detected on a sidelink resource set. Alternatively or additionally, the information may include an indication of a duration of the persistent LBT failure. Alternatively or additionally, the information may include an indication of a sidelink resource set.

[0177] In some example embodiments, the apparatus may further include means for receiving at least one sidelink transmission from the second terminal device on at least one sidelink resource determined based on the information. In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource different from the sidelink resource set. The apparatus may further include means for sending HARQ feedback for the at least one sidelink transmission to the second terminal device.

[0178] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource in the sidelink resource set.The apparatus may further comprise: means for receiving, from the second terminal device, an indication to disable HARQ feedback from the first terminal device to the second terminal device for the at least one sidelink transmission.

[0179] In some example embodiments, the sidelink resource set may include at least one resource block (RB) set. Alternatively or additionally, the sidelink resource set may include at least one resource pool. Alternatively or additionally, the sidelink resource set may include at least one bandwidth portion.

[0180] In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of method 400. In some example embodiments, the means comprises at least one processor and at least one memory comprising computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, enable execution of the apparatus.

[0181] In some example embodiments, an apparatus capable of executing method 500 (e.g., second terminal device 120-2) may include components for executing corresponding steps of method 500. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit system or a software module.

[0182] In some example embodiments, the apparatus includes: means for receiving information relating to a persistent listen-before-talk (LBT) failure detected by a first terminal device on a set of sidelink resources; and means for sending at least one sidelink transmission to the first terminal device on at least one sidelink resource determined based on the received information.

[0183] In some example embodiments, the information may include an indication that a persistent LBT failure has been detected on a sidelink resource set. Alternatively or additionally, the information may include an indication of a duration of the persistent LBT failure. Alternatively or additionally, the information may include an indication of a sidelink resource set. Alternatively or additionally, the information may include an indication of a non-preferred resource included in the sidelink resource set. Alternatively or additionally, the information may include an indication of a preferred resource excluded from the sidelink resource set.

[0184] In some example embodiments, the means for receiving the information may include means for receiving the information from at least one of the first terminal device or the network device. In some example embodiments, the means for receiving the information from the network device may include means for receiving the information from the network device when the first terminal device and the second terminal device are within coverage of the network device. In some example embodiments, the means for receiving the information from the first terminal device may include means for receiving the information from the first terminal device when at least one of the first terminal device and the second terminal device is outside coverage of the network device.

[0185] In some example embodiments, the means for receiving the information from the first terminal device may include means for receiving the information from the first terminal device via at least one of a PC5-RRC UAI, a MAC CE, or an IUC message.

[0186] In some example embodiments, the information may include an indication of at least one sidelink resource, and the means for receiving the information may include means for receiving the information from the network device. In some example embodiments, the apparatus may further include means for sending a request to the network device for allocation of resources for the at least one sidelink transmission based on determining that the second terminal device is in the first resource allocation mode prior to receiving the information from the network device.

[0187] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource that is different from the sidelink resource set. The apparatus may also include means for sending an indication to the first terminal device enabling HARQ feedback from the first terminal device to the second terminal device for the at least one sidelink transmission.

[0188] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource in the sidelink resource set.The apparatus may further comprise: means for sending an indication to the first terminal device to enable HARQ feedback from the first terminal device to the second terminal device for the at least one sidelink transmission.

[0189] In some example embodiments, the means for sending at least one sidelink transmission may include means for sending at least one sidelink transmission by at least one of: reducing a modulation and coding scheme (MCS) of the at least one sidelink transmission, or enabling repetition of the at least one sidelink transmission.

[0190] In some example embodiments, the sidelink resource set may include at least one of: at least one resource block (RB) set, at least one resource pool, or at least one bandwidth part.

[0191] In some example embodiments, the set of sidelink resources may be a first resource pool.The means for receiving the information may comprise means for receiving the information from the first terminal device in a second resource pool different from the first resource pool, and the information may comprise an indication of the first resource pool.

[0192] In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of method 500. In some example embodiments, the means comprises at least one processor and at least one memory comprising computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, enable execution of the apparatus.

[0193] In some example embodiments, an apparatus capable of performing method 600 (e.g., network device 110) may include components for performing the corresponding steps of method 600. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit system or a software module.

[0194] In some example embodiments, the apparatus includes: a component for receiving first information related to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a sidelink resource set from a first terminal device; and a component for sending second information determined based on the first information to a second terminal device.

[0195] In some example embodiments, the information may include an indication that a persistent LBT failure was detected on a sidelink resource set. Alternatively or additionally, the information may include an indication of a duration of the persistent LBT failure. Alternatively or additionally, the information may include an indication of a sidelink resource set.

[0196] In some example embodiments, the sidelink resource set may include at least one resource block (RB) set. Alternatively or additionally, the sidelink resource set may include at least one resource pool. Alternatively or additionally, the sidelink resource set may include at least one bandwidth portion. In some example embodiments, the means for receiving the first information may include means for receiving the first information from the first terminal device when the first terminal device is within coverage of the network device.

[0197] In some example embodiments, the means for sending the second information to the second terminal device may include means for sending the second information to the second terminal device based on determining that the second terminal device is within coverage of the network device.

[0198] In some example embodiments, the second information may include an indication that a persistent LBT failure was detected on a sidelink resource set. Alternatively or additionally, the second information may include an indication of a duration of the persistent LBT failure. Alternatively or additionally, the second information may include an indication of a sidelink resource set.

[0199] In some example embodiments, the means for sending the second information to the second terminal device may include means for sending the second information to the second terminal device based on determining that the second terminal device is in the second resource allocation mode.

[0200] In some example embodiments, the second information may include an indication of at least one sidelink resource allocated for at least one sidelink transmission to be sent from the second terminal device to the first terminal device. In some example embodiments, the apparatus may further include means for determining, based on receiving a request for resources for sending the at least one sidelink transmission, the at least one sidelink resource allocated for the at least one sidelink transmission. In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource that is different from the sidelink resource set.

[0201] In some example embodiments, the at least one sidelink resource may be mapped to at least one PSFCH resource in a sidelink resource set, and the second information may further include an indication to disable HARQ feedback from the first terminal device to the second terminal device for the at least one sidelink transmission. In some example embodiments, the second information may further include an indication of a reduced MCS for the at least one sidelink transmission. Alternatively or additionally, the second information may further include an indication of a repetition of the at least one sidelink transmission.

[0202] In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of method 600. In some example embodiments, the means comprises at least one processor and at least one memory comprising computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, enable execution of the apparatus.

[0203] Figure 7 1 illustrates a simplified block diagram of a device 700 suitable for implementing some example embodiments of the present disclosure. The device 700 may be provided to implement a communication device, such as Figure 1A As shown in FIG, the network device 110, the first terminal device 120-1 or the second terminal device 120-2 includes one or more processors 710, one or more memories 720 coupled to the processors 710, and one or more communication modules 740 coupled to the processors 710.

[0204] The communication module 740 is used for two-way communication. The communication module 740 has at least one antenna to facilitate communication. The communication interface can represent any interface required for communication with other network elements.

[0205] Processor 710 can be of any type suitable for the local technology network and, as non-limiting examples, can include one or more of the following: a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 700 can have multiple processors, such as application-specific integrated circuit chips that are time-slave to a clock synchronized with a main processor.

[0206] The memory 720 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 724, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact disks (CDs), digital video disks (DVDs), and other magnetic and / or optical storage devices. Examples of volatile memories include, but are not limited to, random access memory (RAM) 722 and other volatile memories that do not persist during power outages.

[0207] Computer program 730 includes computer executable instructions executed by associated processor 710. Program 730 may be stored in ROM 724. Processor 710 may perform any suitable actions and processes by loading program 730 into RAM 722.

[0208] The embodiments of the present disclosure may be implemented by the program 730 so that the device 700 may execute the following steps: Figure 2 The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0209] In some example embodiments, the program 730 may be tangibly embodied in a computer-readable medium that may be included in the device 700 (such as in the memory 720) or in other storage devices accessible by the device 700. The device 700 may load the program 730 from the computer-readable medium to the RAM 722 for execution. The computer-readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc.

[0210] Figure 8 FIG1 illustrates a block diagram of an example of a computer readable medium 1000 according to some example embodiments of the present disclosure. The computer readable medium 800 has a program 730 stored thereon. It should be noted that although the computer readable medium 800 is Figure 8 Although depicted in the form of a CD or DVD, computer readable medium 800 may be in any other form suitable for carrying or storing program 730.

[0211] In general, the various embodiments of the present disclosure can be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects can be implemented in hardware, while other aspects can be implemented in firmware or software that can be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are illustrated and described as block diagrams, flow charts, or using some other graphical representations, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein can be implemented in hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0212] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, executed in a device on a target real or virtual processor to perform the above-referenced Figure 4 、 Figure 5 or Figure 6 The method 400, 500 or 600 described. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The functions of program modules can be combined or split between program modules as needed in various embodiments. The machine executable instructions for program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in both local and remote storage media.

[0213] The program code for performing the disclosed method can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing apparatus so that the program code, when executed by the processor or controller, enables specific function / operation in flow chart and / or block diagram to be realized. The program code can be executed entirely on a machine, partially on a machine, as an independent software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0214] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform the various processes and operations described above. Examples of carriers include signals, computer-readable media, etc.

[0215] Computer readable medium can be a computer readable signal medium or a computer readable storage medium. Computer readable medium can include but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or equipment or any suitable combination of the foregoing. More specific examples of computer readable storage medium will include an electrical connection with one or more wires, a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device or any suitable combination of the foregoing. The term "non-transient" as used herein is a restriction on the medium itself (i.e., tangible, rather than a signal), rather than a restriction on data storage persistence (e.g., RAM vs. ROM).

[0216] In addition, although operation is described in a particular order, this should not be understood as requiring these operations or all shown operations to be performed in the particular order shown or in sequential order, to achieve desired results. In some cases, multitasking and parallel processing may be advantageous. Equally, although some specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure, but should be interpreted as describing the features that can be specific to a particular embodiment. Some features described in the context of a separate embodiment also can be realized in the combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment also can be realized individually or with any suitable subcombination in multiple embodiments.

[0217] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A first terminal device, comprising: at least one processor; as well as At least one memory storing instructions, which, when executed by the at least one processor, cause the first terminal device to at least: determining that a persistent listen-before-talk (LBT) failure on a sidelink resource set is detected; and Information related to the persistent LBT failure is sent to at least one of a second terminal device or a network device.

2. The first terminal device according to claim 1, wherein the first terminal device is caused to send the information to the second terminal device by: Based on determining that the first terminal device is outside the coverage of the network device, the information is sent to the second terminal device.

3. The first terminal device according to claim 2, wherein the first terminal device is further configured to: Based on determining that inter-UE coordination IUC exists between the first terminal device and the second terminal device, an IUC message including the information is sent.

4. The first terminal device according to claim 3, wherein the information includes at least one of the following items: including an indication of a non-preferred resource of the sidelink resource set; or An indication of a preferred resource excluding the set of sidelink resources.

5. The first terminal device according to claim 2, wherein the first terminal device is further configured to: Based on determining that there is no IUC between the first terminal device and the second terminal device, at least one of PC5 radio resource control PC5-RRC user equipment assistance information UAI or media access control MAC control element CE is sent, wherein the at least one of the PC5-RRC UAI or the MAC CE includes the information.

6. The first terminal device according to claim 5, wherein the first terminal device is further configured to: Based on determining that a unicast link is established between the first terminal device and the second terminal device, at least one of the PC5-RRC UAI or the MAC CE is sent.

7. The first terminal device according to claim 5, wherein the first terminal device is further configured to: Based on determining that a multicast link is established between the first terminal device and the second terminal device, the MAC CE is sent.

8. A first terminal device according to any one of claims 2 to 7, wherein the sidelink resource set is a first resource pool, the information is sent to the second terminal device in a second resource pool different from the first resource pool, and the information includes an indication of the first resource pool.

9. The first terminal device according to claim 1, wherein the first terminal device is caused to send the information to the network device by: Based on determining that the first terminal device is within the coverage of the network device, the information is sent to the network device.

10. The first terminal device according to any one of claims 5 to 9, wherein the information includes at least one of the following items: an indication that the persistent LBT failure is detected on the sidelink resource set; an indication of the duration of the ongoing LBT failure; or An indication of the sidelink resource set.

11. The first terminal device according to any one of claims 1 to 10, wherein the first terminal device is further configured to: At least one sidelink transmission is received from the second terminal device on at least one sidelink resource determined based on the information.

12. A first terminal device according to claim 11, wherein the at least one sidelink resource is mapped to at least one Physical Sidelink Feedback Channel (PSFCH) resource different from the set of sidelink resources, and the first terminal device is further caused to: Send hybrid automatic repeat request (HARQ) feedback for the at least one sidelink transmission to the second terminal device.

13. The first terminal device of claim 11 , wherein the at least one sidelink resource is mapped to at least one PSFCH resource in the sidelink resource set, and the first terminal device is further caused to: An indication is received from the second terminal device to disable HARQ feedback from the first terminal device to the second terminal device for the at least one sidelink transmission.

14. The first terminal device according to any one of claims 1 to 13, wherein the sidelink resource set comprises at least one of the following: At least one resource block (RB) set; at least one resource pool; or At least one bandwidth portion.

15. A second terminal device, comprising: at least one processor; as well as At least one memory storing instructions, which, when executed by the at least one processor, cause the second terminal device to at least: receiving information related to a persistent listen-before-talk (LBT) failure detected by the first terminal device on the sidelink resource set; as well as At least one sidelink transmission is sent to the first terminal device on at least one sidelink resource determined based on the received information.

16. The second terminal device according to claim 15, wherein the information includes at least one of the following items: an indication that the persistent LBT failure is detected on the sidelink resource set; an indication of the duration of the ongoing LBT failure; an indication of the sidelink resource set; including an indication of a non-preferred resource of the sidelink resource set; or An indication of a preferred resource excluding the set of sidelink resources. 17 . The second terminal device according to claim 15 , wherein the information is received from at least one of the first terminal device or a network device. 18 . The second terminal device according to claim 17 , wherein the information is received from the network device in a case where the first terminal device and the second terminal device are within coverage of the network device. 19 . The second terminal device according to claim 17 , wherein the information is received from the first terminal device in a case where at least one of the first terminal device and the second terminal device is out of coverage of the network device.

20. The second terminal device according to claim 17, wherein the information is received from the first terminal device via at least one of the following: PC5 Radio Resource Control PC5-RRC User Equipment Assistance Information UAI; Media Access Control MAC Control Element CE; or Coordinate IUC messages between UEs.

21. The second terminal device of claim 15, wherein the information comprises an indication of the at least one sidelink resource, and the information is received from a network device.

22. The second terminal device according to claim 21, wherein the second terminal device is further configured to: Prior to receiving the information from the network device, based on determining that the second terminal device is in the first resource allocation mode, sending a request to the network device for allocation of resources for the at least one sidelink transmission.

23. A second terminal device according to any one of claims 15 to 22, wherein the at least one sidelink resource is mapped to at least one Physical Sidelink Feedback Channel (PSFCH) resource different from the set of sidelink resources, and wherein the second terminal device is further caused to: An indication is sent to the first terminal device to enable hybrid automatic repeat request (HARQ) feedback from the first terminal device to the second terminal device for the at least one sidelink transmission.

24. A second terminal device according to any one of claims 15 to 22, wherein the at least one sidelink resource is mapped to at least one PSFCH resource in the sidelink resource set, and the second terminal device is further caused to: An indication is sent to the first terminal device to enable HARQ feedback from the first terminal device to the second terminal device for the at least one sidelink transmission.

25. The second terminal device of claim 24, wherein the second terminal device is caused to send the at least one sidelink transmission by at least one of: reducing a modulation and coding scheme (MCS) of the at least one sidelink transmission; or Enabling repetition of the at least one sidelink transmission.

26. The second terminal device according to any one of claims 1 to 25, wherein the sidelink resource set comprises at least one of the following: At least one resource block (RB) set; at least one resource pool; or At least one bandwidth portion.

27. A second terminal device according to any one of claims 1 to 26, wherein the sidelink resource set is a first resource pool, the information is received from the first terminal device in a second resource pool different from the first resource pool, and the information includes an indication of the first resource pool.

28. A network device comprising: at least one processor; as well as At least one memory storing instructions, which, when executed by the at least one processor, cause the network device to at least: receiving first information from a first terminal device, the first information relating to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a set of sidelink resources; as well as Sending second information determined based on the first information to a second terminal device.

29. The network device according to claim 28, wherein the first information comprises at least one of the following: an indication that the persistent LBT failure is detected on the sidelink resource set; an indication of the duration of the ongoing LBT failure; or An indication of the sidelink resource set.

30. The network device of claim 28 or 29, wherein the set of sidelink resources comprises at least one of the following: At least one resource block (RB) set; at least one resource pool; or At least one bandwidth portion.

31. The network device according to any one of claims 28 to 30, wherein the first information is received from the first terminal device in a case where the first terminal device is within coverage of the network device.

32. The network device according to any one of claims 28 to 31, wherein the network device is configured to send the second information to the second terminal device by: Based on determining that the second terminal device is within the coverage of the network device, the second information is sent to the second terminal device.

33. The network device according to any one of claims 28 to 32, wherein the second information comprises at least one of the following items: an indication that the persistent LBT failure is detected on the sidelink resource set; an indication of the duration of the ongoing LBT failure; or An indication of the sidelink resource set.

34. The network device according to claim 33, wherein the network device is configured to send the second information to the second terminal device by: Based on determining that the second terminal device is in the second resource allocation mode, the second information is sent to the second terminal device.

35. The network device according to any one of claims 28 to 32, wherein the second information comprises: an indication of at least one sidelink resource allocated for at least one sidelink transmission to be sent from the second terminal device to the first terminal device.

36. The network device of claim 35, wherein the network device is further caused to: The at least one sidelink resource allocated for the at least one sidelink transmission is determined based on receiving the request for resources for sending the at least one sidelink transmission.

37. The network device according to claim 35 or 36, wherein the at least one sidelink resource is mapped to at least one physical sidelink feedback channel (PSFCH) resource different from the sidelink resource set.

38. The network device according to claim 35 or 36, wherein the at least one sidelink resource is mapped to at least one PSFCH resource in the sidelink resource set, and the second information further includes: Disabling indication of hybrid automatic repeat request (HARQ) feedback from the first terminal device to the second terminal device for the at least one sidelink transmission.

39. The network device according to claim 38, wherein the second information further includes at least one of the following: an indication of a reduced modulation and coding scheme (MCS) of the at least one sidelink transmission; or An indication of a repetition of the at least one sidelink transmission.

40. A method comprising: At the first terminal device, determining that a persistent listen-before-talk (LBT) failure on a sidelink resource set is detected; as well as Information related to the persistent LBT failure is sent to at least one of a second terminal device or a network device.

41. A method comprising: receiving, at a first terminal device, information related to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a set of sidelink resources; as well as At least one sidelink transmission is sent to the first terminal device on at least one sidelink resource determined based on the received information.

42. A method comprising: At a network device, first information is received from a first terminal device, the first information relating to a persistent listen-before-talk (LBT) failure detected by the first terminal device on a set of sidelink resources; as well as Sending second information determined based on the first information to a second terminal device.

43. An apparatus comprising: means for determining that a persistent listen-before-talk (LBT) failure is detected on a sidelink resource set; as well as means for sending information related to the persistent LBT failure to at least one of a second terminal device or a network device.

44. An apparatus comprising: means for receiving information relating to persistent listen-before-talk, LBT, failures detected by the first terminal device on the set of sidelink resources; as well as means for sending at least one sidelink transmission to the first terminal device on at least one sidelink resource determined based on the received information.

45. An apparatus comprising: means for receiving first information from a first terminal device, the first information relating to a persistent listen-before-talk, LBT, failure detected by the first terminal device on a set of sidelink resources; as well as A component configured to send second information determined based on the first information to a second terminal device.

46. ​​A non-transitory computer-readable medium comprising program instructions, which, when executed by an apparatus, cause the apparatus to at least perform the method according to any one of claims 40 to 42.

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