Channel access priority

Abstract

Certain examples of the present disclosure relate to apparatuses, methods, and computer programs for determining channel access priorities. Certain examples provide an apparatus (10) comprising: means (11) for determining information indicating a channel access priority (p) for a physical sidelink feedback channel, PSFCH, transmission (205) based at least in part on: information indicating at least one state of a last at least one PSFCH transmission (204); or information indicating a propagation type of a sidelink (SL) transmission (202) associated with the PSFCH transmission (205).

Description

Technical Field

[0001] Various examples of the present disclosure relate to the field of data communications, and in particular to: apparatus, methods and computer programs for determining channel access priority. Certain examples, although not affecting the foregoing, relate to: user equipment for determining a channel access priority category for transmissions made via a physical sidelink feedback channel. Background Art

[0002] Conventional methods of determining channel access priorities for transmissions, such as for Physical Sidelink Feedback Channel (PSFCH) transmissions, are not always optimal.

[0003] In some situations, it may be desirable to provide improved apparatus, methods, and computer programs for determining channel access priority for transmissions, such as PSFCH transmissions.

[0004] The listing or discussion of any previously published document or any background technology in this specification is not necessarily taken as an admission that the document or background technology is part of the prior art or is common general knowledge. One or more aspects / examples of the present disclosure may or may not address one or more background technology issues. Summary of the invention

[0005] The following claims set out the scope of protection sought for various embodiments of the invention.

[0006] According to various but not necessarily all examples of the present disclosure, examples as claimed in the appended claims are provided.Any examples and features described in this specification that do not fall within the scope of the independent claims should be interpreted as examples that help understand the various embodiments of the present invention.

[0007] According to at least some examples of the present disclosure, there is provided an apparatus comprising:

[0008] Means for determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on:

[0009] Information indicating at least one state of at least one last PSFCH transmission; or

[0010] Information indicating the propagation type of the sidelink (SL) transmission associated with the PSFCH transmission.

[0011] According to various but not necessarily all examples of the present disclosure, there is provided a method comprising:

[0012] and determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on:

[0013] Information indicating at least one state of at least one last PSFCH transmission; or

[0014] Information indicating the propagation type of the sidelink (SL) transmission associated with the PSFCH transmission.

[0015] According to various but not necessarily all examples of the present disclosure, there is provided a chipset including a processing circuit system configured to execute the above method.

[0016] According to various but not necessarily all examples of the present disclosure, a module, a circuit system, a device, a user equipment and / or a system is provided, which module, the circuit system, the device, the user equipment and / or the system include components for performing the above method.

[0017] According to various but not necessarily all examples of the present disclosure, there is provided a computer program comprising instructions which, when executed by a device, cause the device to perform:

[0018] and determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on:

[0019] Information indicating at least one state of at least one last PSFCH transmission; or

[0020] Information indicating the propagation type of the sidelink (SL) transmission associated with the PSFCH transmission.

[0021] According to various but not necessarily all examples of the present disclosure, there is provided an apparatus comprising:

[0022] at least one processor; and

[0023] at least one memory storing instructions that, when executed by at least one processor, cause the apparatus to at least:

[0024] and determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on:

[0025] Information indicating at least one state of at least one last PSFCH transmission; or

[0026] Information indicating the propagation type of the sidelink (SL) transmission associated with the PSFCH transmission.

[0027] According to various but not necessarily all examples of the present disclosure, there is provided a non-transitory computer-readable medium encoded with instructions that, when executed by at least one processor, cause at least the following to be performed:

[0028] and determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on:

[0029] Information indicating at least one state of at least one last PSFCH transmission; or

[0030] Information indicating the propagation type of the sidelink (SL) transmission associated with the PSFCH transmission.

[0031] In some but not necessarily all examples, the PSFCH transmission is in an unlicensed band.

[0032] In some but not necessarily all examples, the information indicating the channel access priority indicates at least one item selected from the group consisting of:

[0033] Priority categories used in the Listen Before Talk (LBT) process;

[0034] Priority classes for use in unlicensed bands;

[0035] Channel Access Priority Class (CAPC);

[0036] Contention Window (CW); and

[0037] Channel Occupancy Time (COT).

[0038] In some but not necessarily all examples, the information indicating at least one state of the last at least one PSFCH transmission includes information indicating at least one item selected from the group consisting of:

[0039] The channel access status of the last at least one PSFCH transmission;

[0040] Whether the last at least one PSFCH transmission failed or succeeded;

[0041] Whether the LBT procedure used to send the last at least one PSFCH transmission failed or succeeded;

[0042] LBT success rate for the last one or more PSFCH transmissions;

[0043] The number of LBT successes for the last one or more PSFCH transmissions;

[0044] whether the PSFCH transmission includes a retransmission of information that was not successfully transmitted via the last at least one PSFCH transmission;

[0045] Allocation of resources for PSFCH transmission, wherein the resources are allocated for retransmission of information that was not successfully transmitted via the last at least one PSFCH transmission; and

[0046] Whether the PSFCH transmission is within the channel occupation time (COT) shared by the UE.

[0047] In some but not necessarily all examples, means for determining information indicating a channel access priority for PSFCH transmission includes:

[0048] means for determining a first candidate priority class for PSFCH transmission;

[0049] means for determining a second candidate priority class for PSFCH transmission; and

[0050] Means for selecting at least one of a first candidate priority category and a second candidate priority category.

[0051] In some but not necessarily all examples, at least one selected from the group consisting of:

[0052] The first candidate priority category and / or the second candidate priority category are predefined;

[0053] The first candidate priority class and / or the second candidate priority class is configured to the device;

[0054] The first candidate priority class is configured to have a lower channel access priority than the second candidate priority class;

[0055] The first candidate priority class is determined based at least in part on a channel access priority of one or more SL transmissions associated with the transmission;

[0056] The second candidate priority class is determined based at least in part on a channel access priority of one or more SL transmissions associated with the transmission;

[0057] The second candidate priority category is determined based at least in part on the first candidate priority category; and

[0058] The second candidate priority class is determined based at least in part on the first candidate priority class and the priority class offset.

[0059] In some but not necessarily all examples, means for selecting one of the first and second candidate priority categories includes means for selecting one of the first and second candidate priority categories based on at least one selection criterion.

[0060] In some but not necessarily all examples, at least one selection criterion includes selecting the first candidate priority category by default.

[0061] In some but not necessarily all examples, the at least one selection criterion includes selecting the second candidate priority category in response to at least one of:

[0062] determining whether the PSFCH transmission is a retransmission of at least a portion of a previously attempted PSFCH transmission;

[0063] determining whether the PSFCH transmission is a retransmission of a previous attempt to send feedback;

[0064] determining whether the PSFCH transmission is a retransmission of a previous attempt to send a hybrid automatic repeat request acknowledgement (HARQ-ACK) or a negative acknowledgement (NACK);

[0065] Determining the type of resources used for PSFCH transmission;

[0066] determining whether the resources allocated for PSFCH transmission are resources allocated for retransmission of information that failed to be successfully transmitted via the last at least one PSFCH transmission; and

[0067] Determine whether at least one HARQ-ACK of the last one or more PSFCH transmissions failed to be sent via earlier allocated resources due to LBT failure.

[0068] In some but not necessarily all examples, the at least one selection criterion includes selecting the second candidate priority category in response to:

[0069] Determine whether the LBT success rate of multiple previous PSFCH transmissions is less than a threshold.

[0070] In some but not necessarily all examples, the at least one selection criterion includes selecting the second candidate priority category in response to:

[0071] Determine whether the number of LBT successes of multiple last PSFCH transmissions is less than a threshold.

[0072] In some but not necessarily all examples, the at least one selection criterion includes selecting the second candidate priority category in response to:

[0073] Determines whether the SL transmission is a unicast transmission.

[0074] In some but not necessarily all examples, the apparatus further comprises:

[0075] Means for receiving configuration information for enabling the apparatus to determine at least one selection criterion to be applied for selecting one of the first candidate priority category and the second candidate priority category.

[0076] In some but not necessarily all examples, the apparatus further comprises:

[0077] Means for determining at least one selection criterion to apply based at least in part on a propagation type of SL transmissions associated with a PSFCH transmission.

[0078] In some but not necessarily all examples, the apparatus further comprises:

[0079] Means for receiving configuration information for enabling the apparatus to determine information indicative of a channel access priority for PSFCH transmissions.

[0080] In some but not necessarily all examples, the configuration information includes an indication of at least one item selected from the group of:

[0081] First candidate priority category;

[0082] Second candidate priority category;

[0083] an offset between the first candidate priority class and the second candidate priority class;

[0084] Number of last PSFCH transmissions;

[0085] Threshold transmission success rate;

[0086] The threshold number of successful transmissions;

[0087] the propagation type of the SL transmission associated with the PSFCH transmission; and

[0088] One or more selection criteria to be applied by the device.

[0089] In some but not necessarily all examples, the broadcast type includes at least one of: multicast and unicast.

[0090] In some but not necessarily all examples, the SL transmission associated with the PSFCH transmission includes a physical sidelink shared channel (PSSCH) transmission.

[0091] In some but not necessarily all examples, the apparatus further comprises:

[0092] Means for causing performance of a channel access procedure for sending the transmission based at least in part on the determined information indicative of a channel access priority.

[0093] Although the above examples and optional features of the present disclosure are described separately, it should be understood that their provision in all possible combinations and arrangements is included in the present disclosure. It should be understood that each example of the present disclosure may include any or all features described relative to other examples of the present disclosure, and vice versa. In addition, it should be understood that any one or more features or all features may be implemented in any combination as needed and appropriately by devices, methods and / or computer program instructions, or by being included in devices, methods and / or computer program instructions, or may be performed by devices, methods and / or computer program instructions. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Some examples will now be described with reference to the accompanying drawings, in which:

[0095] Figure 1 An example of the subject matter described herein is shown;

[0096] Figures 2(a)-2(f) show other examples of the subject matter described herein;

[0097] Figure 3 Another example of the subject matter described herein is shown;

[0098] Figure 4 Another example of the subject matter described herein is shown;

[0099] Figures 5(a) and 5(b) illustrate other examples of the subject matter described herein;

[0100] Figure 6 Another example of the subject matter described herein is shown;

[0101] Figure 7 Another example of the subject matter described herein is shown;

[0102] Figure 8 Another example of the subject matter described herein is shown;

[0103] Fig. 9 Another example of the subject matter described herein is shown;

[0104] Fig.10 Another example of the subject matter described herein is shown;

[0105] Fig.11 Another example of the subject matter described herein is shown; and

[0106] Fig.12 Another example of the subject matter described herein is shown.

[0107] These figures are not necessarily drawn to scale. For clarity and brevity, certain features and views in the figures may be shown schematically or in an exaggerated manner. For example, for ease of explanation, the size of some elements in the figures may be exaggerated relative to other elements. Similar reference numbers are used in the figures to indicate similar features. For clarity, all reference numbers are not necessarily shown in all figures.

[0108] In the drawings (and the specification), similar features may be referenced by the same three-digit number. In the drawings (and the specification), the optional subscript of the three-digit number may be used to distinguish different instances of similar features. Therefore, the three-digit number without a subscript may be used as a general reference, and the three-digit number with a subscript may be used as a specific reference. The subscript may include a single digit marking different instances. The subscript may include two digits, which include a first digit marking a group of instances and a second digit marking different instances in the group.

[0109] Abbreviation / Definition

[0110] 5G Fifth Generation

[0111] ACK

[0112] CAPC Channel Access Priority Class

[0113] CCA Clear Channel Assessment

[0114] CG Configuration Grant

[0115] COT Channel Occupancy Time

[0116] CSI Channel State Information

[0117] CW Contention Window

[0118] DL Downlink

[0119] gNB gNodeB

[0120] HARQ Hybrid Automatic Repeat Request

[0121] LBT Listen before you speak

[0122] NR New Radio

[0123] PSCCH Physical Sidelink Control Channel

[0124] PSFCH Physical Sidelink Feedback Channel

[0125] PSSCH Physical Sidelink Shared Channel

[0126] PUCCH Physical Uplink Control Channel

[0127] RAN Radio Access Network

[0128] Rx Receiver

[0129] SCI Side Link Control Information

[0130] SL Side Link

[0131] TB Transfer Block

[0132] Tx Transmitter

[0133] U Non-licensed

[0134] UE User Equipment

[0135] UL Uplink DETAILED DESCRIPTION

[0136] Figure 1 An example of a network 100 is schematically illustrated, which includes multiple network nodes, including a terminal node 110 (also referred to as a user equipment, UE), an access node 120, and one or more core nodes 130. The terminal node 110 and the access node 120 communicate with each other. The access node 120 communicates with the one or more core nodes 130. The one or more core nodes 130 can communicate with each other in some but not necessarily all examples. The one or more access nodes 120 can communicate with each other in some but not necessarily all examples.

[0137] In this example, the network 100 is a radio telecommunication network, ie a Radio Access Network (RAN), in which the terminal nodes 110 and at least some of the access nodes 120 communicate with each other using transmission / reception of radio waves.

[0138] The RAN 100 may be a cellular network comprising a plurality of cells 122, each cell being served by an access node 120. The access node 120 comprises a cellular radio transceiver. The terminal node 110 comprises a cellular radio transceiver.

[0139] In the particular example illustrated, network 100 is a Next Generation (NG) or New Radio (NR) network. NR is the Third Generation Partnership Project (3GPP) name for fifth generation (5G) technology.

[0140] The interface between the terminal node 110 and the access node 120 is a radio interface 124 (eg, a Uu interface). The interface between the access node 120 and one or more core nodes 130 is a backhaul interface 128 (eg, an S1 interface and / or an NG interface).

[0141] Depending on the exact deployment scenario, the access node 120 may be a RAN node, such as a NG-RAN node. The NG-RAN node may be a gNodeB (gNB), which provides NR user plane and control plane protocol termination to the UE. The NG-RAN node may be a new generation evolved universal terrestrial radio access network (E-UTRAN) NodeB (ng-eNB), which provides E-UTRA user plane and control plane protocol termination to the UE. The gNB and ng-eNB may be interconnected with each other by means of an Xn interface. The gNB and ng-eNB are also connected to the 5G core (5GC) by means of an NG interface, more specifically, to the AMF (Access and Mobility Management Function) by means of an NG-C interface, and to the UPF (User Plane Function) by means of an NG-U interface. The access nodes 120 may be interconnected with each other by means of an Xn interface 126. The cellular network 100 may be configured to operate in a licensed band or an unlicensed band, such as, in particular, a 60 GHz unlicensed band, where beamforming is mandatory in order to achieve the desired coverage.

[0142] The access node 120 may be deployed in NR standalone operation / scenario. The access node 120 may be deployed in NR non-standalone operation / scenario. The access node may be deployed in carrier aggregation (CA) operation / scenario. The access node 120 may be deployed in dual connectivity operation / scenario, i.e., multi-radio access technology-dual connectivity (MR-DC), such as, for example:

[0143] Evolved Universal Terrestrial Radio Access – New Radio Dual Connectivity (EUTRA-NR-DC, also known as EN-DC),

[0144] New Radio - Evolved Universal Terrestrial Radio Access Dual Connectivity (NR-EUTRA-DC, also known as NE-DC),

[0145] Next Generation Radio Access Network Evolved Universal Terrestrial Radio Access – New Radio Dual Connectivity (NG-RAN E-UTRA-NR Dual Connectivity, also known as NGEN-DC), or

[0146] New Radio Dual Connectivity (also known as NR-DC).

[0147] In such a non-standalone / dual connectivity deployment, the access nodes 120 may be interconnected with each other via an X2 interface or an Xn interface, and connected to an evolved packet core (EPC) via an S1 interface or to a 5GC via an NG interface.

[0148] The terminal node 110 is a network element that terminates the user side of the radio link in the network. The network element is a device that allows access to network services. The terminal node 110 may be referred to as a user equipment (UE), a mobile terminal, or a mobile station. The term "user equipment" may be used to indicate a mobile device that includes a smart card (such as a subscriber identity module (SIM)) for authentication / encryption, etc. In other examples, the term "user equipment" is used to indicate a mobile device that includes a circuit system (such as a software SIM) embedded as part of the user equipment for authentication / encryption.

[0149] The access node 120 is a network element in the network responsible for radio transmission to the terminal node 110 in one or more cells 122, and radio reception from the terminal node 110. Such an access node may also be referred to as a transmission reception point (TRP) or a base station. The access node 120 is a network terminal of a radio link. The access node 120 may be implemented as a single network device, or decomposed / distributed over two or more RAN nodes, such as a central unit (CU), a distributed unit (DU), a remote radio head (RRH), using different functional split architectures and different interfaces.

[0150] In the following description, the access node will be referred to as gNB 120, and the terminal node 110 will be referred to as UE 110.

[0151] In the sub-7 GHz unlicensed band / unlicensed spectrum, the coexistence of New Radio (NR) with other systems (e.g., IEEE802.11) is ensured via a "Listen Before Talk" (LBT) channel access procedure / mechanism. Here, a user equipment that is expected to perform a sidelink (SL) transmission needs to first successfully complete the LBT check before being able to initiate a transmission.

[0152] In order for a UE to pass the LBT check, it must observe that the transmission channel is available for a number of consecutive clear channel assessment (CCA) slots. Below 7GHz, these slots are 9μs in duration. If the measured power (i.e., the energy collected 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.

[0153] When the UE initiates communication (i.e., the UE plays the role of an initiating device), then the UE must obtain the "right" to access the channel for a certain period of time (denoted as the Channel Occupancy Time (COT)) by applying an "extended" LBT procedure. Here, the channel must be considered idle for the entire duration of the backoff procedure determined by the contention window (CW). This "extended" LBT procedure is generally referred to as LBT Type 1, as specified in TS 37.213.

[0154] The duration of both the COT and the CW depends on the channel access priority class (CAPC) associated with the UE's traffic, such as shown below in Table 1. Control plane traffic is sent with p=1, while user plane traffic has p>1.

[0155] Table 1 (from "Table 4.2.1-1: Channel Access Priority Classes (CAPCs) for UL" of TS 37.213). The contention window length in the CCA slot associated with each CAPC has a minimum value (CW min,p ) and maximum value (CW max,p ). The duration of COT is determined by T ulm cot,p ) is given.

[0156]

[0157]

[0158] Figures 2(a)-2(f) depict LBT Type 1 details for the Uu uplink (UL) case. It should be understood that the LBT Type 1 parameters for the downlink (DL) case can also be adopted in principle in the SL. These figures illustrate the allowed gaps to which the LBT Type 2 variant applies:

[0159] Figure 2(a) and Figure 2(d) - LBT type 2C;

[0160] Figure 2(b) and Figure 2(e) - LBT type 2B;

[0161] Figure 2(c) and Figure 2(f) - LBT type 2A.

[0162] Figures 2(a), 2(b) and 2(c) show the case where the gap is between two transmissions both from an initiating UE, while Figures 2(d), 2(e) and 2(f) show the case where the gap is between two different transmissions from an initiating UE and a responder.

[0163] Once the UE initiating the transmission (the initiating device) has successfully completed LBT Type 1 and performed the transmission, a COT is obtained, which has a duration associated with the corresponding CAPC used for the transmission. The obtained COT is valid even in the case where the initiating device suspends its transmission, although if the initiating device wants to perform a new transmission (within the COT), the initiating device still needs to perform a "simplified" LBT procedure. This "simplified" LBT procedure is generally referred to as LBT Type 2 [TS 37.213], with the following variations:

[0164] Type 2A (25 μs LBT)—for SL transmission within the COT acquired by the initiating device (when the gap between two SL transmissions is ≥ 25 μs, and for SL transmission following another SL transmission), as depicted in FIG2( c ) and FIG2( f ).

[0165] Type 2B (16μs LBT) - used for SL transmission within the COT acquired by the initiating device (can only be used for SL transmission after another SL where the gap is exactly equal to 16μs), as depicted in Figures 2(b) and 2(e).

[0166] Type 2C (no LBT) - can only be used for SL transmission after another SL, where the gap is <16 μs and the allowed duration of the SL transmission is ≤584 μs), as depicted in Figures 2(a) and 2(d).

[0167] The initiating device can share its acquired COT with its intended receiver (the responding device). To this end, the initiating device must inform the responding device (e.g., via control signaling) of the duration of the COT. The responding device then uses this information to decide which type of LBT should be applied when performing a transmission for which the intended receiver is the initiating device. If the responding device transmission falls outside the COT, the responding device will have to acquire a new COT using LBT Type 1 with an appropriate CAPC.

[0168] Below is an overview of the Sidelink (SL) in New Radio (NR).

[0169] In 3GPP Release 16, NR SL has been designed to facilitate UEs to communicate with other nearby (multiple) UEs via direct / SL communications. Two resource allocation modes have been specified, and the SL transmitter (Tx) UE is configured with one of the two resource allocation modes to perform its NR SL transmissions. These modes are labeled: NR SL Mode 1 and NRSL Mode 2.

[0170] In NL SR Mode 1, the network (NW) assigns (schedules) sidelink transmission resources to the SL Tx UE, while in Mode 2, the SL Tx UE autonomously selects its SL transmission resources.

[0171] In NL SR Mode 1, where the gNB is responsible for SL resource allocation, configuration and operation are similar to those over the Uu interface (which is Figure 3 The MAC level details of this process are given in Section 5.8.3 of TS 38.321.

[0172] In NL SR Mode 2 (which is Figure 4 ), the SL UE autonomously performs resource selection with the help of a sensing process. More specifically, the SL Tx UE in NR SL Mode 2 first performs a sensing process on the configured (multiple) SL transmission resource pools in order to obtain knowledge of the (multiple) resources reserved by other nearby SL Tx UEs. Based on the knowledge obtained from the sensing, the SL Tx UE can select (multiple) resources from the available SL resources accordingly. In order for the SL UE to perform sensing and obtain the information required to receive SL transmissions, the SL UE needs to decode the Sidelink Control Information (SCI). In Release 16, the SCI associated with data transmission includes a first stage SCI and a second stage SCI, and their contents are standardized in 3GPP TS 38.212.

[0173] The SCI follows a 2-stage SCI structure, the main motivation of which is to support the size difference between SCIs for various NR-V2X (NR Vehicle-to-Everything) SL service types (e.g., broadcast, multicast, and unicast).

[0174] The first stage SCI, SCI format 1-A, is carried by the physical sidelink shared channel (PSSCH) and contains:

[0175] information to enable sensing operations, and

[0176] Information required to determine resource allocation for PSSCH and to decode the second stage SCI.

[0177] According to the 16th edition, the contents of the first phase of SCI are as follows:

[0178]

[0179]

[0180] The second stage SCI, SCI format 2-A and SCI format 2-B, is carried by PSSCH (multiplexed with SL-SCH) and contains:

[0181] Source and target identification;

[0182] ● Information to identify and decode the associated SL-SCH transport block (TB);

[0183] ●Control of Hybrid Automatic Repeat Request (HARQ) feedback in unicast / multicast;

[0184] ● Trigger for CSI feedback in unicast,

[0185] According to the 16th edition, the contents of the second stage SCI are provided in Table 2 below:

[0186]

[0187]

[0188] Below is an overview of the SL physical layer structure.

[0189] The configuration of resources in the sidelink resource pool defines the minimum information required for the RX UE to be able to decode the transmission, which includes: the number of subchannels; the number of physical resource blocks (PRBs) for each subchannel; the number of symbols in the physical sidelink control channel (PSCCH); which time slots have PSFCH, and other configuration aspects not relevant to the present disclosure.

[0190] Details of the actual sidelink transmission (ie, payload) are provided for each individual transmission in the PSCCH (first stage SCI), including: time and frequency resources; Demodulation Reference Signal (DMRS) configuration for PSSCH; MCS; PSFCH; and so on.

[0191] Fig. 5(a) schematically illustrates an example of a SL slot structure including slots with PSCCH / PSSCH. Fig. 5(b) schematically illustrates an example of a SL slot structure including slots with PSCCH / PSSCH, and in which the last symbol is used for PSFCH.

[0192] The configuration of the PSCCH (e.g., DMRS, MCS, number of symbols used) is part of the resource pool configuration. In addition, an indication of which time slots have PSFCH symbols is also part of the resource pool configuration. However, the configuration of the PSSCH (e.g., number of symbols used, DMRS mode and MCS) is provided by the first stage SCI, which is the payload sent within the PSCCH and follows the configuration depicted above and is stated in 8.3.1.1 of TS 38.212 Release 16.

[0193] The following is an overview of SL HARQ operation.

[0194] PSFCH was introduced during Release 16 to enable HARQ feedback from the UE that is the intended recipient of the PSSCH transmission (i.e., RX UE) to the UE that performs the transmission (i.e., Tx UE) via the sidelink. Within the PSFCH, the Zadoff-Chu sequence in one PRB is repeated over two OFDM symbols, the first of which can be used for AGC, and the two OFDM symbols are located near the end of the sidelink resources in the time slot. An example time slot format for PSCCH, PSSCH, and PSFCH is provided in Figure 5(b). The Zadoff-Chu sequence as the basic sequence is (pre-)configured per sidelink resource pool.

[0195] According to 38.331, the time resources for PSFCH are (pre)configured to occur once every 0 slots, 1 slot, 2 slots or 4 slots.The HARQ feedback resources (PSFCH) are derived from the resource location of PSCCH / PSSCH.

[0196] For PSSCH to HARQ timing, there is a configuration parameter K in units of time slots. The time opportunity for PSFCH is determined based on K. For PSSCH transmission with its last symbol located in time slot n, HARQ feedback is located 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 gap of at least K time slots allows consideration of the processing delay of the RX UE when decoding the PSCCH and generating HARQ feedback. K can be equal to 2 or 3, and a single value of K can be (pre) configured per resource pool. This allows multiple RX UEs using the same resource pool to utilize the same mapping of (multiple) PSFCH resources for HARQ feedback. Using the parameter K, the N PSSCH time slots associated with the time slot with PSFCH can be determined.

[0197] As an example, Figure 6 As illustrated in FIG, the period of the PSFCH resource is configured as N=4 (i.e., there will be 4 PSSCH slots associated with the PSFCH), and K (sl-MinTimeGapPSFCH, which is the minimum time gap between the PSFCH and the associated PSSCH, in slots) is configured as 2. If there are L subchannels in the resource pool, and there are N PSSCH slots associated with the slot containing the PSFCH, then there are N*L subchannels associated with the PSFCH symbol. If there are M PRBs available for PSFCH in the PSFCH symbol, then there are M PRBs available for HARQ feedback for transmissions on the N*L subchannels.

[0198] In the case where M is configured as a multiple of N*L, then in the PSFCH period, different sets of Mset=M / (N*L) PRBs may be associated with HARQ feedback for each subchannel. Of the M PRBs available for PSFCH, a first set of Mset PRBs is associated with HARQ feedback for transmissions in the first subchannel in the first time slot. A second set of Mset PRBs is associated with HARQ feedback for transmissions in the first subchannel in the second time slot, and so on.

[0199] This is Figure 6 , where N=4, L=3, and all PRBs in a PSFCH symbol are available for PSFCH. In this example, HARQ feedback for transmission at PSSCH x is sent on a set x of Mset PRBs in the corresponding PSFCH symbol, where x=1, ..., 12.

[0200] In case of ACK / NACK feedback for groupcast communication (option 2) or in case of different PSSCH transmissions in the same subchannel, the set of Mset PRBs associated with the subchannel is shared among multiple RX UEs.

[0201] For each PRB available for PSFCH, there are Q cyclic shift pairs available within the PRB to support ACK or NACK feedback for Q RX UEs. The number of cyclic shift pairs Q is (pre-)configured for a resource pool and can be equal to 1, 2, 3 or 6.

[0202] The number of PSFCH resources F available to support HARQ feedback for a given transmission can be calculated (in TS 38.213, F is denoted as ). In the case where each PSFCH resource is used by one RX UE, the F available PSFCH resources can be used for ACK / NACK feedback of a maximum of F RX UEs.

[0203] The F PSFCH resources available for multiplexing HARQ feedback for PSSCH may be determined based on two options:

[0204] a) or based on the L PSSCH subchannels used by the PSSCH, where F can be calculated as:

[0205] ○F=L PSSCH*M set *Q PSFCH (associated with L PSSCH subchannels of PSSCH)

[0206] ○ Among them:

[0207] ■L PSSCH subchannels of PSSCH;

[0208] ■ Mset PRBs for the PSFCH associated with each subchannel; and

[0209] ■ Q cyclic shift pairs available in each PRB.

[0210] b) or based only on the starting subchannel used by PSSCH (ie, based only on one subchannel for the case when L PSSCH>1).

[0211] ○F=M set *Q PSFCHs (associated with the starting subchannel of PSSCH)

[0212] ○ Among them:

[0213] ■ M for the PSFCH associated with each subchannel set PRBs; and

[0214] ■ Q cyclic shift pairs available in each PRB.

[0215] Similar to the Physical Uplink Control Channel (PUCCH) in Release 15 NR Uu, the available F PSFCH resources are indexed based on the PRB index (frequency domain) and the cyclic shift pair index (code domain).

[0216] The mapping of PSFCH index i (i=1, 2, ..., F) to PRBs and to Q cyclic shift pairs is such that PSFCH index i first increases with the PRB index until the number of PRBs available for PSFCH is reached. Then, index i increases with the cyclic shift pair index, again with the PRB index, and so on.

[0217] Among the F PSFCHs available for HARQ feedback for a given transmission, the RX UE selects the PSFCH with index i for its HARQ feedback, where index i is given by:

[0218] i=(T ID +R ID )mod F

[0219] Where T ID is the layer 1 ID of the Tx UE (indicated in the stage 2 SCI). For unicast ACK / NACK feedback and multicast NACK-only feedback (option 1), R ID =0.

[0220] For multicast ACK / NACK feedback (option 2), R IDis equal to the RX UE identifier within the group, which is indicated by higher layers. For the number X 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 for sending its HARQ feedback based on the PSFCH index i. The RX UE uses the first cyclic shift or the second cyclic shift from the cyclic shift pair associated with the selected PSFCH index i to send a NACK or ACK, respectively.

[0221] By selecting the PSFCH with index i by the RX UE, the Tx UE can distinguish the HARQ feedback of (multiple) different RX UEs (via the RX UE identifier, e.g., for multicast option 2) from the HARQ feedback expected for the Tx UE (via the Layer 1 ID of the Tx UE, e.g., for unicast). ID = 0, so RX UE is based only on layer 1 ID Tx UE identifier T ID The same PSFCH index i is selected for its NACK-only feedback.

[0222] The priority of simultaneous PSFCH transmission / reception is specified in TS 38.213.

[0223] For PSFCH transmission or PSFCH reception with HARQ-ACK information, the priority value for the PSFCH is equal to the priority value indicated by SCI format 1-A associated with the PSFCH.

[0224] For PSFCH transmissions with conflicting information, the priority value for the PSFCH is equal to the minimum priority value determined by the corresponding SCI format 1-A for the conflicting resources.

[0225] For PSFCH reception with conflicting information, the priority value for the PSFCH is equal to the priority value determined by the corresponding SCI format 1-A for the conflicting resources.

[0226] Currently, in the SL-U design, it is still undetermined how to associate the channel access priorities for the corresponding SL channel transmissions.

[0227] For PSFCH transmissions by SL-U UEs without an initiated COT, the basic question to be solved is: which CAPC should be used for LBT of the PSFCH transmissions?

[0228] Various examples of the present disclosure seek to enable determination of the CAPC for the PSFCH that considers both coexistence fairness with other devices and channel access opportunities for transmitting the PSFCH.

[0229] In various examples of the present disclosure, the SL Rx UE may select an appropriate CAPC for PSFCH transmission from the first CAPC and the second CAPC while considering the result of the LBT for at least one most recent PSFCH transmission.

[0230] The SL Rx UE may determine the first CAPC and the second CAPC using any combination of at least the following:

[0231] ● The first CAPC may be predefined or configured with a higher p value than the second CAPC for channel access to transmit PSFCH

[0232] o In an example, a first CAPC may be predefined / configured with a high p-value (e.g., p=4), and a second CAPC may be predefined / configured with a low p-value (e.g., p=1)

[0233] ● The first / second CAPC can be determined based on the priority of SL transmission associated with the PSFCH for SL Rx UEs

[0234] o In an example, the first CAPC and the second CAPC may be determined based on the lowest priority and the highest priority, respectively, of SL transmissions associated with the PSFCH.

[0235] Optionally, if the p-value of the second CAPC is not lower than the first CAPC or is not lower than the offset relative to the first CAPC, the second CAPC can be upgraded to a CAPC with a lower p-value, i.e., p 2nd =max{1, p 1st -p offset}, where the offset p offset It can be predefined or configured to SL Rx UE during standardization.

[0236] In another example, the first CAPC may be determined based on the highest priority (or lowest priority) of the SL transmission associated with the PSFCH, and the second CAPC may be configured with a lower p value than the first CAPC, wherein the p value of the second CAPC may be set to a certain value (i.e., p=1) by default, or configured to be an offset lower than the p value of the first CAPC (but not less than the minimum p value), i.e., p 2nd =max{1, p 1st -p offset}, where the offset p offset It can be predefined or configured to SL Rx UE during standardization.

[0237] In some examples, the SL UE may obtain the priority of the SL transmission by detecting the first stage SCI of the SL transmission, and associate the PSFCH with the SL transmission based on the (pre)configured PSSCH to PSFCH timing.

[0238] The SL UE may select the first CAPC or the second CAPC for PSFCH transmission based on certain selection criteria / metrics, where each selection criterion / metric may be designed based on the channel access state of the last PSFCH transmission (multiple). For example, by default, the SL UE may use the first CAPC for PSFCH transmission, but if at least one of the following conditions is met, the second CAPC should be selected for PSFCH transmission:

[0239] The resources allocated for PSFCH transmission are secondary PSFCH resources for retransmission of HARQ-ACK(s) that were not sent as expected on the primary PSFCH resources due to failed LBT (see, e.g. Fig.12 ). Here, if the HARQ-ACK on PSFCH fails to be sent as expected on the primary PSFCH resource due to failed LBT, it is assumed that the secondary PSFCH resource will be configured to retransmit (multiple) HARQ-ACKs

[0240] ● The LBT success rate of the last x PSFCH transmissions is less than y%

[0241] The number of LBT successes in the last x PSFCH transmissions is less than y LBT successes (see, for example Fig.11 )

[0242] ○ Alternatively, the x PSFCH transmissions may correspond to the same HARQ process, which means that the SL Rx UE may increase the channel access priority of the PSFCH for the retransmissions.

[0243] Note that the values ​​of x and y may be predefined in the specification, or may be preconfigured by the network.

[0244] Advantageously, examples of the present disclosure may enable CAPC selection for PSFCH based on the channel access status of the most recent PSFCH transmission(s) to better balance channel access opportunities for PSFCH and coexistence fairness with other devices. If HARQ-ACK feedback is blocked due to LBT failure in previous PSFCH transmission(s), examples may allow upgrading to a CAPC with a higher channel access priority to improve channel access opportunities for PSFCH transmissions.

[0245] In some examples of the present disclosure, the SL Rx UE may generally select an appropriate channel access priority based on the lowest priority of the associated SL transmission (e.g., a legacy NR-U UE for PDSCH / PUSCH transmission) rather than the highest priority (of the associated SL transmission) to ensure coexistence fairness with other devices. Only when the channel access success rate is low or an LBT failure occurs for PSFCH transmission, the SL Rx UE will upgrade its CAPC for (re)transmission of HARQ ACK / NACK to improve channel access opportunities for the SL Rx UE.

[0246] Since examples of the present disclosure may enable SL Rx UE to conditionally upgrade CAPC for PSFCH transmission, examples may make a better trade-off between channel access opportunities of PSFCH and coexistence fairness with other devices.

[0247] Figure 7 An example of a method 700 of the present disclosure is schematically illustrated. Figure 7 One or more features discussed in relation may be found in one or more other figures. Figure 7 During the discussion of Fig.11 and Fig.12 ) is the reference number of the feature shown in the figure.

[0248] Figure 7 The method and the functions described below may represent actions in the method, functionality performed by the device, and / or parts of instructions / codes in a computer program. It should be understood that the functionality described below may be implemented by various components, such as hardware, firmware, and / or software including one or more computer program instructions. For example, one or more functions described below may be performed by a suitably configured device (such as a UE, such as a SL Rx UE, including components for performing the functions described below). One or more functions described below may be embodied by a suitably configured computer program (such as a computer program including computer program instructions that embody the functions described below and can be stored by a memory storage device and executed by a processor).

[0249] Figure 7 Method 7 and the functions described below may be implemented by a single physical entity (such as reference Figure 8 The device described) is executed / on a single physical entity (such as reference Figure 8 The functions described may also be implemented by a computer program, such as the one described in Fig. 9 as described.

[0250] In block 701, information indicating a channel access priority (p) for a transmission (205) on a transmission channel (203) is determined based at least in part on at least one of:

[0251] information indicative of a status of at least one previous transmission (204) on the transmission channel (203); and

[0252] Information indicating a propagation type of a received transmission (202) associated with the transmission (205).

[0253] For purposes of the following discussion of various examples of the present disclosure and for simplicity of explanation:

[0254] The transport channel may be referred to as the Physical Sidelink Feedback Channel (PSFCH);

[0255] A transmission may be referred to as a PSFCH transmission, such as a current / upcoming PSFCH transmission or a PSFCH occurrence; and

[0256] At least one previous transmission may be referred to as: at least one previous or most recent PSFCH transmission, the last at least one PSFCH transmission, or the last at least one PSFCH occurrence. At least one previous transmission may also be referred to as the last x PSFCH transmissions, where x is an integer greater than 0. The term "last" as used herein may refer to "immediately preceding" or most recent, for example, the last x PSFCH transmissions may refer to the previous two PSFCH opportunities immediately preceding the current / upcoming PSFCH opportunity (where channel access priority will be determined for the current / upcoming PSFCH transmission, which is the PSFCH transmission for which channel access priority will be determined).

[0257] It should be appreciated that the underlying concepts of the present disclosure may be applicable to transmission channels other than PSFCH, transmissions other than PSFCH transmissions, and at least one previous transmission other than at least one previous PSFCH transmission. For example, in some examples, the transmission channel is at least one selected from the group consisting of:

[0258] Physical Sidelink Shared Channel (PSSCH); and

[0259] Synchronization Signal Block (SSB).

[0260] In some examples, the transmission channel is in an unlicensed frequency band.

[0261] In some examples, the information indicating the channel access priority indicates at least one item selected from the group of:

[0262] a priority class for use in a procedure for determining whether a transmitting device (e.g., a SL Rx UE) is allowed to transmit over a transmission channel, such as, in particular, a Listen Before Talk (LBT) procedure;

[0263] Priority classes for use in unlicensed bands;

[0264] Channel Access Priority Class (CAPC);

[0265] a contention window (CW) (eg, determined based at least in part on the determined CAPC and Table 1); and

[0266] Channel Occupancy Time (COT) (eg, determined based at least in part on the determined CAPC and Table 1).

[0267] In some examples, the information indicating the status of at least one previous transmission includes information indicating at least one item selected from the group of: a channel access status of at least one previous transmission, such status may indicate whether the at least one previous transmission failed or succeeded;

[0268] whether the LBT procedure for sending at least one previous transmission failed or succeeded;

[0269] LBT success rate for one or more previous transmissions;

[0270] The number of LBT successes for one or more previous transmissions;

[0271] whether the transmission includes a retransmission of information that was not successfully sent via at least one previous transmission;

[0272] allocation of resources for a transmission (e.g., PSFCH resources for a PSFCH transmission, such as HARQ feedback), wherein the resources are allocated for retransmission of information that failed to be successfully transmitted via at least one previous transmission (such resources may correspond to "secondary" resources that have been allocated, e.g., have been allocated to a SL Rx UE for effecting a transmission, following a "primary" resource that had previously been allocated in an effort to seek to previously transmit that transmission, but wherein that previous transmission was unsuccessful and thereby required allocation of "secondary" resources to retransmit the previously failed transmission); and

[0273] Whether the PSFCH transmission is within the channel occupancy time (COT) shared by the UE (i.e., another UE). For example, if the SLRx UE can detect the COT shared by the SL Tx UE, but the SL Rx UE is not a responder to the COT, the SL Rx UE may be allowed to upgrade its CAPC for PSFCH transmission.

[0274] In some examples, information indicative of a status of at least one previous transmission is determined.

[0275] In some examples, determining information indicating a channel access priority for transmission includes:

[0276] Determine the first candidate priority class (p 1st );

[0277] Determine a second candidate priority class (p 2nd );as well as

[0278] At least one candidate priority category of the first candidate priority category and the second candidate priority category is selected.

[0279] For example, the determined information indicating the channel access priority may be a priority category (p), and the determined priority category may correspond to the selected first candidate priority category or the second candidate priority category, that is, p=p 1st or p 2nd , wherein one of the first candidate priority category or the second candidate priority category is selected based on one or more selection criteria / metrics as discussed below.

[0280] In some examples, the first candidate priority category and / or the second candidate priority category are predefined, for example, they may be stated in a standard such as a 3GPP Technical Specification (TS).

[0281] In some examples, the first candidate priority category and / or the second candidate priority category are configured to the device. For example, the gNB can determine the first candidate priority category and / or the second candidate priority category, for example, based on business information. The gNB can configure the first candidate priority category and / or the second candidate priority category for the SL Rx UE. By configuring the first candidate priority category and / or the second candidate priority category for the SL Rx UE, this can reduce implementation complexity by avoiding the SL Rx UE needing to determine the first candidate priority category and / or the second candidate priority category for itself.

[0282] In some examples, the priority of the first candidate priority category is configured to have a lower priority (ie, a higher p-value / CAPC value) than the priority of the second candidate priority category, i.e., p 1st >p 2nd .

[0283] In some examples, the first candidate priority category is determined based at least in part on a lowest channel access priority of one or more received SL transmissions associated with the transmission. For example, the transmission may be a PSFCH transmission, and the one or more received SL transmissions may be one or more PSCCH+PSSCH transmissions (e.g., PSCCH+PSSCH A and PSCCH+PSSCH B) received by the SL Rx UE, where each of the one or more PSCCH+PSSCH transmissions is associated with its own channel access priority value (e.g., PSCCH+PSSCH A and PSCCH+PSSCH B). A and p B ), such as indicated by SCI format 1-A carried by PSCCH. It should be appreciated that feedback (e.g., HARQ feedback) is provided for a PSCCH+PSSCH transmission by means of a PSFCH transmission, and the PSCCH+PSSCH transmission is associated with the PSFCH transmission. The first candidate priority category may be p 1st =min(p A ,p B ).

[0284] In some examples, the second candidate priority category is determined based at least in part on the highest channel access priority of one or more received SL transmissions associated with the transmission, i.e., p 2nd =max(p A ,p B ).

[0285] In some examples, the second candidate priority category is determined based at least in part on the first candidate priority category. 2nd =max{1,p 1st -p offset}, where p offset is an attribute class offset parameter. The value of the offset parameter may be predefined during standardization or configured to the SL Rx UE. For example, the priority class offset parameter value may be determined by the gNB, for example, based on the channel access requirements or service type of the SL Rx UE, and the gNB may provide the priority class offset parameter value to the SL Rx UE so that the SL Rx UE may determine the second candidate priority class. For example, determining p 1st After that, SL RxUE can be based on p 2nd =max{1,p 1st -p offset} to determine p 2nd .

[0286] In some examples, at least one of the first candidate priority category and the second candidate priority category is selected according to at least one selection criterion.

[0287] In some examples, at least one selection criterion includes selecting a first candidate priority category by default.

[0288] In some examples, the at least one selection criterion includes selecting the second candidate priority category in response to at least one of:

[0289] determining whether a transmission (e.g., a PSFCH transmission) is a retransmission of at least a portion of a previously attempted transmission (e.g., an earlier attempt to send the same PSFCH transmission or at least a portion thereof);

[0290] determining whether a transmission (e.g., a PSFCH transmission) is a retransmission of a previous attempt to send feedback (e.g., a hybrid automatic repeat request acknowledgement (HARQ-ACK) or a negative acknowledgement (NACK));

[0291] Determining the type of resources used for a transmission (e.g., determining whether a transmission uses one or more "secondary" PSFCH resources to retransmit a PSFCH transmission that was previously attempted to be sent via a "primary" PSFCH resource);

[0292] determining whether the resources allocated for transmission are resources allocated for retransmission of information that was not successfully transmitted via at least one previous transmission; and

[0293] Determine whether one or more previously transmitted HARQ-ACKs failed to be sent via previously allocated resources due to LBT failure.

[0294] In some examples, at least one selection criterion includes selecting a second candidate priority category in response to determining whether an LBT success rate of a plurality (x) of previous transmissions is less than a threshold LBT success rate value (y%). The LBT success rate may be determined by a transmitting device (e.g., a SL Rx UE) performing the LBT process, and each of the number of previous transmissions (x) and the threshold LBT success rate (y%) may be predefined or configured for the SL Rx UE.

[0295] In some examples, at least one selection criterion includes selecting a second candidate priority category in response to determining whether a number of LBT successes of a plurality (x) of previous transmissions is less than a threshold (y). Each of the threshold number of LBT successes (y) and the number of previous transmissions (x) can be predefined or configured to the SL Rx UE so that the SL Rx UE LBT can evaluate whether the number of LBT successes in the last x previous transmissions is less than the threshold number of LBT successes (y).

[0296] In some examples, the at least one selection criterion includes selecting the second candidate priority category in response to determining whether the received transmission is unicast.

[0297] In some examples, configuration information and / or parameters are received to enable the apparatus to determine information indicating a channel access priority for transmission. For example, one or more of the following may be provided to the SL Rx UE:

[0298] The value of the first candidate priority category, p 1st ;

[0299] The value of the second candidate priority category, p 2nd ;

[0300] The value of the priority class offset parameter, p offset ;

[0301] Threshold value of LBT success rate (y%);

[0302] Threshold value for the number of LBT successes (y);

[0303] the value of the number of previous transmissions (x); and

[0304] An indication of the type of propagation of the received transmission (eg, whether it is unicast or multicast) associated with the transmission.

[0305] In some examples, configuration information is received to enable determination of at least one selection criterion to be applied (ie, to select one of a first candidate priority category and a second candidate priority category).

[0306] In some examples, a determination is made regarding at least one selection criterion to be applied based at least in part on a propagation type of a received transmission associated with the transmission (e.g., whether a received SL transmission / PSSCH transmission associated with a PSFCH transmission is a unicast transmission to a single UE or a multicast transmission to multiple UEs).

[0307] In some examples, the received transmission associated with the transmission includes a received PSSCH transmission associated with the PSFCH transmission.

[0308] In some examples, a channel access procedure (e.g., LBT) for sending the transmission is performed based at least in part on the determined information indicating the channel access priority. For example, the determined information indicating the channel access priority can be a CAPC in an LBT procedure used to access the PSFCH to send the PSFCH transmission, wherein the CAPC is used to determine a value of the COT and a value of the CW to be used in the LBT procedure.

[0309] The functionality described above, especially from Figure 7 After the description of Figure 10-12 The functionality discussed can be implemented in hardware, software, or a combination of hardware and software.

[0310] Various, but not necessarily all, examples of the present disclosure provide both methods and corresponding apparatus, including various modules, components, or circuit systems that provide functionality for performing / applying the actions of the method. The modules, components, or circuit systems may be implemented as hardware, or may be implemented as software or firmware to be executed by a computer processor. In the case of firmware or software, examples of the present disclosure may be provided as a computer program product that includes a computer-readable storage structure that embodies computer program instructions (i.e., software or firmware) thereon for execution by a computer processor.

[0311] Figure 8 Schematically illustrates a block diagram of an apparatus 10 for executing the methods, processes, procedures and signaling described in the present disclosure, that is, in particular from Figure 7 After the description of the functionality described above and the following description of Figure 10-12 The functionality in question.

[0312] Figure 8 The component blocks in the figure are functional and the functions described can be performed by a single physical entity.

[0313] The apparatus comprises a controller 11, which may be provided within a device such as a UE 110, for example, a SL Rx UE, configured to receive a SL transmission initiated by a SL Tx UE configured to initiate SL communication / transmission.

[0314] The controller 11 may be embodied by a computing device, in particular a computing device such as those mentioned above. In some but not necessarily all examples, the device may be embodied as a chip, a chipset, a circuit system or a module, i.e., for use in any of the above. As used herein, a "module" refers to a unit or device that does not include certain parts / components to be added by the final manufacturer or user.

[0315] The controller 11 may be implemented as a controller circuit system. The controller 11 may be implemented solely in hardware, solely in software including firmware in some aspects, or may be a combination of hardware and software (including firmware).

[0316] The controller 11 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 14 in a general or special purpose processor 12, which executable instructions may be stored on a computer readable storage medium 13 (e.g., a memory or disk, etc.) for execution by such a processor 12.

[0317] The processor 12 is configured to read from and write to the memory 13. The processor 12 may also include an output interface via which data and / or commands are output by the processor 12, and an input interface via which data and / or commands are input to the processor 12. The apparatus may be coupled to or may include one or more other components 15 (e.g., among others: a radio transceiver, a sensor, an input / output user interface element, and / or other modules / devices / components for inputting and outputting data / commands).

[0318] The memory 13 stores a computer program 14 including instructions (computer program instructions / code) that, when loaded into the processor 12, control the operation of the device 10. The instructions of the computer program 14 provide the logic and routines that enable the device to perform the functions described in this disclosure and Figure 7 and Figure 10-12 The processor 12 can load and execute the computer program 14 by reading the memory 13.

[0319] The computer program instructions may be included in a computer program, a non-transitory computer readable medium, a computer program product, a machine readable medium. The term "non-transitory" as used herein is a limitation on the medium itself (i.e., tangible, not a signal), not a limitation on data storage persistence (e.g., RAM vs. ROM). In some but not necessarily all examples, the computer program instructions may be distributed over multiple computer programs.

[0320] Although the memory 13 is illustrated as a single component / circuitry, it may be implemented as one or more separate components / circuits, some or all of which may be integrated / removable and / or may provide permanent / semi-permanent / dynamic / cached storage.

[0321] Although processor 12 is illustrated as a single component / circuitry, it may be implemented as one or more separate components / circuits, some or all of which may be integrated / removable.Processor 12 may be a single-core or multi-core processor.

[0322] The apparatus may include one or more components for implementing the method described in the present disclosure and Figure 7 and Figure 10-12The methods, processes and procedures illustrated in the description are described herein. It is contemplated that the functions of these components may be combined in one or more components, or performed by other components having equivalent functionality. Additionally, the description of a function should be considered to also disclose any components suitable for performing that function. Where a structural feature has been described, the structural feature may be replaced by a component for performing one or more functions of the structural feature, whether the function or functions are explicitly or implicitly described.

[0323] Although examples of devices including various components have been described above, it should be understood that the components may be embodied as, or otherwise controlled by, corresponding controllers or circuit systems (such as one or more processing elements or processors of the device). In this regard, each of the above components may be one or more of any device, component, or circuit system embodied in hardware, software, or a combination of hardware and software, which is configured to perform the corresponding functions of the various components described above.

[0324] For example, the apparatus may be a client device, a server device, a mobile cellular phone, a base station in a mobile cellular telecommunication system, a wireless communication device, a handheld electronic device, a position / location tag, a super tag, etc. The apparatus may be embodied by a computing device, in particular a computing device such as mentioned above. However, in some examples, the apparatus may be embodied as a chip, a chipset, a circuit system or a module, i.e., for use in any of the above.

[0325] In one example, the apparatus is embodied on a handheld portable electronic device, such as a mobile phone, a mobile communication device, a wearable computing device, or a personal digital assistant, which may additionally provide one or more audio / text / video communication functions (e.g., telecommunication communication, video communication, and / or text transmission (Short Message Service (SMS) / Multimedia Message Service (MMS) / email) functions), interactive / non-interactive viewing functions (e.g., web browsing, navigation, TV / program viewing functions), music recording / playback functions (e.g., Moving Picture Experts Group-1 Audio Layer 3 (MP3) or other formats and / or (FM / AM) radio broadcast recording / playback), downloading / sending of data functions, image capture functions (e.g., using a (e.g., built-in) digital camera), and gaming functions, or any combination thereof.

[0326] In some examples, the apparatus includes:

[0327] at least one processor 12; and

[0328] At least one memory 13 stores instructions that, when executed by at least one processor 12, cause the apparatus to at least:

[0329] and determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on:

[0330] Information indicating at least one state of at least one last PSFCH transmission; or

[0331] Information indicating the propagation type of the sidelink (SL) transmission associated with the PSFCH transmission.

[0332] The above-mentioned device can be applied as an enabling component of the following items: telecommunication equipment, telecommunication systems; tracking systems, automotive systems; electronic systems, including consumer electronics; distributed computing systems; media systems for generating or rendering media content, which media content includes audio content, visual content and audio-visual content as well as mixed reality, mediated reality, virtual reality and / or augmented reality; personal systems, including personal health systems or personal fitness systems; navigation systems; user interfaces, also known as human-machine interfaces; networks, including cellular networks, non-cellular networks and fiber optic networks; self-organizing networks; the Internet; the Internet of Things (IOT); vehicle-to-everything (V2X), virtualized networks; and related software and services.

[0333] According to examples of the present disclosure, the device may be provided in an electronic device, such as a mobile terminal. However, it should be understood that the mobile terminal is merely an illustration of an electronic device that will benefit from the examples of implementation of the present disclosure, and therefore should not be considered to limit the scope of the present disclosure to this. Although in some implementation examples, the device may be provided in a mobile terminal, other types of electronic devices, such as but not limited to: mobile communication devices, location tags, handheld portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices, and other types of electronic systems, can easily adopt examples of the present disclosure. In addition, regardless of whether the device is intended to provide mobility, the device can easily adopt examples of the present disclosure.

[0334] Various examples of the present disclosure may take the form of computer program instructions. Such computer program instructions may be provided to one or more processors, processing circuit systems, or (multiple) controllers, so that the instructions executed thereon create components for implementing the functions discussed above, so that the method may be computer-implemented.

[0335] Fig. 9A computer program 14 is illustrated that may be communicated via a delivery mechanism 20. Delivery mechanism 20 may be any suitable delivery mechanism, for example, a machine-readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a solid-state memory, a recording medium such as a compact disk read-only memory (CD-ROM) or a digital versatile disk (DVD), or an article of manufacture that includes or tangibly embodies the computer program 14. The delivery mechanism may be a signal configured to reliably transmit the computer program. An apparatus may receive, propagate, or send a computer program as a computer data signal.

[0336] In some examples of the present disclosure, a computer program including instructions is provided, which, when executed by an apparatus (e.g., apparatus 10 that can be implemented in UE 110), causes the apparatus to perform at least the following items or cause at least the following operations to be performed:

[0337] and determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on:

[0338] Information indicating at least one state of at least one last PSFCH transmission; or

[0339] Information indicating the propagation type of the sidelink (SL) transmission associated with the PSFCH transmission.

[0340] References to "computer program", "computer readable storage medium", "computer program product", "tangibly embodied computer program", etc. or "controller", "computer", "processor", etc. should be understood to cover not only computers with different architectures (such as single processor architecture / multi-processor architecture and sequential (von Neumann) architecture / parallel architecture), but also special-purpose circuits such as field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), signal processing devices and other devices. References to computer programs, instructions, code, etc. should be understood to cover software or firmware for programmable processors, such as, for example, the programmable content of hardware devices, whether instructions for a processor, or configuration settings of a fixed-function device, gate array or programmable logic device, etc.

[0341] As used in this application, the term "circuitry" may refer to one, more, or all of the following:

[0342] (a) hardware circuitry implementation only (such as implementation only in analog circuitry and / or digital circuitry);

[0343] (b) a combination of hardware circuitry and software such as (where applicable):

[0344] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0345] (ii) any portion of hardware processor(s) and software (including digital signal processor(s), software, and memory(s) that act together to enable a device (such as a mobile phone or server) to perform various functions; and

[0346] (c) Hardware circuit(s) and / or processor(s) that require software (e.g., firmware) for operation, such as microprocessor(s) or portion(s) of microprocessor(s), but where the software is not required for operation, the software may not be present.

[0347] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term "circuitry" also covers an implementation of a hardware-only circuit or processor and its (or their) accompanying software and / or firmware. For example, and if applicable to a particular claim element, the term "circuitry" also covers a baseband integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0348] Fig.10 A flow chart of a method 1100 for selecting a CAPC for PSFCH transmission is shown. The method may be performed by a UE, such as a SL-U Rx UE (ie, a UE acting as a receiver of sidelink transmissions in an unlicensed band from a SL-U Tx UE).

[0349] In block 1101, the SL Rx UE obtains parameter configuration information for CAPC selection. Such parameter configuration information may include one or more previously discussed parameters used to determine and apply selection criteria / metrics to apply and evaluate the selection criteria / metrics. In this regard, the parameter configuration information may include:

[0350] First candidate CAPC p 1st ,

[0351] Second candidate CAPC p 2nd ,

[0352] Offset p offset ,

[0353] The threshold of LBT success rate (y%),

[0354] The threshold value for the number of LBT successes (y), and

[0355] The value of the number (x) of previous transmissions.

[0356] The network 100 and / or the gNB 120 may determine configuration information for CPAC selection (such as the first CAPC and / or the second CAPC, or the offset p offset ), and configure the SL Rx UE with the configuration information. The determination of the configuration information may be made taking into account, for example, implementation complexity, channel access opportunities, and / or coexistence fairness between different RATs / devices.

[0357] In implementation, to reduce UE implementation complexity, the first CAPC and / or the second CAPC may be configured by the network, and thus the SL Rx UE does not need to determine the CAPC (eg, based on traffic information).

[0358] In another implementation, to ensure coexistence fairness with other devices, the first CAPC may be configured with the highest CAPC (i.e., the lowest channel access priority, p=4), while the second CAPC may be configured with the lowest CAPC (i.e., the highest channel access priority, p=1) to increase channel access opportunities, such as in the case of HARQ-ACK / NACK retransmissions or low channel access success rates.

[0359] In another implementation, the offset p between the second CAPC and the first CAPC is offset It can be determined based on the channel access requirements of the UE or the service type. For example, for ultra-reliable low-latency communication (URLLC), the offset p offset Can be set to a high / large value (e.g., 2), otherwise it can be set to a low / small value (e.g., 1).

[0360] As discussed below with respect to block 1108, the values ​​of the parameters (e.g., x and y) may be used in part of the criteria / metric to determine whether to select the first CAPC or the second CAPC for PSFCH transmission. The parameter values ​​may be determined based on channel access requirements, e.g., the larger the value of y, the higher the channel access requirements; the larger the value of x, the longer the decision observation time.

[0361] In block 1101, one or more selection metrics may also be configured for the SL-U Rx UE for PSFCH transmission. The selection metric to be applied by the SL-U Rx EU may be based at least in part on: channel access status (e.g., whether a previous PSFCH transmission failed / was unsuccessful) or UE type (e.g., URLLC UE) or traffic type.

[0362] In some implementations, the parameter configuration information may be predefined during specification, or configured to the SL-U Rx UE by the network or via another SL UE.

[0363] In block 1102, the SL-U Rx UE monitors the PSCCH to determine the priority and resource allocation of SL transmissions from the SL-U Tx UE.

[0364] Priority may be determined based on traffic type and Quality of Service (QoS), such as defined in clause 5.4.3.3 of [12, TS 23.287]. SL-U Rx UEs may detect priority and resource allocation through the first stage SCI as discussed above.

[0365] In some implementations, SL transmissions may be limited to unicast transmissions or multicast transmissions towards SL-U Rx UEs. Such determination of the propagation type may be identified by detecting the propagation type and target ID in the second stage SCI provided in Table 2.

[0366] In box 1103, if HARQ-ACK feedback is expected for PSSCH by detecting the HARQ feedback enable / disable indicator in the second stage SCI provided in Table 2, the SL-U Rx UE determines the PSFCH timing for each SL transmission (i.e., PSSCH) based on the configured PSSCH to PSFCH timing.

[0367] In some implementations, the SL-U RX UE may determine the frequency domain location of the PSFCH transmission for HARQ feedback for the SL transmission based on the lowest physical resource block (PRB) index of the resource allocation for the SL transmission. The SL-U RX UE may also determine the time domain location of the HARQ feedback based on the predefined PSSCH to PSCCH timing for the SL transmission discussed above in the overview of SL HARQ operations.

[0368] In some implementations, the primary PSFCH opportunity and the secondary PSFCH opportunity may be configured for HARQ-ACK feedback associated with the SL transmission. If (multiple) HARQ-ACKs may not be sent as expected on the primary PSFCH opportunity (e.g., due to a failed LBT channel access procedure), the SL-U Rx UE may seek to send (i.e., retransmit) (multiple) HARQ-ACKs on the secondary PSFCH opportunity.

[0369] In block 1104, the SL Rx UE determines a first candidate CAPC p for PSFCH transmission. 1st and the second candidate CAPCp 2nd .

[0370] In this regard, in block 1105, if the first candidate CAPC and the second candidate CAPC are predefined or configured to the SL-U Rx UE, the SL-U Rx UE uses the predefined / configured first candidate CAPC and the second candidate CAPC. Otherwise, in block 1106, the SL-U Rx UE determines the first CAPC and / or the second CAPC to be used for PSFCH transmission at a given timing based on the priority of the associated SL transmission, such as in the manner previously discussed.

[0371] In block 1107: SL-U Rx UE selects the first candidate CAPC (p 1st ) and the second candidate CAPC (p 2nd ) to be used as CAPC(p) for PSFCH transmission. The selection is based on one or more selection criteria / metrics.

[0372] In some implementations, the selection metric(s) to be applied by the SL-U Rx UE may be predefined or configured to the SL Rx UE.

[0373] In block 1108, the SL-U Rx UE evaluates the selection metric(s) to determine in block 1109 whether the selection metric has been satisfied, and therefore determines whether to select:

[0374] According to block 1110 , use the first candidate CAPC for PSFCH transmission; or according to block 1111 , use the second candidate CAPC for PSFCH transmission.

[0375] In implementation, the channel access status of the last x PSFCH transmissions may be considered to implement the selection metric.

[0376] By default, if the second CAPC is not selected based on any of the configured selection metrics as follows, the SL-U Rx UE selects the first candidate CAPC for PSFCH transmission.

[0377] Selection metrics can include:

[0378] Metric 1-M1: If the PSFCH resource is a "secondary" PSFCH resource (i.e., a PSFCH resource that has been allocated to the SL-U Rx UE for retransmitting at least one HARQ-ACK on the PSFCH, which at least one HARQ-ACK was previously attempted to be sent via the "primary" PSFCH resource but was unsuccessful [e.g., due to failed LBT]), the SL Rx UE selects the second candidate CAPC.

[0379] In some instances, if there is an available COT, the first / primary PSFCH resource may use a type 2 channel access procedure, while for the second / secondary PSFCH resource, the UE may have to select a CAPC to initiate a type 1 LBT procedure, e.g., selecting a second candidate CPAC in the absence of an available COT.

[0380] Metric 2-M2: If the LBT success rate of the last x PSFCH transmissions is lower than the threshold success rate (y%), the SL-U RxUE selects the second candidate CAPC. In an example, the values ​​of x and y may be set to 2 and 50, respectively.

[0381] Metric 3-M3: If the number of LBT successes for the last x PSFCH transmissions is lower than y, then the SL Rx UE selects the second candidate CAPC. In an example, the values ​​of x and y may be set to 2 and 1, respectively.

[0382] Metric 4-M4: If the PSFCH transmission is within a COT initiated by another UE and the SL Rx UE is not the COT responder, the SL Rx UE selects the second candidate CAPC. The SL Rx UE can detect the COT information by monitoring the SCI of the other UE.

[0383] After selecting the first candidate CAPC or the second candidate CAPC to be used as the CAPC for PSFCH transmission, the SL-U RxUE determines the channel access parameters based on the selected CAPC for PSFCH transmission. The channel access parameters may include CW and / or COT, which may be determined based on the selected CAPC and the information provided in Table 1.

[0384] Then, in block 1112, the Rx UE performs LBT (eg, Type 1 LBT) using the determined channel access parameters, ie, seeks to acquire the "right" to access the channel to send a PSFCH transmission.

[0385] Fig.11 An example of determining a CAPC for PSFCH transmission according to the present disclosure is illustrated.

[0386] In this example, sidelink resource 2011 is allocated to sidelink transmission 2021 PSCCH / PSSCH A towards SL Rx UE at time slot #(n-3). Sidelink resource 2012 is allocated to sidelink transmission 2022 PSCCH / PSSCH B towards SL Rx UE at time slot #(n-4).

[0387] Based on the configured PSSCH to PSFCH timing, for the SL Rx UE on PSFCH 203 at slot #n, two PSSCH 2021 and 2022 respective HARQ feedback 2051 and HARQ feedback 2052 are necessary.

[0388] If the first candidate CAPC value p for PSFCH transmission 1st and the second candidate CAPC value P 2nd If the first and second CAPCs (referred to as the first and second CAPCs) are not predetermined or are not configured for the SL Rx UE, the SL Rx UE determines the priority of the SL transmission 2021 and the SL transmission 2022 based on the priorities of the SL transmission 2051 and the PSFCH transmission 2052 associated with the PSFCH 203. 1st and P 2nd , i.e. SL Rx UE determines the priority of the following items: PSSCH A (= P A ) and PSSCH B(p B ).

[0389] In this example, the first candidate CAPC p 1st Based on the lowest priority of PSSCH A / B, that is, p 1st =min(p A , p B ). The second candidate CAPC p 2nd Based on the highest priority of PSSCH A / B, that is, p 2nd =max(p A , p B ).

[0390] In this example, the selection metric M3 is applied, i.e., the SL Rx UE selects the node with p=p based on the selection metric M3. n CAPC for PSFCH transmission, where p n It is the first candidate CAPC p 1st , the second candidate CAPC p 2nd , and the previous PSFCH transmission LBT at slot #(n-4) and slot #(n-8) PSFCH 2041 and earlier PSFCH transmission LBT PSFCH The function of the LBT state of 2042 is:

[0391] p n =f(p 1st , p 2nd , LBT PSFCH ) (1)

[0392] In this particular example, for the selection metric M3, the value of x (the number of last PSFCH transmissions) is set to 2, and the value of y (the threshold number of LBT successes) is set to 1.

[0393] Therefore, if LBT fails for both the previous PSFCH transmission 2041 and the previous PSFCH transmission 2042 at both slot #(n-4) and slot #(n-8), the SL Rx UE will select the second candidate CAPC for the channel access procedure for the PSFCH transmission at slot #n, i.e., the SL Rx UE will select p=p 2nd Otherwise, the SL Rx UE will select the first candidate CAPC for the channel access procedure of the PSFCH transmission at time slot #n. In other words, if LBT fails for PSFCH transmission only at one of the previous PSFCH transmission 2041 and the previous PSFCH transmission 2042, or if LBT does not fail for both the previous PSFCH transmission 2041 and the previous PSFCH transmission 2042, the SL Rx UE will select p=p 1st .

[0394] Choose p based on the evaluation of the selection metric 1st or p 2nd After that, the SL Rx UE receives the CAPC (i.e., the selected p 1st or p 2nd ) performs the LBT process to seek to send PSFCH transmission 2051 via PSFCH 2031.

[0395] Fig.12 Another example of determining a CAPC for a PSFCH according to the present disclosure is illustrated.

[0396] In this example:

[0397] First candidate CAPC p 1st (referred to as the first CAPC) is determined based on the lowest priority of the associated PSSCH A / B 2021 and 2022, i.e., p 1st =min(p A ,p B );

[0398] Second candidate CAPC p 2nd (referred to as the second CAPC) is configured with the CAPC with the lowest possible p value, i.e., p 2nd = 1; and

[0399] Selection metric M1 is applicable to CAPC selection.

[0400] By default, the first candidate CAPC p will be selected1st For channel access, to send PSFCH transmission 2051 and PSFCH transmission 2052 via PSFCH 2031 at time slot #n, i.e., select p=p 1st However, in this particular example, since the previous transmission of HARQ feedback 2041 for PSCCH / PSSCH A 2021 on PSFCH 2032 was blocked at time slot #(n-4) due to LBT failure (where such previous PSFCH transmission 2041 had been allocated "primary" PSFCH resources 2061), the secondary PSFCH resources 2062 at time slot #n are configured to retransmit HARQ feedback 2051 for PSCCH / PSSCH A 2021 on PSFCH 2031. In this scenario, and based on the selection metric M1, the SL Rx UE selects the second candidate CAPC for sending PSFCH transmission 2051 on PSFCH 2031 at time slot #n, i.e., the SL Rx UE selects p=p 2nd The CAPC for PSFCH is thus determined (ie, in this example, p = p 2nd ) after which the SL Rx UE performs an LBT process based on the determined CAPC to seek to send a PSFCH transmission 2051 on the PSFCH 2031.

[0401] Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0402] Features described in the preceding description may be used in combinations other than the combinations explicitly described.

[0403] Although functions have been described with reference to certain features, that functionality may be performable by other features whether described or not.

[0404] Although a feature has been described with reference to certain examples, the feature may also be present in other examples, whether or not described. Therefore, a feature described in relation to one example / aspect of the disclosure may include any or all features described in relation to another example / aspect of the disclosure, and vice versa, as long as they are not mutually inconsistent.

[0405] Although the preceding paragraphs describe various examples of the present disclosure, it should be understood that the examples given may be modified without departing from the scope of the present invention as set forth in the claims. For example, the various examples described above have been disclosed with reference to a method performed by a SL-URx UE (e.g., a UE configured for SL communications in an unlicensed band, which acts as a receiver for SL transmissions initiated by a SL-U Tx UE), and wherein the transmission is a PSFCH transmission (such as HARQ feedback) sent over a PSFCH, and information indicating a channel access priority is determined for the transmission. However, it should be understood that the examples of the present disclosure are not limited to determining a priority for a PSFCH transmission, the transmission (for which information indicating a channel access priority is determined) being a PSFCH transmission, and the examples are not limited to SL communications and operations in an unlicensed band. In some examples, the transmission channel may be a PSSCH or a synchronization signal block (SSB).

[0406] The various examples described above have been disclosed with respect to determining a first candidate CPAC value and a second candidate CPAC value, and selecting one of the first CPAC and the second CPAC. However, it should be appreciated that in some examples, one or more additional candidate CPAC values ​​may be determined, and one or more of the plurality of candidate CPAC values ​​may be selected.

[0407] The term "comprising" as used in this document has an inclusive rather than an exclusive meaning. That is, any reference to X including Y indicates that X may include only one Y, or may include multiple Ys. If "comprising" is intended to be used in an exclusive sense, this is made clear in the context by reference to "including only one..." or by use of "consisting of..."

[0408] In this description, the words "connected", "coupled" and "in communication" and their derivatives mean operationally connected / coupled / in communication. It should be understood that there may be any number of intermediate components, or any combination of intermediate components (including no intermediate components), i.e., to provide direct or indirect connection / coupling / in communication. Any such intermediate components may include hardware components and / or software components.

[0409] As used herein, the terms "determine / determining" (and grammatical variations thereof) may include, but are not limited to: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (e.g., looking up in a table, a database, or another data structure), ascertaining, etc. Furthermore, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), obtaining, etc. Furthermore, "determining" may include resolving, selecting, choosing, establishing, etc.

[0410] If not explicitly stated, the parameters (e.g. 1st 、p 2nd 、p offset , x, y and y%) may be replaced by references to “data indicating the relevant parameters”, “data defining the relevant parameters” or “data representing the relevant parameters”.

[0411] In this description, reference has been made to various examples. A description of a feature or function associated with an example indicates that the feature or function is present in the example. Whether explicitly stated or not, the use of the term "example" or "for example", "may" or "can" herein indicates that such features or functions are present in at least the example described, whether or not described as an example, and they may be present in some or all other examples, but not necessarily. Therefore, "example", "for example", "may" or "can" refers to a specific instance in a category of examples. The attributes of an instance may be attributes of only the instance, or may be attributes of the category, or may be attributes of a subcategory of the category, which subcategory includes some but not all instances in the class.

[0412] In this specification, unless otherwise clearly stated, reference to "a kind of / an / the" [feature, element, assembly, part ...] is used with inclusive meaning rather than exclusive meaning, and should be interpreted as "at least one" [feature, element, assembly, part ...]. That is, any reference to X including one / the Y indicates that X can include only one Y or can include multiple Ys, unless the context clearly indicates the opposite. If it is intended to use "one" or "the" with exclusive meaning, it should be clearly stated in the context. In some cases, the use of "at least one" or "one or more" can be used to emphasize inclusive meaning, but the absence of these terms should not be considered to mean any exclusive meaning. As used herein, "at least one of the following: <list of two or more elements>" and "at least one of <list of two or more elements>" and similar wording, wherein the list of two or more elements is connected by "and" or "or", meaning at least any one of the element, or at least any two or more of the element, or at least all of the element.

[0413] The presence of a feature (or combination of features) in a claim is a reference to the feature (or combination of features) itself, and is also a reference to features that achieve substantially the same technical effect (equivalent features). Equivalent features include, for example, features that are variants, and that achieve substantially the same result in substantially the same way. Equivalent features include, for example, features that perform substantially the same function in substantially the same way to achieve substantially the same result.

[0414] In this specification, reference has been made to various examples using adjectives or adjective phrases to describe characteristics of the examples. Such description of characteristics associated with the examples indicates that the characteristics exist in some examples exactly as described, and in other examples substantially as described.

[0415] In the above description, the device may alternatively or additionally include a device that includes a distributed system of devices in some other examples, such as a client / server device system. In the example where the provided device forms (or the method is implemented as) a distributed system, each device that forms a component and / or part of the system provides (or implements) one or more features that together implement the examples of the present disclosure. In some examples, the device is reconfigured by an entity other than its original manufacturer to implement the examples of the present disclosure by providing additional software (e.g., such software is downloaded by a user), and when the software is executed, the software causes the device to implement the examples of the present disclosure (such implementation is either fully implemented by the device, or as part of a device system as mentioned above).

[0416] The above description describes some examples of the present disclosure, however, those of ordinary skill in the art will be aware of possible alternative structures and method features that provide functionality equivalent to the specific examples of such structures and features described above, and have been omitted from the above description for the sake of brevity and clarity. Nevertheless, the above description should be interpreted as implicitly including references to such alternative structures and method features that provide equivalent functionality, unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

[0417] While efforts have been made in the foregoing description to call attention to those features of the examples of the present disclosure believed to be particularly important, it should be understood that the applicant claims protection for any patentable feature or combination of features mentioned above and / or shown in the accompanying drawings, whether or not specifically emphasized.

[0418] The examples of the present disclosure and the appended claims may be appropriately combined in any manner apparent to those skilled in the art. Separate references to "examples," "in some examples," etc. in the description do not necessarily refer to the same example, and are not mutually exclusive unless so stated and / or unless it is readily apparent to those skilled in the art from the description. For example, features, structures, processes, blocks, steps, actions, etc. described in one example may also be included in other examples, but are not necessarily included.

[0419] Each claim is incorporated into the specification as an additional disclosure, and the claims are (multiple) embodiments of the present disclosure. In addition, although the claims herein include specific dependencies, it is contemplated that any claim may be dependent on any other claim, and as long as any alternative embodiments can be generated by combining, integrating and / or omitting the features of the individual claims and / or changing the dependencies of the claims, any such alternative embodiments and their equivalents are also within the scope of the present disclosure.

Claims

1. A device comprising: Means for determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on: Information indicating at least one state of at least one last PSFCH transmission; or Information indicating the propagation type of the sidelink SL transmission associated with the PSFCH transmission.

2. The apparatus of claim 1, wherein the PSFCH transmission is in an unlicensed frequency band.

3. The apparatus according to any one of the preceding claims, wherein the information indicating the channel access priority indicates at least one item selected from the group consisting of: Priority categories used in the Listen Before Speak (LBT) process; Priority classes for use in unlicensed bands; Channel access priority category CAPC; Contention window CW; as well as Channel occupation time COT.

4. The apparatus according to any one of the preceding claims, wherein the information indicating at least one state of the last at least one PSFCH transmission comprises information indicating at least one item selected from the group consisting of: the channel access state of the last at least one PSFCH transmission; whether the last at least one PSFCH transmission failed or succeeded; whether the LBT procedure for sending the last at least one PSFCH transmission failed or succeeded; LBT success rate for the last one or more PSFCH transmissions; The number of LBT successes for the last one or more PSFCH transmissions; whether the PSFCH transmission includes a retransmission of information that was not successfully sent via the last at least one PSFCH transmission; allocation of resources for the PSFCH transmission, wherein the resources are allocated for retransmission of information that was not successfully transmitted via the last at least one PSFCH transmission; as well as Whether the PSFCH transmission is within the channel occupation time COT shared by the UE.

5. The apparatus of any preceding claim, wherein the means for determining information indicative of the channel access priority for the PSFCH transmission comprises: means for determining a first candidate priority class for said PSFCH transmission; means for determining a second candidate priority class for said PSFCH transmission; as well as Means for selecting at least one of a first candidate priority category and a second candidate priority category.

6. The apparatus of claim 5, wherein at least one item is selected from the group consisting of: The first candidate priority category and / or the second candidate priority category are predefined; The first candidate priority category and / or the second candidate priority category are configured to the device; the first candidate priority class being configured to have a lower channel access priority than the second candidate priority class; The first candidate priority category is determined based at least in part on a channel access priority of one or more SL transmissions associated with the transmission; The second candidate priority category is determined based at least in part on a channel access priority of one or more SL transmissions associated with the transmission; the second candidate priority category being determined based at least in part on the first candidate priority category; as well as The second candidate priority class is determined based at least in part on the first candidate priority class and a priority class offset.

7. The apparatus according to claim 5 or 6, wherein the means for selecting one of the first candidate priority category and the second candidate priority category comprises: Means for selecting one of the first candidate priority category and the second candidate priority category based on at least one selection criterion.

8. The apparatus of claim 7, wherein the at least one selection criterion comprises selecting the first candidate priority category by default.

9. The apparatus of claim 7 or 8, wherein the at least one selection criterion comprises selecting the second candidate priority category in response to at least one of: determining whether the PSFCH transmission is a retransmission of at least a portion of a previously attempted PSFCH transmission; determining whether the PSFCH transmission is a retransmission of a previous attempt to send feedback; determining whether the PSFCH transmission is a retransmission of a previous attempt to send a hybrid automatic repeat request acknowledgement HARQ-ACK or a negative acknowledgement NACK; determining a type of resource used for the PSFCH transmission; determining whether the resources allocated for the PSFCH transmission are resources allocated for retransmitting information that failed to be successfully transmitted via the last at least one PSFCH transmission; as well as Determine whether at least one HARQ-ACK of the last one or more PSFCH transmissions failed to be sent via earlier allocated resources due to LBT failure.

10. The apparatus of any one of claims 7 to 9, wherein the at least one selection criterion comprises selecting the second candidate priority category in response to: Determine whether the LBT success rate of multiple previous PSFCH transmissions is less than a threshold.

11. The apparatus of any one of claims 7 to 10, wherein the at least one selection criterion comprises selecting the second candidate priority category in response to: Determine whether the number of LBT successes of multiple last PSFCH transmissions is less than a threshold.

12. The apparatus of any one of claims 7 to 11, wherein the at least one selection criterion comprises selecting the second candidate priority category in response to: Determine whether the SL transmission is a unicast transmission.

13. The device according to any one of claims 7 to 12, further comprising: Means for receiving configuration information for enabling the apparatus to determine the at least one selection criterion to be applied for selecting one of the first candidate priority category and the second candidate priority category.

14. The device according to any one of claims 7 to 13, further comprising: Means for determining at least one selection criterion to be applied based at least in part on a propagation type of the SL transmission associated with the PSFCH transmission.

15. The apparatus according to any one of the preceding claims, further comprising: Means for receiving configuration information for enabling said apparatus to determine said information indicative of said channel access priority for said PSFCH transmission.

16. The apparatus of claim 15, wherein the configuration information comprises an indication of at least one item selected from the group consisting of: First candidate priority category; Second candidate priority category; an offset between the first candidate priority class and the second candidate priority class; Number of last PSFCH transmissions; Threshold transmission success rate; The threshold number of successful transmissions; the propagation type of the SL transmission associated with the PSFCH transmission; and One or more selection criteria to be applied by the device.

17. The apparatus of any preceding claim, wherein the propagation type comprises at least one of: multicast and unicast.

18. An apparatus according to any of the preceding claims, wherein the SL transmission associated with the PSFCH transmission comprises a Physical Sidelink Shared Channel (PSSCH) transmission.

19. The apparatus according to any one of the preceding claims further comprising: Means for causing performance of a channel access procedure for sending the transmission based at least in part on the determined information indicative of a channel access priority.

20. A chipset, circuitry or module comprising an apparatus according to any preceding claim.

21. A user equipment UE, comprising the apparatus according to any one of claims 1 to 19 or the chipset, circuit system or module according to claim 20.

22. A method comprising causing, at least in part, actions resulting in: determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on: Information indicating at least one state of at least one last PSFCH transmission; or Information indicating the propagation type of the sidelink SL transmission associated with the PSFCH transmission.

23. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus to: determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on: Information indicating at least one state of at least one last PSFCH transmission; or Information indicating the propagation type of the sidelink SL transmission associated with the PSFCH transmission.

24. An apparatus comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on: Information indicating at least one state of at least one last PSFCH transmission; or Information indicating the propagation type of the sidelink SL transmission associated with the PSFCH transmission.

25. The apparatus of claim 24, wherein the PSFCH transmission is in an unlicensed band.

26. The apparatus according to any one of the preceding claims 24 to 25, wherein the information indicating the channel access priority indicates at least one item selected from the group consisting of: Priority categories used in the Listen Before Speak (LBT) process; Priority classes for use in unlicensed bands; Channel access priority category CAPC; Contention window CW; as well as Channel occupation time COT.

27. The apparatus according to any one of the preceding claims 24 to 26, wherein the information indicating at least one state of the last at least one PSFCH transmission comprises information indicating at least one item selected from the group of: the channel access state of the last at least one PSFCH transmission; whether the last at least one PSFCH transmission failed or succeeded; whether the LBT procedure for sending the last at least one PSFCH transmission failed or succeeded; LBT success rate for the last one or more PSFCH transmissions; The number of LBT successes for the last one or more PSFCH transmissions; whether the PSFCH transmission includes a retransmission of information that was not successfully sent via the last at least one PSFCH transmission; allocation of resources for the PSFCH transmission, wherein the resources are allocated for retransmission of information that was not successfully transmitted via the last at least one PSFCH transmission; as well as Whether the PSFCH transmission is within the channel occupation time COT shared by the UE.

28. The apparatus of any preceding claim 24 to 27, wherein determining information indicative of the channel access priority for the PSFCH transmission comprises: determining a first candidate priority class for the PSFCH transmission; determining a second candidate priority class for the PSFCH transmission; as well as At least one candidate priority category of the first candidate priority category and the second candidate priority category is selected.

29. The apparatus of claim 28, wherein at least one item is selected from the group consisting of: The first candidate priority category and / or the second candidate priority category are predefined; The first candidate priority category and / or the second candidate priority category are configured to the device; the first candidate priority class being configured to have a lower channel access priority than the second candidate priority class; The first candidate priority category is determined based at least in part on a channel access priority of one or more SL transmissions associated with the transmission; The second candidate priority category is determined based at least in part on a channel access priority of one or more SL transmissions associated with the transmission; the second candidate priority category being determined based at least in part on the first candidate priority category; as well as The second candidate priority class is determined based at least in part on the first candidate priority class and a priority class offset.

30. An apparatus according to claim 28 or 29, wherein selecting one of the first candidate priority category and the second candidate priority category includes selecting one of the first candidate priority category and the second candidate priority category based on at least one selection criterion.

31. The apparatus of claim 30, wherein the at least one selection criterion comprises selecting the first candidate priority category by default.

32. An apparatus according to claim 30 or 31, wherein the at least one selection criterion comprises selecting the second candidate priority category in response to at least one of: determining whether the PSFCH transmission is a retransmission of at least a portion of a previously attempted PSFCH transmission; determining whether the PSFCH transmission is a retransmission of a previous attempt to send feedback; determining whether the PSFCH transmission is a retransmission of a previous attempt to send a hybrid automatic repeat request acknowledgement HARQ-ACK or a negative acknowledgement NACK; determining a type of resource used for the PSFCH transmission; determining whether the resources allocated for the PSFCH transmission are resources allocated for retransmitting information that failed to be successfully transmitted via the last at least one PSFCH transmission; as well as Determine whether at least one HARQ-ACK of the last one or more PSFCH transmissions failed to be sent via earlier allocated resources due to LBT failure.

33. An apparatus according to any one of claims 30 to 32, wherein the at least one selection criterion comprises selecting the second candidate priority category in response to: Determine whether the LBT success rate of multiple previous PSFCH transmissions is less than a threshold.

34. An apparatus according to any one of claims 30 to 33, wherein the at least one selection criterion comprises selecting the second candidate priority category in response to: Determine whether the number of LBT successes of multiple last PSFCH transmissions is less than a threshold.

35. An apparatus according to any one of claims 30 to 34, wherein the at least one selection criterion comprises selecting the second candidate priority category in response to: Determine whether the SL transmission is a unicast transmission.

36. The apparatus of any one of claims 30 to 35, wherein the instructions, when executed by the at least one processor, further cause the apparatus to: Configuration information is received, the configuration information being used to enable the apparatus to determine the at least one selection criterion to be applied for selecting one of the first candidate priority category and the second candidate priority category.

37. The apparatus of any one of claims 30 to 36, wherein the instructions, when executed by the at least one processor, further cause the apparatus to perform: At least one selection criterion to be applied is determined based at least in part on a propagation type of the SL transmission associated with the PSFCH transmission.

38. The apparatus of any one of claims 24 to 37, wherein the instructions, when executed by the at least one processor, further cause the apparatus to perform: Configuration information is received, the configuration information being used to enable the apparatus to determine the information indicating the channel access priority for the PSFCH transmission.

39. The apparatus of claim 38, wherein the configuration information comprises an indication of at least one item selected from the group consisting of: First candidate priority category; Second candidate priority category; an offset between the first candidate priority class and the second candidate priority class; Number of last PSFCH transmissions; Threshold transmission success rate; The threshold number of successful transmissions; the propagation type of the SL transmission associated with the PSFCH transmission; and One or more selection criteria to be applied by the device.

40. The apparatus of any one of claims 24 to 39, wherein the propagation type comprises at least one of: multicast and unicast.

41. An apparatus according to any one of claims 24 to 37, wherein the SL transmission associated with the PSFCH transmission comprises a physical sidelink shared channel (PSSCH) transmission.

42. The apparatus of any one of claims 24 to 37, wherein the instructions, when executed by the at least one processor, further cause the apparatus to: Performance of a channel access procedure for sending the transmission is caused based at least in part on the determined information indicative of a channel access priority.

43. A chipset, a circuit system or a module, comprising the apparatus according to any one of the preceding claims 24 to 42.

44. A user equipment UE, comprising the device according to any one of the preceding claims 24 to 42 or the chipset, circuit system or module according to claim 43.

45. A non-transitory computer readable medium encoded with instructions that, when executed by at least one processor, cause at least the following to be performed: determining information indicating a channel access priority for a physical sidelink feedback channel (PSFCH) transmission based at least in part on: Information indicating at least one state of at least one last PSFCH transmission; or Information indicating the propagation type of the sidelink SL transmission associated with the PSFCH transmission.

Images