Use of short control signaling for PSFCH

Abstract

Example embodiments of the present disclosure relate to devices, methods, apparatuses, and computer readable media for transmitting a physical sidelink feedback channel (PSFCH) using short control signaling (SCSt). In an example method, a terminal device determines a sidelink configuration, the sidelink configuration including at least a sidelink synchronization signal block (SL-SSB) configuration and a PSFCH configuration. The terminal device transmits the PSFCH via SCSt or after a listen-before-talk (LBT) process succeeds based on the sidelink configuration. In this manner, the terminal device maximizes the opportunity of transmitting the expected PSFCH, so that its transmission is not blocked due to unsuccessful LBT.

Description

Technical Field

[0001] Example embodiments of the present disclosure generally relate to the field of communications, and in particular to a terminal device, method, apparatus, and computer-readable medium for transmitting a physical sidelink feedback channel (PSFCH) using short control signaling transmission (SCSt). Background Art

[0002] SL-U standardization in 3GPP Release 18 is ongoing, and the latest work item description (WID) on the evolution of the New Radio (NR) sidelink includes a channel access mechanism from NR-U that will be reused for sidelink unlicensed operation. In RAN1#111-e, it was also agreed that the Type 2A channel access procedure applies to sidelink synchronization signal block (SL-SSB) transmissions from UEs without shared channel occupancy. For combined transmissions of both SL-SSB and PSFCH using the Type 2A channel access procedure, whether PSFCH should also be allowed to be listed as FFS. Therefore, a solution for PSFCH transmissions without channel occupancy needs to be studied to enhance SL-U. Summary of the Invention

[0003] Generally, example embodiments of the present disclosure provide solutions for PSFCH transmission using short control signaling transmission (SCSt) in conjunction with SL-SSB transmission.

[0004] In a first aspect, a terminal device is provided. The terminal device includes at least one processor and at least one memory storing instructions, wherein the instructions, when executed by the at least one processor, cause the terminal device to at least: determine a sidelink configuration, the sidelink configuration including at least a sidelink synchronization signal block (SL-SSB) configuration and a physical sidelink feedback channel (PSFCH) configuration; and transmit the PSFCH via short control signaling transmission (SCSt) or after a listen-before-talk (LBT) procedure succeeds based on the sidelink configuration.

[0005] In a second aspect, a method is provided. The method includes: determining, at a terminal device, a sidelink configuration, the sidelink configuration including at least a sidelink synchronization signal block (SL-SSB) configuration and a physical sidelink feedback channel (PSFCH) configuration; and transmitting the PSFCH based on the sidelink configuration via short control signaling transmission (SCSt) or after a listen-before-talk (LBT) procedure is successful.

[0006] In a third aspect, an apparatus is provided. The apparatus includes: a component for determining a sidelink configuration at a terminal device, the sidelink configuration including at least a sidelink synchronization signal block (SL-SSB) configuration and a physical sidelink feedback channel (PSFCH) configuration; and a component for transmitting the PSFCH based on the sidelink configuration via short control signaling (SCSt) or after a successful listen-before-talk (LBT) procedure.

[0007] In a fourth aspect, a non-transitory computer-readable storage medium having instructions stored thereon is provided, wherein when the instructions are executed on at least one processor, the at least one processor is caused to perform the method of the second aspect.

[0008] In a fifth aspect, a computer program comprising instructions is provided, which, when executed by an apparatus, causes the apparatus to at least: determine a side link configuration, the side link configuration comprising at least a side link synchronization signal block (SL-SSB) configuration and a physical side link feedback channel (PSFCH) configuration; and send the PSFCH based on the side link configuration via short control signaling transmission (SCSt) or after a listen-before-talk (LBT) procedure is successful.

[0009] In a sixth aspect, a terminal device is provided. The terminal device includes: a determination circuit system configured to determine a sidelink configuration, the sidelink configuration including at least a sidelink synchronization signal block (SL-SSB) configuration and a physical sidelink feedback channel (PSFCH) configuration; and a transmission circuit system configured to transmit the PSFCH via short control signaling transmission (SCSt) or after a listen-before-talk (LBT) procedure is successful based on the sidelink configuration.

[0010] It should be understood that the invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0012] Figure 1A illustrates examples of application scenarios in which some example embodiments of the present disclosure may be implemented;

[0013] Figure 1B FIGURE 1 illustrates obtaining channel occupancy time by an initiating device via LBT Type 1 according to some example embodiments of the present disclosure;

[0014] Figure 1C illustrates transmission using a simplified LBT process according to some example embodiments of the present disclosure;

[0015] Figure 1D An example diagram illustrating when a responding device must acquire a new COT according to some example embodiments of the present disclosure;

[0016] Figure 1E illustrates an example SL-SSB period according to some example embodiments of the present disclosure;

[0017] Figure 1F illustrates an example of an SCSt budget and an observation window around an SL-SSB transmission according to some example embodiments of the present disclosure;

[0018] Figure 2 A flowchart illustrating an example method implemented at a terminal device according to some embodiments of the present disclosure;

[0019] Figure 3 A flowchart illustrating another example method implemented at a terminal device according to some embodiments of the present disclosure;

[0020] Figure 4 illustrates a simplified block diagram of a device suitable for implementing some example embodiments of the present disclosure; and

[0021] Figure 5 A block diagram illustrating an example of a computer-readable medium according to some example embodiments of the present disclosure.

[0022] Throughout the drawings, the same or similar reference numerals denote the same or similar elements. DETAILED DESCRIPTION

[0023] The principles of the present disclosure will now be described with reference to some exemplary embodiments. It should be understood that these embodiments are described for illustrative purposes only and to help those skilled in the art understand and implement the present disclosure without implying any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various ways different from the ways described below.

[0024] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0025] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Furthermore, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is considered to be within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0026] It should be understood that although the terms "first" and "second" and the like are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the example embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0027] The term used herein is only for the purpose of describing specific embodiments, and is not intended to limit example embodiments. As used herein, the singular "a", "an" and "the" are also intended to include plural forms, unless the context clearly indicates otherwise. It will also be understood that the terms "comprises", "comprising", "has", "having", "includes" and / or "including" specify the existence of the features, elements and / or components when used herein, but do not exclude the existence or addition of one or more other features, elements, components and / or their combinations. As used herein, "at least one of the following: <list of two or more elements>" and "at least one of the list of two or more elements>" and similar wording, wherein the list of two or more elements is connected by "and" or "or", representing at least any one element in these elements, or at least any two or more elements, or at least all elements.

[0028] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0029] (a) hardware circuit implementation only (such as implementation only in analog and / or digital circuitry) and

[0030] (b) a combination of hardware circuitry and software such as (as applicable):

[0031] (i) a combination of (one or more) analog and / or digital hardware circuits and software / firmware, and

[0032] (ii) any portion of hardware processor(s) (including digital signal processor(s)), software and memory(s) with software that work together to enable a device such as a mobile phone or server to perform various functions, and

[0033] (c)(one or more) hardware circuits and / or(one or more) processors, such as(one or more) microprocessors or portions of(one or more) microprocessors, that require software (e.g., firmware) to operate, but the software may not be present when not required for operation.

[0034] This definition of circuitry applies to all uses of the term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers merely a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware implementation. For example, and if applicable to a particular claim element, the term "circuitry" also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0035] As used herein, the terms "network", "communication network" or "data network" refer to a network that complies with any suitable communication standard, such as Long Term Evolution (LTE), Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), Wireless Fidelity (Wi-Fi), etc. In addition, the communication between the terminal devices and the network devices / elements in the communication network can be performed according to any suitable generation of communication protocols, including but not limited to the fourth generation (4G), 4.5G, the future fifth generation (5G), IEEE 802.11 communication protocols, and / or any other protocols currently known or to be developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communications, there are of course future types of communication technologies and systems in which the present disclosure can be embodied. It should not be regarded as limiting the scope of the present disclosure to only the above-mentioned systems.

[0036] As used herein, the term "network device" refers to a node in a communication network, via which a terminal device accesses the network and receives services from it. Depending on the terminology and technology used, a network device may refer to a base station (BS) or an access point (AP), such as a Node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a WiFi device, a relay, a low-power node such as a femto, a pico, etc. In the following description, the terms "network device", "AP device", "AP" and "access point" may be used interchangeably.

[0037] The term "terminal device" refers to any terminal device capable of wireless communication. By way of example and not limitation, a terminal device may also be referred to as a communication device, user equipment (UE), subscriber station (SS), portable subscriber station, mobile station (MS), station (STA) or station device, or access terminal (AT). Terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image capture terminal devices such as digital cameras, game terminal devices, music storage and playback devices, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop mounted devices (LMEs), USB dongles, smart devices, wireless customer premises equipment (CPEs), Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated process chains), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. In the following description, the terms "station," "station device," "STA," "terminal device," "communication device," "terminal," "user equipment," and "UE" may be used interchangeably.

[0038] Sidelink Unlicensed (SL-U) standardization in Release 18 is ongoing, and the latest WID on NR sidelink evolution includes the following goals for operating the sidelink in unlicensed spectrum:

[0039]

[0040]

[0041] In 3GPP RAN1#111-e, the following content related to the applicability of Type 2A is also agreed. The embodiments of the present disclosure handle FFS as follows. Therefore, it is necessary to study a solution for PSFCH transmission without channel occupancy.

[0042]

[0043] The following describes the expected behavior of a UE when accessing unlicensed spectrum for sidelink transmissions based on the current specifications governing uplink transmissions in unlicensed spectrum (see TS 37.213). Sidelink operation in unlicensed spectrum is similar to uplink operation in unlicensed spectrum, with the main difference being that the intended receiver of the communication in the sidelink communication is another UE (in the case of sidelink unicast) or a collection of UEs (in the case of sidelink multicast and broadcast).

[0044] In the present disclosure, a solution is introduced to support efficient PFSCH transmission without shared channel occupancy for the combined transmission of both SL-SSB (interchangeably used as "S-SSB" in this specification) and PSFCH. In this solution, the UE determines the sidelink configuration, which includes at least the SL-SSB configuration and the PSFCH configuration. Based on the sidelink configuration, the UE determines whether to perform a type 1 listen-before-talk (LBT) process or to use short control signaling transmission (SCSt) for transmitting PSFCH. Short control signaling transmission is performed using LBT type 2C in one embodiment and not using LBT in another embodiment. In some embodiments, the UE may consider SCSt constraints related to limited SCSt usage (e.g., total time) within a period in which SL-SSB is also sent via SCSt. The UE may establish a variable called the PSFCH SCSt usage budget, which may be consumed or compared with the current SCSt usage within a (sliding or moving) observation period. The UE may check the budget before sending PSFCH via SCSt. In some embodiments, the UE can establish priority rules to prioritize certain PSFCH opportunities over other PSFCH opportunities, thereby spreading the budget over a longer period of time. In this way, the solution maximizes the chance of transmitting PSFCH when expected so that its transmission is not blocked due to, for example, an unsuccessful LBT (e.g., Type 1) procedure as described below.

[0045] For the purpose of illustration, reference will be made to Figures 1A to 5 However, it should be noted that these embodiments are given to enable those skilled in the art to understand the inventive concepts of the present disclosure and implement the solutions proposed herein, and are not intended to limit the scope of the present application in any way.

[0046] Figure 1A An example of an application scenario 100 in which some example embodiments of the present disclosure may be implemented is illustrated. The application scenario 100, as part of a communication network, includes a terminal device and a network device.

[0047] like Figure 1A As shown in FIG, the communication network 100 may include a network device 110 (which may also be referred to as a gNB or BS). The communication network 100-1 may also include terminal devices 120-1 and 120-2 (which may also be referred to as user equipment 120 or UE 120). Figure 1A Only one network device 110 and two terminal devices 120-1 and 120-2 are shown in FIG. 1 , but the number of network devices and terminal devices is not limited. In other words, there may be one or more network devices 110 and one or more terminal devices 120 in the network.

[0048] For illustration purposes, communication links 130-1 and 130-2 may be established between network device 110 and terminal device 120-1 or 120-2. Typically, communication between network device 110 and terminal device 120-1 or 120-2 may be a wide area network (WAN) communication or a local area network (LAN) communication.

[0049] For illustrative purposes, a direct device-to-device (D2D) link 140 may be established between terminal device 120-1 and terminal device 120-2. Typically, D2D communication between terminal device 120-1 and terminal device 120-2 may also be referred to as sidelink communication or sidelink direct communication, sometimes denoted by the abbreviations "SL" or "SLD." Sidelink communication refers to a wireless technology that enables different devices to communicate directly with each other without routing data paths through a network device. In the following description, the terms "D2D communication," "sidelink communication," "SL," and "SLD" may be used interchangeably.

[0050] The communication between the network device 110 and the terminal device 120-1 or 120-2 in the application scenario 100 can conform to any suitable standard, including but not limited to Long Term Evolution (LTE), LTE Evolution, Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), Wireless Fidelity (Wi-Fi), etc. In addition, the communication can be performed according to any generation of communication protocols currently known or to be developed in the future. Examples of communication protocols include but are not limited to first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G), 5.5G, 5G advanced network, sixth generation (6G), or IEEE 802.11 communication protocols.

[0051] It should be understood that Figure 1A The number of devices and their connection relationships and types shown in FIG are for illustrative purposes only and do not imply any limitation. Application scenario 100 may include any suitable number of devices suitable for implementing the embodiments of the present disclosure.

[0052] In the unlicensed bands below 7 GHz, the coexistence of New Radio (NR) and other systems (such as IEEE 802.11) is ensured via the LBT channel access mechanism, in which a UE intending to perform a sidelink transmission first needs to successfully complete an LBT check before being able to initiate a sidelink transmission. The LBT process may also be referred to as a Clear Channel Assessment (CCA) or a channel access process.

[0053] For a UE to pass the LBT check, it must observe that the channel is available for multiple consecutive CCA slots. Figure 1B The diagram illustrates clear channel assessment (CCA) slots according to some example embodiments of the present disclosure. In unlicensed bands below 7 GHz, the duration of these slots is 9 μs. The UE considers the channel to be available in a CCA slot if the measured power (i.e., the energy collected during the CCA slot) is below a regulatory energy detection threshold, which may depend on the operating band and geographic region.

[0054] When a UE initiates communication (i.e., the UE acts as an initiating device), the UE must obtain "rights" to access the channel for a specific period of time (denoted as the Channel Occupancy Time (COT) in the specification) by applying an "extended" LBT procedure, where the channel must be considered idle for the entire duration of the Contention Window (CW). This "extended" LBT procedure is generally referred to as LBT Type 1 as specified in TS 37.213.

[0055] Figure 1B The acquisition of COT by an initiating device via LBT Type 1 according to some example embodiments of the present disclosure is illustrated. It can be seen that if LBT Type 1 in the CW duration is successful, the initiating device will acquire "rights" to access the channel for the COT duration.

[0056] As shown in Table 1, the duration of COT and CW depends on the channel access priority class (CAPC) associated with the UE's traffic. Control plane traffic (such as PSCCH) is transmitted with p=1, while user plane traffic has p>1. In Table 1, LBT Type 1 details for the Uu uplink (UL) case are described. 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 For the downlink (DL) case, LBT type 1 parameters can in principle also be adopted in SL.

[0057] Table 1: Channel Access Priority Class (CAPC) for UL

[0058]

[0059] According to Table 1, 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 given.

[0060] After successfully completing the LBT Type 1 check, the UE initiating the transmission (the initiating device) obtains a COT with a duration associated with the corresponding CAPC. The obtained COT is valid even if the initiating device suspends its transmission. If the initiating device wants to perform a new transmission (within the COT), it still needs to perform the "simplified" LBT procedure.

[0061] Figure 1C The diagram illustrates transmission using a simplified LBT procedure according to some example embodiments of the present disclosure. The "simplified" LBT procedure is generally referred to as LBT Type 2 [see TS 37.213], with the following variants:

[0062] Type 2A (25μs LBT) - for SL transmissions within the COT acquired by the initiator (in the case where the gap between two SL transmissions is ≥ 25μs, and for an SL transmission that follows another SL transmission), Figure 1C are depicted in scenes (c) and (f);

[0063] Type 2B (16μs LBT) - for SL transmission within the COT acquired by the initiator (can only be used for SL transmission after another SL with a gap exactly equal to 16μs), Figure 1C The scenes (b) and (e) are depicted;

[0064] Type 2C (no LBT) - for SL transmission within COT acquired by the initiator (can only be used for SL transmissions with gaps < 16 μs and an allowed duration of SL transmission of

[0065] ≤584μs after another SL transmission), in Figure 1C The scenes (a) and (d) are depicted.

[0066] Figure 1C Scenarios (a), (b) and (c) show the case where the gap is between two transmissions from the initiating UE. Figure 1C Scenarios (d), (e) and (f) show the case where the gap is between two different transmissions from the initiating UE and the responding UE.

[0067] The initiating device can share its acquired COT with its intended receiver (e.g., the responding device). To do this, the initiating device should inform the responding device (e.g., via control signaling) about the duration of the COT. The responding device then uses this information to decide which type of LBT it should apply after performing a transmission to which the intended receiver is the initiating device. In the event that the responding device transmission falls outside the COT, the responding device will have to use LBT Type 1 with the appropriate CAPC to acquire a new COT.

[0068] Figure 1D An example diagram is shown when a responding device must acquire a new COT associated with some example embodiments of the present disclosure. As shown in FIG1L , when UE B determines that its transmission falls outside the COT initiated by UE A, it needs to acquire a new COT for sidelink transmissions to UE C.

[0069] Short control signaling allows a UE to access channels in unlicensed frequencies without performing LBT, as long as the following conditions as specified in clause 4.2.7.3.3.3 of [ETSI EN 301 893 V2.1.1] are met:

[0070]

[0071] SL transmissions are organized in frames identified by Direct Frame Numbers (DFNs). DFNs enable UEs to synchronize their radio frame transmissions based on the SL timing reference. UEs perform SL synchronization by synchronizing with the reference to have the same SL timing reference for SL communications between nearby UEs. There are five sources for synchronization reference: GNSS, NR cell (gNB), E-UTRAN cell (eNB), synchronization reference UE, or the UE's own internal clock. Here, a synchronization reference UE is a UE that acts as a synchronization reference source, extending the synchronization coverage of a synchronization source (e.g., GNSS, gNB / eNB, or another synchronization reference UE) or using its own internal clock as a synchronization reference.

[0072] When the UE acts as a synchronization reference UE, it performs transmission of an S-SS / PSBCH block consisting of the S-PSS, S-SSS, and PSBCH signals / channels, and then maps the S-PSS, S-SSS, and PSBCH signals / channels to symbols as described in the following text box [from 3GPP TS 38.211]:

[0073]

[0074] The UE receives the following SL synchronization signals to perform synchronization based on the S-SS / PSBCH block: S-PSS and S-SSS. The UE assumes that the reception timings of PSBCH, S-PSS, and S-SSS are in consecutive symbols and form an S-SS / PSBCH block.

[0075] For reception of S-SS / PSBCH blocks, some exemplary portions of TS 38.213 are shown in the text box below:

[0076]

[0077] In terms of the periodicity of S-SS / PSBCH blocks, some exemplary parts of 3GPP TS 38.213 are shown in the text box below:

[0078]

[0079] sl-NumSSB-WithinPeriod is provided within the SL-SyncConfig IE and can take the following values ​​[TS38.331]:

[0080]

[0081]

[0082] The relationship between the number of SS-SS / PSBCH blocks per period and the start time of the first SS-SS / PSBCH and the time offset between S-SS / PSBCH blocks is shown in Figure 1E is described in .

[0083] Figure 1E An SL-SSB period according to some example embodiments of the present disclosure is illustrated. Figure 1E The relationship between the number of SS-SS / PSBCH blocks, the start time of the first SS-SS / PSBCH (given by sl-TimeOffsetSSB), and the time interval between S-SS / PSBCH blocks (given by sl-TimeInterval) in a period of 16 frames is exemplarily depicted in FIG. This example considers the case of SCS 60 kHz in FR1, which can have a maximum of 4 S-SS / PSBCH blocks in this period.

[0084] As mentioned above, in 3GPP RAN1#111, it was agreed that SL-SSB transmission could use short control signaling (SCSt) (using LBT type 2C in addition to the shared COT), and then whether PSFCH should be allowed to do so as well was listed as FFS, given that the combination of SCSt for SL-SSB and PSFCH can comply with the regulations related to the use of SCSt, as long as the duty cycle and transmission duration are adhered to.

[0085] The obvious challenge is that when SCSt for PSFCH is not allowed, the UE is forced to use a lengthy LBT Type 1 which, under high load, may not even be able to complete its contention window countdown before the mapped PSFCH opportunity. The contention window countdown can be interrupted by another system (e.g. WiFi) (i.e., after a failed LBT check, the countdown process stops and enters a hold-off time, and resumes only after a successful LBT check) or even by another SL transmission that includes one of the PSCCH / PSSCH symbols in the SL slot where the PSFCH symbol occurs (if the COT is not shared with the PSFCH transmitter). However, these problems can be avoided if the UE is allowed to use a short LBT Type 2 (Type 2A, 2B or possibly no Type 2C LBT, i.e., no channel sensing at all) for PSFCH outside the COT.

[0086] Figure 1F An example of an SCSt budget and observation window around an S-SSB transmission is shown in FIG. Figure 1F In

[15] , S-SSB transmissions occur with a periodicity of 160ms, and depending on the subcarrier spacing, there can be more than one S-SSB transmission within this window. With the priority of the SCSt budget for S-SSBs, the UE will need to pre-plan the next SCSt transmissions and the impact of having (one or more) S-SSB transmissions in the 50ms observation window.

[0087] It could certainly be argued that SCSt should only be used for S-SSB transmissions, as this is a limitation in NR-U. However, one argument for considering using SCSt also for PSFCH for SL-U is that, in contrast to NR-U which also supports longer PUCCH formats, the sidelink only supports PSFCH based on short PUCCH format 0.

[0088] Embodiments of the present disclosure provide a mechanism for NR SL-U UEs to be allowed to use SCSt for PSFCH transmissions and to determine when they are allowed to do so within the SCSt usage restrictions so that the SCSt usage for PSFCH in the observation window spans as long as possible, and if priority for occurrence is required (i.e., if there is no budget to use SCSt for all PSFCH transmissions), then intelligently select which PSFCH opportunities SCSt will be used for. Note that here it is considered that when the UE uses SCSt for channel access, Type 2A LBT can be applied, but if LBT is not required for SCSt, the mechanism also applies.

[0089] Figure 2A flow chart of an example method 200 implemented at a terminal device (e.g., terminal device 120) according to some embodiments of the present disclosure is illustrated. In some embodiments, the terminal device 120 may be a synchronization reference UE. For ease of understanding, reference is made to Figure 1A Method 200 is described from the perspective of the terminal device 120 (i.e., NR SL-U UE).

[0090] At block 202, the terminal device 120 receives a configuration for the PSFCH and S-SSB. This may be pre-configured or from a base station. The terminal device 120 may receive a sidelink configuration from the network device 110 or another terminal device. The sidelink configuration may include a configuration for the PSFCH and a configuration for the SL-SSB.

[0091] Additionally, the sidelink configuration may include discontinuous reception (DRX) configuration and / or resource pool (RP) configuration. These two configurations can be found in SL-BWP-Config-r16 and SL-SyncConfigList-r16 in 3GPP TS 38.331, respectively.

[0092] At block 204, the terminal device 120 determines whether the PSFCH can always be transmitted as an SCSt. The terminal device 120 may calculate the PSFCH SCSt budget and time bounds around one or more SL-SSB transmissions. The SL-SSB transmission may be determined based on the SL-SSB configuration. In addition, the terminal device 120 may calculate the PSFCH budget and time bounds without considering the SL-SSB transmission (e.g., see Figure 1F For example, terminal device 120 may determine time boundaries around SL-SSB transmission(s) based on the SL-SSB configuration and the size of the observation period (e.g., 50 ms). The SL-SSB configuration may indicate the location of the SL-SSB transmission(s) within the SL-SSB period, and terminal device 120 may determine time boundaries for each SL-SSB transmission within each period.

[0093] The budget calculation can give the number of PSFCH transmission opportunities using SCSt within these durations within the observation window. For example, with 15kHz subcarrier spacing, 1 S-SSB transmission (13 symbols, since the guard symbols are not considered) and assuming 3 (2+CPe) symbols are used for PSFCH transmission, then:

[0094] ●(35(symbols in 2.5ms)-13(symbols of one S-SSB transmission)) / 3(symbols per PSFCH transmission)=7 PSFCH transmission opportunities using SCSt in this observation window.

[0095] When there is no S-SSB with the same assumption, then:

[0096] · 35 (symbols in 2.5 ms) / 3 (symbols per PSFCH transmission) = 11 PSFCH transmission opportunities using SCSt in the observation window.

[0097] This can be set as a local variable (R SCSt_budget ), the local variable is updated when these time instances or boundaries are reached and when transmission using SCSt occurs. Separate budget variables can be maintained for each LBT band (RB-set) or per carrier (if specified by the SCSt specification).

[0098] In some embodiments, the terminal device 120 may consider the PSFCH configuration to determine whether the PSFCH can always be sent as an SCSt. For example, the PSFCH period may be 4 slots (in Rel-17, but may be longer in later releases), giving a total of 12.5 PSFCH opportunities every 50 ms. So in this example, if the terminal device 120 expects all opportunities to be used, there will not be enough SCSt budget.

[0099] In some embodiments, the terminal device 120 may have several RATs capable of using SCSt, and when the RATs use the same RB set, in addition to the SCSt activity in the SL-U RAT, the terminal device 120 will also consider the SCSt activity of devices using SCSt in these RATs within its available SCSt budget.

[0100] In some embodiments, when terminal device 120 has a DRX configuration, it can account for periods of time in its PSFCH budget during which it will be inactive due to DRX inactivity periods, and therefore unable to receive PSCCH / PSSCH and be triggered to transmit PSFCH. As an extension of the above example, if terminal device 120 is asleep due to DRX and does not listen to X% of PSSCH opportunities, it will not be able to use ~X% of PSFCH opportunities. If this is the case 50%, the opportunities drop to 6.25, which is within the budget of 7, and therefore terminal device 120 can now determine that it can always transmit PSFCH using SCSt.

[0101] When the PSFCH configuration indicates that the terminal device 120 does not have issues complying with SCSt rules or constraints, the terminal device 120 can always use SCSt for PSFCH transmission. For example, this is the case when the PSFCH period is 4 slots, 30kHz SCSt, 1 S-SSB transmission in the observation window, and 2 symbols are used for PSFCH. In this case, the method 200 proceeds to block 206, where the terminal device 120 transmits the PSFCH as SCSt.

[0102] In some embodiments, it may be left to the terminal device 120 to estimate when the PSFCH does not need to be prioritized (e.g. based on traffic statistics or reserved traffic such as semi-persistent transmissions). In some embodiments, when the terminal device 120 has a DRX configuration present, then it may account in its PSFCH SCSt budget for periods of time when it will be inactive due to DRX inactivity periods, and therefore unable to receive PSCCH / PSSCH and be triggered to transmit PSFCH.

[0103] When the configuration does not guarantee that the terminal device 120 can always use SCSt for PSFCH transmission within the observation window, the method 200 proceeds to block 208, where the terminal device 120 determines whether the PSFCH transmission is in the shared COT. If the PSFCH transmission is in the shared COT, then at block 210, the terminal device 120 may initiate a Type-2 LBT (e.g., Type-2A LBT, Type-2B LBT, or Type-2C LBT, depending on the gap between transmissions) for the PSFCH transmission.

[0104] Otherwise, the terminal device 120 may initiate a Type 1 LBT for its PSFCH transmission at block 212. If the Type 1 LBT is successful, the terminal device 120 transmits the PSFCH after the Type 1 LBT is successful at block 214. If the countdown is not completed before the PSFCH transmission, the terminal device 120 will resort to SCSt only if the SCSt budget allows. At block 216, the terminal device 120 determines that the PSFCH budget allows and that PSFCH Verify is true for SCSt to occur for the PSFCH transmission.

[0105] Before starting PSFCH with SCSt (possibly with LBT type 2A), the terminal device 120 can use the maintained SCSt resources to SCSt_usage ≤R SCSt_budget ) is compared with the sliding observation window to verify whether the budget allows the transmission to occur SCSt. When the terminal device 120 sends a PSFCH with SCSt within the sliding observation window, it can add it to the local variable (R SCSt_usage +R SCSt_PSFCHWhen the past PSFCH transmission using SCSt is outside the sliding observation window, the resource (R SCSt_usage -R SCSt_PSFCH ), thereby increasing the available SCSt resources to be used.

[0106] In addition to the validation of the PSFCH SCSt budget, the terminal device 120 may apply a set of mechanisms to prioritize specific PSFCH occasions over other occasions, i.e., extend the budget for a longer period of time, and may therefore decide to drop a PSFCH transmission and save budget for a later PSFCH transmission.

[0107] In some embodiments, when the PSFCH priority is above a threshold, the terminal device 120 may transmit the PSFCH as SCSt. In some embodiments, a set of SCSt probabilities is preconfigured per priority. For example; priority 1: 0.4, priority 2: 0.1, priority 3: 0.05, ..., priority 8: 0.05. Note that these do not necessarily sum to 1, and the threshold per priority may be set by (pre) configuration or by UE implementation. In some embodiments, for example, if the terminal device 120 determines that SCSt usage is always away from restricted usage, the terminal device 120 may periodically evaluate SCSt usage and update the priority.

[0108] If the PSFCH budget allows and the priority rule verifies to be true, the terminal device 120 transmits the PSFCH as SCSt at block 218 ; otherwise, the terminal device 120 drops the PSFCH transmission at block 222 .

[0109] In some embodiments, at block 220, the terminal device 120 may track the use of the PSFCH via the SCSt. Count how many PSFCH opportunities are completed by the terminal device 120 as a Tx UE in the shared COT. For example, if the terminal device 120 knows that on average (or some other probability threshold) the transmission of the PSFCH is in the shared COT, it may determine whether any other rules need to be applied to prioritize the SCSt, and adjust the threshold based on this.

[0110] In some embodiments, the PSFCH used for inter-UE coordination (IUC) feedback can be processed with a lower (or higher) probability than the PSFCH used for hybrid automatic repeat request (HARQ) feedback. For example, the probability can be set to 0, meaning that the PSFCH used for IUC is never considered for SCSt.

[0111] Figure 3 FIG. 3 is a flow chart illustrating another exemplary method 300 implemented at a terminal device according to some embodiments of the present disclosure. Figures 1A to 2Method 300 is described.

[0112] At block 310, the terminal device 120 determines a sidelink configuration comprising at least a sidelink synchronization signal block (SL-SSB) configuration and a physical sidelink feedback channel (PSFCH) configuration. The sidelink configuration may be local or received from the network device 110 or another terminal device.

[0113] In some embodiments, the sidelink configuration may further include a discontinuous reception (DRX) configuration. Additionally, the sidelink configuration may include a resource pool (RP) configuration.

[0114] Based on the SL-SSB configuration and the PSFCH configuration, the terminal device 120 may determine a PSFCH SCSt usage budget within the sliding observation window. The PSFCH SCSt usage budget may conform to one or more constraints of the SCSt. The constraints may define, for example, a total transmission duration with a time period. In some embodiments, the PSFCH SCSt usage budget may indicate the number of PSFCH transmission opportunities using the SCSt within the sliding observation window, taking into account the duration of the PSFCH duration (e.g., 2 or 3 symbols per transmission).

[0115] When the SCSt constraint includes a total duration limit for the SCSt within the sliding observation window, the terminal device 120 may determine the PSFCH SCSt budget as follows. The terminal device 120 may determine the number of SL-SSBs within the sliding observation window based on the SL-SSB configuration. As described above, the SL-SSB configuration may indicate the number of (one or more) SL-SSBs in the S-SSB period, the time offset, and the (one or more) SL-SSB time intervals. Thus, the terminal device may determine how many SL-SSBs are located in the sliding observation window and are transmitted via the SCSt. The terminal device 120 may determine the PSFCH SCSt usage budget based on the duration of the PSFCH transmission, the total duration limit, and the number of SL-SSBs within the sliding observation window.

[0116] In some embodiments, the terminal device 120 may determine whether PSFCH transmissions can always be sent via the SCSt based on the sidelink configuration. The terminal device 120 may determine whether a condition is met based on the PSFCH SCSt usage budget and at least the PSFCH configuration. If the condition is met, the PSFCH is directly allowed to be sent via the SCSt. Additionally or alternatively, the terminal device 120 may send the PSFCH via the SCSt based on the determined PSFCH SCSt budget.

[0117] In some embodiments, the terminal device 120 may determine whether the condition is met further based on a discontinuous reception (DRX) configuration.

[0118] In some embodiments, if the condition is not met, the terminal device 120 may determine whether the transmission of the PSFCH is within the shared channel occupancy time (COT). If the transmission of the PSFCH is within the shared COT, the terminal device 120 may perform a Type 2 LBT procedure and transmit the PSFCH after successfully completing the Type 2 LBT procedure.

[0119] If the transmission of the PSFCH is not within the shared COT, the terminal device 120 may perform a Type 1 LBT procedure for transmitting the PSFCH. The terminal device 120 may transmit the PSFCH after successfully completing the Type 1 LBT procedure. However, if the Type 1 LBT procedure is unsuccessful, the terminal device 120 may resort to transmitting the PSFCH via the SCSt if conditions related to the PSFCH SCSt usage budget are met.

[0120] The terminal device 120 may evaluate conditions before transmitting the PSFCH via the SCSt. The terminal device 120 may determine PSFCH usage within a sliding observation window and verify whether the PSFCH usage is equal to or less than the PSFCH SCSt usage budget. If the PSFCH usage is equal to or less than the PSFCH SCSt usage budget, the terminal device may determine that the conditions are met and may transmit the PSFCH via the SCSt.

[0121] Both PSFCH usage and PSFCH SCSt usage budget can be dynamically updated or adjusted. In some embodiments, terminal device 120 can increase PSFCH usage after PSFCH within the sliding observation window is transmitted via SCSt. Additionally or alternatively, terminal device 120 can reduce PSFCH usage when past PSFCH transmissions via SCSt fall outside the sliding observation window.

[0122] In some embodiments, if the terminal device 120 determines that the priority of the PSSCH feedback mapped to the PSFCH opportunity is higher than the priority threshold, it can send the PFSCH via the SCSt. In some embodiments, the terminal device 120 can generate a random number for the PFSCH based on the priority and compare the random number with the threshold number for the priority. The terminal device 120 can also send the PFSCH via the SCSt based on the comparison.

[0123] In some embodiments, the terminal device 120 may evaluate SCSt usage for PSFCH transmissions and update the priority threshold and the threshold number per priority based on the PSFCH SCSt usage.

[0124] As described above, the PSFCH SCSt usage budget may be adjusted when (one or more) time limits regarding (one or more) SL-SSB transmissions are reached. In some embodiments, the terminal device 120 may determine at least one time limit around (one or more) SL-SSBs based on the SL-SSB configuration and the size of the sliding window (i.e., as in the SCSt constraint). When the terminal device enters at least one time limit around one or more SL-SSBs, the terminal device 120 may update the PSFCH SCSt usage budget. Additionally or alternatively, when the terminal device leaves at least one time limit around one or more SL-SSBs, the terminal device 120 may update the PSFCH SCSt usage budget.

[0125] In some embodiments, the PSFCH SCSt usage budget can be determined for each LBT band or per carrier. In some embodiments, the PSFCH SCSt usage budget can be adjusted based on at least one SCSt usage in one or more radio access technologies (RATs) other than the sidelink unlicensed (SL-U) RAT.

[0126] In view of the above, it can be seen that the embodiments of the present disclosure can enable efficient PFSCH transmission without shared channel occupancy for combined transmission of both SL-SSB and PSFCH. The embodiments of the present disclosure can maximize the opportunity to transmit PSFCH when expected so that its transmission is not blocked due to, for example, unsuccessful LBT type 1.

[0127] In some example embodiments, an apparatus capable of executing method 200 or method 300 (e.g., terminal device 120) may include a component for executing the corresponding steps of method 200 or method 300. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit system or a software module.

[0128] In some example embodiments, the apparatus includes: a component for determining a side link configuration at a terminal device, the side link configuration including at least a side link synchronization signal block (SL-SSB) configuration and a physical side link feedback channel (PSFCH) configuration; and a component for sending the PSFCH based on the side link configuration, via short control signaling transmission (SCSt) or after a listen-before-talk (LBT) procedure is successful.

[0129] In some example embodiments, the sidelink configuration may further include one or more of: a discontinuous reception (DRX) configuration; or a resource pool (RP) configuration.

[0130] In some example embodiments, the apparatus may further include means for determining a PSFCH SCSt usage budget within the sliding observation window based on the SL-SSB configuration and the PSFCH configuration, wherein the PSFCH SCSt usage budget complies with the SCSt usage constraint.

[0131] In some example embodiments, the SCSt constraint may include a total duration limit for the SCSt within a sliding observation window, and the component for determining the PSFCH SCSt usage budget may include: a component for determining the number of SL-SSBs within the sliding observation window based on the SL-SSB configuration; and a component for determining the PSFCH SCSt usage budget based on the duration of the PSFCH transmission, the total duration limit, and the number of SL-SSBs within the sliding observation window.

[0132] In some embodiments, the PSFCH SCSt usage budget may indicate the number of PSFCH transmission opportunities using SCSt within a sliding observation window.

[0133] In some embodiments, the component for sending PSFCH may include: a component for determining whether a condition is met based on the PSFCH SCSt usage budget and at least the PSFCH configuration, wherein if the condition is met, the PSFCH is directly sent via the SCSt; or a component for sending PSFCH via the SCSt based on the PSFCH SCSt usage budget.

[0134] In some embodiments, whether the condition is met may also be determined based on a discontinuous reception (DRX) configuration of the terminal device.

[0135] In some embodiments, the component for sending the PSFCH may include: a component for determining whether the transmission of the PSFCH is within the shared channel occupancy time (COT) based on determining that the condition is not met; and a component for sending the PSFCH after the Type 2 LBT process is successful based on determining that the transmission of the PSFCH is within the shared COT.

[0136] In some embodiments, the apparatus may further include means for performing a Type 1 LBT procedure for transmitting the PSFCH based on determining that the transmission of the PSFCH is not within the shared COT.

[0137] In some embodiments, the means for transmitting the PSFCH may include means for transmitting the PSFCH via the SCSt if the PSFCH SCSt usage budget satisfies a condition after the Type 1 LBT procedure is unsuccessful.

[0138] In some embodiments, the apparatus may further include means for evaluating the condition, which may include means for determining PSFCH usage within a sliding observation window; and means for verifying whether PSFCH usage is equal to or less than a PSFCHCSSt usage budget.

[0139] In some embodiments, the apparatus may further include at least one of: a component for updating PSFCH usage based on sending PSFCH via SCSt within the sliding observation window; or a component for updating PSFCH usage based on determining that past PSFCH transmissions via SCSt were outside the sliding observation window.

[0140] In some embodiments, the apparatus may further include means for transmitting the PFSCH via the SCSt based on determining that the priority of the PSSCH feedback mapped to the PSFCH opportunity is higher than a priority threshold.

[0141] In some embodiments, the apparatus may further include: means for generating a random number for the PFSCH based on the priority; and means for transmitting the PFSCH via the SCSt based on a comparison of the random number with a threshold number for the priority.

[0142] In some embodiments, the apparatus may further include: means for evaluating SCSt usage for PSFCH transmission; and means for updating the priority threshold and the number of threshold updates per priority based on the PSFCH SCSt usage.

[0143] In some embodiments, the apparatus may further include: a component for determining at least one time limit around one or more SL-SSBs based on the SL-SSB configuration and the size of the sliding observation window; a component for updating the PSFCH SCSt usage budget when the terminal device enters at least one time limit around one or more SL-SSBs; and a component for updating the PSFCH SCSt usage budget when the terminal device leaves at least one time limit around one or more SL-SSBs.

[0144] In some embodiments, the PSFCH SCSt usage budget can be determined for each LBT band or per carrier.

[0145] In some embodiments, the PSFCH SCSt usage budget may be adjusted based on at least one SCSt usage in one or more radio access technologies (RATs) other than a sidelink unlicensed (SL-U) RAT.

[0146] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 200 or method 300. In some embodiments, the means comprises at least one processor and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, enable execution of the apparatus.

[0147] Figure 4 4 shows a simplified block diagram of a device 400 suitable for implementing some example embodiments of the present disclosure. The device 400 may be provided to implement a communication device or network element, such as Figure 1A As shown in FIG, the network device 110 and the terminal device 120 are shown in FIG. As shown in the figure, the device 400 includes one or more processors 410, one or more memories 420 coupled to the processors 410, and one or more communication modules 440 coupled to the processors 410.

[0148] The communication module 440 is used for two-way communication. The communication module 440 has at least one antenna to facilitate communication. The communication interface can represent any interface required to communicate with other network elements.

[0149] Processor 410 may be of any type suitable for the local technology network and, as non-limiting examples, may include one or more of the following: a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 400 may have multiple processors, such as application specific integrated circuit chips that are time-slave to a clock synchronized with a main processor.

[0150] Memory 420 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 424, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact disks (CDs), digital video disks (DVDs), and other magnetic and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 422 and other volatile memories that do not persist during power outages.

[0151] Computer program 430 includes computer-executable instructions that are executable by associated processor 410. Program 430 may be stored in ROM 424. Processor 410 may perform any suitable actions and processes by loading program 430 into RAM 422.

[0152] The embodiment of the present disclosure can be implemented by the program 430 so that the device 400 can execute the reference Figures 1A to 3 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0153] In some example embodiments, program 430 may be tangibly embodied in a computer-readable medium that may be included in device 400 (such as in memory 420) or in other storage devices accessible to device 400. Device 400 may load program 430 from the computer-readable medium into RAM 422 for execution. Computer-readable media may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, and the like.

[0154] Figure 5 A block diagram illustrating an example of a computer readable medium 500 according to some example embodiments of the present disclosure is shown. The computer readable medium 500 has a program 430 stored thereon. Note that although Figure 5 Computer-readable medium 500 is described in the context of a CD or DVD, but computer-readable medium 500 may be in any other form suitable for carrying or storing program 430 .

[0155] In general, various embodiments of the present disclosure may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are illustrated and described as block diagrams, flow charts, or using some other graphical representations, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or a controller or other computing device, or some combination thereof.

[0156] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer executable instructions, such as instructions included in a program module, which are executed in a device on a target real or virtual processor to perform the above-referenced Figures 2 to 3 Any of the methods 200 and 300 described herein. Generally speaking, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functionality of program modules can be combined or split between program modules as needed. The machine-executable instructions of program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in both local and remote storage media.

[0157] The program code for executing the disclosed method can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device so that the program code, when executed by the processor or controller, enables the function / operation specified in the flow chart and / or block diagram to be realized. The program code can be executed entirely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0158] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations as described above. Examples of carriers include signals, computer-readable media, etc.

[0159] Computer readable media can be computer readable signal media or computer readable storage media. Computer readable media can include but are not limited to electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or equipment, or any suitable combination of the foregoing. More specific examples of computer readable storage media will include electrical connections with one or more wires, portable computer disks, hard disks, random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROM or flash memory), optical fibers, portable compact disc read-only memories (CD-ROMs), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing. The term "non-transient" as used herein is a restriction on the medium itself (i.e., tangible, rather than signal), rather than a restriction on data storage persistence (e.g., RAM vs. ROM).

[0160] In addition, although operation is described in a particular order, this should not be understood as requiring to perform such operation or to perform all shown operations to realize desired result in the particular order shown or in sequential order. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details have been included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure, but are specific to the description of the features of a particular embodiment. Some features described in the context of a separate embodiment also can be combined in a single embodiment. On the contrary, the various features described in the context of a single embodiment also can be realized individually or with any suitable subcombination in multiple embodiments.

[0161] Although the disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A terminal device, comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the terminal device to at least: determining a sidelink configuration, the sidelink configuration comprising at least a sidelink synchronization signal block (SL-SSB) configuration and a physical sidelink feedback channel (PSFCH) configuration; and Based on the sidelink configuration, the PSFCH is sent via short control signaling transmission (SCSt) or after a successful listen-before-talk (LBT) procedure.

2. The terminal device according to claim 1, wherein the side link configuration further comprises one or more of the following: Discontinuous Reception (DRX) configuration; or Resource Pool (RP) configuration.

3. The terminal device according to claim 1 or 2, wherein the terminal device is further configured to: Based on the SL-SSB configuration and the PSFCH configuration, a PSFCH SCSt usage budget within a sliding observation window is determined, wherein the PSFCH SCSt usage budget complies with SCSt usage constraints.

4. The terminal device of claim 3 , wherein the SCSt constraint comprises a total duration limit for SCSt within the sliding observation window, and the terminal device is further caused to determine the PSF CHSCSSt usage budget by at least: determining the number of SL-SSBs within the sliding observation window based on the SL-SSB configuration; and The PSFCH SCSt usage budget is determined based on the duration of the PSFCH transmission, the total duration limit, and the number of the SL-SSBs within the sliding observation window.

5. A terminal device according to claim 3 or 4, wherein the PSFCH SCSt usage budget indicates the number of PSFCH transmission opportunities using SCSt within the sliding observation window.

6. The terminal device according to any one of claims 3 to 5, wherein the terminal device is caused to transmit the PSFCH by: determining whether a condition is satisfied based on the PSFCH SCSt usage budget and at least the PSFCH configuration, wherein if the condition is satisfied, the PSFCH is directly transmitted via the SCSt; or The PSFCH is sent via the SCSt based on the PSFCH SCSt usage budget.

7. The terminal device of claim 6, wherein whether the condition is met is further determined based on a discontinuous reception (DRX) configuration of the terminal device.

8. The terminal device according to claim 6 or 7, wherein the terminal device is caused to transmit the PSFCH by: Based on determining that the condition is not satisfied, determining whether the transmission of the PSFCH is within a shared channel occupancy time (COT); and Based on determining that the transmission of the PSFCH is within the shared COT, the PSFCH is sent after a Type 2 LBT procedure is successful.

9. The terminal device according to claim 8, wherein the terminal device is further configured to: Based on determining that the transmission of the PSFCH is not within the shared COT, a Type 1 LBT procedure for sending the PSFCH is performed.

10. The terminal device of claim 9, wherein the terminal device is caused to transmit the PSFCH by: After the Type 1 LBT process is unsuccessful, if the PSFCH SCSt usage budget meets the conditions, the PSFCH is sent via SCSt.

11. The terminal device according to claim 10, wherein the terminal device is further caused to evaluate the condition by: determining PSFCH usage within the sliding observation window; and Verify whether the PSFCH usage is equal to or less than the PSFCH SCSt usage budget.

12. The terminal device according to claim 11, wherein the terminal device is further configured to perform at least one of the following: updating the PSFCH usage based on transmitting the PSFCH via the SCSt within the sliding observation window; or The PSFCH usage is updated based on determining that past PSFCH transmissions via SCSt are outside the sliding observation window.

13. The terminal device according to any one of claims 10 to 12, wherein the terminal device is further configured to: Based on determining that the priority of the PSSCH feedback mapped to the PSFCH opportunity is higher than the priority threshold, the PFSCH is transmitted via the SCSt.

14. The terminal device according to claim 13, wherein the terminal device is further configured to: generating a random number for the PFSCH based on the priority; and Based on a comparison of the random number and a threshold number for the priority, the PFSCH is sent via the SCSt.

15. The terminal device according to claim 13 or 14, wherein the terminal device is further configured to: Evaluate the use of SCSt for PSFCH transmission; and Based on the PSFCH SCSt usage, the priority threshold is updated and the threshold number is updated per priority.

16. The terminal device according to any one of claims 3 to 15, wherein the terminal device is further configured to: determining at least one time limit around one or more SL-SSBs based on the SL-SSB configuration and the size of the sliding observation window; When the terminal device enters the at least one time boundary around the one or more SL-SSBs, updating the PSFCH SCSt usage budget; as well as The PSFCH SCSt usage budget is updated when the terminal device leaves at least one time boundary around the one or more SL-SSBs.

17. The terminal device according to any one of claims 3 to 16, wherein the PSFCH SCSt usage budget is determined for each LBT band or per carrier.

18. The terminal device according to any one of claims 3-17, wherein the PSFCH SCSt usage budget is adjusted based on at least one SCSt usage in one or more radio access technologies (RATs) other than a sidelink unlicensed (SL-U) RAT.

19. A method comprising: At a terminal device, determining a sidelink configuration, the sidelink configuration comprising at least a sidelink synchronization signal block (SL-SSB) configuration and a physical sidelink feedback channel (PSFCH) configuration; and Based on the sidelink configuration, the PSFCH is sent via short control signaling transmission (SCSt) or after a successful listen-before-talk (LBT) procedure.

20. An apparatus comprising: means for determining, at a terminal device, a sidelink configuration, the sidelink configuration comprising at least a sidelink synchronization signal block (SL-SSB) configuration and a physical sidelink feedback channel (PSFCH) configuration; and Means for transmitting the PSFCH via short control signaling transmission (SCSt) or after a successful listen-before-talk (LBT) procedure based on the sidelink configuration.

21. A non-transitory computer-readable medium comprising program instructions stored thereon for executing the method according to claim 19.

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