Configurable transmission timeline for physical sidelink feedback channel

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may transmit, to a second user equipment, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel. The UE may receive, from the second user equipment, an indication of an agreement to use the time buffer threshold. The UE may transmit, to the second user equipment and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication received from the second user equipment, the sidelink hybrid automatic repeat request feedback being transmitted on the physical sidelink feedback channel based at least in part on the time buffer threshold. Numerous other aspects are provided.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for a configurable transmission timeline for a physical sidelink feedback control channel.

BACKGROUND

SUMMARY

In some aspects, a method of wireless communication, performed by a first user equipment, may include transmitting, to a second user equipment, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; receiving, from the second user equipment, an indication of an agreement to use the time buffer threshold; and transmitting, to the second user equipment and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication received from the second user equipment, the sidelink hybrid automatic repeat request feedback being transmitted on the physical sidelink feedback channel based at least in part on the time buffer threshold.

In some aspects, a method of wireless communication, performed by a first user equipment, may include receiving, from a second user equipment, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; transmitting, to the second user equipment, an indication of an agreement to use the time buffer threshold; and receiving, from the second user equipment and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication transmitted to the second user equipment, the sidelink hybrid automatic repeat request feedback being received on the physical sidelink feedback channel based at least in part on the time buffer threshold.

In some aspects, a method of wireless communication, performed by a first user equipment, may include identifying a time buffer threshold, from a plurality of candidate time buffer thresholds, associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; and transmitting an indication of the time buffer threshold to one or more other user equipment, the indication of the time buffer threshold being included in sidelink control information.

In some aspects, a first user equipment for wireless communication may include memory and one or more processors coupled to the memory. The memory and the one or more processors may be configured to transmit, to a second user equipment, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; receive, from the second user equipment, an indication of an agreement to use the time buffer threshold; and transmit, to the second user equipment and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication received from the second user equipment, the sidelink hybrid automatic repeat request feedback being transmitted on the physical sidelink feedback channel based at least in part on the time buffer threshold.

In some aspects, a first user equipment for wireless communication may include memory and one or more processors coupled to the memory. The memory and the one or more processors may be configured to receive, from a second user equipment, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; transmit, to the second user equipment, an indication of an agreement to use the time buffer threshold; and receive, from the second user equipment and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication transmitted to the second user equipment, the sidelink hybrid automatic repeat request feedback being received on the physical sidelink feedback channel based at least in part on the time buffer threshold.

In some aspects, a first user equipment for wireless communication may include memory and one or more processors coupled to the memory. The memory and the one or more processors may be configured to identify a time buffer threshold, from a plurality of candidate time buffer thresholds, associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; and transmit an indication of the time buffer threshold to one or more other user equipment, the indication of the time buffer threshold being included in sidelink control information.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a first user equipment, may cause the one or more processors to transmit, to a second user equipment, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; receive, from the second user equipment, an indication of an agreement to use the time buffer threshold; and transmit, to the second user equipment and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication received from the second user equipment, the sidelink hybrid automatic repeat request feedback being transmitted on the physical sidelink feedback channel based at least in part on the time buffer threshold.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a first user equipment, may cause the one or more processors to receive, from a second user equipment, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; transmit, to the second user equipment, an indication of an agreement to use the time buffer threshold; and receive, from the second user equipment and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication transmitted to the second user equipment, the sidelink hybrid automatic repeat request feedback being received on the physical sidelink feedback channel based at least in part on the time buffer threshold.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a first user equipment, may cause the one or more processors to identify a time buffer threshold, from a plurality of candidate time buffer thresholds, associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; and transmit an indication of the time buffer threshold to one or more other user equipment, the indication of the time buffer threshold being included in sidelink control information.

In some aspects, a first apparatus for wireless communication may include means for transmitting, to a second apparatus, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; means for receiving, from the second apparatus, an indication of an agreement to use the time buffer threshold; and means for transmitting, to the second apparatus and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication received from the second apparatus, the sidelink hybrid automatic repeat request feedback being transmitted on the physical sidelink feedback channel based at least in part on the time buffer threshold.

In some aspects, a first apparatus for wireless communication may include means for receiving, from a second apparatus, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; means for transmitting, to the second apparatus, an indication of an agreement to use the time buffer threshold; and means for receiving, from the second apparatus and based at least in part on the indication of the agreement, sidelink hybrid automatic repeat request feedback for a sidelink communication transmitted to the second apparatus, the sidelink hybrid automatic repeat request feedback being received on the physical sidelink feedback channel based at least in part on the time buffer threshold.

In some aspects, a first apparatus for wireless communication may include means for identifying a time buffer threshold, from a plurality of candidate time buffer thresholds, associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; and means for transmitting an indication of the time buffer threshold to one or more other apparatus, the indication of the time buffer threshold being included in sidelink control information.

DETAILED DESCRIPTION

Controller/processor240of base station110, controller/processor280of UE120, and/or any other component(s) ofFIG.2may perform one or more techniques associated with a configurable transmission timeline for a physical sidelink feedback control channel (PSFCH), as described in more detail elsewhere herein. For example, controller/processor240of base station110, controller/processor280of UE120, and/or any other component(s) ofFIG.2may perform or direct operations of, for example, process700ofFIG.7, process800ofFIG.8, process900ofFIG.9, and/or other processes as described herein. Memories242and282may store data and program codes for base station110and UE120, respectively. In some aspects, memory242and/or memory282may comprise a non-transitory computer-readable medium storing one or more instructions for wireless communication. For example, the one or more instructions, when executed by one or more processors of the base station110and/or the UE120, may perform or direct operations of, for example, process700ofFIG.7, process800ofFIG.8, process900ofFIG.9, and/or other processes as described herein. A scheduler246may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, UE120may include means for transmitting, to a second UE120, an indication of a time buffer threshold associated with providing sidelink hybrid automatic repeat request (HARQ) feedback on a PSFCH, means for receiving, from the second UE120, an indication of an agreement to use the time buffer threshold, means for transmitting, to the second UE120and based at least in part on the indication of the agreement, sidelink HARQ feedback for a sidelink communication received from the second UE120, the sidelink HARQ feedback being transmitted on the PSFCH based at least in part on the time buffer threshold, and/or the like. In some aspects, UE120may include means for receiving, from a second UE120, an indication of a time buffer threshold associated with providing sidelink HARQ feedback on a PSFCH, means for transmitting, to the second UE120, an indication of an agreement to use the time buffer threshold, means for receiving, from the second UE120and based at least in part on the indication of the agreement, sidelink HARQ feedback for a sidelink communication transmitted to the second UE120, the sidelink HARQ feedback being received on the PSFCH based at least in part on the time buffer threshold, and/or the like. In some aspects, UE120may include means for identifying a time buffer threshold, from a plurality of candidate time buffer thresholds, associated with providing sidelink hybrid automatic repeat request feedback on a physical sidelink feedback channel; and transmitting an indication of the time buffer threshold to one or more other user equipments, the indication of the time buffer threshold being included in sidelink control information, and/or the like. In some aspects, such means may include one or more components of UE120described in connection withFIG.2, such as controller/processor280, transmit processor264, TX MIMO processor266, MOD254, antenna252, DEMOD254, MIMO detector256, receive processor258, and/or the like.

FIG.3Ashows an example frame structure300for frequency division duplexing (FDD) in a telecommunications system (e.g., NR). The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames (sometimes referred to as frames). Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be partitioned into a set of Z (Z≥1) subframes (e.g., with indices of 0 through Z−1). Each subframe may have a predetermined duration (e.g., 1 ms) and may include a set of slots (e.g., 2mslots per subframe are shown inFIG.3A, where m is a numerology used for a transmission, such as 0, 1, 2, 3, 4, and/or the like). Each slot may include a set of L symbol periods. For example, each slot may include fourteen symbol periods (e.g., as shown inFIG.3A), seven symbol periods, or another number of symbol periods. In a case where the subframe includes two slots (e.g., when m=1), the subframe may include 2L symbol periods, where the 2L symbol periods in each subframe may be assigned indices of 0 through 2L−1. In some aspects, a scheduling unit for the FDD may be frame-based, subframe-based, slot-based, symbol-based, and/or the like.

In certain telecommunications (e.g., NR), a base station may transmit synchronization signals. For example, a base station may transmit a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and/or the like, on the downlink for each cell supported by the base station. The PSS and SSS may be used by UEs for cell search and acquisition. For example, the PSS may be used by UEs to determine symbol timing, and the SSS may be used by UEs to determine a physical cell identifier, associated with the base station, and frame timing. The base station may also transmit a physical broadcast channel (PBCH). The PBCH may carry some system information, such as system information that supports initial access by UEs.

In some aspects, the base station may transmit the PSS, the SSS, and/or the PBCH in accordance with a synchronization communication hierarchy (e.g., a synchronization signal (SS) hierarchy) including multiple synchronization communications (e.g., SS blocks), as described below in connection withFIG.3B.

FIG.3Bis a block diagram conceptually illustrating an example SS hierarchy, which is an example of a synchronization communication hierarchy. As shown inFIG.3B, the SS hierarchy may include an SS burst set, which may include a plurality of SS bursts (identified as SS burst 0 through SS burst B−1, where B is a maximum number of repetitions of the SS burst that may be transmitted by the base station). As further shown, each SS burst may include one or more SS blocks (identified as SS block 0 through SS block (bmax_SS−1), where bmax_SS−1 is a maximum number of SS blocks that can be carried by an SS burst). In some aspects, different SS blocks may be beam-formed differently. An SS burst set may be periodically transmitted by a wireless node, such as every X milliseconds, as shown inFIG.3B. In some aspects, an SS burst set may have a fixed or dynamic length, shown as Y milliseconds inFIG.3B.

The SS burst set shown inFIG.3Bis an example of a synchronization communication set, and other synchronization communication sets may be used in connection with the techniques described herein. Furthermore, the SS block shown inFIG.3Bis an example of a synchronization communication, and other synchronization communications may be used in connection with the techniques described herein.

In some aspects, an SS block includes resources that carry the PSS, the SSS, the PBCH, and/or other synchronization signals (e.g., a tertiary synchronization signal (TSS)) and/or synchronization channels. In some aspects, multiple SS blocks are included in an SS burst, and the PSS, the SSS, and/or the PBCH may be the same across each SS block of the SS burst. In some aspects, a single SS block may be included in an SS burst. In some aspects, the SS block may be at least four symbol periods in length, where each symbol carries one or more of the PSS (e.g., occupying one symbol), the SSS (e.g., occupying one symbol), and/or the PBCH (e.g., occupying two symbols).

In some aspects, the symbols of an SS block are consecutive, as shown inFIG.3B. In some aspects, the symbols of an SS block are non-consecutive. Similarly, in some aspects, one or more SS blocks of the SS burst may be transmitted in consecutive radio resources (e.g., consecutive symbol periods) during one or more slots. Additionally, or alternatively, one or more SS blocks of the SS burst may be transmitted in non-consecutive radio resources.

In some aspects, the SS bursts may have a burst period, whereby the SS blocks of the SS burst are transmitted by the base station according to the burst period. In other words, the SS blocks may be repeated during each SS burst. In some aspects, the SS burst set may have a burst set periodicity, whereby the SS bursts of the SS burst set are transmitted by the base station according to the fixed burst set periodicity. In other words, the SS bursts may be repeated during each SS burst set.

The base station may transmit system information, such as system information blocks (SIBs) on a physical downlink shared channel (PDSCH) in certain slots. The base station may transmit control information/data on a physical downlink control channel (PDCCH) in C symbol periods of a slot, where B may be configurable for each slot. The base station may transmit traffic data and/or other data on the PDSCH in the remaining symbol periods of each slot.

As indicated above,FIGS.3A and3Bare provided as examples. Other examples may differ from what is described with regard toFIGS.3A and3B.

FIG.4shows an example slot format410with a normal cyclic prefix. The available time frequency resources may be partitioned into resource blocks. Each resource block may cover a set of subcarriers (e.g.,12subcarriers) in one slot and may include a number of resource elements. Each resource element may cover one subcarrier in one symbol period (e.g., in time) and may be used to send one modulation symbol, which may be a real or complex value.

A UE may be located within the coverage of multiple BSs. One of these BSs may be selected to serve the UE. The serving BS may be selected based at least in part on various criteria such as received signal strength, received signal quality, path loss, and/or the like. Received signal quality may be quantified by a signal-to-noise-and-interference ratio (SNIR), or a reference signal received quality (RSRQ), or some other metric. The UE may operate in a dominant interference scenario in which the UE may observe high interference from one or more interfering BSs.

In some aspects, a single component carrier bandwidth of 100 MHz may be supported. NR resource blocks may span 12 sub-carriers with a sub-carrier bandwidth of 60 or 120 kilohertz (kHz) over a 0.1 millisecond (ms) duration. Each radio frame may include 40 slots and may have a length of 10 ms. Consequently, each slot may have a length of 0.25 ms. Each slot may indicate a link direction (e.g., DL or UL) for data transmission and the link direction for each slot may be dynamically switched. Each slot may include DL/UL data as well as DL/UL control data.

In a wireless network, a UE may transmit sidelink communications to one or more other UEs, and/or receive sidelink communications from one or more other UEs. For example, a UE may receive a sidelink communication on a sidelink channel between the UE and another UE (e.g., a physical sidelink shared channel (PSSCH), a physical sidelink control channel (PSCCH), and/or the like), may receive a sidelink communication on a sidelink communication between the UE and another UE, and/or the like.

In some cases, a UE may transmit feedback to another UE based at least in part on a sidelink communication transmitted to the UE. The feedback may include, for example, hybrid automatic repeat request (HARQ) feedback, channel state information (CSI) feedback, and/or the like. Sidelink HARQ feedback may include an indication of whether a sidelink communication was successfully received (e.g., an acknowledgement (ACK)) or not successfully received (e.g., a negative acknowledgment (NACK)).

In some cases, a UE may be configured to transmit sidelink HARQ feedback on a PSFCH based at least in part on a transmission timeline for transmitting sidelink HARQ feedback on the PSFCH. The transmission timeline may be based at least in part on a time buffer relative to a time at which a sidelink communication was transmitted or received (e.g., relative to an ending slot and/or symbol of the sidelink communication). The time buffer may be a quantity of slots, a quantity of symbols, and/or the like between the slot and/or symbol in which the UE received the sidelink communication, and the slot and/or symbol in which the UE may transmit sidelink HARQ feedback for the sidelink communication. For example, if reception of a sidelink communication at a UE ends in slot n, the earliest slot in which the UE may transmit sidelink HARQ feedback for the sidelink communication may be identified as n+a, where a is the time buffer between slot n and a subsequent slot that includes sidelink HARQ feedback resources in which the UE may transmit the sidelink HARQ feedback.

A UE may determine a based at least in part on a K value. The K value may be a time buffer threshold that ensures a time gap, between reception of a sidelink communication and transmission of associated sidelink HARQ feedback, so that a UE may generate the sidelink HARQ feedback during the time gap. Accordingly, a UE may identify a slot that includes sidelink HARQ feedback resources, after a slot n, such that the time buffer (e.g., a) between slot n and the slot that includes sidelink HARQ feedback resources satisfies the time buffer threshold (e.g., the K value).

In some cases, the K value may be configured to be the same for all UEs associated with a particular cell, for all UEs included in a particular group of UEs, for all UEs associated with a particular sidelink receive resource pool, for all UEs in the wireless network, and/or the like. However, a K value that is the same for a plurality of UEs may result in some UEs that might not be capable of supporting the K value, may result in inefficient sidelink HARQ feedback reporting for some UEs, and/or the like. For example, a UE might not be capable of supporting a K value if the K value is set to a low quantity of slots and/or symbols, and if the UE is a low-capability UE (e.g., the processing, software, memory, and/or networking configuration of the UE may not be capable of generating and transmitting sidelink HARQ feedback within a quantity of symbols and/or slots configured for a K value). As another example, a UE might be capable of generating and transmitting sidelink HARQ feedback at faster time intervals than a configured K value if the K value is set to a low quantity of slots and/or symbols if the UE is a high-capability UE.

Some aspects described herein provide techniques and apparatuses for a configurable transmission timeline for PSFCH. In some aspects, a UE may identify and/or select a time buffer threshold (e.g., a K value) from a plurality of candidate time buffer thresholds. In some aspects, the UE may identify and/or select the time buffer threshold based at least in part on a capability of the UE to generate and transmit sidelink HARQ feedback and/or other parameters. In some aspects, if the UE communicates with a plurality of other UEs in a groupcast or multicast configuration, the UE may transmit an indication of the time buffer threshold in sidelink control information (SCI) to the plurality of other UEs. In some aspects, if the UE communicates with another UE in a unicast configuration, the UE may negotiate the time buffer threshold with the other UE by transmitting an indication of the time buffer threshold to the UE, and the other UE may respond with an indication of an agreement to use the time buffer threshold (or may reject the time buffer threshold and propose a different time buffer threshold).

In this way, the UE may transmit sidelink HARQ feedback to one or more other UEs based at least in part on a time buffer threshold specifically configured for the UE. This permits the UE to identify and/or select a time buffer threshold that is compatible with the UE's capability for generating and transmitting sidelink HARQ feedback, permits the UE to identify and/or select a time buffer threshold that increases the efficiency of sidelink HARQ feedback reporting of the UE, and/or the like.

FIGS.5A and5Bare diagrams illustrating one or more examples500of a configurable transmission timeline for PSFCH, in accordance with various aspects of the present disclosure. As shown inFIGS.5A and5B, example(s)500may include communication between a plurality of UEs (e.g., UEs120), such as UE1, UE2, and/or the like. In some aspects, UE1and UE2may be included in a wireless network (e.g., wireless network100). In some aspects, UE1and UE2may communicate on a sidelink between UE1and UE2in a unicast configuration.

In some aspects, UE1may be configured to generate and transmit sidelink HARQ feedback to UE2. For example, UE1may be configured to generate and transmit sidelink HARQ feedback based at least in part on a unicast sidelink communication received from UE2(e.g., on a PSSCH, a PSCCH, and/or other sidelink channels of the sidelink).

As shown inFIG.5A, and by reference number502, UE1may transmit, to UE2, an indication of a time buffer threshold (e.g., a K value) for transmitting sidelink HARQ feedback to UE2on a PSFCH. In some aspects, UE1may identify and/or select the time buffer threshold from a plurality of candidate time buffer thresholds that are permitted to be selected by UE1. In some aspects, a BS (e.g., BS110), UE2, and/or another entity may configure the plurality of candidate time buffer thresholds for UE1.

In some aspects, UE1may select the time buffer threshold based at least in part on a UE capability of UE1. For example, UE1may select the time buffer threshold based at least in part on a processing capability of UE1, a memory capability of UE1, a network or communication capability of UE1(e.g., a throughput associated with UE1, a latency associated with UE1, and/or the like), a capability of UE1to generate and transmit sidelink HARQ feedback, and/or the like. In some aspects, UE1may select the time buffer threshold based at least in part on other parameters, such as channel conditions on the sidelink between UE1and UE2. In this case, UE1may select the time buffer threshold based at least in part on a signal quality on the sidelink, a signal strength on the sidelink, and/or the like.

In some aspects, UE1may transmit the indication of the time buffer threshold to UE2during connection establishment with UE2. In some aspects, UE1may transmit the indication of the time buffer threshold to UE2after connection establishment with UE2. In some aspects, UE1may periodically or non-periodically update the time buffer threshold (e.g., based at least in part on RSRP, RSRQ, RSSI, CQI, and/or other types of measurement parameters). In some aspects, UE1may transmit the indication of the time buffer threshold to UE2in SCI in a PSSCH communication, in SCI in a PSCCH communication, and/or the like.

As further shown inFIG.5A, and as shown by reference number504, UE2may receive the indication of the time buffer threshold, and may transmit an indication of an agreement to use the time buffer threshold. In this way, UE1and UE2may negotiate the time buffer threshold between peer UEs. In some aspects, UE2may reject the time buffer threshold, may transmit an indication of a rejection of the time buffer threshold, and may transmit an indication of another time buffer threshold. In this case, UE1may agree to the use of the other time buffer threshold, or UE1and UE2may continue to negotiate until a time buffer threshold is agreed upon.

As shown inFIG.5B, and by reference number506, UE1may receive a sidelink communication from UE2(e.g., a unicast sidelink communication) and may transmit sidelink HARQ feedback, associated with the sidelink communication, on the PSFCH based at least in part on the agreed upon time buffer threshold. In some aspects, UE1may transmit the sidelink HARQ feedback in a sidelink communication on the PSFCH.

As an example, and as illustrated inFIG.5B, UE1may receive a sidelink communication from UE2in slot n. The sidelink communication may include data, control information, and/or other types of information that may be time division multiplexed and/or frequency division multiplexed in slot n. UE1may identify a subsequent slot that includes sidelink HARQ feedback resources in which UE1may transmit sidelink HARQ feedback to UE2based at least in part on the sidelink communication received in slot n. The subsequent slot may occur at a time buffer a (e.g., n+a) from an ending slot n. In this case, UE1may select the subsequent slot (e.g., slot n+2 in this example) such that the time buffer satisfies the time buffer threshold (e.g., such that a≥K) agreed upon between UE1and UE2(e.g., where the K value may be 2 slots in this example).

In some aspects, UE2may receive the sidelink HARQ feedback from UE1. In some aspects, due to UE1and other UEs being permitted to configure a particular time buffer threshold, the sidelink HARQ feedback from UE1may collide (e.g., may at least partially overlap in the time domain and/or frequency domain) with another sidelink HARQ feedback from another UE. In this case, UE1and the other UE may transmit respective sidelink HARQ feedback using different PSFCH sequences (e.g., UE1may scramble the sidelink communication carrying the sidelink HARQ feedback of UE1, and the other UE may scramble the sidelink communication carrying the sidelink HARQ feedback of the other UE). UE2may detect the collision and may identify the sidelink HARQ feedback of UE1from the sidelink HARQ feedback of the other UE, based at least in part on the respective PSFCH sequences associated with UE1and the other UE. UE1may generate a PSFCH sequence based at least in part on a source identifier and/or another type of UE identifier associated with UE1, and the other UE may generate a PSFCH sequence based at least in part on a source identifier and/or another type of UE identifier associated with the other UE.

In this way, UE1may transmit sidelink HARQ feedback to UE2based at least in part on a time buffer threshold specifically configured for UE1. This permits UE1to identify and/or select a time buffer threshold that is compatible with UE1's capability for generating and transmitting sidelink HARQ feedback, permits UE1to identify and/or select a time buffer threshold that increases the efficiency of sidelink HARQ feedback reporting of UE1, and/or the like.

As indicated above,FIGS.5A and5Bare provided as one or more examples. Other examples may differ from what is described with respect toFIGS.5A and5B. For example, UE2may configure a particular time buffer threshold for providing sidelink HARQ feedback to UE1using one or more techniques described above in connection withFIGS.5A and5B.

FIG.6is a diagram illustrating one or more examples600of a configurable transmission timeline for PSFCH, in accordance with various aspects of the present disclosure. As shown inFIG.6, example(s)600may include communication between a plurality of UEs (e.g., UEs120), such as UE1through UEm and/or the like. In some aspects, UE1through UEm may be included in a wireless network (e.g., wireless network100). In some aspects, UE1through UEm may communicate on one or more sidelinks between UE1through UEm in a groupcast or multicast configuration.

In some aspects, UE1may be configured to generate and transmit sidelink HARQ feedback to one or more of UE2through UEm. For example, UE1may be configured to generate and transmit sidelink HARQ feedback based at least in part on a groupcast or multicast sidelink communication received from UE2(e.g., on a PSSCH, a PSCCH, and/or other sidelink channels of the sidelink) and/or another UE of UE3through UEm.

As shown inFIG.6, and by reference number602, UE1may identify a time buffer threshold (e.g., a K value) associated with providing sidelink HARQ feedback to UE2through UEm on a PSFCH. In some aspects, UE1may identify and/or select the time buffer threshold from a plurality of candidate time buffer thresholds that are permitted to be selected by UE1. In some aspects, a BS (e.g., BS110), one or more of UE2through UEm, and/or another entity may configure the plurality of candidate time buffer thresholds for UE1.

In some aspects, UE1may identify and/or select the time buffer threshold based at least in part on a UE capability of UE1. For example, UE1may select the time buffer threshold based at least in part on a processing capability of UE1, a memory capability of UE1, a network or communication capability of UE1(e.g., a throughput associated with UE1, a latency associated with UE1, and/or the like), a capability of UE1to generate and transmit sidelink HARQ feedback, and/or the like. In some aspects, UE1may select the time buffer threshold based at least in part on other parameters, such as channel conditions on a sidelink between UE1and one or more of UE2through UEm. In this case, UE1may select the time buffer threshold based at least in part on a signal quality on the sidelink, a signal strength on the sidelink, and/or the like.

As shown inFIG.6, and by reference number604, UE1may transmit, to UE2through UEm, an indication of the time buffer threshold. In some aspects, UE1may transmit the indication of the time buffer threshold in a groupcast or multicast sidelink communication to UE2through UEm. In some aspects, the indication of the time buffer threshold may be included in SCI in the groupcast or multicast sidelink communication.

In some aspects, UE1may subsequently receive a sidelink communication (e.g., a groupcast or multicast sidelink communication) from a UE of UE2through UEm (e.g., UE2) and may transmit sidelink HARQ feedback to the UE on the PSFCH based at least in part on the time buffer threshold. In some aspects, UE1may transmit the sidelink HARQ feedback in a sidelink communication on the PSFCH at a time buffer a after receiving the groupcast or multicast sidelink communication. For example, UE1may transmit the sidelink HARQ feedback such that the time buffer satisfies the time buffer threshold (e.g., such that a≥K).

In this way, UE1may transmit sidelink HARQ feedback to one or more of UE2through UEm based at least in part on a time buffer threshold specifically configured for UE1. This permits UE1to identify and/or select a time buffer threshold that is compatible with UE1's capability for generating and transmitting sidelink HARQ feedback, permits UE1to identify and/or select a time buffer threshold that increases the efficiency of sidelink HARQ feedback reporting of UE1, and/or the like.

As indicated above,FIG.6is provided as one or more examples. Other examples may differ from what is described with respect toFIG.6. For example, UE2through UEm may each configure a particular time buffer threshold for providing sidelink HARQ feedback to other UEs in UE1through UEm using one or more techniques described above in connection withFIGS.5A,5B, and/or6.

FIG.7is a diagram illustrating an example process700performed, for example, by a first UE, in accordance with various aspects of the present disclosure. Example process700is an example where the first UE (e.g., UE120) performs operations associated with a configurable transmission timeline for PSSFCH.

As shown inFIG.7, in some aspects, process700may include transmitting, to a second UE, an indication of a time buffer threshold associated with providing sidelink HARQ feedback on a PSFCH (block710). For example, the first UE (e.g., using antenna252, MOD254, transmit processor264, Tx MIMO processor266, controller/processor280, memory282, and/or the like) may transmit, to a second UE, an indication of a time buffer threshold associated with providing sidelink HARQ feedback on a PSFCH, as described above.

As further shown inFIG.7, in some aspects, process700may include receiving, from the second UE, an indication of an agreement to use the time buffer threshold (block720). For example, the first UE (e.g., using antenna252, DEMOD254, MIMO detector256, receive processor258, controller/processor280, memory282, and/or the like) may receive, from the second UE, an indication of an agreement to use the time buffer threshold, as described above.

As further shown inFIG.7, in some aspects, process700may include transmitting, to the second UE and based at least in part on the indication of the agreement, sidelink HARQ feedback for a sidelink communication received from the second UE, the sidelink HARQ feedback being transmitted on the PSFCH based at least in part on the time buffer threshold (block730). For example, the first UE (e.g., using antenna252, MOD254, transmit processor264, Tx MIMO processor266, controller/processor280, memory282, and/or the like) may transmit, to the second UE and based at least in part on the indication of the agreement, sidelink HARQ feedback for a sidelink communication received from the second UE, the sidelink HARQ feedback being transmitted on the PSFCH based at least in part on the time buffer threshold, as described above.

With respect to process700, and in a first aspect, transmitting the sidelink HARQ feedback comprises transmitting the sidelink HARQ feedback at a time buffer after receiving the sidelink communication, the time buffer satisfying the time buffer threshold. With respect to process700, and in a second aspect, alone or in combination with the first aspect, the time buffer threshold is based at least in part on a user equipment capability of the first user equipment to generate and transmit the sidelink HARQ feedback.

With respect to process700, and in a third aspect, alone or in combination with one or more of the first and second aspects, process700includes identifying the time buffer threshold from a plurality of candidate time buffer thresholds. With respect to process700, and in a fourth aspect, alone or in combination with one or more of the first through third aspects, the sidelink communication is a unicast sidelink communication. With respect to process700, and in a fifth aspect, alone or in combination with one or more of the first through fourth aspects, transmitting the indication of the time buffer threshold comprises transmitting the indication of the time buffer threshold during connection establishment between the first UE and the second UE.

FIG.8is a diagram illustrating an example process800performed, for example, by a first UE, in accordance with various aspects of the present disclosure. Example process800is an example where the first UE (e.g., UE120) performs operations associated with a configurable transmission timeline for PSFCH.

As shown inFIG.8, in some aspects, process800may include receiving, from a second UE, an indication of a time buffer threshold associated with providing sidelink HARQ feedback on a PSFCH (block810). For example, the first UE (e.g., using antenna252, DEMOD254, MIMO detector256, receive processor258, controller/processor280, memory282, and/or the like) may receive, from a second UE, an indication of a time buffer threshold associated with providing sidelink HARQ feedback on a PSFCH, as described above.

As further shown inFIG.8, in some aspects, process800may include transmitting, to the second UE, an indication of an agreement to use the time buffer threshold (block820). For example, the first UE (e.g., using antenna252, MOD254, transmit processor264, Tx MIMO processor266, controller/processor280, memory282, and/or the like) may transmit, to the second UE, an indication of an agreement to use the time buffer threshold, as described above.

As further shown inFIG.8, in some aspects, process800may include receiving, from the second UE and based at least in part on the indication of the agreement, sidelink HARQ feedback for a sidelink communication transmitted to the second UE, the sidelink HARQ feedback being received on the PSFCH based at least in part on the time buffer threshold (block830). For example, the first UE (e.g., using antenna252, DEMOD254, MIMO detector256, receive processor258, controller/processor280, memory282, and/or the like) may receive, from the second UE and based at least in part on the indication of the agreement, sidelink HARQ feedback for a sidelink communication transmitted to the second UE, the sidelink HARQ feedback being received on the PSFCH based at least in part on the time buffer threshold, as described above.

With respect to process800, and in a first aspect, receiving the sidelink HARQ feedback comprises receiving the sidelink HARQ feedback at a time buffer after receiving the sidelink communication, the time buffer satisfying the time buffer threshold. With respect to process800, and in a second aspect, alone or in combination with the first aspect, the time buffer threshold is based at least in part on a user equipment capability of the first user equipment to generate and transmit the sidelink hybrid automatic repeat request feedback. With respect to process800, and in a third aspect, alone or in combination with one or more of the first and second aspects, the time buffer threshold is included in a plurality of candidate time buffer thresholds.

With respect to process800, and in a fourth aspect, alone or in combination with one or more of the first through third aspects, the sidelink communication is a unicast sidelink communication. With respect to process800, and in a fifth aspect, alone or in combination with one or more of the first through fourth aspects, receiving the indication of the time buffer threshold comprises receiving the indication of the time buffer threshold during connection establishment between the first UE and the second UE.

With respect to process800, and in a sixth aspect, alone or in combination with one or more of the first through fifth aspects, process800includes detecting a collision between the sidelink HARQ feedback received from the second UE and sidelink HARQ feedback received from a third UE, and identifying the sidelink HARQ feedback received from the second UE from the sidelink HARQ feedback received from a third UE based at least in part on a PSFCH sequence associated with the second UE, the PSFCH sequence being based at least in part on a source identifier associated with the second UE.

FIG.9is a diagram illustrating an example process900performed, for example, by a first UE, in accordance with various aspects of the present disclosure. Example process900is an example where the first UE (e.g., UE120) performs operations associated with a configurable transmission timeline for PSFCH.

As shown inFIG.9, in some aspects, process900may include identifying a time buffer threshold, from a plurality of candidate time buffer thresholds, associated with providing sidelink HARQ feedback on a PSFCH (block910). For example, the first UE (e.g., using receive processor258, transmit processor264, controller/processor280, memory282, and/or the like) may identify a time buffer threshold, from a plurality of candidate time buffer thresholds, associated with providing sidelink HARQ feedback on a PSFCH, as described above.

As further shown inFIG.9, in some aspects, process900may include transmitting an indication of the time buffer threshold to one or more other UEs, the indication of the time buffer threshold being included in SCI (block920). For example, the first UE (e.g., using antenna252, MOD254, transmit processor264, Tx MIMO processor266, controller/processor280, memory282, and/or the like) may transmit an indication of the time buffer threshold to one or more other UEs, the indication of the time buffer threshold being included in SCI, as described above.

With respect to process900, and in a first aspect, the time buffer threshold is based at least in part on a UE capability of the first UE to generate and transmit sidelink hybrid automatic repeat request feedback. With respect to process900, and in a second aspect, alone or in combination with the first aspect, process900includes receiving, from a second UE of the one or more other UEs, a groupcast sidelink communication and transmitting, to the second UE, sidelink HARQ feedback for the groupcast sidelink communication, the sidelink hybrid automatic repeat request feedback being transmitted on the PSFCH based at least in part on the time buffer threshold.

With respect to process900, and in a third aspect, alone or in combination with one or more of the first and second aspects, transmitting the sidelink HARQ feedback comprises transmitting the sidelink HARQ feedback at a time buffer after receiving the groupcast sidelink communication, the time buffer satisfying the time buffer threshold.