SIDELINK FEEDBACK CHANNEL RESOURCES HAVING A PLURALITY OF SYMBOLS

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a first user equipment (UE) may receive, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a physical sidelink feedback channel (PSFCH) resource comprising more than two symbols. The first UE may receive, from the second UE, a sidelink transmission. The first UE may transmit, to the second UE and based at least in part on the sidelink transmission, a hybrid automatic repeat request (HARQ) acknowledgement (ACK) feedback based at least in part on the PSFCH resource comprising more than two symbols. Numerous other aspects are described.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for sidelink feedback channel resources having a plurality of symbols.

BACKGROUND

SUMMARY

In some implementations, an apparatus for wireless communication at a first user equipment (UE) includes a memory and one or more processors, coupled to the memory, the memory storing code executable by the one or more processors to cause the first UE to: receive, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a physical sidelink feedback channel (PSFCH) resource comprising more than two symbols; receive, from the second UE, a sidelink transmission; and transmit, to the second UE and based at least in part on the sidelink transmission, a hybrid automatic repeat request (HARQ) acknowledgement (ACK) feedback based at least in part on the PSFCH resource comprising more than two symbols.

In some implementations, an apparatus for wireless communication at a second UE includes a memory and one or more processors, coupled to the memory, the memory storing code executable by the one or more processors to cause the second UE to: transmit, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; transmit, to the first UE, a sidelink transmission; and receive, from the first UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

In some implementations, a method of wireless communication performed by a first UE includes receiving, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; receiving, from the second UE, a sidelink transmission; and transmitting, to the second UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

In some implementations, a method of wireless communication performed by a second UE includes transmitting, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; transmitting, to the first UE, a sidelink transmission; and receiving, from the first UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

In some implementations, a non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions, when executed by one or more processors of a first UE, cause the first UE to: receive, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; receive, from the second UE, a sidelink transmission; and transmit, to the second UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

In some implementations, a non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions, when executed by one or more processors of a second UE, cause the second UE to: transmit, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; transmit, to the first UE, a sidelink transmission; and receive, from the first UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

In some implementations, a first apparatus for wireless communication includes means for receiving, from a second apparatus or a network node, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; means for receiving, from a second apparatus, a sidelink transmission; and means for transmitting, to the second apparatus and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

In some implementations, a second apparatus for wireless communication includes means for transmitting, to a first apparatus, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; means for transmitting, to the first apparatus, a sidelink transmission; and means for receiving, from the first apparatus and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

DETAILED DESCRIPTION

In some aspects, a first UE (e.g., UE120a) may include a communication manager140. As described in more detail elsewhere herein, the communication manager140may receive, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a physical sidelink feedback channel (PSFCH) resource comprising more than two symbols; receive, from the second UE, a sidelink transmission; and transmit, to the second UE and based at least in part on the sidelink transmission, a hybrid automatic repeat request (HARQ) acknowledgement (ACK) feedback based at least in part on the PSFCH resource comprising more than two symbols. Additionally, or alternatively, the communication manager140may perform one or more other operations described herein.

In some aspects, a second UE (e.g., UE120e) may include a communication manager150. As described in more detail elsewhere herein, the communication manager150may transmit, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; transmit, to the first UE, a sidelink transmission; and receive, from the first UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols. Additionally, or alternatively, the communication manager150may perform one or more other operations described herein.

In some aspects, a first UE (e.g., UE120a) includes means for receiving, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; means for receiving, from the second UE, a sidelink transmission; and/or means for transmitting, to the second UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols. The means for the first UE to perform operations described herein may include, for example, one or more of communication manager140, antenna252, modem254, MIMO detector256, receive processor258, transmit processor264, TX MIMO processor266, controller/processor280, or memory282.

In some aspects, a second UE (e.g., UE120e) includes means for transmitting, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols; means for transmitting, to the first UE, a sidelink transmission; and/or means for receiving, from the first UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols. The means for the second UE to perform operations described herein may include, for example, one or more of communication manager140, antenna252, modem254, MIMO detector256, receive processor258, transmit processor264, TX MIMO processor266, controller/processor280, or memory282.

FIG.4is a diagram illustrating an example400of a PSFCH resource mapping, in accordance with the present disclosure.

As shown inFIG.4, a physical sidelink shared channel (PSSCH) may be associated with a slot i and a subchannel j. A mapping between the PSSCH and a corresponding PSFCH resource may be based at least in part on a starting subchannel of the PSSCH or a quantity of subchannels in the PSSCH, a slot containing the PSSCH, a source identifier, and a destination identifier. A sidelink PSFCH candidate resource type (sl-PSFCH-CandidateResourceType) may be configured as a starting subchannel (startSubCH) or as an allocated subchannel (allocSubCH). A quantity of available PSFCH resources must be equal to or greater than a quantity of UEs in groupcast option2.

FIG.5is a diagram illustrating an example500of determining a PSFCH resource, in accordance with the present disclosure.

A period PSFCH resource (periodPSFCHresource) parameter may indicate a PSFCH periodicity, in number of slots, in a sidelink resource pool. The period PSFCH resource parameter may be set to 0, 1, 2, or 4. When the period PSFCH resource parameter is set to 0, PSFCH transmissions from a UE in the sidelink resource pool may be disabled. The UE may transmit the PSFCH in a first slot that includes PSFCH resources and is at least a quantity of slots, as provided by a minimum time gap of a PSFCH (MinTimeGapPSFCH) parameter, of the sidelink resource pool after a last slot of a PSSCH reception. A resource block set PSFCH (rbSetPSFCH) parameter may indicate a set of MPRB,setPSFCHset physical resource blocks (PRBs) in the sidelink resource pool for PSFCH transmission. A quantity of subchannels (numSubchannel) parameter may indicate a quantity of Nsubchsub-channels for the sidelink resource pool. A quantity of PSSCH slots associated with a PSFCH slot may be represented by NPSSCHPSFCH, and may be determined based at least in part on the periodPSFCHresource parameter. Further, MPRB,setPSFCH=α·Nsubch·NPSSCH, where a represents an integer value and “·” represents a PSFCH multiplication operation. Further,

represents a quantity of PSFCH PRBs for a sub-channel.

The UE may allocate [(i+j·NPSSCHPSFCH). Msubch,slotPSFCH, (i+1+j·NPSSCHPSFCH). Msubch,slotPSFCH−1] PRBs from MPRB,setPSFCHPRBs to slot i and sub-channel j, where 0≤i≤NPSSCHPSFCHand 0≤j≤Nsubch.

In the example shown inFIG.5, NPSSCHPSFCHmay be equal to four, which may correspond to a PSFCH periodicity. Further, Nsubchmay be equal to ten, which may correspond to a quantity of subchannels for the sidelink resource pool. Further, Msubch,slotPSFCHmay correspond to

which is equal to two. In other words, each sub-channel may be associated with two PSFCH PRBs, which may correspond to 80 PRBs for the PSFCH. In this example, each sub-channel may be associated with two PSFCH PRBs, but the PSFCH may be sent on one of the PSFCH PRBs.

FIG.6is a diagram illustrating an example600of a mini-slot scheduling, in accordance with the present disclosure.

As shown inFIG.6, a mini-slot scheduling may reduce a scheduling and turnaround time for sidelink communications. Each slot may be split into multiple sub-slots, where each sub-slot may have a physical sidelink control channel (PSCCH) and/or a PSSCH, and where each sub-slot may be self-schedulable and decodable. Each UE may select and reserve one or multiple sub-slots per slot. As a quantity of sub-slots increases per slot, which may enhance a scheduling latency and may be suitable for small packets (e.g., 32 bytes for IIoT), an increasing quantity of symbols should be allocated to gaps. For some use cases (e.g., if a large quantity of UEs need to be supported), such overhead may degrade the latency reduction gains.

FIG.7is a diagram illustrating an example700of a multiple sub-slot design, in accordance with the present disclosure.

As shown inFIG.7, a slot may be split into multiple sub-slots according to a given pattern (e.g., a length for each sub-slot and a quantity of sub-slots per slot). A sidelink control information type 1 (SCI-1) or PSCCH may only be at a beginning of each slot. Each SCI may indicate a transmission/reservation of a quantity of sub-slots in the same slot or in upcoming slots. The slot may include multiple sub-slots (e.g., sub-slot #0, sub-slot #1, sub-slot #2, and sub-slot #3) associated with PSSCHs. Automatic gain control (AGC) symbols may not be needed in the slot since a receiver may set the AGC based at least in part on a first symbol of the slot, and a same setting may be used for a reception of any of the PSSCH sub-slots. The slot may include a gap at an end of the slot, where the gap may be used for a Tx/Rx switching at a slot boundary in sidelink.

In a V2X system, a PSFCH resource may be a two-symbol duration, where a first symbol may be used for AGC training and a second symbol may be used to transmit hybrid automatic repeat request (HARQ) acknowledgement (ACK) feedback. The first symbol and the second symbol may be OFDM symbols. However, such a scheme may be insufficient for maintaining an ultra-reliable low latency communication (URLLC) quality of service (QoS) requirement. Since a sidelink may support URLLC, industrial IoT (IIoT), and/or extended reality (XR) applications, an enhancement to a PSFCH resource may be needed to increase a reliability of a HARQ-ACK feedback transmission, and to allow for CSI to be signaled in the PSFCH resource for a relatively quick feedback. The CSI may indicate a channel quality indicator (CQI), a rank indicator (RI), and/or power commands. URLLC, IIoT, and/or XR applications may have a diverse set of latency/reliability requirements, and the two-symbol duration may not provide a sufficient HARQ-ACK feedback reliability. The two-symbol duration of the PSFCH resource may not be sufficient, since one symbol may be used for AGC training, and a potential loss of the PSFCH resource may occur due to collisions between PSFCH transmissions.

In various aspects of techniques and apparatuses described herein, a first UE (e.g., an Rx UE) may receive, from a second UE (e.g., a Tx UE that acts as a primary UE) or a network node, a configuration for a resource pool. The resource pool may be associated with a PSFCH resource comprising more than two symbols. The first UE may receive, from the second UE, a sidelink transmission. The first UE may transmit, to the second UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols. A first portion of the PSFCH resource comprising more than two symbols may be used for an AGC training, and a second portion of the PSFCH resource comprising more than two symbols may be used for transmitting the HARQ-ACK feedback.

In some aspects, to improve a HARQ-ACK feedback reliability, adding more symbols in the PSFCH resource and repeating a HARQ-ACK feedback transmission may be important for maintaining an URLLC QoS requirement. To further improve the reliability, channel state information (CSI) from a PSSCH may be derived, and the PSFCH resource may be used for signaling the CSI. Thus, a quantity of symbols and PRBs may be increased in the PSFCH resource.

In some aspects, various PSFCH improvements described herein may support various consumer cases for a sidelink, as well as URLLC, IIoT, and/or XR applications. The PSFCH improvements described herein may consider a diverse set of latency/reliability requirements associated with URLLC, IIoT, and/or XR services. With the expansion of sidelink to non-V2X use cases, such as IIoT and consumer use cases (e.g., XR or smart wearables), the PSFCH improvements described herein may define sidelink schemes that support low latency and high reliability communications. The PSFCH improvements described herein may be associated with an increase in PSFCH symbols in the PSFCH resource, a PSFCH PRB assignment, a sidelink configuration, AGC symbol considerations, and/or a PRB selection design.

FIG.8is a diagram illustrating an example800associated with sidelink feedback channel resources having a plurality of symbols, in accordance with the present disclosure. As shown inFIG.8, communication may occur between a first UE (e.g., UE120a) and a second UE (e.g., UE120e). In some aspects, the first UE and the second UE may be included in a wireless network, such as wireless network100.

In some aspects, the first UE may be an Rx UE that receives a sidelink transmission. As non-limiting examples, the first UE may be smart glasses or a smartwatch. The second UE may be a Tx UE that transmits the sidelink transmission. The second UE may be a primary UE that controls a plurality of UEs including the first UE. The first UE and the second UE may communicate directly with a network node (not shown inFIG.8), or the first UE may communicate with the network node via the second UE.

As shown by reference number802, the first UE may receive, from the second UE or the network node, a configuration for a resource pool. The resource pool may be associated with a PSFCH resource comprising more than two symbols. A first portion of the PSFCH resource comprising more than two symbols may be used for an AGC training, and a second portion of the PSFCH resource comprising more than two symbols may be used for transmitting HARQ-ACK feedback. A size of the PSFCH resource may be defined by X+1, where X={1, 2, . . . }, with a default value of X=1 (as in a legacy design). In other words, as a default, the size of the PSFCH resource may be two symbols, but the size of the PSFCH resource may be increased to more than two symbols, which may improve a reliability when transmitting the HARQ-ACK feedback.

As shown by reference number804, the first UE may receive, from the second UE, a sidelink transmission. The first UE may receive the sidelink transmission from the second UE via a sidelink interface between the first UE and the second UE. The first UE may receive the sidelink transmission via a PSSCH or a PSCCH.

As shown by reference number806, the first UE may transmit, to the second UE and based at least in part on the sidelink transmission, the HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols. The first UE may transmit the HARQ-ACK feedback using the second portion of the PSFCH resource comprising more than two symbols.

In some aspects, the first UE may determine a PRB of the PSFCH resource comprising more than two symbols based at least in part on a function of a source identifier, a destination identifier, a quantity of PRBs in a frequency domain and a quantity of symbols in a time domain. The first UE may transmit the HARQ-ACK feedback using the PRB. In other words, the PRB used for transmitting the HARQ-ACK feedback may be based at least in part on a frequency domain dimension and a time domain dimension. The quantity of symbols in the time domain may exclude an AGC symbol.

In some aspects, the first UE may determine a plurality of PRBs of the PSFCH resource comprising more than two symbols based at least in part on a mini-slot index. The mini-slot index may be used to assign the plurality of PRBs on different symbols of different mini-slots. Each PRB may be used for a mini-slot HARQ-ACK feedback. A quantity of the different symbols may be equal to a quantity of the different mini-slots, or alternatively, a quantity of the different symbols may be less than a quantity of the different mini-slots, and two or more PRBs may be assigned per symbol.

In some aspects, the first UE may receive, from the second UE or the network node, an indication associated with a scheduling of the HARQ-ACK feedback. The indication may indicate a time and a frequency associated with one or more PRBs of the PSFCH resource comprising more than two symbols. The first UE may transmit the HARQ-ACK feedback based at least in part on the indication. In other words, the first UE may transmit the HARQ-ACK feedback using the one or more PRBs, which may be associated with the time and frequency as indicated by the indication.

In some aspects, the first UE may receive, from the network node, a configuration for a per bit repetition factor for the resource pool. The per bit repetition factor may be based at least in part on a priority or a QoS of the sidelink transmission. In some aspects, the first UE may receive, from the second UE, an indication of the per bit repetition factor for the resource pool, where the per bit repetition factor may be selected from a plurality of potential per bit repetition factors. The per bit repetition factor may be based at least in part on a CSI measurement, or a priority or a QoS of the sidelink transmission.

In some aspects, a size of PSFCH resources may be increased from two symbols to more than two symbols (e.g., more than two OFDM symbols). An increase to the size of PSFCH resources may be defined by X+1, where X={1, 2, . . . }, with a default value of X=1 (as in a legacy design). In other words, as a default, the size of PSFCH resources may be two symbols, but the size of the PSFCH resources may be increased to more than two symbols, which may improve the reliability of the HARQ-ACK feedback transmission. A greater quantity of PSFCH symbols, which may correspond to additional resources, may improve the reliability of the HARQ-ACK feedback transmission. A first symbol may be used for AGC training by being a repetition of a second symbol (e.g., a first symbol of X symbols).

FIG.9is a diagram illustrating an example900associated with sidelink feedback channel resources having a plurality of symbols, in accordance with the present disclosure.

As shown inFIG.9, a plurality of UEs may receive, from a network node, transmit a configuration for a resource pool associated with PSFCH resources with X+1 symbols, where X=1 is a legacy design. A size of the PSFCH resources may be more than two symbols, where a first symbol may be used for AGC by being a repetition of a second symbol (e.g., a first symbol of X symbols). For example, the PSFCH resources may include a first two symbols (e.g., original symbols), as well as two additional symbols (e.g., additional resources), based at least in part on the configuration.

In some aspects, the plurality of UEs may include a first UE (e.g., a first Rx UE, such as smart glasses), a second UE (e.g., a Tx UE or primary UE), and a third UE (e.g., a second Rx UE, such as a smartwatch). The second UE and/or the third UE may receive the configuration directly from the network node, or the second UE and/or the third UE may receive the configuration from the first UE, which may have received the configuration from the network node.

In some aspects, the first UE may transmit, to the second UE or the third UE, a sidelink transmission. The second UE or the third UE may transmit, to the first UE, a HARQ-ACK feedback with improved reliability based at least in part on the resource pool configured with X+1 symbols. The UE may transmit the HARQ-ACK feedback using the PSFCH resources associated with the X+1 symbols.

FIG.10is a diagram illustrating an example1000associated with sidelink feedback channel resources having a plurality of symbols, in accordance with the present disclosure.

As shown inFIG.10, a PSFCH may include multiple PSFCH symbols in a time domain. A PRB within a PSFCH symbol may be selected based at least in part on i=mod (source ID+destination ID, R), where R is a quantity of PRBs that a first UE (e.g., an Rx UE) may use in a frequency domain. The PRB within the PSFCH symbol may be selected for transmitting a HARQ-ACK feedback. When selecting the PRB within the PSFCH symbol, a new index for time may be added to incorporate the time domain. The new index for time may be defined as j=F(source ID, destination ID, Y). For example, F(source ID, destination ID, Y)=mod (source ID+destination ID+configured parameters, Y), where Y is a quantity of symbols in a PSFCH in the time domain (or those allocated for the first UE to use within a PSFCH resource), and Y excludes an AGC symbol. Further, F(.) may be any function, such as a mod operation. As a result, a time-domain dimension may be added when determining the PSFCH resource.

As indicated above,FIG.10is provided as an example. Other examples may differ from what is described with regard toFIG.10.

In some aspects, in a mini-slot scenario, a first UE (e.g., an Rx UE) may use a mini-slot index to assign PRBs on different PSFCH symbols (e.g., assign feedback bit(s) to PRBs across symbols) of a mini-slot, assuming that a quantity of PSFCH symbols is equal to a quantity of mini-slots. When the quantity of PSFCH symbols is less than the quantity of mini-slots, then more than one mini-slot feedback (e.g., HARQ-ACK feedback and CSI feedback) may be assigned to the same symbols (e.g., the first UE may use two or more PRBs per symbol).

FIG.11is a diagram illustrating an example1100associated with sidelink feedback channel resources having a plurality of symbols, in accordance with the present disclosure.

As shown inFIG.11, a PSFCH may include multiple PSFCH symbols in a time domain. For a 4 mini-slot case, mod (source ID+destination ID+mini-slot index+offset (depending on R)) may equal one. Four different PRBs of the4mini-slots may be assigned on different PSFCH symbols, and a sequence of HARQ-ACK feedback bits may be obtained. The sequence of bits may correspond to a HARQ-ACK feedback with improved reliability. Each PRB may be used for a mini-slot HARQ-ACK feedback. In some aspects, if a quantity of mini-slots is five, then a first PSFCH symbol may have two feedback bits/occasions. The feedback bits may be multiplexed on a same PRB using a single cyclic shift, or different cyclic shifts may be assigned to each feedback bit. In some cases, a PRB offset may be added for each Y assignment (e.g., for an assignment of Y symbols), where the offset may be RRC level configured or agreed upon between different UEs.

As indicated above,FIG.11is provided as an example. Other examples may differ from what is described with regard toFIG.11.

In some aspects, a second UE (e.g., a Tx UE or primary UE) may schedule a PSFCH transmission of a first UE (e.g., an Rx UE) using sidelink control information type 2 (SCI-2). The second UE may determine which PRB or set of PRBs is used by the first UE. Alternatively, the second UE may schedule the PSFCH transmission of the first UE using SCI-1, so that other UEs may overhear this information to avoid using the same PRB or set of PRBs. Each second UE may constitute a small cell or a mini network node. The second UE, which may be a centralized node controlling a plurality of UEs, may indicate a time-frequency resource for a first UE to use for transmitting HARQ-ACK feedback, where the time-frequency resource may be associated with the PRB. The second UE may transmit an indication of indices (i,j) associated with the PRB, where the indices may be associated with Y symbols of a PSFCH in a time domain and R PRBs of the PSFCH in a frequency domain. The indication may indicate a particular PRB (or set of PRBs) within the Y symbols of the PSFCH in the time domain and the R PRBs of the PSFCH in the frequency domain (for example, as shown inFIG.10).

In some aspects, in a sidelink mode1, a network node may transmit downlink control information (DCI) to a first UE. The DCI may indicate the indices (i,j) associated with the PRB. The DCI may indicate the PRB (or set of PRBs) within the Y symbols of the PSFCH in the time domain and the R PRBs of the PSFCH in the frequency domain. The first UE may use the indicated PRB when transmitting HARQ-ACK feedback.

In some aspects, to improve a reliability of HARQ-ACK bits, a HARQ-ACK bit may be transmitted multiple times based at least in part on a per bit repetition, such that a first UE (e.g., an Rx UE) may use y PRBs to transmit a bit y times. A network node may configure a resource pool to have a per bit repetition factor. The network node may configure the first UE with the per bit repetition factor. The per bit repetition factor may be configured via a PC5 interface. The per bit repetition factor may be configured via RRC signaling or a medium access control control element (MAC-CE). The per bit repetition factor may be common or valid to any resource pool. The per bit repetition factor may change based at least in part on a priority and/or a QoS of an underlying transmission. For example, a first priority may have a per bit repetition factor of one, a second priority may have a per bit repetition factor of two, and so on.

In some aspects, a second UE (e.g., a Tx UE or primary UE) may determine the per bit repetition factor based at least in part on CSI measurements and/or a priority/QoS of a transmission. The second UE may indicate the per bit repetition factor using one of two options. In a first option, a network node may configure potential per bit repetition factors as part of a resource pool configuration, and then the second UE may configure a first UE (e.g., an Rx UE) with one of the per bit repetition factors from the potential per bit repetition factors. In a second option, the second UE may indicate the per bit repetition factor to the first UE in SCI-2.

FIG.12is a diagram illustrating an example process1200performed, for example, by a first UE, in accordance with the present disclosure. Example process1200is an example where the first UE (e.g., UE120a) performs operations associated with sidelink feedback channel resources having a plurality of symbols.

As shown inFIG.12, in some aspects, process1200may include receiving, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols (block1210). For example, the first UE (e.g., using communication manager140and/or reception component1402, depicted inFIG.14) may receive, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols, as described above.

As further shown inFIG.12, in some aspects, process1200may include receiving, from the second UE, a sidelink transmission (block1220). For example, the first UE (e.g., using communication manager140and/or reception component1402, depicted inFIG.14) may receive, from the second UE, a sidelink transmission, as described above.

As further shown inFIG.12, in some aspects, process1200may include transmitting, to the second UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols (block1230). For example, the first UE (e.g., using communication manager140and/or transmission component1404, depicted inFIG.14) may transmit, to the second UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols, as described above.

In a first aspect, a first portion of the PSFCH resource comprising more than two symbols is used for an AGC training, and a second portion of the PSFCH resource comprising more than two symbols is used for transmitting the HARQ-ACK feedback.

In a second aspect, alone or in combination with the first aspect, process1200includes determining a PRB of the PSFCH resource comprising more than two symbols based at least in part on a function of a source identifier, a destination identifier, a quantity of PRBs in a frequency domain and a quantity of symbols in a time domain, wherein the HARQ-ACK feedback is transmitted using the PRB, and the quantity of symbols in the time domain excludes an AGC symbol.

In a third aspect, alone or in combination with one or more of the first and second aspects, process1200includes determining a plurality of PRBs of the PSFCH resource comprising more than two symbols based at least in part on a mini-slot index, wherein the mini-slot index is used to assign the plurality of PRBs on different symbols of different mini-slots, and each PRB is used for a mini-slot HARQ-ACK feedback.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, a quantity of the different symbols is equal to a quantity of the different mini-slots.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, a quantity of the different symbols is less than a quantity of the different mini-slots, and two or more PRBs are assigned per symbol.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, process1200includes receiving, from one of the second UE or the network node, an indication associated with a scheduling of the HARQ-ACK feedback, wherein the indication indicates a time and a frequency associated with one or more PRBs of the PSFCH resource comprising more than two symbols, and the HARQ-ACK feedback is transmitted based at least in part on the indication.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, process1200includes receiving, from the network node, a configuration for a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a priority or a QoS of the sidelink transmission.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, process1200includes receiving, from the second UE, an indication of a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a CSI measurement, or a priority or a QoS of the sidelink transmission.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, the first UE is an Rx UE that receives the sidelink transmission, wherein the second UE is a Tx UE that transmits the sidelink transmission, and the second UE is a primary UE that controls a plurality of UEs including the first UE.

FIG.13is a diagram illustrating an example process1300performed, for example, by a second UE, in accordance with the present disclosure. Example process1300is an example where the second UE (e.g., UE120e) performs operations associated with sidelink feedback channel resources having a plurality of symbols.

As shown inFIG.13, in some aspects, process1300may include transmitting, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols (block1310). For example, the second UE (e.g., using communication manager140and/or transmission component1504, depicted inFIG.15) may transmit, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols, as described above.

As further shown inFIG.13, in some aspects, process1300may include transmitting, to the first UE, a sidelink transmission (block1320). For example, the second UE (e.g., using communication manager140and/or transmission component1504, depicted inFIG.15) may transmit, to the first UE, a sidelink transmission, as described above.

As further shown inFIG.13, in some aspects, process1300may include receiving, from the first UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols (block1330). For example, the second UE (e.g., using communication manager140and/or reception component1502, depicted inFIG.15) may receive, from the first UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols, as described above.

In a first aspect, process1300includes determining a PRB of the PSFCH resource comprising more than two symbols based at least in part on a function of a source identifier, a destination identifier, a quantity of PRBs in a frequency domain and a quantity of symbols in a time domain, wherein the HARQ-ACK feedback is received using the PRB, and the quantity of symbols in the time domain excludes an AGC symbol.

In a second aspect, alone or in combination with the first aspect, process1300includes determining a plurality of PRBs of the PSFCH resource comprising more than two symbols based at least in part on a mini-slot index, wherein the mini-slot index is used to assign the plurality of PRBs on different symbols of different mini-slots.

In a third aspect, alone or in combination with one or more of the first and second aspects, process1300includes transmitting, to the first UE, an indication associated with a scheduling of the HARQ-ACK feedback, wherein the indication indicates a time and a frequency associated with one or more PRBs of the PSFCH resource comprising more than two symbols, and the HARQ-ACK feedback is received based at least in part on the indication.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, process1300includes transmitting, to the first UE, an indication of a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a CSI measurement, or a priority or a QoS of the sidelink transmission.

FIG.14is a diagram of an example apparatus1400for wireless communication, in accordance with the present disclosure. The apparatus1400may be a first UE, or a first UE may include the apparatus1400. In some aspects, the apparatus1400includes a reception component1402and a transmission component1404, which may be in communication with one another (for example, via one or more buses and/or one or more other components). As shown, the apparatus1400may communicate with another apparatus1406(such as a UE, a base station, or another wireless communication device) using the reception component1402and the transmission component1404. As further shown, the apparatus1400may include the communication manager140. The communication manager140may include a determination component1408, among other examples.

The reception component1402may receive, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols. The reception component1402may receive, from the second UE, a sidelink transmission. The transmission component1404may transmit, to the second UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

The determination component1408may determine a PRB of the PSFCH resource comprising more than two symbols based at least in part on a function of a source identifier, a destination identifier, a quantity of PRBs in a frequency domain and a quantity of symbols in a time domain, wherein the HARQ-ACK feedback is transmitted using the PRB, and the quantity of symbols in the time domain excludes an AGC symbol. The determination component1408may determine a plurality of PRBs of the PSFCH resource comprising more than two symbols based at least in part on a mini-slot index, wherein the mini-slot index is used to assign the plurality of PRBs on different symbols of different mini-slots, and each PRB is used for a mini-slot HARQ-ACK feedback.

The reception component1402may receive, from one of the second UE or the network node, an indication associated with a scheduling of the HARQ-ACK feedback, wherein the indication indicates a time and a frequency associated with one or more PRBs of the PSFCH resource comprising more than two symbols, and the HARQ-ACK feedback is transmitted based at least in part on the indication. The reception component1402may receive, from the network node, a configuration for a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a priority or a QoS of the sidelink transmission. The reception component1402may receive, from the second UE, an indication of a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a CSI measurement, or a priority or a QoS of the sidelink transmission.

FIG.15is a diagram of an example apparatus1500for wireless communication, in accordance with the present disclosure. The apparatus1500may be a second UE, or a second UE may include the apparatus1500. In some aspects, the apparatus1500includes a reception component1502and a transmission component1504, which may be in communication with one another (for example, via one or more buses and/or one or more other components). As shown, the apparatus1500may communicate with another apparatus1506(such as a UE, a base station, or another wireless communication device) using the reception component1502and the transmission component1504. As further shown, the apparatus1500may include the communication manager140. The communication manager140may include a determination component1508, among other examples.

The transmission component1504may transmit communications, such as reference signals, control information, data communications, or a combination thereof, to the apparatus1506. In some aspects, one or more other components of the apparatus1500may generate communications and may provide the generated communications to the transmission component1504for transmission to the apparatus1506. In some aspects, the transmission component1504may perform signal processing on the generated communications (such as filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, among other examples), and may transmit the processed signals to the apparatus1506. In some aspects, the transmission component1504may include one or more antennas, a modem, a modulator, a transmit MIMO processor, a transmit processor, a controller/processor, a memory, or a combination thereof, of the second UE described in connection withFIG.2. In some aspects, the transmission component1504may be co-located with the reception component1502in a transceiver.

The transmission component1504may transmit, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a PSFCH resource comprising more than two symbols. The transmission component1504may transmit, to the first UE, a sidelink transmission. The reception component1502may receive, from the first UE and based at least in part on the sidelink transmission, a HARQ-ACK feedback based at least in part on the PSFCH resource comprising more than two symbols.

The determination component1508may determine a PRB of the PSFCH resource comprising more than two symbols based at least in part on a function of a source identifier, a destination identifier, a quantity of PRBs in a frequency domain and a quantity of symbols in a time domain, wherein the HARQ-ACK feedback is received using the PRB, and the quantity of symbols in the time domain excludes an AGC symbol. The determination component1508may determine a plurality of PRBs of the PSFCH resource comprising more than two symbols based at least in part on a mini-slot index, wherein the mini-slot index is used to assign the plurality of PRBs on different symbols of different mini-slots.

The transmission component1504may transmit, to the first UE, an indication associated with a scheduling of the HARQ-ACK feedback, wherein the indication indicates a time and a frequency associated with one or more PRBs of the PSFCH resource comprising more than two symbols, and the HARQ-ACK feedback is received based at least in part on the indication. The transmission component1504may transmit, to the first UE, an indication of a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a CSI measurement, or a priority or a QoS of the sidelink transmission.

The number and arrangement of components shown inFIG.15are provided as an example. In practice, there may be additional components, fewer components, different components, or differently arranged components than those shown inFIG.15. Furthermore, two or more components shown inFIG.15may be implemented within a single component, or a single component shown inFIG.15may be implemented as multiple, distributed components. Additionally, or alternatively, a set of (one or more) components shown inFIG.15may perform one or more functions described as being performed by another set of components shown inFIG.15.

Aspect 1: A method of wireless communication performed by a first user equipment (UE), comprising: receiving, from a second UE or a network node, a configuration for a resource pool, wherein the resource pool is associated with a physical sidelink feedback channel (PSFCH) resource comprising more than two symbols; receiving, from the second UE, a sidelink transmission; and transmitting, to the second UE and based at least in part on the sidelink transmission, a hybrid automatic repeat request (HARQ) acknowledgement (ACK) feedback based at least in part on the PSFCH resource comprising more than two symbols.

Aspect 2: The method of Aspect 1, wherein a first portion of the PSFCH resource comprising more than two symbols is used for an automatic gain control training, and wherein a second portion of the PSFCH resource comprising more than two symbols is used for transmitting the HARQ-ACK feedback.

Aspect 3: The method of any of Aspects 1 through 2, further comprising: determining a physical resource block (PRB) of the PSFCH resource comprising more than two symbols based at least in part on a function of a source identifier, a destination identifier, a quantity of PRBs in a frequency domain and a quantity of symbols in a time domain, wherein the HARQ-ACK feedback is transmitted using the PRB, and wherein the quantity of symbols in the time domain excludes an automatic gain control symbol.

Aspect 4: The method of any of Aspects 1 through 3, further comprising: determining a plurality of physical resource blocks (PRBs) of the PSFCH resource comprising more than two symbols based at least in part on a mini-slot index, wherein the mini-slot index is used to assign the plurality of PRBs on different symbols of different mini-slots, and wherein each PRB is used for a mini-slot HARQ-ACK feedback.

Aspect 5: The method of Aspect 4, wherein a quantity of the different symbols is equal to a quantity of the different mini-slots.

Aspect 6: The method of Aspect 4, wherein a quantity of the different symbols is less than a quantity of the different mini-slots, and two or more PRBs are assigned per symbol.

Aspect 7: The method of any of Aspects 1 through 6, further comprising: receiving, from one of the second UE or the network node, an indication associated with a scheduling of the HARQ-ACK feedback, wherein the indication indicates a time and a frequency associated with one or more physical resource blocks of the PSFCH resource comprising more than two symbols, and wherein the HARQ-ACK feedback is transmitted based at least in part on the indication.

Aspect 8: The method of any of Aspects 1 through 7, further comprising: receiving, from the network node, a configuration for a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a priority or a quality of service of the sidelink transmission.

Aspect 9: The method of any of Aspects 1 through 8, further comprising: receiving, from the second UE, an indication of a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a channel state information measurement, or a priority or a quality of service of the sidelink transmission.

Aspect 10: The method of any of Aspects 1 through 9, wherein the first UE is a receive UE that receives the sidelink transmission, wherein the second UE is a transmit UE that transmits the sidelink transmission, and wherein the second UE is a primary UE that controls a plurality of UEs including the first UE.

Aspect 11: A method of wireless communication performed by a second user equipment (UE), comprising: transmitting, to a first UE, a configuration for a resource pool, wherein the resource pool is associated with a physical sidelink feedback channel (PSFCH) resource comprising more than two symbols; transmitting, to the first UE, a sidelink transmission; and receiving, from the first UE and based at least in part on the sidelink transmission, a hybrid automatic repeat request (HARQ) acknowledgement (ACK) feedback based at least in part on the PSFCH resource comprising more than two symbols.

Aspect 12: The method of Aspect 11, further comprising: determining a physical resource block (PRB) of the PSFCH resource comprising more than two symbols based at least in part on a function of a source identifier, a destination identifier, a quantity of PRBs in a frequency domain and a quantity of symbols in a time domain, wherein the HARQ-ACK feedback is received using the PRB, and wherein the quantity of symbols in the time domain excludes an automatic gain control symbol.

Aspect 13: The method of any of Aspects 11 through 12, further comprising: determining a plurality of physical resource blocks (PRBs) of the PSFCH resource comprising more than two symbols based at least in part on a mini-slot index, wherein the mini-slot index is used to assign the plurality of PRBs on different symbols of different mini-slots.

Aspect 14: The method of any of Aspects 11 through 13, further comprising: transmitting, to the first UE, an indication associated with a scheduling of the HARQ-ACK feedback, wherein the indication indicates a time and a frequency associated with one or more physical resource blocks of the PSFCH resource comprising more than two symbols, and wherein the HARQ-ACK feedback is received based at least in part on the indication.

Aspect 15: The method of any of Aspects 11 through 14, further comprising: transmitting, to the first UE, an indication of a per bit repetition factor for the resource pool, wherein the per bit repetition factor is based at least in part on a channel state information measurement, or a priority or a quality of service of the sidelink transmission.