Patent Description:
As the demand for mobile broadband access continues to increase, further improvements in LTE, NR, and other radio access technologies and the telecommunication standards that employ these technologies remain useful. Document <NPL> provides views on sidelink (SL) physical layer procedure with emphasis on power control and HARQ. It is observed that the resource for PSFCH is sufficient even at the situation of <NUM> ACK/NACK feedback in groupcast HARQ feedback Option <NUM>.

In one aspect, a method of wireless communication, performed by a user equipment (UE), is provided according to appended claim <NUM>.

In one aspect, a computer program is provided according to appended claim <NUM>.

In one aspect, an apparatus for wireless communication is provided according to appended claim <NUM>.

Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and/or processing system as substantially described herein with reference to and as illustrated by the accompanying drawings and specification.

<FIG> is a diagram illustrating an example <NUM> of a base station <NUM> in communication with a UE <NUM> in a wireless network, in accordance with various aspects of the present disclosure.

Transmit processor <NUM> may also generate reference symbols for reference signals (e.g., a cell-specific reference signal (CRS), a demodulation reference signal (DMRS), and/or the like) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS)).

On the uplink, at UE <NUM>, a transmit processor <NUM> may receive and process data from a data source <NUM> and control information (e.g., for reports that include RSRP, RSSI, RSRQ, CQI, and/or the like) from controller/processor <NUM>. The transceiver may be used by a processor (e.g., controller/processor <NUM>) and memory <NUM> to perform aspects of any of the methods described herein.

The transceiver may be used by a processor (e.g., controller/processor <NUM>) and memory <NUM> to perform aspects of any of the methods described herein.

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform one or more techniques associated with concurrent physical sidelink feedback channel (PSFCH) transmission, as described in more detail elsewhere herein. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform or direct operations of, for example, process <NUM> of <FIG> and/or other processes as described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively. In some aspects, memory <NUM> and/or memory <NUM> may include a non-transitory computer-readable medium storing one or more instructions for wireless communication. For example, the one or more instructions, when executed (e.g., directly, or after compiling, converting, interpreting, and/or the like) by one or more processors of the base station <NUM> and/or the UE <NUM>, may cause the one or more processors, the UE <NUM>, and/or the base station <NUM> to perform or direct operations of, for example, process <NUM> of <FIG> and/or other processes as described herein. In some aspects, executing instructions may include running the instructions, converting the instructions, compiling the instructions, interpreting the instructions, and/or the like.

In some aspects, UE <NUM> may include means for identifying multiple candidate sets of PSFCH transmissions, wherein the multiple candidate sets each include a plurality of PSFCH transmissions to provide hybrid automatic repeat request (HARQ) feedback for a plurality of sidelink communications received from one or more other UEs <NUM>, means for identifying, from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets, means for selecting, from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set that has a highest value for a utility parameter among utility parameters associated with each of the one or more candidate sets, means for transmitting, on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a HARQ feedback occasion, and/or the like. In some aspects, such means may include one or more components of UE <NUM> described in connection with <FIG>, such as controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, and/or the like.

<FIG> is a diagram illustrating an example frame structure <NUM> for frequency division duplexing (FDD) in a telecommunications system (e.g., NR).

In some aspects, "wireless communication structure" may refer to a periodic time-bounded communication unit defined by a wireless communication standard and/or protocol.

<FIG> is a diagram illustrating an example SS hierarchy <NUM>, which is an example of a synchronization communication hierarchy. As shown in <FIG>, the SS hierarchy <NUM> may include an SS burst set, which may include a plurality of SS bursts (identified as SS burst <NUM> through SS burst B-<NUM>, where B is a maximum number of repetitions of the SS burst that may be transmitted by the base station).

An interlace structure may be used for each of the downlink and uplink for FDD in certain telecommunications systems (e.g., NR). For example, Q interlaces with indices of <NUM> through Q - <NUM> may be defined, where Q may be equal to <NUM>, <NUM>, <NUM>, <NUM>, or some other value. Each interlace may include slots that are spaced apart by Q frames. In particular, interlace q may include slots q, q + Q, q + 2Q, etc., where q ∈ {<NUM>,. , Q - <NUM>}.

New Radio (NR) may refer to radios configured to operate according to a new air interface (e.g., other than Orthogonal Frequency Divisional Multiple Access (OFDMA)-based air interfaces) or fixed transport layer (e.g., other than Internet Protocol (IP)). In some aspects, NR may utilize OFDM with a CP (herein referred to as cyclic prefix OFDM or CP-OFDM) and/or SC-FDM on the uplink, may utilize CP-OFDM on the downlink and include support for half-duplex operation using time division duplexing (TDD). In some aspects, NR may, for example, utilize OFDM with a CP (herein referred to as CP-OFDM) and/or discrete Fourier transform spread orthogonal frequency-division multiplexing (DFT-s-OFDM) on the uplink, may utilize CP-OFDM on the downlink and include support for half-duplex operation using TDD. NR may include Enhanced Mobile Broadband (eMBB) service targeting wide bandwidth (e.g., <NUM> megahertz (MHz) and beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., <NUM> gigahertz (GHz)), massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communication (URLLC) service.

NR resource blocks may span <NUM> subcarriers with a subcarrier bandwidth of <NUM> or <NUM> kilohertz (kHz) over a <NUM> millisecond (ms) duration. Each slot may indicate a link direction (e.g., downlink (DL) or uplink (UL)) for data transmission and the link direction for each slot may be dynamically switched.

<FIG> is a diagram illustrating an example <NUM> of sidelink communications, in accordance with various aspects of the present disclosure.

As shown in <FIG>, a first UE <NUM>-<NUM> may communicate with a second UE <NUM>-<NUM> (and one or more other UEs <NUM>) via one or more sidelink channels <NUM>. The UEs <NUM>-<NUM> and <NUM>-<NUM> may communicate using the one or more sidelink channels <NUM> for P2P communications, D2D communications, V2X communications (e.g., which may include V2V communications, V2I communications, V2P communications, and/or the like), mesh networking, and/or the like. In some aspects, the UEs <NUM> (e.g., UE <NUM>-<NUM> and/or UE <NUM>-<NUM>) may correspond to one or more other UEs described elsewhere herein, such as UE <NUM>. In some aspects, the one or more sidelink channels <NUM> may use a PC5 interface and/or may operate in a high frequency band (e.g., the <NUM> band). Additionally, or alternatively, the UEs <NUM> may synchronize timing of transmission time intervals (TTIs) (e.g., frames, subframes, slots, symbols, and/or the like) using global navigation satellite system (GNSS) timing.

As further shown in <FIG>, the one or more sidelink channels <NUM> may include a physical sidelink control channel (PSCCH) <NUM>, a physical sidelink shared channel (PSSCH) <NUM>, and/or a PSFCH <NUM>. The PSCCH <NUM> may be used to communicate control information, similar to a PDCCH and/or a physical uplink control channel (PUCCH) used for cellular communications with a base station <NUM> via an access link or an access channel. The PSSCH <NUM> may be used to communicate data, similar to a PDSCH and/or a physical uplink shared channel (PUSCH) used for cellular communications with a base station <NUM> via an access link or an access channel. For example, the PSCCH <NUM> may carry sidelink control information (SCI) <NUM>, which may indicate various control information used for sidelink communications, such as one or more resources (e.g., time resources, frequency resources, spatial resources, and/or the like) where a transport block (TB) <NUM> may be carried on the PSSCH <NUM>. The TB <NUM> may include data. The PSFCH <NUM> may be used to communicate sidelink feedback <NUM>, such as HARQ feedback (e.g., acknowledgement or negative acknowledgement (ACK/NACK) information), transmit power control (TPC), a scheduling request (SR), and/or the like.

In some aspects, the one or more sidelink channels <NUM> may use resource pools. For example, a scheduling assignment (e.g., included in SCI <NUM>) may be transmitted in sub-channels using specific resource blocks (RBs) across time. In some aspects, data transmissions (e.g., on the PSSCH <NUM>) associated with a scheduling assignment may occupy adjacent RBs in the same subframe as the scheduling assignment (e.g., using frequency division multiplexing). In some aspects, a scheduling assignment and associated data transmissions are not transmitted on adjacent RBs.

In some aspects, a UE <NUM> may operate using a transmission mode where resource selection and/or scheduling is performed by the UE <NUM> (e.g., rather than a base station <NUM>). In some aspects, the UE <NUM> may perform resource selection and/or scheduling by sensing channel availability for transmissions. For example, the UE <NUM> may measure a received signal strength indicator (RSSI) parameter (e.g., a sidelink-RSSI (S-RSSI) parameter) associated with various sidelink channels, may measure a reference signal received power (RSRP) parameter (e.g., a PSSCH-RSRP parameter) associated with various sidelink channels, may measure a reference signal received quality (RSRQ) parameter (e.g., a PSSCH-RSRQ parameter) associated with various sidelink channels, and/or the like, and may select a channel for transmission of a sidelink communication based at least in part on the measurement(s).

Additionally, or alternatively, the UE <NUM> may perform resource selection and/or scheduling using SCI <NUM> received in the PSCCH <NUM>, which may indicate occupied resources, channel parameters, and/or the like. Additionally, or alternatively, the UE <NUM> may perform resource selection and/or scheduling by determining a channel busy rate (CBR) associated with various sidelink channels, which may be used for rate control (e.g., by indicating a maximum number of resource blocks that the UE <NUM> can use for a particular set of subframes).

In the transmission mode where resource selection and/or scheduling is performed by a UE <NUM>, the UE <NUM> may generate sidelink grants, and may transmit the grants in SCI <NUM>. A sidelink grant may indicate, for example, one or more parameters (e.g., transmission parameters) to be used for an upcoming sidelink transmission, such as one or more resource blocks to be used for the upcoming sidelink transmission on the PSSCH <NUM> (e.g., for TBs <NUM>), one or more subframes to be used for the upcoming sidelink transmission, a modulation and coding scheme (MCS) to be used for the upcoming sidelink transmission, and/or the like. In some aspects, a UE <NUM> may generate a sidelink grant that indicates one or more parameters for semi-persistent scheduling (SPS), such as a periodicity of a sidelink transmission. Additionally, or alternatively, the UE <NUM> may generate a sidelink grant for event-driven scheduling, such as for an on-demand sidelink message.

<FIG> is a diagram illustrating an example <NUM> of sidelink communications and access link communications, in accordance with various aspects of the present disclosure.

As shown in <FIG>, a transmitter (Tx)/receiver (Rx) UE <NUM> and an Rx/Tx UE <NUM> may communicate with one another via a sidelink, as described above in connection with <FIG>. As further shown, in some sidelink modes, a base station <NUM> may communicate with the Tx/Rx UE <NUM> via a first access link. Additionally, or alternatively, in some sidelink modes, the base station <NUM> may communicate with the Rx/Tx UE <NUM> via a second access link. The Tx/Rx UE <NUM> and/or the Rx/Tx UE <NUM> may correspond to one or more UEs described elsewhere herein, such as the UE <NUM> of <FIG>. Thus, a direct link between UEs <NUM> (e.g., via a PC5 interface) may be referred to as a sidelink, and a direct link between a base station <NUM> and a UE <NUM> (e.g., via a Uu interface) may be referred to as an access link. Sidelink communications may be transmitted via the sidelink, and access link communications may be transmitted via the access link. An access link communication may be either a downlink communication (from a base station <NUM> to a UE <NUM>) or an uplink communication (from a UE <NUM> to a base station <NUM>).

<FIG> is a diagram illustrating an example HARQ resource configuration <NUM> for sidelink communications, in accordance with various aspects of the present disclosure.

As described above, in some circumstances, two or more subordinate entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, V2X communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., a first UE) to another subordinate entity (e.g., a second UE) without relaying the signal through the scheduling entity (e.g., UE or BS), even though the scheduling entity may be utilized for scheduling and/or control purposes. In some aspects, the sidelink signals may be communicated using a licensed frequency spectrum, an unlicensed frequency spectrum (e.g., an industrial, scientific, and medical (ISM) radio band, such as <NUM>, which is reserved for purposes other than cellular communication such as wireless local area network communication), and/or the like.

As shown in the example HARQ resource configuration <NUM> in <FIG>, a HARQ feedback occasion may include a time-domain duration (e.g., one or more symbols) and a plurality of frequency-domain resources (e.g., a plurality of sub-channels) that are reserved for HARQ feedback on the sidelink. For example, the HARQ feedback may include an acknowledgment (ACK) to indicate that a UE successfully received a sidelink communication, a negative acknowledgement (NACK) to indicate that the UE failed to receive the sidelink communication, and/or the like. In some aspects, the frame structure of the sidelink may include a plurality of HARQ feedback occasions, and a time between the HARQ feedback occasions may define a system-wide PSSCH gap. The plurality of HARQ feedback occasions may be periodic (e.g., may occur at a particular time interval), may be configured at particular time-domain locations, and/or the like. In some aspects, a HARQ feedback occasion may be a multi-slot HARQ feedback occasion, in that the HARQ feedback occasion may be used to aggregate HARQ feedback for sidelink communications that were transmitted in a plurality of sub-channels and a plurality of slots that occurred prior to the HARQ feedback occasion.

As further shown in <FIG>, the frequency-domain resources in each HARQ feedback occasion may be partitioned into different HARQ resource regions, each of which may include various sub-channels that correspond to HARQ resources that one or more UEs can use to transmit HARQ feedback. As an example, in <FIG>, the frequency-domain resources in the HARQ feedback occasion may include a first HARQ resource region for odd-numbered transmitting UEs and a second HARQ resource region for even-numbered transmitting UEs (e.g., based on respective identifiers associated with the UEs). In some aspects, a UE may generally receive a HARQ configuration (e.g., from another UE, a base station in a wireless network, and/or the like) that identifies a HARQ resource to be used to transmit HARQ feedback, may be hard-coded with the HARQ configuration (e.g., the HARQ configuration may be stored on a UE prior to deployment in a wireless network), and/or the like. Accordingly, a UE may identify a HARQ resource (e.g., a sub-channel), in the HARQ feedback occasion, for transmitting HARQ feedback for a sidelink communication based at least in part on a time-domain resource (e.g., a slot) and a frequency-domain resource (e.g., a sub-channel) in which the sidelink communication was received.

Accordingly, in some cases, a UE may provide, to another UE, feedback associated with a sidelink communication transmitted by the other UE on a sidelink between the UE and the other UE. The feedback may include, for example, HARQ feedback (e.g., an ACK to indicate that the UE successfully received the sidelink communication, a NACK to indicate that the UE failed to receive the sidelink communication, and/or the like). The UE may transmit the HARQ feedback in one or more PSFCH transmissions on the sidelink. In some cases, as shown in <FIG>, the sidelink may include a frame structure in which one or more HARQ feedback occasions may be used for transmitting the one or more PSFCH transmissions. Unlike a cellular communication link with a base station, where the UE may provide HARQ feedback to a single base station, the UE may provide HARQ feedback to multiple UEs on a sidelink in a single HARQ feedback occasion. However, if the UE is scheduled to provide a quantity of HARQ feedback that exceeds a maximum quantity that the UE can and/or is permitted to transmit in a single HARQ feedback occasion, the UE may be unable to determine which PSFCH transmissions to transmit in the HARQ feedback occasion. Furthermore, in some cases, the UE may be unable to determine how many PSFCH transmissions to transmit in the HARQ feedback occasion. For example, as a quantity of concurrent PSFCH transmissions increases, less transmit power is allocated to each PSFCH transmission (e.g., because a power budget is split among more PSFCH transmissions), there may be an additional power backoff because a transmission waveform may become a multi-cluster, additional PSFCH transmissions may increase leakage (e.g., into one or more RBs that are allocated to PSFCH transmissions for other UEs), and/or the like, which may adversely affect PSFCH reception.

Some aspects described herein relate to techniques and apparatuses for concurrent PSFCH transmission. For example, when a UE has multiple PSFCH transmissions to transmit in a given HARQ feedback occasion (e.g., based at least in part on a plurality of sidelink communications that are received from one or more other UEs on a sidelink, such as a PSSCH, a PSCCH, and/or the like), the UE may identify a subset of the PSFCH transmissions to be transmitted in a next HARQ feedback occasion using the techniques described in further detail herein. For example, in some aspects, the UE may identify various candidate sets of PSFCH transmissions that each include a quantity of PSFCH transmissions that satisfies a threshold value (e.g., is less than or equal to a maximum number of PSFCH transmissions that the UE has a capability to transmit and/or is permitted to transmit in a single HARQ feedback occasion). For each candidate set, the UE may estimate a link budget requirement for each individual PSFCH transmission and generate a bitmap indicating whether the estimated link budget requirement can be met for each individual PSFCH transmission, based at least in part on a transmit power constraint (e.g., a maximum power reduction (MPR) value, an additional MPR (A-MPR) value, and/or the like). In some aspects, the UE may assign a utility value to each bit in the bitmap and select a particular candidate set that provides a highest combined utility return. Accordingly, the UE may transmit the candidate set that provides the highest combined utility return in the next HARQ feedback occasion. In this way, the UE may provide HARQ feedback for multiple sidelink communications in a single HARQ feedback occasion in a manner that allocates appropriate transmit power to each PSFCH transmission, complies with transmit power constraints, provides a maximum return on transmission utility, and/or the like.

<FIG> are diagrams illustrating an example implementation <NUM> of concurrent PSFCH transmission, in accordance with various aspects of the present disclosure. As shown in <FIG>, example implementation <NUM> may include a plurality of UEs (e.g., UEs 120a, 120e, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>, <NUM>, and/or the like) communicating over a sidelink. In the illustrated example, a particular UE receives sidelink communications from one or more other UEs and determines a set of PSFCH transmissions to be transmitted to a subset of the other UEs in a next HARQ feedback occasion. Accordingly, in the following description, the other UEs that send the sidelink communications may be referred to as "other UEs," and the particular UE that receives the sidelink communications and determines the set of PSFCH transmissions to be transmitted in the next HARQ feedback occasion may be generally referred to as "the UE. " Furthermore, although the example implementation <NUM> illustrated in <FIG> includes three (<NUM>) other UEs that send sidelink communications to the UE, in some aspects, the UE may receive sidelink communications from a greater or lesser quantity of other UEs. In general, the UE and the other UEs may be included in a wireless network (e.g., wireless network <NUM>) and may communicate via a sidelink. In some aspects, the sidelink may be configured with a frame structure, such as the frame structure <NUM> illustrated in <FIG>, a HARQ resource configuration, such as the HARQ resource configuration <NUM> illustrated in <FIG>, and/or the like.

As shown in <FIG>, and by reference number <NUM>, the UE and the other UEs may communicate via the sidelink by transmitting and/or receiving sidelink communications via the sidelink. For example, the UE may receive a plurality of sidelink communications on the sidelink from the other UEs, each of which may transmit one or more sidelink communications to the UE. In some aspects, the sidelink communications may be transmitted and received via a PSCCH, a PSSCH, a PSFCH, and/or the like. In some aspects, the plurality of sidelink communications may be transmitted on one or more channels or sub-channels of the sidelink. In this case, each sidelink communication may be transmitted in one or more time-domain resources (e.g., across one or more slots, across one or more symbols, and/or the like) and/or in one or more frequency-domain resources (e.g., in a sub-channel of the frequency bandwidth of the sidelink). In some aspects, a sub-channel may include a plurality of subcarriers of the frequency bandwidth sidelink, one or more resource blocks (RBs) of the frequency bandwidth of the sidelink, and/or the like.

As further shown in <FIG>, and by reference number <NUM>, the UE may determine a set of PSFCH transmissions to be transmitted in a next HARQ feedback occasion, where each PSFCH transmission may include HARQ feedback for a sidelink communication received from another UE. For example, in some aspects, the HARQ feedback for a particular sidelink communication may include an ACK to indicate, to a transmitter of the sidelink communication (e.g., another UE), that the sidelink communication was successfully received and decoded. Additionally, or alternatively, the HARQ feedback may include a NACK to indicate, to the transmitter of the sidelink communication, that the sidelink communication was not successfully received and/or decoded. In some aspects, the UE may determine that the HARQ feedback to be included in a particular PSFCH transmission is to be an ACK if the UE is capable of decoding both control information (e.g., (SCI) included in the sidelink communication and corresponding data (e.g., a payload) of the sidelink communication. In some aspects, the UE may determine that the HARQ feedback to be included in a particular PSFCH transmission is to be a NACK if the UE fails to successfully decode the control information included in the sidelink communication and/or the corresponding data of the sidelink communication.

In some aspects, the UE and the other UEs may communicate using an ACK/NACK HARQ feedback configuration, in which a receiver UE (e.g., the UE) is to transmit an ACK based at least in part on successfully receiving and decoding a sidelink communication from a transmitter UE (e.g., another UE), and is to transmit a NACK for a sidelink communication that the receiver UE is unable to decode. In some aspects, the UE and the other UEs may communicate using a NACK-only HARQ feedback configuration, in which a receiver UE does not transmit HARQ feedback for sidelink communications that are successfully received and decoded, and only transmits a NACK for sidelink communications that the receiver UE is unable to decode.

In some aspects, the UE may be configured with a parameter that indicates a maximum quantity of PSFCH transmissions that the UE is permitted to transmit in a single HARQ feedback occasion. For example, in some aspects, the parameter that indicates the maximum quantity of PSFCH transmissions that the UE is permitted to transmit in a single HARQ feedback occasion may be configured by a base station and/or another component in the wireless network based at least in part on a concurrent transmission capability of the UE, a configured limit, congestion on a PSSCH channel, congestion on a PSCCH channel, congestion on a PSFCH channel, and/or the like. Accordingly, in some aspects, the UE may select up to the maximum quantity of PSFCH transmissions to transmit in the next HARQ feedback occasion. However, as mentioned above, in some cases transmitting additional PSFCH transmissions may create various challenges, such as less transmit power being available to allocate to each PSFCH transmission, additional power backoffs due to a waveform becoming multi-cluster, and/or the like.

Accordingly, in some aspects, the UE may determine the set of PSFCH transmissions to transmit in the next HARQ feedback occasion to maximize a utility return (e.g., a relative value or usefulness) from the PSFCH transmissions. For example, the UE may identify various candidate sets of PSFCH transmissions that each include a quantity of PSFCH transmissions that satisfies a threshold value (e.g., the maximum quantity of PSFCH transmissions that the UE is permitted to transmit in a single HARQ feedback occasion), identify certain PSFCH transmissions in each candidate set for which individual link budget requirements can be satisfied based at least in part on a transmit power constraint, and select a particular candidate set to be transmitted in the next HARQ feedback occasion by applying a utility function to the individual PSFCH transmissions in each candidate set.

As shown in <FIG>, and by reference number <NUM>, the UE may identify one or more candidate sets of PSFCH transmissions with a highest priority. For example, a parameter (M) may represent the maximum quantity of concurrent PSFCH transmissions, and the UE may identify candidate sets of n PSFCH transmissions with a highest priority for each n ≤ M (e.g., if the maximum quantity of concurrent PSFCH transmissions is five (<NUM>), the UE may identify one or more candidate sets that include one (<NUM>) PSFCH transmission with a highest priority, one or more candidate sets that include two (<NUM>) PSFCH transmissions with a highest priority, and/or the like). In some aspects, the UE may identify the PSFCH transmissions with the highest priority using various techniques. For example, the UE may determine that a first sidelink communication has a higher priority than a second sidelink communication, and may include the PSFCH transmission with the HARQ feedback for the first sidelink communication in the one or more candidate sets. As another example, a priority may be determined for each PSFCH transmission that includes HARQ feedback, and the UE may populate the one or more candidate sets starting with PSFCH transmissions that have the highest priority and continuing with PSFCH transmissions that have a gradually decreasing priority until the one or more candidate sets have been populated with n PSFCH transmissions. As another example, a priority threshold may be defined, whereby the candidate sets may only include PSFCH transmissions having a priority that satisfies the priority threshold.

In some aspects, the UE may determine the priority for a particular PSFCH transmission using various techniques. For example, in some aspects, the priority may depend on whether the PSFCH transmission includes an ACK or a NACK, with a unicast, multicast, and/or groupcast NACK having a higher priority than a unicast, multicast, and/or groupcast ACK (e.g., because a sidelink communication that is unsuccessfully received may not be retransmitted if a NACK is not sent, whereas the worst case scenario from not sending an ACK is that a successfully received sidelink communication will be retransmitted). In another example, the priority for a particular PSFCH transmission may be based at least in part on SCI associated with the sidelink communication. For example, the SCI may be included in a control portion associated with the data portion of the sidelink communication, and the SCI may include a field or value that indicates or specifies the priority of the sidelink communication. In other examples, the priority for a particular PSFCH transmission may be based at least in part on a distance between the UE and the (other) UE that transmitted the sidelink communication (e.g., prioritizing PSFCH transmissions for other UEs that are located closer to the UE to ensure that data sent from nearby transmitters is successfully decoded, prioritizing PSFCH transmissions for other UEs that are located farther from the UE to provide the transmitter with feedback roughly indicating a transmission range for the sidelink communication), signal measurements such as RSRP, RSSI, RSRP, CQI, and/or the like (e.g., prioritizing PSFCH transmissions with a larger RSRP, as a larger RSRP measurement may indicate that the other UE is closer to the UE), a frequency location to be used for the PSFCH transmission (e.g., as indicated by a time and/or frequency location of a data channel), a transmission mode associated with the sidelink communication (e.g., with a unicast transmission mode having a greater priority than a groupcast transmission mode, and the groupcast transmission mode having a higher priority than a broadcast transmission mode), and/or the like.

As further shown in <FIG>, and by reference number <NUM>, the UE may estimate link budget requirements for individual PSFCH transmissions in each of the one or more candidate sets of PSFCH transmissions. In some aspects, the link budget requirements for the individual PSFCH transmissions may be estimated based at least in part on propagation characteristics between the UE and the other UEs. For example, the propagation characteristics may include a path loss, shadowing, antenna gain, and/or the like, which may generally be reciprocal between the UE and the other UEs (e.g., if there are certain obstacles, reflectors, and/or the like in a path between the UE and the other UEs, the propagation characteristics may be reciprocal in both directions). Accordingly, because the propagation characteristics between the UE and the other UEs are reciprocal, the UE may estimate an attenuation for a PSFCH transmission to be sent to a particular other UE based on estimated attenuation associated with the sidelink communication received from the particular other UE via a PSSCH or PSCCH.

Accordingly, to estimate the link budget requirement for a particular PSFCH transmission, the UE may estimate the attenuation associated with the corresponding sidelink communication received via a PSSCH or PSCCH. In some aspects, the attenuation may be represented by the difference between an original transmission power (P<NUM>) associated with the corresponding sidelink communication and an RSRP measurement associated with the corresponding sidelink communication. For example, in some aspects, the original transmission power (P<NUM>) may be a fixed value that is signaled to the UE, indicated in SCI, and/or the like, and the RSRP measurement may be obtained by measuring a power level at which the sidelink communication is received via the PSSCH or PSCCH. Accordingly, a strong RSRP measurement may generally indicate a strong link, a small distance between the UE and the other UE, and/or the like, in which case the PSFCH transmission that includes HARQ feedback for the sidelink communication may have a relatively low link budget requirement. In another example, a weak RSRP measurement may generally indicate a weak link, a large distance between the UE and the other UE, and/or the like, in which case the PSFCH transmission that includes HARQ feedback for the sidelink communication may have a relatively high link budget requirement. In some aspects, the UE may determine the RSRP measurement (and thus the link budget requirement) for a PSFCH transmission to be sent to a particular other UE based on the corresponding sidelink communication, or the UE may determine an average RSRP for multiple sidelink communications received from the particular other UE over a given time period in order to obtain a more accurate RSRP measurement.

In some aspects, based at least in part on the attenuation associated with a sidelink communication received from a particular other UE, the UE may estimate the link budget requirement for the PSFCH transmission as follows: <MAT> where P<NUM> represents a transmit power available to be allocated to the individual PSFCH transmission to the other UE, the expression (P<NUM> - RSRP) represents the attenuation associated with the sidelink communication received from the other UE and therefore the attenuation of the PSFCH transmission to the other UE based at least in part on the reciprocal propagation characteristics, N represents noise (e.g., thermal noise) that the UE can measure within a transmission bandwidth for the PSFCH transmission, and SNR is a minimum SNR (signal-to-noise ratio) for the other UE to be able to reliably decode the PSFCH transmission (e.g., a higher SNR than an SNR for detecting the PSFCH transmission).

In some aspects, the UE may determine a value for P<NUM>, representing the transmit power available to be allocated to an individual PSFCH transmission to a particular other UE, based on one or more transmit power constraints. In some aspects, the one or more transmit power constraints may generally include a maximum transmit power capability of the UE (e.g., a maximum output power), one or more parameters that relate to a power backoff, one or more power sharing rules to be applied to concurrent PSFCH transmissions, and/or the like. For example, the one or more parameters that relate to the power backoff may include a maximum power reduction (MPR) value by which the maximum transmit power capability of the UE is to be reduced (e.g., to control adjacent channel leakage). In some aspects, the parameters that relate to the power backoff may further include an additional MPR (A-MPR) value that is added to the MPR value to provide additional spectral emission control (e.g., the A-MPR value specifies a further amount by which the maximum transmit power capability of the UE is to be reduced due to regulatory, deployment, or other constraints). Accordingly, based on the maximum transmit power capability of the UE and the one or more parameters that relate to the power backoff (e.g., MPR, A-MPR, and/or the like), the UE may determine a maximum transmit power that is available to allocate among a quantity of n concurrent PSFCH transmissions in a particular candidate set.

In some aspects, the UE may apply one or more power sharing rules to determine an allocation of the maximum available transmit power among the n PSFCH transmissions in a particular candidate set. For example, in some aspects, the UE may equally divide the maximum available transmit power among the n PSFCH transmissions in a particular candidate set, in which case the transmit power available to allocate to an individual PSFCH transmission (P<NUM>) may be the maximum available transmit power divided by n. Additionally, or alternatively, in some aspects, all RBs may have an equal power spectrum density, in which case the maximum available transmit power may be divided among a quantity of RBs in which the n PSFCH transmissions are to be sent, and power allocated to a particular RB is divided among PSFCH transmissions allocated to the particular RB (e.g., equally, according to priority, according to an estimated link budget requirement, and/or the like). Additionally, or alternatively, in some aspects, a value for P<NUM> that satisfies the link budget requirement may be determined for each individual PSFCH transmission, and power may be allocated to each individual PSFCH transmission in a candidate set according to a descending priority until a total power budget has been exhausted.

As shown in <FIG>, and by reference number <NUM>, the UE may generate, for each candidate set, a bitmap indicating which PSFCH transmissions are estimated to meet link budget requirements. For example, as described above, the UE may estimate link budget requirements for each individual PSFCH transmission (e.g., based on an original transmit power for a sidelink communication, an RSRP measurement associated with the sidelink communication, noise in a PSFCH transmission bandwidth, a minimum SNR to decode the PSFCH transmission, and/or the like). Furthermore, as described above, the UE may determine a transmit power that is available to be allocated to each individual PSFCH transmission (e.g., based on a maximum transmit power capability, an MPR value and/or A-MPR value, one or more power sharing rules, and/or the like). Accordingly, in some aspects, the UE may determine whether the estimated link budget requirement can be met for each individual PSFCH transmission in a candidate set (e.g., based on whether P<NUM> - (P<NUM> - RSRP) - N ≥ SNR), and the UE may generate a bitmap for each candidate set that indicates whether the estimated link budget can be satisfied for each individual PSFCH transmission. For example, in some aspects, a bit corresponding to an individual PSFCH transmission may be set to a first value (e.g., zero (<NUM>)) to indicate that the estimated link budget cannot be satisfied for the PSFCH transmission, or to a second value (e.g., one (<NUM>)) to indicate that the estimated link budget can be satisfied.

As further shown in <FIG>, and by reference number <NUM>, the UE may assign a utility to each bit in the bitmap generated for each of the one or more candidate sets. For example, for a particular bit that has been set to the first value (e.g., zero) to indicate that the estimated link budget for the corresponding PSFCH transmission cannot be satisfied, the utility assigned to the bit may have a negative value based at least in part on a potential of the PSFCH to create harmful interference to other PSFCH transmissions (e.g., due to in-band emission (IBE) and/or intermodulation distortion (IMD) leakage, raised noise at another UE intended to receive the PSFCH transmission, and/or the like). Alternatively, in some aspects, the bit may be assigned a small positive value (e.g., a positive value that satisfies a threshold) where the PSFCH transmission is associated with a multicast configuration (e.g., where PSFCH transmissions from multiple UEs are combined at the other UE intended to receive the PSFCH transmission such that the PSFCH transmission can be decoded even if the individual PSFCH transmission cannot be successfully decoded standing alone). Alternatively, the bit may be assigned a zero value or a null value in cases where the PSFCH transmission serves no utility (e.g., does not create harmful interference, does not have the potential to be combined with other PSFCH transmissions in a multicast configuration, and/or the like).

In some aspects, for a particular bit that has been set to the second value (e.g., one) to indicate that the estimated link budget for the corresponding PSFCH transmission can be satisfied, the utility assigned to the bit may have a positive value that is generally greater than the small positive value that can be assigned to bits corresponding to PSFCH transmissions for which the estimated link budget cannot be satisfied. For example, in some aspects, the positive value assigned to a particular bit associated with a PSFCH transmission having an estimated link budget that can be satisfied may be based at least in part on a priority associated with the PSFCH transmission (e.g., a bit associated with a high priority PSFCH transmission may be assigned a relatively higher utility value), a distance between the UE and the other UE intended to receive the PSFCH transmission (e.g., a PSFCH transmission intended for another UE located close to the UE may be assigned a relatively higher utility value), an RSRP measurement between the UE and the other UE intended to receive the PSFCH transmission (e.g., a PSFCH transmission intended for another UE with a strong RSRP measurement may be assigned a relatively higher utility value), a remaining delay budget associated with a corresponding sidelink communication (e.g., a PSFCH transmission to indicate a NACK for a delay-sensitive packet may be assigned a relatively higher utility value to ensure that the delay-sensitive packet is retransmitted before the remaining delay budget is exhausted), a current packet reception rate or a bit rate on a link between the UE and the other UE intended to receive the PSFCH transmission (e.g., relatively higher utility values may be assigned to a bit associated with a PSFCH transmission related to a PSSCH, a PSCCH, or another suitable link that has a high packet fail rate or a low bit rate), and/or the like.

As shown in <FIG>, and by reference number <NUM>, the UE may select a particular candidate set that has a highest combined utility. For example, in some aspects, a utility return for a particular candidate set may be determined based at least in part on a combination of the utility values assigned to each bit in the bitmap that corresponds to the particular candidate set. For example, the utility return for a particular candidate set may correspond to a sum of the utility values assigned to each bit in the bitmap that corresponds to the particular candidate set, a squared sum of the utility values assigned to each bit in the bitmap that corresponds to the particular candidate set, and/or the like. In the latter case, when determining the squared sum of the utility values, a sign (e.g., positive or negative) associated with the utility value may be preserved. For example, after a negative utility value is squared, the squared value may be multiplied by negative one or another suitable expression (e.g., <MAT>, where u is the negative utility value) to preserve the negative sign of the original utility value.

As shown in <FIG>, and by reference number <NUM>, the UE may transmit PSFCH transmissions that are included in the selected candidate set to the appropriate other UEs in the next HARQ feedback occasion. For example, the PSFCH transmissions may be transmitted over a PSFCH in one or more RBs that are allocated to the PSFCH transmissions. Furthermore, in some aspects, the PSFCH transmissions may be transmitted according to the one or more power sharing rules described in further detail above. For example, a total transmit power that is available to use in the HARQ feedback occasion (e.g., subject to a transmit power constraint, such as an MPR value, an A-MPR value, and/or the like) may be equally divided among the PSFCH transmissions that are included in the selected candidate set. Additionally, or alternatively, the total transmit power available to use in the HARQ feedback occasion may be equally divided among a set of RBs that are allocated to the PSFCH transmissions, and in some cases, a portion of the total transmit power allocated to a particular RB may be divided among multiple PSFCH transmissions that share the RB (e.g., the portion of the total transmit power allocated to the particular RB may be divided equally among the PSFCH transmissions that share the RB, divided according to priority such as allocating more transmit power to higher priority PSFCH transmissions, divided according to an estimated link budget requirement, and/or the like). Additionally, or alternatively, available transmit power may be allocated to individual PSFCH transmissions in the selected candidate set according to a descending priority until a total power budget has been exhausted.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process <NUM> is an example where a UE (e.g., UE <NUM>, UE <NUM>, Tx/Rx UE <NUM>, Rx/Tx UE <NUM>, and/or the like) performs operations associated with concurrent PSFCH transmission.

As shown in <FIG>, in some aspects, process <NUM> may include identifying multiple candidate sets of PSFCH transmissions, wherein the multiple candidate sets each include a plurality of PSFCH transmissions to provide HARQ feedback for a plurality of sidelink communications received from one or more other UEs (block <NUM>). For example, the UE (e.g., using controller/processor <NUM>, memory <NUM>, and/or the like) may identify multiple candidate sets of PSFCH transmissions, as described above. In some aspects, the multiple candidate sets each include a plurality of PSFCH transmissions to provide HARQ feedback for a plurality of sidelink communications received from one or more other UEs.

As further shown in <FIG>, in some aspects, process <NUM> may include identifying, from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets (block <NUM>). For example, the UE (e.g., using controller/processor <NUM>, memory <NUM>, and/or the like) may identify, from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets, as described above.

As further shown in <FIG>, in some aspects, process <NUM> may include selecting, from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set that has a highest value for a utility parameter among utility parameters associated with each of the one or more candidate sets (block <NUM>). For example, the UE (e.g., using controller/processor <NUM>, memory <NUM>, and/or the like) may select, from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set that has a highest value for a utility parameter among utility parameters associated with each of the one or more candidate sets, as described above.

As further shown in <FIG>, in some aspects, process <NUM> may include transmitting, on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a HARQ feedback occasion (block <NUM>). For example, the UE (e.g., using controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, and/or the like) may transmit, on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a HARQ feedback occasion, as described above.

In a first aspect, the multiple candidate sets of PSFCH transmissions are identified based at least in part on one or more rules assigning priorities to the HARQ feedback for the plurality of sidelink communications.

In a second aspect, alone or in combination with the first aspect, the one or more rules assign HARQ feedback that includes a negative acknowledgment a higher priority than HARQ feedback that includes an acknowledgment.

In a third aspect, alone or in combination with one or more of the first and second aspects, a quantity of the PSFCH transmissions included in each of the multiple candidate sets satisfies a threshold value.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, the threshold value is based at least in part on one or more of a capability associated with the UE, a configured value, or congestion on one or more of the PSFCH, a PSSCH, or a PSCCH.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the at least one candidate set that has the highest value for the utility parameter is randomly selected from at least two candidate sets for which respective utility parameters are equal in value.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the one or more candidate sets that satisfy the PSFCH transmit power constraint are identified based at least in part on respective link budget requirements for individual PSFCH transmissions in each of the multiple candidate sets.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the plurality of sidelink communications are received from the one or more other UEs over one or more of a PSSCH or a PSCCH, and the link budget requirements for the individual PSFCH transmissions are based at least in part on an RSRP measurement associated with one or more of the PSSCH or the PSCCH.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the link budget requirement for an individual PSFCH transmission decreases as a corresponding RSRP measurement increases.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, the link budget requirement for at least one individual PSFCH transmission is based at least in part on an average RSRP measurement for multiple sidelink communications from a particular UE.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, process <NUM> further includes determining the link budget requirement for an individual PSFCH transmission based at least in part on a transmit power allocated to the individual PSFCH transmission, an attenuation associated with one of the plurality of sidelink communications corresponding to the individual PSFCH transmission, a noise within a transmission bandwidth associated with the individual PSFCH transmission, and a signal-to-noise ratio to decode the individual PSFCH transmission.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, the attenuation associated with the sidelink communication corresponding to the individual PSFCH transmission is based at least in part on an original transmission power associated with the sidelink communication and an RSRP measurement associated with the sidelink communication.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, the PSFCH transmit power constraint is a power backoff based at least in part on one or more of an MPR value or an A-MPR value to be added to the MPR value.

In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, process <NUM> further includes determining a total available transmit power to use in the HARQ feedback occasion based at least in part on the power backoff, and determining that the one or more candidate sets satisfy the PSFCH transmit power constraint based at least in part on the total available transmit power to use in the HARQ feedback occasion equaling or exceeding a sum of transmission powers allocated to the plurality of PSFCH transmissions included in the one or more candidate sets.

In a fourteenth aspect, alone or in combination with one or more of the first through thirteenth aspects, process <NUM> further includes applying one or more power sharing rules to allocate the total available transmit power to use in the HARQ feedback occasion among the plurality of PSFCH transmissions that are transmitted in the HARQ feedback occasion.

In a fifteenth aspect, alone or in combination with one or more of the first through fourteenth aspects, the one or more power sharing rules include equally dividing the total available transmit power among the plurality of PSFCH transmissions transmitted in the HARQ feedback occasion.

In a sixteenth aspect, alone or in combination with one or more of the first through fifteenth aspects, the one or more power sharing rules include equally dividing the total available transmit power among a subset of RBs used to transmit the plurality of PSFCH transmissions in the HARQ feedback occasion, and further equally dividing a portion of the total available transmit power allocated to a particular RB among a portion of the plurality of PSFCH transmissions that share the particular RB.

In a seventeenth aspect, alone or in combination with one or more of the first through sixteenth aspects, the one or more power sharing rules include equally dividing the total available transmit power among a subset of RBs used to transmit the plurality of PSFCH transmissions in the HARQ feedback occasion, and further dividing a portion of the total available transmit power allocated to a particular RB among a portion of the plurality of PSFCH transmissions that share the particular RB based at least in part on one or more of a priority or an estimated link budget requirement associated with the portion of the PSFCH transmissions that share the particular RB.

In a eighteenth aspect, alone or in combination with one or more of the first through seventeenth aspects, the one or more power sharing rules include allocating the total available transmit power to the plurality of PSFCH transmissions transmitted in the HARQ feedback occasion based at least in part on respective link budget requirements for each individual PSFCH transmission according to a descending priority until the total available transmit power is exhausted.

In an nineteenth aspect, alone or in combination with one or more of the first through eighteenth aspects, process <NUM> further includes generating, for each of the one or more candidate sets that satisfy the PSFCH transmit power constraint, a bitmap in which each individual bit corresponds to an individual PSFCH transmission, and assigning a utility value to each individual bit in the bitmap, where the respective utility parameters associated with the one or more candidate sets are based at least in part on a combination of the utility values assigned to the individual bits in the bitmaps associated with each respective candidate set.

In a twentieth aspect, alone or in combination with one or more of the first through nineteenth aspects, each individual bit is set to a first value if a link budget requirement for the corresponding individual PSFCH transmission is satisfied or to a second value if a link budget requirement for a corresponding individual PSFCH transmission is not satisfied.

In a twenty-first aspect, alone or in combination with one or more of the first through twentieth aspects, the utility value assigned to each individual bit set to the first value is based at least in part on one or more of a priority associated with the corresponding individual PSFCH transmission, a distance between the UE and a receiver of the corresponding individual PSFCH transmission, an RSRP between the UE and the receiver of the corresponding individual PSFCH transmission, a remaining delay budget for one of the plurality of sidelink communications associated with the corresponding individual PSFCH transmission, a packet reception rate associated with sidelink communications between the UE and the receiver of the corresponding individual PSFCH transmission, or a bit rate associated with the sidelink communications between the UE and the receiver of the corresponding individual PSFCH transmission.

In a twenty-second aspect, alone or in combination with one or more of the first through twenty-first aspects, the utility value assigned to each individual bit set to the second value is based at least in part on one or more of a potential of a corresponding individual PSFCH transmission creating harmful interference to other PSFCH transmissions, or a multicast configuration associated with the corresponding individual PSFCH transmission.

<FIG> is a block diagram of an example apparatus <NUM> for wireless communication. The apparatus <NUM> may be a UE, or a UE may include the apparatus <NUM>. In some aspects, the apparatus <NUM> includes a reception component <NUM> and a transmission component <NUM>, 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 apparatus <NUM> may communicate with another apparatus <NUM> (such as a UE, a base station, or another wireless communication device) using the reception component <NUM> and the transmission component <NUM>. As further shown, the apparatus <NUM> may include one or more of an identification component <NUM> or a selection component <NUM>, among other examples.

In some aspects, the apparatus <NUM> may be configured to perform one or more operations described herein in connection with <FIG>. Additionally or alternatively, the apparatus <NUM> may be configured to perform one or more processes described herein, such as process <NUM> of <FIG>. In some aspects, the apparatus <NUM> and/or one or more components shown in <FIG> may include one or more components of the UE described above in connection with <FIG>. Additionally, or alternatively, one or more components shown in <FIG> may be implemented within one or more components described above in connection with <FIG>. Additionally or alternatively, one or more components of the set of components may be implemented at least in part as software stored in a memory. For example, a component (or a portion of a component) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by a controller or a processor to perform the functions or operations of the component.

The identification component <NUM> may identify multiple candidate sets of PSFCH transmissions, wherein the multiple candidate sets each include a plurality of PSFCH transmissions to provide HARQ feedback for a plurality of sidelink communications received from one or more other UEs. In some aspects, the identification component <NUM> may include a controller/processor, a memory, or a combination thereof, of the UE described above in connection with <FIG>. The identification component <NUM> may identify, from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets. The selection component <NUM> may select, from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set that has a highest value for a utility parameter among utility parameters associated with each of the one or more candidate sets. In some aspects, the selection component <NUM> may include a controller/processor, a memory, or a combination thereof, of the UE described above in connection with <FIG>. The transmission component <NUM> may transmit, on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a HARQ feedback occasion.

Claim 1:
A method (<NUM>) of wireless communication performed by a user equipment, UE, comprising:
identifying (<NUM>) multiple candidate sets of physical sidelink feedback channel, PSFCH transmissions, wherein the multiple candidate sets each include a plurality of PSFCH transmissions to provide hybrid automatic repeat request, HARQ feedback for a plurality of sidelink communications received from one or more other UEs;
characterized in that the method further comprises
identifying (<NUM>), from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets;
selecting (<NUM>), from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set by applying a utility function to the individual PSFCH transmissions in each candidate set; and
transmitting (<NUM>), on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a next HARQ feedback occasion.