Techniques for configuring multiple frequency domain opportunities for sidelink feedback

Methods, systems, and devices for wireless communications are described. In some systems, a user equipment (UE) may receive a configuration of a set of feedback channel occasions corresponding to a first sidelink data channel in a first listen-before-talk (LBT) sub-band, the set of feedback channel occasions located over multiple LBT sub-bands of an unlicensed radio frequency spectrum band. The UE may receive a data transmission over the first sidelink data channel and may determine to transmit feedback associated with the data transmission. The UE, based on the configuration of the set of feedback channel occasions, may perform LBT for each of the set of feedback channel occasions to determine which of the set of feedback channel occasions are available to the UE for transmitting the feedback associated with the data transmission. The UE may transmit feedback over one or more of the set of feedback channel occasions accordingly.

FIELD OF DISCLOSURE

The following relates to wireless communications, including techniques for configuring multiple frequency domain opportunities for sidelink feedback.

BACKGROUND

In some wireless communications systems, two or more UEs may communicate with each other over a sidelink channel. In some cases, a first UE may transmit a sidelink transmission to a second UE with feedback requested, and the second UE may transmit feedback to the first UE accordingly.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support techniques for configuring multiple frequency domain opportunities for sidelink feedback. In some examples, a first user equipment (UE) and a second UE may communicate over a sidelink channel, such as a sidelink data channel. The first UE may transmit data to the second UE over a first sub-band of the sidelink data channel and, in some examples, the second UE may transmit feedback (such as hybrid automatic repeat request (HARQ) feedback) to the first UE indicating whether the second UE was able to successfully receive the sidelink transmission. For instance, in examples in which the second UE successfully receives the sidelink transmission, the second UE may transmit an acknowledgement (ACK) to the first UE. Alternatively, in examples in which the second UE unsuccessfully receives the sidelink transmission, the second UE may transmit a negative ACK (NACK) to the first UE.

In some implementations of the present disclosure, the second UE may receive a configuration of multiple opportunities or occasions over which the second UE may transmit feedback to the first UE and the multiple opportunities or occasions may be located in multiple sub-bands of an unlicensed radio frequency spectrum band. In some aspects, such opportunities or occasions may be referred to herein as feedback channel occasions, and may refer to a set of time and frequency resources of a physical sidelink feedback channel (PSFCH) such that they may be equivalently referred to as PSFCH opportunities or occasions. In some examples, the configuration may indicate a correspondence between the first sub-band over which the second UE receives the transmission from the first UE and the multiple feedback channel occasions. As such, the second UE may identify or otherwise determine the multiple feedback channel occasions based on receiving the transmission over the first sub-band and based on the correspondence indicated by the configuration. The second UE may perform a listen-before-talk (LBT) procedure for each of the multiple feedback channel occasions to determine which of the multiple feedback channel occasions are available (e.g., which feedback channel occasions pass LBT and are not being used by another device) and the second UE may transmit feedback to the second UE over one or more of the multiple feedback channel occasions based on the outcome of the LBT procedures.

In some examples, the configuration of the multiple feedback channel occasions may indicate multiple feedback channel pools. In such examples, the configuration may indicate a correspondence between the first sub-band and a first feedback channel pool, where the first feedback channel pool may include feedback channel occasions located in multiple different sub-bands. In some other examples, the configuration of the multiple feedback channel occasions may indicate one feedback channel pool. In such examples, the configuration may indicate an index of a second sub-band and an offset value between the first sub-band and the second sub-band, and the second UE may determine whether the multiple feedback channel occasions that correspond to the first sub-band include a feedback channel occasion located in the second sub-band based on whether the sidelink data channel in the second sub-band carries a unicast transmission and based on a formula for a sequence index.

A method for wireless communication at a UE is described. The method may include receiving a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band, performing a LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands, and transmitting feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band, perform a LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands, and transmit feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for receiving a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band, means for performing a LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands, and means for transmitting feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to receive a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band, perform a LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands, and transmit feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a control message including a configuration of the set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, where performing the LBT for each of the set of multiple feedback channel occasions may be based on the configuration of the set of multiple feedback channel occasions.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the control message including the configuration of the set of multiple feedback channel occasions may include operations, features, means, or instructions for receiving the control message including the configuration indicating a set of multiple feedback channel pools, each of the set of multiple feedback channel pools corresponding to one sub-band of the unlicensed radio frequency spectrum band, where the set of multiple feedback channel occasions includes one feedback channel pool of the set of multiple feedback channel pools.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration indicating the set of multiple feedback channel pools includes a set of multiple bit vectors, each bit vector indicating a different one of the set of multiple feedback channel pools.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of multiple feedback channel occasions may be associated with groupcast feedback and the method, apparatuses, and non-transitory computer-readable medium may include further operations, features, means, or instructions for determining that a group member identifier (ID) of the UE may be less than a product of a quantity of physical resource blocks (PRBs) of a feedback channel occasion of the set of multiple feedback channel occasions and a cyclic shift value associated with the feedback channel occasion and including the feedback channel occasion in the set of multiple feedback channel occasions based on determining that the group member ID of the UE may be less than the product of the quantity of PRBs and the cyclic shift value.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of multiple feedback channel occasions may be associated with groupcast feedback and the method, apparatuses, and non-transitory computer-readable medium may include further operations, features, means, or instructions for determining that a quantity of UEs providing the groupcast feedback may be less than a product of a quantity of PRBs of a feedback channel occasion of the set of multiple feedback channel occasions and a cyclic shift value associated with the feedback channel occasion and including the feedback channel occasion in the set of multiple feedback channel occasions based on determining that the quantity of UEs providing the groupcast feedback may be less than the product of the quantity of PRBs and the cyclic shift value.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of multiple feedback channel occasions may be associated with groupcast feedback and the method, apparatuses, and non-transitory computer-readable medium may include further operations, features, means, or instructions for identifying that the set of multiple feedback channel occasions includes a first feedback channel occasion in the first sub-band and a second feedback channel occasion in a second sub-band, determining that a first product of a first quantity of PRBs of the first feedback channel occasion and a first cyclic shift value associated with the first feedback channel occasion may be less than a second product of a second quantity of PRBs of the second feedback channel occasion and a second cyclic shift value associated with the second feedback channel occasion, and including the first feedback channel occasion and the second feedback channel occasion in the set of multiple feedback channel occasions based on determining that the first product may be less than the second product.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the control message including the configuration of the set of multiple feedback channel occasions may include operations, features, means, or instructions for receiving the control message including the configuration indicating an index associated with a second sub-band and an offset value between the first sub-band and the second sub-band, where the set of multiple feedback channel occasions include a first feedback channel occasion located in the first sub-band and a second feedback channel occasion located in the second sub-band.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the transmission may be a unicast transmission and the method, apparatuses, and non-transitory computer-readable medium may include further operations, features, means, or instructions for detecting a second unicast transmission over a second sidelink data channel in the second sub-band based on the index associated with the second sub-band and selecting the first feedback channel occasion and the second feedback channel occasion as two of the set of multiple feedback channel occasions based on detecting the second unicast transmission in the second sub-band and a formula.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the formula includes a first product of a summation of an ID associated with a transmitting UE from which the transmission may be received and the offset value between the first sub-band and the second sub-band and a modulo operation of a second product of a quantity of PRBs of the first feedback channel occasion and a cyclic shift value associated with the first feedback channel occasion.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions may include operations, features, means, or instructions for transmitting the feedback over each feedback channel occasion of the set of multiple feedback channel occasions that may be associated with a successful LBT and that may be located in an earliest symbol period including a feedback channel occasion.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a configuration indicating a primary feedback channel occasion and one or more secondary feedback channel occasions of the set of multiple feedback channel occasions, where transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions may include operations, features, means, or instructions for transmitting the feedback over the primary feedback channel occasion or over any of the one or more secondary feedback channel occasions based on whether the primary feedback channel occasion may be associated with a successful LBT.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a configuration indicating a priority of the set of multiple feedback channel occasions, where transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions may include operations, features, means, or instructions for transmitting the feedback over a feedback channel occasion of the set of multiple feedback channel occasions that may have a highest priority and that may be associated with a successful LBT.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions may include operations, features, means, or instructions for transmitting the feedback over each feedback channel occasion of the set of multiple feedback channel occasions that may be associated with a successful LBT.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions may include operations, features, means, or instructions for transmitting the feedback over a first feedback channel occasion within a same channel occupancy time (COT) of the transmission based on a cyclic prefix extension.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that a priority of the transmission satisfies a threshold priority, that the first feedback channel occasion may be an only feedback channel occasion that satisfies a packet delay budget of the transmission, that the first feedback channel occasion may be in a last symbol period including a feedback channel occasion, that previous cyclic prefix extensions may have occurred below a threshold amount, that the first feedback channel occasion may be configured for transmitting the feedback within the same COT, or any combination thereof, where transmitting the feedback over the first feedback channel occasion within the same COT of the transmission may be based on the determining.

A method for wireless communication at a UE is described. The method may include transmitting a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band, transmitting a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band, and receiving feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on a LBT for each of the set of multiple feedback channel occasions.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to transmit a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band, transmit a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band, and receive feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on a LBT for each of the set of multiple feedback channel occasions.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for transmitting a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band, means for transmitting a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band, and means for receiving feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on a LBT for each of the set of multiple feedback channel occasions.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to transmit a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band, transmit a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band, and receive feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on a LBT for each of the set of multiple feedback channel occasions.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the control message including the configuration of the set of multiple feedback channel occasions may include operations, features, means, or instructions for transmitting the control message including the configuration indicating a set of multiple feedback channel pools, each of the set of multiple feedback channel pools corresponding to one sub-band of the unlicensed radio frequency spectrum band, where the set of multiple feedback channel occasions includes one feedback channel pool of the set of multiple feedback channel pools.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration indicating the set of multiple feedback channel pools includes a set of multiple bit vectors, each bit vector indicating a different one of the set of multiple feedback channel pools.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the control message including the configuration of the set of multiple feedback channel occasions may include operations, features, means, or instructions for transmitting the control message including the configuration indicating an index associated with a second sub-band and an offset value between the first sub-band and the second sub-band, where the set of multiple feedback channel occasions include a first feedback channel occasion located in the first sub-band and a second feedback channel occasion located in the second sub-band.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions may include operations, features, means, or instructions for receiving the feedback over each feedback channel occasion of the set of multiple feedback channel occasions that may be associated with a successful LBT and that may be located in an earliest symbol period including a feedback channel occasion.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting the control message includes transmitting the configuration indicating a primary feedback channel occasion and one or more secondary feedback channel occasions of the set of multiple feedback channel occasions and receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions includes receiving the feedback over the primary feedback channel occasion or over any of the one or more secondary feedback channel occasions based on whether the primary feedback channel occasion may be associated with a successful LBT.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting the control message includes transmitting the configuration indicating a priority of the set of multiple feedback channel occasions and receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions includes receiving the feedback over a feedback channel occasion of the set of multiple feedback channel occasions that may have a highest priority and that may be associated with a successful LBT.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions may include operations, features, means, or instructions for receiving the feedback over each feedback channel occasion of the set of multiple feedback channel occasions that may be associated with a successful LBT.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions may include operations, features, means, or instructions for receiving the feedback over a first feedback channel occasion within a same COT of the transmission based on a cyclic prefix extension.

DETAILED DESCRIPTION

In some wireless communications systems, two or more user equipment (UEs) may communicate with each other via one or more sidelink channels. For example, a first UE may transmit to a second UE over a sidelink data channel, such as a physical sidelink shared channel (PSSCH), and, in some cases, the second UE may transmit feedback to the first UE responsive to the transmission over the sidelink data channel over a sidelink feedback channel, such as a physical sidelink feedback channel (PSFCH). In some cases, the second UE may provide the feedback, which may include hybrid automatic repeat request (HARQ) feedback, to the first UE responsive to the transmission over the sidelink data channel to support higher reliability of sidelink communication between the first UE and the second UE. For instance, based on receiving feedback indicating whether or not the second UE successfully received the transmission from the first UE, the first UE may determine whether or not to send a re-transmission to the second UE.

In some cases, a set of PSFCH resources (e.g., a PSFCH opportunity) over which the second UE may transmit the feedback to the first UE may be pre-determined or pre-configured based on a mapping or an assignment between the PSSCH resources over which the first UE transmits to the second UE and PSFCH resources. In other words, each PSSCH resource may be associated with a unique PSFCH opportunity. In some cases, the second UE may transmit the feedback over the PSFCH opportunity associated with the PSSCH over which the first UE transmits to the second UE without contention or competition from other devices (e.g., other UEs also transmitting feedback). In some other cases, however, the PSFCH opportunity over which the second UE may transmit the feedback to the first UE may be part of an unlicensed radio frequency spectrum band and, as such, the second UE may perform listen-before-talk (LBT), such as an LBT procedure or a channel access procedure, prior to getting access to the PSFCH opportunity (and likewise prior to transmitting the feedback). In some examples, such as in examples in which there is high channel volume or traffic, LBT may have a relatively high likelihood of failure and, if LBT failure does occur, the second UE may be unable to transmit the feedback to the first UE over the associated PSFCH opportunity. As such, the first device may assume that the second device failed to receive the transmission and may transmit a re-transmission to the second UE, which may be unnecessary (e.g., the second UE may have failed to provide the feedback based on an LBT failure rather than a reception failure).

In some implementations of the present disclosure, the second UE may receive a configuration of multiple PSFCH opportunities over multiple sub-bands for transmitting feedback responsive to a transmission over a PSSCH over a sub-band. In some aspects, such different sub-bands may refer to different LBT sub-bands (e.g., a sub-band or frequency range over which a UE may perform LBT). Such a configuration of multiple PSFCH opportunities for a PSSCH or an LBT sub-band may increase the likelihood for at least one of the multiple PSFCH opportunities to be available (e.g., pass LBT) and the second UE may likewise have a greater likelihood to transmit the feedback to the first UE. For example, the configuration may indicate that a PSSCH of a first LBT sub-band is configured for multiple PSFCH opportunities including a first PSFCH opportunity in the first LBT sub-band and a second PSFCH opportunity in a second LBT sub-band different from the first LBT sub-band. In such examples, if the second UE receives a transmission from the first UE over the PSSCH of the first sub-band, the second UE may perform LBT for each of the first PSFCH opportunity in the first LBT sub-band and the second PSFCH opportunity in the second LBT sub-band and may transmit feedback to the first UE over the first PSFCH opportunity or the second PSFCH opportunity, or both, depending on the respective outcomes of the LBT procedures.

Aspects of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. The described techniques may be implemented to support more reliable transmission of HARQ feedback associated with sidelink communication over an unlicensed radio frequency spectrum band. For example, based on receiving a configuration of multiple PSFCH opportunities over which the second UE may transmit feedback to the first UE responsive to a transmission over an associated PSSCH or LBT sub-band, the likelihood for at least one of the multiple PSFCH opportunities to pass LBT may increase based on the separation of the multiple PSFCH opportunities in different LBT sub-bands. Based on the greater likelihood of at least one of the multiple PSFCH opportunities to pass LBT, the second UE may likewise have a greater likelihood of transmitting feedback to the first UE. As such, the first UE may more accurately determine whether the transmission was successfully received at the second UE and the first UE may avoid potentially unnecessary re-transmissions to the second UE. Accordingly, the first UE and the second UE may experience greater spectral efficiency, higher data rates, and increased capacity, among other benefits.

Aspects of the disclosure are initially described in the context of wireless communications systems. Aspects of the disclosure are additionally illustrated by and described with reference to resource configurations and a process flow. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to techniques for configuring multiple frequency domain opportunities for sidelink feedback.

The wireless communications system100may support sidelink communications between two or more UEs115over a communication link135. For example, a first UE115may transmit to a second UE115over a sidelink data channel, such as a PSSCH. In some cases, the second UE115may transmit feedback to the first UE115responsive to the transmission over the sidelink data channel over a sidelink feedback channel, such as a PSFCH. Such transmission of feedback, which may include HARQ acknowledgement (ACK) or negative ACK (NACK) feedback, responsive to the transmission over the sidelink data channel may support higher reliability of sidelink communication between the first UE115and the second UE115. For instance, based on receiving feedback indicating whether or not the second UE115successfully received the transmission from the first UE115, the first UE115may determine whether or not to send a re-transmission to the second UE115.

In some cases, the second UE115may transmit feedback over a PSFCH opportunity (e.g., a set of time and frequency resources of a PSFCH) responsive to the transmission from the first UE115according to a mapping or an assignment between the PSSCH over which the first UE115transmitted to the second UE115and the PSFCH opportunity. In other words, each PSSCH resource may be associated with a unique PSFCH opportunity (e.g., there is a one-to-one mapping between a PSSCH resource and a corresponding PSFCH opportunity). In such cases, the second UE115may transmit the feedback over the PSFCH opportunity corresponding to the PSSCH over which the first UE115transmits to the second UE115without contention or competition from other devices (e.g., other UEs115also transmitting feedback). Accordingly, such a mapping or an assignment between a PSSCH and a PSFCH opportunity may be configured within a licensed radio frequency spectrum band. In some other cases, however, the PSFCH opportunity over which the second UE115may transmit the feedback to the first UE115may be part of an unlicensed radio frequency spectrum band and, as such, the second UE115may perform LBT, such as an LBT procedure or a channel access procedure, prior to getting access to the PSFCH opportunity (and likewise prior to transmitting the feedback to the first UE115).

In some examples, such as in examples in which there is high channel volume or traffic, LBT may have a relatively high likelihood of failure and, if LBT failure does occur, the second UE115may be unable to transmit the feedback to the first UE115over the PSFCH opportunity corresponding to the PSSCH over which the first UE115transmits to the second UE115. In examples in which LBT failure does occur, the first UE115, upon failing to receive feedback from the second UE115, may determine or otherwise assume that the second UE115failed to successfully receive the transmission over the PSSCH and the first UE115may transmit a re-transmission to the second UE115. In examples in which the second UE115was able to successfully receive the transmission, but unable to transmit the feedback due to an LBT failure, such a re-transmission may be unnecessary. Additionally, in examples in which the second UE115experiences continuous (e.g., multiple, or greater than a threshold number) of LBT failures for sending feedback to the first UE115, the first UE115or the second UE115, or both, may declare or otherwise trigger radio link failure (RLF), which may result in a loss of connectivity between the first UE115and the second UE115.

In some implementations of the present disclosure, the second UE115may receive a configuration of multiple PSFCH opportunities over multiple LBT sub-bands for transmitting feedback responsive to a transmission over a PSSCH in an LBT sub-band. Such a configuration of multiple PSFCH opportunities over multiple sub-bands for a PSSCH or an LBT sub-band may increase the likelihood for at least one of the multiple PSFCH opportunities to be available for carrying feedback from the second UE115to the first UE115. For example, the configuration may indicate that a PSSCH of a first sub-band is configured for multiple PSFCH opportunities including a first PSFCH opportunity in the first LBT sub-band and a second PSFCH opportunity in a second LBT sub-band different from the first LBT sub-band. In such examples, if the second UE115receives a transmission from the first UE115over the PSSCH of the first sub-band, the second UE115may perform LBT for each of the first PSFCH opportunity in the first LBT sub-band and the second PSFCH opportunity in the second LBT sub-band and may transmit feedback to the first UE115over the first PSFCH opportunity or the second PSFCH opportunity, or both, depending on the respective outcomes of the LBT procedures.

FIG.2illustrates an example of a wireless communications system200that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. The wireless communications system200illustrates communication between a UE115-aand a UE115-b, which may be examples of corresponding devices described herein, including UEs115as described with reference toFIG.1. In some aspects, the UE115-aand the UE115-bmay communicate within a geographic coverage area110-aand communicate with each other via a communication link205and a communication link210. In some implementations, the UE115-bmay receive a configuration of multiple PSFCH opportunities225over multiple LBT sub-bands230corresponding to a PSSCH or an LBT sub-band including the PSSCH for transmitting feedback220responsive to a data transmission215over the PSSCH.

The wireless communications system200, which may be an example of an NR system supporting NR sidelink communication, such as V2X communication, may support the transmission of feedback (such as HARQ feedback) over a PSFCH for higher reliability for both unicast and groupcast transmissions. For example, the UE115-aor the UE115-b, or both, may transmit a HARQ response (such as an ACK or a NACK) over a PSFCH opportunity225responsive to sidelink communication between the UE115-aand the UE115-b, and the PSFCH may be arranged or otherwise configured as a global resource pool with pre-determined (e.g., pre-configured) mappings or assignments. In other words, in some cases, there may be a unique PSFCH opportunity225for one PSSCH. Such examples in which there may be a unique PSFCH opportunity225for one PSSCH may include examples of unicast HARQ response (such that one UE115receives a data transmission215and transmits feedback220responsive to the data transmission215) and examples of groupcast HARQ response option 2 (such that multiple UEs115receive a data transmission215and each transmit feedback220responsive to the data transmission215).

In such examples in which one PSFCH opportunity225is mapped or assigned to one PSSCH and in which the UE115-atransmits a data transmission215to the UE115-bover a PSSCH, the UE115-bmay determine the PSFCH opportunity225that is mapped or assigned to the PSSCH over which the UE115-atransmits the data transmission215, and the UE115-bmay transmit feedback220responsive to the data transmission215over the PSFCH opportunity225accordingly. In some cases, such a mapping or assignment may be pre-configured for each PSSCH resource over which a UE115may transmit. As such, the UE115-bmay transmit feedback220to the UE115-ain a contention-free manner (e.g., without competition from other UEs115). In other words, the UE115-aand the UE115-bmay communicate over a licensed radio frequency spectrum band or an ITS radio frequency spectrum band.

For example, each PSSCH over which the UE115-aor the UE115-bmay transmit may be mapped to a different PSFCH opportunity225, and each different PSFCH opportunity225may correspond to a different set of physical resource blocks (PRBs) in a symbol period, such as a PSFCH symbol period. In some cases, each set of PRBs in the PSFCH symbol period may include a quantity of Z PRBs (and Z may be configurable). In some aspects, a sidelink data channel may include a number of discrete PSSCHs (e.g., discrete sets of resources within a PSSCH) over which a UE115may transmit and the number of PSSCHs may be located in different time or frequency resources. For example, a sidelink data channel may include N PSSCHs over an interval in time and S PSSCHs over a range in frequency. As such, a PSFCH resource pool (which may include a number of PSFCH opportunities225) may include NF=Z*S*N PRBs. In some cases, the NFPRBs of the PSFCH resource pool may be indicated (to the UE115-aor the UE115-b, or both) by a PRB-level bit-map via control signaling, such as layer 3 (L3) signaling. In some aspects, N=2.

Each PSFCH opportunity225(e.g., each Z-PRB) may carry Z*Y PSFCH sequences, where Y is a cyclic shift value of the PSFCH opportunity225and may be a value in the set of numbers {1, 2, 3, 4, 6} representing the number of cyclic shifts (e.g., a dimension in the code-domain) that the UE115-bmay use for transmitting over the PSFCH opportunity225. The UE115-b(e.g., the receiver UE) may choose or select a sequence with an index of (K+M)mod(Z*Y) for transmitting over one of the Z PRBs corresponding to the (leading) sub-channel of the PSSCH. In some cases, K is the transmitting UE ID (e.g., and may be 8 bits) in PSSCH. For instance, K may refer to the UE ID of the UE115-a. M may vary depending on whether the PSSCH carries a unicast transmission or a groupcast transmission. For instance, in examples in which the PSSCH carries a unicast transmission, M is set to 0. Alternatively, in examples in which the PSSCH carries a groupcast transmission (e.g., a groupcast transmission requesting groupcast HARQ response option 2), M is set to a group ID which may be a number in the range of numbers {0, 1, . . . , X−1} where X is equal to a quantity of UEs115receiving the groupcast transmission and requested for groupcast HARQ. In some cases, groupcast HARQ response option 2 is not used for X>Z*Y.

In some cases, however, a licensed radio frequency spectrum band or an ITS radio frequency spectrum band may be unavailable (or not guaranteed) in some regions. For example, the wireless communications system200may not always or everywhere support the use of licensed radio frequency spectrum bands and, in some cases, the UE115-aand the UE115-bmay communicate over an unlicensed radio frequency spectrum band. In such cases in which the UE115-aand the UE115-bcommunicate over an unlicensed radio frequency spectrum band, the UE115-aand the UE115-bmay perform LBT (e.g., an LBT procedure or a channel access procedure) prior to transmitting to support coexistence with other radio access technologies (RATs). In some aspects, the UE115-aand the UE115-bmay perform LBT by regulation in some 5 GHz unlicensed radio frequency spectrum bands (e.g., in some of the most relevant 5 GHz unlicensed radio frequency spectrum bands).

In such cases in which the UE115-aand the UE115-bcommunicate over an unlicensed radio frequency spectrum band and perform LBT prior to transmitting, the UE115-bmay perform LBT prior to transmitting feedback220(e.g., a HARQ response) over the PSFCH opportunity225corresponding to the PSSCH over which the UE115-atransmits the data transmission215. In some cases, however, the PSFCH opportunity225(e.g., a unique PSFCH opportunity for the PSSCH carrying the data transmission215) may be occupied or otherwise unavailable such that the LBT for the PSFCH opportunity225may fail. As such, the UE115-bmay be unable to get channel access for the PSFCH opportunity225and may likewise be unable to transmit the feedback220to the UE115-aover the PSFCH opportunity225. The UE115-a, failing to receive the feedback220from the UE115-bover the PSFCH opportunity225corresponding to (e.g., mapped or assigned to) the PSSCH carrying the data transmission215, may determine or otherwise assume that the UE115-bfailed to successfully receive the data transmission215. The UE115-amay accordingly re-transmit the data transmission215to the UE115-bover a second PSSCH, which may be unnecessary in cases in which the UE115-bsuccessfully received the initial data transmission215and experienced an LBT failure when attempting to transmit the associated feedback220. Such unnecessary re-transmission may result in poor spectral efficiency, increased interference, higher processing costs, or a combination thereof.

The UE115-b, based on receiving the re-transmission of the data transmission215over the second PSSCH, may identify a second PSFCH opportunity225corresponding to the second PSSCH and perform a second LBT procedure on the second PSFCH opportunity225prior to transmitting the feedback220to the UE115-a. In some cases, however, the second LBT procedure may fail and the UE115-bmay again refrain from transmitting the feedback220associated with the data transmission215to the UE115-a. In cases of continuous LBT failure (and likewise continuous failures for sending a HARQ response), the UE115-aor the UE115-b, or both, may declare RLF. In other words, continuous failure to send feedback220to the UE115-aresponsive to the data transmission215may trigger or otherwise result in an RLF event.

In some implementations of the present disclosure, the UE115-bmay receive a configuration of multiple PSFCH opportunities225, such as a PSFCH opportunity225-a, a PSFCH opportunity225-b, and a PSFCH opportunity225-c, over multiple LBT sub-bands230, such as over an LBT sub-band230-aand an LBT sub-band230-b, for a PSSCH or an LBT sub-band carrying the PSSCH. In other words, one PSSCH over which the UE115-amay transmit the data transmission215to the UE115-b(and that requests HARQ response) may correspond to multiple PSFCH opportunities225over multiple LBT sub-bands230over which the UE115-bmay potentially transmit the feedback220associated with the data transmission215. Additionally, in some implementations, the multiple PSFCH opportunities225may be configured over multiple time periods, such as in multiple slots or in multiple PSFCH symbols (as illustrated by and described in more detail with reference toFIG.3).

For example, the UE115-amay transmit the data transmission215over a PSSCH that corresponds to multiple PSFCH opportunities225including the PSFCH opportunity225-alocated in the LBT sub-band230-aand in a first PSFCH symbol, the PSFCH opportunity225-blocated in the LBT sub-band230-band in the first PSFCH symbol, and the PSFCH opportunity225-clocated in the LBT sub-band230-band in a second PSFCH symbol. As such, the UE115-bmay perform an LBT procedure for each of the PSFCH opportunities225to determine which of the multiple PSFCH opportunities225are available (e.g., which of the multiple PSFCH opportunities225pass LBT). In some examples, the UE115-amay determine that one or more of the multiple PSFCH opportunities225are available (e.g., pass LBT) and may transmit the feedback220associated with the data transmission215over at least one of the one or more PSFCH opportunities225that are available.

The UE115-bmay implement various techniques to determine over which PSFCH opportunities225of the available PSFCH opportunities225to transmit the feedback220, and the UE115-bmay follow one or more of the various techniques based on a pre-configuration, a UE decision, or control signaling. For example, depending on the implementation or configuration at the UE115-b, the UE115-bmay transmit over all available PSFCH opportunities225or a subset of the available PSFCH opportunities225. Additional details relating to over which of the available PSFCH opportunities225the UE115-bmay transmit are described herein, including with reference toFIG.3.

In some aspects, an LBT sub-band230may refer to or include a bandwidth (in frequency) over which the UE115-bmay conduct LBT. For instance, in examples in which the UE115-aand the UE115-bcommunicate over the 5 GHz unlicensed radio frequency spectrum band, an LBT sub-band230may refer to or include a 20 MHz frequency range. Alternatively, in some other examples (such as in examples supporting coexistence with dedicated short-range communication (DSRC) technology), an LBT sub-band230may refer to or include a 10 MHz frequency range.

The UE115-bmay receive a control message including a configuration of the multiple PSFCH opportunities225. In some aspects, the UE115-bmay receive the control message from the UE115-avia higher layer signaling (e.g., L3 signaling) or sidelink control information (SCI). In some other aspects, the UE115-bmay receive the control message from a serving base station105(as described with reference toFIG.1) via higher layer signaling (e.g., L3 signaling). In some examples, the control message may configure multiple PSFCH resource pools (where each PSFCH resource pool may include multiple PSFCH opportunities225). For example, the control message may configure one PSFCH resource pool per LBT sub-band230. Additional details relating to how the control message may configure multiple PSFCH opportunities225over multiple PSFCH resource pools are described herein, including with reference toFIGS.4and5.

In some other examples, the control message may configure a single PSFCH resource pool. For example, the control message may configure one PSFCH resource pool for both the LBT sub-band230-aand the LBT sub-band230-b(such that the one PSFCH resource pool includes the PSFCH opportunity225-a, the PSFCH opportunity225-b, and the PSFCH opportunity225-c). In such examples, the control message may provide a one-PSSCH-to-multiple-PSFCH-opportunities mapping such that each of the multiple PSFCH opportunities225mapped to a PSSCH are distributed over different LBT sub-bands230(but within the same PSFCH resource pool). Additional details relating to how the control message may configure multiple PSFCH opportunities225within one PSFCH resource pool are described herein, including with reference toFIG.6.

In some implementations, the UE115-aand the UE115-bmay coordinate on which of the multiple PSFCH opportunities225the UE115-bmay use to transmit the feedback220via sidelink control signaling, such as SCI. For example, the UE115-amay transmit SCI to the UE115-bto control how the UE115-buses the multiple PSFCH opportunities225associated with the PSSCH over which the UE115-atransmits the data transmission215. In some examples, the UE115-amay transmit the SCI including a control field to dynamically pick or otherwise select a subset of the multiple PSFCH opportunities225applicable for the data transmission215(e.g., the multiple PSFCH opportunities225mapped or assigned to the PSSCH over which the UE115-atransmits the data transmission215). For example, the PSSCH over which the UE115-atransmits the data transmission215may be mapped or assigned to the PSFCH opportunity225-a, the PSFCH opportunity225-b, and the PSFCH opportunity225-c, and the UE115-amay sub-select one or more of the PSFCH opportunity225-a, the PSFCH opportunity225-b, or the PSFCH opportunity225-cvia the control field in the SCI. In such examples, the UE115-amay perform LBT for the PSFCH opportunities225that are sub-selected by the SCI or may otherwise refrain from transmitting the feedback220over PSFCH opportunities225that are not sub-selected by the SCI (e.g., the UE115-bmay transmit the feedback220over PSFCH opportunities225that are sub-selected by the SCI). Additional details relating to such a sub-selecting SCI control field are described herein, including with reference toFIG.3.

The wireless communications system200, based on supporting a one-to-many mapping between a PSSCH and PSFCH opportunities225over multiple LBT sub-bands230, may allow a receiving UE115, such as the UE115-b, to fill a gap (e.g., a time gap) between a PSSCH and a PSFCH with a cyclic prefix (CP) extension such that the receiving UE115may transmit feedback220within a same channel occupancy time (COT) of the PSSCH. For example, although such a CP extension to fill the time gap between a PSSCH and a PSFCH may cause LBT procedures for a PSFCH opportunity225within the PSFCH and in the same LBT sub-band as the CP extension to fail, the configuration of multiple PSFCH opportunities225for each PSSCH may provide sufficient opportunities for other, potentially blocked UEs115to still transmit feedback220. Additional details relating to such use of a CP extension to transmit feedback220within a system supporting multiple PSFCH opportunities225over multiple LBT sub-bands230are described herein, including with reference toFIG.7.

Additionally, the techniques of the present disclosure can be implemented with or without multiple time-domain PSFCH opportunities225(such as multiple time-domain PSFCH opportunities225via different HARQ timelines). Such different HARQ timelines may be defined such that one PSSCH has more than one PSFCH opportunity225in the time-domain. In some implementations, the multiple time-domain PSFCH opportunities225may be accommodated by configuring different PSFCH resource sets for different timelines. In some other implementations, the multiple time-domain PSFCH opportunities225may be accommodated by splitting a PSFCH resource set into static and orthogonal sub-sets. In such implementations, for example, odd indices may be configured for a first HARQ timeline and even indices may be configured for a second HARQ timeline.

As such, the UE115-bmay have a greater likelihood of successfully identifying an available PSFCH opportunity and likewise of transmitting the feedback220associated with the data transmission215to the UE115-a. Likewise, the UE115-amay have a greater likelihood of receiving the feedback220from the UE115-b, which may result in fewer potentially unnecessary re-transmissions of the data transmission215and reduce the likelihood of any of the UE115-aor the UE115-b, or both, declaring RLF. Accordingly, the UE115-aand the UE115-bmay achieve greater spectral efficiency, higher data rates, improve system capacity, and reduce interference.

FIG.3illustrates an example of a resource configuration300that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. The resource configuration300may be implemented to realize aspects of the wireless communications system100or the wireless communications system200. For example, a first UE115may transmit a data transmission to a second UE115, which may be examples of corresponding devices described herein, over a PSSCH310and the second UE115may transmit feedback associated with the data transmission to the first UE115over one or more of multiple PSFCH opportunities315in a PSFCH325corresponding to the PSSCH310. In some implementations, the second UE115may receive a control message including a configuration of the multiple PSFCH opportunities315corresponding to the PSSCH310and the second UE115may perform an LBT procedure for each of the multiple PSFCH opportunities315to determine which of the multiple PSFCH opportunities315are available for transmitting feedback.

For example, the second UE115may receive, from the first UE115or from a serving base station105, a control message configuring the multiple PSFCH opportunities315over multiple LBT sub-bands305for a PSSCH310over which the first UE115transmits data (e.g., data that may request feedback) to the second UE115. As shown inFIG.3, the second UE115may receive a configuration of four PSFCH opportunities315over two LBT sub-bands305and in two PSFCH symbols320. For instance, the control message may configure, for the PSSCH310, a PSFCH opportunity315-ain an LBT sub-band305-aand in a PSFCH symbol320-a, a PSFCH opportunity315-bin an LBT sub-band305-band in the PSFCH symbol320-a, a PSFCH opportunity315-cin the LBT sub-band305-aand in a PSFCH symbol320-b, and a PSFCH opportunity315-din the LBT sub-band305-band in the PSFCH symbol320-b. As such,FIG.3illustrates an example in which the multiple PSFCH opportunities315span multiple LBT sub-bands305and multiple PSFCH symbols320. Further, althoughFIG.3illustrates four PSFCH opportunities315(which may achieve up to four LBT diversity order), the second UE115may receive a configuration of any number of PSFCH opportunities315for the PSSCH310without exceeding the scope of the present disclosure.

In some implementations of the present disclosure, the second UE115, based on receiving a transmission from the first UE115over the PSSCH310, may perform LBT (e.g., an LBT procedure or a channel access procedure) for each of the multiple PSFCH opportunities315corresponding to the PSSCH310to determine which of the multiple PSFCH opportunities315are available for transmitting feedback associated with the transmission to the first UE115. In some examples, the second UE115may determine one or more available PSFCH opportunities315based on performing a successful LBT procedure for one or more of the multiple PSFCH opportunities315, and may transmit feedback to the first UE115over the one or more available PSFCH opportunities315.

In some examples, the second UE115may condition over which of the available PSFCH opportunities315the second UE115transmits feedback based on a pre-configuration, a UE decision, or control signaling. In some implementations, for instance, the second UE115(a HARQ responder) may transmit feedback over all of the available PSFCH opportunities315. In such implementations, the second UE115may employ power splitting (e.g., in examples in which two or more of the available PSFCH opportunities315occupy a same PSFCH symbol320). For example, if the PSFCH opportunity315-aand the PSFCH opportunity315-bboth pass LBT, the second UE115may employ power splitting to transmit feedback over both the PSFCH opportunity315-aand the PSFCH opportunity315-bsimultaneously (such that the second UE115avoids exceeding a power limit of the second UE115).

In some other implementations, the second UE115may transmit over all available PSFCH opportunities315that are located in an earliest PSFCH symbol320. In an example, if the PSFCH opportunity315-aand the PSFCH opportunity315-cpass LBT, the second UE115may transmit feedback over the PSFCH opportunity315-aand may refrain from transmitting feedback over the PSFCH opportunity315-c(e.g., because the PSFCH opportunity315-cis located in a later PSFCH symbol320-bthan the PSFCH symbol320-ain which the PSFCH opportunity315-ais located). Similarly, if the PSFCH opportunity315-a, the PSFCH opportunity315-b, and the PSFCH opportunity315-cpass LBT, the second UE115may transmit feedback over both of the PSFCH opportunity315-aand the PSFCH opportunity315-b, and may refrain from transmitting feedback over the PSFCH opportunity315-c(e.g., because the PSFCH opportunity315-cis located in a later PSFCH symbol320-bthan the PSFCH symbol320-ain which the PSFCH opportunity315-aand the PSFCH opportunity315-bare located).

In some other implementations, the second UE115may transmit feedback over a primary PSFCH opportunity if it is available, otherwise the second UE115may choose (e.g., randomly choose) to transmit feedback over one secondary PSFCH opportunity. In such implementations, the second UE115may receive a configuration indicating one of the multiple PSFCH opportunities315as the primary PSFCH opportunity and indicating a remainder of the multiple PSFCH opportunities315as secondary PSFCH opportunities. For instance, in examples in which the PSFCH opportunity315-ais configured as the primary PSFCH opportunity and in which the PSFCH opportunity315-aand the PSFCH opportunity315-b(which may be a secondary PSFCH opportunity) pass LBT, the second UE115may transmit feedback over the PSFCH opportunity315-aand may refrain from transmitting feedback over the PSFCH opportunity315-b.

Alternatively, in examples in which the PSFCH opportunity315-ais the primary PSFCH opportunity, in which the PSFCH opportunity315-afails LBT, and in which the PSFCH opportunity315-band the PSFCH opportunity315-c(which may both be secondary PSFCH opportunities) pass LBT, the second UE115may transmit feedback over one of the PSFCH opportunity315-bor the PSFCH opportunity315-c(e.g., randomly or based on a UE decision). In some aspects, the configuration indicating the primary and secondary PSFCH opportunities may be the same configuration that maps or assigns the multiple PSFCH opportunities315to the PSSCH310. In some other aspects, the configuration indicating the primary and secondary PSFCH opportunities may be a separate configuration.

In some other implementations, the second UE115may transmit feedback over a PSFCH opportunity315that is first in order of the available PSFCH opportunities315. In other words, the second UE115may transmit feedback over a PSFCH opportunity315that has a highest priority of the available PSFCH opportunities315that passed LBT. For example, the second UE115may receive a configuration indicating an order or a priority of the multiple PSFCH opportunities315and the second UE115may transmit feedback over the PSFCH opportunity315highest in the order (or that has the highest priority) of the available PSFCH opportunities315. For instance, in examples in which the PSFCH opportunity315-aand the PSFCH opportunity315-bpass LBT and in which the PSFCH opportunity315-ais higher in the order (or has a higher priority) than the PSFCH opportunity315-b, the second UE115may transmit feedback over the PSFCH opportunity315-aand refrain from transmitting feedback over the PSFCH opportunity315-b. In some aspects, the configuration indicating the order or priority of the PSFCH opportunities315may be the same configuration that maps or assigns the multiple PSFCH opportunities315to the PSSCH310. In some other aspects, the configuration indicating the order or the priority of the PSFCH opportunities315may be a separate configuration.

In some other implementations, the second UE115may select any one or more of the available PSFCH opportunities315. For example, the second UE115may randomly select any one or more of the available PSFCH opportunities315or may select any one or more of the available PSFCH opportunities315based on a UE decision. Further, although described in different implementations, the second UE115may use any combination of techniques for determining over which of the available PSFCH opportunities315to transmit feedback to the first UE115. In some aspects, the second UE115may receive a configuration, such as an RRC configuration or a configuration via SCI, to select any one or more of the techniques for determining over which of the available PSFCH opportunities315to transmit feedback to the first UE115.

In addition or as an alternative to conditioning over which of the available PSFCH opportunities315the second UE115transmits feedback based on a pre-configuration, a UE decision, or control signaling, the second UE115may receive, from the first UE115, SCI including a control field that may dynamically indicate a subset of multiple PSFCH opportunities315for which the second UE115may perform LBT or over which the second UE115may transmit feedback to the first UE115. In some examples, the control field of the SCI may indicate the subset of the PSFCH opportunities315(e.g., the PSFCH opportunities315that are L3 configured) based on indicating a time-domain subset of PSFCH opportunities315or a frequency-domain subset of PSFCH opportunities315, or a combination thereof. For instance, in examples in which the control field indicates a time-domain subset of PSFCH opportunities315, the SCI may sub-select PSFCH opportunities315within an indicated time-domain interval (such as PSFCH opportunities315within one or more PSFCH symbols320). Additionally or alternatively, in examples in which the control field indicates a frequency-domain subset of PSFCH opportunities315, the SCI may sub-select PSFCH opportunities315within an indicated frequency-domain range (such as PSFCH opportunities315within one or more LBT sub-bands305).

For instance, in examples in which the control field indicates a time-domain subset of PSFCH opportunities315, the control field may configure the second UE115to select PSFCH opportunities315within one or more PSFCH symbols320. Additionally or alternatively, in examples in which the control field indicates a frequency-domain subset of PSFCH opportunities315, the control field may configure the second UE115to select PSFCH opportunities315within one or more LBT sub-bands305. Further, the control field may select PSFCH opportunities315that fall within a time-domain subset and a frequency domain subset of PSFCH opportunities315. The control field of the SCI may include one or more bits, and the first UE115may construct the control field, and the second UE115may likewise interpret the control field, based on an RRC configuration. The RRC configuration may be signaled from the first UE115to the second UE115, or vice-versa, or may be signaled to the first UE115and the second UE115from a serving base station105. In some aspects, SCI may be referred to as layer 1 (L1) signaling. In some implementations, the control field may be constructed similarly to a physical uplink control channel (PUCCH) resource indicator (PRI) field in a Uu interface downlink grant.

As introduced with reference toFIG.2, the configuration of multiple PSFCH opportunities315corresponding to a PSSCH310may configure multiple PSFCH resource pools (e.g., one PSFCH resource pool per LBT sub-band305) or may configure a single PSFCH resource pool and introduce a one-PSSCH-to-multiple-PSFCH opportunities mapping such that the multiple PSFCH opportunities315corresponding to a PSSCH are distributed over multiple LBT sub-bands305. Additional details relating to the configuration of multiple PSFCH resource pools are described with reference toFIGS.4and5, and additional details relating to the configuration of one PSFCH resource pool, and the one-to-multiple mapping, are described with reference toFIG.6.

FIG.4illustrates an example of a resource configuration400that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. The resource configuration400may be implemented to realize aspects of the wireless communications system100or the wireless communications system200. For example, a first UE115may transmit a data transmission to a second UE115, which may be examples of corresponding devices described herein, over a PSSCH410and the second UE115may transmit feedback associated with the data transmission to the first UE115over one or more of multiple PSFCH opportunities415corresponding to the PSSCH410. In some implementations, the second UE115may receive a configuration of multiple PSFCH resource pools. In some aspects, the second UE115may receive the configuration of the multiple PSFCH resource pools via higher layer signaling, such as via L3 signaling.

In some cases of a single PSFCH resource pool, as described in more detail with reference withFIG.6, one PRB-level bit-map, together with Z and N (as described with reference toFIG.2), may be sufficient to mark or otherwise indicate the PRBs for the single PSFCH resource pool. In cases of multiple PSFCH resource pools, the configuration may define or otherwise include a per LBT sub-band description. In other words, the configuration may indicate a PRB-level bit vector for each different LBT sub-band that marks out the PRBs of each of the PSFCH opportunities415in the PSFCH resource pool corresponding to that LBT sub-band. For example, for an LBT sub-band405-aincluding a PSSCH410-a, the configuration may indicate a first PRB-level bit vector indicating PRBs of the PSFCH opportunity415-a, the PSFCH opportunity415-d, and the PSFCH opportunity415-fas the multiple PSFCH opportunities415over respective LBT sub-bands405(e.g., over the LBT sub-band405-a, an LBT sub-band405-b, and an LBT sub-band405-c). Similarly, for the LBT sub-band405-bincluding a PSSCH410-a, the configuration may indicate a second PRB-level bit vector indicating PRBs of the PSFCH opportunity415-cand the PSFCH opportunity415-g. Likewise, for the LBT sub-band405-cincluding a PSSCH410-c, the configuration may indicate a third PRB-level bit vector indicating PRBs of the PSFCH opportunity415-e.

As such, the configuration of the multiple PSFCH opportunities415may map or assign the LBT sub-band405-aor the PSSCH410-ato the PSFCH opportunity415-a, the PSFCH opportunity415-d, and the PSFCH opportunity415-f, may map or assign the LBT sub-band405-bor the PSSCH410-bto the PSFCH opportunity415-cand the PSFCH opportunity415-g, and may map or assign the LBT sub-band405-cor the PSSCH410-cto the PSFCH opportunity415-e(e.g., the LBT sub-band405-cor the PSSCH410-cmay have a single PSFCH opportunity415). Accordingly, in examples in which the second UE115receives the transmission from the first UE115over the PSSCH410-ain the LBT sub-band405-a, the second UE115may attempt to transmit feedback associated with the transmission over one or more of the PSFCH opportunity415-a, the PSFCH opportunity415-d, and the PSFCH opportunity415-f. Alternatively, in examples in which the second UE115receives the transmission from the first UE115over the PSSCH410-bin the LBT sub-band405-b, the second UE115may attempt to transmit feedback associated with the transmission over one or more of the PSFCH opportunity415-cand the PSFCH opportunity415-g. Alternatively, in examples in which the second UE115receives the transmission from the first UE115over the PSSCH410-cin the LBT sub-band405-c, the second UE115may attempt to transmit feedback associated with the transmission over the PSFCH opportunity415-e.

In some examples, some of the different PSFCH opportunities415may include different quantities of PRBs. For example, the PSFCH opportunity415-amay include Z PRBs, the PSFCH opportunity415-dmay include Z′ PRBs, and the PSFCH opportunity415-fmay include Z″ PRBs. Such variation in size of the PSFCH opportunities415corresponding to the LBT sub-band405-aor the PSSCH410-amay be referred to herein as a heterogeneous PSFCH resource pool. In such examples, however, the configuration may refrain from separately indicating Z, Z′, and Z″ (even when they are of different values). Further, althoughFIG.4illustrates that each of the multiple PSFCH opportunities415of the multiple PSFCH resource pools are located within one PSFCH symbol420, the described techniques may be extended to any number of PSFCH symbols420without exceeding the scope of the present disclosure.

FIG.5illustrates an example of a resource configuration500that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. The resource configuration500may be implemented to realize aspects of the wireless communications system100or the wireless communications system200. For example, a first UE115may groupcast a data transmission to multiple UEs115, which may be examples of corresponding devices described herein, over a PSSCH510and one or more of the multiple UEs115may transmit feedback associated with the transmission to the first UE115over one or more of multiple PSFCH opportunities515corresponding to the PSSCH510.

In some implementations,FIG.5illustrates multiple heterogeneous (in size) PSFCH resource pools in which an LBT sub-band505-aor a PSSCH510may correspond to a PSFCH opportunity515-aand a PSFCH opportunity515-c. In some aspects, an LBT sub-band505-bmay correspond to a PSFCH opportunity515-b. In some examples, the PSSCH510may be an example of a groupcast PSSCH510requesting groupcast HARQ feedback option 2. In some examples, and based on the heterogenous PSFCH resource pools, the PSFCH opportunity515-amay include a first quantity of PRBs Z and the PSFCH opportunity515-cmay include a second quantity of PRBs Z′. Further, in some examples, the PSFCH opportunity515-amay be associated with a first cyclic shift value Y and the PSFCH opportunity515-bmay be associated with a second cyclic shift value Y′ different from the first cyclic shift value Y.

In such examples in which different PSFCH opportunities515include different numbers of PRBs and have different cyclic shift values, the configuration of the multiple PSFCH opportunities515may also indicate one of various options for how the multiple UEs115receiving the transmission over the PSSCH510may transmit feedback to the first UE115. In some aspects, the options may be configured per LBT sub-band505. In some implementations, for example, a UE115of the multiple UEs115that receive the data transmission from the first UE115over the PSSCH510may determine that the UE115is able to use the PSFCH opportunity515-c(e.g., or any PSFCH opportunity515in the LBT sub-band505-b) if a member ID of the UE115is not larger than (e.g., is less than or equal to) a product of the second quantity of PRBs in the PSFCH opportunity515-cand the second cyclic shift value of the PSFCH opportunity515-c. In other words, the UE115may use the PSFCH opportunity515-cin the LBT sub-band505-bif the member ID of the UE115is not larger than (or is less than or equal to) Z′*Y′. In such implementations, different UEs115of the multiple UEs115may have different quantities of PSFCH opportunities515(e.g., a UE115with a relatively lower member ID may have a greater quantity of PSFCH opportunities515than a UE115with a relatively higher member ID).

In some other implementations, the multiple UEs115that receive the transmission from the first UE115over the PSSCH510may determine that the multiple UEs115(e.g., all of the multiple UEs115) are able to use the PSFCH opportunity515-cif a quantity of the multiple UEs115X is not larger than (or is less than or equal to) a product of the second quantity of PRBs in the PSFCH opportunity515-cand the second cyclic shift value of the PSFCH opportunity515-c. In other words, the multiple UEs115may use the PSFCH opportunity515-cin the LBT sub-band505-bif the quantity of the multiple UEs115X is less than or equal to Z′*Y′(e.g., if X≤Z′*Y′). Alternatively, the multiple UEs115may refrain from using the PSFCH opportunity515-cin the LBT sub-band505-bif the quantity of the multiple UEs115X is greater than Z′*Y′(e.g., if X>Z′*Y′). In such implementations, bigger groups of UEs115(e.g., such that X>Z′*Y′) may be blocked from having multiple PSFCH opportunities515.

In some other implementations, the multiple UEs115that receive the transmission from the first UE115over the PSSCH510may determine that the multiple UEs115(e.g., all of the multiple UEs115) are able to use the PSFCH opportunity515-cif a first product of the first quantity of PRBs in the PSFCH opportunity515-aand the first cyclic shift value of the PSFCH opportunity515-ais less than or equal to a second product of the second quantity of PRBs in the PSFCH opportunity515-cand the second cyclic shift value of the PSFCH opportunity515-c. In other words, the multiple UEs115may use the PSFCH opportunity515-cin the LBT sub-band505-bif Z′*Y′≥Z*Y. Alternatively, the multiple UEs115may refrain from using the PSFCH opportunity515-cin the LBT sub-band505-bif Z′*Y′<Z*Y (e.g., which may be the case in examples in which the PSFCH opportunity515-cdoes not exist or is relatively small). In such implementations, groupcast HARQ response option 2 may be blocked for such PSFCH opportunities that do not exist or are relatively small.

Further, althoughFIG.5illustrates that each of the multiple PSFCH opportunities515of the multiple PSFCH resource pools are located with one PSFCH symbol520, the described techniques may be extended to any number of PSFCH symbols520without exceeding the scope of the present disclosure.

FIG.6illustrates an example of a resource configuration600that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. The resource configuration600may be implemented to realize aspects of the wireless communications system100or the wireless communications system200. For example, a first UE115may transmit a transmission to a second UE115, which may be examples of corresponding devices described herein, over a PSSCH610in an LBT sub-band605and the second UE115may transmit feedback associated with the transmission to the first UE115over one or more of multiple PSFCH opportunities615corresponding the PSSCH610or the LBT sub-band605. In some implementations, a single PSFCH resource pool may be configured for all of the LBT sub-bands605. In such implementations, the configuration of the multiple PSFCH opportunities615may define the multiple PSFCH opportunities615within the single PSFCH resource pool such that a PSSCH610or an LBT sub-band605may correspond to multiple PSFCH opportunities615over multiple LBT sub-bands605.

In some examples, the second UE115may receive a configuration indicating a sub-channel index i associated with the LBT sub-band605-aincluding a PSSCH610-aover which the second UE115may receive the transmission from the first UE115and a PSFCH opportunity615-a. In some aspects, the PSSCH610-amay be an example of a unicast PSSCH610that is transmitted over the leading sub-channel index i. In some implementations of the present disclosure, the configuration may also indicate a secondary sub-channel index j(i) that falls into a different LBT sub-band605, such as an LBT sub-band605-bincluding a PSSCH610-band a PSFCH opportunity615-b. The configuration may introduce a mapping from i to other sub-channels based on j (e.g., a mapping j(i) such that the second UE115may identify other PSFCH opportunities615in other LBT sub-bands605using j(i)). In some aspects, j(i) may be injective (e.g., a one-to-one mapping). As such, based on receiving an indication of the sub-channel index i and j(i), the second UE115may determine that its multiple PSFCH opportunities615may be found in the sub-channel index i (e.g., at the PSFCH opportunity615-a) and at the sub-channel index j(i) (e.g., at the PSFCH opportunity615-b).

In some cases, however, such as in cases in which the PSSCH610-bcarries a groupcast transmission, collision may occur in examples in which the second UE115transmits feedback over the PSFCH opportunity615-aand the PSFCH opportunity615-bbecause the PSFCH opportunity615-bmay also carry some groupcast feedback. Accordingly, in some implementations of the present disclosure, the second UE115may determine whether it is able to use the PSFCH opportunity615-b(without causing collision) if the PSSCH610-acarries a unicast transmission and if the PSSCH610-bdoes not carry a groupcast transmission. For example, if the second UE115receives a unicast transmission over the PSSCH610-afrom the first UE115and detects or otherwise determines that the PSSCH610-bdoes not carry a groupcast transmission (and is not a leading sub-channel), the second UE115may determine to use the PSFCH opportunity615-bin addition to the PSFCH opportunity615-abased on applying a formula. In some aspects, the second UE115may choose a PSFCH index (e.g., a PSFCH sequence index) at the sub-channel index j(i) in the form of the form of the formula.

In some aspects, the formula may be (K+M+O′)mod(Z*Y), where O′ is an offset depending on which LBT sub-band605the sub-channel index i is located in (e.g., depending on the LBT sub-band605-a), where K is an ID of the transmitting UE115(e.g., the first UE115) and may be 8-bit, and where M is set to 0 for unicast transmissions and to a group ID for groupcast HARQ response option 2. In some cases, the group ID may be within a set of numbers including {0, 1, . . . , X−1} (where X is equal to a quantity of the UEs115within the group). Additionally, groupcast HARQ response option 2 (e.g., which refers to respective response for different receivers) may not be used for X>Z*Y. In some implementations of the present disclosure, j(i) and O′ may be included in a higher layer signaling configuration, such as L3 signaling.

Further, althoughFIG.6illustrates that each of the multiple PSFCH opportunities615of a single PSFCH resource pool are located with one PSFCH symbol620, the described techniques may be extended to any number of PSFCH symbols620without exceeding the scope of the present disclosure.

FIG.7illustrates an example of a resource configuration700that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. The resource configuration700may be implemented to realize aspects of the wireless communications system100or the wireless communications system200. For example, a first UE115may transmit a transmission to a second UE115, which may be examples of corresponding devices described herein, over a PSSCH710in an LBT sub-band705and the second UE115may transmit feedback associated with the transmission to the first UE115over one or more of multiple PSFCH opportunities715corresponding to the PSSCH710or the LBT sub-band705. In some implementations, based on enabling multiple PSFCH opportunities715, a sidelink UE115may fill a time gap725between a PSSCH710-band a PSFCH730with a CP extension to transmit the feedback associated with a data transmission received over a PSSCH710-bin a same COT740of the PSSCH710-b.

As described in more detail herein, including with reference toFIG.3, the second UE115may receive, from the first UE115or from a serving base station105, a control message configuring multiple PSFCH opportunities715over multiple LBT sub-bands705for a PSSCH710over which the first UE115may transmit data to the second UE115. As shown inFIG.7, the second UE115may receive a configuration of four PSFCH opportunities715over two LBT sub-bands705and in two PSFCH symbols720. For instance, the control message may configure, for a PSSCH710-a, a PSFCH opportunity715-ain an LBT sub-band705-aand in a PSFCH symbol720-a, a PSFCH opportunity715-bin an LBT sub-band705-band in the PSFCH symbol720-a, a PSFCH opportunity715-cin the LBT sub-band705-aand in a PSFCH symbol720-b, and a PSFCH opportunity715-din the LBT sub-band705-band in the PSFCH symbol720-b.

In some aspects, there may be a time gap725between a PSSCH710and a PSFCH730. In some cases, such a time gap725may be configured such that UEs115may perform LBT during the time gap725to determine whether a corresponding (e.g., a subsequent) PSFCH opportunity715is available or occupied. For example, there may be a time gap725-aprior to the PSFCH730in the PSFCH symbol720-aand a time gap725-bprior to the PSFCH730in the PSFCH symbol720-b. In some cases, a PSSCH710-bmay be scheduled adjacent to the time gap725-bsuch that the time gap725-bmay represent a gap in time between the PSSCH710-band the PSFCH730in the PSFCH symbol720-b.

In some examples, such as in examples in which the a UE115receives a data transmission (e.g., a unicast data transmission) over the PSSCH710-b, the UE115may attempt to employ a CP extension into the time gap725-bto enable the UE115to transmit feedback associated with the data transmission received over the PSSCH710-bwithin a same COT740as the PSSCH710-b. In some cases, however, such a CP extension into the time gap725-bmay block one or more nearby UE's115LBT for the PSFCH730(e.g., for the PSFCH opportunity715-c). To maintain minimal blocking, the UE115may determine whether the UE115is able to employ such CP extension (e.g., whether such CP extension is allowed) based on whether conditions (e.g., pre-defined conditions) for CP extension are satisfied. In some implementations, for example, the UE115may employ the CP extension to transmit feedback associated with the data transmission received over the PSSCH710-bif the PSSCH710-bcarries data having a priority that satisfies a threshold priority. In such implementations, the CP extension or the threshold priority, or both, may be configured via a system information block (SIB) or a pre-configuration. Additionally or alternatively, the UE115may employ the CP extension if the PSSCH710-bhas a sufficiently high likelihood of missing a packet delay budget threshold or value associated with the PSSCH710-b. In such implementations, the CP extension can be configured via a 1-bit indication in SCI.

Additionally or alternatively, the UE115may employ the CP extension over one (e.g., only one) of a last time-domain PSFCH opportunity715. For instance, in examples in which the PSFCH symbol720-bincludes the last time-domain PSFCH opportunities715corresponding to the PSSCH710-b, the UE115may employ the CP extension. Additionally or alternatively, the UE115may employ the CP extension if the UE115has employed the CP extension below a threshold usage ratio (e.g., a pre-defined threshold usage ratio). For example, if the UE115has employed similar CP extension lower than a threshold number of times or at lower than a threshold frequency, the UE115may employ the CP extension. Additionally or alternatively, the UE115may employ the CP extension over a pre-configured LBT sub-band705or over a pre-configured LBT sub-band705at indicated slots. For example, the UE115may receive an indication of an LBT sub-band705(such as an LBT sub-band705-a) or an indication of the LBT sub-band705at given slots and the UE115may employ the CP extension in the indicated LBT sub-band705or in the indicated LBT sub-band705at the given slots.

In examples in which any one or more of the above conditions for employing the CP extension are satisfied, the UE115(e.g. a HARQ responder) may check out the COT740for the PSSCH710-band may use the COT740to transmit feedback associated with the data received over the PSSCH710-bover the PSFCH730without leaving the time gap725-bbefore the PSFCH opportunity715-cempty. For example, the UE115may transmit feedback associated with the data received over the PSSCH710-bover a resource opportunity735located in the time gap725-bbetween the PSSCH710-band the PSFCH opportunity715-c. The UE115, based on implementing such a CP extension, may refrain from giving up a current COT740based on experiencing greater than a threshold duration of silence (e.g., a lack of communication) and, accordingly, may refrain from performing category 4 (Cat4) LBT for that period (which may have a low likelihood of being successful for the PSFCH opportunity715-cdue to the short time duration between the PSSCH710-band the PSFCH opportunity715-c).

FIG.8illustrates an example of a process flow800that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. In some examples, the process flow800may implement aspects of the wireless communications system100or the wireless communications system200. For example, the process flow800may illustrate communication between a UE115-dand a UE115-d, which may be examples of corresponding devices described herein. In some implementations, the UE115-cmay transmit a control message to the UE115-dincluding a configuration for transmitting feedback over multiple feedback channel occasions over multiple LBT sub-bands that correspond to a sidelink data channel (e.g., a PSSCH) over which the UE115-ctransmits a data transmission to the UE115-d.

At805, the UE115-cmay transmit, to the UE115-d, a control message including a configuration for multiple feedback channel occasions in multiple sub-bands (e.g., LBT sub-bands) of an unlicensed radio frequency spectrum band. In some examples, such as in examples in which the configuration indicates multiple feedback channel pools (e.g., PSFCH resource pools), the configuration for the multiple feedback channel occasions may include one or more bit vectors (e.g., one or more PRB-level bit vectors), and each bit vector may indicate the feedback channel occasions included within a feedback channel pool. In some other examples, the configuration may indicate a single feedback channel pool and the configuration may indicate a mapping (e.g., a mapping between a sub-channel index i and a sub-channel index j(i)) such that the multiple feedback channel occasions are distributed across multiple LBT sub-bands. For instance, in examples in which the configuration indicates one feedback channel pool, the configuration may indicate an index associated with a second LBT sub-band and an offset value between a first LBT sub-band and a second LBT sub-band.

In some examples, the multiple feedback channel occasions may include a first feedback channel occasion located in the first LBT sub-band and a second feedback channel occasion located in the second LBT sub-band. In some implementations, the configuration for the multiple feedback channel occasions may indicate a primary feedback channel occasion and one or more secondary feedback channel occasions. In some other implementations, the configuration for the multiple feedback channel occasions may indicate a priority or an order of the multiple feedback channel occasions.

In some examples, the multiple feedback channel occasions may be associated with groupcast feedback (e.g., groupcast HARQ feedback option 2). In an example, if the UE115-ddetermines that a group member ID of the UE115-dis less than a product of a quantity of PRBs of a feedback channel occasion and a cyclic shift value associated with the feedback channel occasion, the UE115-dmay include the feedback channel occasion in the multiple feedback channel occasions. In an example, if the UE115-ddetermines that a quantity of UEs providing the groupcast feedback is less than a product of a quantity of PRBs of a feedback channel occasion and a cyclic shift value associated with the feedback channel occasion, the UE115-dmay include the feedback channel occasion in the multiple feedback channel occasions. In an example, if the UE115-didentifies a first feedback channel occasion in a first sub-band and a second feedback channel occasion in a second sub-band and if the UE115-ddetermines that a first product of a first quantity of PRBs of the first feedback channel occasion and a first cyclic shift value associated with the first feedback channel occasion is less than a second product of a second quantity of PRBs of the second feedback channel occasion and a second cyclic shift value associated with the second feedback channel occasion, the UE115-dmay include both the first feedback channel occasion and the second feedback channel occasion in the multiple feedback channel occasions.

At810, the UE115-cmay transmit, to the UE115-d, a data transmission over a first sidelink data channel in the first LBT sub-band of the unlicensed radio frequency spectrum band. In some examples, the data transmission may be a unicast transmission. In such examples, if the UE115-ddetects a unicast transmission over a second sidelink data channel in the second LBT sub-band, the UE115-dmay include, in the multiple feedback channel occasions, a first feedback channel occasion located in the first LBT sub-band and a second feedback channel occasion located in the second LBT sub-band based at least in part on detecting the unicast transmission. The UE115-dmay transmit a sequence over the first feedback channel occasion or the second feedback channel occasion based at least in part on a formula. The formula may include a first product of a summation of an ID associated with the UE115-cand an offset value between the second LBT sub-band and the first LBT sub-band and a modulo operation of a second product of a quantity of PRBs of the first feedback channel occasion and a cyclic shift value associated with the first feedback channel occasion.

At815, the UE115-dmay perform an LBT procedure for each of the multiple feedback channel occasions. The LBT procedure may be equivalently referred to as a channel access procedure. The UE115-dmay perform the LBT procedure to determine which of the multiple feedback channel occasions are available for transmitting feedback associated with the data transmission to the UE115-c.

At820, the UE115-dmay transmit, to the UE115-c, feedback associated with the data transmission over one or more of the multiple feedback channel occasions based at least in part on the LBT procedure and the configuration for the multiple feedback channel occasions. In some examples, the UE115-dmay transmit the feedback to the UE115-cover each feedback channel occasion of the multiple feedback channel occasions that is associated with a successful LBT procedure and is located in an earliest symbol period. In some other examples, the UE115-dmay transmit the feedback to the UE115-cover a primary feedback channel occasion or over any secondary feedback channel occasions of the multiple feedback channel occasions based at least in part on whether the primary feedback channel occasion is associated with a successful LBT procedure. For example, if the LBT procedure for the primary feedback channel occasion is successful, the UE115-dmay transmit the feedback to the UE115-cover the primary feedback channel occasion. Alternatively, if the LBT procedure for the primary feedback channel occasion is unsuccessful, the UE115-dmay transmit the feedback to the UE115-cover any one of the second feedback channel occasions.

In some other examples, the UE115-dmay transmit the feedback to the UE115-cover a feedback channel occasion of the multiple feedback channel occasions that has a highest priority and is associated with a successful LBT procedure. In some other examples, the UE115-dmay transmit the feedback to the UE115-cover each feedback channel occasion of the multiple feedback channel occasions that is associated with a successful LBT procedure. In some other examples, the UE115-dmay transmit the feedback to the UE115-cwithin a same COT of the data transmission based at least in part on a cyclic prefix extension. In some implementations, the UE115-dmay transmit the feedback to the UE115-cover a resource occasion prior to the feedback channel within the same COT of the data transmission based at least in part on determining that a priority of the data transmission satisfies a threshold priority, that the first feedback channel occasion is an only feedback channel occasion that satisfies a packet delay budget of the transmission, that the first feedback channel occasion is in a last symbol period including a feedback channel occasion, that previous cyclic prefix extensions have occurred below a threshold amount, that the first feedback channel occasion is configured for transmitting the feedback within the same channel occupancy time, or any combination thereof.

FIG.9shows a block diagram900of a device905that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. The device905may be an example of aspects of a UE115as described herein. The device905may include a receiver910, a transmitter915, and a communications manager920. The device905may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The transmitter915may provide a means for transmitting signals generated by other components of the device905. For example, the transmitter915may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to techniques for configuring multiple frequency domain opportunities for sidelink feedback). In some examples, the transmitter915may be co-located with a receiver910in a transceiver component. The transmitter915may utilize a single antenna or a set of multiple antennas.

The communications manager920, the receiver910, the transmitter915, or various combinations thereof or various components thereof may be examples of means for performing various aspects of techniques for configuring multiple frequency domain opportunities for sidelink feedback as described herein. For example, the communications manager920, the receiver910, the transmitter915, or various combinations or components thereof may support a method for performing one or more of the functions described herein.

The communications manager920may support wireless communication at a UE in accordance with examples as disclosed herein. For example, the communications manager920may be configured as or otherwise support a means for receiving a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band. The communications manager920may be configured as or otherwise support a means for performing an LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands. The communications manager920may be configured as or otherwise support a means for transmitting feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions.

Additionally or alternatively, the communications manager920may support wireless communication at a UE in accordance with examples as disclosed herein. For example, the communications manager920may be configured as or otherwise support a means for transmitting a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band. The communications manager920may be configured as or otherwise support a means for transmitting a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band. The communications manager920may be configured as or otherwise support a means for receiving feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on an LBT for each of the set of multiple feedback channel occasions.

By including or configuring the communications manager920in accordance with examples as described herein, the device905(e.g., a processor controlling or otherwise coupled to the receiver910, the transmitter915, the communications manager920, or a combination thereof) may support techniques for reduced processing, reduced power consumption, and more efficient utilization of communication resources.

In some examples, the communications manager920may be implemented as an integrated circuit or chipset for a mobile device modem, and the receiver910and the transmitter915may be implemented as analog components (for example, amplifiers, filters, antennas) coupled to the mobile device modem to enable wireless transmission and reception over one or more bands.

The communications manager920may be implemented to realize one or more potential advantages. In some implementations in which the communications manager920functions as a device transmitting feedback, the communications manager920may experience a greater likelihood of performing a successful LBT procedure for at least one of multiple PSFCH opportunities over multiple LBT sub-bands over which the communications manager920may transmit feedback responsive to a data transmission over a PSSCH in an LBT sub-band (where the multiple PSFCH opportunities correspond to (e.g., are assigned or mapped to) the PSSCH or the LBT sub-band over which the data transmission is sent). Based on having a greater likelihood for at least one of the multiple PSFCH opportunities to pass LBT, the communications manager920may likewise have a greater likelihood of transmitting feedback to a transmitting device (e.g., another UE115), which may result in fewer potentially unnecessary re-transmissions of the data transmission. In other words, based on implementing aspects of the present disclosure, the communications manager920may receive fewer re-transmissions of a data transmission due to LBT failure (which may be unnecessary re-transmissions) rather than due to reception failure. Accordingly, based on potentially reducing a number of re-transmissions that are sent, the communications manager920may lower the likelihood of a declaration of an RLF event.

Based on reducing a number of potentially unnecessary re-transmissions and lowering the likelihood of RLF, the communications manager920, or one or more processing components of the communications manager920, may enter a sleep mode (or power off) for longer durations or more frequently, which may improve power savings and increase battery life at the device905.

Further, in examples in which the communications manager920functions as a device receiving feedback, and based on implementing the described techniques, the communications manager920may have a greater likelihood of receiving feedback from a receiving device (e.g., another UE115), which may provide greater or more robust insight into how a data transmission was received at the receiving device for the communications manager920. For example, based on having a greater likelihood of receiving feedback from the receiving device, the communications manager920may more accurately determine whether the data transmission was successfully or unsuccessfully received. Accordingly, the communications manager920may more accurately determine whether a re-transmission of the data transmission is necessary (as the likelihood of the communications manager920failing to receive feedback due to LBT failure, as opposed to reception failure, is lower). In examples in which the communications manager920experiences such a lower likelihood of failing to receive feedback due to LBT failure, the communications manager920may more accurately determine whether to send a re-transmission of the data transmission, which may also improve power savings and increase battery life of the device905.

The device1005, or various components thereof, may be an example of means for performing various aspects of techniques for configuring multiple frequency domain opportunities for sidelink feedback as described herein. For example, the communications manager1020may include a sidelink transmission component1025, an LBT component1030, a feedback transmission component1035, an PSFCH configuration component1040, a feedback reception component1045, or any combination thereof. The communications manager1020may be an example of aspects of a communications manager920as described herein. In some examples, the communications manager1020, or various components thereof, may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver1010, the transmitter1015, or both. For example, the communications manager1020may receive information from the receiver1010, send information to the transmitter1015, or be integrated in combination with the receiver1010, the transmitter1015, or both to receive information, transmit information, or perform various other operations as described herein.

The communications manager1020may support wireless communication at a UE in accordance with examples as disclosed herein. The sidelink transmission component1025may be configured as or otherwise support a means for receiving a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band. The LBT component1030may be configured as or otherwise support a means for performing an LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands. The feedback transmission component1035may be configured as or otherwise support a means for transmitting feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions.

Additionally or alternatively, the communications manager1020may support wireless communication at a UE in accordance with examples as disclosed herein. The PSFCH configuration component1040may be configured as or otherwise support a means for transmitting a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band. The sidelink transmission component1025may be configured as or otherwise support a means for transmitting a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band. The feedback reception component1045may be configured as or otherwise support a means for receiving feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on an LBT for each of the set of multiple feedback channel occasions.

FIG.11shows a block diagram1100of a communications manager1120that supports techniques for configuring multiple frequency domain opportunities for sidelink feedback in accordance with various aspects of the present disclosure. The communications manager1120may be an example of aspects of a communications manager920, a communications manager1020, or both, as described herein. The communications manager1120, or various components thereof, may be an example of means for performing various aspects of techniques for configuring multiple frequency domain opportunities for sidelink feedback as described herein. For example, the communications manager1120may include a sidelink transmission component1125, an LBT component1130, a feedback transmission component1135, an PSFCH configuration component1140, a feedback reception component1145, a groupcast feedback component1150, a unicast feedback component1155, or any combination thereof. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The communications manager1120may support wireless communication at a UE in accordance with examples as disclosed herein. The sidelink transmission component1125may be configured as or otherwise support a means for receiving a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band. The LBT component1130may be configured as or otherwise support a means for performing an LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands. The feedback transmission component1135may be configured as or otherwise support a means for transmitting feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions.

In some examples, the PSFCH configuration component1140may be configured as or otherwise support a means for receiving a control message including a configuration of the set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, where performing the LBT for each of the set of multiple feedback channel occasions is based on the configuration of the set of multiple feedback channel occasions.

In some examples, to support receiving the control message including the configuration of the set of multiple feedback channel occasions, the PSFCH configuration component1140may be configured as or otherwise support a means for receiving the control message including the configuration indicating a set of multiple feedback channel pools, each of the set of multiple feedback channel pools corresponding to one sub-band of the unlicensed radio frequency spectrum band, where the set of multiple feedback channel occasions includes one feedback channel pool of the set of multiple feedback channel pools. In some examples, the configuration indicating the set of multiple feedback channel pools includes a set of multiple bit vectors, each bit vector indicating a different one of the set of multiple feedback channel pools.

In some examples, the set of multiple feedback channel occasions are associated with groupcast feedback, and the groupcast feedback component1150may be configured as or otherwise support a means for determining that a group member ID of the UE is less than a product of a quantity of PRBs of a feedback channel occasion of the set of multiple feedback channel occasions and a cyclic shift value associated with the feedback channel occasion. In some examples, the set of multiple feedback channel occasions are associated with groupcast feedback, and the groupcast feedback component1150may be configured as or otherwise support a means for including the feedback channel occasion in the set of multiple feedback channel occasions based on determining that the group member ID of the UE is less than the product of the quantity of PRBs and the cyclic shift value.

In some examples, the set of multiple feedback channel occasions are associated with groupcast feedback, and the groupcast feedback component1150may be configured as or otherwise support a means for determining that a quantity of UEs providing the groupcast feedback is less than a product of a quantity of PRBs of a feedback channel occasion of the set of multiple feedback channel occasions and a cyclic shift value associated with the feedback channel occasion. In some examples, the set of multiple feedback channel occasions are associated with groupcast feedback, and the groupcast feedback component1150may be configured as or otherwise support a means for including the feedback channel occasion in the set of multiple feedback channel occasions based on determining that the quantity of UEs providing the groupcast feedback is less than the product of the quantity of PRBs and the cyclic shift value.

In some examples, the set of multiple feedback channel occasions are associated with groupcast feedback, and the groupcast feedback component1150may be configured as or otherwise support a means for identifying that the set of multiple feedback channel occasions includes a first feedback channel occasion in the first sub-band and a second feedback channel occasion in a second sub-band. In some examples, the set of multiple feedback channel occasions are associated with groupcast feedback, and the groupcast feedback component1150may be configured as or otherwise support a means for determining that a first product of a first quantity of PRBs of the first feedback channel occasion and a first cyclic shift value associated with the first feedback channel occasion is less than a second product of a second quantity of PRBs of the second feedback channel occasion and a second cyclic shift value associated with the second feedback channel occasion. In some examples, the set of multiple feedback channel occasions are associated with groupcast feedback, and the groupcast feedback component1150may be configured as or otherwise support a means for including the first feedback channel occasion and the second feedback channel occasion in the set of multiple feedback channel occasions based on determining that the first product is less than the second product.

In some examples, to support receiving the control message including the configuration of the set of multiple feedback channel occasions, the PSFCH configuration component1140may be configured as or otherwise support a means for receiving the control message including the configuration indicating an index associated with a second sub-band and an offset value between the first sub-band and the second sub-band, where the set of multiple feedback channel occasions include a first feedback channel occasion located in the first sub-band and a second feedback channel occasion located in the second sub-band.

In some examples, the transmission is a unicast transmission, and the unicast feedback component1155may be configured as or otherwise support a means for detecting a second unicast transmission over a second sidelink data channel in the second sub-band based on the index associated with the second sub-band. In some examples, the transmission is a unicast transmission, and the unicast feedback component1155may be configured as or otherwise support a means for selecting the first feedback channel occasion and the second feedback channel occasion as two of the set of multiple feedback channel occasions based on detecting the second unicast transmission in the second sub-band and a formula.

In some examples, the formula includes a first product of a summation of an ID associated with a transmitting UE from which the transmission is received and the offset value between the first sub-band and the second sub-band and a modulo operation of a second product of a quantity of PRBs of the first feedback channel occasion and a cyclic shift value associated with the first feedback channel occasion.

In some examples, to support transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions, the feedback transmission component1135may be configured as or otherwise support a means for transmitting the feedback over each feedback channel occasion of the set of multiple feedback channel occasions that is associated with a successful LBT and that is located in an earliest symbol period including a feedback channel occasion.

In some examples, the feedback transmission component1135may be configured as or otherwise support a means for receiving a configuration indicating a primary feedback channel occasion and one or more secondary feedback channel occasions of the set of multiple feedback channel occasions. In some examples, to transmit the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions, the feedback transmission component1135may be configured as or otherwise support a means for transmitting the feedback over the primary feedback channel occasion or over any of the one or more secondary feedback channel occasions based on whether the primary feedback channel occasion is associated with a successful LBT.

In some examples, the feedback transmission component1135may be configured as or otherwise support a means for receiving a configuration indicating a priority of the set of multiple feedback channel occasions. In some examples, to transmit the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions, the feedback transmission component1135may be configured as or otherwise support a means for transmitting the feedback over a feedback channel occasion of the set of multiple feedback channel occasions that has a highest priority and that is associated with a successful LBT.

In some examples, to support transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions, the feedback transmission component1135may be configured as or otherwise support a means for transmitting the feedback over each feedback channel occasion of the set of multiple feedback channel occasions that is associated with a successful LBT.

In some examples, to support transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions, the feedback transmission component1135may be configured as or otherwise support a means for transmitting the feedback over a first feedback channel occasion within a same COT of the transmission based on a cyclic prefix extension.

In some examples, the feedback transmission component1135may be configured as or otherwise support a means for determining that a priority of the transmission satisfies a threshold priority, that the first feedback channel occasion is an only feedback channel occasion that satisfies a packet delay budget of the transmission, that the first feedback channel occasion is in a last symbol period including a feedback channel occasion, that previous cyclic prefix extensions have occurred below a threshold amount, that the first feedback channel occasion is configured for transmitting the feedback within the same COT, or any combination thereof, where transmitting the feedback over the first feedback channel occasion within the same COT of the transmission is based on the determining.

Additionally or alternatively, the communications manager1120may support wireless communication at a UE in accordance with examples as disclosed herein. The PSFCH configuration component1140may be configured as or otherwise support a means for transmitting a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band. In some examples, the sidelink transmission component1125may be configured as or otherwise support a means for transmitting a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band. The feedback reception component1145may be configured as or otherwise support a means for receiving feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on an LBT for each of the set of multiple feedback channel occasions.

In some examples, to support transmitting the control message including the configuration of the set of multiple feedback channel occasions, the PSFCH configuration component1140may be configured as or otherwise support a means for transmitting the control message including the configuration indicating a set of multiple feedback channel pools, each of the set of multiple feedback channel pools corresponding to one sub-band of the unlicensed radio frequency spectrum band, where the set of multiple feedback channel occasions includes one feedback channel pool of the set of multiple feedback channel pools.

In some examples, the configuration indicating the set of multiple feedback channel pools includes a set of multiple bit vectors, each bit vector indicating a different one of the set of multiple feedback channel pools.

In some examples, to support transmitting the control message including the configuration of the set of multiple feedback channel occasions, the PSFCH configuration component1140may be configured as or otherwise support a means for transmitting the control message including the configuration indicating an index associated with a second sub-band and an offset value between the first sub-band and the second sub-band, where the set of multiple feedback channel occasions include a first feedback channel occasion located in the first sub-band and a second feedback channel occasion located in the second sub-band.

In some examples, to support receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions, the feedback reception component1145may be configured as or otherwise support a means for receiving the feedback over each feedback channel occasion of the set of multiple feedback channel occasions that is associated with a successful LBT and that is located in an earliest symbol period including a feedback channel occasion.

In some examples, transmitting the control message includes transmitting the configuration indicating a primary feedback channel occasion and one or more secondary feedback channel occasions of the set of multiple feedback channel occasions. In some examples, receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions includes receiving the feedback over the primary feedback channel occasion or over any of the one or more secondary feedback channel occasions based on whether the primary feedback channel occasion is associated with a successful LBT.

In some examples, transmitting the control message includes transmitting the configuration indicating a priority of the set of multiple feedback channel occasions. In some examples, receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions includes receiving the feedback over a feedback channel occasion of the set of multiple feedback channel occasions that has a highest priority and that is associated with a successful LBT.

In some examples, to support receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions, the feedback reception component1145may be configured as or otherwise support a means for receiving the feedback over each feedback channel occasion of the set of multiple feedback channel occasions that is associated with a successful LBT.

In some examples, to support receiving the feedback associated with the transmission over the one or more feedback channel occasions of the set of multiple feedback channel occasions, the feedback reception component1145may be configured as or otherwise support a means for receiving the feedback over a first feedback channel occasion within a same COT of the transmission based on a cyclic prefix extension.

The I/O controller1210may manage input and output signals for the device1205. The I/O controller1210may also manage peripherals not integrated into the device1205. In some cases, the I/O controller1210may represent a physical connection or port to an external peripheral. In some cases, the I/O controller1210may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. Additionally or alternatively, the I/O controller1210may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller1210may be implemented as part of a processor, such as the processor1240. In some cases, a user may interact with the device1205via the I/O controller1210or via hardware components controlled by the I/O controller1210.

The communications manager1220may support wireless communication at a UE in accordance with examples as disclosed herein. For example, the communications manager1220may be configured as or otherwise support a means for receiving a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band. The communications manager1220may be configured as or otherwise support a means for performing an LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands. The communications manager1220may be configured as or otherwise support a means for transmitting feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions.

Additionally or alternatively, the communications manager1220may support wireless communication at a UE in accordance with examples as disclosed herein. For example, the communications manager1220may be configured as or otherwise support a means for transmitting a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band. The communications manager1220may be configured as or otherwise support a means for transmitting a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band. The communications manager1220may be configured as or otherwise support a means for receiving feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on an LBT for each of the set of multiple feedback channel occasions.

By including or configuring the communications manager1220in accordance with examples as described herein, the device1205may support techniques for improved communication reliability, reduced latency, improved user experience related to reduced processing, reduced power consumption, more efficient utilization of communication resources, improved coordination between devices, longer battery life, and improved utilization of processing capability, among other benefits.

At1305, the method may include receiving a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band. The operations of1305may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1305may be performed by a sidelink transmission component1125as described with reference toFIG.11.

At1310, the method may include performing an LBT for each of a set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands. The operations of1310may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1310may be performed by an LBT component1130as described with reference toFIG.11.

At1315, the method may include transmitting feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions. The operations of1315may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1315may be performed by a feedback transmission component1135as described with reference toFIG.11.

At1405, the method may include receiving a control message including a configuration of a set of multiple feedback channel occasions corresponding to a first sidelink data channel in a first sub-band. The operations of1405may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1405may be performed by an PSFCH configuration component1140as described with reference toFIG.11.

At1410, the method may include receiving a transmission over the first sidelink data channel in the first sub-band of an unlicensed radio frequency spectrum band. The operations of1410may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1410may be performed by a sidelink transmission component1125as described with reference toFIG.11.

At1415, the method may include performing an LBT for each of the set of multiple feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the set of multiple feedback channel occasions in a set of multiple sub-bands. The operations of1415may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1415may be performed by an LBT component1130as described with reference toFIG.11.

At1420, the method may include transmitting feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on the LBT for each of the set of multiple feedback channel occasions. The operations of1420may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1420may be performed by a feedback transmission component1135as described with reference toFIG.11.

At1505, the method may include transmitting a control message including a configuration of a set of multiple feedback channel occasions in a set of multiple sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band. The operations of1505may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1505may be performed by an PSFCH configuration component1140as described with reference toFIG.11.

At1510, the method may include transmitting a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band. The operations of1510may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1510may be performed by a sidelink transmission component1125as described with reference toFIG.11.

At1515, the method may include receiving feedback associated with the transmission over one or more feedback channel occasions of the set of multiple feedback channel occasions based on an LBT for each of the set of multiple feedback channel occasions. The operations of1515may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of1515may be performed by a feedback reception component1145as described with reference toFIG.11.

Aspect 1: A method for wireless communication at a UE, comprising: receiving a transmission over a first sidelink data channel in a first sub-band of an unlicensed radio frequency spectrum band; performing an LBT for each of a plurality of feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, the plurality of feedback channel occasions in a plurality of sub-bands; and transmitting feedback associated with the transmission over one or more feedback channel occasions of the plurality of feedback channel occasions based at least in part on the LBT for each of the plurality of feedback channel occasions.

Aspect 2: The method of aspect 1, further comprising: receiving a control message including a configuration of the plurality of feedback channel occasions corresponding to the first sidelink data channel in the first sub-band, wherein performing the LBT for each of the plurality of feedback channel occasions is based at least in part on the configuration of the plurality of feedback channel occasions.

Aspect 3: The method of aspect 2, wherein receiving the control message including the configuration of the plurality of feedback channel occasions comprises: receiving the control message including the configuration indicating a plurality of feedback channel pools, each of the plurality of feedback channel pools corresponding to one sub-band of the unlicensed radio frequency spectrum band, wherein the plurality of feedback channel occasions includes the one feedback channel pool of the plurality of feedback channel pools.

Aspect 4: The method of aspect 3, wherein the configuration indicating the plurality of feedback channel pools comprises a plurality of bit vectors, each bit vector indicating a different one of the plurality of feedback channel pools.

Aspect 5: The method of any of aspects 3 through 4, wherein the plurality of feedback channel occasions are associated with groupcast feedback, the method further comprising: determining that a group member ID of the UE is less than a product of a quantity of PRBs of a feedback channel occasion of the plurality of feedback channel occasions and a cyclic shift value associated with the feedback channel occasion; and including the feedback channel occasion in the plurality of feedback channel occasions based at least in part on determining that the group member ID the UE is less than the product of the quantity of PRBs and the cyclic shift value.

Aspect 6: The method of any of aspects 3 through 4, wherein the plurality of feedback channel occasions are associated with groupcast feedback, the method further comprising: determining that a quantity of UEs providing the groupcast feedback is less than a product of a quantity of PRBs of a feedback channel occasion of the plurality of feedback channel occasions and a cyclic shift value associated with the feedback channel occasion; and including the feedback channel occasion in the plurality of feedback channel occasions based at least in part on determining that the quantity of UEs providing the groupcast feedback is less than the product of the quantity of PRBs and the cyclic shift value.

Aspect 7: The method of any of aspects 3 through 4, wherein the plurality of feedback channel occasions are associated with groupcast feedback, the method further comprising: identifying that the plurality of feedback channel occasions includes a first feedback channel occasion in the first sub-band and a second feedback channel occasion in a second sub-band; determining that a first product of a first quantity of PRBs of the first feedback channel occasion and a first cyclic shift value associated with the first feedback channel occasion is less than a second product of a second quantity of PRBs of the second feedback channel occasion and a second cyclic shift value associated with the second feedback channel occasion; and including the first feedback channel occasion and the second feedback channel occasion in the plurality of feedback channel occasions based at least in part on determining that the first product is less than the second product.

Aspect 8: The method of aspect 2, wherein receiving the control message including the configuration of the plurality of feedback channel occasions comprises: receiving the control message including the configuration indicating an index associated with a second sub-band and an offset value between the first sub-band and the second sub-band, wherein the plurality of feedback channel occasions include a first feedback channel occasion located in the first sub-band and a second feedback channel occasion located in the second sub-band.

Aspect 9: The method of aspect 8, wherein the transmission is a unicast transmission, the method further comprising: detecting a second unicast transmission over a second sidelink data channel in the second sub-band based at least in part on the index associated with the second sub-band; and selecting the first feedback channel occasion and the second feedback channel occasion as two of the plurality of feedback channel occasions based at least in part on detecting the second unicast transmission in the second sub-band and a formula.

Aspect 10: The method of aspect 9, wherein the formula comprises a first product of a summation of an ID associated with a transmitting UE from which the transmission is received and the offset value between the first sub-band and the second sub-band and a modulo operation of a second product of a quantity of PRBs of the first feedback channel occasion and a cyclic shift value associated with the first feedback channel occasion.

Aspect 11: The method of any of aspects 1 through 10, wherein transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises: transmitting the feedback over each feedback channel occasion of the plurality of feedback channel occasions that is associated with a successful LBT and that is located in an earliest symbol period including a feedback channel occasion.

Aspect 12: The method of any of aspects 1 through 11, further comprising: receiving a configuration indicating a primary feedback channel occasion and one or more secondary feedback channel occasions of the plurality of feedback channel occasions, wherein transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises: transmitting the feedback over the primary feedback channel occasion or over any of the one or more secondary feedback channel occasions based at least in part on whether the primary feedback channel occasion is associated with a successful LBT.

Aspect 13: The method of any of aspects 1 through 12, further comprising: receiving a configuration indicating a priority of the plurality of feedback channel occasions, wherein transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises: transmitting the feedback over a feedback channel occasion of the plurality of feedback channel occasions that has a highest priority and that is associated with a successful LBT.

Aspect 14: The method of any of aspects 1 through 13, wherein transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises: transmitting the feedback over each feedback channel occasion of the plurality of feedback channel occasions that is associated with a successful LBT.

Aspect 15: The method of any of aspects 1 through 14, wherein transmitting the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises: transmitting the feedback over a first feedback channel occasion within a same COT of the transmission based at least in part on a cyclic prefix extension.

Aspect 16: The method of aspect 15, further comprising: determining that a priority of the transmission satisfies a threshold priority, that the first feedback channel occasion is an only feedback channel occasion that satisfies a packet delay budget of the transmission, that the first feedback channel occasion is in a last symbol period including a feedback channel occasion, that previous cyclic prefix extensions have occurred below a threshold amount, that the first feedback channel occasion is configured for transmitting the feedback within the same COT, or any combination thereof, wherein transmitting the feedback over the first feedback channel occasion within the same COT of the transmission is based at least in part on the determining.

Aspect 17: A method for wireless communication at a UE, comprising: transmitting a control message including a configuration of a plurality of feedback channel occasions in a plurality of sub-bands of an unlicensed radio frequency spectrum band corresponding to a first sidelink data channel in a first sub-band of the unlicensed radio frequency spectrum band; transmitting a transmission over the first sidelink data channel in the first sub-band of the unlicensed radio frequency spectrum band; and receiving feedback associated with the transmission over one or more feedback channel occasions of the plurality of feedback channel occasions based at least in part on an LBT for each of the plurality of feedback channel occasions.

Aspect 18: The method of aspect 17, wherein transmitting the control message including the configuration of the plurality of feedback channel occasions comprises: transmitting the control message including the configuration indicating a plurality of feedback channel pools, each of the plurality of feedback channel pools corresponding to one sub-band of the unlicensed radio frequency spectrum band, wherein the plurality of feedback channel occasions includes one feedback channel pool of the plurality of feedback channel pools.

Aspect 19: The method of aspect 18, wherein the configuration indicating the plurality of feedback channel pools comprises a plurality of bit vectors, each bit vector indicating a different one of the plurality of feedback channel pools.

Aspect 20: The method of aspect 17, wherein transmitting the control message including the configuration of the plurality of feedback channel occasions comprises: transmitting the control message including the configuration indicating an index associated with a second sub-band and an offset value between the first sub-band and the second sub-band, wherein the plurality of feedback channel occasions include a first feedback channel occasion located in the first sub-band and a second feedback channel occasion located in the second sub-band.

Aspect 21: The method of any of aspects 17 through 20, wherein receiving the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises: receiving the feedback over each feedback channel occasion of the plurality of feedback channel occasions that is associated with a successful LBT and that is located in an earliest symbol period including a feedback channel occasion.

Aspect 22: The method of any of aspects 17 through 21, wherein transmitting the control message comprises transmitting the configuration indicating a primary feedback channel occasion and one or more secondary feedback channel occasions of the plurality of feedback channel occasions; and receiving the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises receiving the feedback over the primary feedback channel occasion or over any of the one or more secondary feedback channel occasions based at least in part on whether the primary feedback channel occasion is associated with a successful LBT.

Aspect 23: The method of any of aspects 17 through 22, wherein transmitting the control message comprises transmitting the configuration indicating a priority of the plurality of feedback channel occasions; and receiving the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises receiving the feedback over a feedback channel occasion of the plurality of feedback channel occasions that has a highest priority and that is associated with a successful LBT.

Aspect 24: The method of any of aspects 17 through 23, wherein receiving the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises: receiving the feedback over each feedback channel occasion of the plurality of feedback channel occasions that is associated with a successful LBT.

Aspect 25: The method of any of aspects 17 through 24, wherein receiving the feedback associated with the transmission over the one or more feedback channel occasions of the plurality of feedback channel occasions comprises: receiving the feedback over a first feedback channel occasion within a same COT of the transmission based at least in part on a cyclic prefix extension.

Aspect 29: An apparatus for wireless communication at a UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 17 through 25.

Aspect 30: An apparatus for wireless communication at a UE, comprising at least one means for performing a method of any of aspects 17 through 25.