Concurrent physical sidelink feedback channel transmission

1. A method of wireless communication performed by a user equipment (UE), comprising:

identifying multiple candidate sets of physical sidelink feedback channel (PSFCH) transmissions, wherein the multiple candidate sets each include a plurality of PSFCH transmissions to provide hybrid automatic repeat request (HARQ) feedback for a plurality of sidelink communications received from one or more other UEs;

identifying, from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets;

selecting, from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set; and

transmitting, on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a HARQ feedback occasion.

2. The method of claim 1 , wherein the multiple candidate sets of PSFCH transmissions are identified based at least in part on one or more rules assigning priorities to the HARQ feedback for the plurality of sidelink communications.

3. The method of claim 2 , wherein the one or more rules assign HARQ feedback that includes a negative acknowledgment a higher priority than HARQ feedback that includes an acknowledgment.

4. The method of claim 1 , wherein a quantity of the PSFCH transmissions included in each of the multiple candidate sets satisfies a threshold value.

5. The method of claim 4 , wherein the threshold value is based at least in part on one or more of a capability associated with the UE, a configured value, or congestion on one or more of the PSFCH, a physical sidelink shared channel, or a physical sidelink control channel.

6. The method of claim 1 , wherein the at least one candidate set is randomly selected from at least two candidate sets, of the one or more candidate sets, for which respective utility parameters are equal in value.

7. The method of claim 1 , wherein the one or more candidate sets that satisfy the PSFCH transmit power constraint are identified based at least in part on respective link budget requirements for individual PSFCH transmissions in each of the multiple candidate sets.

8. The method of claim 7 , wherein the plurality of sidelink communications are received from the one or more other UEs over one or more of a physical sidelink shared channel (PSSCH) or a physical sidelink control channel (PSCCH), and wherein the link budget requirements for the individual PSFCH transmissions are based at least in part on a reference signal received power (RSRP) measurement associated with one or more of the PSSCH or the PSCCH.

9. The method of claim 8 , wherein the link budget requirement for an individual PSFCH transmission decreases as a corresponding RSRP measurement increases.

10. The method of claim 8 , wherein the link budget requirement for at least one individual PSFCH transmission is based at least in part on an average RSRP measurement for multiple sidelink communications from a particular UE.

11. The method of claim 8 , further comprising:

determining the link budget requirement for an individual PSFCH transmission based at least in part on a transmit power allocated to the individual PSFCH transmission, an attenuation associated with one of the plurality of sidelink communications corresponding to the individual PSFCH transmission, a noise within a transmission bandwidth associated with the individual PSFCH transmission, and a signal-to-noise ratio to decode the individual PSFCH transmission.

12. The method of claim 11 , wherein the attenuation associated with the sidelink communication corresponding to the individual PSFCH transmission is based at least in part on an original transmission power associated with the sidelink communication and an RSRP measurement associated with the sidelink communication.

13. The method of claim 1 , wherein the PSFCH transmit power constraint is a power backoff based at least in part on one or more of a maximum power reduction (MPR) value or an additional MPR (A-MPR) value to be added to the MPR value.

14. The method of claim 13 , further comprising:

determining a total available transmit power to use in the HARQ feedback occasion based at least in part on the power backoff, and

determining that the one or more candidate sets satisfy the PSFCH transmit power constraint based at least in part on the total available transmit power to use in the HARQ feedback occasion equaling or exceeding a sum of transmission powers allocated to the plurality of PSFCH transmissions included in the one or more candidate sets; and

applying one or more power sharing rules to allocate the total available transmit power to use in the HARQ feedback occasion among the plurality PSFCH transmissions that are transmitted in the HARQ feedback occasion.

15. The method of claim 14 , wherein the one or more power sharing rules include equally dividing the total available transmit power among the plurality of PSFCH transmissions transmitted in the HARQ feedback occasion.

16. The method of claim 14 , wherein the one or more power sharing rules include equally dividing the total available transmit power among a subset of resource blocks (RBs) used to transmit the plurality of PSFCH transmissions in the HARQ feedback occasion, and further equally dividing a portion of the total available transmit power allocated to a particular RB among a portion of the plurality of PSFCH transmissions that share the particular RB.

17. The method of claim 14 , wherein the one or more power sharing rules include equally dividing the total available transmit power among a subset of resource blocks (RBs) used to transmit the plurality of PSFCH transmissions in the HARQ feedback occasion, and further dividing a portion of the total available transmit power allocated to a particular RB among a portion of the plurality of PSFCH transmissions that share the particular RB based at least in part on one or more of a priority or an estimated link budget requirement associated with the portion of the PSFCH transmissions that share the particular RB.

18. The method of claim 14 , wherein the one or more power sharing rules include allocating the total available transmit power to the plurality of PSFCH transmissions transmitted in the HARQ feedback occasion based at least in part on respective link budget requirements for each individual PSFCH transmission according to a descending priority until the total available transmit power is exhausted.

19. The method of claim 1 , further comprising:

generating, for each of the one or more candidate sets that satisfy the PSFCH transmit power constraint, a bitmap in which each individual bit corresponds to an individual PSFCH transmission; and

assigning a utility value to each individual bit in the bitmap, wherein the respective utility parameters associated with the one or more candidate sets are based at least in part on a combination of the utility values assigned to the individual bits in the bitmaps associated with each respective candidate set.

20. The method of claim 19 , wherein each individual bit is set to a first value if a link budget requirement for the corresponding individual PSFCH transmission is satisfied or to a second value if a link budget requirement for a corresponding individual PSFCH transmission is not satisfied.

21. The method of claim 20 , wherein:

the utility value assigned to each individual bit set to the first value is based at least in part on one or more of a priority associated with the corresponding individual PSFCH transmission, a distance between the UE and a receiver of the corresponding individual PSFCH transmission, a reference signal received power between the UE and the receiver of the corresponding individual PSFCH transmission, a remaining delay budget for one of the plurality of sidelink communications associated with the corresponding individual PSFCH transmission, a packet reception rate associated with sidelink communications between the UE and the receiver of the corresponding individual PSFCH transmission, or a bit rate associated with the sidelink communications between the UE and the receiver of the corresponding individual PSFCH transmission, and

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

22. A user equipment (UE) for wireless communication, comprising:

a memory; and

one or more processors operatively coupled to the memory, the one or more processors configured to:

identify multiple candidate sets of physical sidelink feedback channel (PSFCH) transmissions, wherein the multiple candidate sets each include a plurality of PSFCH transmissions to provide hybrid automatic repeat request (HARQ) feedback for a plurality of sidelink communications received from one or more other UEs;

identify, from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets;

select, from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set; and

transmit, on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a HARQ feedback occasion.

23. The UE of claim 22 , wherein the multiple candidate sets of PSFCH transmissions are identified based at least in part on one or more rules assigning priorities to the HARQ feedback for the plurality of sidelink communications.

24. The UE of claim 22 , wherein a quantity of the PSFCH transmissions included in each of the multiple candidate sets satisfies a threshold value.

25. The UE of claim 22 , wherein the at least one candidate set is randomly selected from at least two candidate sets, of the one or more candidate sets, for which respective utility parameters are equal in value.

26. The UE of claim 22 , wherein the one or more candidate sets that satisfy the PSFCH transmit power constraint are identified based at least in part on respective link budget requirements for individual PSFCH transmissions in each of the multiple candidate sets.

27. The UE of claim 22 , wherein the PSFCH transmit power constraint is a power backoff based at least in part on one or more of a maximum power reduction (MPR) value or an additional MPR (A-MPR) value to be added to the MPR value.

28. The UE of claim 22 , wherein the one or more processors are further configured to:

generate, for each of the one or more candidate sets that satisfy the PSFCH transmit power constraint, a bitmap in which each individual bit corresponds to an individual PSFCH transmission; and

assign a utility value to each individual bit in the bitmap, wherein the respective utility parameters associated with the one or more candidate sets are based at least in part on a combination of the utility values assigned to the individual bits in the bitmaps associated with each respective candidate set.

29. A non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions comprising:

one or more instructions that, when executed by one or more processors of a user equipment (UE), cause the UE to:

identify multiple candidate sets of physical sidelink feedback channel (PSFCH) transmissions, wherein the multiple candidate sets each include a plurality of PSFCH transmissions to provide hybrid automatic repeat request (HARQ) feedback for a plurality of sidelink communications received from one or more other UEs;

identify, from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets;

select, from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set; and

transmit, on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a HARQ feedback occasion.

30. An apparatus for wireless communication, comprising:

means for identifying multiple candidate sets of physical sidelink feedback channel (PSFCH) transmissions, wherein the multiple candidate sets each include a plurality of PSFCH transmissions to provide hybrid automatic repeat request (HARQ) feedback for a plurality of sidelink communications received from one or more other user equipments (UEs);

means for identifying, from the multiple candidate sets, one or more candidate sets that satisfy a PSFCH transmit power constraint based at least in part on a total transmission power for the plurality of PSFCH transmissions included in the one or more candidate sets;

means for selecting, from the one or more candidate sets that satisfy the PSFCH transmit power constraint, at least one candidate set; and

means for transmitting, on a PSFCH, the plurality of PSFCH transmissions included in the at least one candidate set in a HARQ feedback occasion.

31. The method of claim 1 , wherein the at least one candidate set is selected based on having a highest value for a utility parameter among utility parameters associated with each of the one or more candidate sets.

32. The UE of claim 22 , wherein the at least one candidate set is selected based on having a highest value for a utility parameter among utility parameters associated with each of the one or more candidate sets.