Method of determining physical sidelink feedback channel resource for hybrid automatic repeat request feedback and related device

1. A method for a first user equipment (UE) for determining one or more physical sidelink feedback channel (PSFCH) resources for hybrid automatic repeat request (HARQ) feedback, the method comprising:

receiving, from a second UE, first sidelink control information (SCI) for scheduling a first unicast physical sidelink shared channel (PSSCH) transmission, the first SCI associated with a source identifier (ID);

receiving, from the second UE, second SCI for scheduling a second unicast PSSCH transmission, the second SCI associated with the same source ID;

determining priorities of a first HARQ feedback corresponding to the first PSSCH transmission and a second HARQ feedback corresponding to the second PSSCH transmission according, respectively, to the first SCI and the second SCI; and

transmitting, to the second UE, a PSFCH for at least one of the first HARQ feedback and the second HARQ feedback with a higher priority according to the determined priorities when a first PSFCH resource for the first HARQ feedback and a second PSFCH resource for the second HARQ feedback are at least partially overlapped in time domain, wherein transmitting the PSFCH comprises transmitting HARQ bits of both of the first and second HARQ feedbacks in the PSFCH when the PSFCH has enough resource size to include the HARQ bits of both of the first and second HARQ feedbacks in at least four slots after the first and second PSCCH transmissions.

2. The method of claim 1 , further comprising:

dropping another one of the first HARQ feedback and the second HARQ feedback with a lower priority according to the determined priorities when the first PSFCH resource and the second PSFCH resource are at least partially overlapped in the time domain.

3. The method of claim 2 , wherein dropping the another one of the first and second HARQ feedbacks with the lower priority comprises:

dropping a portion of HARQ bits of the another one of the first HARQ feedback and the second HARQ feedback with the lower priority when the PSFCH that is to be transmitted does not have enough resource size to include the HARQ bits of both of the first and second HARQ feedbacks.

4. The method of claim 1 , further comprising:

dropping a PSSCH transmission, a physical sidelink control channel (PSCCH) transmission, or a PSFCH transmission on other resources when the PSFCH that is to be transmitted has enough size to include the HARQ bits of both of the first and second HARQ feedbacks in the at least four slots after the first and second PSSCH transmissions, but is at least partially overlapped with one of a PSSCH, a PSCCH, or a PSFCH of the other resources.

5. The method of claim 1 , wherein transmitting the PSFCH for at least one of the first HARQ feedback and the second HARQ feedback with the higher priority comprises:

transmitting the PSFCH by overriding the first PSFCH resource with the second PSFCH resource when the first PSFCH resource and the second PSFCH resource are at least partially overlapped in the time domain, and the first PSSCH transmission is in a slot prior to a slot of the second PSFCH resource, wherein the first PSSCH transmission is prior to the second PSSCH transmission.

6. The method of claim 1 , wherein the transmitted PSFCH is selected according to the first and second PSFCH resources located on a subchannel with a lowest index, a subchannel with a smaller capacity for including sidelink feedback control information (SFCI), or a subchannel starting at earlier symbol of a slot.

7. The method of claim 1 , wherein transmitting the PSFCH for at least one of the first HARQ feedback and the second HARQ feedback with the higher priority comprises:

determining whether to transmit the PSFCH for at least one of the first HARQ feedback and the second HARQ feedback according to a PSFCH resource configuration indicated by one of master information block (MIB)-sidelink (SL), system information block (SIB), SIB-SL, radio resource control (RRC), SL-RRC, according to resource pool, bandwidth part (BWP), and anchor carrier; or

determining whether to transmit the PSFCH for at least one of the first HARQ feedback and the second HARQ feedback according to service types of the first and second PSSCH transmissions, wherein the service types are differentiated by at least one of a logical channel (LCH), a logical channel group identifier (LCG ID) of a transport block (TB)/data in a medium access control (MAC) configuration, and a priority indicator either in the first or second SCI.

8. A user equipment (UE) for determining one or more physical sidelink feedback channel (PSFCH) resources for hybrid automatic repeat request (HARQ) feedback, the UE comprising:

at least one processor for executing computer-executable instructions; and

at least one non-transitory machine-readable medium, coupled to the processor, for storing the computer-executable instructions, wherein the computer-executable instructions when executed by the at least one processor instruct the UE to:

receive, from a second UE, first sidelink control information (SCI) for scheduling a first unicast physical sidelink shared channel (PSSCH) transmission, the first SCI associated with a source identifier (ID);

receive, from the second UE, second SCI for scheduling a second unicast PSSCH transmission, the second SCI associated with the same source ID;

determine priorities of a first HARQ feedback corresponding to the first PSSCH transmission and a second HARQ feedback corresponding to the second PSSCH transmission according, respectively, to the first SCI and the second SCI; and

transmit, to the second UE, a PSFCH for at least one of the first HARQ feedback and the second HARQ feedback with a higher priority according to the determined priorities when a first PSFCH resource for the first HARQ feedback and a second PSFCH resource for the second HARQ feedback are at least partially overlapped in time domain, wherein transmitting the PSFCH comprises transmitting HARQ bits of both of the first and second HARQ feedbacks in the PSFCH when the PSFCH has enough resource size to include the HARQ bits of both of the first and second HARQ feedbacks in at least four slots after the first and second PSCCH transmissions.

9. The UE of claim 8 , wherein the computer-executable instructions when executed by the at least one processor further instruct the at least one processor to:

drop another one of the first HARQ feedback and the second HARQ feedback with a lower priority according to the determined priorities when the first PSFCH resource and the second PSFCH resource are at least partially overlapped in the time domain.

10. The UE of claim 9 , wherein dropping the another one of the first and second HARQ feedbacks with the lower priority comprises:

dropping a portion of HARQ bits of the another one of the first HARQ feedback and the second HARQ feedback with the lower priority when the PSFCH that is to be transmitted does not have enough resource size to include the HARQ bits of both of the first and second HARQ feedbacks.

11. The UE of claim 8 , wherein the computer-executable instructions when executed by the at least one processor further instruct the at least one processor to:

drop a PSSCH transmission, a physical sidelink control channel (PSCCH) transmission/reception, or a PSFCH transmission on other resources when the PSFCH that is to be transmitted has enough size to include the HARQ bits of both of the first and second HARQ feedbacks in the at least four slots after the first and second PSSCH transmissions, but is at least partially overlapped with one of a PSSCH, a PSCCH or a PSFCH of the other resources.

12. The UE of claim 8 , wherein transmitting the PSFCH for at least one of the first HARQ feedback and the second HARQ feedback with the higher priority comprises:

transmitting the PSFCH by overriding the first PSFCH resource with the second PSFCH resource when the first PSFCH resource and the second PSFCH resource are overlapped in the time domain, and the first PSSCH transmission is in a slot prior to a slot of the second PSFCH resource, wherein the first PSSCH transmission is prior to the second PSSCH transmission.

13. The UE of claim 8 , wherein the computer-executable instructions when executed by the at least one processor further instruct the at least one processor to:

select the transmitted PSFCH according to the first and second PSFCH resources located on a subchannel with a lowest index, a sub channel with a smaller capacity for including sidelink feedback control information (SFCI), or a subchannel starting at earlier symbol of a slot.

14. The UE of claim 8 , wherein transmitting the PSFCH for at least one of the first HARQ feedback and the second HARQ feedback with the higher priority comprises:

determine whether to transmit the PSFCH for at least one of the first HARQ feedback and the second HARQ feedback according to a PSFCH resource configuration indicated by one of master information block (MIB)-sidelink (SL), system information block (SIB), SIB-SL, radio resource control (RRC), SL-RRC according to resource pool, bandwidth part (BWP) and anchor carrier; or

determine whether to transmit the PSFCH for at least one of the first HARQ feedback and the second HARQ feedback according to service types of the first and second PSSCH transmissions, wherein the service types are differentiated by at least one of a logical channel (LCH), a logical channel group identifier (LCG ID) of a transport block (TB)/data in a medium access control (MAC) configuration, and a priority indicator in either the first or second SCI.