Physical channel structures for sidelink communication

1. A method, comprising:

receiving a physical sidelink shared channel (PSSCH) associated with a first two-stage sidelink control information (SCI) at a first user equipment (UE) from a second UE over a sidelink, the first two-stage SCI indicating a physical layer identity (L1-ID) of the second UE;

determining based on the L1-ID of the second UE a time-frequency resource for transmitting a physical sidelink feedback channel (PSFCH) carrying a hybrid automatic repeat request (HARQ) feedback corresponding to reception of the PSSCH;

transmitting the PSFCH with the determined time-frequency resource; and

transmitting from the first UE a second two-stage SCI, a 2nd-stage SCI of the second two-stage SCI being mapped to resources that are indicated by a 1st-stage SCI of the second two-stage SCI, wherein the resources are used for data transmission associated with the second two-stage SCI when there is the data transmission associated with the second two-stage SCI, and the resources are used for 2nd-stage SCI transmission when there is no data transmission associated with the second two-stage SCI.

2. The method of claim 1 , wherein transmission of the PSSCH from the second UE is a groupcast transmission or a unicast transmission.

3. The method of claim 1 , wherein

the second two-stage SCI includes a field indicating whether there is the data transmission associated with the second two-stage SCI.

4. The method of claim 3 , wherein the 1st-stage SCI of the second two-stage SCI indicates there is no data transmission associated with the second two-stage SCI.

5. The method of claim 1 , further comprising:

transmitting a second two-stage SCI in a groupcast transmission from the first UE, a 1st-stage or a 2nd-stage SCI of the second two-stage SCI indicating a transmission power of the first UE for the groupcast transmission.

6. The method of claim 1 , further comprising:

receiving a second two-stage SCI from a third UE performing a groupcast transmission, a 1st-stage or a 2nd-stage SCI of the second two-stage SCI indicating a transmission power of the third UE;

determining a pathloss for the groupcast transmission between the third UE and the first UE based on the indicated transmission power of the third UE; and

determining a transmission power for transmitting a PSFCH from the first UE to the third UE according to the determined pathloss.

7. The method of claim 1 , further comprising:

transmitting a PSSCH over a sidelink from the first UE using a resource scheduled by a base station serving the first UE;

receiving in a slot a HARQ feedback in a PSFCH corresponding to the transmitted PSSCH; and

forwarding the received HARQ feedback to the base station using a resource reserved for a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH), a timing of the reserved resource being the slot plus a configured time offset.

8. The method of claim 1 , further comprising:

receiving at the first UE multiple HARQ feedbacks from a third UE at a same slot corresponding to multiple sidelink transmissions from the first UE to the third UE; and

forwarding the multiple HARQ feedbacks to a base station in a resource reserved for a PUCCH or a PUSCH.

9. An apparatus, comprising circuitry configured to:

receive a physical sidelink shared channel (PSSCH) associated with a first two-stage sidelink control information (SCI) at a first user equipment (UE) from a second UE over a sidelink, the first two-stage SCI indicating a physical layer identity (L1-ID) of the second UE;

determine based on the L1-ID of the second UE a time-frequency resource for transmitting a physical sidelink feedback channel (PSFCH) carrying a hybrid automatic repeat request (HARQ) feedback corresponding to reception of the PSSCH;

transmit the PSFCH with the determined time-frequency resource; and

transmit from the first UE a second two-stage SCI, a 2nd-stage SCI of the second two-stage SCI being mapped to resources that are indicated by a 1st-stage SCI of the second two-stage SCI, wherein the resources are used for data transmission associated with the second two-stage SCI when there is the data transmission associated with the second two-stage SCI, and the resources are used for 2nd-stage SCI transmission when there is no data transmission associated with the second two-stage SCI.

10. The apparatus of claim 9 , wherein transmission of the PSSCH from the second UE is a groupcast transmission or a unicast transmission.

11. The apparatus of claim 9 , wherein

the second two-stage SCI includes a field indicating whether there is the data transmission associated with the second two-stage SCI.

12. The apparatus of claim 11 , wherein the 1st-stage SCI of the second two-stage SCI indicates there is no data transmission associated with the second two-stage SCI.

13. The apparatus of claim 9 , wherein the circuitry is further configured to:

transmit a second two-stage SCI in a groupcast transmission from the first UE, a 1st-stage or a 2nd-stage SCI of the second two-stage SCI indicating a transmission power of the first UE for the groupcast transmission.

14. The apparatus of claim 9 , wherein the circuitry is further configured to:

receive a second two-stage SCI from a third UE performing a groupcast transmission, a 1st-stage or a 2nd-stage SCI of the second two-stage SCI indicating a transmission power of the third UE;

determine a pathloss for the groupcast transmission between the third UE and the first UE based on the indicated transmission power of the third UE; and

determine a transmission power for transmitting a PSFCH from the first UE to the third UE according to the determined pathloss.

15. The apparatus of claim 9 , wherein the circuitry is further configured to:

transmit a PSSCH over a sidelink from the first UE using a resource scheduled by a base station serving the first UE;

receive in a slot a HARQ feedback in a PSFCH corresponding to the transmitted PSSCH; and

forward the received HARQ feedback to the base station using a resource reserved for a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH), a timing of the reserved resource being the slot plus a configured time offset.

16. The apparatus of claim 9 , wherein the circuitry is further configured to:

receive at the first UE multiple HARQ feedbacks from a third UE at a same slot corresponding to multiple sidelink transmissions from the first UE to the third UE; and

forward the multiple HARQ feedbacks to a base station in a resource reserved for a PUCCH or a PUSCH.

17. A non-transitory computer-readable medium storing instructions that, when executed by a processor, causing the processor to perform a method, the method comprising:

receiving a physical sidelink shared channel (PSSCH) associated with a first two-stage sidelink control information (SCI) at a first user equipment (UE) from a second UE over a sidelink, the first two-stage SCI indicating a physical layer identity (L1-ID) of the second UE;

determining based on the L1-ID of the second UE a time-frequency resource for transmitting a physical sidelink feedback channel (PSFCH) carrying a hybrid automatic repeat request (HARQ) feedback corresponding to reception of the PSSCH;

transmitting the PSFCH with the determined time-frequency resource; and

transmitting from the first UE a second two-stage SCI, a 2nd-stage SCI of the second two-stage SCI being mapped to resources that are indicated by a 1st-stage SCI of the second two-stage SCI, wherein the resources are used for data transmission associated with the second two-stage SCI when there is the data transmission associated with the second two-stage SCI, and the resources are used for 2nd-stage SCI transmission when there is no data transmission associated with the second two-stage SCI.

18. The non-transitory computer-readable medium of claim 17 , wherein transmission of the PSSCH from the second UE is a groupcast transmission or a unicast transmission.