Periodic resource reservation for serving aperiodic traffic over sidelink

1. An apparatus for wireless communication at a wireless device, comprising:

a memory; and

at least one processor coupled to the memory and configured to:

reserve a set of periodic resources for sidelink transmission, wherein the reserved set of periodic resources include reserved resources for sidelink control information (SCI) and reserved resources for data; and

transmit the SCI without a data transmission in a periodic resource for a period, wherein the SCI includes an indication that there is no data transmission associated with the SCI, wherein the indication is comprised in a first portion of the SCI that is transmitted on a physical sidelink control channel (PSCCH).

2. The apparatus of claim 1 , wherein the wireless device transmits the SCI without the data transmission in the period based on there being no data for transmission at the wireless device in the period.

3. The apparatus of claim 1 , wherein the indication is further comprised in a second portion of the SCI that is transmitted on a physical sidelink shared channel (PSSCH).

4. The apparatus of claim 1 , wherein the SCI does not reserve resources within the period and indicates a periodic reservation in a next period.

5. The apparatus of claim 1 , wherein the at least one processor is further configured to:

receive hybrid automatic repeat request (HARQ) feedback in response to the SCI.

6. The apparatus of claim 5 , wherein the HARQ feedback is received in a physical sidelink feedback channel (PSFCH) based on one or more of:

a starting sub-channel of the PSCCH in which the SCI is transmitted,

a slot comprising the PSCCH in which the SCI is transmitted,

a source identifier, or

a destination identifier.

7. The apparatus of claim 5 , wherein the HARQ feedback is based on the SCI being unicast.

8. The apparatus of claim 5 , wherein the HARQ feedback is based on a second part of the SCI being transmitted in a physical sidelink shared channel (PSSCH).

9. The apparatus of claim 1 , wherein the at least one processor is further configured to:

release remaining periodic resources in the set of periodic resources min response to the wireless device not having the data to transmit in a threshold number of consecutive periods.

10. The apparatus of claim 9 , wherein the wireless device releases the remaining periodic resources based on a codepoint transmitted in the SCI that corresponds to a release of a periodic reservation.

11. A method of wireless communication at a wireless device, comprising:

reserving a set of periodic resources for sidelink transmission, wherein the reserved set of periodic resources include reserved resources for sidelink control information (SCI) and reserved resources for data; and

transmitting the SCI without a data transmission in a periodic resource for a period, wherein the SCI includes an indication that there is no data transmission associated with the SCI, wherein the indication is comprised in a first portion of the SCI that is transmitted on a physical sidelink control channel (PSCCH).

12. The method of claim 11 , wherein the wireless device transmits the SCI without transmitting the data transmission in the period based on there being no data for transmission at the wireless device in the period.

13. The method of claim 11 , wherein the indication is further comprised in a second portion of the SCI that is transmitted on a physical sidelink shared channel (PSSCH).

14. The method of claim 11 , wherein the SCI does not reserve resources within the period and indicates a periodic reservation in a next period.

15. The method of claim 11 , further comprising:

receiving hybrid automatic repeat request (HARQ) feedback in response to the SCI.

16. The method of claim 15 , wherein the HARQ feedback is received in a physical sidelink feedback channel (PSFCH) based on one or more of:

a starting sub-channel of the PSCCH in which the SCI is transmitted,

a slot comprising the PSCCH in which the SCI is transmitted,

a source identifier, or

a destination identifier.

17. The method of claim 15 , wherein the HARQ feedback is received based on the SCI being unicast.

18. The method of claim 15 , wherein the HARQ feedback is received based on a second part of the SCI being transmitted in a physical sidelink shared channel (PSSCH).

19. The method of claim 11 , further comprising:

releasing remaining periodic resources in the set of periodic resources based on determining that the wireless device does not have the data to transmit in a threshold number of consecutive periods.

20. An apparatus for wireless communication at a first wireless device, comprising:

a memory; and

at least one processor coupled to the memory and configured to:

receive a reservation from a second wireless device for a set of periodic resources for sidelink transmission;

receive, from the second wireless device, sidelink control information (SCI) in a period of the set of periodic resources, the SCI including an indication that the SCI is not associated with a data transmission, wherein the indication is comprised in a first part of the SCI in a physical sidelink control channel (PSCCH); and

refrain from attempting to decode a second part of the SCI and the data transmission in response to receiving the indication in the first part of the SCI.

21. The apparatus of claim 20 , wherein the at least one processor is further configured to:

measure reference signal received power (RSRP) for the PSCCH that carries the SCI; and

determine whether a resource associated with the SCI is reserved based on the indication and the measured RSRP.

22. The apparatus of claim 20 , wherein the SCI does not reserve resources within the period and indicates a periodic reservation in a next period.

23. The apparatus of claim 20 , wherein the at least one processor is further configured to:

receive a release of remaining periodic resources in the set of periodic resources, the release being based on a codepoint in the SCI that corresponds to periodic reservation release.

24. The apparatus of claim 20 , wherein the at least one processor is further configured to:

transmit hybrid automatic repeat request (HARQ) feedback to the second wireless device in response to the SCI.

25. A method of wireless communication at a first wireless device, comprising:

receiving a reservation from a second wireless device for a set of periodic resources for sidelink transmission;

receiving, from the second wireless device, sidelink control information (SCI) in a period of the set of periodic resources, the SCI including an indication that the SCI is not associated with a data transmission, wherein the indication is comprised in a first part of the SCI in a physical sidelink control channel (PSCCH); and

refraining from attempting to decode a second part of the SCI and the data transmission in response to receiving the indication in the first part of the SCI.

26. The method of claim 25 , further comprising:

measuring reference signal received power (RSRP) for the PSCCH that carries the SCI; and

determining whether a resource associated with the SCI is reserved based on the indication and the measured RSRP.

27. The method of claim 25 , wherein the SCI does not reserve resources within the period and indicates a periodic reservation in a next period.

28. The method of claim 25 , further comprising:

receiving a release of remaining periodic resources in the set of periodic resources, the release being based on a codepoint in the SCI that corresponds to periodic reservation release.

29. The method of claim 25 , further comprising:

transmitting hybrid automatic repeat request (HARQ) feedback to the second wireless device in response to the SCI.