Timing advance granularity for uplink with different numerologies

1. A method for wireless communications by a user equipment (UE), comprising:

receiving configuration information indicating a reference bandwidth part (BWP) from a group of uplink BWPs having different numerologies, wherein the reference BWP comprises a BWP used for determining a granularity for any timing advance (TA) command;

receiving a TA command to be applied to an uplink transmission on a first BWP from the group of uplink BWPs;

determining a granularity for the TA command based on a numerology of the reference BWP; and

sending the uplink transmission on a second BWP from the group of uplink BWPs with timing adjusted based on the TA command and the determined granularity.

2. The method of claim 1 , wherein the first and second BWPs are the same BWP.

3. The method of claim 1 , wherein the group of uplink BWPs are part of a timing advance group (TAG).

4. The method of claim 1 , wherein the reference BWP is a BWP having a largest subcarrier spacing among active uplink BWPs.

5. The method of claim 1 , wherein the reference BWP is a BWP having a largest subcarrier spacing among configured BWPs.

6. The method of claim 1 , wherein the reference BWP is a BWP having a minimum TA granularity among BWPs in the group.

7. The method of claim 1 , wherein the reference BWP is associated with a default downlink BWP.

8. A method for wireless communications by a user equipment (UE), comprising:

receiving configuration information indicating a reference uplink carrier from a group of uplink carriers having different numerologies, wherein the reference uplink carrier comprises an uplink carrier used for determining a granularity for any timing advance (TA) command;

receiving a TA command to be applied to an uplink transmission on a first uplink carrier among the group of uplink carriers;

determining a granularity for the TA command based on a numerology of the reference uplink carrier; and

sending the uplink transmission on a second uplink carrier of the group of uplink carriers with timing adjusted based on the TA command and the determined granularity.

9. The method of claim 8 , wherein the first and second uplink carriers are the same uplink carrier.

10. The method of claim 8 , wherein the reference uplink carrier is an uplink carrier with a minimum TA granularity.

11. The method of claim 8 , wherein the reference uplink carrier is an uplink carrier with the largest subcarrier spacing.

12. The method of claim 8 , wherein the reference uplink carrier corresponds to an uplink carrier used for physical uplink control channel (PUCCH) transmission.

13. A method for wireless communications by a base station, comprising:

determining a granularity for a timing advance (TA) command based on a numerology of a reference bandwidth part (BWP) from a group of BWPs having different numerologies;

signaling, to a user equipment (UE), an identification of the reference BWP for determining a granularity of any TA command including the TA command;

setting a value for the TA command based on the determined granularity; and

sending the TA command to a UE to apply when sending an uplink transmission on one or more of the BWPs in the group.

14. The method of claim 13 , wherein the reference BWP is a BWP having a largest subcarrier spacing among active uplink BWPs.

15. The method of claim 13 , wherein the reference BWP is a BWP having a largest subcarrier spacing among configured BWPs.

16. The method of claim 13 , wherein the reference BWP is a BWP having a minimum TA granularity among BWPs in the TAG.

17. The method of claim 13 , wherein the reference BWP is associated with a default downlink BWP.

18. A method for wireless communications by a base station (BS), comprising:

determining, for each of one or more uplink carriers available for communications with a user equipment (UE), a numerology of the uplink carrier, wherein the one or more uplink carriers are associated with a same timing advance group (TAG);

signaling, to the UE, an indication of an uplink carrier of the one or more uplink carriers to be used as a reference uplink carrier for determining a granularity of any timing advance (TA) command;

determining a TA granularity for the one or more uplink carriers, based in part on the numerology of each uplink carrier; and

signaling a TA command based on the TA granularity to the UE.

19. The method of claim 18 , wherein the TA granularity is determined based on a maximum TA granularity of the uplink carriers.

20. The method of claim 18 , wherein the TA granularity is determined based on a minimum TA granularity of the uplink carriers.

21. The method of claim 18 , wherein the reference uplink carrier is an uplink carrier with the largest subcarrier spacing.

22. The method of claim 18 , wherein the TA configuration is determined based on one of the uplink carriers that is associated with a physical uplink control channel (PUCCH).

23. The method of claim 18 , wherein the TA configuration is based on one of the uplink carriers that is associated with a particular carrier index.

24. The method of claim 18 , further comprising:

determining, for each of the one or more uplink carriers, a numerology associated with one or more bandwidth parts of the uplink carrier, wherein the TA granularity is determined based on a numerology of at least one of the bandwidth parts.

25. The method of claim 24 , wherein the TA granularity is determined based at least in part on a maximum TA granularity of the bandwidth parts.

26. The method of claim 24 , wherein the TA granularity is determined based at least in part on a minimum TA granularity of the bandwidth parts.

27. The method of claim 18 , wherein determining the TA granularity comprises:

selecting one of the bandwidth parts to use as a reference; and

determining the TA granularity based on the selected bandwidth part.