Random access for aerial user equipments in connected mode

1. An apparatus for wireless communications at a base station, comprising:

a processor;

memory coupled with the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to:

transmit an indication of a pre-compensation timing value for transmission of a random access message by an aerial user equipment (UE), the random access message being part of a random access procedure between the base station and the aerial UE, wherein the pre-compensation timing value is based at least in part on a location of the aerial UE; and

monitor a set of random access resources for the random access message based at least in part on the indication, the set of random access resources associated with the pre-compensation timing value and the aerial UE.

2. The apparatus of claim 1 , wherein the instructions to transmit the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

transmit the indication of the pre-compensation timing value for transmission of the random access message by the aerial UE, the random access message being part of the random access procedure between the base station and the aerial UE when the aerial UE is in a connected state.

3. The apparatus of claim 1 , wherein the instructions to transmit the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

transmit, to the aerial UE, the indication of the pre-compensation timing value via radio resource control signaling, a medium access control control element, or downlink control information, wherein the pre-compensation timing value is specific to the aerial UE.

4. The apparatus of claim 1 , wherein the instructions to transmit the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

transmit an index corresponding to the pre-compensation timing value for transmission of the random access message by the aerial UE.

5. The apparatus of claim 1 , wherein the instructions to transmit the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

transmit broadcast signaling indicating a plurality of zones and corresponding zone identifiers, wherein each zone of the plurality of zones is associated with a respective pre-compensation timing value for transmission of the random access message by the aerial UE.

6. The apparatus of claim 5 , wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, to the aerial UE and via a dedicated radio resource control message, an indication to activate a zone identifier for the aerial UE.

7. The apparatus of claim 5 , wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, to the aerial UE and via a medium access control control element or downlink control information, a bitmap to activate a zone identifier for the aerial UE.

8. The apparatus of claim 5 , wherein the instructions are further executable by the processor to cause the apparatus to:

maintain a list comprising the plurality of zones and the respective pre-compensation timing values based at least in part on one or more measurements associated with one or more aerial UEs.

9. The apparatus of claim 5 , wherein each pre-compensation timing value corresponds to a minimum value for pre-compensation for a respective zone for a random access preamble transmission.

10. The apparatus of claim 1 , wherein the instructions are further executable by the processor to cause the apparatus to:

receive a capability message from the aerial UE, the capability message indicating a capability of the aerial UE to measure the location of the aerial UE, to apply a pre-compensation timing value, or both.

11. The apparatus of claim 1 , wherein the instructions are further executable by the processor to cause the apparatus to:

transmit a second message of the random access procedure after monitoring the set of random access resources for the random access message, the second message indicating a timing pre-compensation of the random access message.

12. The apparatus of claim 1 , wherein the instructions to transmit the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

transmit signaling indicating a location of the base station via system information or dedicated radio resource control signaling.

13. The apparatus of claim 1 , wherein the instructions to transmit the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

transmit signaling configuring the aerial UE with a pre-compensation timing value offset.

14. The apparatus of claim 1 , wherein the instructions are further executable by the processor to cause the apparatus to:

receive, based at least in part on completion of the random access procedure, a report indicating the pre-compensation timing value determined or used by the aerial UE.

15. An apparatus for wireless communications at an aerial user equipment (UE), comprising:

a processor;

memory coupled with the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to:

receive an indication of a pre-compensation timing value for transmission of a random access message by the aerial UE, the random access message being part of a random access procedure between a base station and the aerial UE, wherein the pre-compensation timing value is based at least in part on a location of the aerial UE; and

transmit, based at least in part on receiving the indication, the random access message using a first random access resource of a set of random access resources associated with the pre-compensation timing value and the aerial UE.

16. The apparatus of claim 15 , wherein the instructions to receive the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

receive the indication of the pre-compensation timing value for transmission of the random access message by the aerial UE, the random access message being part of the random access procedure between the base station and the aerial UE when the aerial UE is in a connected state.

17. The apparatus of claim 15 , wherein the instructions to receive the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

receive signaling indicating a location of the base station via system information or dedicated radio resource control signaling; and

determine the pre-compensation timing value based at least in part on the location of the base station.

18. The apparatus of claim 15 , wherein the instructions to receive the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

receive signaling configuring the aerial UE with a pre-compensation timing value offset; and

determine the pre-compensation timing value based at least in part on the pre-compensation timing value offset.

19. The apparatus of claim 15 , wherein the instructions are further executable by the processor to cause the apparatus to:

determine the pre-compensation timing value based at least in part on the location of the base station and the location of the aerial UE.

20. The apparatus of claim 15 , wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, based at least in part on completion of the random access procedure, a report indicating the pre-compensation timing value determined by the aerial UE.

21. The apparatus of claim 15 , wherein the instructions are further executable by the processor to cause the apparatus to:

transmit the random access message using the pre-compensation timing value via a second random access resource of the set of random access resources based at least in part on the pre-compensation timing value being available at the aerial UE; and

transmit the random access message via a third random access resource of the set of random access resources based at least in part on the pre-compensation timing value being unavailable at the aerial UE.

22. The apparatus of claim 15 , wherein the instructions are further executable by the processor to cause the apparatus to:

transmit a capability message from the aerial UE, the capability message indicating a capability of the aerial UE to measure the location of the aerial UE, to apply a pre-compensation timing value, or both.

23. The apparatus of claim 15 , wherein the instructions to receive the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

receive, from the base station, the indication of the pre-compensation timing value via radio resource control signaling, a medium access control control element, or downlink control information, wherein the pre-compensation timing value is specific to the aerial UE.

24. The apparatus of claim 15 , wherein the instructions to receive the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

receive an index corresponding to the pre-compensation timing value for transmission of the random access message by the aerial UE.

25. The apparatus of claim 15 , wherein the instructions to receive the indication of the pre-compensation timing value are executable by the processor to cause the apparatus to:

receive broadcast signaling indicating a plurality of zones and corresponding zone identifiers, wherein each zone of the plurality of zones is associated with a respective pre-compensation timing value for transmission of the random access message by the aerial UE.

26. The apparatus of claim 25 , wherein the instructions are further executable by the processor to cause the apparatus to:

receive, from the base station and via a dedicated radio resource control message, an indication to activate a zone identifier for the aerial UE.

27. The apparatus of claim 25 , wherein the instructions are further executable by the processor to cause the apparatus to:

receive, from the base station and via a medium access control control element or downlink control information, a bitmap to activate a zone identifier for the aerial UE.

28. The apparatus of claim 25 , wherein each pre-compensation timing value corresponds to a minimum value for pre-compensation for a respective zone for a random access preamble transmission.

29. A method for wireless communications at a base station, comprising:

transmitting an indication of a pre-compensation timing value for transmission of a random access message by an aerial user equipment (UE), the random access message being part of a random access procedure between the base station and the aerial UE, wherein the pre-compensation timing value is based at least in part on a location of the aerial UE; and

monitoring a set of random access resources for the random access message based at least in part on the indication, the set of random access resources associated with the pre-compensation timing value and the aerial UE.

30. A method for wireless communications at an aerial user equipment (UE), comprising:

receiving an indication of a pre-compensation timing value for transmission of a random access message by the aerial UE, the random access message being part of a random access procedure between a base station and the aerial UE, wherein the pre-compensation timing value is based at least in part on a location of the aerial UE; and

transmitting, based at least in part on receiving the indication, the random access message using a first random access resource of a set of random access resources associated with the pre-compensation timing value and the aerial UE.