Timing advance signaling in a physical downlink control channel

1. A method for wireless communication, comprising:

determining to synchronize timing with a network via a random access procedure;

transmitting a first random-access channel message associated with the random access procedure;

receiving, via a physical downlink control channel, a second random-access channel message associated with the random access procedure in response to the first random-access channel message, the second random-access channel message received via the physical downlink control channel comprising a timing advance command;

identifying the timing advance command in the second random-access channel message received via the physical downlink control channel based at least in part on the first random-access channel message; and

communicating based at least in part on identifying the timing advance command.

2. The method of claim 1 , wherein transmitting the first random-access channel message and receiving the second random-access channel message comprises:

transmitting, to a neighbor node, the first random-access channel message as a request for the timing advance command; and

receiving, from the neighbor node via the physical downlink control channel, the second random-access channel message, the second random-access channel message received via the physical downlink control channel comprising the timing advance command based at least in part on the first random-access channel message being transmitted as the request for the timing advance command.

3. The method of claim 2 , further comprising:

receiving an indication of dedicated random-access channel resources allocated for transmitting the first random-access channel message to the neighbor node; and

transmitting the first random-access channel message to the neighbor node on the dedicated random-access channel resources.

4. The method of claim 3 , wherein the second random-access channel message is scrambled using a random-access radio network temporary identifier (RA-RNTI).

5. The method of claim 2 , wherein the second random-access channel message is scrambled using a cell radio network temporary identifier (C-RNTI) specific to a wireless node.

6. The method of claim 2 , wherein the communicating is within an integrated access backhaul (IAB) network.

7. The method of claim 1 , wherein transmitting the first random-access channel message and receiving the second random-access channel message comprises:

transmitting the first random-access channel message to a node as part of a beam failure recovery (BFR) procedure; and

receiving, from the node via the physical downlink control channel, the second random-access channel message, the second random-access channel message received via the physical downlink control channel comprising the timing advance command based at least in part on the first random-access channel message being transmitted as part of a BFR procedure.

8. The method of claim 1 , wherein communicating based at least in part on identifying the timing advance command comprises:

identifying time synchronization using the timing advance command; and

communicating based at least in part on the time synchronization.

9. The method of claim 1 , wherein the first random-access channel message is transmitted as part of a contention-free random-access (CFRA) procedure or a contention-based random-access (CBRA) procedure.

10. The method of claim 1 , wherein the timing advance command comprises an absolute timing advance command or a relative timing advance command.

11. A method for wireless communication, comprising:

receiving a first random-access channel message associated with a determined random access procedure to synchronize timing;

identifying a timing advance command to transmit based at least in part on receiving the first random-access channel message;

transmitting the timing advance command in a second random-access channel message associated with the random access procedure via a physical downlink control channel based at least in part on the first random-access channel message; and

communicating based at least in part on the identified timing advance command.

12. The method of claim 11 , further comprising:

determining that the first random-access channel message is transmitted as a request for the timing advance command; and

transmitting the timing advance command in the second random-access channel message via the physical downlink control channel based at least in part on the first random-access channel message being transmitted as the request for the timing advance command.

13. The method of claim 12 , further comprising:

transmitting an indication of dedicated random-access channel resources allocated for transmitting the first random-access channel message; and

receiving the first random-access channel message on the dedicated random-access channel resources.

14. The method of claim 13 , wherein the second random-access channel message is scrambled using a random-access radio network temporary identifier (RA-RNTI).

15. The method of claim 12 , wherein the second random-access channel message is scrambled using a cell radio network temporary identifier (C-RNTI) specific to a user equipment (UE).

16. The method of claim 11 , further comprising:

receiving the first random-access channel message from a user equipment (UE) as part of a beam failure recovery (BFR) procedure; and

transmitting, to the UE, the timing advance command in the second random-access channel message via the physical downlink control channel based at least in part on the first random-access channel message being received as part of a BFR procedure.

17. The method of claim 11 , wherein the first random-access channel message is received as part of a contention-free random-access (CFRA) procedure or a contention-based random-access (CBRA) procedure.

18. The method of claim 11 , wherein the timing advance command comprises an absolute timing advance command or a relative timing advance command.

19. An apparatus for wireless communication, comprising: a processor, memory in electronic communication with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to:

determine to synchronize timing with a network via a random access procedure;

transmit a first random-access channel message associated with the random access procedure;

receive, via a physical downlink control channel, a second random-access channel message associated with the random access procedure in response to the first random-access channel message, the second random-access channel message received via the physical downlink control channel comprising a timing advance command;

identify the timing advance command in the second random-access channel message received via the physical downlink control channel based at least in part on the first random-access channel message; and

communicate based at least in part on identifying the timing advance command.

20. The apparatus of claim 19 , wherein the instructions to transmit the first random-access channel message and receiving the second random-access channel message are executable by the processor to cause the apparatus to:

transmit, to a neighbor node, the first random-access channel message as a request for the timing advance command; and

receive, from the neighbor node via the physical downlink control channel, the second random-access channel message, the second random-access channel message received via the physical downlink control channel comprising the timing advance command based at least in part on the first random-access channel message being transmitted as the request for the timing advance command.

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

receive an indication of dedicated random-access channel resources allocated for transmitting the first random-access channel message to the neighbor node; and

transmit the first random-access channel message to the neighbor node on the dedicated random-access channel resources.

22. The apparatus of claim 21 , wherein the second random-access channel message is scrambled using a random-access radio network temporary identifier (RA-RNTI).

23. The apparatus of claim 20 , wherein the second random-access channel message is scrambled using a cell radio network temporary identifier (C-RNTI) specific to a wireless node.

24. The apparatus of claim 20 , wherein the communicating is within an integrated access backhaul (IAB) network.

25. The apparatus of claim 19 , wherein the instructions to transmit the first random-access channel message and receiving the second random-access channel message are executable by the processor to cause the apparatus to:

transmit the first random-access channel message to a node as part of a beam failure recovery (BFR) procedure; and

receive, from the node, the second random-access channel message, the second random-access channel message received via the physical downlink control channel comprising the timing advance command based at least in part on the first random-access channel message being transmitted as part of a BFR procedure.

26. The apparatus of claim 19 , wherein the instructions to communicate based at least in part on identifying the timing advance command are executable by the processor to cause the apparatus to:

identify time synchronization using the timing advance command; and

communicate based at least in part on the time synchronization.

27. The apparatus of claim 19 , wherein the first random-access channel message is transmitted as part of a contention-free random-access (CFRA) procedure or a contention-based random-access (CBRA) procedure.

28. The apparatus of claim 19 , wherein the timing advance command comprises an absolute timing advance command or a relative timing advance command.

29. An apparatus for wireless communication, comprising: a processor, memory in electronic communication with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to:

receive a first random-access channel message associated with a determined random access procedure to synchronize timing;

identify a timing advance command to transmit based at least in part on receiving the first random-access channel message;

transmit the timing advance command in a second random-access channel message associated with the random access procedure via a physical downlink control channel based at least in part on the first random-access channel message; and

communicating based at least in part on the identified timing advance command.

30. The apparatus of claim 29 , wherein the instructions are further executable by the processor to cause the apparatus to:

determine that the first random-access channel message is transmitted as a request for the timing advance command; and

transmit the timing advance command in the second random-access channel message via the physical downlink control channel based at least in part on the first random-access channel message being transmitted as the request for the timing advance command.