Random access channel transmission procedures in higher bands

1. A user equipment (UE) for wireless communication, comprising:

a memory; and

one or more processors coupled to the memory, wherein the one or more processors are configured to:

receive, from a network entity, initial timing advance information in a msg2 communication of a four-step random access channel (RACH) procedure based at least in part on a subcarrier spacing in a cell associated with the network entity;

transmit, to the network entity, a msg3 communication with an initial timing advance that is based at least in part on the initial timing advance information; and

receive, from the network entity and based at least in part on a detection failure corresponding to the msg3 communication, a retransmission of the msg2 communication including updated timing advance information configured to resolve a timing advance value between the UE and the network entity.

2. The UE of claim 1 , wherein the initial timing advance information indicates the initial timing advance to be used for the msg3 communication within a full symbol duration that is based at least in part on the subcarrier spacing, and wherein the updated timing advance information includes a non-negative integer value indicating a time to be added to the initial timing advance used for the msg3 communication based at least in part on the full symbol duration.

3. The UE of claim 1 , wherein the msg3 communication is detected according to multiple timing hypotheses including an aligned timing hypothesis based at least in part on the initial timing advance and one or more additional timing hypotheses that are based at least in part on one or more possible values for the timing advance value between the UE and the network entity.

4. The UE of claim 3 , wherein the one or more processors are further configured to:

transmit, to the network entity, a timing resolution reference signal prior to the msg3 communication, wherein an attempt to detect the msg3 communication according to the multiple timing hypotheses is based at least in part on timing information determined from the timing resolution reference signal.

5. The UE of claim 1 , wherein the updated timing advance information is first updated timing advance information, and

wherein the one or more processors are further configured to receive second updated timing advance information in a physical downlink control channel or a physical downlink shared channel associated with a msg4 communication of the four-step RACH procedure.

6. The UE of claim 1 , wherein the one or more processors, to receive the retransmission of the msg2 communication, are configured to receive the retransmission of the msg2 communication during a random access response window monitored by the UE for a duration that is based at least in part on a supported cell size associated with the network entity.

7. The UE of claim 1 , wherein the one or more processors, to receive the updated timing advance information, are configured to receive the updated timing advance information in a physical downlink control channel including downlink control information (DCI) triggering a retransmission of the msg3 communication.

8. The UE of claim 7 , wherein the updated timing advance information is indicated by an entry in a time domain resource assignment table or a hybrid automatic repeat request process identifier field of the DCI triggering the retransmission of the msg3 communication.

9. The UE of claim 1 , wherein the updated timing advance information is first updated timing advance information, wherein the initial timing advance information includes multiple timing advance commands and multiple resource allocations for the msg3 communication, wherein, to transmit the msg3 communication, the one or more processors are configured to transmit the msg3 communication in multiple repetitions based at least in part on the multiple timing advance commands and the multiple resource allocations for the msg3 communication, and wherein second updated timing advance information is explicitly or implicitly indicated in a msg4 communication of the four-step RACH procedure based at least in part on the multiple repetitions of the msg3 communication.

10. The UE of claim 1 , wherein the one or more processors are further configured to:

receive, from the network entity, random access configuration information including a first physical RACH (PRACH) numerology for a two-step RACH procedure and a second PRACH numerology for the four-step RACH procedure, wherein the first PRACH numerology is the same as a data numerology that is based at least in part on the subcarrier spacing in the cell associated with the network entity, and wherein the second PRACH numerology is smaller than the data numerology that is based at least in part on the subcarrier spacing in the cell associated with the network entity.

11. A network entity for wireless communication, comprising:

a memory; and

one or more processors coupled to the memory, wherein the one or more processors are configured to:

transmit, to a user equipment (UE), initial timing advance information in a msg2 communication of a four-step random access channel (RACH) procedure based at least in part on a subcarrier spacing in a cell associated with the network entity;

transmit, to the UE and based at least in part on a failure to detect a msg3 communication, a retransmission of the msg2 communication including updated timing advance information configured to resolve a timing advance value between the UE and the network entity; and

receive, from the UE, the msg3 communication with a timing advance that is based at least in part on the updated timing advance information.

12. The network entity of claim 11 , wherein the initial timing advance information indicates an initial timing advance to be used for the msg3 communication within a full symbol duration that is based at least in part on the subcarrier spacing, and wherein the updated timing advance information includes a non-negative integer value indicating a time to be added to the initial timing advance used for the msg3 communication based at least in part on the full symbol duration.

13. The network entity of claim 11 , wherein the one or more processors are further configured to:

detect the msg3 communication according to multiple timing hypotheses including an aligned timing hypothesis based at least in part on the timing advance and one or more additional timing hypotheses that are based at least in part on one or more possible values for the timing advance value between the UE and the network entity.

14. The network entity of claim 13 , wherein the one or more processors are further configured to:

receive, from the UE, a timing resolution reference signal prior to the msg3 communication; and

attempt to detect the msg3 communication according to the multiple timing hypotheses based at least in part on timing information determined from the timing resolution reference signal.

15. The network entity of claim 11 , wherein the updated timing advance information is first updated timing advance information, and

wherein the one or more processors are further configured to transmit second updated timing advance information in a physical downlink control channel or a physical downlink shared channel associated with a msg4 communication of the four-step RACH procedure.

16. The network entity of claim 11 , wherein the one or more processors, to transmit the retransmission of the msg2 communication, are configured to transmit the retransmission of the msg2 communication during a random access response window monitored by the UE for a duration that is based at least in part on a supported cell size associated with the network entity.

17. The network entity of claim 11 , wherein, the one or more processors, to transmit the updated timing advance information, are configured to transmit the updated timing advance information in a physical downlink control channel including downlink control information (DCI) triggering a retransmission of the msg3 communication.

18. The network entity of claim 17 , wherein the updated timing advance information is indicated by an entry in a time domain resource assignment table or a hybrid automatic repeat request process identifier field of the DCI triggering the retransmission of the msg3 communication.

19. The network entity of claim 11 , wherein the updated timing advance information is first updated timing advance information, wherein the initial timing advance information includes multiple timing advance commands and multiple resource allocations for the msg3 communication, wherein the one or more processors, to receive the msg3 communication, are configured to receive the msg3 communication in multiple repetitions based at least in part on the multiple timing advance commands and the multiple resource allocations for the msg3 communication, and wherein second updated timing advance information is explicitly or implicitly indicated in a msg4 communication of the four-step RACH procedure based at least in part on the multiple repetitions of the msg3 communication.

20. The network entity of claim 11 , wherein the one or more processors are further configured to:

transmit, to the UE, random access configuration information including a first physical RACH (PRACH) numerology for a two-step RACH procedure and a second PRACH numerology for the four-step RACH procedure, wherein the first PRACH numerology is the same as a data numerology that is based at least in part on the subcarrier spacing in the cell associated with the network entity, and wherein the second PRACH numerology is smaller than the data numerology that is based at least in part on the subcarrier spacing in the cell associated with the network entity.

21. A method of wireless communication performed by a user equipment (UE), comprising:

receiving, from a network entity, initial timing advance information in a msg2 communication of a four-step random access channel (RACH) procedure based at least in part on a subcarrier spacing in a cell associated with the network entity;

transmitting, to the network entity, a msg3 communication with an initial timing advance that is based at least in part on the initial timing advance information; and

receiving, from the network entity and based at least in part on a detection failure corresponding to the msg3 communication, a retransmission of the msg2 communication including updated timing advance information resolving a timing advance value between the UE and the network entity.

22. The method of claim 21 , wherein the initial timing advance information indicates the initial timing advance to be used for the msg3 communication within a full symbol duration that is based at least in part on the subcarrier spacing, and wherein the updated timing advance information includes a non-negative integer value indicating a time to be added to the initial timing advance used for the msg3 communication based at least in part on the full symbol duration.

23. The method of claim 21 , wherein the retransmission of the msg2 communication is received during a random access response window monitored by the UE for a duration that is based at least in part on a supported cell size associated with the network entity.

24. The method of claim 21 , wherein the updated timing advance information is received in a physical downlink control channel including downlink control information triggering a retransmission of the msg3 communication.

25. The method of claim 21 , wherein the updated timing advance information is first updated timing advance information, wherein the initial timing advance information includes multiple timing advance commands and multiple resource allocations for the msg3 communication, wherein the msg3 communication is transmitted in multiple repetitions based at least in part on the multiple timing advance commands and the multiple resource allocations for the msg3 communication, and wherein second updated timing advance information is explicitly or implicitly indicated in a msg4 communication of the four-step RACH procedure based at least in part on the multiple repetitions of the msg3 communication.

26. A method of wireless communication performed by a network entity, comprising:

transmitting, to a user equipment (UE), initial timing advance information in a msg2 communication of a four-step random access channel (RACH) procedure based at least in part on a subcarrier spacing in a cell associated with the network entity;

transmitting, to the UE and based at least in part on the network entity failing to detect a msg3 communication, a retransmission of the msg2 communication including updated timing advance information resolving a timing advance value between the UE and the network entity; and

receiving, from the UE, the msg3 communication with a timing advance that is based at least in part on the updated timing advance information.

27. The method of claim 26 , comprising:

detecting the msg3 communication according to multiple timing hypotheses including an aligned timing hypothesis based at least in part on the initial timing advance and one or more additional timing hypotheses that are based at least in part on one or more possible values for the timing advance value between the UE and the network entity.

28. The method of claim 26 , wherein the retransmission of the msg2 communication is transmitted during a random access response window monitored by the UE for a duration that is based at least in part on a supported cell size associated with the network entity.

29. The method of claim 26 , wherein the updated timing advance information is transmitted in a physical downlink control channel including downlink control information triggering a retransmission of the msg3 communication.

30. The method of claim 26 , wherein the updated timing advance information is first updated timing advance information, wherein the initial timing advance information includes multiple timing advance commands and multiple resource allocations for the msg3 communication, wherein the msg3 communication is received in multiple repetitions based at least in part on the multiple timing advance commands and the multiple resource allocations for the msg3 communication, and wherein second updated timing advance information is explicitly or implicitly indicated in a msg4 communication of the four-step RACH procedure based at least in part on the multiple repetitions of the msg3 communication.