Methods and apparatus to facilitate cross-carrier beam association

1. A method of wireless communication at a user equipment (UE), comprising:

receiving an indication of a cross-carrier beam association associated with a first carrier and a second carrier different than the first carrier;

selecting a first subset of beams of a first set of beams based on measurements of a transmission received on the first carrier;

transmitting a message via a second subset of beams of a second set of beams, the second subset of beams corresponding to the first subset of beams based on the cross-carrier beam association, wherein:

the transmission is a synchronization signal block (SSB) of the first set of beams,

the message is a random access channel (RACH) message,

the indication further indicates the SSB of the first set of beams is associated with a RACH occasion (RO), and

the transmission comprises transmitting the RACH message via the second subset of beams at the RO; or

receiving on the first set of beams and the second set of beams based on an association between the first set of beams of the first carrier and a second set of beams of the second carrier, said association being based on the indication of the cross-carrier beam association.

2. The method of claim 1 , further comprising:

receiving SSBs via the second subset of beams;

measuring the received SSBs; and

refining beams in the second subset of beams based on the measurement associated with the received SSBs.

3. The method of claim 1 , wherein the first set of beams comprises a first quantity of beams and the second set of beams comprises a second quantity of beams that is a same quantity as the first quantity of beams or that is a different quantity than the first quantity of beams.

4. The method of claim 1 , wherein the first set of beams comprises N beams and the second set of beams comprises N*M beams.

5. The method of claim 1 , wherein the first carrier and the second carrier are inter-band carriers.

6. The method of claim 1 , wherein the first carrier is associated with a first frequency range and the second carrier is associated with a second frequency range that is a same frequency range as the first frequency range or that is a different frequency range than the second frequency range.

7. The method of claim 1 , wherein the first carrier and the second carrier are intra-band carriers.

8. The method of claim 1 , wherein each beam of the first set of beams is associated with a first beam width, wherein each beam of the second set of beams is associated with a second beam width, and wherein the second set of beams overlaps the first set of beams.

9. The method of claim 8 , wherein the second beam width is a same beam width as the first beam width or is a different beam width than the first beam width.

10. The method of claim 8 , wherein the second beam width is approximately equal to 1/M the first beam width.

11. The method of claim 1 , wherein the cross-carrier beam association between the first carrier and the second carrier is based on a quasi co-location (QCL) relationship of the first set of beams and the second set of beams.

12. The method of claim 1 , wherein the indication is received via system information (SI) or radio resource control (RRC) signaling.

13. The method of claim 1 , further comprising:

transmitting a capability indicating support of the cross-carrier beam association, wherein the indication is received, after the transmission of the capability, in a radio resource control (RRC) message.

14. A user equipment (UE), comprising:

a transceiver;

memory comprising instructions; and

at least one processor configured to execute the instructions to cause the UE to:

receive, via the transceiver, an indication of a cross-carrier beam association associated with a first carrier and a second carrier different than the first carrier;

determine an association between a first set of beams of the first carrier and a second set of beams of the second carrier based on the indication of the cross-carrier beam association;

select a first subset of beams of the first set of beams based on measurements of a transmission received on the first carrier;

transmit, via the transceiver, a message via a second subset of beams of the second set of beams, the second subset of beams corresponding to the first subset of beams based on the cross-carrier beam association, wherein:

the transmission is a synchronization signal block (SSB) of the first set of beams,

the message is a random access channel (RACH) message,

the indication further indicates the SSB of the first set of beams is associated with a RACH occasion (RO), and

the transmission comprises transmitting the RACH message via the second subset of beams at the RO; or

receive, via the transceiver, on the first set of beams and the second set of beams based on the determined association.

15. The UE of claim 14 , wherein the at least one processor is further configured to cause the UE to:

receive, via the transceiver and the second subset of beams, SSBs;

measure the received SSBs; and

refine beams in the second subset of beams based on the measurement associated with the received SSBs.

16. The UE of claim 14 , wherein the first set of beams comprises a first quantity of beams and the second set of beams comprises a second quantity of beams that is a same quantity as the first quantity of beams or that is a different quantity than the first quantity of beams.

17. A method of wireless communication at a base station, comprising:

transmitting an indication of a cross-carrier beam association between a first set of beams of a first carrier and a second set of beams of a second carrier, the first carrier being different than the second carrier;

transmitting a first set of transmissions via at least a first subset of beams of the first set of beams;

receiving a message via a second subset of beams of the second set of beams, wherein the first subset of beams is based on the first set of transmissions and the second subset of beams corresponds to the first subset of beams based on the cross-carrier beam association, wherein:

the reception is a synchronization signal block (SSB) of the first set of beams,

the message is a random access channel (RACH) message,

the indication further indicates that SSB of the first set of beams is associated with a RACH occasion (RO), and

the reception comprises receiving the RACH message via the second subset of beams at the RO; or

transmitting on the first set of beams and the second set of beams based on the cross-carrier beam association.

18. The method of claim 17 , wherein the first set of transmissions comprises a synchronization signal block (SSB) of the first set of beams and the message is a random access channel (RACH) message, wherein the indication further indicates that the SSB of the first set of beams is associated with a RACH occasion (RO), wherein receiving the message comprises, receiving the RACH message through the second subset of beams of the second set of beams at the RO.

19. The method of claim 17 , wherein the first set of beams comprises a first quantity of beams and the second set of beams comprises a second quantity of beams that is a same quantity as the first quantity of beams or that is a different quantity than the first quantity of beams.

20. The method of claim 17 , wherein the first set of beams comprises N beams and the second set of beams comprises N*M beams.

21. The method of claim 17 , wherein the first carrier and the second carrier are inter-band carriers.

22. The method of claim 17 , wherein the first carrier is associated with a first frequency range and the second carrier is associated with a second frequency range that is a same frequency range as the first frequency range or that is a different frequency range than the second frequency range.

23. The method of claim 17 , wherein the first carrier and the second carrier are intra-band carriers.

24. The method of claim 17 , wherein each beam of the first set of beams is associated with a first beam width, wherein each beam of the second set of beams is associated with a second beam width, and wherein the second set of beams overlaps the first set of beams.

25. The method of claim 24 , wherein the second beam width is a same beam width as the first beam width or is a different beam width than the first beam width.

26. The method of claim 24 , wherein the second beam width is approximately equal to 1/M the first beam width.

27. The method of claim 17 , wherein the cross-carrier beam association between the first carrier and the second carrier is based on a quasi co-location (QCL) relationship of the first set of beams and the second set of beams.

28. The method of claim 17 , wherein the indication is transmitted via system information (SI) or radio resource control (RRC) signaling.

29. The method of claim 17 , further comprising:

receiving a capability indicating support of the cross-carrier beam association, wherein the indication is transmitted, after the reception of the capability, in a radio resource control (RRC) message.

30. A base station, comprising:

a transceiver;

memory comprising instructions; and

at least one processor configured to execute the instructions to cause the base station to:

transmit, via the transceiver, an indication of a cross-carrier beam association between a first set of beams of a first carrier and a second set of beams of a second carrier, the first carrier being different than the second carrier;

transmit, via the transceiver, a first set of transmissions via at least a first subset of beams of the first set of beams;

receive, via the transceiver, a message via a second subset of beams of the second set of beams, wherein the first subset of beams is based on the first set of transmissions and the second subset of beams corresponds to the first subset of beams based on the cross-carrier beam association, wherein:

the reception is a synchronization signal block (SSB) of the first set of beams,

the message is a random access channel (RACH) message,

the indication further indicates that SSB of the first set of beams is associated with a RACH occasion (RO), and

the reception comprises receiving the RACH message via the second subset of beams at the RO; or

transmit, the transceiver, on the first set of beams and the second set of beams based on the cross-carrier beam association.