Cross-carrier sounding with aperiodic channel state information reference signals (CSI-RS)

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

receiving signaling on a first component carrier (CC) triggering an aperiodic channel state information reference signal (A-CSI-RS) transmission in a second CC and indicating triggering states for A-CSI-RS resources on each of the first and second CCs, wherein each trigger state indicates at least one of a triggering offset or transmit beams, only the first CC having an active search space;

monitoring for the A-CSI-RS in the second CC; and

transmitting at least one measurement report for the A-CSI-RS in the second CC.

2. The method of claim 1 , wherein the first and second CCs have different numerologies, each numerology defined by at least one of subcarrier spacing (SCS) or cyclic prefix (CP) length.

3. The method of claim 1 , further comprising receiving signaling pre-configuring the UE to monitor certain A-CSI-RS resources for each of the first and second CCs.

4. The method of claim 1 , wherein the signaling is received via a downlink control information (DCI).

5. The method of claim 4 , wherein the DCI is received on one of the first and second CCs.

6. The method of claim 4 , wherein the DCI indicates a grant of uplink resources for transmitting the measurement report via a physical uplink shared channel (PUSCH).

7. The method of claim 6 , wherein CSI-RS measurements for the first and second CCs are included in a single PUSCH transmission.

8. The method of claim 4 , wherein the DCI triggers multiple A-CSI-RS resource sets, each resource set associated with a cell index and comprising time and frequency resources to monitor for A-CSI-RS.

9. The method of claim 4 , wherein:

the DCI carries up to N triggering commands; and

positions of the N triggering commands is configured via radio resource control (RRC) signaling.

10. The method of claim 9 , wherein each triggering command indicates a trigger state of a corresponding A-CSI-RS resource set.

11. The method of claim 10 , wherein each trigger state indicates a transmission configuration information (TCI) state of the A-CSI-RS resources.

12. The method of claim 1 , further comprising receiving signaling activating a search space in one of the first and second CCs, selected based on the measurement report.

13. A method of wireless communications by a network entity, comprising:

transmitting signaling, to at least one user equipment (UE), on a first component carrier (CC) triggering an aperiodic channel state information reference signal (A-CSI-RS) transmission in a second CC and indicating triggering states for A-CSI-RS resources on each of the first and second CCs, wherein each trigger state indicates at least one of a triggering offset or transmit beams, only the first CC having an active search space;

transmitting the A-CSI-RS in the second CC; and

receiving, from the UE, at least one measurement report for the A-CSI-RS in the second CC.

14. The method of claim 13 , wherein the first and second CCs have different numerologies, each numerology defined by at least one of subcarrier spacing (SCS) or cyclic prefix (CP) length.

15. The method of claim 13 , further comprising transmitting signaling pre-configuring the UE to monitor certain A-CSI-RS resources for each of first and second CCs.

16. The method of claim 13 , wherein the signaling is transmitted via a downlink control information (DCI).

17. The method of claim 16 , wherein the DCI is transmitted on one of the first and second CCs.

18. The method of claim 16 , wherein the DCI indicates a grant of uplink resources for transmitting the measurement report via a physical uplink shared channel (PUSCH).

19. The method of claim 18 , wherein CSI-RS measurements for the first and second CCs are received in a single PUSCH transmission.

20. The method of claim 16 , wherein the DCI triggers multiple A-CSI-RS resource sets, each resource set associated with a cell index and comprising time and frequency resources to monitor for A-CSI-RS.

21. The method of claim 16 , wherein:

the DCI carries up to N triggering commands; and

positions of the N triggering commands is configured via radio resource control (RRC) signaling.

22. The method of claim 21 , wherein each triggering command indicates a trigger state of a corresponding A-CSI-RS resource set.

23. The method of claim 22 , wherein each trigger state indicates a transmission configuration information (TCI) state of the A-CSI-RS resources.

24. The method of claim 13 , further comprising:

selecting, based on the report, at least one CC for activating a search space; and

transmitting signaling activating the search space on the selected CC.

25. An apparatus for wireless communications by a user equipment (UE), comprising:

means for receiving signaling on a first component carrier (CC) triggering aperiodic channel state information reference signal (A-CSI-RS) transmission in a second CC and indicating triggering states for A-CSI-RS resources on each of the first and second CCs, wherein each trigger state indicates at least one of a triggering offset or transmit beams, only the first CC having an active search space;

means for monitoring for the A-CSI-RS in the second CC; and

means for transmitting at least one measurement report for the A-CSI-RS in the second CC.

26. An apparatus for wireless communications by a network entity, comprising:

means for transmitting signaling, to at least one user equipment (UE), on a first component carrier (CC) triggering an aperiodic channel state information reference signal (A-CSI-RS) transmission in a second CC and indicating triggering states for A-CSI-RS resources on each of the first and second CCs, wherein each trigger state indicates at least one of a triggering offset or transmit beams, only the first CC having an active search space;

means for transmitting the A-CSI-RS in the second CC; and

means for receiving, from the UE, at least one measurement report for the A-CSI-RS in the second CC.