Default quasi co-location assumption for cross carrier reference signal triggering

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

receiving, via a first component carrier, control information that triggers transmission of an aperiodic reference signal in a second component carrier;

receiving control signaling that indicates a plurality of configured transmission configuration indicator states for the second component carrier;

identifying a quasi co-location assumption for reception of the aperiodic reference signal in the second component carrier based at least in part on a control resource set not being configured for the second component carrier, the quasi co-location assumption corresponding to a first transmission configuration indicator state that has a lowest identifier in a set of identifiers that correspond to the plurality of configured transmission configuration indicator states; and

receiving the aperiodic reference signal of the second component carrier based at least in part on the quasi co-location assumption.

2. The method of claim 1 ,:

wherein the control signaling indicates one or more configured transmission configuration indicator states for a shared data channel of the second component carrier.

3. The method of claim 2 , further comprising:

receiving a control message that indicates that the first transmission configuration indicator state is an activated transmission configuration indicator state with the lowest identifier.

4. The method of claim 3 , wherein

the control message is a medium access control (MAC) control element (CE).

5. The method of claim 2 , wherein

the control signaling is radio resource control signaling that indicates the one or more configured transmission configuration indicator states.

6. The method of claim 1 , wherein the first transmission configuration indicator state is a latest activated transmission configuration indicator state of the plurality of configured transmission configuration indicator states.

7. The method of claim 1 , wherein receiving the control information comprises:

receiving, via the first component carrier having a first numerology, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that has a second numerology that differs from the first numerology.

8. The method of claim 1 , wherein receiving the control information comprises:

receiving, via the first component carrier that is a frequency range 1 (FR1) component carrier that has a first numerology, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that has a second numerology that differs from the first numerology.

9. The method of claim 1 , wherein receiving the control information comprises:

receiving, via the first component carrier that is a frequency range 2 (FR2) component carrier, or a frequency range 3 (FR3) component carrier, or a frequency range 4 (FR4) component carrier, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that is a frequency range 2 (FR2) component carrier, or a FR3 component carrier, or a FR4 component carrier.

10. The method of claim 1 , wherein receiving the control information comprises:

receiving, via the first component carrier, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that is a frequency range 2 (FR2) component carrier, or a frequency range 3 (FR3) component carrier, or a frequency range 4 (FR4) component carrier.

11. The method of claim 1 , wherein receiving the control information comprises:

receiving, via the first component carrier, the control information that is downlink control information that triggers transmission of the aperiodic reference signal in the second component carrier.

12. The method of claim 1 , further comprising:

generating a reference signal measurement for the aperiodic reference signal; and

transmitting a measurement report that indicates the reference signal measurement.

13. The method of claim 12 , further comprising:

deriving a channel metric that comprises one or more of delay spread, doppler spread, average delay, doppler shift, or any combination thereof, based at least in part on the reference signal measurement; and

decoding a shared data channel that uses the aperiodic reference signal as a quasi co-location source.

14. A method for wireless communications by a base station, comprising:

transmitting, via a first component carrier, control information that triggers transmission of a aperiodic reference signal in a second component carrier;

transmitting control signaling that indicates a plurality of configured transmission configuration indicator states for the second component carrier;

identifying a quasi co-location assumption for transmission of the aperiodic reference signal in the second component carrier based at least in part on a control resource set not being configured for a user equipment (UE) for the second component carrier, the quasi co-location assumption corresponding to a first transmission configuration indicator state that has a lowest identifier in a set of identifiers that correspond to the plurality of configured transmission configuration indicator states; and

transmitting an aperiodic reference signal via the second component carrier based at least in part on the quasi co-location assumption.

15. The method of claim 14 ,

wherein the control signaling indicates one or more configured transmission configuration indicator states for a shared data channel of the second component carrier.

16. The method of claim 15 , further comprising:

transmitting a control message that indicates that the first transmission configuration indicator state is an activated transmission configuration indicator state with the lowest identifier of a set of identifiers.

17. The method of claim 16 , wherein

the control message is a medium access control (MAC) control element (CE).

18. The method of claim 15 , wherein

the control signaling is radio resource control signaling that indicates the one or more configured transmission configuration indicator states.

19. The method of claim 14 , wherein transmitting the control information comprises:

transmitting, via the first component carrier having a first numerology, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that has a second numerology that differs from the first numerology.

20. The method of claim 14 , wherein transmitting the control information comprises:

transmitting, via the first component carrier that is a frequency range 1 (FR1) component carrier that has a first numerology, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that has a second numerology that differs from the first numerology.

21. The method of claim 14 , wherein transmitting the control information comprises:

transmitting, via the first component carrier that is a frequency range 2 (FR2) component carrier, or a frequency range 3 (FR3) component carrier, or a frequency range 4 (FR4) component carrier, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that is a FR2 component carrier, or a FR3 component carrier, or a FR4 component carrier.

22. The method of claim 14 , wherein transmitting the control information comprises:

transmitting, via the first component carrier, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that is a frequency range 2 (FR2) component carrier, or a frequency range 3 (FR3) component carrier, or a frequency range 4 (FR4) component carrier.

23. The method of claim 14 , wherein transmitting the control information comprises:

transmitting, via the first component carrier, the control information that is downlink control information that triggers transmission of the aperiodic reference signal in the second component carrier.

24. An apparatus for wireless communications by a 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, via a first component carrier, control information that triggers transmission of an aperiodic reference signal in a second component carrier;

receive control signaling that indicates a plurality of configured transmission configuration indicator states for the second component carrier;

identify a quasi co-location assumption for reception of the aperiodic reference signal in the second component carrier based at least in part on a control resource set not being configured for the second component carrier, the quasi co-location assumption corresponding to a first transmission configuration indicator state that has a lowest identifier in a set of identifiers that correspond to the plurality of configured transmission configuration indicator states; and

receive the aperiodic reference signal of the second component carrier based at least in part on the quasi co-location assumption.

25. The apparatus of claim 24 , wherein the instructions to receive the control information are further executable by the processor to cause the apparatus to:

receive, via the first component carrier having a first numerology, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that has a second numerology that differs from the first numerology.

26. The apparatus of claim 24 , wherein the instructions to receive the control information are further executable by the processor to cause the apparatus to:

receive, via the first component carrier that is a frequency range 1 (FR1) component carrier that has a first numerology, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that has a second numerology that differs from the first numerology.

27. The apparatus of claim 24 , wherein the instructions to receive the control information are further executable by the processor to cause the apparatus to:

receive, via the first component carrier that is a frequency range 2 (FR2) component carrier, or a frequency range 3 (FR3) component carrier, or a frequency range 4 (FR4) component carrier, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that is a FR2 component carrier, or a FR3 component carrier, or a FR4 component carrier.

28. The apparatus of claim 24 , wherein the instructions to receive the control information are further executable by the processor to cause the apparatus to:

receive, via the first component carrier, the control information that triggers transmission of the aperiodic reference signal in the second component carrier that is a frequency range 2 (FR2) component carrier, or a frequency range 3 (FR3) component carrier, or a frequency range 4 (FR4) component carrier.

29. The apparatus of claim 24 , wherein the instructions to receive the control information are further executable by the processor to cause the apparatus to:

receive, via the first component carrier, the control information that is downlink control information that triggers transmission of the aperiodic reference signal in the second component carrier.

30. An apparatus for wireless communications by 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, via a first component carrier, control information that triggers transmission of a aperiodic reference signal in a second component carrier;

transmit control signaling that indicates a plurality of configured transmission configuration indicator states for the second component carrier;

identify a quasi co-location assumption for transmission of the aperiodic reference signal in the second component carrier based at least in part on a control resource set not being configured for a user equipment (UE) for the second component carrier, the quasi co-location assumption corresponding to a first transmission configuration indicator state that has a lowest identifier in a set of identifiers that correspond to the plurality of configured transmission configuration indicator states; and

transmit an aperiodic reference signal via the second component carrier based at least in part on the quasi co-location assumption.