Common beam as a default beam for aperiodic channel state information reference signals
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may identify a transmission configuration indicator (TCI) state that is associated with at least two signals or at least two communication channels. The UE may use the TCI state as the default beam to receive an aperiodic channel state information reference signal (CSI-RS) based at least in part on a scheduling offset between a scheduling downlink control information, which schedules the aperiodic CSI-RS, and a transmission time of the aperiodic CSI-RS being less than a beam switch latency threshold. Numerous other aspects are provided.
1. A method of wireless communication performed by a user equipment (UE), comprising:
identifying a transmission configuration indicator (TCI) state that is associated with at least two signals or at least two communication channels, wherein the TCI state is based at least in part on a control resource set associated with a bandwidth part for receiving an aperiodic channel state information reference signal (CSI-RS); and
using the TCI state as a default beam for receiving the aperiodic CSI-RS based at least in part on a scheduling offset between a scheduling downlink control information (DCI), which schedules the aperiodic CSI-RS, and a transmission time of the aperiodic CSI-RS being less than a beam switch latency threshold.
2. The method of claim 1 , wherein using the TCI state as the default beam is based at least in part on always using the TCI state as the default beam.
3. The method of claim 1 , wherein identifying the TCI state that is associated with the at least two signals or at least two communication channels comprises:
identifying the TCI state based at least in part on an implicit rule.
4. The method of claim 3 , further comprising:
receiving, from a base station, an indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs.
5. The method of claim 4 , wherein receiving the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs comprises:
receiving the indication via at least one of a DCI communication, a medium access control (MAC) control element (MAC-CE) communication, or a radio resource control (RRC) communication.
6. The method of claim 1 , wherein identifying the TCI state that is associated with the at least two signals or at least two communication channels comprises:
identifying the TCI state based at least in part on an explicit rule.
7. The method of claim 6 , further comprising:
receiving, from a base station, an indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs.
8. The method of claim 7 , wherein receiving the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs comprises:
receiving the indication via at least one of a DCI communication, a medium access control (MAC) control element (MAC-CE) communication, or a radio resource control (RRC) communication.
9. The method of claim 7 , wherein receiving the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs comprises:
receiving an indication of the TCI state and the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs in a same signal.
10. The method of claim 1 , wherein identifying the TCI state that is associated with at least two signals or at least two communication channels comprises:
identifying that the TCI state is to be used for a multiple transmit receive point (multi-TRP) configuration.
11. The method of claim 10 , wherein the TCI state to be used for the multi-TRP configuration is associated with a single beam or multiple beams.
12. The method of claim 10 , the TCI state, associated with a TRP of the multi-TRP configuration, is to be used as the default beam for aperiodic CSI-RSs associated with the TRP.
13. The method of claim 1 , further comprising:
receiving, from a base station, an indication that the TCI state is not to be used as the default beam for aperiodic CSI-RSs.
14. The method of claim 13 , further comprising:
determining another default beam for aperiodic CSI-RSs based at least in part on a quasi co-location assumption of flail the control resource set with a lowest identifier in a latest monitored slot of the bandwidth part, wherein the bandwidth part comprises an active downlink bandwidth part.
15. The method of claim 13 , further comprising:
determining that another TCI state, that was determined prior to identifying the TCI state, is to be used as a new default beam for aperiodic CSI-RSs.
16. The method of claim 1 , further comprising:
receiving the scheduling DCI which schedules the aperiodic CSI-RS, wherein the DCI indicates the transmission time of the aperiodic CSI-RS; and
determining that the scheduling offset between the scheduling DCI and the transmission time of the aperiodic CSI-RS is less than the beam switch latency threshold.
17. A method of wireless communication performed by a base station, comprising:
transmitting, to a user equipment (UE), an indication that a transmission configuration indicator (TCI) state, that is associated with at least two signals or at least two communication channels, is to be used as a default beam for aperiodic channel state information reference signals (CSI-RSs), wherein the TCI state is based at least in part on a control resource set associated with a bandwidth part for transmitting an aperiodic channel state information reference signal (CSI-RS); and
transmitting, to the UE, the aperiodic CSI-RS that is to be received by the UE using the TCI state as the default beam.
18. The method of claim 17 , further comprising:
transmitting, to the UE, a configuration indicating that the UE is to use the default beam for aperiodic CSI-RSs if a scheduling offset between a scheduling DCI and a transmission time of an aperiodic CSI-RS that is scheduled by the scheduling DCI is less than a beam switch latency threshold.
19. The method of claim 17 , wherein the TCI state is identified by the UE based at least in part on an implicit indication.
20. The method of claim 19 , wherein transmitting the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs comprises:
transmitting the indication via at least one of a DCI communication, a medium access control (MAC) control element (MAC-CE) communication, or a radio resource control (RRC) communication.
21. The method of claim 17 , further comprising:
transmitting, to the UE, an indication of the TCI state.
22. The method of claim 21 , wherein transmitting the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs comprises:
transmitting the indication via at least one of a DCI communication, a medium access control (MAC) control element (MAC-CE) communication, or a radio resource control (RRC) communication.
23. The method of claim 21 , wherein transmitting the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs comprises:
transmitting the indication of the TCI state and the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs in a same signal.
24. The method of claim 17 , further comprising:
determining that the TCI state is to be used for a multiple transmit receive point (multi-TRP) configuration.
25. The method of claim 24 , wherein transmitting the indication that the TCI state is to be used as the default beam for aperiodic CSI-RSs comprises:
transmitting, to the UE, an indication that the TCI state, associated with a TRP of the multi-TRP configuration, is to be used as the default beam for aperiodic CSI-RSs associated with the TRP.
26. The method of claim 17 , further comprising:
transmitting, to the UE, an indication that the TCI state is no longer to be used as the default beam.
27. A user equipment (UE) for wireless communication, comprising:
one or more memories; and
one or more processors, coupled to the one or more memories, configured to:
identify a transmission configuration indicator (TCI) state that is associated with at least two signals or at least two communication channels, wherein the TCI state is based at least in part on a control resource set associated with a bandwidth part for receiving an aperiodic channel state information reference signal (CSI-RS); and
use the TCI state as a default beam for receiving the aperiodic CSI-RS based at least in part on a scheduling offset between a scheduling downlink control information (DCI), which schedules the aperiodic CSI-RS, and a transmission time of the aperiodic CSI-RS being less than a beam switch latency threshold.
28. A base station for wireless communication, comprising: one or more memories; and
one or more processors, coupled to the one or more memories, configured to:
transmit, to a user equipment (UE), an indication that a transmission configuration indicator (TCI) state, that is associated with at least two signals or at least two communication channels, is to be used as a default beam for aperiodic channel state information reference signals (CSI-RSs), wherein the TCI state is based at least in part on a control resource set associated with a bandwidth part for transmitting an aperiodic channel state information reference signal (CSI-RS); and
transmit, to the UE, the aperiodic CSI-RS that is to be received by the UE using the TCI state as the default beam.