Determining uplink default beam for multiple-input multiple-output (MIMO)
Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for determining a default uplink beam to use for at least one configured uplink resource before receiving an uplink beam configuration, such as in New Radio multi-input multi-output applications.
1. A method for wireless communications by a user equipment (UE), the method comprising:
determining a default uplink beam to use for a physical uplink shared channel (PUSCH) before receiving a radio resource control (RRC) configuration for an uplink transmission configuration indicator (TCI) state list;
using the default uplink beam for transmitting the PUSCH; and
deactivating the default uplink beam for the PUSCH in response to receipt of signaling that configures a single TCI state for a control resource set (CORESET) and with a field set to a value that indicates a TCI field is not present in a downlink control information (DCI).
2. The method of claim 1 , further comprising determining a default uplink beam to use for a sounding reference signal (SRS) or a physical uplink control channel (PUCCH).
3. The method of claim 1 , wherein determining the default uplink beam to use for the PUSCH comprises determining the default uplink beam that corresponds to a spatial domain transmission filter used for a message scheduled by a random access response (RAR) in an initial access or reconfiguration procedure.
4. The method of claim 1 , wherein the deactivating comprises deactivating:
the default uplink beam for the PUSCH only; or
a default beam for both a physical downlink shared channel (PDSCH) and the PUSCH.
5. The method of claim 1 , wherein the deactivating comprises jointly deactivates the default uplink beam and one or more default beams for one or more types of downlink and uplink resources.
6. The method of claim 1 , further comprising using a second default uplink beam for the PUSCH in response to deactivation of the default uplink beam for the PUSCH.
7. A method for wireless communications by a network entity, the method comprising:
determining a default uplink beam for a user equipment (UE) to use for a physical uplink shared channel (PUSCH) before the network entity sends the UE a radio resource control (RRC) configuration for an uplink transmission configuration indicator (TCI) state list;
processing transmissions from the UE sent on the PUSCH using the default uplink beam;
sending signaling to the UE that configures a single TCI state for a control resource set (CORESET) and with a field set to a value that indicates a TCI field is not present in a downlink control information (DCI); and
deactivating the default uplink beam for the PUSCH in response to receipt, from the UE, of an acknowledgment of the signaling.
8. The method of claim 7 , further comprising determining a default uplink beam for the UE to use for a sounding reference signal (SRS) or a physical uplink control channel (PUCCH).
9. The method of claim 7 , wherein determining the default uplink beam for the UE to use for the PUSCH comprises determining the default uplink beam that corresponds to a spatial domain transmission filter used for a message scheduled by a random access response (RAR) in an initial access or reconfiguration procedure.
10. The method of claim 7 , wherein the deactivating comprises deactivating:
the default uplink beam for the PUSCH only; or
a default beam for both a physical downlink shared channel (PDSCH) and the PUSCH.
11. The method of claim 7 , wherein the deactivating comprises jointly deactivates the default uplink beam and one or more default beams for multiple types of downlink and uplink resources.
12. The method of claim 9 , further comprising using a second default uplink beam for the PUSCH in response to deactivation of the default uplink beam for the PUSCH.
13. An apparatus for wireless communications by a user equipment (UE), the apparatus comprising:
means for determining a default uplink beam to use for a physical uplink shared channel (PUSCH) before receiving a radio resource control (RRC) configuration for an uplink transmission configuration indicator (TCI) state list; and
means for using the default uplink beam for transmitting the PUSCH; and
means for deactivating the default uplink beam for the PUSCH in response to receipt of signaling that configures a single TCI state for a control resource set (CORESET) and with a field set to a value that indicates a TCI field is not present in a downlink control information (DCI).
14. An apparatus for wireless communications by a network entity, the apparatus comprising:
means for determining a default uplink beam for a user equipment (UE) to use for a physical uplink shared channel (PUSCH) before the network entity sends the UE a radio resource control (RRC) configuration for an uplink transmission configuration indicator (TCI) state list;
means for processing transmissions from the UE sent on the PUSCH using the default uplink beam;
means for sending signaling to the UE that configures a single TCI state for a control resource set (CORESET) and with a field set to a value that indicates a TCI field is not present in a downlink control information (DCI); and
means for deactivating the default uplink beam for the PUSCH in response to receipt, from the UE, of an acknowledgment of the signaling.
15. An apparatus for wireless communications by a user equipment (UE), the apparatus comprising:
at least one processor and a memory configured to cause the apparatus to:
determine a default uplink beam to use for a physical uplink shared channel (PUSCH) before receiving a radio resource control (RRC) configuration for an uplink transmission configuration indicator (TCI) state list;
use the default uplink beam for transmitting the PUSCH; and
deactivate the default uplink beam for the PUSCH in response to receipt of signaling that configures a single TCI state for a control resource set (CORESET) and with a field set to a value that indicates a TCI field is not present in a downlink control information (DCI).
16. An apparatus for wireless communications by a network entity, the apparatus comprising:
at least one processor and a memory configured to cause the apparatus to:
determine a default uplink beam for a user equipment (UE) to use for a physical uplink shared channel (PUSCH) before the network entity sends the UE a radio resource control (RRC) configuration for an uplink transmission configuration indicator (TCI) state list;
process transmissions from the UE sent on the PUSCH using the default uplink beam;
send signaling to the UE that configures a single TCI state for a control resource set (CORESET) and with a field set to a value that indicates a TCI field is not present in a downlink control information (DCI); and
deactivate the default uplink beam for the PUSCH in response to receipt, from the UE, of an acknowledgment of the signaling.