Default PUCCH and SRS beam determination

1. A method to determine a default beam for dedicated physical uplink control channel (PUCCH) and/or sounding reference signal (SRS) transmission in a component carrier (CC), comprising:

in response to determining that a serving base station has not configured spatial relationship information for a default beam for transmissions in the CC, determining whether a pathloss reference signal (RS) has been configured in the CC;

in response to determining that the pathloss RS has not been configured in the CC, determining whether any control resource sets (CORESETs) and/or transmission configuration indication (TCI) states for a physical downlink shared channel (PDSCH) in the CC have been configured; and

in response to determining that no CORESESTs and/or TCI states have been configured in the CC, determining the default beam for transmissions based, at least in part, on a beam used for a most recent PUSCH transmission in the CC, in a CC in a same band as the CC, in a same band group as the CC, in a same cell group as the CC, or in a same CC list group as the CC.

2. The method of claim 1 , further comprising:

in response to determining that the pathloss RS has been configured in the CC, determining the default beam for transmissions based, at least in part, on the pathloss RS.

3. The method of claim 2 ,

wherein determining the default beam for transmissions based, at least in part, on the pathloss RS comprises determining the default beam for transmissions based, at least in part, on a beam used for a first, last, or indicated pathloss RS in a pathloss RS list configured via radio resource control (RRC) signaling with the serving base station.

4. The method of claim 1 ,

wherein determining the default beam for transmissions comprises determining the default beam for transmissions based, at least in part, on a default physical downlink shared channel (PDSCH) beam or a CORESET beam configured in another CC.

5. The method of claim 1 ,

wherein determining the default beam for transmissions comprises determining the default beam for transmissions further based, at least in part, on a beam used for a most recent PRACH procedure in the CC, in a CC in a same band as the CC, in a same band group as the CC, in a same cell group as the CC, or in a same CC list group as the CC.

6. The method of claim 1 ,

wherein determining the default beam for transmissions comprises determining the default beam for transmissions further based, at least in part, on a beam used for a most recent SRS transmission in the CC, in a CC in a same band as the CC, in a same band group as the CC, in a same cell group as the CC, or in a same CC list group as the CC.

7. The method of claim 1 ,

wherein determining the default beam for transmissions comprises determining the default beam for transmissions further based, at least in part, on a beam used for a most recent PUCCH transmission in the CC, in a CC in a same band as the CC, in a same band group as the CC, in a same cell group as the CC, or in a same CC list group as the CC.

8. The method of claim 1 ,

wherein determining the default beam for transmissions comprises determining the default beam for transmissions further based, at least in part, on selection of a CC index from CCs within a same band as the CC, within a same band group as the CC, or within a same cell group as the CC.

9. The method of claim 1 , further comprising:

in response to determining that no CORESESTs and/or TCI states have been configured in the CC, determining a pathloss RS for power control for the dedicated PUCCH or SRS based, at least in part, on at least one of:

a downlink RS used to determine a default spatial relationship;

a synchronization signal block (SSB) associated with a most recent random-access channel (RACH) procedure in the CC, in a CC in a same band as the CC, in a CC in a same band group as the CC, or in a CC in a same cell group as the CC;

a pathloss RS used for a most recent transmission on a PUSCH in the CC, in a CC in a same band as the CC, in a CC in a same band group as the CC, or in a CC in a same cell group as the CC;

a pathloss RS used for a most recent transmission of a PUCCH in the CC, in a CC in a same band as the CC, in a CC in a same band group as the CC, or in a CC in a same cell group as the CC; or

a pathloss RS used for a most recent transmission of an SRS in the CC, in a CC in a same band as the CC, in a CC in a same band group as the CC, or in a CC in a same cell group as the CC.

10. The method of claim 1 , further comprising:

determining a change in a default spatial relationship; and

switching to a new pathloss RS one time slot after measuring a specified number of samples of the new pathloss RS after corresponding control signaling for a spatial relationship update takes effect.

11. An apparatus, comprising:

a memory; and

a processing element in communication with the memory, wherein the processing element is configured to:

in response to determining that a serving base station has not configured spatial relationship information for a default beam for transmissions in a component carrier (CC), determine whether a pathloss reference signal (RS) has been configured in the CC;

in response to determining that the pathloss RS has not been configured in the CC, determine whether any control resource sets (CORESETs) and/or transmission configuration indication (TCI) states for a physical downlink shared channel (PDSCH) in the CC have been configured; and

in response to determining that no CORESESTs and/or TCI states have been configured in the CC, determine the default beam for transmissions based, at least in part, on a beam used for a most recent PUSCH transmission in the CC, in a CC in a same band as the CC, in a same band group as the CC, in a same cell group as the CC, or in a same CC list group as the CC.

12. The apparatus of claim 11 ,

wherein the processing element is further configured to:

determine a change in a default spatial relationship; and

switch to a new pathloss RS one time slot after measuring a specified number of samples of the new pathloss RS after corresponding control signaling for a spatial relationship update takes effect.

13. The apparatus of claim 12 ,

wherein the specified number of samples is predefined via a standard, configured via higher layer signaling with the serving base station, or based on capabilities of the apparatus.

14. The apparatus of claim 11 ,

wherein the processing element is further configured to:

after determining the change in the default spatial relationship and prior to an effective time of the new pathloss RS, use a higher layer filtered reference signal received power (RSRP) based on a prior pathloss RS and/or a layer 1 (L1) RSRP based on the new pathloss RS for pathloss measurement.

15. The apparatus of claim 11 ,

wherein the processing element is further configured to:

in response to determining that the pathloss RS has been configured in the CC, determine the default beam for transmissions based, at least in part, on the pathloss RS.

16. A user equipment device (UE), comprising:

at least one antenna;

at least one radio, wherein the at least one radio is configured to perform cellular communication using at least one radio access technology (RAT);

one or more processors coupled to the at least one radio, wherein the one or more processors and the at least one radio are configured to perform voice and/or data communications;

wherein the one or more processors are configured to cause the UE to:

in response to determining that a base station serving the UE has not configured spatial relationship information for a default beam for transmissions in a component carrier (CC), determine whether a pathloss reference signal (RS) has been configured in the CC;

in response to determining that the pathloss RS has not been configured in the CC, determine whether any control resource sets (CORESETs) and/or transmission configuration indication (TCI) states for a physical downlink shared channel (PDSCH) in the CC have been configured; and

in response to determining that no CORESESTs and/or TCI states have been configured in the CC, determine the default beam for transmissions based, at least in part, on a beam used for a most recent PUSCH transmission in the CC, in a CC in a same band as the CC, in a same band group as the CC, in a same cell group as the CC, or in a same CC list group as the CC.

17. The UE of claim 16 ,

wherein the one or more processors are further configured to cause the UE to:

in response to determining that the pathloss RS has been configured in the CC, determine the default beam for transmissions based, at least in part, on the pathloss RS.

18. The UE of claim 17 ,

wherein, to determine the default beam for transmissions based, at least in part, on the pathloss RS, the one or more processors are further configured to cause the UE to determine the default beam for transmissions further based, at least in part, on a beam used for a first, last, or indicated pathloss RS in a pathloss RS list configured via radio resource control (RRC) signaling with the base station.

19. The UE of claim 16 ,

wherein the default beam for transmissions is determined further based, at least in part, on at least one of:

a default transmission beam in another CC;

a CC index;

a physical random-access channel (PRACH) procedure;

a physical uplink shared channel (PUSCH) transmission;

a sounding reference signal (SRS) transmission; or

a physical uplink control channel (PUCCH) transmission.

20. The UE of claim 16 ,

wherein the one or more processors are further configured to cause the UE to:

in response to determining that no CORESESTs and/or TCI states have been configured in the CC, determine a pathloss RS for power control for a dedicated physical uplink control channel (PUCCH) or a sounding reference signal (SRS) based, at least in part, on at least one of:

a downlink RS used to determine a default spatial relationship;

a synchronization signal block (SSB) associated with a most recent random-access channel (RACH) procedure in the CC, in a CC in a same band as the CC, in a CC in a same band group as the CC, or in a CC in a same cell group as the CC;

a pathloss RS used for a most recent transmission on a physical uplink shared channel (PUSCH) in the CC, in a CC in a same band as the CC, in a CC in a same band group as the CC, or in a CC in a same cell group as the CC;

a pathloss RS used for a most recent transmission of a physical uplink control channel (PUCCH) in the CC, in a CC in a same band as the CC, in a CC in a same band group as the CC, or in a CC in a same cell group as the CC; or

a pathloss RS used for a most recent transmission of an SRS in the CC, in a CC in a same band as the CC, in a CC in a same band group as the CC, or in a CC in a same cell group as the CC.