Quasi-co-location (QCL) indication for multi-transmission and reception point (TRP) enabled sidelink communications

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

determining at least one quasi-co-location (QCL) relationship between antenna ports of the transmitting sidelink UE, the at least one QCL relationship corresponding to carrier frequency offset (CFO), average delay, delay spread, Doppler shift, and/or Doppler spread across the antenna ports of the transmitting sidelink UE, each antenna port mapping to a different transmission and reception point (TRP) of a plurality of TRPs at different locations of the transmitting sidelink UE; and

indicating the at least one QCL relationship to a receiving sidelink UE either via sidelink control information (SCI), or during a radio resource control (RRC) connection setup procedure for a sidelink communications link established between the receiving sidelink UE and the transmitting sidelink UE, or during an RRC modification procedure for the sidelink communications link established between the receiving sidelink UE and the transmitting sidelink UE.

2. The method of claim 1 , further comprising determining the at least one QCL relationship based on preconfigured information about the plurality of TRPs.

3. The method of claim 1 , further comprising determining the at least one QCL relationship based on a velocity of the plurality of TRPs.

4. The method of claim 1 , further comprising determining the at least one QCL relationship based on sensor information and/or location information received from the receiving sidelink UE.

5. The method of claim 1 , further comprising:

updating the at least one QCL relationship in response to receiving, from the receiving sidelink UE, a negative acknowledgment (NACK) for a message; and

retransmitting the message with an updated at least one QCL relationship.

6. The method of claim 1 , further comprising:

receiving measurement reports from the receiving sidelink UE when a dedicated link exists between the receiving sidelink UE and the transmitting sidelink UE; and

determining the at least one QCL relationship based on the measurements.

7. The method of claim 6 , further comprising:

informing the receiving sidelink UE that the transmitting sidelink UE has multiple TRPs;

transmitting a first estimated QCL relationship; and

transmitting a list of reference signals for each antenna port to be measured,

in which the measurements comprise a channel quality report based on the list of reference signals and the estimated QCL relationship.

8. The method of claim 7 , further comprising transmitting a radio resource control (RRC) connection update with a second QCL estimate when the measurements indicate the first estimated QCL relationship was incorrect.

9. The method of claim 1 , further comprising:

receiving a report indicating the at least one QCL relationship is incorrect; and

sending a radio resource control (RRC) connection update message with a modified QCL relationship.

10. A method of wireless communication by a receiving sidelink user equipment (UE), comprising:

receiving a message from a plurality of transmission and reception points (TRPs) of a transmitting sidelink UE, the message indicating a quasi-co-location (QCL) assumption for the TRPs, each TRP having a different location on the transmitting sidelink UE;

measuring reference signals received from each transmission port of the plurality of TRPs, individually;

determining whether signaling from the plurality of TRPs satisfies all conditions for the QCL assumption; and

reporting to the transmitting sidelink UE a result of the determining.

11. The method of claim 10 , further comprising reporting to the transmitting sidelink UE via a channel state indication (CSI) parameter, the parameter indicating groups of the plurality of TRPs that are not consistent with the QCL assumption.

12. The method of claim 11 , in which the parameter indicates at least one reason why the groups are not consistent with the QCL assumption.

13. The method of claim 10 , further comprising receiving a modified QCL assumption based on the reporting.

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

at least one processor,

memory coupled with the at least one processor; and

instructions stored in the memory and operable, when executed by the at least one processor, to cause the apparatus:

to determine at least one quasi-co-location (QCL) relationship between antenna ports of the transmitting sidelink UE, the at least one QCL relationship corresponding to carrier frequency offset (CFO), average delay, delay spread, Doppler shift, and/or Doppler spread across the antenna ports of the transmitting sidelink UE, each antenna port mapping to a different transmission and reception point (TRP) of a plurality of TRPs at different locations of the transmitting sidelink UE; and

to indicate the at least one QCL relationship to a receiving sidelink UE either via sidelink control information (SCI), or during a radio resource control (RRC) connection setup procedure for a sidelink communications link established between the receiving sidelink UE and the transmitting sidelink UE, or during an RRC modification procedure for the sidelink communications link established between the receiving sidelink UE and the transmitting sidelink UE.

15. The apparatus of claim 14 , in which the at least one processor causes the apparatus to determine the at least one QCL relationship based on preconfigured information about the plurality of TRPs.

16. The apparatus of claim 14 , in which the at least one processor causes the apparatus to determine the at least one QCL relationship based on a velocity of the plurality of TRPs.

17. The apparatus of claim 14 , in which the at least one processor causes the apparatus to determine the at least one QCL relationship based on sensor information and/or location information received from the receiving sidelink UE.

18. The apparatus of claim 14 , in which the at least one processor causes the apparatus:

to update the at least one QCL relationship in response to receiving, from the receiving sidelink UE, a negative acknowledgment (NACK) for a message; and

to retransmit the message with an updated at least one QCL relationship.

19. The apparatus of claim 14 , in which the at least one processor causes the apparatus:

to receive measurement reports from the receiving sidelink UE when a dedicated link exists between the receiving sidelink UE and the transmitting sidelink UE; and

to determine the at least one QCL relationship based on the measurements.

20. The apparatus of claim 19 , in which the at least one processor causes the apparatus:

to inform the receiving sidelink UE that the transmitting sidelink UE has multiple TRPs;

to transmit a first estimated QCL relationship; and

to transmit a list of reference signals for each antenna port to be measured,

in which the measurements comprise a channel quality report based on the list of reference signals and the estimated QCL relationship.

21. The apparatus of claim 20 , in which the at least one processor causes the apparatus to transmit a radio resource control (RRC) connection update with a second QCL estimate when the measurements indicate the first estimated QCL relationship was incorrect.

22. The apparatus of claim 14 , in which the at least one processor causes the apparatus:

to receive a report indicating the at least one QCL relationship is incorrect; and

to send a radio resource control (RRC) connection update message with a modified QCL relationship.

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

at least one processor,

memory coupled with the at least one processor; and

instructions stored in the memory and operable, when executed by the at least one processor, to cause the apparatus:

to receive a message from a plurality of transmission and reception points (TRPs) of a transmitting sidelink UE, the message indicating a quasi-co-location (QCL) assumption for the TRPs, each TRP having a different location on the transmitting sidelink UE;

to measure reference signals received from each transmission port of the plurality of TRPs, individually;

to determine whether signaling from the plurality of TRPs satisfies all conditions for the QCL assumption; and

to report to the transmitting sidelink UE a result of the determining.

24. The apparatus of claim 23 , in which the at least one processor causes the apparatus to report to the transmitting sidelink UE via a channel state indication (CSI) parameter, the parameter indicating groups of the plurality of TRPs that are not consistent with the QCL assumption.

25. The apparatus of claim 24 , in which the parameter indicates at least one reason why the groups are not consistent with the QCL assumption.

26. The apparatus of claim 23 , in which the at least one processor causes the apparatus to receive a modified QCL assumption based on the reporting.