Method and apparatus for power headroom report regarding multi-TRP in a wireless communication system

1. A method for a User Equipment (UE) in a wireless communication system, comprising:

receiving a configuration with a list of pathloss reference signals for an uplink Bandwidth Part (BWP) of a first serving cell with multiple transmission/reception points (TRPs) comprising at least a first TRP and a second TRP;

computing a first Power Headroom (PH) for the first TRP based on at least a first pathloss reference signal associated with a lowest pathloss reference signal Identity (ID) in the list;

computing a second PH for the second TRP based on at least a second pathloss reference signal associated with a second lowest pathloss reference signal ID in the list; and

transmitting information of the first PH and information of the second PH.

2. The method of claim 1 , wherein the UE performs multi-TRP Physical Uplink Shared Channel (PUSCH) associated with the first TRP and the second TRP.

3. The method of claim 1 , wherein the UE computes the first PH and the second PH based on at least a Downlink Control Information (DCI) received by the UE, wherein the DCI schedules at least one PUSCH transmission to the first TRP and/or the second TRP, and the DCI does not comprise a SRS Resource Indicator (SRI) field.

4. The method of claim 1 , wherein the UE computes the first PH based on at least a first closed loop index, and the UE computes the second PH based on at least a second closed loop index different than the first closed loop index.

5. The method of claim 1 , wherein the UE computes the first PH based on at least a first maximum power, and/or the UE computes the second PH based on at least a second maximum power.

6. The method of claim 5 , wherein the first maximum power is the same as or is different than the second maximum power, and/or the first maximum power is a first UE configured maximum output power or a first maximum reference power, and/or the second maximum power is a second UE configured maximum output power or a second maximum reference power.

7. The method of claim 1 , wherein the information of the first PH and the information of the second PH are indicated via a Medium Access Control (MAC) Control Element (CE).

8. The method of claim 1 , wherein at least one of the following occurs:

both the first PH and the second PH are based on real transmissions;

the first PH is based on a first real transmission and the second PH is based on a second reference format;

the first PH is based on a first reference format and the second PH is based on a second real transmission; or

both the first PH and the second PH are based on reference formats.

9. The method of claim 1 , wherein the lowest pathloss reference signal ID is 0 and the second lowest pathloss reference signal ID is 1.

10. The method of claim 1 , wherein:

the first TRP is associated with a first Sounding Reference Signal (SRS) resource set of the first cell; and

the second TRP is associated with a second SRS resource set of the first cell.

11. A User Equipment (UE) in a wireless communication system, comprising:

a memory; and

a processor operatively coupled to the memory, wherein the processor is configured to execute program code to:

receive a configuration with a list of pathloss reference signals for an uplink Bandwidth Part (BWP) of a first serving cell with multiple transmission/reception points (TRPs) comprising at least a first TRP and a second TRP;

compute a first Power Headroom (PH) for the first TRP based on at least a first pathloss reference signal associated with a lowest pathloss reference signal Identity (ID) in the list;

compute a second PH for the second TRP based on at least a second pathloss reference signal associated with a second lowest pathloss reference signal ID in the list; and

transmit information of the first PH and information of the second PH.

12. The UE of claim 11 , wherein the UE performs multi-TRP Physical Uplink Shared Channel (PUSCH) associated with the first TRP and the second TRP.

13. The UE of claim 11 , wherein the UE computes the first PH and the second PH based on at least a Downlink Control Information (DCI) received by the UE, wherein the DCI schedules at least one PUSCH transmission to the first TRP and/or the second TRP, and the DCI does not comprise a SRS Resource Indicator (SRI) field.

14. The UE of claim 11 , wherein the UE computes the first PH based on at least a first closed loop index, and the UE computes the second PH based on at least a second closed loop index different than the first closed loop index.

15. The UE of claim 11 , wherein the UE computes the first PH based on at least a first maximum power, and/or the UE computes the second PH based on at least a second maximum power.

16. The UE of claim 15 , wherein the first maximum power is the same as or is different than the second maximum power, and/or the first maximum power is a first UE configured maximum output power or a first maximum reference power, and/or the second maximum power is a second UE configured maximum output power or a second maximum reference power.

17. The UE of claim 11 , wherein the information of the first PH and the information of the second PH are indicated via a Medium Access Control (MAC) Control Element (CE).

18. The UE of claim 11 , wherein one of the following occurs:

both the first PH and the second PH are based on real transmissions;

the first PH is based on a first real transmission and the second PH is based on a second reference format;

the first PH is based on a first reference format and the second PH is based on a second real transmission; or

both the first PH and the second PH are based on reference formats.

19. The UE of claim 11 , wherein the lowest pathloss reference signal ID is 0 and the second lowest pathloss reference signal ID is 1.

20. The UE of claim 11 , wherein:

the first TRP is associated with a first Sounding Reference Signal (SRS) resource set of the first cell; and

the second TRP is associated with a second SRS resource set of the first cell.