Method and device for determining sidelink transmit power in NR V2X

1. A method for performing wireless communication by a first device, the method comprising:

transmitting sidelink control information (SCI) to a second device through a physical sidelink control channel (PSCCH);

transmitting, to the second device through a physical sidelink shared channel (PSSCH), at least one demodulation reference signal (DMRS) for reference signal received power (RSRP) measurement;

obtaining reference signal power from transmit power layer-3 (L3) filtered using L3 filter coefficient information;

receiving, from the second device, information related to RSRP L3 filtered using L3 filter coefficient information;

obtaining a sidelink (SL) pathloss by subtracting the L3 filtered RSRP from the L3 filtered reference signal power; and

determining first transmit power based on the SL pathloss.

2. The method of claim 1 , wherein the L3 filter coefficient information used for the transmit power L3 filtering and the RSRP L3 filtering corresponds to a same filter coefficient value.

3. The method of claim 1 , wherein the information related to the L3 filtered RSRP is obtained by the second device.

4. The method of claim 1 , wherein the L3 filter coefficient information is configured for each resource pool.

5. The method of claim 1 , further comprising transmitting, to the second device, a PC5 radio resource control (RRC) message including information related to the L3 filter coefficient information.

6. The method of claim 1 , further comprising receiving, from the second device, a PC5 radio resource control (RRC) message including information related to the L3 filter coefficient information.

7. The method of claim 1 , wherein the determining the first transmit power based on the SL pathloss is based on a unicast communication being performed between the first device and the second device.

8. The method of claim 1 , wherein the determining the first transmit power based on the SL pathloss comprises:

obtaining a downlink (DL) pathloss between the first device and a base station,

wherein the first transmit power is determined based on a minimum value among (i) second transmit power obtained based on the SL pathloss and (ii) third transmit power obtained based on the DL pathloss.

9. The method of claim 1 , further comprising establishing a unicast connection with the second device.

10. The method of claim 1 , further comprising changing the first transmit power to fourth transmit power, based on a determination that the information related to the L3 filtered RSRP is invalid.

11. The method of claim 10 , wherein the fourth transmit power is maximum transmit power of the first device.

12. The method of claim 1 , further comprising changing the first transmit power to fourth transmit power, based on failure to receive the information related to the L3 filtered RSRP more than a threshold number of times.

13. The method of claim 1 , further comprising changing the first transmit power to fourth transmit power, based on accuracy of the information related to the L3 filtered RSRP not satisfying a configured criterion.

14. The method of claim 1 , further comprising changing the first transmit power to fourth transmit power, based on link quality between the first device and the second device not satisfying a configured criterion.

15. The method of claim 14 , wherein the fourth transmit power is determined based on at least one of a parameter related to open loop power control (OLPC) or a number of resource blocks (RBs) allocated to the first device, and

wherein the SL pathloss is not used for determining the fourth transmit power.

16. The method of claim 1 , wherein the first transmit power is time-varying.

17. A first device configured to perform wireless communication, the first device comprising:

one or more memories storing instructions;

one or more transceivers; and

one or more processors connected to the one or more memories and the one or more transceivers, wherein the one or more processors execute the instructions to:

transmit sidelink control information (SCI) to a second device through a physical sidelink control channel (PSCCH);

transmit, to the second device through a physical sidelink shared channel (PSSCH), at least one demodulation reference signal (DMRS) for reference signal received power (RSRP) measurement;

obtain reference signal power from transmit power layer-3 (L3) filtered using L3 filter coefficient information;

receive, from the second device, information related to RSRP L3 filtered using L3 filter coefficient information;

obtain a sidelink (SL) pathloss by subtracting the L3 filtered RSRP from the L3 filtered reference signal power; and

determine first transmit power based on the SL pathloss.

18. The first device of claim 17 , wherein the L3 filter coefficient information used for the transmit power L3 filtering and the RSRP L3 filtering corresponds to a same filter coefficient value.

19. An apparatus of a first user equipment (UE), the apparatus comprising:

one or more processors; and

one or more memories operably connected to the one or more processors and storing instructions, wherein the one or more processors execute the instructions to:

transmit sidelink control information (SCI) to a second UE through a physical sidelink control channel (PSCCH);

transmit, to the second UE through a physical sidelink shared channel (PSSCH), at least one demodulation reference signal (DMRS) for reference signal received power (RSRP) measurement;

obtain reference signal power from transmit power layer-3 (L3) filtered using L3 filter coefficient information;

receive, from the second UE, information related to RSRP L3 filtered using L3 filter coefficient information;

obtain a sidelink (SL) pathloss by subtracting the L3 filtered RSRP from the L3 filtered reference signal power; and

determine first transmit power based on the SL pathloss.

20. The apparatus of claim 19 , wherein the L3 filter coefficient information used for the transmit power L3 filtering and the RSRP L3 filtering corresponds to a same filter coefficient value.