Method and apparatus for sounding reference signal transmission on sidelink

1. An apparatus comprising a first user equipment, the apparatus further comprising:

a transceiver that:

receives a sidelink sounding reference signal configuration corresponding to a sounding reference signal (SRS) from a network equipment or a sidelink (SL) apparatus comprising a second user equipment;

in response to receiving the sidelink sounding reference signal configuration from the network equipment:

transmits the same sidelink sounding reference signal configuration received from the network equipment to the sidelink apparatus for the sidelink apparatus to be configured with the sidelink sounding reference signal configuration prior to receiving the sounding reference signal; and

transmits the sounding reference signal to the sidelink apparatus; and

in response to receiving the sidelink sounding reference signal configuration from the sidelink apparatus, transmits the sounding reference signal to the sidelink apparatus without transmitting the sidelink sounding reference signal configuration because the sidelink apparatus already is aware of the sidelink sounding reference signal configuration.

2. The apparatus according to claim 1 , wherein, the SRS is based on a SL SRS configuration which configures location information of the SRS in time-frequency domain.

3. The apparatus according to claim 2 , wherein the SL SRS configuration is obtained by one or more of the following: receiving the SL SRS configuration from a network equipment, pre-configuring the SL SRS configuration in the apparatus, determining the SL SRS configuration according to a resource pool for SL communication, and/or receiving the SL SRS configuration from another apparatus.

4. The apparatus according to claim 1 ,

wherein the transceiver:

periodically transmits the SRS on the SL.

5. The apparatus according to claim 1 ,

wherein the transceiver:

transmits indication information or receives the indication information corresponding to transmitting the SRS.

6. The apparatus according to claim 5 ,

wherein the transceiver:

receives trigger information from the network equipment, wherein the trigger information is carried on one or more of a physical downlink control channel and/or a higher layer signaling; and

transmits the indication information according to the trigger information.

7. The apparatus according to claim 1 , wherein the SRS is a single SRS or a set of SRS.

8. The apparatus according to claim 7 , wherein the set of SRS includes one or more subband SRS and/or one wideband SRS.

9. The apparatus according to claim 5 , wherein the indication information is carried on one or more of a physical sidelink control channel, a higher layer signaling and/or a physical sidelink discovery channel.

10. The apparatus according to claim 7 , wherein the indication information includes one bit field to indicate whether the SRS is transmitted or not.

11. The apparatus according to claim 7 , wherein the indication information includes at least one bits field to indicate which of SRS are transmitted.

12. The apparatus according to claim 7 , wherein the indication information includes at least one bits field to indicate which of SRS are transmitted in a bitmap manner.

13. An apparatus comprising a first user equipment, the apparatus further comprising:

a transceiver that:

receives a sidelink sounding reference signal configuration corresponding to a sounding reference signal (SRS) from a network equipment or a sidelink (SL) apparatus comprising a second user equipment;

in response to receiving the sidelink sounding reference signal configuration from the network equipment:

transmits the same sidelink sounding reference signal configuration received from the network equipment to the sidelink apparatus for the sidelink apparatus to be configured with the sidelink sounding reference signal configuration prior to receiving the sounding reference signal; and

receives the sounding reference signal from the sidelink apparatus; and

in response to receiving the sidelink sounding reference signal configuration from the sidelink apparatus, receives the sounding reference signal from the sidelink apparatus without transmitting the sidelink sounding reference signal configuration because the sidelink apparatus already is aware of the sidelink sounding reference signal configuration.

14. The apparatus according to claim 13 , wherein, the SRS is based on a SL SRS configuration which configures location information of the SRS in time-frequency domain.

15. The apparatus according to claim 14 , wherein the SL SRS configuration is obtained by one or more of the following: receiving the SL SRS configuration from a network equipment, pre-configuring the SL SRS configuration in the apparatus, determining the SL SRS configuration according to a resource pool for SL communication, and/or receiving the SL SRS configuration from another apparatus.

16. The apparatus according to claim 13 ,

wherein the transceiver:

periodically receives the SRS on the SL.

17. The apparatus according to claim 13 ,

wherein the transceiver:

transmits indication information or receives the indication information corresponding to receiving the SRS.

18. The apparatus according to claim 17 ,

wherein the transceiver that:

receives trigger information from the network equipment, wherein the trigger information is carried on one or more of a physical downlink control channel and/or a higher layer signaling; and

transmits the indication information according to the trigger information.

19. The apparatus according to claim 13 , wherein the SRS is a single SRS or a set of SRS.

20. The apparatus according to claim 19 , wherein the set of SRS includes one or more subband SRS and/or one wideband SRS.

21. The apparatus according to claim 17 , wherein the indication information is carried on one or more of a physical sidelink control channel, a higher layer signaling and/or a physical sidelink discovery channel.

22. The apparatus according to claim 20 , wherein the indication information includes one bit field to indicate whether the SRS is transmitted or not.

23. The apparatus according to claim 20 , wherein the indication information includes at least one bits field to indicate which of SRS are transmitted.

24. The apparatus according to claim 20 , wherein the indication information includes at least one bits field to indicate which of SRS are transmitted in a bitmap manner.

25. A method of a first user equipment, the method comprising:

receiving a sidelink sounding reference signal configuration corresponding to a sounding reference signal (SRS) from a network equipment or a sidelink (SL) apparatus comprising a second user equipment;

in response to receiving the sidelink sounding reference signal configuration from the network equipment:

transmitting the same sidelink sounding reference signal configuration received from the network equipment to the sidelink apparatus for the sidelink apparatus to be configured with the sidelink sounding reference signal configuration prior to receiving the sounding reference signal; and

transmitting the sounding reference signal to the sidelink apparatus; and

in response to receiving the sidelink sounding reference signal configuration from the sidelink apparatus, transmitting the sounding reference signal to the sidelink apparatus without transmitting the sidelink sounding reference signal configuration because the sidelink apparatus already is aware of the sidelink sounding reference signal configuration.

26. A method of a first user equipment, the method comprising:

receiving a sidelink sounding reference signal configuration corresponding to a sounding reference signal (SRS) from a network equipment or a sidelink (SL) apparatus comprising a second user equipment;

in response to receiving the sidelink sounding reference signal configuration from the network equipment:

transmitting the same sidelink sounding reference signal configuration received from the network equipment to the sidelink apparatus for the sidelink apparatus to be configured with the sidelink sounding reference signal configuration prior to receiving the sounding reference signal; and

receiving the sounding reference signal from the sidelink apparatus; and

in response to receiving the sidelink sounding reference signal configuration from the sidelink apparatus, receiving the sounding reference signal from the sidelink apparatus without transmitting the sidelink sounding reference signal configuration because the sidelink apparatus already is aware of the sidelink sounding reference signal configuration.