Method and apparatus for configuring DMRS in wireless communication system

1. A method comprising:

receiving, by a first user device, information of a demodulation reference signal (DMRS) for vehicle-to-everything (V2X) communication between user devices;

via a first orthogonal frequency division multiplexing (OFDM) symbol in a first time interval, receiving, by the first user device from a second user device, a first Physical Sidelink Control Channel (PSCCH) DMRS and a first Physical Sidelink Shared Channel (PSSCH) DMRS;

demodulating, based on the first PSCCH DMRS, a first PSCCH;

demodulating, based on the first PSSCH DMRS, a first PSSCH;

receiving, via a second OFDM symbol in the first time interval, a second PSCCH DMRS, wherein the second OFDM symbol immediately follows the first OFDM symbol; and

receiving, via one or more third OFDM symbols in the first time interval, one or more second PSSCH demodulation reference signals (DMRSs), wherein the second OFDM symbol precedes the one or more third OFDM symbols.

2. The method of claim 1 , further comprising:

receiving, via the first OFDM symbol in the first time interval, the first PSCCH and the first PSSCH,

wherein the first PSCCH DMRS and the first PSCCH are mapped in a first frequency band and in the first OFDM symbol, and

wherein the first PSSCH DMRS and the first PSSCH are mapped in a second frequency band and in the first OFDM symbol.

3. The method of claim 2 , further comprising:

receiving, via the second OFDM symbol in the first time interval, a second PSCCH,

wherein the second PSCCH DMRS and the second PSCCH are mapped in the first frequency band and in the second OFDM symbol.

4. The method of claim 1 , wherein the first time interval is a normal slot, and

wherein the normal slot consists of 14 OFDM symbols in a time axis.

5. The method of claim 1 , wherein the first time interval is a non-slot or a mini-slot, and

wherein the non-slot or the mini-slot consists of less than 14 OFDM symbols in a time axis.

6. The method of claim 1 , further comprising:

via a fourth OFDM symbol in a second time interval, receiving, by the first user device, a third PSCCH DMRS and a third PSSCH DMRS;

receiving, via a fifth OFDM symbol in the second time interval, a fourth PSCCH DMRS, wherein the fifth OFDM symbol immediately follows the fourth OFDM symbol; and

receiving, via one or more sixth OFDM symbols in the second time interval, one or more fourth PSSCH DMRSs, wherein the fifth OFDM symbol precedes the one or more sixth OFDM symbols.

7. The method of claim 1 , wherein the first PSCCH DMRS is received via a first frequency resource in the first OFDM symbol, and

wherein the first PSSCH DMRS is received via a second frequency resource in the first OFDM symbol.

8. The method of claim 7 , wherein a portion of the second frequency resource is configured in at least one of:

a frequency band lower than a frequency band of the first frequency resource; or

a frequency band higher than the frequency band of the first frequency resource.

9. The method of claim 1 , wherein no channel configured in the first time interval precedes the first OFDM symbol.

10. The method of claim 1 , further comprising determining, based on sidelink control information (SCI) identifier (ID) information comprised in the first PSCCH and the second PSCCH, the first PSSCH DMRS.

11. A method comprising:

transmitting, by a first user device, information of a demodulation reference signal (DMRS) for vehicle-to-everything (V2X) communication between user devices;

via a first orthogonal frequency division multiplexing (OFDM) symbol in a first time interval, transmitting, by the first user device to a second user device, a first Physical Sidelink Control Channel (PSCCH) DMRS and a first Physical Sidelink Shared Channel (PSSCH) DMRS, wherein the first PSCCH DMRS is for the second user device for demodulating a first PSCCH, and wherein the first PSSCH DMRS is for the second user device for demodulating a first PSSCH;

transmitting, via a second OFDM symbol in the first time interval, a second PSCCH DMRS, wherein the second OFDM symbol immediately follows the first OFDM symbol; and

transmitting, via one or more third OFDM symbols in the first time interval, one or more second PSSCH demodulation reference signals (DMRSs), wherein the second OFDM symbol precedes the one or more third OFDM symbols.

12. The method of claim 11 , further comprising:

transmitting, via the first OFDM symbol in the first time interval, the first PSCCH and the first PSSCH,

wherein the first PSCCH DMRS and the first PSCCH are mapped in a first frequency band and in the first OFDM symbol, and

wherein the first PSSCH DMRS and the first PSSCH are mapped in a second frequency band and in the first OFDM symbol.

13. The method of claim 12 , further comprising:

transmitting, via the second OFDM symbol in the first time interval, a second PSCCH,

wherein the second PSCCH DMRS and the second PSCCH are mapped in the first frequency band and in the second OFDM symbol.

14. The method of claim 11 , wherein the first time interval is a normal slot, and

wherein the normal slot consists of 14 OFDM symbols in a time axis.

15. The method of claim 11 , wherein the first time interval is a non-slot or a mini-slot, and

wherein the non-slot or the mini-slot consists of less than 14 OFDM symbols in a time axis.

16. The method of claim 11 , further comprising:

via a fourth OFDM symbol in a second time interval, transmitting, by the first user device, a third PSCCH DMRS and a third PSSCH DMRS;

transmitting, via a fifth OFDM symbol in the second time interval, a fourth PSCCH DMRS, wherein the fifth OFDM symbol immediately follows the fourth OFDM symbol; and

transmitting, via one or more sixth OFDM symbols in the second time interval, one or more fourth PSSCH DMRSs, wherein the fifth OFDM symbol precedes the one or more sixth OFDM symbols.

17. The method of claim 11 , wherein the first PSCCH DMRS is transmitted via a first frequency resource in the first OFDM symbol, and

wherein the first PSSCH DMRS is transmitted via a second frequency resource in the first OFDM symbol.

18. The method of claim 17 , wherein a portion of the second frequency resource is configured in at least one of:

a frequency band lower than a frequency band of the first frequency resource; or

a frequency band higher than the frequency band of the first frequency resource.

19. The method of claim 11 , wherein no channel configured in the first time interval precedes the first OFDM symbol.

20. The method of claim 11 , wherein the first PSCCH and the second PSCCH comprise sidelink control information (SCI) identifier (ID) information.

21. The method of claim 20 , further comprising generating, based on the SCI ID information, the first PSSCH DMRS.