Demodulation reference signal design for vehicle-to-vehicle communication

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

determining a base demodulation reference signal (DM-RS) sequence associated with a control channel for vehicle-to-vehicle communication;

determining a DM-RS sequence based on the base DM-RS sequence based on an identity of the UE; and

transmitting a plurality of DM-RS symbols that use the same DM-RS sequence determined based on the identity of the UE in the control channel within the control channel in a transmission time interval (TTI) using the DM-RS sequence.

2. The method of claim 1 , wherein the control channel is a physical sidelink control channel (PSCCH).

3. The method of claim 1 , wherein the base DM-RS sequence is determined based on an index corresponding to the base DM-RS sequence received from a base station.

4. The method of claim 1 , wherein the base DM-RS sequence is determined based on a pre-configured index corresponding to the base DM-RS sequence.

5. The method of claim 1 , wherein the DM-RS sequence is determined based on the identity of the UE, wherein the identity of the UE is a Temporary Mobile Subscriber Identity (TMSI).

6. The method of claim 1 , wherein the plurality of DM-RS symbols include four DM-RS symbols.

7. The method of claim 6 , further comprising multiplying the plurality of DM-RS symbols by an orthogonal sequence of [1 1 1 1].

8. The method of claim 1 , wherein the DM-RS sequence is a cyclic-shifted version of the base DM-RS sequence.

9. The method of claim 8 , wherein the DM-RS sequence is selected from a subset of all cyclic-shifted versions of the base DM-RS sequence based on the identity of the UE.

10. The method of claim 9 , wherein a size of the subset is four.

11. An apparatus for wireless communication, the apparatus being a user equipment (UE), comprising:

a memory; and

at least one processor coupled to the memory and configured to:

determine a base demodulation reference signal (DM-RS) sequence associated with a control channel for vehicle-to-vehicle communication;

determine a DM-RS sequence based on the base DM-RS sequence based on an identity of the UE; and

transmit a plurality of DM-RS symbols that use the same DM-RS sequence determined based on the identity of the UE in the control channel within the control channel in a transmission time interval (TTI) using the DM-RS sequence.

12. The apparatus of claim 11 , wherein the at least one processor is further configured to determine the base DM-RS sequence based on one of an index corresponding to the base DM-RS sequence received from a base station, or a pre-configured index corresponding to the base DM-RS sequence retrieved from the memory.

13. The apparatus of claim 11 , wherein the DM-RS sequence is determined based on the identity of the UE, wherein the identity of the UE is a Temporary Mobile Sub scriber Identity (TMSI).

14. The apparatus of claim 11 , wherein the at least one processor is further configured to multiply the plurality of DM-RS symbols by an orthogonal sequence of [1 1 1 1].

15. The apparatus of claim 11 , wherein the DM-RS sequence is selected from a subset of all cyclic-shifted versions of the base DM-RS sequence based on the identity of the UE.

16. The apparatus of claim 15 , wherein a size of the subset is four.

17. A method of wireless communication of a user equipment (UE), comprising:

generating a plurality of demodulation reference signal (DM-RS) sequences, each DM-RS sequence being generated for a corresponding DM-RS symbol of a plurality of DM-RS symbols associated with a sidelink channel based on a DM-RS symbol number of the corresponding DM-RS symbol; and

transmitting the plurality of DM-RS symbols within a data channel in a transmission time interval (TTI) using the plurality of DM-RS sequences, wherein the DM-RS symbol number comprises a first index of the DM-RS symbol in reference to a frame, wherein the DM-RS symbol number is based on a subframe number and a second index of the DM-RS symbol within the TTI.

18. The method of claim 17 , wherein the plurality of DM-RS sequences are based on Zadoff-Chu sequences.

19. The method of claim 17 , wherein the data channel is a physical sidelink shared channel (PSSCH).

20. The method of claim 17 , wherein a total number of the plurality of DM-RS symbols is four.

21. The method of claim 20 , further comprising multiplying the plurality of DM-RS symbols by an orthogonal sequence of [1 1 1 1] when a scheduling assignment (SA) identifier transmitted in an associated control channel is an even number.

22. The method of claim 21 , further comprising multiplying the plurality of DM-RS symbols by an orthogonal sequence of [1 −1 1 −1] when the SA identifier is an odd number.

23. The method of claim 17 , wherein the DM-RS symbol number is based on 4*n_{ssf}{circumflex over ( )}{PSSCH}+i, wherein i indicates the index of the DM-RS symbol within the TTI and wherein n_{ssf}{circumflex over ( )}{PSSCH} comprises a subframe number modulo 10.

24. The method of claim 17 , wherein the sidelink channel comprises the data channel for vehicle-to-vehicle communication or device-to-device communication.

25. An apparatus for wireless communication, the apparatus being a user equipment (UE), comprising:

a memory; and

at least one processor coupled to the memory and configured to:

generate a plurality of demodulation reference signal (DM-RS) sequences, each DM-RS sequence being generated for a corresponding DM-RS symbol of a plurality of DM-RS symbols associated with a sidelink channel based on a DM-RS symbol number of the corresponding DM-RS symbol; and

transmit the plurality of DM-RS symbols within a data channel in a transmission time interval (TTI) using the plurality of DM-RS sequences, wherein the DM-RS symbol number comprises a first index of the DM-RS symbol in reference to a frame, wherein the DM-RS symbol number is based on a subframe number and a second index of the DM-RS symbol within the TTI.

26. The apparatus of claim 25 , wherein the plurality of DM-RS sequences are based on Zadoff-Chu sequences.

27. The apparatus of claim 25 , wherein the data channel is a physical sidelink shared channel (PSSCH).

28. The apparatus of claim 25 , wherein a total number of the plurality of DM-RS symbols is four.

29. The apparatus of claim 28 , wherein the at least one processor is further configured to multiply the plurality of DM-RS symbols by an orthogonal sequence of [1 1 1 1] when a scheduling assignment (SA) identifier transmitted in an associated control channel is an even number.

30. The apparatus of claim 29 , wherein the at least one processor is further configured to multiply the plurality of DM-RS symbols by an orthogonal sequence of [1 −1 1 −1] when the SA identifier is an odd number.

31. The apparatus of claim 25 , wherein the DM-RS symbol number is based on 4*n_{ssf}{circumflex over ( )}{PSSCH}+i, wherein i indicates the index of the DM-RS symbol within the TTI and wherein n_{ssf}{circumflex over ( )}{PSSCH} comprises a subframe number modulo 10.

32. The apparatus of claim 25 , wherein the sidelink channel comprises the data channel for vehicle-to-vehicle communication or device-to-device communication.