Method and apparatus for configuring DM-RS for V2X

1. A method performed by a wireless user device, the method comprising:

mapping, based on a first group-hopping associated with a first time resource, a first demodulation-reference signal (DM-RS) in a first symbol in the first time resource;

mapping, based on a second group-hopping associated with the first time resource and with an offset, a second DM-RS in a second symbol in the first time resource, wherein the first group-hopping and the second group-hopping apply different inputs in a pseudo-random sequence;

mapping, based on a third group-hopping associated with a second time resource, a third DM-RS in a third symbol in the second time resource;

mapping, based on a fourth group-hopping associated with the second time resource and with an offset, a fourth DM-RS in a fourth symbol in the second time resource, wherein the third group-hopping and the fourth group-hopping apply different inputs in the pseudo-random sequence; and

transmitting, to a second wireless user device, the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS.

2. The method of claim 1 , wherein the first group-hopping and the third group-hopping are associated with (Σ i=0 7 c(16n ss PSSCH +i)·2 i )mod 30, and

wherein the second group-hopping and the fourth group-hopping are associated with (Σ i=0 7 c(16n ss PSSCH +8+i)·2 i )mod 30,

where c(x) denotes the pseudo-random sequence that is defined as a length-31 Gold sequence and n ss PSSCH denotes a current slot number in a subframe pool for sidelink, wherein the first time resource is a first slot of a subframe, and wherein the second time resource is a second slot of the subframe.

3. The method of claim 2 , wherein n ss PSSCH =k for the first slot of the subframe and n ss PSSCH =k+1 for the second slot of the subframe, where k is a non-negative integer.

4. The method of claim 1 , wherein the transmitting the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS comprises:

transmitting, using first orthogonal sequence [+1 +1 +1 +1] or second orthogonal sequence [+1 −1 +1 −1], the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS.

5. The method of claim 4 , further comprising:

determining, based on a modulo-2 operation of an identifier being equal to a first value, the first orthogonal sequence [+1 +1 +1 +1]; or

determining, based on a modulo-2 operation of the identifier being equal to a second value, the second orthogonal sequence [+1 −1 +1 −1].

6. The method of claim 1 , further comprising:

transmitting, to the second wireless user device, one or more physical sidelink shared channel (PSSCH) signals,

wherein the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS are associated with the one or more PSSCH signals.

7. The method of claim 1 , further comprising:

enabling a group-hopping for demodulation-reference signals (DM-RSs) associated with a physical sidelink shared channel (PSSCH).

8. The method of claim 1 ,

wherein each of the first time resource and the second time resource consists of seven symbols, respectively,

wherein the first time resource precedes the second time resource in a time axis,

wherein the first symbol in the first time resource is symbol #2 and the second symbol in the first time resource is symbol #5, the seven symbols in the first time resource being arranged from symbol #0 to symbol #6, and

wherein the third symbol in the second time resource is symbol #1 and the fourth symbol in the second time resource is symbol #4, the seven symbols in the second time resource being arranged from symbol #0 to symbol #6.

9. A wireless user device comprising:

one or more antennas;

one or more processors; and

memory storing instructions that, when executed by the one or more processors, cause the wireless user device to:

map, based on a first group-hopping associated with a first time resource, a first demodulation-reference signal (DM-RS) in a first symbol in the first time resource;

map, based on a second group-hopping associated with the first time resource and with an offset, a second DM-RS in a second symbol in the first time resource, wherein the first group-hopping and the second group-hopping apply different inputs in a pseudo-random sequence;

map, based on a third group-hopping associated with a second time resource, a third DM-RS in a third symbol in the second time resource;

map, based on a fourth group-hopping associated with the second time resource and with an offset, a fourth DM-RS in a fourth symbol in the second time resource, wherein the third group-hopping and the fourth group-hopping apply different inputs in the pseudo-random sequence; and

transmit, to a second wireless user device, the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS.

10. The wireless user device of claim 9 , wherein the first group-hopping and the third group-hopping are associated with (Σ i=0 7 c(16n ss PSSCH +i)·2 i )mod 30, and

wherein the second group-hopping and the fourth group-hopping are associated with (Σ i=0 7 c(16n ss PSSCH +8+i)·2 i )mod 30,

where c(x) denotes the pseudo-random sequence that is defined as a length-31 Gold sequence and n ss PSSCH denotes a current slot number in a subframe pool for sidelink, wherein the first time resource is a first slot of a subframe, and wherein the second time resource is a second slot of the subframe.

11. The wireless user device of claim 10 , wherein n ss PSSCH =k for the first slot of the subframe and n ss PSSCH =k+1 for the second slot of the subframe, where k is a non-negative integer.

12. The wireless user device of claim 9 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

transmit, using first orthogonal sequence [+1 +1 +1 +1] or second orthogonal sequence [+1 −1 +1 −1], the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS.

13. The wireless user device of claim 12 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

determine, based on a modulo-2 operation of an identifier being equal to a first value, the first orthogonal sequence [+1 +1 +1 +1]; or

determine, based on a modulo-2 operation of the identifier being equal to a second value, the second orthogonal sequence [+1 −1 +1 −1].

14. The wireless user device of claim 9 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

transmit, to the second wireless user device, one or more physical sidelink shared channel (PSSCH) signals,

wherein the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS are associated with the one or more PSSCH signals.

15. The wireless user device of claim 9 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

enable a group-hopping for demodulation-reference signals (DM-RSs) associated with a physical sidelink shared channel (PSSCH).

16. The wireless user device of claim 9 ,

wherein each of the first time resource and the second time resource consists of seven symbols, respectively,

wherein the first time resource precedes the second time resource in a time axis,

wherein the first symbol in the first time resource is symbol #2 and the second symbol in the first time resource is symbol #5, the seven symbols in the first time resource being arranged from symbol #0 to symbol #6, and

wherein the third symbol in the second time resource is symbol #1 and the fourth symbol in the second time resource is symbol #4, the seven symbols in the second time resource being arranged from symbol #0 to symbol #6.

17. A non-transitory computer-readable medium storing instructions that, when executed by one or more processors, cause a wireless user device to:

map, based on a first group-hopping associated with a first time resource, a first demodulation-reference signal (DM-RS) in a first symbol in the first time resource;

map, based on a second group-hopping associated with the first time resource and with an offset, a second DM-RS in a second symbol in the first time resource, wherein the first group-hopping and the second group-hopping apply different inputs in a pseudo-random sequence;

map, based on a third group-hopping associated with a second time resource, a third DM-RS in a third symbol in the second time resource;

map, based on a fourth group-hopping associated with the second time resource and with an offset, a fourth DM-RS in a fourth symbol in the second time resource, wherein the third group-hopping and the fourth group-hopping apply different inputs in the pseudo-random sequence; and

transmit, to a second wireless user device, the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS.

18. The non-transitory computer-readable medium of claim 17 , wherein the first group-hopping and the third group-hopping are associated with (Σ i=0 7 c(16n ss PSSCH +i)·2 i )mod 30, and

wherein the second group-hopping and the fourth group-hopping are associated with (Σ i=0 7 c(16n ss PSSCH +8+i)·2 i )mod 30,

where c(x) denotes the pseudo-random sequence that is defined as a length-31 Gold sequence and n ss PSSCH denotes a current slot number in a subframe pool for sidelink, wherein the first time resource is a first slot of a subframe, and wherein the second time resource is a second slot of the subframe.

19. The non-transitory computer-readable medium of claim 18 , wherein n ss PSSCH =k for the first slot of the subframe and n ss PSSCH =k+1 for the second slot of the subframe, where k is a non-negative integer.

20. The non-transitory computer-readable medium of claim 17 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

transmit, using first orthogonal sequence [+1 +1 +1 +1] or second orthogonal sequence [+1 −1 +1 −1], the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS.

21. The non-transitory computer-readable medium of claim 20 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

determine, based on a modulo-2 operation of an identifier being equal to a first value, the first orthogonal sequence [+1 +1 +1 +1]; or

determine, based on a modulo-2 operation of the identifier being equal to a second value, the second orthogonal sequence [+1 −1 +1 −1].

22. The non-transitory computer-readable medium of claim 17 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

transmit, to the second wireless user device, one or more physical sidelink shared channel (PSSCH) signals,

wherein the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS are associated with the one or more PSSCH signals.

23. The non-transitory computer-readable medium of claim 17 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

enable a group-hopping for demodulation-reference signals (DM-RSs) associated with a physical sidelink shared channel (PSSCH).

24. The non-transitory computer-readable medium of claim 17 ,

wherein each of the first time resource and the second time resource consists of seven symbols, respectively,

wherein the first time resource precedes the second time resource in a time axis,

wherein the first symbol in the first time resource is symbol #2 and the second symbol in the first time resource is symbol #5, the seven symbols in the first time resource being arranged from symbol #0 to symbol #6, and

wherein the third symbol in the second time resource is symbol #1 and the fourth symbol in the second time resource is symbol #4, the seven symbols in the second time resource being arranged from symbol #0 to symbol #6.