Method and apparatus for configuring DM-RS for V2X

1. 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:

determine, 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;

determine, 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;

determine, 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;

determine, 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

receive the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS.

2. The wireless user device 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 ) mod30, 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 ) mod30,

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 wireless user device 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 wireless user device of claim 1 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

receive, 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 wireless user device of claim 4 , 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].

6. The wireless user device of claim 1 , wherein the instructions, when executed by the one or more processors, cause the wireless user device to:

receive, from a second wireless user device, one or more physical sidelink shared channel (P S SCH) signals,

wherein at least one of the first DM-RS, the second DM-RS, the third DM-RS, or the fourth DM-RS is associated with the one or more PSSCH signals.

7. The wireless user device of claim 1 , 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).

8. The wireless user device 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 method performed by a wireless user device, the method comprising:

determining, 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;

determining, 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;

determining, 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;

determining, 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

receiving the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS.

10. The method 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 method 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 method of claim 9 , wherein the receiving the first DM-RS, the second DM-RS, the third DM-RS, and the fourth DM-RS comprises:

receiving, 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 method of claim 12 , 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].

14. The method of claim 9 , further comprising:

receiving, from a second wireless user device, one or more physical sidelink shared channel (PSSCH) signals,

wherein at least one of the first DM-RS, the second DM-RS, the third DM-RS, or the fourth DM-RS is associated with the one or more PSSCH signals.

15. The method of claim 9 , further comprising:

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

16. The method 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.