Method and apparatus for configuring DM-RS for V2X

1. A method for transmitting Demodulation-Reference Signal (DM-RS) configured for Vehicle-to-everything (V2X) communication, the method comprising:

determining, based on a first group-hopping associated with a first slot of a subframe, a first DM-RS for V2X communication, and generating, based on a second group-hopping associated with the first slot and with an offset, a second DM-RS for V2X communication, wherein the first group-hopping and the second group-hopping apply different inputs in a pseudo-random sequence;

mapping the first DM-RS for V2X communication in a first symbol in the first slot of the subframe, and mapping the second DM-RS for V2X communication in a second symbol in the first slot of the subframe;

determining, based on a third group-hopping associated with a second slot of the subframe, a third DM-RS for V2X communication, and generating, based on a fourth group-hopping associated with the second slot and with an offset, a fourth DM-RS for V2X communication, wherein the third group-hopping and the fourth group-hopping apply different inputs in the pseudo-random sequence;

mapping the third DM-RS for V2X communication in a first symbol in the second slot of the subframe, and mapping the fourth DM-RS for V2X communication in a second symbol in the second slot of the subframe; and

transmitting the mapped first DM-RS for V2X communication, the mapped second DM-RS for V2X communication, the mapped third DM-RS for V2X communication, and the mapped fourth DM-RS for V2X communication.

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

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

where c(x) for the first equation and the second equation 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 a sidelink.

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 , further comprising:

applying first orthogonal sequence [+1 +1 +1 +1] or second orthogonal sequence [+1 −1 +1 −1] in association with the first, second, third, and fourth DM-RSs for V2X communication.

5. The method of claim 4 , wherein the first orthogonal sequence [+1 +1 +1 +1] is configured to be applied when a modulo-2 operation of an identifier is equal to zero, and

wherein the second orthogonal sequence [+1 −1 +1 −1] is configured to be applied when the modulo-2 operation of the identifier is equal to one.

6. The method of claim 1 , further comprising:

determining to send, to a target device, a V2X data channel; and

determining, for mapping the first, second, third, and fourth DM-RSs, a plurality of symbols in the first slot of the subframe and a plurality of symbols in the second slot of the subframe,

wherein the first, second, third, and fourth DM-RSs are associated with the V2X data channel.

7. The method of claim 1 , further comprising:

determining whether to enable a group-hopping for DM-RSs associated with a V2X data channel.

8. A method for transmitting Demodulation-Reference Signal (DM-RS) for Vehicle-to-everything (V2X) communication, the method comprising:

determining, based on a first group-hopping associated with a first slot number of a subframe, a first DM-RS for V2X communication, and generating, based on a second group-hopping associated with the first slot number and with an offset, a second DM-RS for V2X communication, wherein the first group-hopping and the second group-hopping apply different inputs in a pseudo-random sequence;

mapping the first DM-RS for V2X communication in a first symbol in a first slot of the subframe, and mapping the second DM-RS for V2X communication in a second symbol in the first slot of the subframe;

determining, based on a third group-hopping associated with a second slot number of the subframe, a third DM-RS for V2X communication, and generating, based on a fourth group-hopping associated with the second slot number and with an offset, a fourth DM-RS for V2X communication, wherein the third group-hopping and the fourth group-hopping apply different inputs in the pseudo-random sequence;

mapping the third DM-RS for V2X communication in a first symbol in a second slot of the subframe, and mapping the fourth DM-RS for V2X communication in a second symbol in the second slot of the subframe; and

transmitting the mapped first DM-RS for V2X communication, the mapped second DM-RS for V2X communication, the mapped third DM-RS for V2X communication, and the mapped fourth DM-RS for V2X communication,

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

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

wherein the first symbol in the first slot is symbol #2 and the second symbol in the first slot is symbol #5 if the seven symbols in the first slot are arranged from symbol #0 to symbol #6, and

wherein the first symbol in the second slot is symbol #1 and the second symbol in the second slot is symbol #4 if the seven symbols in the second slot are arranged from symbol #0 to symbol #6.

9. The method of claim 8 , wherein the first group-hopping is associated with a first equation, (Σ i=0 7 c(16n ss PSSCH +i)·2 i )mod 30, and

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

where c(x) for the first equation and the second equation 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 a sidelink.

10. The method of claim 9 , 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.

11. The method of claim 8 , further comprising:

applying first orthogonal sequence [+1 +1 +1 +1] or second orthogonal sequence [+1 −1 +1 −1] in association with the first, second, third, and fourth DM-RSs for V2X communication.

12. The method of claim 11 , wherein the first orthogonal sequence [+1 +1 +1 +1] is configured to be applied when a modulo-2 operation of an identifier is equal to zero, and

wherein the second orthogonal sequence [+1 −1 +1 −1] is configured to be applied when the modulo-2 operation of the identifier is equal to one.

13. A method for transmitting Demodulation-Reference Signal (DM-RS) configured for Vehicle-to-everything (V2X) communication, the method comprising:

determining, based on a first group-hopping associated with a first slot number of a subframe, a first DM-RS for V2X communication, and generating, based on a second group-hopping associated with the first slot number and with an offset, a second DM-RS for V2X communication, the first DM-RS for V2X communication being mapped in a first symbol in a first slot of the subframe, the second DM-RS for V2X communication being mapped in a second symbol in the first slot of the subframe;

determining, based on a third group-hopping associated with a second slot number of the subframe, a third DM-RS for V2X communication, and generating, based on a fourth group-hopping associated with the second slot number and with an offset, a fourth DM-RS for V2X communication, the third DM-RS for V2X communication being mapped in a first symbol in a second slot of the subframe, the fourth DM-RS for V2X communication being mapped in a second symbol in the second slot of the subframe;

applying first orthogonal sequence [+1 +1 +1 +1] or second orthogonal sequence [+1 −1 +1 −1] in association with the first, second, third, and fourth DM-RSs for V2X communication; and

transmitting the first DM-RS for V2X communication, the second DM-RS for V2X communication, the third DM-RS for V2X communication, and the fourth DM-RS for V2X communication.

14. The method of claim 13 , wherein the first orthogonal sequence [+1 +1 +1 +1] is configured to be applied when a modulo-2 operation of an identifier is equal to zero, and

wherein the second orthogonal sequence [+1 −1 +1 −1] is configured to be applied when the modulo-2 operation of the identifier is equal to one.