Positioning method and device using sidelink RTT in NR V2X

1. A method for performing, by a first user equipment (UE), positioning of the first UE, the method comprising:

transmitting, to a second UE, a first physical control channel including a second identifier (ID) related to the second UE and first control information;

transmitting a first positioning reference signal (PRS) to the second UE;

receiving, from the second UE, a second physical control channel including a first ID related to the first UE;

receiving a second PRS from the second UE;

receiving a first time difference from the second UE; and

determining a position of the first UE based on the first time difference and a second time difference,

wherein the first control information includes reservation information related to transmission of the first PRS,

wherein the first time difference is a time difference between a time when the second UE transmits the second PRS to the first UE and a time when the second UE receives the first PRS, and

wherein the second time difference is a time difference between a time when the first UE receives the second PRS and a time when the first UE transmits the first PRS to the second UE.

2. The method of claim 1 , wherein a value related to the first time difference and the second time difference is a value obtained by subtracting a value related to the first time difference from a value related to the second time difference.

3. The method of claim 1 , further comprising:

transmitting a request for a round trip time (RTT) for the positioning to the second UE; and

receiving an acceptance for the request from the second UE.

4. The method of claim 3 , wherein the request is transmitted to the second UE through at least one of a first positioning protocol message transmitted by the first UE, the first physical control channel transmitted by the first UE, a first PC5 radio resource control (RRC) message transmitted by the first UE, and/or a first medium access control (MAC) control element (CE) transmitted by the first UE, and

wherein the acceptance for the request is transmitted through at least one of a second positioning protocol message transmitted by the second UE, the second physical control channel transmitted by the second UE, a second PC5 RRC message transmitted by the second UE, and/or a second MAC CE transmitted by the second UE.

5. The method of claim 1 , further comprising:

sensing a first resource related to transmission of the first PRS,

wherein the first resource is:

a resource at a transmittable time among resources determined based on the result of the sensing; and

the earliest resource that exists after a specific time has elapsed from the time of receiving the second physical control channel.

6. The method of claim 1 , wherein the first physical control channel includes the first control information,

wherein the first control information includes information related to a resource pool, and

wherein the resource pool includes a resource related to the second PRS.

7. The method of claim 1 , further comprising:

transmitting a third PRS to a third UE;

receiving a fourth PRS from the third UE; and

receiving a third time difference from the third UE,

wherein the position of the first UE is determined based on the first time difference, the second time difference, the third time difference and a fourth time difference,

wherein the third time difference is a time difference between a time when the third UE transmits the fourth PRS to the first UE and a time when the third UE receives the third PRS, and

wherein the fourth time difference is a time difference between a time when the first UE receives the fourth PRS and a time when the first UE transmits the third PRS to the third UE.

8. The method of claim 7 , wherein the first PRS and the third PRS are:

transmitted through the same resource; and

transmitted orthogonally based on the second ID related to the second UE and a third ID related to the third UE.

9. The method of claim 8 , wherein the second ID includes L1 ID or L2 ID of the second UE, and

wherein the third ID includes L1 ID or L2 ID of the third ID.

10. The method of claim 7 , further comprising:

receiving information related to an absolute position of the second UE from the second UE;

receiving information related to an absolute position of the third UE from the third UE; and

obtaining an absolute position of the first UE based on the position of the first UE, information related to the absolute position of the second UE, and information related to the absolute position of the third UE.

11. The method of claim 10 , wherein the second UE is a road side unit (RSU), and

wherein the information related to the absolute position of the second UE is transmitted through an RSU ID related to the RSU.

12. A first user equipment (UE) for performing wireless communication, the first UE comprising:

at least one transceiver;

at least one processor; and

at least one memory connected to the at least one processor and storing instructions that, based on being executed, cause the first UE to perform operations comprising:

transmitting, to a second UE, a first physical control channel including a second identifier (ID) related to the second UE and first control information;

transmitting a first positioning reference signal (PRS) to the second UE;

receiving, from the second UE, a second physical control channel including a first ID related to the first UE;

receiving a second PRS from the second UE;

receiving a first time difference from the second UE; and

determining a position of the first UE based on the first time difference and a second time difference,

wherein the first control information includes reservation information related to transmission of the first PRS,

wherein the first time difference is a time difference between a time when the second UE transmits the second PRS to the first UE and a time when the second UE receives the first PRS, and

wherein the second time difference is a time difference between a time when the first UE receives the second PRS and a time when the first UE transmits the first PRS to the second UE.

13. A processing device adapted to control a first user equipment (UE) to perform wireless communication, the processing device comprising:

at least one processor; and

at least one memory connected to the at least one processor and storing instructions that, based on being executed, cause the at least one processor to perform operations comprising:

transmitting, to a second UE, a first physical control channel including a second identifier (ID) related to the second UE and first control information;

transmitting a first positioning reference signal (PRS) to the second UE;

receiving, from the second UE, a second physical control channel including a first ID related to the first UE;

receiving a second PRS from the second UE;

receiving a first time difference from the second UE; and

determining a position of the first UE based on the first time difference and a second time difference,

wherein the first control information includes reservation information related to transmission of the first PRS,

wherein the first time difference is a time difference between a time when the second UE transmits the second PRS to the first UE and a time when the second UE receives the first PRS, and

wherein the second time difference is a time difference between a time when the first UE receives the second PRS and a time when the first UE transmits the first PRS to the second UE.