Sidelink timing-based positioning

1 . A user equipment (“UE”) for wireless communication, comprising:

at least one memory; and

at least one processor coupled with the at least one memory and configured to cause the UE to:

receive a set of sidelink (“SL”) positioning reference signals (“SL-PRS”) measurements from a reference node and two or more additional UEs;

measure a set of SL reference signal timing differences (“RSTDs”) between the two or more additional UEs with respect to the reference node;

receive, from the reference node or the two or more additional UEs, transmit time information to compensate for real time difference (“RTD”) offsets in performing a time-difference-of-arrival (“TDOA”) positioning technique; and

determine an estimated location of the UE based on the TDOA positioning technique using the set of SL RSTDs.

2 . The UE of claim 1 , wherein to determine the estimated location, the at least one processor is configured to cause the UE to:

locally compute the estimated location based on the TDOA positioning technique using the set of SL RSTDs.

3 . The UE of claim 1 , wherein to determine the estimated location, the at least one processor is configured to cause the UE to:

report the set of SL RSTDs measurements to a location server using an interface selected from a Uu interface, a SL interface, or both; and

determine the estimated location based at least in part on a response received from the location server.

4 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to receive location information for the two or more additional UEs, and wherein the location information comprises:

first absolute location information received from one or more anchor UEs of the two or more additional UEs, wherein the first absolute location information comprises respective absolute locations of the one or more anchor UEs; or

second absolute location information received from a location management function (“LMF”) for one or more non-anchor UEs of the two or more additional UEs, wherein the second absolute location information comprises respective absolute locations of the one or more anchor UEs.

5 . The UE of claim 1 ,

wherein the reference node is a fixed node selected from a base station, a roadside unit (“RSU”), a SL-UE, or a vulnerable road user (“VRU”); and

wherein the processor is configured to cause the UE to measure the RSTD based on at least one SL-PRS received from the reference node.

6 . The UE of claim 1 ,

wherein the reference node is a non-anchor mobile node selected from a SL-UE or a vulnerable road user (“VRU”);

wherein the two or more additional UEs are non-anchor nodes; and

wherein the processor is configured to cause the UE to receive, from the non-anchor mobile node, one or more SL-PRS configurations corresponding to a set of SL transmission reception points (“TRPs”) originating from the non-anchor mobile node and the two or more additional UEs.

7 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to initiate a groupcast communication session between a vehicle-to-everything (“V2X”) layer and a location management function (“LMF”) to perform the TDOA positioning technique.

8 . The UE of claim 7 ,

wherein the reference node is a mobile reference node selected from a SL-UE and a vulnerable road user (“VRU”);

wherein the two or more additional UEs are non-anchor nodes; and

wherein the processor is configured to cause the UE to receive from the LMF:

identities and SL-PRS configurations corresponding to a set of SL transmission reception points (“TRPs”) originating from the mobile reference node and the two or more additional UEs; and

relative locations of the two or more additional UEs with respect to the mobile reference node based on the groupcast communication session initiated between the V2X layer and the LMF.

9 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to receive the set of SL-PRS using one or more SL channels selected from Physical Sidelink Control Channels (“PSCCHs”), Physical Sidelink Broadcast Channels (“PSBCHs”), and Physical Sidelink Shared Channels (“PSSCH”), or a combination thereof.

10 . The UE of claim 1 , wherein the set of SL-PRS are configured and measured at a plurality of time instances corresponding to points along a trajectory of the UE.

11 . A method performed by a User Equipment (“UE”), the method comprising:

receiving a set of sidelink (“SL”) positioning reference signals (“SL-PRS”) measurements from a reference node and two or more additional UEs;

measuring a set of SL reference signal timing differences (“RSTDs”) between the two or more additional UEs with respect to the reference node;

receiving, from the reference node or the two or more additional UEs, transmit time information to compensate for real time difference (“RTD”) offsets in performing a time-difference-of-arrival (“TDOA”) positioning technique; and

determining an estimated location of the UE based on the TDOA positioning technique using the set of SL RSTDs.

12 . The method of claim 11 , wherein determining the estimated location comprises:

locally computing the estimated location based on the TDOA positioning technique using the set of SL RSTDs.

13 . The method of claim 11 , wherein determining the estimated location comprises:

reporting the set of SL RSTDs measurements to a location server using an interface selected from a Uu interface, a SL interface, or both; and

determining the estimated location based at least in part on a response received from the location server.

14 . The method of claim 11 , further comprising receiving location information for the two or more additional UEs, wherein the location information comprises:

first absolute location information received from one or more anchor UEs of the two or more additional UEs, wherein the first absolute location information comprises respective absolute locations of the one or more anchor UEs; or

second absolute location information received from a location management function (“LMF”) for one or more non-anchor UEs of the two or more additional UEs, wherein the second absolute location information comprises respective absolute locations of the one or more anchor UEs.

15 . The method of claim 11 ,

wherein the reference node is a fixed node selected from a base station, a roadside unit (“RSU”), a SL-UE, or a vulnerable road user (“VRU”), and

wherein the method further comprises measuring the RSTD based on at least one SL-PRS received from the reference node.

16 . The method of claim 11 ,

wherein the reference node is a non-anchor mobile node selected from a SL-UE or a vulnerable road user (“VRU”);

wherein the two or more additional UEs are non-anchor nodes; and

wherein the method further comprises receiving, from the non-anchor mobile node, one or more SL-PRS configurations corresponding to a set of SL transmission reception points (“TRPs”) originating from the non-anchor mobile node and the two or more additional UEs.

17 . The method of claim 11 , further comprising initiating a groupcast communication session between a vehicle-to-everything (“V2X”) layer and a location management function (“LMF”) to perform the TDOA positioning technique.

18 . The method of claim 17 ,

wherein the reference node is a mobile reference node selected from a SL-UE and a vulnerable road user (“VRU”);

wherein the two or more additional UEs are non-anchor nodes; and

wherein the method further comprises receiving from the LMF:

identities and SL-PRS configurations corresponding to a set of SL transmission reception points (“TRPs”) originating from the mobile reference node and the two or more additional UEs; and

relative locations of the two or more additional UEs with respect to the mobile reference node based on the groupcast communication session initiated between the V2X layer and the LMF.

19 . The method of claim 11 , further comprising receiving the set of SL-PRS using one or more SL channels selected from Physical Sidelink Control Channels (“PSCCHs”), Physical Sidelink Broadcast Channels (“PSBCHs”), and Physical Sidelink Shared Channels (“PSSCH”), or a combination thereof.

20 . The method of claim 11 , wherein the set of SL-PRS are configured and measured at a plurality of time instances corresponding to points along a trajectory of the UE.