Methods and systems for locating a mobile device using an asynchronous wireless network

1. A method of locating a User Equipment (UE) at a first base station, the method comprising:

measuring a first time of arrival (TOA) of a first reference signal received from a second base station;

determining a first Real Time Difference (RTD) between a first transmission from the first base station and a second transmission from the second base station, based at least in part on the first TOA, wherein determining the first RTD further comprises determining a first Round Trip signal propagation Time (RTT) between the first base station and the second base station;

measuring a second TOA of an uplink signal received from the UE;

determining a second RTT between the first base station and the UE based at least in part on the second TOA;

receiving a first Reference Signal Time Difference (RSTD) for the first base station and the second base station from the UE; and

sending location information for the UE to a location-capable device, wherein the location information is based at least in part on the first RTD, the second RTT, and the first RSTD.

2. The method of claim 1 , further comprising determining a location of the UE based at least in part on the first RTD, the second RTT, and the first RSTD, wherein the location information comprises the determined location of the UE.

3. The method of claim 1 , wherein the location-capable device determines a location of the UE based at least in part on the location information.

4. The method of claim 1 , wherein the location-capable device comprises a Location Management Function (LMF), a base station different from the first base station, or a location server in a radio access network.

5. The method of claim 1 , wherein the first reference signal comprises a Positioning Reference Signal (PRS), a Tracking Reference Signal (TRS), or a Cell-specific Reference Signal (CRS).

6. The method of claim 1 , wherein the first and second base stations comprise evolved Node Bs (eNBs) for Long Term Evolution (LTE), next generation eNBs (ng-eNBs) for LTE or New Radio (NR) Node Bs (gNBs) for Fifth Generation (5G) NR.

7. The method of claim 1 , wherein the first base station comprises a serving base station for the UE.

8. The method of claim 1 and further comprising:

broadcasting a second reference signal; and

receiving a timing measurement from the UE for the second reference signal, wherein the second RTT is further determined based at least in part on the timing measurement.

9. The method of claim 8 , wherein the second reference signal comprises a Positioning Reference Signal, a Tracking Reference Signal or a Cell-specific Reference Signal.

10. The method of claim 8 , wherein the timing measurement comprises a TOA measurement or a measurement of a transmit time-receive time difference at the UE.

11. The method of claim 1 and further comprising:

measuring a third time of arrival (TOA) of a third reference signal received from a third base station;

determining a second RTD between a third transmission from the first base station and a fourth transmission from the third base station, based at least in part on the third TOA; and

receiving a second RSTD for the first base station and the third base station from the UE, wherein the location information for the UE is further based at least in part on the second RTD and the second RSTD.

12. The method of claim 11 , further comprising determining a location of the UE based at least in part on the first RTD, the second RTT, the first RSTD, the second RTD, and the second RSTD, wherein the location information comprises the determined location of the UE.

13. A method of locating a User Equipment (UE) at the UE, the method comprising:

measuring a time of arrival (TOA) for a first reference signal received from a first base station;

determining a first Round Trip signal propagation Time (RTT) between the first base station and the UE based at least in part on the TOA;

measuring a first Reference Signal Time Difference (RSTD) between a second reference signal for the first base station and a third reference signal for a second base station;

receiving a first real time difference (RTD) between the first base station and the second base station, based on a second RTT between the first base station and the second base station; and

determining a location of the UE, based at least in part on the first RTT, the first RSTD, and the first RTD.

14. The method of claim 13 , wherein the first RTD is received from the first base station or from a Location Management Function (LMF).

15. The method of claim 13 , wherein each of the first reference signal, the second reference signal and the third reference signal comprises a Positioning Reference Signal, a Tracking Reference Signal, or a Cell-specific Reference Signal.

16. The method of claim 13 , wherein the first reference signal and the second reference signal comprise the same reference signal.

17. The method of claim 13 , wherein the first base station and the second base station comprise evolved Node Bs (eNBs) for Long Term Evolution (LTE), next generation eNBs (ng-eNBs) for LTE or New Radio (NR) Node Bs (gNBs) for Fifth Generation (5G) NR.

18. The method of claim 13 , wherein the first base station comprises a serving base station for the UE.

19. The method of claim 13 and further comprising:

sending an uplink signal to the first base station; and

receiving a timing measurement for the uplink signal from the first base station, wherein the first RTT is further determined based at least in part on the timing measurement.

20. The method of claim 19 , wherein the timing measurement comprises a TOA measurement or a measurement of a transmit time-receive time difference obtained at the first base station.

21. The method of claim 13 and further comprising:

measuring a second RSTD between a fourth reference signal for the first base station and a fifth reference signal for a third base station; and

receiving a second RTD between the first base station and the third base station, wherein determining the location of the UE is further based at least in part on the second RSTD and the second RTD.

22. The method of claim 21 , wherein the second reference signal and the fourth reference signal are the same reference signal.

23. A base station comprising:

a wireless communication interface;

a memory; and

a processing unit communicatively coupled with the wireless communication interface and the memory and configured to:

measure, with the wireless communication interface, a first time of arrival (TOA) of a first reference signal received from a second base station;

determine a first Real Time Difference (RTD) between a first transmission from the base station and a second transmission from the second base station, based at least in part on the first TOA, wherein determining the first RTD further comprises determining a first Round Trip signal propagation Time (RTT) between the first base station and the second base station;

measure, with the wireless communication interface, a second TOA of an uplink signal received from a User Equipment (UE);

determine a second RTT between the base station and the UE based at least in part on the second TOA;

receive, with the wireless communication interface, a first Reference Signal Time Difference (RSTD) for the base station and the second base station from the UE; and

send, with the wireless communication interface, location information for the UE to a location-capable device, wherein the location information is based at least in part on the first RTD, the second RTT, and the first RSTD.

24. The base station of claim 23 , wherein the processing unit is further configured to determine a location of the UE based at least in part on the first RTD, the second RTT, and the first RSTD, wherein the location information comprises the determined location of the UE.

25. The base station of claim 23 , wherein the base station comprises an evolved Node B (eNB) for Long Term Evolution (LTE), a next generation eNB (ng-eNB) for LTE or a New Radio (NR) Node B (gNB) for Fifth Generation (5G) NR.

26. The base station of claim 23 , wherein the base station comprises a serving base station for the UE.

27. A User Equipment (UE) comprising:

a wireless communication interface;

a memory; and

a processing unit communicatively coupled with the wireless communication interface and the memory and configured to:

measure, using the wireless communication interface, a time of arrival (TOA) for a first reference signal received from a first base station;

determine a first Round Trip signal propagation Time (RTT) between the first base station and the UE based at least in part on the TOA;

measure, using the wireless communication interface, a first Reference Signal Time Difference (RSTD) between a second reference signal for the first base station and a third reference signal for a second base station;

receive, using the wireless communication interface, a first real time difference (RTD) between the first base station and the second base station, based on a second RTT between the first base station and the second base station; and

determine a location of the UE, based at least in part on the first RTT, the first RSTD, and the first RTD.

28. The UE of claim 27 , wherein the processing unit is further configured to:

send, using the wireless communication interface, an uplink signal to the first base station; and

receive, using the wireless communication interface, a timing measurement for the uplink signal from the first base station;

wherein the processing unit further determines the first RTT based at least in part on the timing measurement.

29. The UE of claim 27 , wherein the processing unit is further configured to:

measure, using the wireless communication interface, a second RSTD between a fourth reference signal for the first base station and a fifth reference signal for a third base station; and

receive, using the wireless communication interface, a second RTD between the first base station and the third base station;

wherein the processing unit determines the location of the UE further based at least in part on the second RSTD and the second RTD.