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

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.

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.

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.