Method and system for locating mobile stations using call measurement data

• US 8,165,599 B1
• Filed: 12/30/2008
• Issued: 04/24/2012
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: Sprint Spectrum LLC (Deutsche Telekom AG)
• Original Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Inventors: Lall, Abhishek, Dronamraju, Srirama Krishna, Srinivasamurthy, Vishu
• Primary Examiner(s): Corsaro, Nick
• Assistant Examiner(s): Chambers, Tangela T.
• Application Number:
  US12/346,649
• Time in Patent Office: 1,211 Days
• Field of Search: 4554561-4562, 4554565-4566
• US Class Current: 455/456.1
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A location of a mobile station is estimated based on wireless communications between the mobile station and a wireless telecommunications network. Call measurement data is obtained for a call involving the mobile station and a plurality of base station antennas. The call measurement data includes round-trip delay (RTD) measurements and received signal strength (RSS) measurements. The most significant one or more base station antennas involved in the call are identified. An expected signal strength is calculated for each significant base station antenna, according to a wireless propagation model that accounts for terrain around the base station antennas. For each significant base station antenna, the corresponding expected signal strength, RTD measurement, and RSS measurement are used to calculate an adjusted RTD value. The one or more adjusted RTD values calculated for the one or more significant base station antennas are used to estimate the mobile station'"'"'s location.

Claims

1. A method for locating a mobile station based on wireless communications between said mobile station and a wireless telecommunications network, said method comprising:

for each antenna in a plurality of base station antennas in said wireless telecommunications network, obtaining a measurement of round-trip delay (RTD) in wireless communications between said mobile station and said antenna and obtaining a received signal strength (RSS) measurement of a wireless signal transmitted by said antenna and received by said mobile station, so as to obtain a plurality of RTD measurements and a plurality of RSS measurements;

for each given antenna in said plurality of base station antennas, obtaining a respective significance value for said given antenna based, at least in part, on a given RTD measurement and a given RSS measurement corresponding to said given antenna, so as to obtain a plurality of significance values;

identifying at least one significant base station antenna from among said plurality of base station antennas based on said significance values;

obtaining at least one expected signal strength for said at least one significant base station antenna;

determining at least one adjusted RTD value for said at least one significant base station antenna based, at least in part, on said at least one expected signal strength, at least one RTD measurement corresponding to said at least one significant base station antenna, and at least one RSS measurement corresponding to said at least one significant base station antenna; and

using said at least one adjusted RTD value to estimate a location of said mobile station.

2. The method of claim 1, wherein said plurality of RTD measurements and said plurality of RSS measurements are obtained from measurement data for a call involving said mobile station.

3. The method of claim 1, wherein identifying at least one significant base station antenna from among said plurality of base station antennas based on said significance values comprises:

for each given antenna in said plurality of base station antennas, comparing its respective significance value to a predetermined threshold value and identifying said given antenna as significant if its respective significance value exceeds said predetermined threshold value.

4. The method of claim 1, wherein obtaining a respective significance value for said given antenna based, at least in part, on a given RTD measurement and a given RSS measurement corresponding to said given antenna comprises:

obtaining a reference signal strength for said given antenna; and

calculating said respective significance value as a function of said given RTD measurement, said given RSS measurement, and said reference signal strength.

5. The method of claim 4, wherein obtaining a reference signal strength for said given antenna comprises:

selecting a reference location for said given antenna; and

calculating said reference signal strength as a signal strength at said reference location of a pilot signal transmitted by said given antenna, according to a wireless propagation model.

6. The method of claim 5, wherein said wireless propagation model accounts for terrain around said given antenna.

7. The method of claim 1, wherein said at least one significant base station antenna comprises a first significant base station antenna, a second significant base station antenna, and a third significant base station antenna.

8. The method of claim 7, wherein obtaining at least one expected signal strength for said at least one significant base station antenna comprises:

obtaining a first expected signal strength for said first significant base station antenna.

9. The method of claim 8, wherein obtaining a first expected signal strength for said first significant base station antenna comprises:

calculating said first expected signal strength as a signal strength at an expected location of a pilot signal transmitted by said first significant base station antenna, according to a wireless propagation model.

10. The method of claim 9, wherein said wireless propagation model accounts for terrain around said first significant base station antenna.

11. The method of claim 9, further comprising:

selecting said expected location based, at least in part, on an RTD measurement corresponding to said first significant base station antenna.

12. The method of claim 8, wherein determining at least one adjusted RTD value for said at least one significant base station antenna based, at least in part, on said at least one expected signal strength, at least one RTD measurement corresponding to said at least one significant base station antenna, and at least one RSS measurement corresponding to said at least one significant base station antenna comprises:

using a neural network model to calculate a first adjusted RTD value based on first antenna parameters for said first significant base station antenna, said first expected signal strength, a first RTD measurement corresponding to said first significant base station antenna, and a first RSS measurement corresponding to said first significant base station antenna.

13. The method of claim 12, wherein said first antenna parameters include geographic coordinates of said first significant base station antenna.

14. The method of claim 12, wherein said first antenna parameters include a height of said first significant base station antenna.

15. The method of claim 12, wherein said first antenna parameters include an azimuth of said first significant base station antenna.

16. The method of claim 12, wherein said first antenna parameters include a beam width of said first significant base station antenna.

17. The method of claim 12, wherein using said at least one adjusted RTD value to estimate a location of said mobile station comprises:

using said first adjusted RTD value to calculate a first distance between said mobile station and said first significant base station antenna.

18. The method of claim 17, wherein using said at least one adjusted RTD value to estimate a location of said mobile station further comprises:

using a second adjusted RTD value to calculate a second distance between said mobile station and said second significant base station antenna.

19. The method of claim 18, wherein using said at least one adjusted RTD value to estimate a location of said mobile station further comprises:

using a third adjusted RTD value to calculate a third distance between said mobile station and said third significant base station antenna.

20. A system for estimating locations of a plurality of mobile stations based on wireless communications between said mobile stations and a plurality of base station antennas in a wireless telecommunications network, said system comprising:

a first data source, wherein said first data source is configured to provide call measurement data for a plurality of calls involving said mobile stations, said call measurement data including round-trip delay (RTD) measurements and received signal strength (RSS) measurements;

a second data source, wherein said second data source is configured to provide expected signal strengths according to a wireless propagation model, wherein said wireless propagation model accounts for terrain around said base station antennas; and

a location processor communicatively coupled to said first data source and said second data source, wherein said location processor is configured to estimate a given location of a given mobile station by a process comprising (i) calculating significance values for base station antennas involved in one or more calls with said given mobile station based, at least in part, on RTD measurements and RSS measurements provided by said first data source, (ii) identifying significant base station antennas based on said significance values, (iii) calculating adjusted RTD values for said significant base station antennas based, at least in part, on expected signal strengths provided by said second data source, and (iv) estimating said given location of said given mobile station based, at least in part, on said adjusted RTD values.

21. The system of claim 20, wherein said location processor is configured to estimate locations of said mobile stations at periodic time intervals.