CELL ID BASED POSITIONING FROM CELL INTERSECTIONS

• US 20080039114A1
• Filed: 08/11/2006
• Published: 02/14/2008
• Est. Priority Date: 08/11/2006
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Venkatasubramanian, Vijayaraghavan, Phatak, Makarand, Kohli, Sanjai, Garin, Lionel, Wan, Marlene
• Granted Patent: US 8,364,164 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Systems and methods are described for determining location of wireless devices using signal strength of signals detected by the wireless devices. The strength of signals received from identifiable sources is typically compared to reference signal strength measurements collected or estimated at known locations. Information identifying the source of the signals is typically obtained from data provided in the signals. Mappers associate combinations of reference signal strengths with geometrically shaped geographical regions such that signal strength measurements can be used as indices to locate a region in which a wireless device can be found. Systems and methods are described for receiving signal strength information from known locations where the information can be used to update and improve mapping system databases.

Claims

1. A method for locating a wireless device, comprising the steps of:

obtaining measured signal strengths of one or more identifiable signals from the wireless device;

determining location of the wireless device by comparing the measured signal strengths to reference signal strengths of the one or more identifiable signals.

2. The method of claim 1, wherein each of the one or more identifiable signals is associated with a radio frequency (RF) source.

3. The method of claim 1, wherein each of the one or more identifiable signals provides information identifying an RF source of the each identifiable signal.

4. The method of claim 1, and further comprising the step of identifying an RF source of at least one of the one or more identifiable signals.

5. The method of claim 4, wherein the RF source is identified from information provided in the at least one identifiable signal.

6. The method of claim 4, wherein the step of identifying an RF source includes associating a service provider with the at least one identifiable signal.

7. The method of claim 1, wherein the reference signal strengths include previously obtained measurements of signal strengths of the one or more identifiable signals,

8. The method of claim 7, wherein the previously obtained measurements of signal strengths include signal strengths measured at a plurality of known locations.

9. The method of claim 1, wherein the reference signal strengths include estimated signal strengths of the one or more identifiable signals.

10. The method of claim 9, wherein the estimated signal strengths are obtained by modeling.

11. The method of claim 1, wherein the reference signal strengths include expected signal strengths for the one or more identifiable signals in a known geographical region.

12. The method of claim 10, wherein the expected signal strength values are expressed as ranges of possible signal strengths for the known geographical region.

13. The method of claim 11, wherein location is determined by comparing the measured signal strengths with expected signal strengths in selected geographical regions.

14. The method of claim 1, wherein the measured signal strengths are adjusted using correction factors based on a history of measurements recorded for the wireless device

15. A method for mapping signal strength comprising:

identifying portions of a geographic area wherein each portion is associated with a signal and strengths of the signal measured within the each portion are expected to fall within a predetermined range;

delineating intersections corresponding to selected overlapping portions; and

fitting the intersections to regions having a desired geometrical shape.

16. The method of claim 15, wherein the desired geometrical shape is elliptical.

17. The method of claim 15, wherein the intersections are representative of coverage area hulls associated with RF sources.

18. The method of claim 17, wherein the RF sources include a cellular telephone system base station.

19. The method of claim 17, wherein the RF sources include a WiFi base station.

20. The method of claim 15, wherein a source of the signal associated with the each portion is identifiable.

21. The method of claim 15, and further comprising the step of indexing each region using signal strength ranges expected within the each region.

22. A system comprising:

a database configured to maintain expected signal strengths of signals within a geographic area;

a mapper for identifying regions of the geographic area wherein each region is characterized by a range of expected signal strengths for each of one or more of the signals detectable in the each region; and

one or more servers for locating a wireless device in one of the identified regions based on signal strengths measured by the wireless device.

23. The system of claim 22, wherein certain of the expected signal strengths are based on signal strengths measured at known locations within the geographic area.

24. The system of claim 22, wherein certain of the expected signal strengths include estimated signal strengths for selected locations within the geographic area.

25. The system of claim 22, wherein sources of the signals are identifiable.

26. The method of claim 25, wherein the sources include a cellular telephone system base station.

27. The method of claim 25, wherein the sources include a WiFi base station.

28. The system of claim 23, wherein the measured signal strengths include signal strengths measured by a GPS-equipped wireless device.

29. The method of claim 24, wherein the estimated signal strengths are obtained by modeling.

30. The system of claim 22, wherein the wireless device is located based on an intersection of signal strengths of signals received from two or more RF sources.