Systems and methods for using a satellite positioning system to detect moved WLAN access points

• US 8,154,454 B2
• Filed: 08/17/2011
• Issued: 04/10/2012
• Est. Priority Date: 07/16/2009
• Status: Active Grant

• Current Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Original Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Inventors: Alizadeh-Shabdiz, Farshid
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US13/211,703
• Publication Number:
  US 20120007775A1
• Time in Patent Office: 237 Days
• Field of Search: 342/458
• US Class Current: 342/458
• CPC Class Codes: G01S 19/00 Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/0242 Determining the position of transmitters to be subsequently used in positioning G01S5/0289 takes precedence
• CPC Class Codes: G01S 5/0263 by combining or switching between positions derived from two or more separate positioning systems
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 4/029 Location-based management or tracking services

Abstract

The disclosed subject matter generally relates to hybrid positioning systems and methods and, more specifically, systems and methods of detecting moved WLAN assess points using a wireless local area network based positioning system (WLAN-PS) and a satellite-based positioning system (SPS) with at least two satellites measurement.

Claims

1. A method of using a Wireless Local Area Network (WLAN) and satellite enabled device to infer that a reference location associated with a detected WLAN access point (AP) is not the present location of the AP, the method comprising:

identifying WLAN APs detected by the WLAN and satellite enabled device;

accessing a reference database to obtain a reference location associated with at least one of the WLAN APs;

grouping the WLAN APs into clusters of at least one WLAN AP based on the reference locations associated with the identified WLAN APs;

determining an aggregate reference location for at least one cluster of WLAN APs based on the reference locations associated with the WLAN APs grouped into said cluster;

receiving at least one possible Satellite Positioning System (SPS) location solution of the device based on satellite measurements from at least two satellites;

estimating a distance between the aggregate reference location associated with the at least one cluster and the at least one possible SPS location solution; and

inferring that the reference location associated with the at least one WLAN AP of the at least one cluster is not the present location of the WLAN AP if the distance between the aggregate reference location of said cluster and the at least one SPS location solution is above a predetermined threshold.

2. The method of claim 1, wherein the satellite measurements are from less than four satellites.

3. The method of claim 1, further comprising providing a plurality of possible SPS location solutions of the device from the satellite measurements.

4. The method of claim 3, wherein the plurality of possible SPS location solutions of the device comprise a region of possible location solutions for the device.

5. The method of claim 1, further comprising indicating in the reference database that the reference locations associated with the WLAN APs of the at least one cluster are not the present locations of said WLAN APs.

6. The method of claim 1, further comprising updating in the reference database the reference locations associated with the WLAN AP of the at least one cluster to reflect estimated present locations of the associated WLAN APs.

7. The method of claim 1, wherein the predetermined threshold is based on an estimated coverage area of the at least one WLAN AP of the at least one cluster.

8. The method of claim 1, further comprising estimating a consistency between the satellite measurements and the aggregate reference location of the at least one cluster.

9. The method of claim 8, wherein the consistency between the aggregate reference location of the at least one cluster and the satellite measurements is estimated by applying said aggregate reference location to the satellite measurements and determining an internal SPS receiver clock bias to conform the satellite measurements to said aggregate reference location.

10. The method of claim 8, further comprising calculating an internal SPS receiver clock bias by considering the aggregate reference location of the at least one cluster as an initial position.

11. The method of claim 1, wherein the estimating the distance between the aggregate reference location of the at least one cluster and the at least one possible SPS location solution is estimated based on:

determining an internal SPS receiver clock bias that would yield an SPS position within a predetermined distance of the aggregate reference location; and

comparing the determined internal SPS receiver clock bias to a clock bias associated with the at least one possible SPS location solution.

12. The method of claim 11, wherein determining the internal SPS receiver clock bias that would yield an SPS position within a predetermined distance of the aggregate reference location includes determining the standard deviation or the mean square error of the internal SPS receiver clock bias.

13. A system for using a Wireless Local Area Network (WLAN) and satellite enabled device to infer that a reference location associated with a detected WLAN access point (AP) is not the present location of the AP, the system comprising:

logic for identifying WLAN APs detected by the WLAN and satellite enabled device;

logic for accessing a reference database to obtain a reference location associated with at least one of the WLAN APs;

logic for grouping the WLAN APs into clusters of at least one WLAN AP based on the reference locations associated with the identified WLAN APs;

logic for determining an aggregate reference location for at least one cluster of WLAN APs based on the reference locations associated with the WLAN APs grouped into said cluster;

logic for receiving at least one possible Satellite Positioning System (SPS) location solution of the device based on satellite measurements from at least two satellites;

logic for estimating a distance between the aggregate reference location associated with the at least one cluster and the at least one possible SPS location solution; and

logic for inferring that the reference location associated with the at least one WLAN AP of the at least one cluster is not the present location of the WLAN AP if the distance between the aggregate reference location of said cluster and the at least one SPS location solution is above a predetermined threshold.

14. The system of claim 13, wherein the satellite measurements are from less than four satellites.

15. The system of claim 13, the logic for receiving at least one possible Satellite Positioning System (SPS) location solution of the device including logic for providing a plurality of possible SPS location solutions of the device from the satellite measurements.

16. The system of claim 15, wherein the plurality of possible SPS location solutions of the device comprise a region of possible location solutions for the device.

17. The system of claim 13, further comprising logic for indicating in the reference database that the reference locations associated with the WLAN APs of the at least one cluster are not the present locations of said WLAN APs.

18. The system of claim 13, further comprising logic for updating in the reference database the reference locations associated with the WLAN AP of the at least one cluster to reflect estimated present locations of the associated WLAN APs.

19. The system of claim 13, wherein the predetermined threshold is based on an estimated coverage area of the at least one WLAN AP of the at least one cluster.

20. The system of claim 13, further comprising logic for estimating a consistency between the satellite measurements and the aggregate reference location of the at least one cluster.

21. The system of claim 20, wherein the consistency between the aggregate reference location of the at least one cluster and the satellite measurements is estimated by applying said aggregate reference location to the satellite measurements and determining an internal SPS receiver clock bias to conform the satellite measurements to said aggregate reference location.

22. The system of claim 20, further comprising calculating an internal SPS receiver clock bias by considering the aggregate reference location of the at least one cluster as an initial position.

23. The system of claim 13, wherein the estimating the distance between the aggregate reference location of the at least one cluster and the at least one possible SPS location solution is estimated based on:

determining an internal SPS receiver clock bias that would yield an SPS position within a predetermined distance of the aggregate reference location; and

comparing the determined internal SPS receiver clock bias to a clock bias associated with the at least one possible SPS location solution.

24. The system of claim 23, wherein determining the internal SPS receiver clock bias that would yield an SPS position within a predetermined distance of the aggregate reference location includes determining the standard deviation or the mean square error of the internal SPS receiver clock bias.