System and method for estimating positioning error within a WLAN-based positioning system

• US 8,909,245 B2
• Filed: 08/09/2011
• Issued: 12/09/2014
• Est. Priority Date: 11/07/2006
• Status: Active Grant

• Current Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Original Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Inventors: Alizadeh-Shabdiz, Farshid, Morgan, Edward James
• Primary Examiner(s): Sarwar, Babar
• Application Number:
  US13/206,028
• Publication Number:
  US 20110287783A1
• Time in Patent Office: 1,218 Days
• Field of Search: 4554561-457, 4554351-453, 370/328, 370/329, 370/338, 370/385, 370/420
• US Class Current: 455/456.1
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 64/003 locating network equipment
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

The invention features a method of estimating an expected error of a position estimate for use in a WLAN positioning system that estimates the position of a WLAN-enabled device. The WLAN-enabled device receives signals transmitted by a WLAN access point in range of the WLAN-enabled device. The method estimates the position of the WLAN-enabled device based on the received signals from the WLAN access point in range of the WLAN enabled device. The method also estimates an expected error of the position estimate based on characteristics of the WLAN access point in range of the WLAN enabled device, wherein the expected error predicts a relative accuracy of the position estimate.

Claims

1. In a Wireless Local Area Network (WLAN) positioning system for estimating the position of a WLAN-enabled device, a method of estimating an expected error of a position estimate of the WLAN-enabled device, the method comprising:

receiving an identity of a plurality of WLAN access points in range of the WLAN-enabled device, the plurality of WLAN access points each having an estimated geographic location; and

estimating an expected error, in terms of distance, of a position estimate of the WLAN-enabled device that would result from using the estimated geographic locations of the plurality of WLAN access points in a position estimation determination, based on a spatial spread of WLAN access points in range of the WLAN enabled device,

wherein the spatial spread is a measure of distances between the estimated geographic locations of the plurality of WLAN access points in range of the WLAN enabled device, and the expected error of the position estimate predicts a relative accuracy of the position estimate.

2. The method of claim 1, the estimating the expected error of the position estimate that would result from using the estimated geographic location of the plurality of WLAN access points in a position estimation determination being further based on the estimated geographic locations of the plurality of WLAN access points.

3. The method of claim 1, the receiving the identity including receiving aggregate statistics associated with the estimated geographic locations of the plurality of WLAN access points, and the estimating the expected error that would result from using the estimated geographic locations of the plurality of WLAN access points in a position estimation determination being based on the aggregate statistics.

4. The method of claim 3, the aggregate statistics being at least one of a maximum value, a minimum value, a median value, an average value, a standard deviation, and a sum.

5. The method of claim 1, further comprising estimating the position of the WLAN-enabled device based on the estimated geographic locations of the plurality of WLAN access points in range of the WLAN enabled device only when the expected error of the position estimate is lower than a predetermined threshold.

6. The method of claim 1, the WLAN positioning system using public and private WLAN access points for estimating the position of the WLAN-enabled device.

7. The method of claim 1, the WLAN positioning system using public and private WLAN access points that are deployed over a metropolitan area.

8. The method of claim 1, the estimating the expected error of the position estimate that would result from using the estimated geographic locations of the plurality of WLAN access points in a position estimation determination being based on a weighted average of estimated error based on the measure of distances between the estimated geographic locations of the plurality of WLAN access points combined with an estimated error determined using another error estimation method.

9. In a Wireless Local Area Network (WLAN) positioning system for estimating the position of a WLAN-enabled device, a method of estimating an expected error of a position estimate of the WLAN-enabled device, the method comprising:

receiving an identity of at least one WLAN access point in range of the WLAN-enabled device, the at least one WLAN access point having an estimated signal coverage area; and

estimating an expected error, in terms of distance, of a position estimate that would result from using an estimated geographic position of the at least one WLAN access point in a position estimation determination based on the estimated signal coverage area of the at least one WLAN access point in range of the WLAN enabled device,

wherein the estimated signal coverage area is an area in which WLAN enabled devices can detect the WLAN access point, and the expected error of the position estimate predicts a relative accuracy of the position estimate.

10. The method of claim 9, the estimated signal coverage area for the at least one WLAN access point being estimated based on systematically scanning a target geographical area and recording received signal strength samples at known geographic locations.

11. The method of claim 10, the estimated signal coverage area being based on a subset of the received signal strength samples recorded at known geographic locations.

12. The method of claim 11, further comprising determining members of the subset based on a value of the received signal strength sample.

13. The method of claim 12, the members of the subset including only those received signal strength samples having a value above a predetermined threshold value.

14. The method of claim 11, the estimated signal coverage area being based on statistics associated with the subset of the received signal strength samples recorded at known geographic locations.

15. The method of claim 9, the estimated signal coverage area for the at least one WLAN access point being estimated based on a power profile associated with the at least one WLAN access point, the power profile representing a power value of a signal from the at least one WLAN access point at various geographic locations.

16. The method of claim 9, the estimating the expected error of the position estimate being based on estimated signal coverage area of more than one WLAN access point in range of the WLAN-enabled device.

17. The method of claim 9, the receiving the identity of at least one WLAN access point in range of the WLAN-enabled device including receiving the identities of a plurality of WLAN access points in range of the WLAN-enabled device, the WLAN access points of the plurality having aggregate statistics of the estimated coverage areas of WLAN access points of the plurality, and the estimating the expected error that would result from using the estimated geographic locations of the plurality of WLAN access points in a position estimation determination being based on the aggregate statistics.

18. The method of claim 17, the aggregate statistics being at least one of a maximum value, a minimum value, a median value, an average value, a standard deviation, and a sum.

19. The method of claim 9, further comprising estimating the position of the WLAN-enabled device based on the estimated geographic location of the at least one WLAN access point in range of the WLAN enabled device only when the expected error of the position estimate is lower than a predetermined threshold.

20. The method of claim 9, the WLAN positioning system using public and private WLAN access points for estimating the position of the WLAN-enabled device.

21. The method of claim 9, the WLAN positioning system using public and private WLAN access points that are deployed over a metropolitan area.

22. In a Wireless Local Area Network (WLAN) positioning system for estimating the position of a WLAN-enabled device, a system for estimating an expected error of a position estimate of the WLAN-enabled device, the system for estimating the expected error comprising:

identity receiving logic for receiving the identity of a plurality of WLAN access points in range of the WLAN-enabled device, the plurality of WLAN access points each having an estimated geographic location; and

error estimating logic for estimating an expected error, in terms of distance, of a position estimate of the WLAN-enabled device that would result from use of the estimated geographic locations of the plurality of WLAN access points in a position estimation determination, based on spatial spread of WLAN access points in range of the WLAN enabled device,

wherein the spatial spread is a measure of distances between the estimated geographic locations of the plurality of WLAN access points in range of the WLAN enabled device, and the expected error of the position estimate predicts a relative accuracy of the position estimate.

23. The system of claim 22, the error estimating logic further basing the expected error of the position estimate on the estimated geographic location of the plurality of WLAN access points.

24. The system of claim 22, the identity receiving logic receiving aggregate statistics associated with the estimated geographic locations of the plurality of WLAN access points, and the error estimating logic estimating the expected error further based on the aggregate statistics.

25. The system of claim 24, the aggregate statistics being at least one of a maximum value, a minimum value, a median value, an average value, a standard deviation, and a sum.

26. The system of claim 22, further comprising position estimating logic for estimating the position of the WLAN-enabled device based on the estimated geographic location of the plurality of WLAN access points in range of the WLAN enabled device only when the expected error of the position estimate is lower than a predetermined threshold.

27. The system of claim 22, the WLAN positioning system using public and private WLAN access points for estimating the position of the WLAN-enabled device.

28. The system of claim 22, the WLAN positioning system using public and private WLAN access points that are deployed over a metropolitan area.

29. The system of claim 22, the error estimating logic estimating the expected error further based on a weighted average of estimated error based on the measure of distances between the estimated geographic locations of the plurality of WLAN access points combined with an estimated error determined using another error estimation method.

30. In a Wireless Local Area Network (WLAN) positioning system for estimating the position of a WLAN-enabled device, a system for estimating an expected error of a position estimate of the WLAN-enabled device, the system for estimating the expected error comprising:

signal identity receiving logic for receiving the identity of at least one WLAN access point in range of the WLAN-enabled device, the at least one WLAN access point having an estimated signal coverage area; and

error estimating logic for estimating an expected error, in terms of distance, of a position estimate of the WLAN-enabled device that would result from use of an estimated geographic location of the at least one WLAN access point in a position estimation determination, based on the estimated signal coverage area of the at least one WLAN access point in range of the WLAN enabled device,

wherein the estimated signal coverage area is an area in which WLAN enabled devices can detect the WLAN access point, and the expected error of the position estimate predicts a relative accuracy of the position estimate.

31. The system of claim 30, the estimated signal coverage area for the at least one WLAN access point being estimated based on systematically scanning a target geographical area and recording received signal strength samples at known geographic locations.

32. The system of claim 30, the estimated signal coverage area being based on a subset of the received signal strength samples recorded at known geographic locations.

33. The system of claim 32, further comprising logic for determining members of the subset based on a value of the received signal strength sample.

34. The system of claim 33, the members of the subset including only those received signal strength samples having a value above a predetermined threshold value.

35. The system of claim 32, the estimated signal coverage area being based on statistics associated with the subset of the received signal strength samples recorded at known geographic locations.

36. The system of claim 30, the estimated signal coverage area for the at least one WLAN access point being estimated based on a power profile associated with the at least one WLAN access point, the power profile representing a power value of a signal from the at least one WLAN access point at various geographic locations.

37. The system of claim 30, the error estimating logic further basing the expected error of the position estimate on estimated signal coverage area of more than one WLAN access point in range of the WLAN-enabled device.

38. The system of claim 30, the identity receiving logic receiving the identities of a plurality of WLAN access points in range of the WLAN-enabled device, the system further comprising logic for determining aggregate statistics of the estimated coverage areas of WLAN access points of the plurality, and the error estimating logic estimating the expected error further based on the aggregate statistics.

39. The system of claim 38, the aggregate statistics being at least one of a maximum value, a minimum value, a median value, an average value, a standard deviation, and a sum.

40. The system of claim 30, further comprising position estimating logic for estimating the position of the WLAN-enabled device based on the estimated geographic location of the at least one WLAN access point in range of the WLAN enabled device only when the expected error of the position estimate is lower than a predetermined threshold.

41. The system of claim 30, the WLAN positioning system using public and private WLAN access points for estimating the position of the WLAN-enabled device.

42. The system of claim 30, the WLAN positioning system using public and private WLAN access points that are deployed over a metropolitan area.