Location determination and location tracking in wireless networks

• US 20050246334A1
• Filed: 04/30/2004
• Published: 11/03/2005
• Est. Priority Date: 04/30/2004
• Status: Active Grant

• Current Assignee: Meta Platforms, Inc. (f/k/a Facebook, Inc.)
• Original Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Inventors: Tao, Meixia, Lau, Kin-Nang
• Granted Patent: US 7,359,718 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 5/02524 Creating or updating the radio-map
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The present invention is directed to systems and methods which monitor a network environment, collect client information available online, and refine location determinations of individual clients based on observed information as well as online information. More particularly, the present invention is directed to systems and methods which monitor the wireless network, collect online receive signal strength indicator (RSSI) information observations from client users, without requiring knowledge of those clients'"'"' locations. The present invention is additionally directed to systems and methods to enhance the accuracy of the location determinations in a network, based on observed client information such as, for example, signal strength references.

Claims

1. A system comprising:

one or more wireless network access nodes, said one or more wireless network access nodes providing a plurality of antenna patterns;

calculation logic for determining receive signal strength differences with respect to a signal as received by said one or more wireless access nodes using said plurality of antenna patterns, said signal being transmitted from a location unknown to said system;

a radio map providing location estimates associated with use of said plurality of antenna patterns; and

calculation logic for improving said location estimates of said radio map using said receive signal strength differences determined by said calculation logic for determining receive signal strength differences.

2. The system of claim 1, wherein said calculation logic for improving said location estimates iteratively improves said location estimates using a series of receive signal strength differences determined by said calculation logic for determining receive signal strength differences.

3. The system of claim 1, wherein said calculation logic for improving said location estimates includes a location-conditional probability density function for use in improving said location estimates using said receive signal strength differences.

4. The system of claim 3, wherein said location-conditional probability density function includes a probability for each location estimate of said radio map.

5. The system of claim 3, wherein said location-conditional probability density function is determined using a user density profile.

6. The system of claim 3, wherein said location-conditional probability density function is determined using weighting coefficients.

7. The system of claim 1, wherein said calculation logic for improving said location estimates includes weighting coefficients for weighting said receive signal strength differences in a location estimate calculation.

8. The system of claim 7, wherein said weighting coefficients include a weighting coefficient for each receive signal strength observation made with respect to a particular location estimate of said radio map.

9. The system of claim 1, wherein said radio map is formed by sampling a set of multiple grid points.

10. The system of claim 1, further comprising:

a database containing antenna gain profile information for said plurality of antenna patterns of said wireless access nodes.

11. The system of claim 10, wherein said radio map is formed by establishing a set of location candidates and calculating a receive signal strength reference for an imaginary remote station transmitting from each location candidate.

12. The system of claim 11, wherein said receive signal strength references are calculated using a geometrical distance between each of location candidates and each of said wireless network access nodes and an angle between each of said location candidates and each of said wireless network access nodes.

13. The system of claim 10, wherein said database contains antenna gain differences associated with each antenna pattern of said plurality of antenna patterns.

14. The system of claim 1, wherein said radio map is populated with receive signal strength reference information for each of said plurality of antenna patterns.

15. The system of claim 1, wherein said plurality of antenna patterns comprise multiple narrow antenna patterns and a wide antenna pattern associated with a same wireless network access node.

16. The system of claim 1, wherein said calculation logic for determining receive signal strength differences, said calculation logic for iteratively improving said location estimates, and said radio map are disposed at a centralized system in communication with said one or more wireless network access nodes.

17. The system of claim 1, wherein said calculation logic for determining receive signal strength differences, said calculation logic for iteratively improving said location estimates, and said radio map are disposed in a distributed configuration.

18. The system of claim 1, wherein said calculation logic for determining receive signal strength differences, said calculation logic for iteratively improving said location estimates, and said database are disposed within one or more of said wireless network access nodes.

19. A method comprising:

providing a plurality of antenna patterns in a service area;

providing a radio map of location estimates associated with use of said plurality of antenna patterns;

determining receive signal strength information with respect to a signal as received using said plurality of antenna patterns, said signal being transmitted from a location unknown to said system; and

revising said location estimates of said radio map using said determined receive signal strength information.

20. The method of claim 19, wherein said revising said location estimates comprises:

using a series of receive signal strength information determinations to iteratively revise said location estimates.

21. The method of claim 19, further comprising:

determining a location-conditional probability density function, said location-conditional probability density function being used with said determined receive signal strength in said revising said location estimates.

22. The method of claim 21, wherein said determining said location-conditional density function comprises:

determining a probability of a receive signal strength information profile for each location estimate of said radio map.

23. The method of claim 21, wherein said determining said location-conditional density function comprises:

using a user density profile.

24. The method of claim 21, wherein said determining said location-conditional density function comprises:

using weighting coefficients.

25. The method of claim 19, wherein said revising said location estimates comprises:

applying weighting coefficients to said receive signal strength information.

26. The method of claim 25, wherein said weighting coefficients include a weighting coefficient for each receive signal strength observation made with respect to a particular location estimate of said radio map.

27. The method of claim 19, wherein said providing said radio map comprises:

forming said radio map by sampling a set of multiple grid points.

28. The method of claim 19, wherein said providing said radio map comprises:

forming said radio map by establishing a set of location candidates and calculating a receive signal strength reference for an imaginary remote station transmitting from each location candidate.

29. The method of claim 28, wherein said forming said radio map comprises:

using antenna gain profile information for said plurality of antenna patterns for each location candidate.

30. The method of claim 28, wherein said receive signal strength references are calculated using a geometrical distance between each of location candidates and a wireless network access node and an angle between each of said location candidates and said wireless network access node.

31. The method of claim 28, wherein said providing said radio map comprises:

populating said radio map with receive signal strength reference information for each of said plurality of antenna patterns.

32. The method of claim 19, further comprising:

providing a database of antenna gain differences associated with each antenna pattern of said plurality of antenna patterns for use in said revising said location estimates.

33. The method of claim 19, wherein said plurality of antenna patterns comprise multiple narrow antenna patterns and a wide antenna pattern associated with a same wireless network access node.

34. The method of claim 19, further comprising:

determining a location of a remote station using said revised location estimates of said radio map.

35. The method of claim 34, wherein said determining said location comprises:

using said determined receive signal strength information.

36. The method of claim 34, wherein said determining said location comprises:

using historical information to model a likelihood of the remote station transitioning in successive instants in time.

37. A system comprising:

a map of points in a wireless network environment;

a set of online observations from one or more network client users;

computation logic for computing a weighting coefficient associated with observations of said set of online observations;

calculation logic for calculating an update point for a point of said map, wherein said calculation logic uses observations of said set of online observations and their associated weighting coefficients in calculating said update point; and

refining logic for updating said point of said map with said update point.

38. The system of claim 37, further comprising:

determination logic for determining probability of a received signal strength, said determined probability being utilized by said calculation logic in calculating said update point.

39. The system of claim 37, further comprising:

comparison logic for determining the difference between a plurality of points of said map and said update point for selecting said point of said map for updating with said update point.

40. The system of claim 37, wherein said map includes received signal strength information with respect to said points of said map.

41. The system of claim 40, wherein said received signal strength information is observed.

42. The system of claim 40, wherein said received signal strength information is predicted.

43. The system of claim 42, wherein said map of received signal strength information is predicted using a generic propagation model.

44. The system of claim 37, wherein refining logic updates said map without requiring manual measurements in said wireless network environment.

45. The system of claim 37, wherein said set of online observations contains a greater number of observations than the number of said observed points in said map.

46. The system of claim 37, wherein said computation logic, said calculation logic, and said refining logic are disposed at a centralized system in communication with a plurality of wireless network access nodes.

47. The system of claim 37, wherein said computation logic, said calculation logic, and said refining logic are disposed in a distributed configuration.

48. A method for refinement of a map of a wireless network environment using unsupervised learning, said method comprising:

providing an initial received signal strength reference for a location on a map of a wireless network environment;

providing one or more online observations from client users of said wireless network environment;

assigning a probability density function to a receive signal strength reference for said location on said map;

calculating a weighting coefficient for said location on said map;

calculating an update received signal strength reference for said location on said map; and

replacing said initial receive signal strength reference for said location on a map with said update received signal strength reference.

49. The method of claim 48, wherein a probability of said probability density function is location-conditional.

50. The method of claim 48, wherein said calculating an update received signal strength reference for said location on said map comprises:

calculating said update received signal strength reference with said one or more online observations and said weighting coefficient.

51. The method of claim 48, further comprising:

iteratively calculating a weighting coefficient for each of the one or more locations on said grid map of a wireless network environment;

iteratively calculating an update received signal strength reference for each of the one or more locations on said grid map of a wireless network environment with said probability and said weighting coefficient; and

iteratively replacing said initial receive signal strength reference for each of the one or more locations on a grid map of a wireless network environment with each of the said update received signal strength reference.

52. A method for online location determination of a stationary target, said method comprising:

selecting a target client;

selecting one or more wireless network access nodes;

providing a radio map associated with said one or more wireless network access nodes and providing location candidates for a service area of said one or more wireless network access nodes;

computing a distance in signal space between said target client and said location candidates to identify one or more location candidates;

calculating a mean position of said one or more location candidates; and

estimating a location of said target client using said mean position.

53. The method of claim 52, wherein estimating said location of said target client comprises:

using a plurality of antenna beams associated with one or more of nearest wireless access nodes neighboring said target client.

54. The method of claim 53, wherein estimating said location of said target client comprises:

estimating location of said target client using a weighted mean position.

55. The method of claim 52, further comprising:

providing network access as a function of said location.

56. The method of claim 52, further comprising:

providing data content as a function of said location.

57. The method of claim 52, further comprising:

providing management of network resources as a function of said location.

58. A method for determining a location of a remote station in a wireless network, said method comprising:

providing a radio map providing location estimates for a plurality of points in a service area of said wireless network;

observing received signal strength information associated with a plurality of antenna patterns for a plurality of remote stations; and

applying said observed receive signal strength information to said radio map to iteratively revise location estimates of said radio map.

59. The method of claim 58, wherein said providing said radio map comprises:

calculating a radio map using a propigation model with respect to a grid of points in said service area.

60. The method of claim 58, wherein said applying said observed receive signal strength information to said radio map comprises:

applying weighting coefficients to said observed receive signal strength information.

61. The method of claim 60, wherein said weighting coefficients include a weighting coefficient for each receive signal strength observation made with respect to a particular location estimate of said radio map.

62. The method of claim 58, wherein said applying said observed receive signal strength information to said radio map comprises:

using a location-conditional probability density function.

63. The method of claim 62, further comprising:

determining said location-conditional density function using weighting coefficients.

64. The method of claim 63, wherein said determining said location-conditional density function comprises:

determining a probability of a receive signal strength information profile for each location estimate of said radio map.

65. The method of claim 63, wherein said determining said location-conditional density function comprises:

using a user density profile.