Proximity detection using wireless signal strengths

• US 20060046709A1
• Filed: 06/29/2004
• Published: 03/02/2006
• Est. Priority Date: 06/29/2004
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Krumm, John C., Hinckley, Kenneth P.
• Granted Patent: US 7,509,131 B2
• Time in Patent Office: Days
• US Class Current: 455/422.100
• CPC Class Codes: H04N 21/4126 The peripheral being portable, e.g. PDAs or mobile phones
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Described is a system and method in a wireless (Wi-Fi) network comprising a server, clients and various mechanisms that compute lists of other clients and resources that are physically nearby. Clients report Wi-Fi access points'"'"' signal strengths to a server, which uses that data to compute the proximity of resources to one another, including an estimate the distance between resources. The data may be returned to the client as a list of resources within short range proximity, or resources within long-range proximity, with an approximate time to that resource based on previous clients'"'"' reporting. Because proximity is used rather than absolute location, only minimal setup is needed. As the number of clients and resources that use the system increases, the server knowledge also increases with respect to the number of resources that can be found and in the physical range over which other people and places can be found.

Claims

1. In a environment in which signal strengths data can be detected, a method comprising:

obtaining signal strength data of a first device with respect to signals received from at least one base station; and

computing an approximate distance from the first network device to a resource based on the signal strength data.

2. The method of claim 1 further comprising, building a database of signal strength data.

3. The method of claim 2 further comprising, determining from the database which base stations can be detected simultaneously with one another.

4. The method of claim 3 further comprising, maintaining a data structure that contains information as to which base stations are adjacent to which other base stations.

5. The method of claim 4 further comprising, providing data to a client corresponding to how many base stations away the client is to a resource.

6. The method of claim 2 wherein building the database includes discarding inconsistent information as to at least one base station that has not been previously detected.

7. The method of claim 2 wherein building the database includes discarding inconsistent information as to base stations that are reported as having overlapping coverage but have not been previously detected as having overlapping coverage.

8. The method of claim 1 wherein computing the approximate distance from the first network device to the resource comprises comparing how many base stations are detected in common by each.

9. The method of claim 8 wherein computing the approximate distance from the first network device to the resource comprises ordering base stations seen in common by signal strength values into a first ordering for the network device and a second ordering for the resource, and determining similarity between the first ordering and the second ordering.

10. The method of claim 1 further comprising, selecting numeric features for computing distance, and testing combinations of those features to determine a function that gives the best results with respect to actual distances.

11. The method of claim 1 wherein the resource is not connected to the network, and further comprising, using another network device to assign signal strength data to the resource.

12. The method of claim 1 wherein the resource comprises a mobile computing device, and further comprising, obtaining a plurality of readings from the resource and returning information corresponding to the approximate distance to the resource based on a latest reading of the plurality.

13. The method of claim 1 further comprising, providing short range proximity data to a client corresponding to at least one resource that is within a short distance of the client.

14. The method of claim 13 further comprising using the proximity data to establish that a mobile device is closely associated with another mobile device.

15. The method of claim 13 wherein the short range proximity data is used to present a list of nearby people and things to a user of the client.

16. The method of claim 13 further comprising, sending a communication from the client to another device based on the short range proximity data indicating that the other device is nearby.

17. At least one computer-readable medium having computer-executable instructions which when executed perform the method of claim 1.

18. In a network environment, a method comprising:

obtaining signal strength data from a plurality of scan sources that indicates a signal strength and access point identity for each detected signal; and

processing the data to develop long-range proximity information.

19. The method of claim 18 further comprising, processing the data to develop short-range proximity information between a scan source and another entity.

20. The method of claim 18 wherein processing the data to develop long-range proximity information comprises determining access point topology by determining which access points are detected at the same time by a scan source.

21. The method of claim 20 further comprising, using the topology to provide data corresponding to a number of access points between a querying client and another entity.

22. The method of claim 18 further comprising, applying a time-stamp to at least some of the signal strength data.

23. The method of claim 22 further comprising, using the time-stamp to compute an estimated traversal time between a user corresponding to a scan source and another entity corresponding to another scan source.

24. The method of claim 23 further comprising, sending the estimated time to the user.

25. At least one computer-readable medium having computer-executable instructions which when executed perform the method of claim 18.

26. In a network environment, a method comprising:

obtaining a first signature comprising signal strength data with respect to signals received by a first network device from at least one base station;

obtaining a second signature comprising signal strength data with respect to signals received by a second network device from at least one base station; and

computing an approximate distance from the first network device to the second network device based on the first and second signatures.

27. The method of claim 26 wherein the second network device represents a resource that is not a network device, and further comprising, receiving information about that resource in association with the signal strength data.

28. The method of claim 26 wherein computing an approximate distance comprises applying a numerical function to the two Wi-Fi signatures.

29. The method of claim 28 wherein the numerical function includes a variable corresponding to a number of base stations detected in common between the first and the second network devices.

30. The method of claim 28 wherein the numerical function includes a variable corresponding to how closely the first and the second network devices ranked based stations seen in common by signal strength.

31. The method of claim 28 wherein the numerical function includes a variable corresponding to differences of signal strengths.

32. The method of claim 28 wherein the numerical function includes a variable corresponding to base stations not in common.

33. The method of claim 28 wherein the numerical function includes one variable corresponding to a number of base stations detected in common between the first and the second network devices, and another variable corresponding to how closely the first and the second network devices ranked based stations seen in common by signal strength.

34. The method of claim 28 wherein the function comprises a polynomial, and further comprising, measuring actual distances to determine coefficients of the polynomial.

35. The method of claim 26 further comprising, reporting the distance to a client.

36. The method of claim 26 further comprising, using the distance in conjunction with other computed distances relative to a client to provide a sorted list the client.

37. The method of claim 26 further comprising using the approximate distance to establish that a mobile device is closely associated with another mobile device.

38. The method of claim 26 further comprising, sending a communication from the first network device to the second network device based on the approximate distance indicating that the other device is nearby.

39. At least one computer-readable medium having computer-executable instructions which when executed perform the method of claim 26.