Method for RF fingerprinting

• US 20050040968A1
• Filed: 07/29/2004
• Published: 02/24/2005
• Est. Priority Date: 07/31/2003
• Status: Active Grant

• Current Assignee: InnerWireless Incorporated (Black Box Ltd.)
• Original Assignee: InnerWireless Incorporated (Black Box Ltd.)
• Inventors: Trammel, Brian H., Damarla, Chanakya, Pollard, Mark, Ivers, James, Kompanek, Andrew J.
• Granted Patent: US 7,346,359 B2
• Time in Patent Office: Days
• US Class Current: 340/825.490
• CPC Class Codes: G01S 5/02526 using non-dedicated equipment, e.g. user equipment or crowd-sourcing
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The invention provides a novel method for preparing a wireless environment for location determination of a wireless mobile unit, and for location determination of a wireless mobile unit. In preparing the physical environment, the invention utilizes novel techniques, including novel techniques to place transmitters, the removal of outlying data in the creation of reference RF fingerprints, and algorithms to obtain accurate reference RF fingerprints. In determining the location of a wireless mobile unit, the invention utilizes novel techniques, including novel techniques to select transmitters, the removal of outlying data in the creation of reference RF fingerprints, and algorithms to obtain accurate reference RF fingerprints.

Claims

1. A method of preparing an area for location determination of a mobile unit comprising the steps of:

a) providing at least two transmitters that are consistently detectable by said mobile unit at locations in said area;

b) collecting RF data of said mobile unit at said locations in said area; and

c) assigning a unique reference RF fingerprint for each of said locations based on said collected RF data for each of said locations.

2. The method of claim 1 wherein said RF data of said mobile unit at locations in said area further comprises RF data related to an orientation of said mobile unit at said locations in said area, said method further comprising assigning a unique reference RF fingerprint for each orientation of said mobile unit at each of said locations based on said collected RF data for each said orientation at said each location.

3. The method of claim 1 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises:

averaging said collected data respective to each location to obtain an average and assigning said reference RF fingerprint respective to each location based each said respective average.

4. The method of claim 2 wherein said step of assigning said reference RF fingerprint for each of said locations and orientations based on said collected RF data further comprises:

averaging said collected data respective to each location and orientation to obtain an average and assigning said reference RF fingerprint respective to each location and orientation based each said respective average.

5. The method of claim 1 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises interpreting said RF data for missed transmissions and wherein said unique reference RF fingerprints are assigned based on said interpreted data.

6. The method of claim 1 wherein said step of assigning said reference RF fingerprint for each of said location based on said collected RF data further comprises:

a) determining if any of said collected RF data respective to each location is outlying;

b) applying a mathematical function to said RF data that is not outlying respective to each location and obtaining a value from said application of said mathematical function; and

c) assigning a unique reference RF fingerprint for each of said locations based on said respective value.

7. The method of claim 6 wherein outlying RF data is data outside N standard deviations of an average of said RF data for that location.

8. The method of claim 6 wherein outlying RF data is data over N units from an average of said RF data for that location.

9. The method of claim 1 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises:

a) determining if a transmitter is out of range or temporarily unobservable for said mobile unit at a location;

b) applying a mathematical function to said collected data for respective locations that are not temporarily unobservable or out of range and obtaining a value from said application of said mathematical function; and

c) assigning a unique reference RF fingerprint for each of said respective locations based on said respective values.

10. The method of claim 9 wherein said step of determining if a transmitter is out of range or temporarily unobservable for a mobile unit at a location is accomplished by determining that a transmitter is out of range if a transmitter has not been observed in an N number of preceding time slices, and determining that a transmitter is temporarily unobservable if a transmitter has been observed in said number of preceding time slices, but is not observable in the current time slice.

11. The method of claim 9 wherein the method further comprises removing RF data that is out of range or temporarily unobservable said step of determining if a transmitter is out of range or temporarily unobservable for a mobile unit at a location is accomplished by determining that a transmitter is out of range if a transmitter has not been observed in an X percentage samples of RF data collected for a mobile unit at that location.

12. The method of claim 1 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises:

a) selecting said collected data for a location related to any said transmitter having an incidence of detection of N; and

b) assigning a unique reference RF fingerprint for a location based on said selected data for that location.

13. The method of claim 1 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises:

a) selecting said collected data related to any said transmitter, said selected RF data having low variance; and

b) assigning a unique reference RF fingerprint for each of said location based on said selected data for each of said locations.

14. The method of claim 1 wherein said step of assigning said reference RF fingerprint for each of said location based on said collected RF data further comprises:

a) determining a subset of transmitters that provides RF data for a location that is distinguished from RF data for the largest number of other locations; and

b) assigning a unique reference RF fingerprint for each said location based on said distinguished RF data for each said location.

15. The method of claim 14 wherein said step of determining a subset of transmitters that provides data for a location that is distinguished from RF data for the largest number of other locations further comprises iteratively adding a transmitter as long as RF data for said location is distinguished from RF data for the largest number of other locations.

37. The method of any one of claims 1, 16, 31-35 further comprising the step of determining cases in which said reference RF fingerprints would apply and tagging said reference RF fingerprints to apply to any of said cases.

16. A method of preparing an area for location determination of a mobile unit comprising the steps of:

a) providing at least two transmitters that are located along different axes with respect to a plurality of locations in said area;

b) collecting RF data of said mobile unit at said locations; and

c) assigning a unique reference RF fingerprint for each of said locations based on said collected RF data for each of said locations.

17. The method of claim 16 wherein said RF data of said mobile unit at locations in said area further comprises RF data related to an orientation of said mobile unit at said locations in said area, said method further comprising assigning a unique reference RF fingerprint for each orientation of said mobile unit at each of said locations based on said collected RF data for each said orientation at said each location.

18. The method of claim 16 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises:

averaging said collected data respective to each location to obtain an average and assigning said reference RF fingerprint respective to each location based each said respective average.

19. The method of claim 17 wherein said step of assigning said reference RF fingerprint for each of said locations and orientations based on said collected RF data further comprises:

averaging said collected data respective to each location and orientation to obtain an average and assigning said reference RF fingerprint respective to each location and orientation based each said respective average.

20. The method of claim 16 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises interpreting said RF data for missed transmissions and wherein said unique reference RF fingerprints are assigned based on said interpreted data.

21. The method of claim 16 wherein said step of assigning said reference RF fingerprint for each of said location based on said collected RF data further comprises:

a) determining if any of said collected RF data respective to each location is outlying;

b) applying a mathematical function to said RF data that is not outlying respective to each location, and obtaining a value from said application of said mathematical function; and

c) assigning a unique reference RF fingerprint for each of said locations based on said respective value.

22. The method of claim 21 wherein outlying RF data is data outside N standard deviations of an average of said RF data for that location.

23. The method of claim 21 wherein outlying RF data is data over N units from an average of said RF data for that location.

24. The method of claim 16 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises:

a) determining if a transmitter is out of range or temporarily unobservable for said mobile unit at a location;

b) applying a mathematical function to said collected data for respective locations that are not temporarily unobservable or out of range and obtaining a value from said application of said mathematical function; and

c) assigning a unique reference RF fingerprint for each of said respective locations based on said respective values.

25. The method of claim 24 wherein said step of determining if a transmitter is out of range or temporarily unobservable for a mobile unit at a location is accomplished by determining that a transmitter is out of range if a transmitter has not been observed in an N number of preceding time slices, and determining that a transmitter is temporarily unobservable if a transmitter has been observed in said number of preceding time slices, but is not observable in the current time slice.

26. The method of claim 24 wherein the method further comprises removing RF data that is out of range or temporarily unobservable said step of determining if a transmitter is out of range or temporarily unobservable for a mobile unit at a location is accomplished by determining that a transmitter is out of range if a transmitter has not been observed in an X percentage samples of RF data collected for a mobile unit at that location.

27. The method of claim 17 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises:

a) selecting said collected data for a location related to any said transmitter having an incidence of detection of N; and

b) assigning a reference RF fingerprint for a location based on said selected data.

28. The method of claim 16 wherein said step of assigning said reference RF fingerprint for each of said locations based on said collected RF data further comprises:

a) selecting said collected data related to any said transmitter, said selected RF data having low variance; and

b) assigning a reference RF fingerprint based on said selected data for each of said locations.

29. The method of claim 16 wherein said step of assigning said reference RF fingerprint for each of said location based on said collected RF data further comprises:

a) determining a subset of transmitters that provides RF data for a location that is distinguished from RF data for the largest number of other locations; and

b) assigning a unique reference RF fingerprint for each said location based on said distinguished RF data for each said location.

30. The method of claim 29 wherein said step of determining a subset of transmitters that provides data for a location that is distinguished from RF data for the largest number of other locations further comprises iteratively adding a transmitter as long as RF data for said location is distinguished from RF data for the largest number of other locations.

31. A method for preparing an area for location determination of a mobile unit, said area having a transmitter associated therewith that is able transmit data to said mobile unit comprising the steps of:

a) collecting RF data of said mobile unit at said locations;

b) applying a mathematical function to said collected data that are not temporarily unobservable and obtaining a value from said application of said mathematical function; and

c) assigning a unique reference RF fingerprint for each of said locations based on said value.

32. A method for preparing an area for location determination of a mobile unit, said area having a transmitter associated therewith that is able transmit data to said mobile unit comprising the steps of:

a) collecting RF data of said mobile unit at said locations;

b) determining if any of said collected RF data is outlying;

c) applying a mathematical function to said collected data that are not outlying and obtaining a value from said application of said mathematical function; and

d) assigning a unique reference RF fingerprint for each of said locations based on said value.

33. A method for preparing an area for location determination of a mobile unit, said area having at least one transmitter associated therewith that is able transmit data to said mobile unit comprising the steps of:

a) collecting RF data of said mobile unit;

b) selecting said collected data related to any of the at least one transmitter having an incidence of detection of N; and

c) assigning a reference RF fingerprint based on selected data.

34. A method for preparing an area for location determination of a mobile unit, said area having at least one transmitter associated therewith that is able transmit data to said mobile unit comprising the steps of:

a) collecting RF data of said mobile unit;

b) selecting said collected data related to any of the at least one transmitter, said selected RF data having low variance; and

c) assigning a reference RF fingerprint based on selected data.

35. A method for preparing an area for location determination of a mobile unit, said mobile unit receiving RF data from a set of transmitters:

a) collecting RF data of said mobile unit in a location in said area;

b) determining a subset of transmitters that provides RF data for a location that is distinguished from RF data for the largest number of other locations; and

c) assigning a reference RF fingerprint based on said distinguished RF data for said location.

36. The method of claim 35 wherein said step of determining a subset of transmitters further comprises iteratively adding a transmitter as long as RF data for said location is distinguished from RF data for the largest number of other locations.

38. A method of determining a location of a mobile unit in an area configured for wireless location determination of said mobile unit, said mobile unit in communication with a transmitter associated to said area comprising the steps of:

a) collecting samples of RF data of a mobile unit at said location;

b) applying a mathematical function to said samples to obtain a value that is used as an RF fingerprint;

c) determining the similarity of said RF fingerprint to location specific data.

39. The method of claim 38 wherein said location specific data is a reference RF fingerprint.

52. The method of claim 38 or 41 further comprising reporting a location estimate based on a rule.

53. The method of claim 52 wherein said rule is to consider said RF fingerprint a location estimate if said RF fingerprint was not previously a location estimate, and said RF fingerprint has a value less than said entry cutoff for said reference RF fingerprint.

54. The method of claim 52 wherein said rule is to consider said RF fingerprint a location estimate if said RF fingerprint was previously a location estimate, and said RF fingerprint has a value less than said exit cutoff for said reference RF fingerprint.

55. The method of claim 52 wherein said rule is to not consider said RF fingerprint a location estimate if said RF fingerprint was previously a location estimate and said RF fingerprint has a value greater than or equal to said exit cutoff for said reference RF fingerprint.

56. The method according to claim 38 or 41 wherein said area comprises subareas and said locations specific data comprises reference RF fingerprints for a set of locations within said subarea, wherein said method further comprises steps of reporting a location estimate based on a rule.

57. The method of claim 56 wherein said rule is to consider said subarea a location estimate if said subarea was not previously a location estimate, and a value for any RF fingerprint with said subarea is less than said entry cutoff.

58. The method of claim 56 wherein said rule is to consider said subarea a location estimate if said subarea was previously a location estimate and a measure for any location within said subarea is less than said exit cutoff.

59. The method of claim 56 wherein said rule is to not consider said subarea a location estimate if said subarea was previously considered a location estimate and all RF fingerprints within said subarea have a measure greater than or equal to said exit cutoff.

60. The method of claim 38 or 41 further comprising eliminating all reference RF fingerprints from consideration if said reference RF fingerprints comprise information from any currently unobservable subtransmitter.

61. The method of claim 38 or 41 further comprising reporting a most probable location estimate.

62. The method of claim 61 wherein said most probable location estimate determined by calculating the probability of the transition from any of said locations to any other of said locations.

63. The method of claim 61 wherein said most probable location estimate is determined by using a probability matrix.

64. The method of claim 52 wherein said rule is to:

a) assign one vote to any location estimate that has been a location estimate any time during a period for each round in which said location estimate was valid;

b) assign additional votes to said any location estimate that had the most number of votes in a last said round;

c) reporting as a location estimate the location estimate having the most number of votes.

65. The method of claim 64 wherein if said location estimates have an equal number of votes, a location estimate having the most number of votes in the previous round is reported as a location estimate.

66. The method of claim 65 wherein if there is no location estimate having the most number of votes in the previous round, reporting a location estimate based on a random choice of said location estimates.

40. The method of 38 wherein said mathematical function is determining a mode, median, or mean.

41. A method of determining a location of a mobile unit in an area configured for wireless location determination of said mobile unit, said mobile unit in communication with a transmitter associated to said area comprising the steps of:

a) collecting at least two samples of RF data of a mobile unit at said location;

b) selecting said samples based on a rule;

c) applying a mathematical function to said selected samples to obtain a value that is used as an RF fingerprint;

d) determining the similarity of said RF fingerprint to location specific data.

42. The method of claim 41 wherein said location specific data is a reference RF fingerprint.

44. The method of claim 41 wherein said rule is to select said collected samples that are not outlying.

45. The method of claim 44 wherein outlying RF data is data outside N standard deviations of an average of said RF data for a location.

46. The method of claim 44 wherein outlying RF data is data over N units from an average of RF data for said respective location.

47. The method of claim 41 wherein said rule is to select collected samples that are not out of range or temporarily unobservable.

48. The method according to claim 47 wherein said rule comprises determining that a transmitter is out of range if a transmitter has not been observed in an N number of preceding time slices, and determining that a transmitter is temporarily unobservable if a transmitter has been observed in said number of preceding time slices, but is not observable in the current time slice.

49. The method according to claim 47 wherein said rule comprises determining that a transmitter is out of range if a transmitter has not been observed in an X percentage of samples of RF data collected for a mobile unit at said respective location.

50. The method of claim 41 wherein said rule is to select collected data related to at least one said transmitter having an incidence of detection above a predefined threshold.

51. The method of claim 41 wherein said rule is to select collected data related to any of said transmitters, said selected data having low variance.

67. The method of claim 41 wherein said RF data samples further comprises RF data related to an orientation of said mobile unit at said location and said step of creating an RF fingerprint for each location based on said value further comprises creating an RF fingerprint for each orientation at each location.

43. The method of 41 wherein said mathematical function is determining a mode, median, or mean.