Estimating the Location of a Wireless Terminal Based on Signal Path Impairment

• US 20060240846A1
• Filed: 05/22/2006
• Published: 10/26/2006
• Est. Priority Date: 09/22/1998
• Status: Active Grant

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: Polaris Wireless Incorporated
• Inventors: Gordon, Scot Douglas, Spain, David Stevenson Jr., Feuerstein, Martin, Bhattacharya, Tarun Kumar
• Granted Patent: US 7,734,298 B2
• Time in Patent Office: Days
• US Class Current: 455/456.100
• CPC Class Codes: G01S 19/06 employing an initial estimate of the location of the receiver as aiding data or in generating aiding data
• CPC Class Codes: G01S 19/17 Emergency applications
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A technique for estimating the location of a wireless terminal at an unknown location in a geographic region is disclosed. The technique is based on the recognition that there are traits of electromagnetic signals that are dependent on topography, the receiver, the location of the transmitter, and other factors. For example, if a particular radio station is known to be received strongly at a first location and weakly at a second location, and a given wireless terminal at an unknown location is receiving the radio station weakly, it is more likely that the wireless terminal is at the second location than at the first location.

Claims

1. A method comprising estimating the location of a wireless terminal based on a measured pathloss of a signal as processed by said wireless terminal.

2. The method of claim 1 wherein said wireless terminal receives said signal.

3. The method of claim 1 wherein said wireless terminal transmits said signal.

4. The method of claim 1 wherein estimating the location of said wireless terminal comprises comparing said measured pathloss to:

(i) a first expected pathloss of said of said signal when said wireless terminal is at a first location, and

(ii) a second expected pathloss of said of said signal when said wireless terminal is at a second location.

5. A method comprising:

(1) receiving (i) a first measured pathloss for a first signal that is processed by a wireless terminal and (ii) a second measured pathloss for a second of a second signal that is processed by said wireless terminal; and

(2) estimating the location of said wireless terminal based on said first measured pathloss and said second measured pathloss.

6. The method of claim 5 wherein said wireless terminal receives said first signal and said second signal.

7. The method of claim 5 wherein said wireless terminal transmits said first signal and said second signal.

8. The method of claim 5 wherein said wireless terminal receives said first signal and transmits said second signal.

9. The method of claim 5 wherein (2) estimating the location of said wireless terminal comprises:

(2.1) comparing said first measured pathloss to;

(i) a first expected pathloss of said first signal when said wireless terminal is at a first location, and

(ii) a second expected pathloss of said first signal when said wireless terminal is at a second location; and

(2.2) comparing said second measured pathloss to;

(i) a first expected pathloss of said second of said second signal when said wireless terminal is at said first location, and

(ii) a second expected pathloss of said second of said second signal when said wireless terminal is at said second location.

10. A method comprising:

(1) receiving (i) a first measured pathloss for a first signal that is processed by a wireless terminal at a first time T₁ and (ii) a second measured pathloss for said first signal at a second time T₂, wherein said first time does not equal said second time; and

(2) estimating the location of said wireless terminal at said second time based on (i) said first measured pathloss, (ii) said second measured pathloss, and (iii) an estimate of the probability that said wireless terminal in said location at time T will still be in said location at time T+Δ

t.

11. The method of claim 10 wherein said wireless terminal receives said first signal and said second signal.

12. The method of claim 10 wherein said wireless terminal transmits said first signal and said second signal.

13. The method of claim 10 wherein said wireless terminal receives said first signal and transmits said second signal.

14. The method of claim 10 wherein (2) estimating the location of said wireless terminal comprises:

(2.1) comparing said first measured pathloss to;

(i) a first expected pathloss of said first signal when said wireless terminal is at a first location at said first time T₁, and

(ii) a second expected pathloss of said first signal when said wireless terminal is at a second location at said first time T₁; and

(2.2) comparing said second measured pathloss to;

(i) a first expected pathloss of said second of said second signal when said wireless terminal is at said first location at said first time T₂, and

(ii) a second expected pathloss of said second of said second signal when said wireless terminal is at said second location at said first time T₂.

15. A method comprising estimating the location of a wireless terminal based on a measured error rate of a signal as processed by said wireless terminal.

16. The method of claim 15 wherein said wireless terminal receives said signal;

and

wherein said measured error rate is measured at said wireless terminal.

17. The method of claim 15 wherein said wireless terminal transmits said signal;

and

wherein said measured error rate is measured at a base station.

18. The method of claim 15 wherein estimating the location of said wireless terminal comprises comparing said measured error rate to:

(i) a first expected error rate of said signal when said wireless terminal is at a first location, and

(ii) a second expected error rate of said signal when said wireless terminal is at a second location.

19. A method comprising:

(1) receiving (i) a first measured error rate for a first pair of multipath components of a first signal that is processed by a wireless terminal and (ii) a second measured error rate for a second signal that is processed by said wireless terminal; and

(2) estimating the location of said wireless terminal based on said first measured error rate and said second measured error rate.

20. The method of claim 19 wherein said wireless terminal receives said first signal and said second signal;

and

wherein said first measured error rate and said second measured error rate are measured at said wireless terminal.

21. The method of claim 19 wherein said wireless terminal transmits said first signal and said second signal;

and

wherein said first measured error rate is measured at a first base station and said second measured error rate is measured at a second base station.

22. The method of claim 19 wherein said wireless terminal receives said first signal and transmits said second signal;

and

wherein said first measured error rate is measured at said wireless terminal and said second measured error rate is measured at a base station.

23. The method of claim 19 wherein (2) estimating the location of said wireless terminal comprises:

(2.1) comparing said first measured error rate to;

(i) a first expected error rate of said first pair of multipath components of said first signal when said wireless terminal is at a first location, and

(ii) a second expected error rate of said first pair of multipath components of said first signal when said wireless terminal is at a second location; and

(2.2) comparing said second measured error rate to;

(i) a first expected error rate of said second pair of multipath components of said second signal when said wireless terminal is at said first location, and

(ii) a second expected error rate of said second pair of multipath components of said second signal when said wireless terminal is at said second location.

24. A method comprising:

(1) receiving (i) a first measured error rate for a first pair of multipath components of a first signal that is processed by a wireless terminal at a first time T₁ and (ii) a second measured error rate for said first pair of multipath components of said first signal at a second time T₂, wherein said first time does not equal said second time; and

(2) estimating the location of said wireless terminal at said second time based on (i) said first measured error rate, (ii) said second measured error rate, and (iii) an estimate of the probability that said wireless terminal in said location at time Twill still be in said location at time T+Δ

t.

25. The method of claim 24 wherein said wireless terminal receives said first signal and said second signal;

and

wherein said first measured error rate and said second measured error rate are measured at said wireless terminal.

26. The method of claim 24 wherein said wireless terminal transmits said first signal and said second signal;

and

wherein said first measured error rate is measured at a first base station and said second measured error rate is measured at a second base station.

27. The method of claim 24 wherein said wireless terminal receives said first signal and transmits said second signal;

and

wherein said first measured error rate is measured at said wireless terminal and said second measured error rate is measured at a base station.

28. The method of claim 24 wherein (2) estimating the location of said wireless terminal comprises:

(2.1) comparing said first measured error rate to;

(i) a first expected error rate of said first pair of multipath components of said first signal when said wireless terminal is at a first location at said first time T₁, and

(ii) a second expected error rate of said first pair of multipath components of said first signal when said wireless terminal is at a second location at said first time T₁; and

(2.2) comparing said second measured error rate to;

(i) a first expected error rate of said second pair of multipath components of said second signal when said wireless terminal is at said first location at said first time T₂, and

(ii) a second expected error rate of said second pair of multipath components of said second signal when said wireless terminal is at said second location at said first time T₂.

39. The method of claim 24 wherein said wireless terminal receives said first signal and said second signal;

and

wherein said first measured signal-to-impairment ratio and said second measured signal-to-impairment ratio are measured at said wireless terminal.

40. The method of claim 24 wherein said wireless terminal transmits said first signal and said second signal;

and

wherein said first measured signal-to-impairment ratio is measured at a first base station and said second measured signal-to-impairment ratio is measured at a second base station.

41. The method of claim 24 wherein said wireless terminal receives said first signal and transmits said second signal;

and

wherein said first measured signal-to-impairment ratio is measured at said wireless terminal and said second measured signal-to-impairment ratio is measured at a base station.

42. The method of claim 24 wherein (2) estimating the location of said wireless terminal comprises:

(2.1) comparing said first measured signal-to-impairment ratio to;

(i) a first expected signal-to-impairment ratio of said first pair of multipath components of said first signal when said wireless terminal is at a first location at said first time T₁, and

(ii) a second expected signal-to-impairment ratio of said first pair of multipath components of said first signal when said wireless terminal is at a second location at said first time T₁; and

(2.2) comparing said second measured signal-to-impairment ratio to;

(i) a first expected signal-to-impairment ratio of said second pair of multipath components of said second signal when said wireless terminal is at said first location at said first time T₂, and

(ii) a second expected signal-to-impairment ratio of said second pair of multipath components of said second signal when said wireless terminal is at said second location at said first time T₂.

29. A method comprising estimating the location of a wireless terminal based on a measured signal-to-impairment ratio of a signal as processed by said wireless terminal.

30. The method of claim 29 wherein said wireless terminal receives said signal;

and

wherein said measured signal-to-impairment ratio is measured at said wireless terminal.

31. The method of claim 29 wherein said wireless terminal transmits said signal;

and

wherein said measured signal-to-impairment ratio is measured at a base station.

32. The method of claim 29 wherein estimating the location of said wireless terminal comprises comparing said measured signal-to-impairment ratio to:

(i) a first expected signal-to-impairment ratio of said signal when said wireless terminal is at a first location, and

(ii) a second expected signal-to-impairment ratio of said signal when said wireless terminal is at a second location.

33. A method comprising:

(1) receiving (i) a first measured signal-to-impairment ratio for a first pair of multipath components of a first signal that is processed by a wireless terminal and (ii) a second measured signal-to-impairment ratio for a second signal that is processed by said wireless terminal; and

(2) estimating the location of said wireless terminal based on said first measured signal-to-impairment ratio and said second measured signal-to-impairment ratio.

34. The method of claim 33 wherein said wireless terminal receives said first signal and said second signal;

and

wherein said first measured signal-to-impairment ratio and said second measured signal-to-impairment ratio are measured at said wireless terminal.

35. The method of claim 33 wherein said wireless terminal transmits said first signal and said second signal;

and

wherein said first measured signal-to-impairment ratio is measured at a first base station and said second measured signal-to-impairment ratio is measured at a second base station.

36. The method of claim 33 wherein said wireless terminal receives said first signal and transmits said second signal;

and

wherein said first measured signal-to-impairment ratio is measured at said wireless terminal and said second measured signal-to-impairment ratio is measured at a base station.

37. The method of claim 33 wherein (2) estimating the location of said wireless terminal comprises:

(2.1) comparing said first measured signal-to-impairment ratio to;

(i) a first expected signal-to-impairment ratio of said first pair of multipath components of said first signal when said wireless terminal is at a first location, and

(ii) a second expected signal-to-impairment ratio of said first pair of multipath components of said first signal when said wireless terminal is at a second location; and

(2.2) comparing said second measured signal-to-impairment ratio to;

(i) a first expected signal-to-impairment ratio of said second pair of multipath components of said second signal when said wireless terminal is at said first location, and

(ii) a second expected signal-to-impairment ratio of said second pair of multipath components of said second signal when said wireless terminal is at said second location.

38. A method comprising:

(1) receiving (i) a first measured signal-to-impairment ratio for a first pair of multipath components of a first signal that is processed by a wireless terminal at a first time T₁ and (ii) a second measured signal-to-impairment ratio for said first pair of multipath components of said first signal at a second time T₂, wherein said first time does not equal said second time; and

(2) estimating the location of said wireless terminal at said second time based on (i) said first measured signal-to-impairment ratio, (ii) said second measured signal-to-impairment ratio, and (iii) an estimate of the probability that said wireless terminal in said location at time Twill still be in said location at time T+Δ

t.