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

• US 20100245115A1
• Filed: 06/07/2010
• Published: 09/30/2010
• Est. Priority Date: 09/22/1998
• Status: Active Grant

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: Polaris Wireless Incorporated
• Inventors: Spain, David Stevenson JR., Gordon, Scot Douglas, Feuerstein, Martin, Bhattacharya, Tarun Kumar
• Granted Patent: US 8,583,141 B2
• Time in Patent Office: Days
• US Class Current: 340/825.490
• 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 5/0252 Radio frequency fingerprinting
• 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 for a signal as processed by the wireless terminal.

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

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

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

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

(ii) a second expected pathloss for the signal when the 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 signal that is processed by the wireless terminal; and

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

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

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

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

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

(2.1) comparing the first measured pathloss to;

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

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

(2.2) comparing the second measured pathloss to;

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

(ii) a second expected pathloss for the second signal when the wireless terminal is at the 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 the first signal at a second time T₂, wherein the first time does not equal the second time; and

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

t.

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

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

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

14. A method comprising:

estimating the location of a wireless terminal based on a measured error rate for a signal as processed by the wireless terminal.

15. The method of claim 14 wherein the wireless terminal receives the signal;

and

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

16. The method of claim 14 wherein the wireless terminal transmits the signal;

and

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

17. The method of claim 14 wherein estimating the location of the wireless terminal comprises comparing the measured error rate to:

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

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

18. A method comprising:

(1) receiving (i) a first measured error rate for 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 the wireless terminal; and

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

19. The method of claim 18 wherein the wireless terminal receives the first signal and the second signal;

and

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

20. The method of claim 18 wherein the wireless terminal transmits the first signal and the second signal;

and

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

21. The method of claim 18 wherein the wireless terminal receives the first signal and transmits the second signal;

and

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

22. The method of claim 18 wherein (2) estimating the location of the wireless terminal comprises:

(2.1) comparing the first measured error rate to;

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

(ii) a second expected error rate for the first signal when the wireless terminal is at a second location; and

(2.2) comparing the second measured error rate to;

(i) a first expected error rate for the second signal when the wireless terminal is at the first location, and

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

23. A method comprising:

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

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

t.

24. The method of claim 23 wherein the wireless terminal receives the first signal and the second signal;

and

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

25. The method of claim 23 wherein the wireless terminal transmits the first signal and the second signal;

and

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

26. The method of claim 23 wherein the wireless terminal receives the first signal and transmits the second signal;

and

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

27. A method comprising:

estimating the location of a wireless terminal based on a measured signal-to-impairment ratio for a signal as processed by the wireless terminal.

28. The method of claim 27 wherein the wireless terminal receives the signal;

and

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

29. The method of claim 27 wherein the wireless terminal transmits the signal;

and

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

30. The method of claim 27 wherein estimating the location of the wireless terminal comprises comparing the measured signal-to-impairment ratio to:

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

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

31. A method comprising:

(1) receiving (i) a first measured signal-to-impairment ratio for 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 the wireless terminal; and

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

32. The method of claim 31 wherein the wireless terminal receives the first signal and the second signal;

and

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

33. The method of claim 31 wherein the wireless terminal transmits the first signal and the second signal;

and

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

34. The method of claim 31 wherein the wireless terminal receives the first signal and transmits the second signal;

and

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

35. The method of claim 31 wherein (2) estimating the location of the wireless terminal comprises:

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

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

(ii) a second expected signal-to-impairment ratio for the first signal when the wireless terminal is at a second location; and

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

(i) a first expected signal-to-impairment ratio for the second signal when the wireless terminal is at the first location, and

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

36. A method comprising:

(1) receiving (i) a first measured signal-to-impairment ratio for 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 the first signal at a second time T₂, wherein the first time does not equal the second time; and

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

t.

37. The method of claim 36 wherein the wireless terminal receives the first signal and the second signal;

and

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

38. The method of claim 36 wherein the wireless terminal transmits the first signal and the second signal;

and

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

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

and

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