Estimating the location of a wireless terminal based on calibrated signal-strength measurements

• US 7,796,966 B2
• Filed: 03/15/2005
• Issued: 09/14/2010
• Est. Priority Date: 03/15/2005
• Status: Active Grant

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: Polaris Wireless Incorporated
• Inventors: Spain, David Stevenson Jr., Feuerstein, Martin, Bhattacharya, Tarun Kumar
• Primary Examiner(s): Dao; Minh D
• Application Number:
  US11/080,861
• Publication Number:
  US 20060211376A1
• Time in Patent Office: 2,009 Days
• Field of Search: 455/67.11, 455/67.13, 455/67.14, 455/115.3, 455/456.1, 455/63.1
• US Class Current: 455/231
• CPC Class Codes: G01S 5/02527 Detecting or resolving anomalies in the radio frequency fingerprints of 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

A process and machine for estimating the location of a wireless terminal is disclosed. The illustrative embodiment of the present invention is based on the observation that the signal strength of a signal from a transmitter is different at some locations, and, therefore, the location of a wireless terminal can be estimated by comparing the signal strength it currently observes against a map or database that correlates locations to signal strengths. In accordance with a first example, if a particular radio station is known to be received well at a first location and poorly at a second location, and a given wireless terminal at an unknown location is receiving the radio station poorly, it is more likely that the wireless terminal is at the second location than it is at the first location.

Claims

1. A process comprising:

receiving a first reported signal-strength measurement, R(1,n), from a wireless terminal;

generating a first calibrated signal-strength measurement, S(1,n), based on;

(i) the first reported signal-strength measurement, R(1,n), and (ii) an identifying characteristic, C, of the wireless terminal;

receiving a second reported signal-strength measurement, R(2,n), from the wireless terminal; and

generating a second calibrated signal-strength measurement, S(2,n), based on;

(i) the second reported signal-strength measurement, R(2,n), and (ii) the identifying characteristic, C;

wherein the first reported signal-strength measurement, R(1,n), and the second reported signal-strength measurement, R(2,n), are based on measurements of different signals at substantially the same time.

2. The process of claim 1 further comprising estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n), and on the second calibrated signal-strength measurement, S(2,n).

3. The process of claim 1 further comprising estimating the location of the wireless terminal based on the difference between the first calibrated signal-strength measurement, S(1,n), and the second calibrated signal-strength measurement, S(2,n).

4. A process comprising:

receiving a first reported signal-strength measurement, R(1,n), from a wireless terminal;

generating a first calibrated signal-strength measurement, S(1,n), based on;

(i) the first reported signal-strength measurement, R(1,n), and (ii) an identifying characteristic, C, of the wireless terminal;

receiving a second reported signal-strength measurement, R(1,n+1), from the wireless terminal; and

generating a second calibrated signal-strength measurement, S(1,n+1), based on;

(i) the second reported signal-strength measurement, R(1,n+1), and (ii) the identifying characteristic, C;

wherein the first reported signal-strength measurement, R(1,n), and the second reported signal-strength measurement, R(1,n+1), are based on measurements of the same signal at different times.

5. The process of claim 4 further comprising estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n), and on the second calibrated signal-strength measurement, S(1,n+1).

6. A machine comprising:

a receiver for receiving a first reported signal-strength measurement, R(1,n), from a wireless terminal; and

a processor for generating a first calibrated signal-strength measurement, S(1,n), based on;

(i) the first reported signal-strength measurement, R(1,n), and (ii) an identifying characteristic, C, of the wireless terminal;

wherein the receiver is also for receiving a second reported signal-strength measurement, R(2,n), from the wireless terminal; and

wherein the processor is also for generating a second calibrated signal-strength measurement, S(2,n), based on;

(i) the second reported signal-strength measurement, R(2,n), and (ii) the identifying characteristic, C; and

wherein the first reported signal-strength measurement, R(1,n), and the second reported signal-strength measurement, R(2,n), are based on measurements of different signals at substantially the same time.

7. The machine of claim 6 wherein the processor is also for estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n), and on the second calibrated signal-strength measurement, S(2,n).

8. The machine of claim 6 wherein the processor is also for estimating the location of the wireless terminal based on the difference between the first calibrated signal-strength measurement, S(1,n), and the second calibrated signal-strength measurement, S(2,n).

9. A machine comprising:

a receiver for receiving a first reported signal-strength measurement, R(1,n), from a wireless terminal; and

a processor for generating a first calibrated signal-strength measurement, S(1,n), based on;

(i) the first reported signal-strength measurement, R(1,n), and (ii) an identifying characteristic, C, of the wireless terminal;

wherein the receiver is also for receiving a second reported signal-strength measurement, R(1,n+1), from the wireless terminal; and

wherein the processor is also for generating a second calibrated signal-strength measurement, S(1,n+1), based on;

(i) the second reported signal-strength measurement, R(1,n+1), and (ii) the identifying characteristic, C; and

wherein the first reported signal-strength measurement, R(1,n), and the second reported signal-strength measurement, R(1,n+1), are based on measurements of the same signal at different times.

10. The machine of claim 9 wherein the processor is also for estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n), and on the second calibrated signal-strength measurement, S(1,n+1).

11. A process comprising:

generating a first calibrated signal-strength measurement, S(1,n), based on (i) a first reported signal-strength measurement, R(1,n), as made by a wireless terminal and (ii) an identifying characteristic, C, of the wireless terminal;

estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n);

generating a second calibrated signal-strength measurement, S(2,n), based on (i) a second reported signal-strength measurement, R(2,n), as made by the wireless terminal and (ii) the identifying characteristic, C, of the wireless terminal;

wherein the first reported signal-strength measurement, R(1,n), and the second reported signal-strength measurement, R(2,n), are based on measurements of different signals at substantially the same time.

12. The process of claim 11 further comprising estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n), and on the second calibrated signal-strength measurement, S(2,n).

13. The process of claim 11 further comprising estimating the location of the wireless terminal based on the difference between the first calibrated signal-strength measurement, S(1,n), and the second calibrated signal-strength measurement, S(2,n).

14. A process comprising:

generating a first calibrated signal-strength measurement, S(1,n), based on (i) a first reported signal-strength measurement, R(1,n), as made by a wireless terminal and (ii) an identifying characteristic, C, of the wireless terminal;

estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n);

generating a second calibrated signal-strength measurement, S(1,n+1), based on (i) a second reported signal-strength measurement, R(1,n+1), as made by the wireless terminal and (ii) the identifying characteristic, C, of the wireless terminal;

wherein the first reported signal-strength measurement, R(1,n), and the second reported signal-strength measurement, R(1,n+1), are based on measurements of the same signal at different times.

15. The process of claim 14 further comprising estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n+1), and on the second calibrated signal-strength measurement, S(2,n+1).

16. A machine comprising:

a receiver for receiving a first reported signal-strength measurement, R(1,n), as made by a wireless terminal; and

a processor for;

(a) generating a first calibrated signal-strength measurement, S(1,n), based on (i) the first reported signal-strength measurement, R(1,n), and (ii) a identifying characteristic, C, of the wireless terminal; and

(b) estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n);

wherein the processor is also for generating a second calibrated signal-strength measurement, S(2,n), based on (i) a second reported signal-strength measurement, R(2,n), as made by the wireless terminal and (ii) the identifying characteristic, C, of the wireless terminal; and

wherein the first reported signal-strength measurement, R(1,n), and the second reported signal-strength measurement, R(2,n), are based on measurements of different signals at substantially the same time.

17. The machine of claim 16 wherein the processor is also for estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n), and on the second calibrated signal-strength measurement, S(2,n).

18. The machine of claim 16 wherein the processor is also for estimating the location of the wireless terminal based on the difference between the first calibrated signal-strength measurement, S(1,n), and the second calibrated signal-strength measurement, S(2,n).

19. A machine comprising:

a receiver for receiving a first reported signal-strength measurement, R(1,n), as made by a wireless terminal; and

a processor for;

(a) generating a first calibrated signal-strength measurement, S(1,n), based on (i) the first reported signal-strength measurement, R(1,n), and (ii) a identifying characteristic, C, of the wireless terminal; and

(b) estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n);

wherein the processor is also for generating a second calibrated signal-strength measurement, S(1,n+1), based on (i) a second reported signal-strength measurement, R(1,n+1), as made by the wireless terminal and (ii) the identifying characteristic, C, of the wireless terminal; and

wherein the first reported signal-strength measurement, R(1,n), and the second reported signal-strength measurement, R(1,n+1), are based on measurements of the same signal at different times.

20. The machine of claim 19 wherein the processor is also for estimating the location of the wireless terminal based on the first calibrated signal-strength measurement, S(1,n+1), and on the second calibrated signal-strength measurement, S(2,n+1).