Location estimation of wireless terminals through pattern matching of deduced signal strengths
A method of estimating the location of a wireless terminal without the addition of hardware to either the wireless terminal or to the telecommunication system's base stations 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. Furthermore, the illustrative embodiment deduces the signal strength of the serving base station's control channel signal at the wireless terminal, R D , based on the principal of reciprocity.
1. A method comprising:
receiving, by a location system, a report of a signal-strength measurement for a first signal, R 1 , at a wireless terminal;
when said location system does not receive a report of a signal strength of a second signal, R D , at said wireless terminal, deducing, by said location system, said signal strength of said second signal, R D , based on a transmit strength of a third signal, T U , that is transmitted by said wireless terminal; and
estimating the location of said wireless terminal based on:
(i) said signal strength measurement of said first signal, R 1 , and
(ii) said deduced signal strength of said second signal, R D .
2. The method of claim 1 wherein deducing said signal strength of said second signal, R D , is also based on a transmit strength of said second signal, T D .
3. The method of claim 1 wherein deducing said signal strength of said second signal, R D , is also based on a signal-strength measurement for said third signal, R U , at the location where said first signal is transmitted.
4. The method of claim 1 wherein deducing said signal strength of said second signal, R D , is also based on an attenuation for said third signal, A U , between said wireless terminal and the location where said first signal is transmitted.
5. The method of claim 1 wherein estimating the location of said wireless terminal comprises pattern matching said deduced signal strength of said second signal, R D , against a database that associates candidate locations for said wireless terminal with predicted signal-strength measurements for said second signal.
6. The method of claim 1 wherein estimating the location of said wireless terminal is based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
7. The method of claim 1 wherein estimating the location of said wireless terminal comprises generating a two-dimensional probability distribution for the location of said wireless terminal based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
8. A method comprising:
receiving, by a location system, a report of a signal-strength measurement for a first signal, R 1 , at a wireless terminal;
when said location system does not receive a report of a signal strength of a second signal, R D , at said wireless terminal, deducing, by said location system, said signal strength of said second signal, R D , based on a signal-strength measurement of a third signal, R U , at the location where said second signal is transmitted; and
estimating the location of said wireless terminal based on:
(i) said signal strength measurement of said first signal, R 1 , and
(ii) said deduced signal strength of said second signal, R D .
9. The method of claim 8 wherein deducing said signal strength of said second signal, R D , is also based on a transmit strength of said second signal, T D .
10. The method of claim 8 wherein deducing said signal strength of said second signal, R D , is also based on a transmit strength of said third signal, T U , that is transmitted by said wireless terminal.
11. The method of claim 8 wherein deducing said signal strength of said second signal, R D , is also based on an attenuation for said third signal, A U , between said wireless terminal and the location where said second signal is transmitted.
12. The method of claim 8 wherein estimating the location of said wireless terminal comprises pattern matching said deduced signal strength of said second signal, R D , against a database that associates candidate locations for said wireless terminal with predicted signal-strength measurements for said second signal.
13. The method of claim 8 wherein estimating the location of said wireless terminal is based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
14. The method of claim 8 wherein estimating the location of said wireless terminal comprises generating a two-dimensional probability distribution for the location of said wireless terminal based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
15. The method of claim 8 further comprising removing the effects of fast fading on R U .
16. A method comprising:
receiving, by a location system, a report of a signal-strength measurement for a first signal, R 1 , at a wireless terminal;
when said location system does not receive a report of a signal strength of a second signal, R D , at said wireless terminal, deducing, by said location system, said signal strength of said second signal, R D , based on an attenuation of a third signal, A U , that is transmitted by said wireless terminal; and
estimating the location of said wireless terminal based on:
(i) said signal strength measurement of said first signal, R 1 , and
(ii) said deduced signal strength of said second signal, R D .
17. The method of claim 16 wherein deducing said signal strength of said second signal, R D , is also based on a transmit strength of said second signal, T D .
18. The method of claim 16 wherein deducing said signal strength of said second signal, R D , is also based on a signal-strength measurement for said third signal, R U , at the location where said second signal is transmitted.
19. The method of claim 16 wherein deducing said signal strength of said second signal, R D , is also based on a transmit strength of said third signal, T U .
20. The method of claim 16 wherein estimating the location of said wireless terminal comprises pattern matching said deduced signal strength of said second signal, R D , against a database that associates candidate locations for said wireless terminal with predicted signal-strength measurements for said second signal.
21. The method of claim 16 wherein estimating the location of said wireless terminal is based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
22. The method of claim 16 wherein estimating the location of said wireless terminal comprises generating a two-dimensional probability distribution for the location of said wireless terminal based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
23. A location system for estimating the location of a wireless terminal, the location system comprising:
a receiver for receiving a report of a signal-strength measurement for a first signal, R 1 , at said wireless terminal; and
a processor for:
(A) when said receiver does not receive a report of a signal strength of a second signal, R D , at said wireless terminal, deducing said signal strength of said second signal, R D , based on a transmit strength of a third signal, T U , that is transmitted by said wireless terminal, and
(B) estimating the location of said wireless terminal based on:
(i) said signal strength measurement of said first signal, R 1 , and
(ii) said deduced signal strength of said second signal, R D .
24. The location system of claim 23 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on a transmit strength of said second signal, T D .
25. The location system of claim 23 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on a signal-strength measurement for said third signal, R U , at the location where said first signal is transmitted.
26. The location system of claim 23 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on an attenuation for said third signal, A U , between said wireless terminal and the location where said first signal is transmitted.
27. The location system of claim 23 further comprising:
a memory, which is non-volatile, for storing a database that associates candidate locations for said wireless terminal with predicted signal-strength measurements for said second signal, R D ; and
wherein said estimating by said processor of the location of said wireless terminal comprises pattern matching said deduced signal strength of said second signal, R D , against said database.
28. The location system of claim 23 wherein said estimating by said processor of the location of said wireless terminal is based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
29. The location system of claim 23 wherein said estimating by said processor of the location of said wireless terminal comprises generating a two-dimensional probability distribution for the location of said wireless terminal based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
30. A location system for estimating the location of a wireless terminal, the location system comprising:
a receiver for receiving a report of a signal-strength measurement for a first signal, R 1 , at said wireless terminal; and
a processor for:
(A) when said receiver does not receive a report of a signal strength of a second signal, R D , at said wireless terminal, deducing said signal strength of said second signal, R D , based on a signal-strength measurement of a third signal, R U , at the location where said second signal is transmitted, and
(B) estimating the location of said wireless terminal based on:
(i) said signal strength measurement of said first signal, R 1 , and
(ii) said deduced signal strength of said second signal, R D .
31. The location system of claim 30 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on a transmit strength of said second signal, T D .
32. The location system of claim 30 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on a transmit strength of said third signal, T U , that is transmitted by said wireless terminal.
33. The location system of claim 30 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on an attenuation for said third signal, A U , between said wireless terminal and the location where said second signal is transmitted.
34. The location system of claim 30 further comprising:
a memory, which is non-volatile, for storing a database that associates candidate locations for said wireless terminal with predicted signal-strength measurements for said second signal, R D ; and
wherein said estimating by said processor of the location of said wireless terminal comprises pattern matching said deduced signal strength of said second signal, R D , against said database.
35. The location system of claim 30 wherein said estimating by said processor of the location of said wireless terminal comprises generating a two-dimensional probability distribution for the location of said wireless terminal based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
36. A location system for estimating the location of a wireless terminal, the location system comprising:
a receiver for receiving a report of a signal-strength measurement for a first signal, R 1 , at said wireless terminal; and
a processor for:
(A) when said receiver does not receive a report of a signal strength of a second signal, R D , at said wireless terminal, deducing said signal strength of said second signal, R D , based on an attenuation of a third signal, A U , that is transmitted by said wireless terminal, and
(B) estimating the location of said wireless terminal based on:
(i) said signal strength measurement of said first signal, R 1 , and
(ii) said deduced signal strength of said second signal, R D .
37. The location system of claim 36 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on a transmit strength of said second signal, T D .
38. The location system of claim 36 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on a signal-strength measurement for said third signal, R U , at the location where said second signal is transmitted.
39. The location system of claim 36 wherein said deducing by said processor of said signal strength of said second signal, R D , is also based on a transmit strength of said third signal, T U .
40. The location system of claim 36 further comprising:
a memory, which is non-volatile, for storing a database that associates candidate locations for said wireless terminal with predicted signal-strength measurements for said second signal, R D ; and
wherein said estimating by said processor of the location of said wireless terminal comprises pattern matching said deduced signal strength of said second signal, R D , against said database.
41. The location system of claim 36 wherein said estimating by said processor of the location of said wireless terminal is based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .
42. The location system of claim 36 wherein said estimating by said processor of the location of said wireless terminal comprises generating a two-dimensional probability distribution for the location of said wireless terminal based on the absolute magnitude of the difference between said deduced signal strength of said second signal, R D , and said signal-strength measurement of said first signal, R 1 .