Location estimation of wireless terminals through pattern matching of deduced and empirical signal-strength measurements

• US 20050014518A1
• Filed: 03/12/2004
• Published: 01/20/2005
• Est. Priority Date: 07/19/2003
• Status: Active Grant

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: Polaris Wireless Incorporated
• Inventors: Spain, David Stevenson Jr., Bhattacharya, Tarun Kumar, Martin, Robert Lewis
• Granted Patent: US 7,116,987 B2
• Time in Patent Office: Days
• US Class Current: 455/456.500
• 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 method of 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. Furthermore, the illustrative embodiment deduces the signal strength of one or more base stations'"'"' control channels at the wireless terminal based on the principal of reciprocity, whether or not the wireless terminal can actually receive the base stations'"'"' control channels but so long as the base station can receive and measure the uplink signal from the wireless terminal. The deduced signal-strength measurements can then used—alone or in combination with the empirical signal-strength measurements—to estimate the location of the wireless terminal.

Claims

1. A method comprising:

receiving a signal-strength measurement for a first downlink signal that is received by a wireless terminal and a signal-strength measurement for an uplink signal that is transmitted by said wireless terminal; and

estimating the location of said wireless terminal based on said signal-strength measurement for said first downlink signal and on said signal-strength measurement for said uplink signal.

2. The method of claim 1 further comprising deducing the signal strength of a second downlink signal at said wireless terminal based on said signal-strength measurement for said uplink signal.

3. The method of claim 2 wherein estimating the location of said wireless terminal comprises pattern matching (i) said signal-strength measurement for said downlink signal and (ii) the deduced signal strength of said downlink signal at said wireless terminal against a map that correlates signal-strength measurements and locations.

4. The method of claim 2 wherein estimating the location of said wireless terminal comprises pattern matching the difference between (i) said signal-strength measurement for said downlink signal and (ii) the deduced signal strength of said downlink signal at said wireless terminal against a map that correlates signal-strength measurements and locations.

5. The method of claim 2 wherein deducing the signal strength of said second downlink signal at said wireless terminal is also based on the transmit strength of said second downlink signal.

6. The method of claim 2 wherein deducing the signal strength of said second downlink signal at said wireless terminal is also based on the transmit strength of said uplink signal.

7. The method of claim 1 further comprising transmitting a request to a mobile switching center to make said signal-strength measurement for said uplink signal.

8. A method comprising:

receiving (i) a first signal-strength measurement for an uplink signal that is transmitted by a wireless terminal and received at a first location and (ii) a second signal-strength measurement for said uplink signal that is transmitted by said wireless terminal and received at a second location;

deducing the signal strength of a first downlink signal at said wireless terminal based on said first signal-strength measurement for said uplink signal;

deducing the signal strength of a second downlink signal at said wireless terminal based on said second signal-strength measurement for said uplink signal; and

estimating the location of said wireless terminal based on the deduced signal strength of said first downlink signal and on the deduced signal strength of said second downlink signal.

9. The method of claim 8 wherein estimating the location of said wireless terminal comprises pattern matching (i) the deduced signal strength of said first downlink signal and (ii) the deduced signal strength of said second downlink signal against a map that correlates signal-strength measurements and locations.

10. The method of claim 8 wherein estimating the location of said wireless terminal comprises pattern matching the difference between (i) the deduced signal strength of said first downlink signal and (ii) the deduced signal strength of said second downlink signal against a map that correlates signal-strength measurements and locations.

11. The method of claim 8 wherein deducing the signal strength of a first downlink signal at said wireless terminal is based on the transmit strength of said first downlink signal.

12. The method of claim 8 wherein deducing the signal strength of a first downlink signal at said wireless terminal is based on the transmit strength of said uplink signal.

13. The method of claim 8 further comprising transmitting a request to a mobile switching center to make said first signal-strength measurement for an uplink signal and said second signal-strength measurement for said uplink signal.

14. The method of claim 8 further comprising receiving a message from a mobile switching center that comprises said first signal-strength measurement for an uplink signal and said second signal-strength measurement for said uplink signal.

15. A method comprising:

transmitting a request to a mobile switching center to make a first signal-strength measurement at a first location and a second signal-strength measurement at a second location for an uplink signal that is transmitted by a wireless terminal;

receiving a message from said mobile switching center that comprises said first signal-strength measurement and said second signal-strength measurement;

deducing the signal strength of a first downlink signal at said wireless terminal based on said first signal-strength measurement;

deducing the signal strength of a second downlink signal at said wireless terminal based on said second signal-strength measurement; and

estimating the location of said wireless terminal based on the deduced signal strength of said first downlink signal and on the deduced signal strength of said second downlink signal.

16. The method of claim 15 wherein estimating the location of said wireless terminal comprises pattern matching (i) the deduced signal strength of said first downlink signal and (ii) the deduced signal strength of said second downlink signal against a map that correlates signal-strength measurements and locations.

17. The method of claim 15 wherein estimating the location of said wireless terminal comprises pattern matching the difference between (i) the deduced signal strength of said first downlink signal and (ii) the deduced signal strength of said second downlink signal against a map that correlates signal-strength measurements and locations.

18. The method of claim 15 wherein deducing the signal strength of a first downlink signal at said wireless terminal is based on the transmit strength of said first downlink signal.

19. The method of claim 15 wherein deducing the signal strength of a first downlink signal at said wireless terminal is based on the transmit strength of said uplink signal.