Location estimation of wireless terminals based on combinations of signal strength measurements and geometry-of-arrival measurements

• US 7,233,799 B2
• Filed: 01/05/2004
• Issued: 06/19/2007
• Est. Priority Date: 02/24/2003
• Status: Active Grant

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: Polaris Wireless Incorporated
• Inventors: Spain, David Stevenson Jr.
• Primary Examiner(s): Trost; William
• Assistant Examiner(s): Santiago-Cordero; Marivelisse
• Application Number:
  US10/751,790
• Publication Number:
  US 20040180671A1
• Time in Patent Office: 1,261 Days
• Field of Search: 455/456.1, 455/456.2, 455/456.3, 455/457, 455/456.4, 455/456.7, 455/456.6
• US Class Current: 455/456.1
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method and apparatus for estimating the location of a wireless terminal are disclosed. The location of the wireless terminal is estimated based on one or more signal strength measurements in conjunction with: (i) one or more angle-of-arrival measurements, (ii) one or more time-of-arrival measurements, or (iii) a combination of (i) and (ii). At each measurement time, the illustrative embodiment (a) determines the candidate locations for the wireless terminal, (b) computes a measurement likelihood function for any signal strength measurements that are available at that time, (c) computes a measurement likelihood function for any geometry-of-arrival measurements that are available at that time, (d) computes a joint likelihood function for all measurements available at that time, and (e) updates the location probability distribution for the wireless terminal with the joint measurement likelihood function. Estimates of the location of the wireless terminal are obtained from the location probability distribution.

Claims

1. A method comprising:

receiving

(i) a first signal measurement for a first signal as received by a wireless terminal, and

(ii) a second signal measurement for a second signal as transmitted by said wireless terminal;

generating a first multi-dimensional probability distribution for the location of said wireless terminal based on said first signal measurement;

generating a second multi-dimensional probability distribution for the location of said wireless terminal based on a comparison of said second signal measurement to a predicted value of said second signal measurement; and

estimating the location of said wireless terminal based on

(i) said first multi-dimensional probability distribution, and

(ii) said second multi-dimensional probability distribution;

wherein estimating the location of said wireless terminal comprises;

pruning a first list of candidate locations for said wireless terminal to a second list of candidate locations of said wireless terminal based on said first signal measurement; and

choosing an estimated location for said wireless terminal based on said second list of locations and said second signal measurement.

2. A method comprising:

receiving

(i) a first signal measurement for a first signal as received by a wireless terminal, and

(ii) a second signal measurement for a second signal as transmitted by said wireless terminal;

generating a first multi-dimensional probability distribution for the location of said wireless terminal based on said first signal measurement;

generating a second multi-dimensional probability distribution for the location of said wireless terminal based on a comparison of said second signal measurement to a predicted value of said second signal measurement; and

estimating the location of said wireless terminal based on

(i) said first multi-dimensional probability distribution, and

(ii) said second multi-dimensional probability distribution;

wherein estimating the location of said wireless terminal comprises;

pruning a first list of candidate locations for said wireless terminal to a second list of candidate locations of said wireless terminal based on said second signal measurement; and

choosing an estimated location for said wireless terminal based on said second list of locations and said first signal measurement.

3. A method comprising:

receiving

(i) a signal strength measurement for a first signal as received by a wireless terminal,

(ii) a first time-of-arrival measurement for a second signal as received by said wireless terminal, wherein said second signal is transmitted by a first Earth satellite, and

(iii) a second time-of-arrival measurement for a third signal as received by said wireless terminal, wherein said third signal is transmitted by a second Earth satellite,

matching said signal strength measurement against a database that associates locations with signal measurements to generate a first multi-dimensional probability distribution for the location of said wireless terminal;

generating a second probability distribution for the location of said wireless terminal based on said first time-of-arrival measurement and said second time-of-arrival measurement; and

estimating the location of said wireless terminal based on;

(i) said first multi-dimensional probability distribution, and

(ii) said second multi-dimensional probability distribution;

wherein estimating the location of said wireless terminal comprises;

pruning a first list of candidate locations for said wireless terminal to a second list of candidate locations of said wireless terminal based on said second first time-of-arrival measurement and said second time-of-arrival measurement; and

measurement;

choosing an estimated location for said wireless terminal based on said second list of locations and said signal strength measurement.

4. A method comprising:

receiving

(i) a signal strength measurement for a first signal as received by a wireless terminal,

(ii) a first time-of-arrival measurement for a second signal as received by said wireless terminal, wherein said second signal is transmitted by a first Earth satellite, and

(iii) a second time-of-arrival measurement for a third signal as received by said wireless terminal, wherein said third signal is transmitted by a second Earth satellite,

matching said signal strength measurement against a database that associates locations with signal measurements to generate a first multi-dimensional probability distribution for the location of said wireless terminal;

generating a second probability distribution for the location of said wireless terminal based on said first time-of-arrival measurement and said second time-of-arrival measurement; and

estimating the location of said wireless terminal based on;

(i) said first multi-dimensional probability distribution, and

(ii) said second multi-dimensional probability distribution;

wherein estimating the location of said wireless terminal comprises;

pruning a first list of candidate locations of said wireless terminal to a second list of candidate locations of said wireless terminal based on said signal strength measurement; and

choosing an estimated location of said wireless terminal based on said second list of locations, said first time-of-arrival measurement, and said second time-of-arrival measurement.