Estimating the location of a wireless terminal based on signal path impairment

• US 8,571,577 B2
• Filed: 07/18/2012
• Issued: 10/29/2013
• Est. Priority Date: 09/22/1998
• Status: Expired due to Term

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: Polaris Wireless Incorporated
• Inventors: Bhattacharya, Tarun Kumar, Feuerstein, Martin, Gordon, Scot Douglas, Spain, David Stevenson Jr.
• Primary Examiner(s): Doan, Kiet
• Assistant Examiner(s): Vu, Michael T
• Application Number:
  US13/551,893
• Publication Number:
  US 20120282947A1
• Time in Patent Office: 468 Days
• Field of Search: 455 332- 334, 455/404, 455/456, 455/423, 455/450, 4554561-457
• US Class Current: 455/456.1
• 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:

(1) receiving, at a location server;

(i) a first measured error rate for a first signal that is received by a wireless terminal, and

(ii) a second measured error rate for a second signal that is received by the wireless terminal; and

(2) estimating, at the location server, a first location of the wireless terminal based on the first measured error rate and the second measured error rate;

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

wherein (2) the estimating the first location of the wireless terminal comprises;

(2.1) comparing the first measured error rate to;

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

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

(2.2) comparing the second measured error rate to;

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

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

2. A method comprising:

(1) receiving, at a location server;

(1.i) a first measured error rate for a signal that is received by a wireless terminal, wherein the first measured error rate is measured at a first time T₁, and

(1.ii) a second measured error rate for the signal that is received by the wireless terminal, wherein the second measured error rate is measured at a second time T₂, and

wherein the first time does not equal the second time; and

(2) estimating a first location of the wireless terminal at the second time T₂ based on;

(2.i) the first measured error rate,

(2.ii) the second measured error rate, and

(2.iii) an estimate of the probability that the wireless terminal at a second location at the first time T₁ will still be at the second location at the second time T₂;

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

3. A location server comprising:

a transceiver for receiving;

(i) a first measured error rate for a first signal that is received by a wireless terminal, and

(ii) a second measured error rate for a second signal that is received by the wireless terminal;

a memory, which is non-volatile, for storing application software; and

a processor for executing the application software to estimate a first location of the wireless terminal based on the first measured error rate and the second measured error rate;

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

wherein to estimate the first location of the wireless terminal, the processor is further for;

(A) comparing the first measured error rate to;

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

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

(B) comparing the second measured error rate to;

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

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

4. A location server comprising:

a transceiver for receiving;

(1.i) a first measured error rate for a signal that is received by a wireless terminal, wherein the first measured error rate is measured at a first time T₁, and

(1.ii) a second measured error rate for the signal that is received by the wireless terminal, wherein the second measured error rate is measured at a second time T₂, and

wherein the first time does not equal the second time T₂;

a memory, which is non-volatile, for storing application software; and

a processor for executing the application software to estimate a first location of the wireless terminal at the second time T₂ based on;

(2.i) the first measured error rate,

(2.ii) the second measured error rate, and

(2.iii) an estimate of the probability that the wireless terminal at a second location at the first time T₁ will still be at the second location at the second time T₂;

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