Network-based wireless location system to position AMPs (FDMA) cellular telephones, part I

• US 6,330,452 B1
• Filed: 08/06/1998
• Issued: 12/11/2001
• Est. Priority Date: 08/06/1998
• Status: Expired due to Term

• Current Assignee: CELL-LOC LOCATION TECHNOLOGIES INC.
• Original Assignee: Cell-Loc Inc. (Pembina Pipeline Corp.)
• Inventors: Borsodi, Andrew, Fattouche, Michel, Klukas, Richard
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Perez-Gutierrez, Rafael
• Application Number:
  US09/130,637
• Time in Patent Office: 1,223 Days
• Field of Search: 455/456, 455/507, 455/524, 455/526, 455/440, 455/67.1, 455/67.6, 342/387, 342/457
• US Class Current: 455/456.1
• CPC Class Codes: G01S 1/045 Receivers
• CPC Class Codes: G01S 11/10 using Doppler effect
• CPC Class Codes: G01S 5/02213 Receivers arranged in a network for determining the position of a transmitter
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The intention of the invention is to produce a network-based Wireless Location System (WLS) whereby existing Advanced Mobile Phone System (AMPS) Frequency Division Multiple Access (FDMA) Cellular Telephones (CTs) can be located passively without modification to the CTs or to the cellular antenna infrastructure. More specifically, the invention consists of methods and apparatus to estimate the position and velocity of a Cellular Telephone (CT) using either the Time Of Arrival (TOA) of a signal transmitted by the CT, its Phase Of Arrival (POA), its Frequency Of Arrival (FOA), or a combination thereof, at several antennas at a number of Monitoring Sites (MSs). In order to solve for the coordinates of the CT, the patent uses either hyperbolic multilateration based on Time Difference Of Arrival (TDOA), or linear multiangulation based on Phase Difference Of Arrival (PDOA), or both. In order to solve for the velocity of the CT, the patent uses FOA based on Frequency Difference Of Arrival (FDOA). An important contribution of this invention is the way the CT is forced to transmit radio signals for location purposes. Another important contribution is the application of Super-Resolution (SR) techniques to increase the resolution of the estimated TOAs, POAs or FOAs.

Claims

1. A method of estimating the location of a cellular telephone that is initiating a call, the method comprising the steps of:

monitoring the initiation of the call over a reverse control channel using a first monitoring site;

monitoring a reverse voice channel assignment over the corresponding forward control channel using the first monitoring site;

notifying a plurality of monitoring sites to monitor the signal s(t) generated by the cellular telephone over the assigned reverse voice channel during an observation time T which coincides with the cellular telephone being in either answered conversation mode or unanswered conversation mode;

processing the signal s(t) by each one of the plurality of monitoring sites by estimating the phase of one of a SAT tone resolved using superresolution algorithms and a tone derived from the pitch of the signal s(t) and resolved using superresolution algorithms;

estimating the location of the cellular telephone from the estimated phase to generate a location estimate; and

transferring the location estimate to a user during unanswered conversation mode.

2. A method of estimating the location of a cellular telephone that is initiating a call, the method comprising the steps of:

monitoring the initiation of the call over a reverse control channel using a first monitoring site;

monitoring a reverse voice channel assignment over the corresponding forward control channel using the first monitoring site;

notifying a plurality of monitoring sites to monitor the signal s(t) generated by the cellular telephone over the assigned reverse voice channel during an observation time T which coincides with the cellular telephone being in answered conversation;

processing the signal s(t) received by each one of the plurality of monitoring sites by estimating the phase of a SAT tone resolved using superresolution algorithms only over quiet periods of time where no speech is uttered; and

estimating the location of the cellular telephone from the estimated phase to generate a location estimate.

3. A method of estimating the location of a cellular telephone that is initiating a call, the method comprising the steps of

monitoring the initiation of the call over a reverse control channel using a monitoring site;

monitoring a reverse voice channel assignment over the corresponding forward control channel using the same monitoring site; and

notifying a plurality of monitoring sites to monitor and process a signal s(t) generated by the cellular telephone over the assigned reverse voice channel during an observation time T which coincides with the cellular telephone being in unanswered conversation mode; and

estimating the location of the cellular telephone from the signal s(t) to obtain a location estimate.

4. The method of claim 3 further comprising:

taking a plurality of samples of the signal s(t) during a plurality of observation intervals while the cellular telephone is in unanswered conversation mode; and

averaging the location estimate over the plurality of samples.

5. A method of estimating the location of a powered-up cellular telephone, the method comprising the steps of

calling the cellular telephone by paging the cellular telephone;

monitoring the paging of the cellular telephone over a forward control channel using a monitoring site;

acquiring and processing the response s(t) of the cellular telephone to the page over the corresponding reverse voice channel at each one of a plurality of monitoring sites;

performing a nonlinear operation on the received signal s(t) at each one of the monitoring sites to generate at least one tone;

dropping the call; and

estimating the location of the cellular telephone from the tone generated by performing the nonlinear operation on the received signal.

6. The method of claim 5 further comprising the steps of:

FM demodulating the received signal s(t) at each one of the monitoring sites before performing a non-linear operation on the received signal s(t); and

performing a nonlinear operation comprises performing the nonlinear operation on the FM demodulated signal at each one of the monitoring sites.

7. The method of claim 5 wherein the nonlinear operation is selected from the group consisting of:

a quadratic operation;

a delay product operation; and

an absolute value operation.

8. The method of claim 5 further comprising the step of

notifying a plurality of monitoring sites to anticipate the response s(t) of the cellular telephone over a specified reverse control channel.

9. The method of claim 5 wherein estimating the location of the cellular telephone is based upon the phases of the generatid at least one tone.

10. The method of claim 9 wherein the generated at least one tone is resolved using superresolution algorithms.

11. The method of claim 5 wherein the call is dropped before the cellular telephone is allowed to utter an alert signal.

12. The method of claim 11 wherein the step of estimating the location of the cellular telephone is achieved by a step selected from the group consisting of:

estimating the time of arrival of the signal s(t) at some of the plurality of monitoring sites,

estimating the angle of arrival of the signal s(t) at some pairs of the plurality of monitoring sites, and

estimating both the time of arrival and the angle of arrival of the signal s(t) at some of the plurality of monitoring sites.

13. The method of claim 12 wherein the step of estimating the angle of arrival of the cellular telephone at some pairs of the plurality of monitoring sites is achieved by co-locating the monitoring sites within a plurality of base stations and estimating the angle of arrival between pairs of cellular diversity antennas at the base stations or pairs of cellular sector antennas at the base stations.

14. The method of claim 11 further comprising:

repeating the steps in claim 5 a plurality of times to generate location estimates; and

averaging the location estimates over the plurality of times.

15. The method of claim 11 wherein the monitoring sites are co-located within a plurality of base stations.

16. The method of claim 15 wherein only one RF front end is used per antenna at each base station.

17. The method of claim 5 wherein the signal s(t) is filtered prior to performing the nonlinear operation.