Method for improving the accuracy of a wireless location system

• US 6,097,336 A
• Filed: 01/12/1999
• Issued: 08/01/2000
• Est. Priority Date: 01/08/1999
• Status: Expired due to Term

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: TruePosition Incorporated
• Inventors: Stilp, Louis A.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/229,056
• Time in Patent Office: 567 Days
• Field of Search: 342/457, 342/464, 342/357.01, 342/357.02
• US Class Current: 342/357.395
• CPC Class Codes: G01S 1/026 of associated receivers
• CPC Class Codes: G01S 2205/006 for emergency situations
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 2205/06 Emergency
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/02216 Timing or synchronisation of the receivers
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0246 involving frequency difference of arrival or Doppler measurements G01S5/02685 takes precedence
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: G01S 5/0268 by deriving positions from different combinations of signals or of estimated positions in a single positioning system
• CPC Class Codes: G01S 5/0284 Relative positioning
• 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: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 76/50 for emergency connections
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method for locating a mobile transmitter comprises the steps of (a) making a first estimate of the location of the mobile transmitter on the basis of a first transmission from the mobile transmitter; (b) causing the mobile transmitter to emit a second transmission; (c) making a second estimate of the location of the mobile transmitter on the basis of the second transmission; and (d) combining at least the first and second estimates to obtain an improved, more accurate estimate of the location of the mobile transmitter. Step (b) may comprise auditing the mobile transmitter to elicit an audit response, or terminating the call (hanging up) and then initiating another call by paging the mobile transmitter to elicit a page response. Step (d) preferably comprises averaging a plurality of statistically-independent location estimates.

Claims

1. A method for use in a Wireless Location System in locating a mobile transmitter, comprising the steps of:

(a) making a first estimate of the location of said mobile transmitter, said first estimate being made on the basis of a first reverse transmission from the mobile transmitter;

(b) causing the mobile transmitter to emit a second transmission;

(c) making a second estimate of the location of the mobile transmitter; and

(d) combining at least said first and second estimates to obtain an improved, more accurate estimate of the location of the mobile transmitter.

2. A method as recited in claim 1, wherein step (b) comprises auditing the mobile transmitter.

3. A method as recited in claim 1, wherein step (b) comprises terminating the call with the mobile transmitter, and then initiating another call by paging the mobile transmitter.

4. A method as recited in claim 1, wherein step (d) comprises averaging a plurality of statistically-independent location estimates.

5. A method for locating a mobile transmitter, comprising the step of averaging a plurality of statistically-independent location estimates to obtain an improved, more accurate estimate of the location of the mobile transmitter, wherein at least one of said plurality of statistically-independent location estimates is obtained by causing the mobile transmitter to emit a responsive signal of a predetermined type.

6. A method as recited in claim 5, wherein said responsive signal comprises an audit response.

7. A method as recited in claim 5, wherein said responsive signal comprises a page response.

8. A method for locating a mobile transmitter, comprising the steps of:

(a) making a first estimate of the location of said mobile transmitter, said first estimate being made on the basis of a first reverse transmission from the mobile transmitter;

(b) auditing the mobile transmitter to thereby cause it to emit an audit response signal;

(c) making a second estimate of the location of the mobile transmitter on the basis of said audit response signal, said second estimate being statistically-independent of said first estimate; and

(d) averaging at least the first and second, statistically-independent location estimates to obtain a third location estimate which is more accurate than said first or second estimates.

9. A method for use in a Wireless Location System for locating a mobile transmitter, comprising:

making a first estimate of the mobile transmitter'"'"'s location based upon first reverse channel transmissions from the mobile transmitter;

monitoring the mobile transmitter for a second transmission;

making a second location estimate based on the second transmission; and

combining the first and second estimates to obtain an improved estimate of the mobile transmitter'"'"'s location.

10. A method as recited in claim 9, wherein the Wireless Location System causes the mobile transmitter to make the second transmission.

11. A method as recited in claim 10, wherein the mobile transmitter is audited to elicit the second transmission.

12. A method as recited in claim 10, comprising terminating the call with the mobile transmitter and then initiating another call by paging the mobile transmitter, whereby the second transmission is elicited.

13. A method as recited in claim 9, comprising averaging a plurality of statistically independent location estimates.

14. A method of locating a mobile transmitter, comprising averaging a plurality of statistically independent location estimates to obtain an improved estimate, wherein at least one estimate is obtained by causing the mobile transmitter to transmit a predetermined response signal.

15. A method as recited in claim 14, wherein the response signal comprises an audit response.

16. A method as recited in claim 14, wherein the response signal comprises a page response.

17. A method for locating a mobile transmitter, comprising making a first location estimate based upon a first reverse transmission, auditing the mobile transmitter to cause it to emit an audit response, making a second location estimate based upon the audit response, and averaging the first and second estimates to obtain a third estimate.