Local positioning system

• US 6,748,224 B1
• Filed: 12/16/1998
• Issued: 06/08/2004
• Est. Priority Date: 12/16/1998
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Palamara, Maria E., Varvaro, Charles, Chen, Byron H.
• Primary Examiner(s): Appiah, Charles
• Assistant Examiner(s): MOORE, JAMES K
• Application Number:
  US09/212,261
• Time in Patent Office: 2,001 Days
• Field of Search: 455/456, 455/457, 455/456--45, 342/450, 342/451, 342/457, 342/387, 342/458
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A local positioning system (LPS) uses the radio propagation parameters in a CDMA forward link or TDMA reverse link to establish a mobile station'"'"'s position. The mobile station receives pilot channel signals from at least three distinct base stations and records the PN chip offset of the pilot channel signals. The LPS time difference of arrival triangulation approach requires no additional signal detection capabilities. Base stations send out pilot channel signals that arrive at a mobile station with a particular phase and at least a predetermined minimum strength. The mobile station reports back the “visible” pilot channel signals, their phases and signal strength to the LPS which uses a location non-linear system, expressed as a set of cost functions, to estimate the mobile location. The LPS can also solve the 9-1-1 mobile location problem for wireless CDMA systems by determining the position of a person in distress that has a digital cellular phone.

Claims

1. A method for determining the position of a mobile station, comprising the steps of:

(a) receiving pilot channel signal information indicating arrival times of pilot channel signals at the mobile station;

[b] estimating a distance from the mobile station to one of a plurality of base stations by minimizing a set of distance error cost functions including angles formed by the base stations and the mobile station; and

[c] estimating the location of the mobile station by minimizing a set of position error cost functions based on the pilot channel signal information and on base station information indicating the location of the plurality of base stations to which the arrival time information is associated.

2. The method of claim 1, wherein the position error cost functions are derived from the equations:

3. The method of claim 2, wherein

d₂=d₁+800.4(p₂)ft, where p₂ is a phase difference between the pilot channel signal phase recordings of the first and second base stations, and

d₃=d₁+800.4(p₃)ft, where p₃ is a phase difference between the pilot channel signal phase recordings of the first and third base stations.

4. The method of claim 1, prior to step [c], further comprising the steps of:

[d] receiving the base station information indicating the location of the plurality of base stations; and

[e] matching the pilot channel signal information to the base station information based on a source identifier common to both the pilot channel signal information and the base station information.

5. The method of claim 1, wherein the arrival times correspond to synchronized timing of the base stations.

6. The method of claim 1, wherein the distance error cost functions are derived from the equations:

7. The method of claim 1, wherein the pilot channel signal information includes at least one of a source identifier, a pilot channel signal phase and a pilot strength.

8. The method of claim 7, wherein the base station information includes at least one of the source identifier and base station location.

9. The method of claim 1, further comprising the step of averaging the estimation of the mobile station location with a previous estimation of the mobile station to acquire a mean estimation of mobile station location.

10. The method of claim 1, wherein the pilot channel signal information is included in a CDMA signal.

11. The method of claim 1, wherein the pilot channel signal information is included in a TDMA signal.

12. A local positioning system implemented on a computer for determining the position of a mobile station, comprising:

means for receiving pilot channel signal information indicating arrival times of pilot channel signals at the mobile station;

means for estimating a distance from the mobile station to one of a plurality of base stations by minimizing a set of distance error cost functions including angles formed by the base stations and the mobile station; and

means for estimating the location of the mobile station by minimizing a set of position error cost functions based on the pilot channel signal information and on base station information indicating the location of the plurality of base stations to which the arrival time information is associated.

13. The local positioning system of claim 12, wherein the position error cost functions are derived from the equations:

14. The local positioning system of claim 13, wherein

d₂=d₁+800.4(p₂)ft, where p₂ is a phase difference between the pilot channel signal phase recordings of the first and second base stations, and

d₃=d₁+800.4(p₃)ft, where p₃ is a phase difference between the pilot channel signal phase recordings of the first and third base stations.

15. The local positioning system of claim 12, further comprising:

means for receiving the base station information indicating the location of the plurality of base stations; and

means for matching the pilot channel signal information to the base station information based on a source identifier common to both the pilot channel signal information and the base station information.

16. The local positioning system of claim 12, wherein the arrival times correspond to synchronized timing of the base stations.

17. The local positioning system of claim 12, wherein the distance error cost functions are derived from the equations:

18. The local positioning system of claim 12, wherein the pilot channel signal information includes at least one of a source identifier, a pilot channel signal phase and a pilot strength.

19. The local positioning system of claim 18, wherein the base station information includes at least one of the source identifier and base station location.

20. The local positioning system of claim 12, further comprising means for averaging th e estimation of the mobile station location with a previous estimation of the mobile station to acquire a mean estimation of mobile station location.

21. The local positioning system of claim 12, wherein the pilot channel signal information is included in a CDMA signal.

22. The local positioning system of claim 12, wherein the pilot channel signal information is included in a TDMA signal.

23. An executable program embodied on a computer-readable medium for determining the position of a mobile station comprising:

a receiving source code segment for receiving pilot channel signal information indicating arrival times of pilot channel signals at the mobile station;

a computing source code segment for estimating a distance from the mobile station to one of a plurality of base stations by minimizing a set of distance error cost functions including angles formed by the base stations and the mobile station; and

an estimating source code segment for estimating the location of the mobile station by minimizing a set of position error cost functions based on the pilot channel signal information and on base station information indicating the location of a the plurality of base stations to which the arrival time information is associated.

24. A computer data signal comprising:

a receiving signal segment for receiving pilot channel signal information indicating arrival times of pilot channel signals at the mobile station;

a computing signal segment for estimating a distance from the mobile station to one of a plurality of base stations by minimizing a set of distance error cost functions including angles formed by the base stations and the mobile station; and

an estimating signal segment for estimating the location of the mobile station by minimizing a set of position error cost functions based on the pilot channel signal information and on base station information indicating the location of the plurality of base stations to which the arrival time information is associated.

25. The computer data signal of claim 24, wherein the computer data signal is embodied on a carrier wave.