Location and tracking system

• US 20010004601A1
• Filed: 02/02/2001
• Published: 06/21/2001
• Est. Priority Date: 12/22/1995
• Status: Active Grant

• Current Assignee: Christopher R. Drane, Craig A. Scott, Malcolm D. Macnaughtan
• Original Assignee: Christopher R. Drane, Craig A. Scott, Malcolm D. Macnaughtan
• Inventors: Drane, Christopher R., MacNaughtan, Malcolm D., Scott, Craig A.
• Granted Patent: US 6,522,890 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 1/024 of beacon transmitters
• 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

The invention concerns a method of finding the position of a mobile radio-frequency transceiver in a communications system. A network of at least two unsynchronized base stations arranged to transmit/receive signals to at least one mobile-radio frequency transceiver; a reference receiver located at a known distance from the base stations and including measuring means to measure the times of arrival of signals transmitted from the base stations; determination means to use the known distances and measured times to determine the relative time offsets of transmissions from each base station; and location means to use the determined relative time offsets to calculate the position of a mobile transceiver in the network area using hyperbolic positioning techniques. A number of other enhancements to positioning systems relating to the usage of Doppler, carrier information, direction of arrival to improve the performance of mobile telephone-based positioning systems are also described.

Claims

1. A mobile radio-frequency communication system, comprising:

a network of at least two base stations arranged to transmit the same signals to at least one mobile radio-frequency transceiver, and receive signals from the one or more mobile radio-frequency transceivers;

a reference receiver located at a fixed location a known distance from each of the base stations and including measuring means to measure the times of arrival of signals transmitted from the base stations;

determination means to use the known distances and measured times to determine the relative time offsets of transmissions from each base station; and

location means to use the determined relative time offsets to calculate the position of a mobile transceiver in the network area using hyperbolic positioning techniques involving comparison of the times of arrival of signals from the base stations at the mobile transceiver.

2. A mobile radio-frequency communication system according to

claim 1

, wherein the determination means is situated within the reference receiver.

3. A mobile radio-frequency communication system according to

claim 1

, wherein the location means is situated within the mobile transceiver.

4. A mobile radio-frequency communication system according to

claim 1

, wherein the location means is associated with a base station.

5. A mobile radio-frequency communication system according to

claim 1

, wherein the location means receives information from the reference receiver by means of a landline.

6. A mobile radio-frequency communication system according to

claim 1

, wherein the location means also receives data concerning at least one of base station oscillator stability, base station location or the phase difference between two signals having different frequencies that have been transmitted by the same base station, by means of the landline.

7. A mobile radio-frequency communication system according to

claim 1

, wherein a selector means is operationally associated with the determination means to selectively prevent information concerning the position of a mobile transceiver from being available to that transceiver.

8. A mobile radio-frequency communication system according to

claim 1

, wherein each base station is arranged to transmit signals at several different frequencies to at least one mobile radio-frequency transceiver, and the mobile transceiver calculates the phase difference between the signals having different frequencies that have been transmitted from the same base station in order to calculate its position.

9. A mobile radio-frequency communication system according to

claim 1

, wherein the mobile transceiver calculates the impulse response of the channel and uses this information to reduce multi-path effects.

10. A mobile radio-frequency communication system according to

claim 1

, wherein the mobile transceiver synthesises a wide aperture while it is moving to provide additional information for position calculation.

11. A mobile radio-frequency communication system according to

claim 1

, wherein the mobile transceiver synthesises a wide aperture while it is moving to provide additional information to reduce multi-path effects.

12. A mobile radio-frequency communication system according to

claim 1

, wherein a directional antenna is used for position ambiguity resolution, position determination or to reduce multi-path effects.

13. A mobile radio-frequency communication system according to

claim 1

, wherein Doppler estimates of the velocity of mobile transceivers are used to calculate the velocity of the vehicle and use this information to enhance position estimates of the mobile radio-frequency transceiver.

14. A mobile radio-frequency communication system according to

claim 1

, wherein information such as map data, dead reckoning, communications broadcasts are used to improve mobile transceiver position estimates.

15. A method of finding the position of a mobile radio-frequency transceiver in a communication system comprising a network of at least two base stations arranged to transmit the same signals, comprising the steps of:

locating a reference receiver at known distances from the base stations;

measuring the times of arrival at the reference receiver of signals transmitted from the base stations;

determining the relative time offsets of transmissions from each base station, using the known distances and measured times; and

calculating the position of a mobile transceiver in the network area using the determined relative time offsets and hyperbolic positioning techniques.

16. A method according to

claim 15

, comprising the further step of selectively preventing information concerning the position of a mobile transceiver from being available to that transceiver.

17. A method according to

claim 15

, comprising the further steps of:

transmitting signals from the base stations at several different frequencies; and

calculating the phase difference between the different signals having different frequencies that have been transmitted from the same base station in order to calculate its position.

18. A method according to

claim 15

, comprising the additional step of:

calculating the impulse response of the channel between a base station and a mobile and using this information in the mobile transceiver to reduce multi-path effects.

19. A method according to

claim 15

, comprising the additional step of:

synthesising a wide aperture while the mobile transceiver is moving to provide additional information for position calculation.

20. A method according to

claim 15

, comprising the additional step of:

synthesising a wide aperture while the mobile transceiver is moving to provide additional information to reduce multi-path effects.

21. A method according to

claim 15

, comprising the additional step of:

using a directional antenna, either at base station or on a mobile transceiver, for position ambiguity resolution, position determination or to reduce multi-path effects.

22. A method according to

claim 15

, comprising the additional step of:

using Doppler estimates of the velocity of mobile transceivers to calculate the position or location of the mobile transceiver.

23. A method according to

claim 15

, comprising the additional step of:

using information such as map data, dead reckoning, communications broadcasts to improve mobile transceiver position estimates.