Location and tracking system

• US 6,275,705 B1
• Filed: 11/27/1998
• Issued: 08/14/2001
• Est. Priority Date: 12/22/1995
• Status: Expired due to Term

• Current Assignee: Cambridge Positioning Systems Limited (Qualcomm, Inc.)
• Original Assignee: Cambridge Positioning Systems Limited (Qualcomm, Inc.)
• Inventors: Drane, Christopher R., MacNaughtan, Malcolm D., Scott, Craig A.
• Primary Examiner(s): Nguyen, Lee
• Application Number:
  US09/091,728
• Time in Patent Office: 991 Days
• Field of Search: 455/456, 455/65, 342/372, 342/457, 342/107, 342/357.08, 342/450, 342/417, 342/429, 342/432, 342/446
• US Class Current: 455/456.2
• 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 techniques involving comparison of the times of arrival of signals from the base stations at the mobile transceiver;

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

2. 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 form 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 techniques involving comparison of the times of arrival of signals from the base stations at the mobile transceiver;

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

3. 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 techniques involving comparison of the times of arrival of signals from the base stations at the mobile transceiver;

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

4. 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;

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

5. 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;

said method comprising the additional step of synthesizing a wide aperture while the mobile transceiver is moving to provide additional information for position calculation.

6. 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;

said method comprising the additional step of synthesizing a wide aperture while the mobile transceiver is moving to provide additional information to reduce multi-path effects.