Method and apparatus for determining location of a subscriber device in a wireless cellular communications system

• US 5,815,538 A
• Filed: 01/11/1996
• Issued: 09/29/1998
• Est. Priority Date: 06/25/1993
• Status: Expired due to Fees

• Current Assignee: Westar Capital LLC
• Original Assignee: Omniplex Incorporated
• Inventors: Bennett, Chris, Theiss-Aird, Michael, Rothmuller, Ilan J., Grell, Conrad, Guralnick, Jeremy
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Nguyen, Madeleine Au
• Application Number:
  US08/585,261
• Time in Patent Office: 992 Days
• Field of Search: 342/357, 342/356, 342/387, 342/358, 342/413, 342/450, 342/458, 364/460, 364/449.1, 379/58, 379/59, 455/32.1, 455/456, 455/457, 375/364, 375/356
• US Class Current: 375/356
• 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: 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 location of a subscriber device in a wireless cellular communications system is established by transmitting digital data signals to a cellular digital data receiver of the subscriber device from at least three different cellular cell site transmitters at known locations. Each data signal has a time-synchronized synchronization signal, preferably synchronized through the time signals of the global positioning system. The time of arrival of each of the time-synchronized synchronization signals is determined with respect to an internal clock of the receiver. The location of the subscriber device is established from the locations of the cell sites and the times of arrival of the synchronization signals relative to the internal clock.

Claims

1. A method for determining a location of a subscriber device in a wireless cellular communications system, comprising the steps of:

providing a subscriber device having a cellular digital data receiver system with a cellular digital data receiver therein;

transmitting cellular digital data signals to the subscriber device from at least three different cellular cell site transmitters at different but known locations, each data signal containing a time-synchronized synchronization signal, the time-synchronized synchronization signals of the at least three different cellular cell site transmitters being transmitted at the same time or being displaced in time from each other by a known time displacement;

informing the subscriber device of location data representing a location of each of the at least three cellular cell site transmitters;

determining a time of arrival of each of the time-synchronized synchronization signals with respect to an internal clock of the cellular digital data receiver system; and

obtaining the location of the subscriber device from the location data and the times of arrival of the time-synchronized synchronization signals relative to the internal clock.

2. The method of claim 1, wherein the step of transmitting includes the step of

synchronizing the time-synchronized synchronization signals to a timing signal provided by a global positioning system.

3. The method of claim 1, wherein the step of informing includes the step of

incorporating into the cellular digital data signal transmitted from at least one cell site the location data representing the location of each of the at least three cell site transmitters.

4. The method of claim 1, wherein the step of determining includes the steps of

aligning the internal clock of the cellular digital data receiver system to a first one of the time-synchronized synchronization signals transmitted at a first time, and

establishing the arrival times of a second and a third later-transmitted time-synchronized synchronization signals of respective second and third cell site transmitters relative to the aligned internal clock.

5. The method of claim 1, wherein the step of obtaining is performed by the cellular digital data receiver.

6. The method of claim 1, including the additional step of

transmitting the relative time of arrival of each of the time-synchronized synchronization signals to a remote location, and wherein the step of obtaining is performed at the remote location.

7. The method of claim 1, wherein the step of transmitting includes the step of

providing time-synchronized synchronized signals having no intentionally introduced time displacements therein.

8. The method of claim 1, including the additional step of

time displacing at least one of the time-synchronized synchronization signals by a preestablished amount, and

providing the preestablished amount of the time displacing to the step of obtaining, so that the preestablished amount of time displacement may be accounted for in the obtaining of the relative location of the subscriber device.

9. The process of claim 1, wherein the step of providing a subscriber device includes the step of

providing a cellular digital data receiver operable with a Cellular Digital Packet Data format.

10. Apparatus for determining a location of a subscriber device in a wireless cellular communications system, comprising:

at least three cellular cell site transmitters, each of the cellular cell site transmitters including

means for providing a timing signal synchronized to a common time standard, the common time standard being a time standard that is the same for each of the cellular cell site transmitters, and

means for transmitting a cellular digital data signal having a time-synchronized synchronization signal synchronized to the timing signal;

a subscriber device having

a cellular digital data receiver operable to receive the cellular digital data signal transmitted by the cellular cell site transmitters,

means for determining a time of arrival of each of the time-synchronized synchronization signals relative to the internal clock;

means for determining the location of the cellular cell site transmitters; and

means for obtaining the location of the subscriber device from the locations of the cellular cell site transmitters and the time of arrival of the time-synchronized synchronization signal at each of the at least three cellular cell site transmitters relative to the internal clock.

11. The apparatus of claim 10, wherein the means for providing a timing signal includes

a global positioning system receiver.

12. The apparatus of claim 10, wherein the cellular digital data signal includes information defining the location of the cell site transmitters and the means for determining the location of the cell site transmitters includes

means for decoding the data signals to obtain the information defining the location of the cell site transmitters.

13. The apparatus of claim 10, wherein the means for determining the time of arrival includes

means for aligning the internal clock to a first one of the time-synchronized synchronization signals received at a first time, and

establishing the arrival times of a second and a third later-received time-synchronized synchronization signals of respective second and third cellular cell site transmitters relative to the aligned internal clock.

14. The apparatus of claim 10, wherein the means for obtaining is located within the subscriber device.

15. The apparatus of claim 10, further including

means for providing the location of the subscriber device to an external device.

16. The apparatus of claim 10, further including

means for transmitting the relative time of arrival of each of the synchronized time-synchronized synchronization signals to a remote location, and wherein the means for obtaining is located at least in part at the remote location.

17. The apparatus of claim 10, wherein the means for transmitting includes

means for providing time-synchronized synchronized signals having no intentionally introduced time displacements therein.

18. The apparatus of claim 10, wherein the means for transmitting further includes

means for introducing a time displacement into at least one of the time-synchronized synchronization signals by a preestablished amount upon transmittal, and

means for providing the preestablished amount of the time displacement to the means for obtaining, so that the time displacement may be accounted for in the obtaining of the location of the subscriber device relative to the locations of the cellular cell site transmitters.

19. The apparatus of claim 10, wherein the cellular digital data receiver is operable with a Cellular Digital Packet Data format.

20. Apparatus for determining a location of a subscriber device in a wireless cellular communications system, the apparatus comprising the subscriber device having

a cellular digital data receiver operable to receive cellular digital data signals transmitted by at least three cellular cell site transmitters, each of the cellular digital data signals including a time-synchronized synchronization signal synchronized to a common time standard, the common time standard being a time standard that is the same for each of the cellular cell site transmitters,;

an internal clock;

means for determining a time of arrival of each of the time-synchronized synchronization signals relative to the internal clock; and

means for obtaining the location of the subscriber device relative to the at least three cellular cell site transmitters from the times of arrival of the time-synchronized synchronization signals relative to the internal clock.

21. The apparatus of claim 20, wherein the cellular digital data receiver includes

a radio frequency receiver operable to receive cellular transmissions,

a filter that eliminates noise from the received cellular transmissions, and

a discriminator that produces a hard limited signal from the filtered cellular transmissions.

22. The apparatus of claim 20, wherein the means for determining the time of arrival includes

means for aligning the internal clock with a correlation feature of a first one of the time-synchronized synchronization signals received by the cellular digital data receiver from a first cellular cell site transmitter, and

means for establishing the time increment of receipt of the correlation feature of each of the time-synchronized synchronization signals received from a second and a third cellular cell site transmitter relative to the aligned internal clock, thereby establishing the relative time of receipt of the time-synchronized synchronization signals of the digital data signals relative to the common time standard.

23. The apparatus of claim 22, wherein the correlation feature is a common bit in each of the time-synchronized synchronization signals, and wherein the means for establishing includes

means for dividing the bits of each of the second and third time-synchronized synchronization signals into fractional time increments and for establishing a fractional bit interval displacement for each of the common bits.

24. The apparatus of claim 23 wherein the correlation feature is a leading edge of the common bit in each of the time-synchronized synchronization signals.