US 5,327,144 AGranted

Cellular telephone location system

AssigneeAssociated RT, Inc.

InventorsLouise A. Stilp, Curtis A. Knight, John C. Webber

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Abstract

A cellular telephone location system for automatically recording the location of one or more mobile cellular telephones comprises three or more cell site systems 12. Each cell site system is located at a cell site of a cellular telephone system. Each cell site system includes an antenna that may be mounted on the same tower or building as the antenna employed by the cellular telephone system and equipment that may be housed in the equipment enclosure of the corresponding cell site. The cell site systems are coupled via T1 communication links 14 to a central site 16. The central site may be collocated with the cellular telephone system's MTSO. The central site 16 is further coupled to a database 20, which may be remotely located from the central site and made available to subscribers.

Claims45

Dependent claims

A cellular telephone location system for determining the locations of multiple mobile cellular telephones each initiating periodic signal transmission over one of a prescribed set of reverse control channels, comprising:

(a) at least three cell site systems, each cell site system comprising:
an elevated ground-based antenna;
a baseband convertor operatively coupled to said antenna for receiving cellular telephone signals transmitted over a reverse control channel by said cellular telephones and providing baseband signals derived from the cellular telephone signals;
a timing signal receiver for receiving a timing signal common to all cell sites;
and a sampling subsystem operatively coupled to said timing signal receiver and said baseband convertor for sampling said baseband signal at a prescribed sampling frequency and formatting the sample signal into frames of digital data, each frame comprising a prescribed number of data bits and time stamp bits, said time stamp bits representing the time at which said cellular telephone signals were received;
and
(b) a central site system operatively coupled to said cell site systems, comprising:
means for processing said frames of data from said cell site systems to generate a table identifying individual cellular telephone signals and the differences in times of arrival of said cellular telephone signals among said cell site systems;
and means for determining, on the basis of said times of arrival differences, the locations of the cellular telephones responsible for said cellular telephone signals.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/059,248Filed 7 May 1993
Granted: 5 Jul 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H04W 64/00
Locating users or terminals or network equipment for network management purposes
G01S 3/46
Systems for determining direction or deviation from predetermined direction: using antennas spaced apart and measuring phase or time difference…
G01S 5/06
Using radio waves: position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements
G01S 1/026
Means for monitoring or calibrating: of associated receivers