Cellular telephone location system
DCFirst Claim
1. 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.
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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.
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Citations
45 Claims
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1. 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:
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(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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A ground-based cellular telephone system serving a plurality of subscribers possessing mobile cellular telephones, comprising:
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(a) at least three cell sites equipped to receive signals sent by multiple mobile cellular telephones each initiating periodic signal transmissions over one of a prescribed set of reverse control channels; (b) locating means for automatically determining the locations of said cellular telephones by receiving and processing signals emitted during said periodic reverse control channel transmissions; and (c) database means for storing location data identifying the cellular telephones and their respective locations, and for providing access to said database to subscribers at remote locations. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30)
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31. A method for determining the location(s) of one or more mobile cellular telephones periodically transmitting signals over one of a prescribed set of reverse control channels, comprising the steps of:
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(a) receiving said reverse control channel signals at at least three geographically-separated cell sites; (b) processing said signals at each cell site to produce frames of data, each frame comprising a prescribed number of data bits and time stamp bits, said time stamp bits representing the time at which said frames were produced at each cell site; (c) processing said frames of data to identify individual cellular telephone signals and the differences in times of arrival of said cellular telephone signals among said cell sites; and (d) determining, on the basis of said times of arrival differences, the locations of the cellular telephones responsible for said cellular telephone signals. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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Specification