US 5,905,949 AGranted

Cellular telephone fraud prevention system using RF signature analysis

AssigneeCorsair Communications, Inc.

InventorsKelly Davidson Hawkes, Michael Shaw McKinley, Kenneth Irwin Talbot

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Abstract

Apparatus for identifying wireless subscriber units and for determining if access to a communications network should be granted. A plurality of wireless subscriber units each generates a wireless subscriber signal including internal data traits and external signal traits. The internal data traits include an identification code. A RF downconverter is located remote from the wireless subscriber units and receives the wireless subscriber signal. A characterizing device is connected to the RF downconverter and extracts parameters that characterize the external signal traits of the wireless subscriber units. A decision device computes the likelihood that the observed parameters belong to the validated wireless subscriber unit to determine if access to the wireless subscriber service should be granted. The apparatus may be used to prevent cellular telephone cloning fraud.

Claims15

Dependent claims

A transmitter identification system including a plurality of transmitters, each transmitter broadcasting a transmitter signal having an identification code where the plurality of transmitters in include a plurality of authorized transmitters and one or more unauthorized transmitters where at times,

each authorized transmitter has an authorized identification code and transmits an authorized-transmitter signal having authorized-transmitter modulation characteristics and containing said authorized identification code,
each unauthorized transmitter transmits an unauthorized-transmitter signal having unauthorized-transmitter modulation characteristics and containing an unauthorized identification code identical to an authorized identification code of an authorized transmitter,
said transmitter identification system comprising:
receiving means including two or more antennas, each antenna receiving a particular transmitter signal and providing a corresponding antenna output signal and including two or more RF downconverters, each RF downconverter processing a different antenna output signal to provide a downconverted signal, whereby two or more single downconverted signals are formed,
combining means for combining said two or more single downconverted signals to form a combined signal representing said particular transmitter signal, said combined signal having a signal-to-noise power ratio greater than a signal-to-noise power ratio of any single downconverted signal,
demodulating means for demodulating said combined signal to recover a particular identification code contained within said particular transmitter signal,
extraction means for extracting parameters representng said modulation characteristics from said combined signal, and
determining means for determining the likelihood, based on said parameters, that said particular transmitter signal is not from an authorized transmitter having an authorized identificaton code the same as said particular identification code.

5 more elements

A transmitter identification system including a plurality of transmitters, each transmitter broadcasting a transmitter signal having an identification code where the plurality of transmitters include a plurality of authorized transmitters and one or more unauthorized transmitters where at times,

each authorized transmitter has an authorized identification code and transmits an authorized-transmitter signal having authorized-transmitter signal characteristics and containing said authorized identification code,
each unauthorized transmitter transmits an unauthorized-transmitter signal having unauthorized-transmitter signal characteristics and containing an unauthorized identification code identical to an authorized identification code of an authorized transmitter,
said transmitter identification system comprising:
receiving means for receiving a particular transmitter signal and providing a corresponding received signal,
demodulating means for demodulating said received signal to recover a particular identification code contained within said particular transmitter signal,
extraction means for extracting parameters from said received signal, said extraction means including processing means for processing a plurality of signal characteristics to form said parameters, and
determining means for determining the likelihood based on said parameters, that said particular transmitter signal is not from an authorized transmitter having an authorized identification code the same as said particular identification code.

4 more elements

Dependencies are inferred from the claim text.