Importance

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Abstract

A system and method extracts a portion of a transmitted waveform and compares the transmission characteristics of the extracted waveform to determine if they match a stored fingerprint associated with the transmitter, such as a cellular telephone. The system adaptively creates fingerprint data by storing a plurality of waveforms believed to be from a particular transmitter and calculates the variability of the individual transmissions with respect to a composite mean waveform of the transmission characteristics. The system emphasizes the variability between the individual waveforms and the composite mean waveform and determines variability values for each of the individual waveforms in the fingerprint. When the system receives an additional unidentified transmission purported to be from the transmitter with the stored fingerprint, the system determines whether the variability of the unidentified waveform fits within the predetermined margins of variability for the fingerprint. If the variability of the unidentified waveform is less than a predetermined variability threshold, the system considers the waveforms to be a suitable match. The system can adaptively include new waveforms in the fingerprint by determining whether the newly-received transmission characteristics meet a series of criteria for inclusion in the fingerprint. In addition, the system analyzes the newly-received waveform and all waveforms forming the fingerprint to determine if any of the waveforms exceed a predetermined maximum variability value. A waveform that exceeds the maximum variability value is eliminated from the fingerprint. The system is easily automated, thus providing a useful analysis technique for communications network such as cellular telephone systems where a large population of transmitters with similar transmission characteristics are operating at any given time.

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First Claim