Cellular Technical Services Company, Inc.

Randy McKernan

David M Stanhope

David N Hoogerwerf

Dmitry Kaplan

Evan R Green

Chetan Sharma

A method and system for actively and rapidly collecting reference waveforms from a large number of cellular telephones is provided. The reference waveforms are used to generate fingerprints which are used to distinguish between authorized cellular telephones and unauthorized cellular telephones. Initially, the system selects a cellular telephone whose reference waveform is desired. The selected cellular telephone is then sent a polling message such as a page or registration request. The cellular telephone receives the polling message and transmits a radio frequency (RF) signal containing a reference waveform that contains certain transmission characteristics unique to the selected cellular telephone. From the received RF signal, the reference waveform is extracted and stored. Preferably, the selected cellular telephone is polled repeatedly in order to receive a sufficiently large number of reference waveforms to be able to generate an accurate fingerprint. One method of polling the cellular telephone is by calling the selected cellular telephone through a cellular telephone system. Another method of polling the cellular telephone is by transmitting a control message such as a page, registration, audit or maintenance message.

Active waveform collection for use in transmitter identification

A method and system for detecting a voice channel grab by a pirate in a cellular telephone network. Initially, RF signals transmitted to and from an authorized cellular telephone over the control and voice channels are monitored to track call processing activities and obtain various data that are used to detect potential voice channel grabbing attempts. The data may include such things as RSSI, change power output messages and responses, and hook-flash signal. From the data, the system looks for two events. A first event is an unexpected change or an absence of an expected change in the voice channel RF signal indicating that the pirate may be transmitting on the voice channel. The first event may be any one or more of the following: (1) a sudden upward shift in the voice channel RSSI; (2) an unexpected phase shift of either the RF signal or the SAT signal contained in the RF signal; and (3) an absence of an expected shift in the RSSI that corresponds to the change power level message from the network. The second event is receipt of a message indicative of a request to establish a new telephone connection such as a hook-flash message initiating a call conference. When the unexpected change in the RF signal and the message indicative of the request to establish the new telephone connection are detected, the system determines that the voice channel assigned to the authorized cellular telephone has been grabbed by the pirate. When the system determines that the channel grab has occurred, it prevents the pirate from establishing the new telephone connection by preventing receipt of dialed digits or terminating the connection on the voice channel.

Detection and prevention of channel grabbing in a wireless

A system analyzes telephone calls that have been determined by signature analysis to be fraudulent and stores parameter data associated with the fraudulent cell phone. During subsequent cell phone calls, the system compares the stored parameter data associated with the fraudulent cell phone to corresponding parameters from a subsequent call to determine whether the subsequent call is from the fraudulent cellular telephone. In this manner, the system may reject subsequent cellular telephone calls as fraudulent without the need for time consuming signature analysis. Parameters analyzed by the system can include the time of day of the fraudulent call, the origin from which the fraudulent call was placed, the transmitted identification numbers of the fraudulent telephone, and the destination telephone number of the fraudulent call. The system can analyze one or more of these parameters in combination to determine that the subsequent call is fraudulent.

Growing community of inventors

Graton, CA, United States of America

Randy McKernan