Importance

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Abstract

A method of supervising the subscribers in a mobile telephone system to detect audulent use of a mobile telephone. A fraudulent subscriber (MS2) can have the same identification number (12) as that (11) of a legitimate subscriber (MS1) and the operator of the system cannot discover the fraudulent use. According to the proposed method, a predetermined sequence of numbers (00, 01, . . .20) is assigned to each mobile telephone in the system. When a call is made by a subscriber across a control channel it is followed by a particular number in the sequence across the allotted voice channel and this order number is recorded in the toll-ticketing records in the mobile switching centre (MSC). When the next call is made from the same subscriber, the next order number is sent and recorded. Thus all the calls from a legitimate subscriber are recorded in a determined sequence. The order number from a fraudulent subscriber's call will break the legitimate subscriber's sequence and the fraud can be discovered by this break.

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First Claim