Patent ID: 6101378
Filing Date: 2000-08-08
Classification: H04M,H04W

Abstract:
A radiotelephone system for providing prepaid mobile telephone service to subscribers, comprising:(a) a plurality of mobile telephone units, each:(i) being associated with one of the subscribers;(ii) storing an identification of the associated subscriber; and(iii) including a first modem being capable of sending the identification of the associated subscriber whenever a call is attempted over the mobile telephone unit;(b) a plurality of base stations, each of said base stations having means for establishing a voice channel between it and one of said mobile telephone units for each call initiated or received at said mobile telephone unit and said base station also having means for controlling calls and providing control information and power level information between said base station and one of said mobile telephone units for mobile telephone service being provided to said mobile telephone unit; and(c) a debit processing unit having a link to at least one of said base stations and also having:(i) means for storing a database, for each subscriber the database contains a balance of money remaining in an account corresponding to the subscriber;(ii) a second modem connected to a point along the voice channel, said second modem being in data communication with said first modem, said second modem including means for receiving information over said voice channel established by said base station in bursts in a blank-and-burst format, the first and second modems sending signals to and receiving signals from each other in bursts, each said burst comprising a synchronization word having a variable error threshold and said synchronization word for enabling one of said modems that is receiving said burst to differentiate the burst from the voice signals carried over the voice channel, the voice signals being muted during each burst, whereby the first and second modems provide a data channel between the mobile telephone unit and the debit processing unit seemingly concurrently, and with minimal interference with the voice signals that are being carried over the voice channel, and without requiring modifications to the base station, and wherein said information being sent over the voice channel includes the identification of the associated subscriber sent by one of the plurality of mobile telephone units when a call is attempted over the mobile telephone unit; and(iii) means for selectively permitting, over said link, the call to be connected if the balance of money remaining in the account corresponding to the associated subscriber exceeds a first specified amount, and if the call is permitted, reducing the balance of money remaining in the account corresponding to the associated subscriber; and(iv) means for denying, over said link, said call by sending a command to said mobile unit associated with the subscriber to terminate the call if said balance is below said first specified amount.