Abstract: A method and apparatus for authentication between a subscriber unit and a communication unit is provided. The authentication process includes: maintaining an historic non-arbitrary value in the subscriber unit, generating an authentication message in the subscriber unit as a function of at least part of the historic non-arbitrary value, and transmitting the authentication message to the communication unit. In addition, the authentication process includes: receiving an authentication message at a communication unit, maintaining an historic non-arbitrary value in the communication unit, and determining, in the communication unit, through the use of the received authentication message and the maintained historic non-arbitrary value, whether a received service request is authentic.

Abstract: In a cellular radiotelephone communication system, there is provided a method and apparatus for reducing contention between a plurality of mobile units requesting system resources comprising the steps of A) receiving access requests from at least one of the plurality of mobile units, B) determining the number of attempted access requests (access request count); and C) altering system resources as a function of the access request count in order to reduce the likelihood of contending mobile units. An alternative embodiment suggests deriving timing advance information as well as access request count, correlating the access request count to the timing advance information, and altering system resources as a function of the correlation in order to reduce the likelihood of contention. Yet another embodiment suggests that the mobile unit take independent action, based upon its access request count, in order to reduce the likelihood of contention.

Abstract: Radio frequency based cellular telecommuication systems often require a subscriber (10) to maintain a proprietary identifier (19) or serial number (18) which is transmitted to a fixed network communication unit (20) to verify the authenticity of the subscriber (10). An enciphering and call sequencing method and apparatus are provided which can decrease unauthorized detection of these proprietary ID's (18, 19). This method and apparatus permit efficient roaming by allowing authentication variables for multiple calls to be sent from the "home" system (20) to the "visted" system and stored by the "visted" system for use with subsequent calls. Further, a method and apparatus are provided which force the authenticating mobile (10) to use information that only it has available to itself.