Adaptive algorithms for reducing PCS network authentication traffic

Two authentication schemes (ASs) have been proposed in the Electronic Industry Association/Telecommunications Industry Association´s (EIA/TIA) Telecommunications Systems Bulletins (TSBs) 51 for incorporation in the cellular industry Interim Standard IS 41 Revision C. In the first scheme, which we refer to as the WS scheme, a unique secret key [also known as shared secret data (SSD)] is shared only between the authentication center (AC) and handset. In the second scheme, referred to as the S scheme, the SSD is also shared with the visited system. The performance of the two schemes can be compared by using the expected number of call originations/terminations between two consecutive registrations or call-to-mobility ratio (CMR). Based on the message flow (accesses to databases), it is apparent that the S scheme outperforms the WS schemes if the CMR ratio is large. The CMRs of users will likely span a wide range and, even for the same user, will perhaps vary from time to time. It is therefore desirable to switch between the ASs based on the users´ CMR to reduce the signaling network traffic. We propose two adaptive algorithms to determine how and when to switch between the ASs for a given user. Our performance study indicates that as the CMR of a user changes, the adaptive algorithms automatically select the best AS in real time