Mobile-station adapted for removable user identity modules

The present invention relates generally to wireless communications systems and, in particular, to mobile-stations for third generation wireless communications systems. A mobile-station with an integrated user identity module (I-UIM) and a removable user identity module (R-UIM) that adheres to the second generation standard intersystem protocol for validation and authentication is disclosed herein. The I-UIM includes an integrated electronic serial number (I-ESN) and integrate-subscriber/subscription information, whereas the R-UIM includes a removable electronic serial number (R-ESN) and remote-subscriber/subscription information. The mobile-station will transmit either the I-UIM and integrated subscriber/subscription information pair or the R-UIM and remote subscriber/subscription information pair depending on the user of the mobile-station. A registry of I-ESNs paired with integrated-subscriber/subscription information and R-ESNs paired with remote-subscriber/subscription information will be maintained by wireless communications systems and/or authentication centers. Such registry is used to validate and authenticate I-ESN and integrated-subscriber/subscription information pairs, and R-ESN and remote-subscriber/subscription information pairs.