Abstract: A roaming interworking gateway has a modular unit associated with an IS.41 system, a modular unit associated with a FSM system, and a translation function. The translation function accesses a database which stores subscriber data upon registration of a subscriber in a roamed mobile system. Each modular unit comprises an authentication center to perform authentication before registration. The RIG is implemented on a distributed hardware structure having a high-speed network to which are connected network access processors (NAP), database servers, and an operations and maintenance processor. Each modular unit resides on a single network access processor. The translation function has a module residing on the NAP of each associated modular unit.