Inter-PLMN handover-an approach for a functional requirement description

Today, provision of service within a particular mobile network requires previous subscriber registration within this network. This contribution addresses the question which network prerequisites are required for seamless continuation of a call even if the radio resources are provided by a network different from the one where the subscriber is currently booked in. The mechanism allowing continuation of a call when moving from the coverage area of one mobile network into the coverage area of a different network is called "inter-PLMN handover". The related service requirements and resulting protocol extensions necessary in GSM PLMNs are investigated, The introduced approach is extended to inter-standard handover.