Network functions and signalling for personal roaming between digital cellular standards

A possible short-term solution for creating an inter-cellular standard roaming service is presented. An inter-cellular standard roaming service is, for example, the service whereby a GSM mobile subscriber can roam into a PDC network operator by means of a user identity module. For interconnecting the different cellular systems, two network nodes called "interworking location register (ILR)" and "interworking mobile services switching center (IMSC)" are proposed. These network nodes are designed to cause no modifications in the original cellular system. With this in mind, the network architecture of the digital cellular standards is considered. Furthermore, the outline of the basic call procedures for the roaming subscribers based on the proposed network architecture model is described.