Subscriber interrogation point

A method of supplying information to a visited exchange within a mobile radio communications network associated with a mobile subscriber roaming within said network and which is identified by a mobile identification number, said method comprising the steps of:

• storing within a home location associated with each mobile subscriber, data associated with the mobile identification number of each mobile subscriber and related to the service of said subscriber and the last known geographic location of said subscriber;
• storing within a subscriber interrogation point, data related to the identity of the home location of a plurality of mobile subscribers;
• storing within each exchange in said network, data which identifies a subscriber interrogation point associated with the mobile identification number of each mobile subscriber within said network and not an identification of the home exchange of said subscriber so that when the home exchange of a mobile subscriber is changed that information need only be modified in the memory of the mobile subscriber's associated subscriber interrogation point and not in the memory of each visited exchange into which it can roam;
• sending, from a visited exchange in response to a registration request by a visiting mobile subscriber, a location update request message addressed to the subscriber interrogation point associated with the mobile identification number of said visiting mobile requesting registration;
• forwarding said location update request message from said subscriber interrogation point to the home location associated with the visiting mobile subscriber requesting registration with the visited exchange.

An improved cellular radio communications network of the type which includes a plurality of mobile switching centers each having a plurality of base stations with which a mobile subscriber can be connected, a plurality of mobile switching centers which serve as the home exchange for a plurality of mobile subscribers and store within a memory of each preselected information associated with the mobile identification number of each mobile subscriber for which it is the home exchange, a plurality of mobile switching centers which can serve as the visited exchange for a plurality of mobile subscribers for which each is not the home exchange thereof and store within the memory of each preselected information associated with the mobile identification number of each mobile subscriber within the network capable of roaming into said visited exchange, and a data network interconnecting each of said mobile switching centers for the communications of information therebetween, said improvement comprising:

• a subscriber interrogation point connected to the data network for communications therewith and being associated with a group of mobile subscribers the home of exchanges of which are located in a particular geographic area, said subscriber interrogation point having a memory containing information associated with the mobile identification number of each mobile subscriber in said group identifying either the home exchange of that particular subscriber or the identification of another subscriber interrogation point which contains such a home exchange identification;
• and
• means for storing within the memory of each of said plurality of mobile switching centers which can serve as the visited exchange for a plurality of mobile subscribers for which each is not the home exchange thereof information associated with the mobile identification number of each mobile subscriber within the network capable of roaming into said visited exchange, said information identifying the subscriber interrogation point associated with said mobile subscriber and not the home exchange of said subscriber so that when the home exchange of a mobile subscriber is changed that information need only be modified in the memory of the mobile subscriber's associated subscriber interrogation point and not in the memory of each visited exchange into which it can roam.