Private communications network system and method of authentication for a mobile station used in private communications networks

A private communications network system comprising at least one first private branch exchange interconnected to second private branch exchanges in a plurality of other private communications network systems by transmission lines, and having a plurality of base stations and a plurality of first mobile stations for providing mobile communication services, said private communications network system further comprising:

• common data management means provided in common to a plurality of private communications network systems including said private communications network system and interconnected to said first and second private branch exchanges by transmission lines for communicating with each private branch exchange, for managing group number data corresponding to an identification number of a mobile station of each private communications network system and network identification data including a private communications network system number and billing information corresponding to the group number information;
• subscriber data corresponding to each of said first mobile stations and stored in said first private branch exchange, said subscriber data indicating authentication information and location information;
• temporary subscriber data stored in said first private branch exchange and provided for a second mobile station from another private communications network system, that has entered into said private communications network system and requested mobile communications, said temporary subscriber data indicating authentication information and location information of said second mobile station and authentication means for authenticating the second mobile station having requested mobile communications in said private communications network system, said authentication means comprising
• inquiring means for communicating with said common data management means for requesting and receiving identification of a private communications network number corresponding to said second mobile station;
• requesting means for communicating with a second private branch exchange in one of said other private communications network systems indicated by said identification of a private communications network number for requesting a transmission of subscriber data of said second mobile station and storing said subscriber data transmitted into said temporary subscriber data means;
• and
• control means for authenticating said second mobile station by using authentication information contained in said temporary subscriber data, updating location information contained in said temporary subscriber data, instructing said second private branch exchange in said other private communications network system indicated by said identification of a private communications network number to update subscriber data corresponding to said second mobile station, and notifying the second mobile station that it is authorized to be used in said private communications network system area.