Voice and text data service for mobile subscribers

Intelligent Subscriber Management Unit ISMU, comprising

• a visitor location register, an interface to a public communication network and an interface to a mobile subscriber device via a data network,
• wherein the intelligent subscriber management unit comprises a first part arranged to authenticate a mobile subscriber device using a home location register and/or authentication center associated with the mobile subscriber device, while the mobile
• subscriber device is in reach of an access point associated with the data network, wherein authenticating comprises
• receiving an identity response from the mobile subscriber device in response to an identity request packet sent from the access point to the mobile subscriber device;
• forwarding the identity response to the home location register and authentication center;
• and receiving identification triplets in response;
• challenging the mobile subscriber device using the identification triplets, and receiving a challenge response from a subscriber identity module SIM of the mobile subscriber device, the challenge response including the international mobile subscriber identity IMSI;
• storing the IMSI in a visitor location register and attaching the visitor location register to the home location register;
• and further comprises a conversion part for converting voice and text data service between a first data format suitable for the public communication network and a second data format suitable for the data network, and providing a communication path for the voice and text data service using the interface to the public communication network and the interface to the data network.