System with a dual mode WLAN/GSM terminal in which calls are established over WLAN or GSM network

摘要

The present application relates to dual-mode GSM/WLAN terminals and how to establish calls in a convenient and cost-effective manner. In the prior art the user has to manually select between the access technology to use. This problem is solved by the application in that, when a terminal with an active account enters the coverage area of the WLAN, the server registers the terminal to the WLAN. When another terminal sends a call request to it (INVITE sip: 358041111111@server), the [SIP] server will proxy the call request message to it (INVITE sip:userB@10.0.8). If the called terminal is not registered or does not even have an account then the [SIP] server will tell the calling terminal to do a GSM call.