| 摘要 |
<p>A telecommunications system includes a first (home) mobile telecommunications network A5 second (roamed) mobile telecommunications network B and a third (virtual) mobile telecommunications network C. The virtual network C does not have its own radio access network but uses the radio access network of network B in accordance with a commercial contract between networks B and C. Network C is a MVNO. When a mobile telecommunications device that has network A as its home network roams to network B, the mobile telecommunications device initially registers with network B as the roamed network. Conventionally, communications between network A and network B would be transmitted via a fixed communication link (25) (such as a leased line). However, in the embodiment described, the network A transmits a command to the mobile telecommunications device, instructing that device to de-register from network B and to re-register with virtual network C. The home network A and the virtual network C include IP routing servers (29,29C) which enable voice over IP calls to be routed between the home network A and the virtual network C via the Internet (31). The calls can subsequently be routed from the virtual network C to the mobile device via the radio access network on network B. In this way, use of the fixed communication link (25) between network A and network B is reduced, thereby potentially reducing the cost of making and receiving calls while roaming.</p> |
