SBC-Enabled Enhancement of IMS Resilience in Outlying Islands

Chunghwa Telecom has developed a Session Border Controller (SBC) system, referred to as CHT SBC, which supports IP multicast technology. When the primary voice call path between the voice gateway and the IMS (IP Multimedia Subsystem) network fails, the voice gateway switches to local call mode, allowing only local users to communicate with each other via IP multicast. CHT SBC interfaces with the IMS network through heterogeneous networks, such as satellite or microwave links and supports both IP multicast and unicast functionalities. It is capable of receiving multicast signals and converting them into unicast for transmission to the IMS network as well as receiving unicast signals from the voice gateway and forwarding them to the IMS network to establish the connection. Considering the limited bandwidth of heterogeneous networks, CHT SBC is equipped with user and bandwidth control features to manage the number of users and active calls, thereby ensuring consistent call quality.