However, for operators to deliver these benefits requires a smooth transition of the services in the circuit switch network to the IP Multimedia Subsystem (IMS) network. Jonathan Bell, VP Marketing at OpenCloud, discusses how an evolutionary transformation of the service layer is required for operators to transition to VoLTE with no negative effect on the subscriber.
In a traditional circuit switched network used to deliver 2G and 3G services, the switch provides a lot of the basic call handling functionality such as call forwarding and call barring. Over the years, most new services and additional functionality have been added to the circuit switched network. They have been developed on additional Intelligent Network (IN) platforms rather than by making changes to the switch. The IN platform has enabled operators to create value-added services which complement their existing core telephony and communication service offerings. These are services that businesses and consumers worldwide often take for granted as the basic fabric of the network itself, such as voicemail, number translation, least-cost routing and mobile roaming. Most importantly, operators have developed premium revenue generating business services for the enterprise market. There are countless variations of such service implementations and most operators have fifty to a hundred different services being used and valued by enterprises and consumers alike.
In the IMS network, the ‘switch’ is just a router and does not provide any of the call handling capabilities that are provided by a circuit switched telephony switch. The Multimedia Telephony Telecom Application Server (MMTel TAS) provides the equivalent call handling on the IMS network. The GSMA IR.92 VoLTE standard specifies the set of basic call handling capabilities required of an MMTel TAS. IR.92.However, the standard does not address any of the additional functionality that has been added to all legacy networks on IN platforms and is still being used to deliver services today.