The IP Multimedia Subsystem is best defined as a third generation core network infrastructure designed specifically for facilitating the delivery of rich, real-time mutimedia services. Apart from rich services, the IMS core network is designed to support high quality multimedia calls consisting of an audio component coupled with a video component. IMS uses the Session Initiation Protocol (SIP) for session setup and teardown while DIAMETER is used as a AAA (Authorization,Authentication and Accounting) protocol.
With the advent of IMS, comes the concept of access independence. Various 3G/3.5G access technologies can be directly plugged into a common IMS core network. A simplified view of the IMS architecture is shown in the figure below.
May it be WiMax or WiFi access, or fixed broadband access, the IMS core network serves as a common ‘glue’ layer for access aggregation. This is a significant value proposition for network operators, as they need to invest in the core network infrastructure only once. This is unlike the current scenario of legacy networks, where a GSM operator has to invest seperately if he wishes to roll out a CDMA2000 network for example.
As shown in the figure, the IMS core network has an application layer which consists of various application server hosting IMS services. The IMS application layer consists of SIP-Application servers and other service delivery platforms.
The IMS-era promises to revolutionize the telco industry. For network operators, it generates new revenue generation streams by enabling them to provide newer, richer and personalized services to the end user. From the perspective of the customer, IMS offers an unparalleled customer experience and a greater choice of services. IMS thus offers a win-win situation for all.
