"The IP Multimedia Subsystem (IMS) is an architectural framework for delivering internet protocol (IP) multimedia to mobile users. IMS Architecture is horizontal that separates service layer from access network, making it access network agnostic."

Service providers see the potential of generating new revenue streams by becoming a one-stop shop for all the communication needs of a customer, and are in the process of constantly refining their service offerings. With operators migrating from circuit switched networks to next generation packet-based networks, the convergence of voice, video and data termed as triple play have received a major boost. IMS is the corner stone in next generation networks. It will increase network efficiency and enable faster and easy introduction of innovative complex bundled services and a greater variety of rich multi-media services to subscribers.

Next generation networks based on IMS architecture support a range of new service types like voice and push-to-talk, presence and location aware applications, Internet access and content delivery, instant messaging, multi-party, multi-media communications sessions etc.

The IP Multimedia Subsystem (IMS) is an architectural framework for delivering internet protocol (IP) multimedia to mobile users. IMS Architecture is horizontal that separates service layer from access network, making it access network agnostic. IMS is not intended to standardize applications itself but to aid the access of multimedia and voice applications across wireless and wireline terminals, i.e., aid a form of fixed mobile convergence (FMC). IMS architecture greatly helps service providers reduce cost and offers customers combined multimedia service components like - text, pictures, content, voice and, video over a single connection in real time.

Convergence, interoperability, and new models based on IMS framework are driving innovation in charging and AAA.

IMS charging is appropriate for traditional volume-time-based charging schemes, large service bundles, and complex tariff functions. Its fully defined charging architecture supports convergence of prepaid-postpaid billing and integration of application servers and services. It support both offline and online charging, however the significant difference in IMS from other architectures is that operators don't need to categorize subscribers into prepaid and post-paid groups; they can allow subscribers to access a wide range of events within a single session and charging can be combined in the same session.

Real-time charging cannot work without harmony with the network, through an intelligent AAA server that helps manage services on real time basis through policy definition such as quota-based session control, QoS based service delivery etc. Not having a close relationship with the network, which is effective and efficient at the subscriber and application-level means IMS based charging cannot be achieved to the full. AAA is the answer to the aggressive and ever-growing access control, service delivery, and accounting requirements of carriers, service providers, and wireless operators. The next generation networks and services need a convergent AAA solution (SIP/VoIP, Cable TV/IPTV, GSM/UMTS, and DSL/Cable) to manage services. A carrier-grade, cost-efficient AAA server that can be fully integrated with next generation HLR and HSS elements.