IMS has been variously described as “ERP for the telecommunications industry”, “software that gives telecoms networks the flexibility of the internet”, “an operating system for converged networks”, and even, controversially but not quite accurately, “an attempt to turn the Internet into an extension of the mobile phone network”.

So what exactly is it? Given that the IP multimedia subsystem (IMS) was formally defined in 2002 by the 3GPP (the 3rd generation partnership project), a global telecommunications industry body, this should be a simple question. But the standards-based description of IMS is a sprawling, evolving one, and the political and technical goals have shifted over its short and largely theoretical lifetime.

Initially, the goal of IMS was to help mobile service operators around the world produce advanced, interactive and interoperable services cost effectively, using a standardised base. Effectively, the operators wanted an architecture into which new application components, such as text messaging or push-to-talk could be plugged, reducing the need for functional silos, proprietary solutions and unnecessary duplication.

Enterprise software specialists will understand the analogies with ERP and the fast-evolving architectural framework, the service-oriented architecture (SOA). Like enterprise resource planning (ERP), the goal is to horizontalise services onto a common core, such as subscriber databases, reducing complexity and increasing agility. But like the SOA, IMS is not a package, but a framework; as long as new services or components conform to the standards, they can be plugged in to make use of common services.

With the packetisation of voice (voice-over-IP or VoIP) emerging, it was an obvious decision to chose the emerging Internet standard, Session Initiation Protocol (SIP) as a signalling mechanism, enabling simple, peer-to-peer voice, text and multimedia services to be set up across networks.

Later, it became clear that SIP and IMS could be of great value to fixed line telecoms companies, as well as mobile companies. They could use the standards to interoperate with mobile services, and could also use it to support converged IP services, such as VoIP, and the standardised solutions would help to reduce costs. Because the transport mechanisms are separate, IMS can be used to manage diverse services (WiFi, cellular, fixed) from a common base.

During 2006, IMS has suddenly taken on an urgent new importance. Portal operators such as Google, and eBay (with Skype, its VoIP service) can use SIP and other simple Internet standards to offer telecoms and media services. They can offer voice calls, TV programmes, and interactive sessions – all piggybacked onto a basic Internet data connection. And with mobile networks offering greater bandwidth, they will soon be doing this over mobile networks.

IMS is seen as a potential saviour: the telecoms companies can not only use it to rapidly develop all these new services – at lower cost than before – but they can also blend services together and offer them as part of a bundle – along with the transport mechanism(s).

Further reading

Telecoms' grand design - lead feature on IMS, April 2006

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