IP Multimedia Subsystems: Easy Does It

Finding a way to converge service delivery over a common control architecture that can be quickly and efficiently reused across multiple applications is a vital piece of the network puzzle for mobile operators working to roll out mass-market mobile data services.

The answer, for many, will be to deploy IP Multimedia Subsystem (IMS) technology, finds this month's Unstrung Insider report, IMS: The Heart of Wireless & Wireline Convergence, which evaluates vendor positioning and strategies for introducing IMS across the wireless and wireline sectors.

Originally defined by the 3rd Generation Partnership Project (3GPP) Release 5 specifications for 3G networks, IMS provides a SIP-based control layer with open interfaces to the transport layer below and the services layer above. It gives operators control over services on a per-session basis, and is expected to provide unprecedented flexibility to the way mobile data is delivered to the subscriber.

Applications enabled by IMS include the ability to launch a circuit voice call from an instant messaging session; the ability to start a video-sharing application during a circuit voice call; multimedia conferencing; multiplayer gaming; and more.

At its base level, IMS consists of Call Session Control Function (CSCF) software, deployed either on a softswitch MSC or on standalone commercial hardware. Media gateways, a Media Resource Function, and a subscriber database (known as the Home Subscriber Server in 3GPP environments) are also specified.

It's not, however, the performance of these individual IMS elements that will set vendors apart. Instead, the service enablers (such as presence), the services and applications themselves (such as push-to-talk), the clients (mobile phone software), and the integration between all of these elements will determine vendor and operator success.

"It's not just about a box built to specification," says Petri Seppänen, head of IMS marketing and sales at Nokia Corp. (NYSE: NOK). "We're taking a 'use-case' all the way through to the terminal from the core." One example of such a "use-case" is last week's announcement by Telecom Italia Mobile SpA (Milan: TIM) of a video-sharing (see-what-I-see) service over a Nokia IMS core to Nokia handsets (see TIM Intros Video Sharing).

According to the Insider report, it seems likely that IMS will be initially introduced into mobile networks in this application-led manner, with operators rolling out specific services, such as the much-hyped push-to-talk, as a prelude to making major strategic commitments to an IMS platform and vendor.

In the longer term, the real benefit of IMS is the capability to develop applications off a common platform that can be reused again and again, says Peter Gersing from the mobile core networks product development team at Siemens AG (NYSE: SI; Frankfurt: SIE).

"IMS provides a horizontal infrastructure for operators," explains Gersing. "Sixty percent of the value today in vertical [applications] is an infrastructure value that you can re-use."

The value of IMS as a reusable infrastructure was also noted by David Cooper, chief technology officer of 3, in an interview with Unstrung in summer 2004 (see Interview: David Cooper, CTO, 3 UK). IMS is a good idea, he said, because it gives flexibility to launch new services without huge upheaval, and with short lead times.

"I'm not foolish enough to think I know exactly what a mass of population will do," said Cooper. "But one or two of these services will take off, and we'll find some things that work in this [mobile] environment, and [those] will be big revenue generators."

But despite this enthusiasm, the rate at which operators will adopt IMS, and therefore the short-term market opportunity for vendors, is uncertain.

"3GPP has defined a fairly heavy implementation that adds some cost and complexity to initial implementations," says Alan Stoddard, general manager of multimedia converged networks at Nortel Networks Ltd. (NYSE/Toronto: NT). "The key will be defining the business case to trigger the initial implementation."

And therein lies the rub: Most everyone is positive on IMS and can see benefits to deploying it, but what really counts is how fast this functionality can be converted into cold, hard cash.

The upshot is that the market for IMS products and services today looks like a slow burner, but one with such potential that vendors must position themselves to capitalize when the fires really start to blaze.

— Gabriel Brown, Chief Analyst, Unstrung Insider

The report, IMS: The Heart of Wireless & Wireline Convergence, is available as part of an annual subscription (12 monthly issues) to Unstrung Insider, priced at $1,350. Individual reports are available for $900. To subscribe, please visit: www.unstrung.com/insider.