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March 2008 | Volume 11/ Number 3
Feature Articles

The Further Adventures of IMS

By Richard "Zippy" Grigonis

The IP Multimedia Subsystem (IMS) is an upcoming common network service delivery architecture for both wireless and wireline applications. With IMS, Internet-type wireline applications can now be delivered just as easily to mobile devices as desktop-bound PCs. This is sort of ironic since wireline operators envy the advanced applications being deployed in the wireless world, and the wireless operators have always been jealous of the broadband capacities now available in the wireline world.

By decoupling and modularizing everything (in schematic diagrams if not yet in real life), relying on development platforms that re-use network resources such as group list management, location, presence, etc., and controlling the whole shebang with software and SIP (Session Initiation Protocol), network operators and even third party developers adopting IMS should both easily and quickly be able to hatch as many new services as they can possibly think up, then try them on their customers. Those services finding favor with the public will be marketed and promoted extensively. Others will vanish, never to be seen again.

From its humble beginnings in 1999, in an industry forum called 3G.IP, IMS was picked up and elaborated by the wireless standards body 3rd Generation Partnership Project (3GPP), and a succession of other standards bodies, such as the 3GPP2 and TISPAN. These groups continued to add to IMS’ capability, increasing its scope beyond the original GSM/GPRS formulation to embrace Wireless LANs, CDMA2000, fixed line, WiMAX, and every other network in the known universe. The mobility aspect of IMS alone helps in the transformation of unified messaging into unified communications. And although IMS isn’t entirely synonymous with Fixed-Mobile Communications (FMC), the concept of Voice Call Continuity (VCC) between wireless LANs and cellular mobile devices has become a major topic of interest – or bone of contention, if one talks to proponents of IMS’ competing technology, UMA (Unlicensed Mobile Access). UMA is a “quick fix” technology for existing networks that enables roaming between GSM cellular and Bluetooth or WiFi (it’s now also known as the Generic Access Network, or GAN).

As has been pointed out by others, IMS is really more of a software-centric approach to multimedia services networking. And with IMS you contact a person on the network, not a device or series of devices if you don’t know exactly where the person is at the moment. IMS thus provides network operators with a new-found flexibility and simplicity when it comes to development and deployment. But the problem, as stated by one European carrier, is that with IMS, “one has to pay a lot to achieve simplicity”. Moreover, in the absence of a bevy of futuristic “killer apps” waiting to be deployed, services initially ported to IMS include such time-honored, revenue-generators as voice service.

Then there’s the possibility that no services are ever be ported to IMS, depending on the “corporate culture” of the carrier and the size of their pocketbook. Even carriers that were quite gung-ho on IMS, such as BT and France Telecom, have had to slow down as they await network element interoperability testing to take place and second sources for the equipment to appear.

A 2007 poll by Comptel Corporation (, a maker of dynamic Operations Support Software (OSS), found that 32 percent of operators worldwide had decided to move towards an IMS architecture within the next two years, but about another third (32 percent) had made no such plans. The remaining service providers foresaw IMS deployment in 2 to 4 years (27 percent) or beyond that time (6 percent). The always-optimistic Americans had a majority of operators (78 percent) expecting to adopt the IMS architecture sometime over the next 2 to 4 years. In the rest of the world, about half the operators expected to migrate to IMS within two years (Asia-Pacific – 50%, Europe – 47%) but a sizeable chunk hadn’t decided whether they would ever migrate to IMS (Asia-Pacific – 50%, Europe – 41%).

Many pundits have decried the slow progress of IMS adoption by the world’s network operators and service providers, and predict that at best we’ll see partial, piecemeal implementations of IMS here and there in the network.

Such opinions about IMS are always almost immediately counterbalanced by news such as the recent announcement that Nokia Siemens Networks ( is supplying T-2 Slovenia, the country’s leading IPTV and Internet service alternative provider, with Europe’s first Internet High Speed Packet Access (I-HSPA) network, an architecture developed by Nokia Siemens to bring full wireless mobility to ‘heavy’ data and rich multimedia traffic, along with a complete 3G network based on Wideband Code Division Multiple Access (WCDMA) technology. There will also be a Nokia Siemens MSC Server mobile softswitching solution supporting IMS, which will enable T2 Slovenia to rapidly introduce new IP-based voice and multimedia services.

And NewStep Networks (, the company that provides solutions enabling what they describe as an “any device, any place, any content” communications experience, since 2006 has partnered with Embarq ( to deliver IMS-based FMC using NewStep’s Converged Services Node (CSN), an application server that employs signaling to control user sessions while enabling PBX features on mobile phones. The CSN can be hosted in a carrier’s network, and works fine with pre-IMS and IMS architectures in any domain — fixed, mobile, broadband or enterprise. Embarq used the CSN to roll out its initial “Smart Connect” services in October 2006, which enables users to have a single phone number and voicemail box for multiple devices, and which can easily switch calls from a wireless network to a corporate WiFi network. An even more sophisticated service, Smart Connect Plus, uses a dual-mode handset from UT Starcom (, a company that sells converged broadband wireless and wireline products, an integrated IPTV solution, and a full line of handset and customer premise equipment to operators in both emerging and established telecom markets.

NewStep also has partnerships with fg microtec and Paragon Wireless. As it happens, fg microtec ( provides of best-of-breed multimedia applications for 2.5G, 3G and WLAN mobile phones, such as OMA/IMS compliant push-over-cellular clients, IMS and SIP-based VoIP solutions including VCC for converged GSM and VoIP applications, video telephony and video sharing over 3G and WLAN networks. Paragon Wireless ( offers customizable, inexpensive VoWLAN handsets and solutions known for their user-friendly interfaces. They offer SIP/IMS-based dual-mode solution for both GSM and CDMA.

A User-Oriented Architecture?

Other, more dire predictions involve looking upon SOA (Service-Oriented Architecture) and Web Services as alternatives to IMS and its service architecture. Amazon, Google, Microsoft and other IP-based players are focusing on Web Services APIs that can be used to take existing platforms and create “mash-ups” of new, composite packet/circuit applications. Such critics fail to realize that these are not competitors but are in fact powerfully complementary to IMS and even SIP as a service control protocol.

How? Superficially, one could say that SOA is basically another way of describing a component model for distributed systems, similar in a way to the ideas behind such things as CORBA, and that IMS is also a modularized distributed system and resembles an SOA. As Martin Cookson, of BEA Systems wrote online in 2006: “In IMS does not deliver the complete architecture for an operator. This requires the combination of an OSS/BSS architecture, service creation and execution (OMA OSE?), device architecture, data model, etc. The IMS is however an important (and large) component. An IMS therefore must expose mechanisms which can be composed and orchestrated to form part of an overall enterprise approach to build complete communication products. The comparison of an IMS to SOA is a good one. Perhaps the reality is that the SOA architecture is applied recursively. An IMS is a SOA instance, content management is a SOA instance and OSS/BSS systems are a SOA instance. All three (and more) form part of a telecom enterprise SOA. The next step is the SOA marketplace in which enterprises interchange services (IMS session from the operator and financial transaction from a bank) and compose new products.”

But the relationship can be made much deeper. As telecom consultant and IMS expert Christophe Gourraud writes, “An important question is how the integration of IMS and SOA should be performed. At the moment, the prevailing understanding is that it should take place uniquely through the definition of Web Services, permitting to integrate a SIP-centric IMS with a Web Services and SOA-centric application layer. I believe that this view is incomplete and that the optimal integration between IMS and SOA should be more intimate, considering that IMS service logic should combine the direct usage of SIP and Web Services for service delivery, instead of only developing SIP-centric logic and web services-centric logic connected through a loose Web Services adaptation layer, similar to the one that connects the pre-IMS networks with SOA. I gave a name to this more intimate integration architecture, which extends both OSA and the standardized IMS service architecture: the User Oriented Architecture (UOA).”

In any case, there is almost universal agreement among standards groups that IMS will ultimately reign in the global network. Its closest competitors (e.g., UMA) don’t have its vast scope, nearly every equipment vendor is building IMS-compliant products, SIP has indeed emerged as the de facto call control/signaling standard, and even the aspects of the IMS model based on some far-out assumptions (popularity of presence and video) have turned out to be correct.

Like VoIP, IMS will slowly percolate through the world’s network, just a VoIP did over the past 12 years. Good things come to those who wait. IT

Richard Grigonis is Executive Editor of TMC’s IP Communications Group.

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