FEATURE: Easing the Transition to IMS

IMS Deployment Environment: Greenfield or Big Dig?

By now, most of us in the telecommunications industry are familiar with Internet Protocol Multimedia System (IMS)--the drivers, architecture and benefits. Almost every week we hear about another "IMS-Ready" win--though the press release never really explains what exactly "IMS-Ready" means. But rarely, if ever, do we hear of a real, honest-to-goodness, IMS deployment.

In fact, a quick Google search on "call session control function (CSCF) commercial deployment," with the CSCF being the heart of the IMS signaling core, returned several pages of results, with none of the first few pages from a service provider. The truth is that most of the returned results were white papers from vendors trying to pitch CSCFs to carriers.

What many people forget to include in their discussions about IMS is how to overcome the challenges associated with moving from today's networks to IMS networks. Vendors are out pitching IMS as if they're in a "Greenfield Vacuum," and operators are conducting lab trials in what is essentially a clean-room lab experiment. The reality of an IMS field deployment is more analogous to Boston's well-known "Big Dig" than to a Greenfield deployment.

For those not familiar with the Big Dig, it is a project in Boston to replace an elevated highway that runs through the city with an underground tunnel. The path for the tunnel was under the existing roadway and the city needed to build the tunnel while keeping the existing roadway in place, so that it could continue to carry traffic through the city. Needless to say, this turned out to be a real engineering and financial challenge. Despite the many obstacles and issues surrounding the Big Dig, it was in many ways a spectacular engineering accomplishment.

Each and every carrier that deploys IMS will be faced with similar challenges. They will be forced to deploy new IMS-based technology, and at the same time, they will be forced to keep much of the existing technology in place for quite some time because complete replacement with IMS will not happen over night and is cost prohibitive. At the same time, although continuing to use the pre-IMS infrastructure, carriers will be interested in minimizing their investment in the pre-IMS technology.

IMS presents a number of key challenges from both a technical and business perspective. From the business case perspective, key questions include "what applications do I deploy first?" and "when and how do I make the business case work for IMS when the majority of my customers will be on a 'pre-IMS' infrastructure well into the future…?" And, from a technical perspective, the issue of systems integration and multi-vendor interoperability are a concern.

How can operators ease the technical and financial pains of transitioning to an IMS architecture? The answer is...via session initiation protocol (SIP)-signaling system 7 (SS7) Service Mediation.

The Bridging Technology: SIP-SS7 Service Mediation

With a substantial investment in existing circuit-switched networks, operators need to leverage their existing resources and services to maximize the return on investment as they transition to a new technology.

SIP-SS7 Service Mediation products enable service interaction between legacy, mobile and IMS networks and serves as the "bridging technology" to the next-generation of network technology, without requiring upgrades of existing network elements or a complete migration of all existing services to the SIP/IMS domain. The transitional products allow service delivery across multiple domains, enabling intelligent network (IN) service platforms to coexist and interact with SIP-based application servers.

SIP-SS7 Service Mediation is the "bridging technology" that enables access from the 2G/time division multiplexing (TDM) domain to the IMS domain and from the IMS domain to the SS7 domain. For example, one can move from the IMS domain to a number portability database or from the 2G domain to an IMS-based voice mail or multimedia mail server in the IMS domain.

Access to SIP Applications from the 2G/TDM Domain

Operators can increase their revenue opportunities by delivering new services to legacy clients using IMS platforms. However, many will need to maintain legacy TDM voice networks for some time after the introduction of VoIP networks that provide interoperability between technologies as well as serve subscribers who are slow adopters. The VoIP network brings a unique set of SIP-based service offerings such as web-based call management, click-to-dial and unified messaging--which are not generally available to an end user in the legacy voice network. To maximize VoIP and IMS investments, open up new revenue streams and encourage subscribers to migrate to the new technology, the ability to offer next-generation services in the legacy voice network is equally as important.

SIP-SS7 Service Mediation gives legacy TDM voice networks access to next generation, SIP-based services, such as click-to-dial, remote call management, advanced call treatment, unified messaging and dynamic call routing. Operators can offer newly deployed services to legacy subscribers and generate fresh sources of revenue.

It's a win-win situation. Operators can save money, while making money, maximize revenues, and reduce costs making the IMS business case work. The bottom line results are lower cost, easier transition, and richer, more profitable services.

Steve French is a senior manager of Tekelec's Product Marketing Network Signaling Group. 

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