Driven by the increasing implementation of voice over Internet Protocol (VoIP) systems, the worldwide VoIP control equipment market will surpass $5 billion by 2010, according to Gartner, Inc. In 2010, 77 percent of all investment for call control layers is forecast to be based on IP Multimedia Subsystem (IMS) architecture, while 23 percent will continue to go into enhanced softswitch technologies. Although IMS will be a thriving core architecture by 2010, it will have minimal impact as an application architecture beyond voice.

"As wireline and wireless operators are deciding to build out VoIP services using a call control layer with softswitch and media gateways, they are confronted with a choice between a traditional voice-oriented softswitch architecture or softswitch solutions that can be upgraded to support the IMS topology," said Bettina Tratz-Ryan, research director for Gartner. "Operators that want to emulate existing voice services on time division multiplexing (TDM) infrastructure and see voice as a discreet service will opt for established softswitch topologies. Operators comfortable with not having to offer all the legacy voice services and that see value in offering new value-added voice services will need to decide between an IMS upgradeable or IMS compliant solution."

Operators with a clear path to fixed-mobile convergence (FMC) and converged services across voice, video and data will be deploying horizontal session control architectures such as IMS. Wireline operators have taken the lead in deploying next-generation network (NGN) architectures that can benefit from IMS to realize operating expenditure savings and provide a basis for converged applications in the long run.

However, for operators implementing VoIP to emulate their existing voice services, deploying IMS will not offer material benefits over traditional softswitch-based architectures. The latter are less expensive and have been market tested. Most modern softswitches also have a migration plan to IMS.

For operators planning to offer value-added VoIP services, IMS delivers long-term core networking efficiencies. It also offers a standardized way of providing value-added voice applications, such as push-to-talk over cellular. This will lead to lower total cost of ownership and less vendor lock-in. But these advantages will take time to develop and are not expected within the next 24 months.

"IMS will offer the best advantages over the implementation of softswitch architectures in FMC because it can rely on a massive industry standardization effort," said Tratz-Ryan. "That effort will open the doors for operators to evaluate a broader range of solutions with different implementation elements for different services. Vendors can build comprehensive ecosystems that operators can feed from, with interoperability with application and content providers." KW