Sprint dedicates IMS work to voice and enhanced voice services

* IMS-based multimedia applications are some time off in the future

Continuing our series evaluating the status of IP Multimedia Subsystem (IMS) deployments, we spoke recently with executives from Sprint, Manish Mangal, director of core architectures and Mike Logan, director of network development. Sprint is using IMS on a limited basis for both wireline and wireless services.

For wireline services, Sprint uses Session Initiation Protocol (SIP) and an IMS Session Controller (ISC) to provide both consumer and business services. (SIP is the control protocol used for IMS.) Wireline VoIP services to the consumer are offered by Sprint through partnerships with various cable companies.

On the business side, Sprint offers a premises-based VoIP solution and it has partnerships with cable operators to supply hosted enterprise VoIP. Consequently Sprint is using SIP and IMS as a basis for connectivity to other carrier and enterprise voice networks, in addition to its own network.

According to Mangal and Logan, Sprint has worked with multiple vendors to solve some of the interoperability issues for SIP, and they have had “some good agreement on voice and voice extensions;” however “for other services like presence, video, and policies, the standard isn’t that mature and as these [other] services go, there is a lot of work to be done.”

To address some of the operational interface support that IMS still lacks, Sprint has been using a “pre-IMS” environment to provide an operations training ground so that once IMS evolves to include full operational systems support, Sprint will have already shown that it can be done.

When it comes to inter-carrier IMS, Mangal and Logan said the “media gateway work is going on between operators, but anything more sophisticated than a packet interface still faces work to be done.” Sprint solves this challenge by managing the bearer and signaling control separately; splitting the two also provides the operator with better control.

Managing the bearer and control separately also facilitates the Sprint femtocell-based offer. Sprint uses a secure tunnel so that if FMC-generated traffic comes from a legacy handset, it is transported inside the tunnel to stay with the legacy mobile switching center services signaling. But if the CPE supports SIP-based VoIP, then the SIP traffic is taken to the IMS network.

Mangal and Logan believe that the principal focus of IMS work will be dedicated to voice and enhanced voice services for the coming years. Before IMS becomes advantageous for other multimedia services, carriers and suppliers will need to develop more multimedia applications that customers will appreciate enough to pay for. In short, the industry must drive the IMS-supported multimedia applications that will pay the bills to build a full-scale IMS architecture before IMS evolves beyond a voice-focused solution.

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