For now the evidence is anecdotal at best, but conversations with service providers, equipment manufacturers and chip/board vendors seem to show a long-awaited uptick in real-world IMS deployments – though projects remain mostly experimental and small-scale in nature.

Sources consistently pointed to 2006-2007 as the low – or “trough” – point for the IMS hype cycle, with carriers finding it hard to justify the expense or complexity of taking a wholesale plunge into IMS. But those same sources said deployments of IP Multimedia Subsystem network elements and over-arching architectures are now on the rise.

As vendors and service providers prepare for the NXTcomm conference in Dallas next month, news of growing IMS contracts and deployments represent a strong step forward for this up-to-now languishing technology.

“We are seeing an increase, even this year, in the number of IMS deals we are signing; there’s an acceleration,” said David Withington, director of marketing for Alcatel-Lucent’s application division. “It’s not huge, but a number of customers are making significant IMS decisions. As a result of that momentum, other customers are coming back and starting to get interested as well.”

Alcatel-Lucent touted its largest IMS project with AT&T on the voice-over-IP offering delivered over its uVerse network. That offering, still in limited release, uses and IMS-based network to deliver standard calling features like caller ID, click-to-call and messaging. But it also – in limited ways today and in more integrated fashion down the line – aims to use IMS to integrate uVerse voice and video offerings to deliver TV-screen access to caller ID/call history and click-to-call from the IPTV remote.

“There’s still a lot of interest in VoIP as an application that IMS can provide,” Withington said. “But after that, service providers are looking to deliver a broader range of services that can run over IMS.”

Yet despite all the talk of new IMS services, many early deployments are focused on voice-oriented replacement networks, agreed Vikram Saksena, CTO of Sonus Networks.

“The main focus for IMS right now seems to be on the access side, for both wireline and wireless networks,” Saksena said. “We’re seeing quite a few places, though more outside of the U.S., where operators are looking to do Class 5 access-type deployments. We’re also seeing activity in broadband wireless, in particular new wimax networks around the world.”

Overall, said Saksena – in a point echoed by an array of sources – IMS deployments are much more point-oriented these days. “No one is really trying to do a complete IMS deployment in one shot these days,” he said. “It’s a more piecemeal approach where operators focus on projects and pick up the necessary IMS components to make it work.”

That approach is brings together both near-term pragmatism and the desire to future-proof any of today’s investments by tying them to a long-term IMS architecture vision.

Continuous Computing, which provides IMS protocol software and integrated hardware to equipment manufacturers, has seen both vendors and operators focus on affordable, smaller IMS projects with an eye toward rapidly scaling up deployments when a truly “stick” IMS service emerges.

“The cost of deploying a new [IMS] service has to be very, very low,” said Manish Singh, vice president of product line management for Continuous Computing. “A carrier should be able to try out a new service at a very low cost point and if it becomes sticky be able to scale that service up very quickly.”

At least for now, Singh said has seen operators deploy IMS mainly to support basic voice services. But newer applications, in particular on the wireless side, such as SMS off-loading and mobile instant messaging are beginning to emerge on IMS networks as well, he said.

“We don’t have any customers today that aren’t moving to IMS in some form or fashion,” said Chad Hart, product marketing manager for test vendor Empirix. “That’s both vendors and service providers. The deployments may not contain many IMS components, and the initial services may not be doing anything that couldn’t be offered by non-IMS means. But operators are starting to make investments and get in the game.”

Empirix has even seen a growing uptick in sales of IMS monitoring solutions, a step beyond more basic test systems and proof that IMS is starting to gradually move into production networks, Hart said.

“When [a new technology] hits the monitoring side of our business, we know it’s starting to hit,” he said.

A couple of additional trends on the vendor side are also worth noting. Many operators are asking for – and some vendors have even productized – IMS “light” solutions that among other changes from the core IMS architecture do away (at least initially) with the centralized Home Subscriber Server database.

“The one major deviation I see from the standard IMS architecture is operators rolling out infrastructure that is IMS-compliant but that doesn’t use and HSS,” said Alcatel-Lucent’s Withington. “The architecture without HSS is simpler to deploy, quicker to get going and less expensive.”

Also on the vendor front, there has been mild controversy around the concept of single-vendor, “pre-integrated” IMS – where all of the elements either come from a single vendor or are integrated together by that vendor – and the more multi-vendor approach that was originally envisioned for IMS.

“We do believe that going with a pre-integrated package is more cost-effective than a best-of-breed, build-your-own-network approach,” said Alcatel-Lucent’s Withington. “We do understand some operators take a different approach, and we’ll work with them and support that. We’ve done a lot of work integrated third-party application servers into our network, for instance.”

But to some, the concept of single-vendor IMS is a move by larger NEMs to dominate IP the way they did the circuit world. Critics also doubt the success of the strategy.

“Carriers will go with that approach when they are in learning mode, in the lab,” said Sonus’ CTO Saksena. “But when it comes to real deployment, they are enforcing more openness and more distributed architectures.”