As we saw in yesterday's article, A Tough Call 1: Services to bridge Wi-Fi and cell, some operators are beginning to think about bridging between Wi-Fi and cell-phones, while vendors are beginning to provide them kit to do it. Today we look at the software that could enable such services.

Start-ups push middleware products
A number of start-ups have emerged to tackle the issues involved with linking these divergent networks. BridgePort, Kineto, IBiS Telecom and LongBoard (mentioned here) all intend to bring products to market that enable fixed-mobile convergence.

These products reside in the core of the carrier network, and bridge mobile and IP networks. To link networks, these products typically use a roaming technology that extends a user's mobile-phone identity over an IP network, translating from the telecoms world's Signaling System 7 (SS7) on one end to SIP on the other. All the products are designed to extend a user's mobile identity to IP networks, so a user's phone number and session remain the same, regardless of location. These start-ups also focus on additional features, such as session persistence and single sign-on authentication.

Executives at BridgePort emphasise the benefits of a single subscriber identity. "Today's highly mobile professional has several different points of contact, a desk phone, a mobile phone and maybe a couple of e-mail addresses," says Sanjay Jhawar, BridgePort's senior vice president of marketing and business development. "With fixed-mobile convergence, not only do you converge the networks, but you also converge the points of contact for the individuals you serve. In certain verticals, such as healthcare, this is a very valuable service.

"A fixed-mobile solution also needs to extend services from one network to the other, such as enabling SMS (Short Messaging Service) on Wi-Fi," says Steven Shaw, director of marketing for Kineto Wireless. "Users need to have the same access to applications and the same user features as they had before, or they won't be satisfied."

However, the bridging technology is only one piece of the puzzle. Another must-have is the dual-mode handset that switches seamlessly between networks. "For broad handset support, the industry first needed an appropriate standard for fixed-mobile convergence," Shaw says.

This is where UMA comes in. It will be part of Release 6 of 3rd Generation Partnership Program, and as a result handset manufacturers now have specifications to build to. On the heels of these developments, ABI Research predicts that there will be more than 50 million dual-mode handsets worldwide by the end of 2009.

What's the benefit to IT?
The most immediate benefit to an IT staff will be cost. However, quantifying actual cost savings is something that carriers, vendors and even analysts seem reluctant to do. Although, the basic logic goes something like this: A large number of mobile calls placed within the corporation are actually intra-enterprise calls. With a converged service, those calls would be free. Mobile calls placed within a corporation but going to the outside world also would be less expensive going over the Internet than over the cellular network (Nortel has made the most extravagant claims for this sort of cost saving).

"Already you have large enterprises playing hardball with carriers," BridgePort's Jhawar says. "Certain large enterprises are telling the telcos that they will no longer pay for on-campus-to-on-campus calls." If this is true, it means that convergence ultimately will benefit the carrier - which in essence is able to extend its network without adding capacity.

"Basically, increased mobility equals increased productivity," Kineto's Shaw says. "The user experience of data applications on phones is also greatly improved when you have broadband."

"A converged solution is a more secure solution," Avaya's Lovasco says. "With convergence, enterprises are able to regain control of their mobile user base."

When will we see converged services?
That depends on what you mean by "converged." T-Mobile provides a dual-mode service, although it lacks session persistence. BridgePort and Kineto have both been in trials with carriers - BridgePort with Bell Canada and Kineto with AT&T Wireless. The Avaya/Proxim/Motorola offering is due out in the spring.

As for carrier offerings, timetables are still up in the air. "Actually, the cable operators may be the first movers in this space," Jhawar says. "Many are looking to partner with (mobile virtual network operators), as evidenced by the recent announcement between EarthLink Wireless and SK Telecom. Convergence is perfect for (mobile virtual network operators). They're not responsible for maintaining networks, so they are freer to focus on convergence and the benefits that come with it."

Vance is a freelance technology writer and president of Sandstorm Media. .