Roadmap to Fixed-Mobile Convergence

Once upon a time, when you wanted to make a phone call you had to find a telephone. Now the cell phone network finds us.

That’s where Internet connectivity is going in the not-too-distant future, says Peter Thornycroft, Vo-Fi Solutions Product Manager at Sunnyvale, CA-based enterprise networking company Aruba Networks.

“It’s a mobility-centric view,” says Thornycroft, explaining Aruba’s vision of the new mobile enterprise. “What we do is decide who you are and what device you’re on and we follow you around.”

Thornycroft knows what he’s talking about. The three-year old privately held company currently has about 3,000 customers; including what the company believes to be two of world’s largest mobile wireless networks: Microsoft, whose network covers 70 buildings world-wide, and Ohio State University with 10,000 access points. Aruba also provides the infrastructure for Verizon’s Managed Wireless LAN service.

Thornycroft is a big fan of dual-mode phones that have come on the market in recent months. “We’re seeing a new generation of WiFi/cell phones,” he says. “We think the simplest model is a single number and a single device.”

But carrier networks aren’t ready yet to support the capacities of these devices.

“What’s been happening recently is that customers have been calling us and telling us ‘I’ve been using this phone and I’d like it to this and this,'” he says. “But the cellular carriers haven’t considered what you need to do when the fixed-mobile network hits the corporate environment.”

But Aruba has been thinking about it and has boiled it down to two approaches.

The first is a PBX-centric approach. In this model, the desk phone with a DID number becomes the single number that reaches you wherever you are. The PBX decides where the phone is – in the WiFi or cell universe – and directs the call appropriately.

The second approach is – as you might guess – carrier-centric. In this model the carrier makes the decision about where the phone is and routes the call. This approach offers carriers an entrĂ©e into the enterprise with managed services.

“We see a huge number of customers that haven’t been touched by WiFi,” Thornycroft reports. “A lot are deterred by the unknowns. They don’t know the costs of deployment, they don’t have the RF expertise, they don’t have the help desk expertise. That’s why we’re keen to see service providers take on those tasks. That’s when we see the market opening up.”

While it sounds pretty straightforward – decide where the phone is and send the call there – there are some significant icebergs below the surface.

“One of the key questions is deciding when the phone is moving out of WiFi range,” says Thornycroft. “You can quickly go from a good signal to no signal. With WiFi you need to be concerned as you leave access points – you need to make decisions pretty accurately and pretty quickly.”

Which brings up the – no pun intended – thorny question of the call handover between WiFi and cell networks. Answers remain elusive. Although several vendors claim to have solutions – Bridgeport Networks, Global IP Sound, Kineto Networks, and Hellosoft just to name a few – none are in production.

“There’s a lot of debate about how valuable it is to add complexity to handle call handover,” Thornycroft says. The biggest market for fixed-mobile phones is Japan, where handoff is done manually by the caller. “Until we get a few more [devices] out there and get some user behavior data, we won’t know.”

Thornycroft sees a five-step roadmap to the “holy grail” of complete fixed-mobile convergence.

Step one was 2005 where the greatest challenge was getting the phones to work.

In 2006, we’re at step two: wireless LAN scalability to thousands and tens of thousands of access points. For example, NTT Data in Japan (another Aruba customer) is upgrading to support 8,000 devices. Each employee will have a PDA and a dual mode phone.

Thornycroft sees handover-helper software enabling premises-based fixed-mobile convergence in 2007 – step three. He also foresees this happening with off-the-shelf phones and PBX vendors offering APIs for their systems. “If you’re an Avaya customer, you’ll want Avaya features on your mobile implementation as well.”

The next step happens when carriers integrate architecture that lets them offer fixed-mobile services over a wireless LAN. “You can then sell the same services sold to residential customers to small business,” Thornycroft explains.

The final step is a seamless network – everything is IP – which Thornycroft sees happening in 2008.

“We think WiFi will be a big part of the architecture,” he says. In the meantime, “we’re trying to be a good citizen and accommodate all these architectures for fixed-mobile convergence.”


  1. sshaw says:


    I’m with Kineto, one of the companies mentioned in your FMC article. We are involved in the “carrier” FMC side of what Peter from Aruba was discussing.

    Our solution is based on a standard known as UMA (, or Unlicensed Mobile Access. It’s a specification for operators to deliver mobile services over Wi-Fi access networks.

    Anyhow, it was mentioned that there aren’t any carrier solutions in production from Kineto. I wanted to point out that several operators around the world have UMA services deployed, include Orange in France, UK and Netherlands, Telia in Denmark, Telecom Italia, British Telecom and T-Mobile here in the US.

    Dual mode phones and seamless mobility between GSM and Wi-Fi is coming a lot faster than many people think, and UMA is the technology driving it. I also think Aruba’s technology will be key for bringing UMA solutions into the enterprise.

    Thanks for letting me clarify.