A huge amount has been written about convergence between Wi-Fi and cellular services in the last year, but absolutely nothing has been available. Now, a nearly-forgotten BT project has reappeared, with plans to offer a cellular phone enabled for voice over Wi-Fi.

However, this will do very little for convergence, because Bluephone will use Wi-Fi to meet the needs of the mobile phone industry, rather than use it to unleash the potential of merging the cell service with the Internet.

The context
During 2004 we heard a mass of conflicting stories about voice on Wi-Fi and convergence:

After all that, can you actually buy a converged system that roams calls between the cellular network and Wi-Fi? No. Not unless you are in Japan and buy a limited system from DoCoMo, that roams between DoCoMo's own network and a DoCoMo PBX in your office.

Cells and Wi-Fi fight like cat and dog
And why not? The reason is, there is an entrenched difference of opinion behind the two types of service.

At the most basic level, voice over Wi-Fi treats voice as just another kind of data. It runs voice over IP and uses SIP addresses to route calls across the Internet. This is anathema to the cell networks, who have no intention of allowing voice over IP. For them, data is a means to squeeze more revenue from reluctant customers, not a means to let customers get voice services for less money.

Voice over Wi-Fi devices expect to have control over what network they attach to. This is powerful for end-user devices (but potetntially risky - it is the basis of the "evil twin" attack, where a user unknowingly attaches to a bogus base station).

Cellular devices are different. They expect the network to control their attachment. If you have a 2G/3G device, for instance, the operator's network determines what base stations you are in range of, and decides which you will connect to.

So merging the two means merging two opposing worldviews. It's a continuation of the "Net-head" versus "Bell-head" debates that have always surrounded the Internet, in which the telcos' urge to put control at the centre always fights the Internet's tendency to let end-systems have control.

Could Bluephone crack it?
At first sight, it seemed like BT might (surprisingly for such a giant operator) sidestep these difficulties. It understands IP - it is diverting calls onto an advanced IP backbone. "The fixed domain is a long way ahead of the cellular operators, in terms of IP," says Dean Bubley of Disruptive Analysis. "Most fixed operators understand IP, and are more gung-ho about VoIP. I generally think Wi-Fi much better fit with wireline than wireless."

More than a year ago, we heard of a project - Project Bluephone - that sounds like a major step forward. Bluephone is a plan to combine a cellular phone with a local wireless base station.

Despite originally having an expected launch date of Spring 2003 (still embarassingly promised on BT's site at the time of writing), the project dropped out of sight. It's not exactly forgotten, but some observers have wondered out loud if it will actually ever appear.

Now it looks like Bluephone has revived, at least in terms of BT talking to the press. A BT executive briefed us on Bluephone last week, promising a launch "this spring", of a significantly changed and evolved Bluephone service.

One major change is that BT plans to move Bluephone to Wi-Fi (from the Bluetooth service it will launch). The dispapointing news is, the company has clarified the way it will combine cellular and local wireless. The merger is clearly on the cellular industry's terms, and not the kind of convergence we were hoping for.

How does Bluephone work?
The original idea for Bluephone was to have a normal cellphone which can send calls via a special Bluetooth base station when inside the house or office. BT chose Bluetooth for the job, because it supports cordless telephony, is less power-hungry than Wi-Fi, and is almost universally available in mobile phones.

Bluephone is a consumer service, and BT intends to deliver it on absolutely standard cellphones.

However, since the project was announced, Wi-Fi has been moving fast, and BT can see which way the wind is blowing. "In 2006, when Wi-Fi makes its way into standard mid-range phones, we will have a Wi-Fi version," says Ryan Jarvis, director of mobile products and partnerships at BT. Future versions will use WiMax, he says.

But, even when the Wi-Fi version arrives, this will not be the converged Wi-Fi/cell phone that we have been waiting for, because it will not do voice over IP, and it will not be a SIP phone.

Bluephone calls use the GSM network. When they transfer a call to use the Bluetooth link, they just transfer the first few yards of that call. The call stays under the control of the GSM network. All indications are that it will still be priced as a mobile call: Jarvis would not be drawn on pricing, but offered the possibility of "a discount" for calls using Bluephone.

Bluephone is mobile-centric
BT is using Bluephone to get back into the mobile world, having sold off O2. It is leasing capacity on Vodafone's network (under an MVNO deal), and taking on mobile industry thinking.

As Jarvis explains, Bluephone was delayed while the mobile industry set up UMA and other bodies. UMA's role is entirely to do with allowing the GSM network to "embrace and extend" unlicensed radio links. UMA lets operators slot in Wi-Fi, Bluetooth or whatever, as the first step in a connection ruled by the GSM network.

The FMCA - which Jarvis chairs - takes a higher level view: "It's the next level up," says Jarvis. With ten telco members, FMCA is looking at all means of convergence, including Wi-Fi and SIP. By contrast, he says, UMA is "a technology-specific body, aiming to put GSM over wireless".

A ray of hope
Users that want a mobile voice-on-Wi-Fi phone have a ray of hope, however. Vonage has promised to launch a Wi-Fi handset for its voice on broadband service. It isn't mobile, as it can't roam to the mobile network, but it will work at the ever-increasing number of Wi-Fi hotspots.

[Aside: Since this article was published, I have heard from Frank Bulk of Syracuse University, that you can already use Vonage wirelessly: simply sign up for a soft phone account at Vonage, buy a WISIP phone (read our review) and configure it according to Vonage's instructions]

Moves like that could push BT and the rest into making a better job of fixed/mobile convergence. At the moment, however, there is only divergence. Bluephone is a mobile phone exploiting unlicensed local connections but keeping IP at bay, while Vonage has a voice on IP phone that allows mobility to the patchy coverage of Wi-Fi.