A new technology start-up promises to make voice on Wi-Fi more practical by letting a single handset roam between office wireless networks and public cellphone services - using a single handset. The prospect, of saving money by using "free" in-building Wi-Fi is enticing, (and has been proposed as a major driver for office Wi-Fi)but those already in the field agree the idea still faces difficulties.

Longboard showed OnePhone, an application that runs on handsets and provides "sort-of" Wi-Fi to cellphone roaming, at this week's Voice on the Net (VON) conference in Santa Clara. It's currently aimed at the healthcare market (since Wi-Fi is allowed in hospitals but cellphones generally aren't) but the company expects a European carrier to pick it up by the end of 2004.

The application (described here) uses Wi-Fi or Bluetooth in the office, routing calls to a central server connected to the office phone service, and "fades across" to cellular when necessary. As the Wi-Fi signal strength goes away at the edge of a WLAN, it dials a cellular call and the user speaks on both for a time.

The company is selling this as a service for carriers, rather than one the enterprise would put in for itself. As such it is similar to BT's promised Bluephoneservice, which uses Bluetooth for the in-office part of the system. Longboard believes that rather than reduce the mobile carriers' revenues, by allowing some calls to go over the office WLAN, it will increase overall takings. It wants handset makers to put OnePhone on their products so carriers can offer the service.

As well as OnePhone enabled handsets, the customer would have to have a server, called the Longboard Multimedia Application Platform (LMAP), which includes software to support SIP connections and an ENUM server to convert from Internet addresses to telephone numbers.

LMAP can support up to 100,000 users, at a cost of $30 to $60 per subscriber,
Longboard's director or marketing, David Schwartz, told eWeek. It will take about half a second to create a call, he said.

Longboard is already available on some handsets including the HTC Himalaya and Andes. This is better known in the UK as O2's XDA, which might be a hint as to which "major European network" the company expects to do a deal with, or it might not.
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Despite Longboard's optimism, and recent announcements, such as Nortel's claim to have saved $22 million on a $6 million VoIP investment, there was plenty of uncertainty at VON about how mature and practical voice on WLAN is: "The handoff is good enough for data but it's not good enough for voice," said Alain Mouttham, chief executive of SIPquest.

Service providers don't yet support the same QoS scheme, said Bob Jordan, vice president of marketing for Strix Systems Inc: "This cries out for a VoIP forum," he said. Such a body might also get involved in efforts to make Wi-Fi handovers fast enough for uninterrupted voice.

Beyond the QoS problems, each access point can handle a limited number of voice calls before it gets overloaded and quality suffers, however at 30 calls per access point (ie within a radius of 100 feet) this should be adequate said Ujjal Kohli, chief executive of Meru Networks.

Adding Wi-Fi to existing cellphones will take a bit longer, but will probably be better than using devices designed as Wi-Fi phones. For one thing it will allow users to continue with one phone that they are familiar with.

Wi-Fi phones tend to have poor battery life and often lack sleeper mode. They also tend to be so much more expensive than cellphones, that any effort to use them to save money is doomed according to some vendors.

Despite all this, even the sceptics say that customers should be buying into the technology now, though their motives may not be the best: "Please don't wait," said Mouttham. "We need the money."

Tim Greene of Network World Fusion contributed to this report