Trapeze Networks has teamed up with a mobility appliance startup to demonstrate handoffs between cellular and Wi-Fi networks.

Trapeze said its wireless LANs can interoperate with appliances from DiVitas Networks to let any Microsoft Windows Mobile 5.0 handset go seamlessly from a cellular to a Wi-Fi network.

With DiVitas client software on the handset, a user talking on the phone could move from one network to the other and back without any involvement by the cellular service provider, said Dan Simone, chief technology officer at Trapeze.

The companies tested handsets offered by Cingular Wireless and Verizon Wireless, Simone said. The demonstration involved currently available Trapeze gear and products from DiVitas that are in beta testing. The companies are only technology partners at this time, said Richard Watson, director of product management at DiVitas.

Handset makers are starting to introduce dual-mode handsets with both cellular and Wi-Fi capability. They can use VOIP (voice over Internet Protocol) to take advantage of the relatively low cost and high good coverage of Wi-Fi networks within homes and businesses. Infrastructure vendors are developing the technology to make that work, but handing off between the two types of networks has been a challenge.

DiVitas, in Mountain View, California, is developing enterprise appliances and client software for mobility management that should go on sale around the end of the second quarter, Watson said.

After starting with Windows Mobile 5.0 client, the company plans to introduce software for Symbian and Linux handsets in the third quarter, he said. The appliance and clients are expected to cost enterprises about US$100 to $200 per user, he said.

Being able to hand cellular calls off to an enterprise Wi-Fi network could lower an organisation's costs and in some cases offer other benefits, according to analyst Peter Jarich, of Current Analysis. It's not uncommon in a large enterprise for two employees to end up on a cell call with each other even though they're both in the office, he said. Offloading those calls to the company-owned data network, or even going through the office PBX (private branch exchange) to a long-distance service with volume discounts, could slash the cost.

In some enterprises, linking dual-mode phones with an IP PBX could allow the use of special features such as four-digit extension dialling, Jarich added. Wi-Fi capability could also improve mobile phone coverage inside the office - as long as the enterprise implements its Wi-Fi network well, he said.

Dual-mode handsets shown off at the CTIA Wireless trade show earlier this month are smaller and cooler than previous designs, and availability and choice are set to grow, he added.

"We'll see it ramp up this year and into next year," Jarich said.

Also Monday, Trapeze introduced two wireless LAN switches, the MX-200 for data centres and the MX-216 for direct connection to access points. They support more clients than earlier Trapeze switches for lower per-user cost and are priced at $9,595 and $9,995, respectively.