I got to wondering recently how Anthony Marano Co., a 57-year-old fruits and vegetables wholesaler in Chicago, was continuing to meet its extreme need for dual-mode Wi-Fi-to-cellular voice roaming. The company has been a longtime test site for a prototype fixed-mobile convergence (FMC) system created in 2003 by partners Avaya, Motorola and Proxim that never shipped commercially.

I caught up with the wholesaler’s IT director, Chris Nowak, last week. Thankfully, according to Nowak, Avaya and Motorola have continued to support Anthony Marano’s nearly three-year-old pilot, which the company treats as its production voice system. The system was put together for the wholesaler initially by Avaya, which intended to commercially resell Proxim’s lightweight access points, Motorola’s CN620 handset with 802.11a/GSM connectivity, and Motorola’s Wireless Services Manager Wi-Fi-to-cellular handoff appliance.

But since all of these FMC elements have been discontinued, Anthony Marano is on the prowl for an alternative solution. It is currently testing T-Mobile Unlicensed Mobile Access (UMA) services with BlackBerry smart phones and single-channel wireless LAN systems from Extricom and Meru Networks (Learn more about Enterprise Wireless LAN products from our Enterprise Wireless LAN Buyer's Guide).

UMA is a service offered by T-Mobile that automatically puts dual-mode handset users on Wi-Fi for voice calling indoors and on GSM for voice calling outdoors. The UMA service relies on a UMA gateway made by Kineto Wireless to seamlessly make the transition on behalf of users, who get better voice quality and save cellular minutes when in the office or at home.

About 80% of Anthony Marano’s business volume involves quickly filling grocery store orders, often within a single day. So the company can't tolerate extensive voice mails, callbacks and desktop-bound e-mail. Most of its employees are mobile and use the FMC system for single-number phone reach and seamless Wi-Fi-to-GSM roaming.

With the Motorola-Proxim-Avaya system, says Nowak, mobility among access points is fine as long as the user remains on a new session. However, if the user attempts to generate or receive a call while actually moving, the system can’t figure out which AP the user is on and the call dies. With the Extricom and Meru WLANs, this problem goes away, Nowak says.

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.