Chicago fruits and vegetables distributor Anthony Marano Company has settled on a hybrid fixed-mobile convergence (FMC) configuration to meet its intensive wireless voice and inter-network roaming requirements. It has installed a CPE-based solution and also subscribes to a carrier FMC service to get the job done.

The fresh-produce distributor is using a Session Initiation Protocol (SIP)-based RoamAnywhere Mobility Router from startup Agito Networks and Nokia dual-mode smartphones to serve the company’s phone-centric, highly mobile sales force of 50. Meanwhile, an Unlicensed Mobile Access (UMA) service from T-Mobile and dual-mode BlackBerries serve administrative staff. UMA is an FMC technology that tunnels GSM calls through wireless LANs.

Both approaches enable calls in progress to transition back and forth between the company’s 80-access point (AP) Meru Networks voice-optimized indoor Wi-Fi network and the T-Mobile GSM cellular network. And both extend the company’s Avaya PBX features and four-digit dialing (Compare IP-PBX products).

Before discovering Agito, Anthony Marano tested T-Mobile’s UMA service alone to serve all employees. The service works well for personnel with average phone use and offers unmatched flexibility for Wi-Fi roaming to homes and other venues, says IT director Chris Nowak. But for multitasking, just-in-time-oriented sales staff, the UMA service “wasn’t fast enough.”

A UMA-enabled phone connects to Wi-Fi, then a call is routed over the Internet to T-Mobile’s central office, then back to the company’s PBX, which then routes the PBX’s internal four digits to the UMA-enabled handset. The process requires about 20 seconds for call completion, Nowak says.

This is OK for typical users but the latency “drove the sales staff batty,” he says. And if the user transferred and forwarded calls, the latency had a cascading, cumulative effect on call setup time, he says, incurring another 20 seconds each step of the way. Nowak explains that a missed call could mean thousands of dollars lost when a grocer or restaurant gets frustrated and calls another supplier.

“Using SIP for direct wireless connections to the PBX has satisfied users much better” with instantaneous call setups, Nowak says.

The recently installed Meru WLAN runs on a single channel to eliminate co-channel interference, says Nowak, and the configuration maps all APs into a single “virtual cell” with a single common MAC address. This eliminates AP-to-AP call handoffs so users can place and receive calls when literally in motion, which they couldn’t do before, he says.

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