As part of a technology trial, about 50 workers at Anthony Marano, a fruit and produce distributor in Chicago, for the past 18 months have been using dual-mode phones made by Motorola. Chris Nowak, the distributor's IT director, said the phones have provided "substantial productivity gains" by letting users roam throughout the company's WLAN-equipped warehouse and continue talking on a cellular network if they go outside to examine a delivery truck.

Nowak isn't fully satisfied with the current dual-mode phones, though. He said he'd like to see a model that has a better display and is less expensive so he could give the phones to more users.

Motorola is working on a new dual-mode handset for customers such as Marano, said Kevin Goulet, director of product management at the vendor's enterprise mobility solutions group. But, he added, Motorola has learned from trials at Marano and other sites that most workers don't need dual-mode capabilities and would prefer handhelds supporting data and voice for WLAN use only.

At least a dozen dual-mode phones have been introduced by vendors. But the big question for potential users is how to provide security for handoffs from WLANs to cellular and back again, especially when public Wi-Fi hot spots are involved, analysts said.

The Boeing Co. is a case in point. The aircraft maker has made a major commitment to WLAN technology for more than four years and currently has about 3,000 access points installed in plants and offices in 48 states, said Allen Ballinger, senior manager of distributed networks integration at Boeing. The highest concentrations of access points are on manufacturing floors, where pulling Ethernet cable into cramped locations would be impractical, Ballinger said.

But Cliff Naughton, Boeing's director of network services, said the company is "very security-conscious," which governs how it will extend the uses of its WLANs. With dual-mode phones, a wireless carrier would have to support roaming onto corporate networks and vice versa, which is "extremely complicated," Naughton said. "It gets kind of onerous. We will not be fielding production applications until we feel confident."

In the near term, adding voice over Wi-Fi by itself "is more viable," said Doug Hill, chief network architect and an associate technical fellow at Boeing. Even so, he added, some strict rules will need to be applied to keep voice quality high, especially with so many WLAN users. He also cited concerns that transmissions from radio frequency identification tags on a separate network might interfere with Wi-Fi voice calls.

As for expanding wireless bandwidth with 802.11n, Hill said Boeing isn't interested in installing thousands of new access points until well after 2008. "It's a lot of hardware change, and not something we're fired up about," he said.

Naughton said Boeing has talked with vendors about where it might be able to take advantage of WiMax and ZigBee, an emerging wireless technology for monitoring and controlling the temperature, lighting and security of buildings. But he said it likely will be "quite a long time" before Boeing is interested in putting ZigBee-based capabilities into buildings, partly because the company is consolidating its manufacturing and office space, not expanding it.

Paul DeBeasi, a Burton Group analyst, said that with the addition of 802.11n and other standards being developed for functions such as roaming and wireless network management, "Wi-Fi will be really reliable, predictable and high performance." It's hard to forecast, though, when those standards will be adopted by users, he added.

Gartner analyst Philip Redman predicted that 802.11n-based technology won't be widely installed until 2012, even if the IEEE meets its current schedule for approving the proposed standard.

And Bob Egan, an analyst at TowerGroup, said he thinks security concerns will continue to haunt Wi-Fi networks and limit their growth, particularly among large companies. "WLANs have had a very hype-driven ramp-up in homes, hot spots and municipal networks, and only certain parts of the business," Egan said.

At some companies, WLANs have become so commonplace that many workers never need to use wired connections anymore. For example, about 5,000 workers at Intel's Jones Farm office campus in Oregon rely on a WLAN "for mission-critical uses and use it as their primary network," said Brian Tucker, Intel's mobile marketing manager. "The majority do fine on wireless."