This year, voice over wireless LAN has been a fashionable item for wireless LAN vendors to offer to their enterprise customers and prospects, but so far there is little evidence of voice over WLAN making any dent in the use of mobile phones or wired phone systems in the office.

Instead, like the basic wireless LAN itself (and like the chic idea of wearable computer devices, voice is being taken up first in the more prosaic world of the warehouse, and US-based fast-food outlet Dunkin' Donuts is at the forefront.

The application is not voice communication between people, but voice input to a warehouse "picking" system, but the voice traffic is carried over the WLAN. Voice input lets the workers operate hands-free, while the WLAN unties them from a specific location for data input.

Voice input
Such systems learn the sound of a worker's voice through speech recognition, then instruct that worker - who wears a portable computer and wireless headset - as to which items to pick from the warehouse inventory and where to deposit them for shipment. A highly accurate voice-based picking system can greatly speed warehouse productivity, compared with workers having to print and consult paper instructions.

In the Dunkin' Donuts warehouse in Swedesboro, New Jersey, the workers drive carts or other small vehicles, so hands-free voice systems contribute to safety in picking operations.

Using 802.11a and 802.11b, but not 802.11g
Dunkin' Donuts has been piloting Airespace wireless to support the Voxware VoiceLogistics picking system. The donut chain has been trying out six Airespace multimode 802.11a/b/g lightweight access points and an Airespace 4000 WLAN switch, which it uses to segregate its traffic for performance. It expects to bring the system into production use soon.

The company runs Voxware traffic on the 802.11b 2.4 GHz frequencies, with data on the 802.11a 5 GHz frequencies. For now, it has disabled 802.11g to avoid interference with 802.11b traffic, says Boris Shubin, director of IT in the Dunkin' Donuts Swedesboro site.

The slower 802.11b (11 Mbit/sec) is used instead of 802.11g (54M bit/sec) only because Voxware doesn't yet work with the higher-speed network.

Shubin says the Airespace switch dictates prioritisation for voice traffic according to the frequency band, so all traffic from the "Voxware WLAN" (802.11b) is prioritised highest, while the "data WLAN" (802.11a) has lowest priority.

"The switch dictates prioritisation at the access point level as well," Shubin explains. "It also affects what gets sent over the wire - from the access points to the switch and on to the Voxware application server - and what gets sent out to the access points first."

Low admin costs
Shubin says his organisation settled on using Airespace because it is the "closest thing I've seen to zero administration in an environment where 90 percent or more of our recurring total cost of ownership is support."

For example, says Shubin, the access points will dynamically change channels if one experiences interference. And the lightweight access point architecture means Shubin makes all configuration and management changes once, to the switch, not to multiple access points.

"I'm thin on IT resources here," he says. "So this is helpful."