Is wireless [Wi-Fi-based] VoIP worth the bother?

From Network World -

Per the article, the answer for enterprise deployment is generally negative. However, recent trends provide hope.

Morever, successful deployments though still rare at this time, such as Osaka Gas in Japan, provide compelling proof of VoIP's viability. The utility used Meru Networks’ USD10M WLAN infrastructure to support 6,000 mobile phones that were equipped with cellular and Wi-Fi network interfaces.

The reluctance to embrace large-scale wireless VoIP isn’t suprising. Enterprisewide wireline VoIP deployments have only fairly recently found traction, and many of these have been angst-ridden. To be fair, often the angst is created by specific issues or problems at a given enterprise site.

But using a wireless connection in place of a wire adds lots of complexities, solutions to which are only slowly maturing. Access points have to be pervasively distributed to support voice traffic, while radio interference can easily affect voice quality or call sessions. Wireless eavesdropping on unsecured VoIP sessions is another worry for enterprise managers.

And it’s difficult to pinpoint savings since corporate IT doesn't have a good handle on actual spending since some of the equipment have other functions. Thus it is often just expensed, making it difficult to make a case for savings and therefore to make a case for investing in VoIP over WLAN.

Over the course of three months WLAN switches and access points from Aruba Wireless Networks, Chantry Networks (now Siemens), Cisco and Colubris Networks in terms of audio quality QoS enforcement, roaming capabilities, and system features were tested. Among the findings:

* With QoS enforcement turned on, and with only voice traffic on the net, calls nearly matched toll-quality audio.
* With even a small amount of data traffic, dropped calls became common and audio quality was poor, even with QoS still enabled.
* Roaming from one access point to another either failed or took so long, from 0.5 to 10 seconds, that calls dropped.

Those findings reflect some of the experience at Dartmouth College, which deployed a limited VoIP system on its pervasive Aruba-based campus WLAN four years ago. Initially, some college staff used the wearable mobile VoIP phone from Vocera. There were some problems with roaming, according to David Bucciero, Dartmouth director of technical services, who despite these teething pains is one who says wireless VoIP is worth the hassle.

More recently, the college has added just under 100 Cisco 7920 wireless VoIP handsets which “were flawless,” though latency was an issue early in the deployment. Reducing those delays has been an ongoing tuning process.

Things have changed in two years, including the advent of the 802.11e QoS standard, augmented by continued proprietary QoS tweaks, and faster handoffs between access points.

But the real change has been the growing interest in, and products for, shifting call sessions automatically between cellular and Wi-Fi. At the enterprise level, this convergence entails an IP PBX, usually a SIP server, the WLAN infrastructure, new specialized servers from start-ups like Divitas and established players like Siemens, and accompanying client code running on so-called dual-mode handsets.

Dartmouth is doing exactly this, running a pilot test with the Nokia E61i which uses SIP to talk to the Cisco CallManager IP PBX.

“Cellular and Wi-Fi convergence is the real pull for VoIP over wireless LANS,” says Farpoint’s Mathias. “Once that [convergence] happens, then we can converge dialing directories, voice mail, other services, and have one phone that works everywhere.”