VoWLAN: The Wireless Voice Future is Nearly Here

VoWLAN might be the chocolate and peanut butter of networking, but the convergence of VoIP and wireless freedom has its share of snags. Here's what you need to know.
Chris Taylor, telecommunications manager with the Metro Toronto Convention Centre, had a serious problem.

His mission critical Nortel ''Companion'' 900Mz phone system was no longer supported and he needed a replacement system double quick. With 2 million square feet of open exhibition space spread over two buildings, he needed a communications system that provided roaming and instant communications, an open flexible data network, and a minimum of wires.

A year ago, he started looking at wireless networking combined with VoIP (Voice over IP) or VoWLAN (Voice over IP over Wireless) as part of the total networking solution. As Taylor put it, ''My three goals were to provide wireless data networking for exhibitors, create a corporate profit center by selling services to the exhibitors, and meet employee data/telecommunications needs. The combination of VoIP and wireless networking fit the bill exactly.''

With 55 million lines and 15 percent of the voice market, VoIP is an established and rapidly maturing technology. It has been proven to be less expensive to install and maintain. The core equipment is comparable in cost to traditional voice, and it offers many more integration options.

Wireless technology also is rapidly maturing, so the next obvious step is to deploy a converged technology. Until a few months ago, the converged technology suffered from proprietary equipment, weak security, and a lack of scalable network management tools: It was not quite ready for prime time. All that has changed in the past year. The VoWLAN landscape is rapidly changing with evolving standards, new equipment, and finally some good management tools. Let us look at some of the issues that were plaguing VoWLAN and how the fledgling industry is successfully addressing them.

Approaching Technological Liftoff

According to Bob Myers, CTO and co-founder of Chantry Networks, a company that develops wireless network management systems, VoWLAN is growing rapidly in certain vertical industries like health care, hospitality, retail and manufacturing. Industries where the flexibility, combined voice and data requirements are so compelling that they are willing to forgo the current lack of handset hardware, network management tools and poorly addressed security, standards, and QoS (Quality of Service) issues.

Part of the problem is that wireless is a contention media -- the users share the available bandwidth -- so wireless always will have overhead issues and more complex management requirements. Another overlooked issue is how to determine good coverage. In an open field, coverage is easy to determine, but most IT people don't have the specialized knowledge required to plan an installation for a complex environment like a hospital, with all its attendant equipment and building structures.

Myers notes, ''Health care's transition to VoWLAN came about because they had widely deployed 802.11 so they were already comfortable with the technology. The hospitality and retail sectors both have a widely dispersed work force that needs to be in constant communication. Both industries were previously using the 900Mz Walkie-Talkie systems, so conversion to VoWLAN was a natural next step. Beyond those specific industries, uptake has been slow because of the perceived security issues and lake of management tools.''

Recently, there has been a major change in perception as companies discover the benefits of increased flexibility, the improved security standards, and the always popular, substantially lower operational costs.

Wireless Network Management

A critical component to the success of VoWLAN is sophisticated wireless network management tools. As Myers puts it, ''Unlike all previous computer technology, wireless networking, wireless came back into the enterprise from the SOHO and home markets. With a three node network, you don't need management tools.''

When rolling out enterprise-wide wireless, especially VoIP, the need for prioritized data streams, transparent access point handoffs, and seamless security are essential. Chantry offers a management package that is designed to specifically address these issues. Other companies, like Avaya and Cisco who are heavily invested in developing this market, are also working to develop new tools.

QoS and Reliability

Wireless service quality is technologically a step 10 years backwards. For data packet delivery, companies are willing to trade mobility and reduced costs for reliability, but voice packets are more sensitive to perceptible service degradation.

''You really need to have a max of 150ms to make sure users are not bothered by QoS issues when you are using a VoIP system,'' says Meyers. ''Cellular has gotten people used to a lower QoS compared to traditional voice, but not entirely.''

To make matters worse, the WME (Wireless Multimedia Extensions) 802.11e wireless QoS standard will not be ratified until the end of 2004 or early 2005. Most wireless equipment has not yet incorporated any QoS because they are waiting for the emerging standards. Because this is such a critical piece for a successful VoWLAN deployment, some companies are implementing a subset of 802.11e.

Another gotcha is that while 802.11b officially delivers 11MB with QoS, the actual useable bandwidth is really closer to 6MB. Remember that 6MB is shared by anyone on the access point. VoIP has a tendency to have small packets with a large overhead. With 10 to 15 VoIP users you are quickly down to unacceptable modem-level data rates. The reality is that with most wireless equipment, planners should expect 6-7 voice calls maximum per channel. With Chandra's priority queuing and predictive handoffs, they can support up to 15 voice streams in addition to a small amount of data traffic. By limiting the number of voice calls on a single access point, the software can maintain the required QoS.


Wireless security is finally improving with the newer WPA and WPA2 standards, but these emerging standards have not been fully adopted into the VoWLAN equipment yet. 802.11r is a brand new IEEE taskforce created specifically to address VoWLAN security issues. Expect to see handsets incorporating the improved security standards in 6 to 8 months, and new standards in this area in a year or so.

According to Myers, part of the problem is the need to re-authenticate every time users move between access points. Session switching can cause unacceptably high delays (up to 500ms) or dropped calls. Obviously the re-authentication process is in direct conflict with the QoS requirements of maintaining the call data stream. Chantry has incorporated a virtual network service that preloads the VoIP session security at the backend as the user roams the network so the call session is transparently switched to the new access point minimizing signal delay.

This article was first published on crossnodes.com. To read the full article, click here.

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