VoWLAN: The Wireless Voice Future is Here ... Almost - Page 2

 By Beth Cohen
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QoS (Quality of Service) 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. As Myers puts it, "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. 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.

Staffing and Operational Issues
Unless you were a tiny company that had an IT generalist, the data and telecom support staff have, until recently, not needed to learn each other's methodologies and equipment. The current trend is to merge the support functions and staff for more efficient operations, but there is still a time lag in training and operational efficiencies, as the staff learn the new equipment and procedures.

Hardware What Hardware?
Currently there are two main companies in the VoWLAN handset market, Vocera and SpectraLink. SpectraLink owns 75% of the total handset market and the majority of the health care market with systems in 1600 hospitals nationwide. Vocera is startup breaking into retail and health care. Because they were first to market, neither of these are standards based systems. Both Cisco and Symbol (the people who invented barcode scanners) have handsets as well. According to Chris Taylor, Symbol has recently dropped the VoWLAN line to focus on their core market. All the products suffer from short battery life and reliability problems. As PoE (Power over Ethernet), standards and cellphone technology is incorporated, expect to see a plethora of better handsets within the next few months.

Are We There Yet?
How is Chris Taylor doing with his VoWLAN system? He reports that they have had the beta system in place since January. They are planning a full rollout to completely replace the old "Companion" system by September. "The staff loves it. The voice quality is good and roaming is completely transparent. Just make sure all the vendors' equipment is compatible and integrated. That was the key to success for our installation."

Should you be seriously considering Voice over IP over wireless LAN solutions today? Well yes and no. Unless you are in the health care, manufacturing, or retail industries where the ROI is especially compelling, the technology is still not quite ready to be heard yet. With the maturing of both the VoIP and wireless technologies, on the surface merging the two emerging technologies might seem to be a terrific idea. However, security issues, poor quality equipment, and bandwidth prioritization considerations point to a technology that is still too immature for anybody to deploy unless they are ready to put up with the bleeding edge phase of the innovation curve. In the next 8 to 12 month there will be numerous new products that will be addressing these and other issues as many innovative technology companies work on solving the problems. Once the issues have been properly addressed and the standards settle down, VoWLAN with its potential to merge data, voice and mobility into one neat package, promises to be something that could transform how companies do business.

Beth Cohen is president of Luth Computer Specialists, Inc., a consulting practice specializing in IT infrastructure for smaller companies. She has been in the trenches supporting company IT infrastructure for over 20 years in different industries including manufacturing, architecture, construction, engineering, software, telecommunications, and research. She is available for consulting to help your company identify the right IT infrastructure to meet your business objectives.
This article was originally published on Jun 14, 2004
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