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Ian Schenkel, Managing Director EMEA of AirMagnet discusses key considerations when implementing a voice over wireless LAN
Voice over Wireless LAN (alternately known as VoWLAN or VoFi) is currently one of the hottest topics among CIOs and enterprise technology circles. This shouldn’t be surprising given that VoFi straddles two of the most successful enterprise technology trends of the past several years - the rise of 802.11-based wireless LANs and voice-over- IP (VoIP). However, VoFi isn’t simply riding the coat tails of its forbears. Wireless voice deployments are surging because VoFi is able to resolve real problems more effectively, and at a lower cost, than those options being used today.
VoFi is able to leverage the local network that the enterprise can control which means that organisations have direct control over the quality of the access network. This would be impossible in a mobile environment. For example, working in a multi-story building can subject users to poor call quality for a variety of reasons, including working near an elevator shaft. Using a mobile network means there is very little that can be done to improve coverage other than move to another location. In a VoFi deployment additional coverage and capacity can be
supplied simply by adding relatively low-cost access points. In addition a wireless LAN offers much better performance to end-users who increasingly need to converge voice and data. Basically, a 54 Mbps WLAN connection has a lot more to offer an enduser than a broadband cellular connection with less than 1 Mbps.
VoFi also provides considerable cost savings by pushing even more enterprise voice traffic to the enterprise IP network. The cost benefits of using the enterprise IP network instead of a traditional carrier is at the heart of VoIP’s widespread adoption and success on the wired side of the network. For the same reasons, companies are now trying to drive as many voice calls as possible to the IP network, including calls made from a desk phone. This allows companies to control costs, ensure quality and derive additional value from the existing network infrastructure.
While VoFi has some very obvious and compelling advantages, it is important that CIOs and network managers don’t get carried away by the hype, and instead ensure they fully understand the technical and operational requirements of a successful VoFi deployment. Voice is a fundamentally different technical animal than data; any variance in the network can lead to poor call quality, dropped calls and one-way audio. In a data deployment, small fluctuations in network quality are unlikely to be noticed by end-users. This leads to the single most common pitfall for voice deployments today – when an enterprise simply adds voice to a wireless LAN originally designed for data. Inevitably this approach leads to poor results. For voice to work reliably an enterprise must design, deploy and manage the WLAN with VoFi in mind.
A comprehensive site survey and network plan is an absolute must for any VoFi deployment. It is almost impossible to expect a reliable end-user experience without taking the time to design the network for the needs of voice. A standard rule of thumb is to ensure that all areas are covered by at least two wireless access points with a suitable signal (typically a minimum signal of between -64 to -67 dBm). Special attention should also be paid to evaluating the quality of the physical RF environment as well as the overall capacity needed to support both voice and data applications at peak traffic times. Staff should also identify and implement a Quality of Service (QoS) strategy to provide voice traffic with real-time priority over data. This is of course, not an all-inclusive list, but rather an important reminder that there are many things to think about and plan for before voice is rolled out.
In addition to this planning, companies should also be prepared to overcome voice problems as and when they arise. This means taking the time to establish a methodology and toolkit for troubleshooting voice. When an end-user experiences a problem with VoFi there are several potential sources of the problem, it could be rooted in the user’s phone, in the RF environment, a problem with the WLAN itself or there could be a QoS problem caused by the competition of voice and data on the network. Once identified, problems can be easy to resolve, but it is critical that technical staff have the tools and understanding to quickly diagnose these problems without having to go to the phone or WLAN vendor. Regardless of the tool of choice, it is important that staff are prepared for problems and that a policy is agreed regarding problem resolution.