Prepare your network for voice over wireless LAN

Voice over wireless LAN technology is maturing. Is your WLAN - and the rest of your network - ready for this new form of traffic? Now's the time to get ready!

With voice over wireless LAN (VoWLAN) set to explode in a few years, network professionals must make sure their wireless networks are ready.

Frost & Sullivan recently predicted that the North American market for enterprise VoWLAN devices will grow from $110.5 million in 2007 to $2.15 billion in 2014. This includes dual-mode cellular and Wi-Fi mobile phones, as well as single-mode Wi-Fi desk phones and specialized paging and messaging devices that have become popular in the medical industry.

"Dual-mode VoWLAN devices are expected to emerge in the market noticeably in 2009 and penetrate considerably the enterprise space in the coming two to three years, and to finally surpass the market of single-mode devices in 2012," said Alaa Saayed, a research analyst at Frost & Sullivan.

There are very clear cost benefits associated with VoWLAN, according to Chris Silva, an analyst at Forrester Research Inc.

"We see more and more users making use of their mobile phone when they are sitting at their desks," Silva said. "They're using their BlackBerry while they're sitting next to a relatively expensive piece of equipment, the desk phone. So in some organizations it's possible that to support that behavior, enterprises will explore dual-mode offerings where PBX functionality, five-digit dialing and conferencing are all integrated with the mobile OS … and those devices will make calls that go over Wi-Fi. So now you're adapting infrastructure to support the behavior that's already taking place -- and in the process, reducing the cost of cellular calls going out every month."

The problem with this trend is that the majority of wireless LANs in enterprises today are not deployed with the depth of coverage that would truly support seamless voice, Silva said. In most so-called "carpeted enterprise" settings, wireless LAN technology is often laid out in a way that provides a few areas of connectivity for data. Often access points are deployed in some parts of a building but not in others.

"All this comes down to more access points being laid out and being laid out in a thoughtful manner -- not turning them on and laying them out ad hoc as different groups or different physical areas of the organization demand connectivity," Silva said.

Paul Debeasi, a senior analyst at Burton Group, said organizations must also consider density when building out the WLAN for voice.

"You might have good coverage, but there may be areas of buildings where you have high call volumes -- and just like network operators have to worry about network arrival times and call times, you do too," he said. "If people are on the phone for long periods of time and there's a high density of calls, you have got to make sure you've got sufficient coverage and density to support those calls"

Silva said enterprises are starting to move forward with broader wireless LAN deployments. By 2010 or 2011, about 50% of enterprises will be ready to support VoWLAN, he said. Companies that are exploring wireless LAN for the first time or are expanding their existing deployments should be thinking about supporting voice, even if they are a couple years away from using it. They should demand that their prospective WLAN vendors generate coverage maps that support data and voice.

"So if you deploy for voice even before you use it, it's likely your data network will improve and you won't have to retrofit when you do make the move to voice," he said. "Organizations that roll out a Wi-Fi network might have a hard time making the ROI case for rolling it out deeper across the organization. Voice over Wi-Fi has the potential to give those organizations, especially the IT operations group, the ability to go to the CIO or CFO and say, 'Look, if we deploy more wireless access points it might cost us another $50,000. But over the course of the next year our cellular usage savings is going to come back to us in the form of $75,000 or $100,000.'"

In addition to building sufficient infrastructure, networking professionals will also have to manage their networks carefully when they are called on to support voice.

"Management tools become critical. You need to have real-time ability to diagnose problems," Debeasi said. "When you have problems with voice over wireless LAN, it's an urgent problem. It needs to be solved right away. Whereas interference on a wireless LAN that is just doing email -- people might not even notice"

Debeasi said organizations need good visibility into the physical layer, including dedicated sensors that can monitor for rogue access points or legitimate access points that can create interference. He said networking pros must also look past the physical layer and do real-time packet monitoring of packets, too, with product vendors like AirMagnet Inc. and WildPackets Inc. AirMagnet, for instance, has a VoWLAN specific that can perform specialized analysis of voice packets.

"When it comes to wireless voice, you want to make sure your wired infrastructure has quality of service and that you have the tools to monitor that," Debeasi added.

"The last thing I always tell people, because they always forget this, is make sure you spend time to provide training for your staff to both use these tools as well as be trained on wireless LAN technology and even consider getting some of your professionals certified. CWNP, for instance.."

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