Setting up a wireless LAN or Wi-Fi network involves a certain amount of radio frequency (RF) voodoo.
Engineers/designers have to get an accurate sense of how many access points (APs) point are needed and where they should be located for optimum performance and minimum interference. (APs are the wall- or ceiling-mounted base station units connected to the wired network that actually make the wireless (i.e., radio) connections with Wi-Fi clients.)
One of the most popular tools for doing this pre-installation audit work is the software-based Survey application from AirMagnet Inc., which installs on a laptop or tablet PC and is thus totally portable. (Survey can be used post-installation as well, and for ongoing optimization.)
If setting up a Wi-Fi data network involves RF voodoo, deploying voice over Wi-Fi is voodoo doubled in spades.
Density and physical placement of APs become trickier and more critical for maintaining signal strength requirements while concurrently optimizing roaming (handoff) conditions. Too few APs can mean insufficient bandwidth or signal strength, too many can create handoff ‘confusion,’ where a phone switches aimlessly back and forth between available connections, causing latency or outright dropped calls.
Well, AirMagnet has answers for these voice-centric problems, too, not just for Wi-Fi data nets.
They’ve had a specialist tool—VoFi Analyzer—for some time (we’ll come back to this). But yesterday the Sunnyvale, Calif.- based company announced a new feature in Survey, especially for voice over Wi-Fi deployments. AirMagnet Survey product manager Dilip Advani told us all about it.
“What we have done is we created built-in profiles for different phone vendors—starting with the Cisco 7920 and the 7921 phones. So all the user needs to do is go to that screen, click on the profile; then we will tell you if the network meets, in this case, Cisco-recommended guidelines for a voice network.”
“It’s a one-click option,” Advani continued. “You just click on the profile and we tell you if are you ready for a Cisco voice deployment. Maybe you need more APs to be deployed, maybe APs need to be moved; we will give you all that information within that one screen.”
The Cisco profiles are just the first of many. AirMagnet is currently developing profiles for phones from other vendors, as well. But the feature can be used for any Wi-Fi enabled phone today.
“If you’re using [Polycom’s] SpectraLink phones, and you have their deployment guide,” Advani explained, “you just go to the application and plug in all those values for signal strength, interference, etc, as recommended by Polycom—and the system will be able to tell you if you’re ready for a Polycom deployment or not.” The same holds for any other Wi-Fi phone.
While AirMagnet Survey looks at the network and how it is configured, VoFi Analyzer looks at phones, and voice traffic on the network as well, and gives the IT manager direct insight into actual call quality—even on a fully encrypted network.
One critical factor in determining quality of service in a VoFi network is proper configuration of packet prioritization. That is, voice or other media streams must be able to take precedence over data traffic, or, again, latency, even dropped calls results. VoFi Analyzer monitors these configuration issues and identifies any QoS traffic problems.
“We have our own patent pending technology to calculate what we call the “WiMOS” score,” Advani told VoIPplanet.com. “We have developed our own WiMOS call where we use the basic MOS (definition) calculations, and add on wireless parameters to the original algorithm.” VoFi Analyzer also calculates WiR-Values—another quasi-objective measure of call quality.
Analyzer automatically identifies and tracks all calls and scores them in terms of WiMOS scores and WiR-Values, making it easy to troubleshoot Wi-Fi-based phone conversations.