SIP/VoIP over WiFi – Part 1: Landscape
This is the first in a series of articles about SIP/VoIP over WiFi.
Before we even start digging into protocols, let’s take a look at the WiFi spectrum and see whether we should expect any issues or problems before starting.
There are a few tools available for spectrum analysis – I use Chanalyzer Lite from MetaGeek. Chanalyzer Lite is free – and well worth the money. I bought one of MetaGeek’s Wi*Spy devices a while ago. If you need to work with WiFi, a spectrum analyzer is essential. It’s cool to plug into a laptop and perform site surveys for friends and family – tell them the best channel for their home routers. That’s usually good for at least one free dinner.
Here’s what a quick survey of my environment looks like:
The top window (Waterfall View) shows the highest saturation in channel 1, with declining signal saturation in channels 6 and 11. I’m not sure what the spike is between channels 10 and 11 – but there’s something there.
The second window (Density View) shows is there’s a high signal density centered on channel 6 – and that mysterious spike between 10 and 11.
The third window (Network Strength Over Time) shows signal strength for two of my local access points: horcrux and linksys-g.
Overall, looking at what Chanalyzer is showing us, we shouldn’t expect spectrum-related issues using horcrux for VoIP. Good signal strength, with relatively little noise or congestion.
[Now I'm curious about that spike near channel 11. I'll check that out later.]
