Sniff Wi-Fi

Editor's note: In the original publication of this article, the relationship between Wi-Fi channel width and SNR was described imprecisely.  While the point of the article was correct -- that wider channel widths increase the likelihood of Wi-Fi frame failures for mobile client devices -- the mistakes have been corrected.  Thank you to Adrian Granados . Ahh, roaming. Few things capture the spirit of freedom like the ability to Roam wherever you want to go. Wi-Fi has its own brand of roaming, and there is one aspect of Wi-Fi roaming that often gets overlooked: 40 MHz and 80 MHz wide channels can make Wi-Fi users feel like they've been bounced from the Love Shack. Much has been written and spoken about the pros and cons of the three Wi-Fi channel widths: 20 MHz, 40 MHz, and 80 MHz. 20 MHz wide channels allow for the highest number of APs to be deployed -- nice for ultra high-density Wi-Fi -- because each AP takes up less of Wi-Fi's scarce frequency space.  ...

"There are known knowns; things that we know we know. There are known unknowns; that is to say there are some things we do not know. But there are also unknown unknowns -- the ones we don't know we don't know. And if one looks throughout [history], it is the latter category that tends to be the [most problematic]." -Donald Rumsfeld, former United States Secretary of Defense For those of us who follow United States politics, the above quote is a famous one.  And for those of us who work in Wi-Fi, being aware of Unknown Unknowns can make the difference between good Wi-Fi and bad. What are the Known Knowns of Wi-Fi?  AP status (up or down).  AP channel.  Number of associated client devices.  Data statistics.  We can gather these pieces of information from WLAN controllers or wireless management systems. And what are Known Unknowns?  For one, we know that we don't know precisely which nearby APs and client devices are causing CCI.  We kn...