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.  ...

The recently completed Wireless LAN Professionals Conference (WLPC) was nice enough to gift attendees a Wi-Fi Stand .  The product is a clever one, but as a person who believes in measuring Wi-Fi propagation accurately when surveying, I was concerned.  When I tested it, my results showed that my concerns appear to be unfounded. The Wi-Fi stand is an apparatus that screws in to the top of a tripod to make a vertical, rectangular structure that allows enterprise APs to be hung upside down from standard ceiling mounts.  If that is a little bit hard to visualize, here's my best shot at describing it: The graphic on the left is what the Wi-Fi Stand looks like and the graphic on the right is how the Wi-Fi Stand looks on top of a tripod. I am a big believer in designing & surveying Wi-Fi using real, production devices, and a longstanding problem with that has been temporarily mounting APs for the design/survey.  I've tried zip ties, and velcro.  I've gone...

Back in my day, we called it The Corner .  Nowadays, the kids call it The Trap . (WARNING: Very NSFW) The average IT professional may not view Wi-Fi "Design" as being directly analogous to the inner city drug trade.  Yet, when Wi-Fi Professionals go through the process of choosing AP installation locations, they should know what even the most novice  B.G. drug dealer knows: that The Corner is also The Trap. When embarking on a Wi-Fi "Design", some things are obvious.  Coverage is needed everywhere.  The number of available APs must be appropriate for the number of expected Wi-Fi devices.  Physical objects (walls, doors, et al.) should be accounted for. A less obvious part of Wi-Fi "Design" is avoiding Hidden Node problems.  The Hidden Node problem occurs when two or more devices on the same channel A) cannot "hear" each other, and B) can interfere with each other. The reason why Hidden Node is a problem is that Wi-Fi devices rely o...