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...

It's summer in Los Angeles, which can only mean one thing: Sequels! As movie fans indulge in a third 'Avengers', a fifth 'Jurassic Park', and what feels like a seven hundreth 'Star Wars', this here blog is providing a sequel to a probably-long-forgotten Sniff Wi-Fi post called ' Why Are You Slowing Down My Wi-Fi, Apple? ' Turn down the lights, pop some popcorn, and enjoy the twists and turns of this harrowing look into Wi-Fi Calling on iPhones. Several months ago, this blog highlighted the Wi-Fi behavior of the iPhone X  using OmniPeek.  Truth be told, that post was a little bit like the latest 'Spider-Man' sequel: attention-grabbing title, some interesting content, but ultimately nothing consequential.  And just as movie fans knew that Michael Keaton's flying bird character wasn't going to beat the lead superhero,  a lot of Wi-Fi folks already knew that Apple iOS devices use Protection (called a "TXOP" in the blog po...

After eight and a half years, one hundred forty posts, and a shade under one-and-a-half million page views, it is clear to me that one topic causes more controversy than any other on this here Sniff Wi-Fi blog: disabling low OFDM rates (such as 6 & 9 Mbps). Wi-Fi vendors tell you to do it. CWNP trainers tell you to do it. Other bloggers tell you to do it. I (and a very, very small group of other hardcore Wi-Fi professionals) tell you   not to   do it . But this blog post isn't about re-litigating that controversial issue (for the most part).   This blog post is about telling you why I **did** disable the 6 & 9 Mbps data rates on a recent Wi-Fi optimization project. Given the subject matter of this blog post, I feel compelled to begin with some shameless self-promotion: if you have a problematic Wi-Fi deployment (or if you're in the "design" phase and you want to avoid having a problematic Wi-Fi deployment, or if you would like training on how to ...

A friend of mine recently posted a message on Twitter telling people that his email had been hacked.   I told him that his email had most likely NOT been hacked, and it took all of thirty seconds to figure that out.   A lot of people believe that their email has been hacked when they receive messages like this: From: A Friend To: Me Subject: Has your email been hacked? Body: [Forwarded message from "You" that you didn't actually send.] When someone receives an email from "You" that you didn't send, it could mean that your email is hacked, but it probably doesn't. Here's how to check: Ask your friend to click or tap on Your Name (the "From" in the email). If your real email address shows up, then the email was sent from your real email account.  That means your email has been hacked. If an email address that is NOT yours shows up when your friend clicks/taps on Your Name (in the "From" field of the email), then...

At the 2018 Wireless LAN Professional Conference (WLPC), I was scheduled to give a ten-minute "Ten Talk" on Wi-Fi surveying without using site survey software.  I aborted that talk at the last minute in favor of a talk on Ghost Frames .   After the WLPC, Matthew Norwood told me on Twitter that he was looking forward to the talk about surveying without using site survey software.  I don't want to disappoint Matthew, or anyone else who was looking forward to that scheduled Ten Talk.  Here, then, is a YouTube version of the aborted talk on Wi-Fi surveying without using site survey software: ****** If you like my blog, you can support it by shopping through my  Amazon  link or becoming a Patron on  Patreon .  Thank you. Twitter:  @Ben_SniffWiFi ben at sniffwifi dot com

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...