Sniff Wi-Fi

When using Wi-Fi spectrum analyzers, it's good to remember an old Russian proverb: Trust, but verify. Recently, I was doing some work for a company that needs BYOD Wi-Fi at several office spaces in multi-tenant buildings (insert: lame excuse for not blogging more) and we ran into what seemed to be an interference problem. Why did I think it was an interference problem? I had already completed the following checklist: 1. Cisco AP transmit power set to level 2 or 3 (that's 20 dBm to 17 dBm if you're using 3600/3700/3800 APs)? Check. 2. RRM channels 2, 3, 4, 5, 7, 8, 9 and 10 disabled? Check. 3. Excess 2.4 GHz radios disabled based on a survey done using an iPhone 4s? (What can I say? I'm a big softy for users who over-extend the life of their smartphones. They're the real MVPs of climate change.) Check. 4. OmniPeek captures, done from potential "neighbor" trouble areas, to look for channels occupied by large amounts of Retry frames?

Everybody likes high Wi-Fi speeds.  Because high Wi-Fi speeds mean that the channel is being used more efficiently ( often false ).  An efficient channel means that there's more available throughput ( only in sterile test environments ) and more available throughput means that more users can be supported concurrently ( completely wrong ). Unfortuantely, high Wi-Fi speeds sometimes  ( all the time )  come at a cost.  To get higher Wi-Fi speeds, wider channels must be used ( which makes the Wi-Fi suck ).  Using wider channels means that fewer channels will be available ( plus it ups minimum RSSI requirements, which just about guarantees a bad design ).  It is therefore essential that wireless professionals analyze the environment and carefully choose whether to use 40 MHz or 80 MHz wide channels ( or they could stop wasting everyone's time and just stick to 20 MHz channels ). But this blog post isn't about choosing the correct channel bandwidth ( although it should be, b

Spec-ing the Layers with WiSpy (one time, one time) Channel gone red with this stream (two times, two times) Killing my channel with this song Killing my WiFi With this song Taking my WiFi With this stream Killing my WiFi With Bluetooth spe-ee-ee-eeakers... Wireless streaming (music, video or, in the case of the wonderful song referenced above, a music video ) can sure kill a WiFi connection.  It's good to have a spectrum analyzer to identify the problem.  It's even better to remember to use it. Wireless streaming devices are popular nowadays, but most of them are benign.  An AppleTV, for instance, can wirelessly stream audio and video or it can act as a mirroring device for whatever audio or video is on your smartphone, tablet or laptop.  (And mirroring is tougher on WiFi than basic streaming.  When I mirror my iPhone 5, I'm creating three streams.  One from my wireless router to my phone for the Internet stream, a second from my phone back to the wireless r

It's been over two-and-a-half years since yours truly last wrote about Oscium WiPry , but there is reason to today: they fixed it!  Now the only 2.4 GHz spectrum analyzer for Apple iOS reads signal level correctly.  And using the new, corrected version reminded the author why WiPry is a nice product at a reasonable price. The concept of a spectrum analyzer hasn't changed in decades, and for good reason.  It's simple.  A device listens for activity at a given frequency and displays a readout of said activity, usually in a fancy, colorful way. In the last two years, however, many things have changed about spectrum analysis for WiFi.  PC card slots have become increasingly rare, thus leaving the Cisco Spectrum Expert in the margins.  Sensor-based spectrum analysis has increased in popularity.  Metageek, makers of my favored spectrum analyzer , stopped offering free software with their signature WiSpy series of spectrum analyzers. What hadn't changed in the last cou

When I wrote a blog post recently extolling the virtues of WiFi protocol analysis, I expected some blowback.  Not because WiFi protocol analysis won't help performance (only a Garo falo -ian fool would assert that it won't), but because I touted protocol analysis at the expense of spectrum analysis.   Well, it's time to make amends.  Spectrum analysis is pretty darned useful, too.  And the spectrum analyzer that I use ( Metageek's WiSpy DBx with Chanalyzer ) underwent a notable update in recent months.  Here, then, is an update on Chanalyzer and a reminder of what spectrum analyzers can be useful for. For quite some time Metageek's spectrum analysis suite (consisting of the WiSpy USB adapter and the Chanalyzer software application) has been the thrifty man(and woman)'s tool of choice for analyzing WiFi frequencies.  The original Metageek WiSpy (a 2.4 GHz-only device without an external antenna interface) was a $100 (all prices in USD) USB adapter and the o

Some days you wake up and say to yourself, "how can I be more like Buzzfeed ?"  Buzzfeed is popular and beloved and has an office across the street from a great Mexican restaurant.  I have a few friends and wonderful parents, but I can barely cook a taco.   What is it that I'm missing (besides venture money, a flock of ambitious MBAs and universal scorn from the intelligentsia)?  Lists!  That's what I'm missing.  Hit-trawling, crowd-pleasing lists! So here it is: the first in what hopefully will be a series of one.  A list of Three Simple Ways to Boost Your WiFi.  #LOL #cute #OMG #trashy 1) Add an 802.11n/ac USB adapter to old 802.11a/b/g laptops and desktops. Some folks in the WLAN business like to use the term "5G" to refer to 802.11ac, but I refer to 802.11a/b/g as 1st generation WiFi and 802.11n/ac as 2nd generation WiFi.  The reason I do that is because big improvements to power consumption, receive sensitivity and channel bonding are avail