Tag Archives: Wi-Fi Interference

Interfering Personal Hotspots- Beyond Simply a Technical Issue

After 20-some odd years in the Wi-Fi business, I can safely say that I both love and hate personal wireless hotspots. Before I get into all that, let’s go back in time. If you want some zesty background, here are a few easy, compelling reads written by me from the way back machine:

If you don’t want to review the above links, here’s the poor man’s executive summary:

FCC: Don’t use de-auth frames- that equals jamming (depending on which one of our own definitions you stumble across). Selling jammers is illegal. We let Wi-Fi vendors sell illegal jammers because they provide tools that do de-auth. But that is illegal. You can’t sell jammers except when you can sell jammers. Confused? Shut up, or maybe we’ll fine your ass for our lack of clarity. Our annual fund-raiser is coming up- how’d you like to “donate” several thousand dollars?

Hotspot Makers: We use only the highest power and some really cocked up channel selection algorithms to ensure your device delivers the absolute finest in RF interference to the Wi-Fi environment you are sitting in the middle of.


Network Customers, WLAN Admins: WTF?

It all makes perfect sense if you don’t think about it.

The Technical Frustrations

Anyone else in the biz knows that hotspots can be annoying, or they can be WLAN-killers. It all depends on the day, the device, the location, and the density of the WLAN where those hotspots are fired up. You can only play so many frequency-stomping games with spectrum, then physics shows through and Wi-Fi sucks for everyone until the contention is eliminated. This is the technical side of hotspot frustration.

And nobody of title has done a shittin’ thing to improve the situation- not the FCC, not the WI-Fi Alliance whose members make all of the devices that step on each other, not anybody. Everyone is in it for themselves… (Soapbox moment brought to you by the good folks at Shamwowsers & McKracken, LLC).

Ah well.

The Cultural Component to the Whole Mess

Cell phones and Mi-Fi devices have come soooo far since WLAN administrators first played whack-a-mole with hotspot-induced network issues. Data plans have also evolved, to the point where many of us are walking around with dual-band, unlimited data hotspots in our pockets ready to put into service at the slightest notion.

Let’s turn to rocker Ted Nugent for his take on the situation, as written about in his mega-hit “Free For All”:

Well looky here, you sweet young thing: the magic’s in my hands
When in doubt, I’ll whip it out. I got me a hotspot- dual-band
It’s a free for all

Or something like that… It ABSOLUTELY IS a free for all. That’s the culture right now. If I can’t get on the business network because I don’t know how to configure meself for 802.1X, I’m gonna WHIP IT OUT, Nugent-style, and get myself off to the Internet. The business Wi-Fi can suck it, and how dare you expect me to open a trouble ticket to get help with your 802.1X noise? THE MAGIC IS IN MY HANDS. Any collateral damage is NOT MY PROBLEM.

So what if your stupid police cars can’t transfer dashcam video because of interference? Why do I give two figs if your expensive Wi-Fi locks and clocks are acting up because of my RF pride and joy? Spare me the lecture on how your wireless VoIP handsets are getting walked on… Maybe YOU shouldn’t be using Wi-Fi-equipped medical devices. IT’S A FREE FOR ALL, DID YOU NOT GET THAT MEMO FROM TED NUGENT?

Hate ’em, Love ’em

Yeah, hotspots are a big fat PITA. They really do create problems. Some are dual-band, high power beasts that insist on obliterating your WLAN, while others seem to have a little more common sense and lower power built in, but in dense WLAN environments it still gets ugly.

But I’m here to confess that I too hear their siren song.

I get WHY people fire up their hotspots. At hotels, at camp, while troubleshooting systems that have potential ISP issues and so on. My phone’s hotspot gets it’s share of exercise, and I can’t imagine not having it available in a number of situations. But as a WLAN professional, I have the knowledge and (usually) the discipline to not hose up someone else’s WLAN with my hotspot when I’m at their place of business. Most people- not so much.

We’re way past the opportunity for THE INDUSTRY PLAYERS to responsibly to educate end users on why hotspots shouldn’t just be whipped out Ted Nugent-style. So we’re stuck with the problem.

Suck it up, Buttercup

What really sucks about all of this is that WLAN components are only getting ever more expensive. The tools that are used to design and support WLANs are only getting more expensive. Collectively, the security stakes in almost all WLAN environments are only getting higher. We can pump endless dollars and man-hours into delivering really good Wi-Fi, yet hotspots can lay waste to parts of our infrastructures, and there isn’t much anyone can do except to ask the offender to put them away, if we can pinpoint them and get them to listen to our appeal that they think of their fellow man…

Strange times, says I.

Some Rogue APs You Just Gotta Live With

As I look in on the management console of my big Cisco WLAN, I see at the moment I have 711 detected rogues on my biggest campus. Detection in this case loosly equals:

  • Being heard by one or more APs that have been configured to take part in rogue detection
  • Breaking our threshold of concern (I have set to RSSI of -78)
  • Being heard within the last few days

Because of where this WLAN sits geographically and the fact that we have thousands of APs (with hundreds participating in rogue detection), our rogue dashboard stays pretty busy. We’re in a city, surrounded by hospitals, businesses, and residential neighborhoods. I asked The Google for graphical help:


This is a quick and dirty view of our main campus area, and doesn’t show several of our local remote sites or our mile-away other large campus. But- you can see we’re surrounded by lots of buildings. And… those buildings have lots of Wi-Fi. Because we’re so close, we can’t help but to mutually interfere with our neighbors. Our high density design keeps our APs usually running very low power, and we try to be good neighbors.

For giggles, here’s a partial list of interfering SSIDs along with channel and signal strength (perceived by our APs) that I really can’t do a thing about. This DOES NOT include the known “regulars” that have already been “acknowledged”- the hospitals, JPMC, local hotels, etc,  Each of the following is absolutely outside of our own buildings:

  • SSID: PA 217A, Channel 6, Strongest AP RSSI: -41 (yes, -41)
  • Guest Network, 11, -43
  • On Route (several instances, all very strong, scattered all over 2.4 GHz and 5 GHz, very transient)
  • Apple, 6, -47
  • Netgear, 1, -49
  • AirDelt, 10, -57 (Asustek)
  • TWCWIFI and TWCWIFI Passpoint. 11, -57 (These are Ruckus)
  • IACNY (multiple), 4, -60
  • <non-broadcast>, 3, -61
  • prettygirlthreadz, 11, -62 (Actiontec)
  • Braka Air, 1, -62
  • Themis Corporate, 2, -62 (Apple)
  • Tits for Password, 1, -63 (Belkin)
  • EnvySalon. 1, -63 (Cisco-Linksys)
  • Dr Cohen, 9, -63 (Cisco)
  • DTD Ground1, 3, -63 (Cisco-Linksys)
  • PsyMiFi, 2, -63 (Novatel)
  • ATT912, 8, -65 (Motorola)
  • DensityAP431, 6, -65 (Tp-Link)
  • <non-broadcast>, 9, -65 (Z-com)
  • MidValleyHospice, 8, -65 (Netgear)
  • CrepeandGelatoEspressoBar, 6, -66 (Actiontec)
  • <non-broadcast>, 10, -65 (Nintendo)
  • 2WIRE260, 4, -67 (2wire)

I’m hoping you get the point. Remember- my current view shows over 700 of these. To the trained wireless eye, there are many stories in this sample of my overall reported rogue list:

– lots of consumer-grade stuff
– lots of default channel 6
– lots of CCI, ACI, and every xCI you can think of afoot
– lots of nearby networks that likely aren’t performing all that well, and certainly not up to their potentials
– most of the noise is in 2.4 GHz (but certainly not all on the full list)
– our own network has a lot to contend with on our geographic edges

Given the wild-west nature of unlicensed wireless, this snapshot is just another day in the life of my WLAN. I can’t do much about the neighbors, but occasionally do help them when one of them reaches out. The conversation usually goes like:

“I hear you’re the campus wireless guy”
What can I do for you.
“I’m your neighbor and my wireless sucks. Any thoughts?”

(this is where we gather a little info, talk about what else they see in their client utility and whether they can access their wireless router’s admin pages)

Change your channel and expect to have to do that now and then. Stay on 1, 6, or 11. Here’s how to tell what’s best (point to free tools). Buy a 5 GHz router.

The problem usually goes away, or at least gets better.

Back to topic: rogue detection is nice, and I’d hate to be without it. And the quest for clean channels is worthy, never-ending, and can be frustrating at times when your WLAN lives in a busy, dynamic, unpredictable RF neighborhood. But I will give Cisco’s RRM a lot of credit, when tuned properly it does a pretty effective job of adjusting to the sort of variability and contention shown above, without being overly disruptive.

Competing signals are a way of life, and many of us WLAN types simply have to make the best of complicated situations.