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Tracking Down Wi-Fi Interference?
Nicros writes "Almost every evening, between 8:30 and 10:00, my Wi-Fi just dies. This, in itself, could be explained by a crappy Wi-Fi source or some hardware failure, except that I know both of my neighbors are experiencing the same loss of signal at the same time. While the Wi-Fi is down, the LAN is OK, and anything plugged into Cat5 can access the Internet just fine. One possibility comes to mind — perhaps some other neighbor arrives home and turns on their router from 8:30 to 10:00? And something in their signal is hosing our Wi-Fi? I have tried looking around for software to help identify the source of interference, but either the programs are ridiculously expensive for a home user, or else my card (Intel Link 1000 BGN) isn't supported. (Netstumbler is an example of the latter.) Any suggestions on how I can track this down?"
First thing to try is setting your AP to a different channel.
If that doesn't set you right, get a USB Wifi device that is supported under Linux and fire up Kismet and identify any strong signals nearby.
Once he got a 5 GHz phone all was well.
Long story, short: lots of things use the 2.4 GHz spectrum. It may not have anything to do with WiFi.
An associate of mine reported the same issue. In his case it was a failed security lamp that was trying to come on at sunset and failing; it was only when the ballast gave up after an hour and a half that his wifi -- and his AM radio -- came back. Note that many security lights are sodium arc or mercury vapor arc; not much is as hard on RF in general as a big fat arc.
...put a sign in your front window or building lobby asking if anyone else is having the same problem, or uses electrical equipment only between those times. Make it a friendly note, with smiles, rainbows, and unicorns, so you don't offend anyone or make it look like a witch. As a bonus you get to know your neighbours.
If you are finding your fancy wifi card isn't supported by stumbler and other free channel overlap type tools . . . why not buy a cheap wifi card to use with those apps? You could always drop it back on craigslist/ebay (or even return it to the store claiming it doesn't match your curtains).
That's the same time I microwave up all my hotpockets for the next day's raiding Ice Crown Citadel...
Talk to someone in your local ham radio club and see if they have a member with a spectrum analyzer and a directional antenna. Have them come out to the house and do some direction finding to determine who is transmittin on the WiFi freqeuncies in your neighbourhood.
Be polite. Ask nicely. Buy them pizza and beer to say thank you.
Hams are nice guys and gals and they will probably be happy to help out.
The ARRL website can probably provide a contact for your local ham radio club.
I'd help you buddy, but every night between 8:30 and 10:00pm I'm working on my microwave disruptor beam. If it happens any other time, let me know and I'll be glad to pop over and take a look.
inSSIDer
I've been pretty happy using that to help find the best channel for my WAPs in congested areas. If you really believe it might be a neighbor jumping online from 8:30 to 10, that could help. I haven't yet found a card it doesn't work with under windows (assuming you are running windows...)
Happens the same whether you're on channel 1, 6, or 11? (the only b/g channels that don't overlap)
I know in my high-rise apartment, almost everyone is on channel 6, and I wouldn't be surprised if peak usage was mid-evening.
Did you double-check that some rule didn't accidentally get selected, which filters you out (either in the router interface... of you're using software that has scheduling...)
If you're using a radio type that is using the 5Ghz channel, someone's old beastly cordless phone might be affecting it too. If you're using a dual-band radio on your router, try using the other band and see what happens.
Running Wireshark (free) might not tell you what specifically is causing the problem, but you can narrow it down to see if packets are timing out, or getting filtered. Maybe there's traffic you didn't expect to be there? http://www.wireshark.org/download.html
For example I run netbsd on my wife router
NetBSD...it really does run on anything!
Did you get your wife from Stepford?
I will add my 2c and say it is the increased usage of cordless 2.4GHz phones during those hours. Some of the (cheap) units don't behave particularly well with WiFi and I've personally seen just one phone cause a complete outage of all WiFi in a house.
Chances are that one of your neighbours with a teenage daughter bought some cheap but funky looking cordless phone off eBay and uses it every night during your outage window.
Dan. -- So what if it's spelt wrong, nobody's perfect
Netstumbler did not support my wifi card but came across InSSIDer which is free, and allowed me to easily see channel usage in the neighbourhood. They also sell USB spectrum analyzers for non wifi interference which is what you may need. http://www.metageek.net/products/inssider
This is exactly the problem we had with our apartment neighbor's teenage daughter. 8:30pm -10:00 pm fits the high school homework phone schedule.
A gift of 5 GHz wireless phones to the neighbors (in exchange for their old phones of course) cleaned up our mutual WiFi problems.
Took the old phones and dumped them into ATT Wireless Store's recycle bin.
Get either the USB stick or one of the 2.4Ghz supported AP's from Ubiquiti. [www.ubnt.com]
The newest firmware supports a Spec analyzer mode - quite good, IMO - and it's not limited to WiFi equipment - anything in the radio spectrum is "seen."
Their wireless bridges in the 5Ghz spectrum using N tech (dual spacial streams) are seriously killer too - if you've got a wireless bridge, or WISP type situation, it's really, really cheap stuff. I'm likely to end up with 2.4 ghz and 5Ghz units just for spec analysis on the cheap. The units then double as AP's / routers / Bridges. (And at around $100 each, they're pretty awesome - Bullet M5, and Nano Station M5's for example.Find a wireless N bridge that will hold links over miles that are that cheap anywhere else!)
For around $100 you could have a nice AP and a spec unit in the same hardware. Antenna, unless built into the unit is a bit more difficult/pricey, but still do-able.
Anyway, I've got a setup using them in a PtMP setup, and though it's not miles, I'm seriously impressed - and the cost factor is simply *insanely* cheap.
http://www.ubnt.com/
-Greg
Meaning that the FCC won't do anything if your microwave is making your router go wonky. But since there is something causing outside interference to multiple people, they WILL track it down, as that means there is a device somewhere in your neighborhood that is violating the first part of the above condition.
"So after all this, you make my case for me. To end this stalemate, you must die..."
You realize that N doesn't spec frequency, right?
802.11n can run in 5Ghz spectrum, but can also run in 2.4 spectrum. So, simply saying "use N" doesn't mean anything in terms of frequency.
In fact, most of the "consumer-grade" 802.11n equipment is 2.4Ghz exclusively.
---
I'd mostly agree that 5Ghz spectrum will be less cluttered, but I'd also guess that decent equipment using the tech in the N standard will do a lot better in 2.4 than b/g will. Multiple spacial streams, and (when implemented beam-forming) as well as beneficial use of "multi-path" etc will probably make N a lot better in most environments regardless of spectrum.
Baby monitors. One of the few devices that can completely trash all wi-fi frequencies in an area, not just for 1-20 minutes like a microwave but for years on end. Especially older models which use an analog signal.
I don't know if they'll come and check things out, but they do care about unlicensed bands - if you're way outside the power envelope allowed, I'm sure they'll whack you upside the head just as bad as if you were doing it in licensed spectrum.
Given the symptoms, I wouldn't be surprised to find something in the spectrum being used that IS outside the allowed power-limits.
However, I think you're more likely to get results if you find out what the offending device/person/entity is and asking them to help resolve the conflict. If they don't then you can move on to a complaint with the FCC based on power-output.
...enter the FCC. That's kinda what they do....
Here's a cheap build-it-yourself spectrum analyzer: http://hackaday.com/2010/03/17/im-me-spectrum-analyzer/ The IM-ME can be had for about $15 or so, and is purportedly very hackable.
John
It's an unlicensed service, provided you use licensed hardware to operate on it. That means, there's FCC certification behind all the commercial wifi gear you use. If you modify it or add on power boosting transmitters, you're using unlicensed hardware and the FCC will come after you.
That device only covers 281 - 361, 378 - 481, and 749 - 962 MHz bands. It will not be useful for debugging the 2.4ghz spectrum.
There are likely some other options for a cheap analyzer around. I had some friends in a wireless shop convert an AP to a spectrum analyzer via a firmware update . However, those AP's were intended for commercial use and the price was a bit too steep.
"You should always go to other people's funerals; otherwise, they won't come to yours." -- Yogi Berra
http://hackaday.com/2010/03/17/im-me-spectrum-analyzer/ [hackaday.com] The IM-ME can be had for about $15 or so, and is purportedly very hackable.
But it's... pink...
46137
8:30 - 10:00 could also be a baby monitor.
I'll never make that mistake again, reading the experts' opinions. - Feynman
+1 - we were given a baby monitor that transmits live video and source temperature. It destroys our WiFi capability - but only within 20 metres or so.
So is your dick. Do you avoid that too?
"A great democracy must be progressive or it will soon cease to be a great democracy." --Theodore Roosevelt
Not at all. Changing channels is a low work method to solve the problem which will take little time. Since it may very well fix it, it is an efficient first thing to do. Who needs to know about interference on an unused channel? Additionally they may provide information. For example, If all channels are blocked then it is not likely to be another Wi-FI issue unless something is majorly broken (to the point of not functioning). If the quick, cheap and easy fail then you assign resources to the problem.
"It does *not* mean that the FCC doesn't care, or that they won't investigate interference."
Investigate it yourself.
Go from house to house, both sides of your street, pounding on doors, yelling "I'm gunna start kicking some ass if you don't stop interfering with my WiFi Signal! Pussy! C'mon!".
The guy that DOESN'T come outside and kick your ass is the culprit. Speak to him privately after you get out of the hospital. I'm sure the two of you can come to a reasonable solution to the issue if you just relax and work things out rationally.
airodump-ng --showack -w output mon0
take note that all your idiotic neighbors all use channel 6 for everything.
decrypt WEP/WPA keys for router.
connect to router, login using default (never changed) credentials.
upload notepad.exe to router as a firmware upgrade.
no wireless devices running in range of your equipment.
And here's another one along similar lines. Some time ago, someone's network went down regularly at the same time every evening. In the end, it was found that the bank on the floors below was turning on a microwave-based motion detector after closing. Perhaps in this WiFi case, something industrial or commercial is being activated nightly nearby? 8:30 to 10 seems a lot like cleaning staff hours. Maybe a floor polisher motor or vacuum with bad brushes putting out a lot of EMI.
and source temperature
I know this is probably for detecting a fever. But I just wanted to point out that it's also good for detecting dead babies.
A couple of days ago, I was using my microwave oven while watching a MythTV stream over the Wi-Fi network from a laptop three feet away. Not even a hiccup.
The whole point of the design of a microwave is that the holes in its Faraday cage are much smaller than the wavelength of the signal generator within. If your microwave is wrecking your Wi-Fi connection, don't grumble about it. Get a newer microwave oven.
Check out my sci-fi/humor trilogy at PatriotsBooks.
No ... I was working in a Norfolk hospital lab when some idiot turned on the horizon-scanning radar for an aircraft carrier that was nearby - it should have been locked down, but wasn't. A lot of our electronics readouts went berserk from the induced interference, harmonics and other crap that thing was belching out. ICU had it worse because all their heart monitors and ventilators were affected. It was an interesting few minutes.
You do realise you're posting on slashdot?
Not everyone knows their mom as well as they should.
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