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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?"
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.
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
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
Unlicensed means you can operate such a device without an operator's license.
It does *not* mean that the FCC doesn't care, or that they won't investigate interference.
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.
Summary:
... or else my card (Intel Link 1000 BGN) isn't supported. (Netstumbler is an example ...)
Parent:
Try using a wireless network monitoring program like ... Net Stumbler for Windows.
Yes, I know this is slashdot, and we don't read the articles; but is it too much to ask for you to read the freaking SUMMARY before you reply with a useless load of blather?
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.
Nowadays it might be better and cheaper to go with 1.3 Ghz phones. Uses the TV bands that were freed up. I have one and have wonderfully interference-free calls.
Warning, knife is sharp. Please keep out of children.
...enter the FCC. That's kinda what they do....
Metageek has a few products in their Wi-Spy USB Spectrum Analyzer family. The cheapest one (the 2.4i) is $99, and the next model up (2.4x) is $199. It analyzes the entire 2.4GHz spectrum using your laptop and lets you see potential sources of interference. The 2.4x version allows you to use their more advanced software which also has device signatures -- you can overlay signal patterns of various types of devices (microwave, cordless phone, wireless baby monitors, etc.) on top of the signal density graph in order to identify what's causing the interference. I use the DBx version (2.4 + 5GHz) at work, and it's great for helping to find problems.
You'll find a prior posted thread of mine about a spec analyzer. Perhaps it's out of financial range for the poster, since they seem to want a virtually no-cost solution, but I do offer suggestions on a spec analyzer for around $100, which is pretty good.
I didn't want to dupe that info in this thread, and it wasn't exactly the point of my post anyway. The GP claimed the FCC didn't care about unlicensed spectrum, but they do. However, they'll care a lot more if you show up with some real data - rather than "someone" must be doing something bad since my wifi doesn't work.
-Greg
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
I've been using the Wi-Spy from Metageek at work. I hadn't heard of the Ubiquity AirView. It looks like it's pretty competitive with the Wi-Spy -- apparently it uses the same chip, and the software has similar features. It'd be great if the AirView software had device signatures, but it appears that they're pretty receptive to feature requests through their forums. I'll definitely have to keep that product in mind as a recommendation to others. Thanks!
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
You can do the same issue with dd-wrt, but that only if the signal also conforms to the 802.11b specification.
A burst of noise or device using the spectrum differently will not display using such techniques. The spectrum is open and there are a number of protocols today that rely on those frequencies.
I had a friend with a 2.4ghz phone which would completely and utterly destroy our wireless reception.
"You should always go to other people's funerals; otherwise, they won't come to yours." -- Yogi Berra
I would add only one detail: tune the AM radio up near the "high end" of the radio spectrum, around 1500 or so. That's the part of the AM spectrum that's closest to 2400 Mhz, and thus most likely to pick up the interference.
I have no problem with your religion until you decide it's reason to deprive others of the truth.
It may in fact be a ham that is legally operating in the 2.4GHz band. Hams are licensed users of this spectrum, and have priority. They could be causing the interference (if in fact they are), and if so you just have to live with it, if it can't be resolved. Hams are also protected from interference (by law) from the unlicensed users of the spectrum.
And by the way, end users increasing the power output of a WiFi transmitter is not a good idea. It can cause interference on nearby spectrum, and increased noise levels in the band, which can defeat the purpose of the increase in the first place. This is not something that should be hacked.
Heisenberg may have been here.
A quick clarification: The top of the AM dial (around 1500) is 1500kHz, or 1.5MHz. This is not close to the 2400MHz, or 2.4GHz at which WiFi operates.
The ability to identify the origin of the interference using an AM radio relies on the fact that the interference is produced from a source (often an electrical spark or arc) which generates RF noise on the entire spectrum. The spark plugs in car engines are a notorious cause of this sort of interference. If the spark plug wiring in a car is not shielded properly, you will hear a whining sound on an AM radio which changes pitch as the engine RPM changes.
AM radios happen to be easy to find and are very good at "hearing" the noise produced by an arc. If the noise is something like a microwave oven, which produces RF energy only at about 2.4GHz, then the AM radio will not help you find the problem.
I hope this helps to clarify the issues.
-Todd
p.s. As an interesting experiment. If you have WiFi and a microwave oven in your house/apartment, start downloading a large file. Look at the download rate (300kB/sec. or whatever). Then, start the microwave and look at the download rate. Mine drops to about 10-20kB/sec., because the microwave interferes with the WiFi signal.
Omne ignotum pro magnifico.
it's the years on end part which kind of rules that one out, i think. op says it only happens for a couple hours each night. unlikely that's the only time when the baby monitor would be in use....
Google xirrus wifi monitor. Is a free wifi signal monitor.
You are all assuming it's another Wifi device.
By the exact timing, it sounds more like ordinary unexciting EM interference.
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
+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.
Indeed... I put my 2.4 GHz AP on channel 1, because *all* the APs I could see from my house was on channels 6 and higher. It turns out to be a reason for that -- something that *isn't* 802.11 is interfering with the lower channels. Bumping it to channel 11 and all the interference problems went away.
Wifi operates in the ISM bands - the scrap heaps of the radio spectrum. There is tons of crap, and 802.11 is just a small part of that.
Fox and CNN supply different data. A Wi-Fi channel carries the same data. A difference that makes no difference.
The point was that say someone is operating under the part 97 (amateur service) rules in the frequencies of WiFi that overlap the ham band... who do you think wins?
The guy with the license, that's who.
"Alcohol, Tobacco, Firearms, and Explosives" should be a convenience store, not a government agency.
If you have an Android phone, you can download a free application called WiFi Analyzer by Kevin Yuan which scans signal strength and can identify possibly interfering networks, pretty much like NetStumbler but in a more convenient package. If you are patient enough then you can map out signal strengths in various locations when you have GOOD reception, and then compare them to what happens when you have BAD reception and see where the interference is worse.. if it's a rival WiFi network then it should be even easier! But as others say.. the source of interference could be one of so many things in the 2.4 GHz band including DECT phones, baby monitors, microwaves or even just plain old fault equipment
Never email donotemail@WeAreSpammers.com
For about $30 - $40 you can get the Ubiquiti AirView spectrum analyzer usb dongle. From what I understand this will run on linux (don't quote me on that. I don't own one). http://www.google.com/products?hl=en&safe=off&q=ubiquiti%20airview&um=1&ie=UTF-8&sa=N&tab=wf
He screwed up more than just the last line.
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.
If you live close to water where big ships dock then there's a good chance it could be radar. It may sound far fetched but it has happened before with a company who couldn't figure out why the entire wireless network went down every day at the same time. Turned out there was a harbour with big navy ships nearby, due to the tide the ships radar would be at a certain height at a specific time each day which would cause the radar to interfere with wireless signals.
Growing up a friend of mine had a CB base station and a Ham radio, not satisfied with the range on his CB Base station he added boosters to his system. Any time he fired up his Base station to full power, TV's for a block or so went out everytime he key his mic. Look around and see if you see any radio antenna's around the neighborhood. Could be an overpowered CB or Ham Radio operator that gets on at that time every night.
This has to be an urban legend because the tide is not at the same height at the same time each day. The full tide cycle is roughly 12 hours, 18 minutes, so the time of high tide is going to be at a different time each day.
Try again.
"Ayn Rand is a bloody socialist compared to me." - Robert A. Heinlein
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.
1. Download a Ubuntu Live CD.
2. Open a terminal and type "sudo apt-get install aircrack-ng"
3. If aircrack-ng installs successfully (you may need to connect an ethernet cable to get an internet connection), type "sudo airmon-ng start wlan0".
4. Type in "sudo airodump-ng mon0" and you'll get a nice list of all the wireless access points in your area (even the hidden ones).
Aircrack-ng (and airodump-ng) documentation can be found here.
You can also try NetStumbler, which runs on Windows, but it much less powerful.
Unless the interference cause isn't subject to Part 15. The general pecking order in most of the ISM bands is:
Primary user: Military - They can run whatever power levels they want, and the secondary/tertiary users are screwed. However, the military typically stays out of the ISM bands because they're an interference cesspool unless they run crazy power levels.
Secondary user: Amateur (ham) radio operators - Legal limit 1500W, can't interfere with the military but can interfere with the tertiary user (but usually try to avoid doing so), and tend to stay away from the ISM bands for the same reason as the military. Occasionally hams will reclassify Part 15 devices under Part 97 (pretty much need to disable encryption and adhere to IDing rules), but it's very rare these days - just not worth the trouble.
Tertiary user: Unlicensed users.
The FCC is unlikely to investigate unless you have some evidence. Get a card supported by NetStumbler or Kismet (this won't help you much if your interference source is not 802.11), or get a 2.4 GHz spectrum analyzer such as the Ubiqiti AirView2-EXT ($60) or WiSpy 2.4x ($200).
I'm surprised that an Intel card isn't supported by any of the Wi-Fi monitoring tools. Intel cards usually are. (Maybe Kismet supports it but NS doesn't?)
retrorocket.o not found, launch anyway?
As an interesting experiment. If you have WiFi and a microwave oven in your house/apartment, start downloading a large file. Look at the download rate (300kB/sec. or whatever). Then, start the microwave and look at the download rate. Mine drops to about 10-20kB/sec., because the microwave interferes with the WiFi signal.
Here is another one. Put your cell phone in the microwave, and close the door. DON'T TURN THE MICROWAVE ON. After a few seconds, your cell phone should say, "no signal," or "out of network," etc. If your cell phone still has signal after 10 seconds, it's time to get a new microwave. The housing of your microwave is no longer acting as an effective faraday cage, and is leaking dangerous amounts of radiation.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
I used the Wi-Spy 2.4i and easily tracked down a source of interference (in my case, a wireless rear-view trailer camera) in a crowded convention hall in a matter of minutes, and I didn't even know what I was doing at the time. It was crapping all over my Wi-Fi network, and as soon as they shut it off, I was back in business again.
I've since upgraded to the 2.4x model and track down Wi-Fi interference all the time. I would consider $99 cheap, consumer grade equipment. (Assuming you already own a laptop.)
-Arthur
Cave ne ante ullas catapultas ambules
That is not correct for North America. The 700MHz band is what was freed up, UHF channels 52-69. Channel 69 was at 800 MHz. The highest channel ever allocated was 83, at 885MHz (rescinded sometime in the 80s). There was no 1.3 GHz broadcast TV channel in the US.
-molo
Using your sig line to advertise for friends is lame.
Decomposition generates a lot of heat...
Normally I don't feed the trolls, but sometimes the trolls just beg to be fed a little bit of humble pie. It took all of about 20 seconds to find an article showing actual ham deployment, at the request of a local emergency agency, in the US. http://journalstar.com/news/local/article_84aba07a-3d9b-11df-8d7a-001cc4c03286.html A local news source including video from officials involved. Is that "reputable" enough for you?
And ham radio isn't just using "ancient analog technologies" to chat with each other about the bad conditions in nursing homes. While there is a lot of analog technology still in use, hams are also at the forefront of digital (extremely) narrow bandwidth communications development. The other thing to consider is that old analog technology doesn't stop working because one ham's clock is set a little off from another's, essentially what happened in Nebraska to take the 911 systems offline.
Ham radio is also not slowly dying as all the "old fogies" die off. The number of newly licensed hams is actually on the increase. http://www.ah0a.org/FCC/Graphs.html That data is sourced from the FCC license database if you want to go compile it yourself. There was a decline for a few years, but it is increasing in popularity again and is almost up to the pre-decline numbers. More and more young people are getting involved in ham radio. I know personally of several licensed hams who are 7 and 8 years old! The younger hams are very passionate about the hobby and more importantly the public service provided by hams.
As Random Coward pointed out above, if you think if the ham bands were suddenly taken away from hams that the spectrum would all turn into "part 15" unlicensed spectrum, you must not have taken your meds for a while. You said yourself how valuable the spectrum would be if it were to be auctioned off. Do you think the FCC and the rest of the government is going to donate those billions of dollars worth of spectrum to the public domain? They'll go the the highest bidders and they will be defended from illegal users (what "the people" will be) without end.
If you want "the public" to use the ham spectrum, nothing is stopping you from getting your license. It costs $14 to cover the expenses of the VOLUNTEERS who will administer the exam to you. Study materials are available at no charge all over the Internet. Once you have your license you'll be out a couple of hundred bucks for some radio gear to get started using the spectrum as you see fit (within the legal boundaries of course.) Ham radio is not about the "rich" people at all. It is just like any other organized hobby or service, you can do it relatively inexpensively or you can literally spend as much money as you want on it, depending on what you want to do and how far you want to take it.
Say what you will, but your argument doesn't hold water against verifiable facts.