WiFi gets clobbered by baby-monitors, not other WiFi
Ofcom, the UK equivalent to the FCC, has a new report that identifies baby monitors and other wireless devices as serious interferers with urban WiFi. I've got WiFi and a baby-monitor in my tiny London flat and I can't say I've ever noticed the issue -- on the other hand, my spark-gap generator seems to really do some interesting stuff to the network.
"There is a view that some domestic users generate excessive amounts of Wi-Fi traffic, denying access to other users," claims the report from wireless specialists, Mass Consutling. "Our research suggests that this is not the case, rather the affected parties are almost certainly seeing interference from non-Wi-Fi devices such as microwave ovens, Audio Video senders, security cameras or baby monitors."Baby monitors killing urban Wi-Fi (via /.)"The greatest concentration of different radio types tends to occur in urban centres, so interference tends to increase with population density.
"However, interference also occurs in low population density areas. It only requires a single device, such as an analogue video sender, to severely affect Wi-Fi services within a short range, such that a single large building or cluster of houses can experience difficulties with using a single Wi-Fi channel."
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Makes a lot of sense. I would imagine that the RF from the average el-cheepo baby monitor has more harmonics that a Hendrix solo.
I can't wait for Analog TV to shutdown. Hopefully we can finally have some decent reserved bandwidth for Wi-Fi. And dare I dream it, pro wireless receiver / transmitters.
2.4GHz phones are also wonderful DoS tools.
Microwave ovens and many wireless phones work in the 2.5 gig band. So far I've not seen any trouble from either. There's is also some TV microwave pickup there but only as a last resort as there are so many other users.
Essentially there are no primary users. It's up for grabs.
My neighbor bought a rebadged higher-power version of my router and apparently neither are capable of 'playing nice' so I lost all my WiFi -- in dense areas where there's a lot of the same cheap routers floating around, it can be a big problem even with different channels being used.
Not to say that even noisier stuff in the same band isn't worse. It's getting crowded, even with a few bands available. How many RF devices do we all have at this point?
Man, I knew about this in the mid-1980s. I'd watch UHF TV shows and every now and then hear odd voices. Thought I was going nuts! It was a family in my building. They were (and still are) Russian, so it made it seem even more exotic.
So the solution is to wrap your children in aluminum foil? Got it. Will do.
@David Carroll: Any non-802.11 2.4 GHz device can cause interference. Examples include baby monitors, cordless phones, cordless video cameras, and such. It's not about dirty signal or harmonics. It's just about two devices using completely different modulation and encoding methods on the same frequency. Garbage results.
802.11 devices do not generally interfere with each other AS LONG AS THEY ARE CONFIGURED ON COMPATIBLE CHANNELS. 802.11 has a big complicated algorithm called CSMA/CA that ensures that two radios on the same channel do not interfere. Usually. The problems usually happen when people configure their devices to incompatible channels.
Here is the short version: if you have a Wi-Fi device operating in 2.4 GHz, ONLY PUT IT ON CHANNELS 1, 6, OR 11. Seriously, forget that all those other channels exist.
Here's why: 802.11 2.4 GHz channels overlap with each other about +/-3 channels. This means that if you are on channel 1 and I go to channel 3, we are actually overlapping. Because we're just overlapping and not on the same channel, CSMA/CA can't do its job very well, and interference results. We both get poor performance. By the time you get to channels 1 and 6, the distance between them is sufficient to prevent overlap.
With 802.11, two devices on the SAME channel will usually get better performance than two devices on close and overlapping channels (like 1 and 2, 1 and 3, and so on). It's the jerk who puts his device on channel 3, trying to be clever, who ruins it for people on channels 1 and 6. And the real irony is that the jerk on channel 3 is getting his performance screwed up too.
Can someone recommend a monitor that *won't* do this? I've been looking for one of these for a few days now. All I can find is a Philips DECT monitor that was recommended by David a few years back:
http://www.boingboing.net/2007/02/philips-interference.html
Two hundred bucks though! Yeesh!
Think I've seen the reverse of this. My grandmothers doorbell used a small radio transmitter. As more and more wifi appeared in her appartment block over the past five years the doorbell got more and more flaky.
Doorbell replaced with old fashioned wired variety.
"Audio-video senders"? "Security cameras"? Aren't those things pretty much endemic all over the UK nowadays? If CCTV feeds trump wi-fi, it appears the Brits may have already chosen not to be a part of the current millenium...
Yet another reason not to allow your government to watch your every move.
I believe that's why spark-gap generators are illegal.
If you use WiFi and you're planning on buying a baby monitor, consider a DECT model (particularly those from Philips/Avent.
DECT operates outside the WiFi frequency bands. Thanks to the same bullshit which resulted in GSM requiring new frequencies in the US, the DECT ranges are slightly different there.
on the other hand, my spark-gap generator seems to really do some interesting stuff to the network
Why in the world would you want to have that kind of voltage anyway, unless it's to show off pretty sparks to your friends? If that's the case, then just refrain from using wi-fi while simultaneously discharging your uberleet spark-gap generator and all will be well.
Ah, maybe you were showing off your spark-gap discharge via laptop webcam! =D
It probably also does 'interesting stuff' to your neighbours' networks, as well as their TV, radio and mobile phone reception.
If you're just looking at the pretty sparks, it would be considerate to put a suppressing capacitor across it...
Looran, you're outdated. A number of recent papers found that interchannel interference is not so dangerous as it was thought, and that in high-density area it can be way less damaging that co-channel interference from adjacent cells.
Bean.. that's not very punk.
Surely the non-stop broadcasting of my particular taste in bad music, over every available frequency and arespectable range (and all for free, mind you) more than makes up for the loss of a little internet by my local community.
They'll be so happy, I can't wait to see their faces.
*glee!*
Time to make the move to 802.11A
I read "I've got WiFi and a baby-monitor in my tiny London flat and I can't say I've ever noticed the issue -- on the other hand, my spark-gap generator seems to really do some interesting stuff to the network" and thought the spark-gap comment was "witty" rather than "statement of fact".
Cory, do you actually have a spark gap generator or was that simply pointing out that this problem isn't a universal truth?
I'd like to know how much OfCom spent to discover the issue of RF interference.
I've got an old wireless phone that can reliably kill any wireless networks within a 30-foot radius. I think it's kinda neat, actually.
:)
What are babies doing on the internet, anyway?
This is some interesting stuff on wireless and radios… It discusses WiFi standards, Adjacent Channel Interference (ACI) and what works when trying to get any sort of density and such out of APs, bridges and mesh networks… Not really to solve any particular problems you have, more like background stuff… It really illustrates that the strength of a signal is the inverse square of the distance and that goes for noise too…
Surprisingly enough it shows that even 802.11a has lots of trouble with interference between widely spaced channels when the antennas are not very far apart…
http://www2.informatik.hu-berlin.de/~nachtiga/sar/Channel_Orthogonality_IWCMC_08_talk.pdf
http://www2.informatik.hu-berlin.de/~nachtiga/sar/Adjacent_Channel_Interference_IWCMC08_PID653269.pdf