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How Best To Deal With WiFi Interference?
marciot writes "I live in a condominium where I get interference from my neighbors' WiFi. I understand that 1, 6 and 11 are the only non-overlapping WiFi channels, but how does this translate into real-life best practices? When you must overlap, is there a 'good' way to do it? With nine access points, for example, is it better to have three APs each on 1, 6 and 11, so that each completely overlaps with only two others? Or is it best to distribute those APs across nine channels such that they only partially overlap others (but potentially overlap more APs in total)? Do use patterns affect interference? For example, is it best to overlap a channel with multiple APs that rarely transfers data, or to share a channel with one person who downloads torrents 24/7? Does maximum data rate affect interference or robustness to interference? I found out by accident that setting my access point to '802.11b only' mode appeared to give me a vastly more reliable connection that leaving it in 'mixed 802.11b/g.' Is this a fluke? Or does transmitting at 10 Mbps when everyone else is using 54 Mbps (for their 3 Mbps DSL pipes!) give you a true advantage?"
Increase the power. Then only your neighbours will have interference problems.
Go back to wired, if you can. Really, you will enjoy the speed increase.
Worked for me. Don't need MIMO-compatible clients to get some benefit either.
Also, careful placement of your hub can help - minimising obstacles between the hub and the target devices, away from sources of interferece, that sort of thing.
If all else fails, use a cheap mimo hub as a repeater.
The 5GHz band has been basically forgotten by the mainstream. This is your chance. Equipment supporting 802.11a is a little bit more expensive and 5GHz doesn't work so well through walls, but other than that it's pure upsides.
Finally! A year of moderation! Ready for 2019?
I detect five AP's here, mostly from my neighbours and I still have a really good connection with my own wireless router. I haven't had a problem with interference at all, even when other PC's working in the same channel.
All the AP's occupy another channel (except 6), so the four channels I see are 1, 4, 6 and 9. My own AP is also in 6. So I guess the best solution is to spread them.
Also, and I don't know wether I could work, but you could use channel 64 ( 5.32 GHz ). Most likely, nobody is using that one but maybe your router will not support that. I know mine does.
As long as there are slaughterhouses, there will be battlefields.
If there's lots of 802.11b/g networks around you on the 2.4ghz band, and probably a lot of other 2.4ghz non wifi equipment (lots of wireless cameras use an analog transmisssion on the 2.4ghz band for instance), why not try using 5ghz 802.11a instead?
I can't detect any 802.11a networks here other than my own, so i get much better performance than on the crowded 2.4ghz bands.
http://spamdecoy.net - free throwaway anonymous email - avoid spam!
They will increase the signal power you transmit in a particular direction. They will also reduce the amount of power you receive from your neighbour. Be careful that the directional antenna's don't cause you to exceed legislated limits for EIRP.
As others have suggested, MIMO will also help your cause. MIMO resolves antennas in space, which means that once the MIMO receiver has completed its channel measurements it can reduce the level of interfering signals based on their physical location.
You can't trust what you can see in the wireless network list to be an accurate representation of the noise level.
As another poster pointed out, the re are plenty of other devices that mucks up the signal in a condo. For instance, in my previous flat some caring neighbor bought a wireless surround system and since he was on the dole he pretty much watched TV all the time he was awake. And his sleep pattern was plaid.
The big problem with these automatic systems is that some of them will dynamically allocate a channel for itself when it is turned on and any channel you have previously chosen might be garbage now.
You can find autodetecting systems for wireless, but you might have to dig around a bit to find them.
Me, I use to hop channels and instead of trusting the channel strength and such I run a ping to a known host outside for each channel and then select the one with the least interference. But if your neighbor gets a noisy microwave or an anarchistic stereo, that could become a rather tedious hobby.
You can minimize interference, but don't expect too much.
First, I don't know what type of antenna's you use, but escaping from vertical polarization (which is 'default'), to horizontal one.
Difference in signal level between these two are 20 dbm. So, if you'r getting signal level from your neibh. -70, you will be getting -90, which will greatly improve your wifi stability.
Next, use channels that have lesser bandwidth consumption. It's not important how many ap's are on one channel, it's important how many data frames are going in and out on that channel.
I tested few days ago, my wifi nodes are receiving data from 3 channel bellow/above me, so cuz I use 11, that means I get data from channel 8, but not from 7 that much. Some packets get through, but that's nothing. Which means, if there's traffic on channel 6, you can safely use channel 9, and you won't feel interference blocking you.
Changing data rate, means changing signal modulation. If you use G or A(if you can, use 802.11a), OFDM modulation kicks in, which from my experience deals better with noise. Latency is far more better then on any modulation of B.
So, try putting your devices on G, then fix the rate to 11mbps.
Basically ... there's no real escape from noise. I'm dealing with it for years now, and I'm getting sick of it ... even polarisation changes aren't effective anymore. That's why, I recommend to switch to 802.11a, there's more then 30 non overlaping channels.. or go above/bellow frequency range. Like .. channel 15 on 2.4. It's possible to do.
ok this is not legal in the USA, but it doesn't require you buying anything new. which is why I like it.
1. Flash your wifi equipment with firmware meant for jap versions. that enables the 2 extra channel's above ours.
2. ???
3. PROFIT!
Then you can use channels 12 and 13, which will have a touch less interference
Hack your neighbours access point, turn wifi off and change all the passwords. Bonus points if you can upload custom firmware with different factory password so that even reset doesn't grant them access.
This
From my sofa, iStumbler shows 15 different networks, all at 2.4Ghz. Switching to an AEBS with 802.11n at 5 ghz made a huge improvement for me. YMMV.
802.11n also supports the 5ghz band.
Oh, wait, no it doesn't...you have to guess.
No sig today...
I spend a lot of time in hotels. When I have problems getting WIFI was it always form interference. I have solved the problem by using external USB adapter (with a 12ft USB cable). Relocating the antenna (adapter) is usually all that is needed to solve the problem. In extreme cases I need to use the "foil sheet". I keep a sheet of aluminum foil in an 8.5x11 plastic sleeve in my laptop case. The sheet will block WIFI from one direction, and make a USB adapter that is directional.
What's the reasons for using the older "A" (5GHz ODFM) technology instead of the still-draft (2.4/5GHz ODFM with MIMO) technology?
I've googled and saw many "G vs N" articles, and some technical info on the 5GHz bands, but ... let's just say, one good explanation from an experienced Slashdot writer, is far better.
Put 3 access points on channel 1.
Put 3 access points on channel 6.
Put 3 access points on channel 11.
Nothing at all inbetween as that will destroy the communication on these channels.
If you put the wifi-ap's on the same channel, they will recognize each other and only transmit when the medium is free. Thus the packages will get through although there are some negotiation.
If you spread them on channel 1,2,3,4,5,6,7,8... they will not be able to see and talk to each other, they will only see high background noise. Thus they will start to transmit and really interfer with each other. Large packets will all the time be destroyed and require re-transmission which does not really help up the bandwidth problem at all.
Try to use the highest common standard all basestations/clients understand as they deploy more advanced protocol techniques.
I don't know exactly what a 'condominium' is in America but if running ethernet isn't an option it might be an option to try a homeplug network device?
I have my ADSL router downstairs but all my PCs upstairs with 2 x 200mbit Devolo Homeplug devices taking the ethernet through my power sockets and I've been much much happier than when I tried to WIFI to downstairs.
Get Homeplug devices with good encryption and make sure you set it up to use it and you'll do well.
the dude asked how he can optimise his existing wireless solution - not whether he should buy new wireless hardware or switch to a wired network.
(clearly im not answering the question either... but at least im not karma whoring and trying to pose as an answer)
Example: Netgear WNHDE111
Bonuses:
--Whizzmo
Talk to your neighbors. Pick the AP with the highest wattage, unplug the rest, grab a 15dbi omni, form 1 single larger network, and everyone share 1 internet connection. You'll all save a few bucks too.
How much better? If you're using one fifth of the bandwidth over the same channel, you can withstand a noise level that's five times higher. At least in theory.
If you don't need the bandwidth, just use 802.11b.
Reality is the ultimate Rorschach.
I thought that IEEE 802.11n used OFDM to help prevent this sort of thing from being a problem?
XML is like violence. If it doesn't solve the problem, use more.
The answers are generalities, since each situation is unique. As others have already said, the real solution to your problem is spelled "5 GHz." However, if we add the condition that you must remain at 2.4, here we go:
In general, the former is best. Most site planning is done this way, with the (I hope obvious) additional condition that the cochannel APs are physically separated as much as possible.
Yes, use patterns affect interference. In general, the former is best, since the channel has more idle time available for "your" data.
Maximum data rate has a major effect on interference robustness. As you've found, in general lower rates can tolerate higher levels of interference than can higher rates. More explicitly, there's a range of interference levels (low) at which both will work. Above this is a range of interference levels (medium) at which the low rate will work and the high rate won't. Above this is a range of interference levels (high) at which both will not work. What you've found is that you're in the medium category, in which your system will work at 10 Mbps in the presence of interference from your neighbor's 54 Mbps system, but your system will not work at 54 Mbps in the presence of the same interference.
A second phenomenon may also be present, one specific to the 802.11g standard. To make it backwards compatible (i.e., so that an 11g AP would work in a network having one or more 11b devices) the 802.11g folk mandated a behavior in which an AP checks first to see what's around it. If it hears an 11b device, it downshifts into 11b. This, of course, slows the entire 54 Mbps network down to 10 Mbps. You may be experiencing a side effect of this -- all the checking and upshifting and downshifting takes time, so if 11b devices come and go frequently (as they might in your scenario) the net throughput can be less than if one stayed at 11b speeds in the first place.
One of our client wanted to have wireless clients from the start. It was easy, but now the number of clients are spreading like rabbits and currently I have to use 5-6 AP to cover the whole area.
What is the best configuration in this case?
Love many, trust a few, do harm to none.
Get ath5k or rt73, linux, and run off-frequency. I can run at 2192mhz w/o problems w/ rt73usb right now... just don't tell the FCC.
Do you and your neaghbors all need your own seperate LAN's ?
If all you are doing is a bit of surfing, it might be worth knocking on doors and offering to set up an open access point. Of course, some will need a private LAN of there own, but most will probably jump at the chance to split the ISP bill with you and reduce the interferance.
Remember, they will be suffering with crap wireless just as much as you are. If you are a geek, you will be the one in the best position to help everyone out.... and meet your neigbours for a beer in the process
Anyone quoted by a reporter knows how little they understand
Don't believe what you read is the truth.
In the first part of my comment, I said, "...the cochannel APs are physically separated as much as possible."
This, of course, is true only both APs are part of your LAN, and isn't really appropriate here. (*sigh* You can take a horse to "Preview," but you can't make him think.) In your case, one might consider the opposite strategy: Place your cochannel AP as close to your neighbor's as possible (e.g., on the other side of the wall from his), and use a directional antenna (pointed into your place, of course). This would tend to produce a constant signal-to-interference ratio throughout your place, hopefully high enough to be useful, while not producing interference in your neighbor's place high enough to corrupt his network. I guess while you were buying directional antennas you could buy one for your neighbor, too, which could only help matters.
Of course, the contrarian view is to place your AP against the wall with its present antenna, and force your neighbor to worry about interference, buy antennas, etc. :-/
Use NetStumbler http://www.netstumbler.com/ to determine the signal strength of all the other access points to see if any of the channels will have low interference. Although you may see lots of access points, they could be very feint signals because beacon frames are short at about 50 bytes (compared to 1500 for a typical data frame) so they're a lot easier to receive. The strong signal from your own apartment/condo should be able to drown out the noise from all the feint AP signals but if the people next door to you have an AP then it could slow you down so that's why you need to check for strong signals with NetStumbler.
Title correction: Pick the one with the LEAST interference
At minimum you increase both noise from the AP and signal, and your ratio stays the same. If environmental noise is a much larger factor, then increasing AP signal will improve your SN ratio.
Connect to your neighbor's unsecured wireless routers, log into the web administration panel with the default password, and set them all to channel 1. There will be one neighbor who secured his, and he will be using channel 11. Set yours to channel 6. No more problems!
Go green: turn off your refrigerator.
Install a bigger antenna. Oh 12 db gain should do nicely.
Nuff said.
As previously mentioned, try switching to 5GHz if you can. It won't go through walls, which means that you need to locate the AP carefully to make sure you have coverage where you need it. But it does mean that your neighbors APs, if they switch to 5GHz as well, won't interfere as much with you.
Run your APs at the lowest power possible to still cover where you need, and have your neighbors do the same. Many people want to push the power up and up when they have problems. But that just leads to an arms race and more interference.
I only use the non-overlapping channels.
I use 802.11g on 2.4GHz, using the theory that sending the data in a smaller time will decrease the overall contention. However, 802.11b may be more robust.
If your systems have a setting for "Interference robustness", try using it.
Try setting the RTS threshold, possibly to a very low number.
You might want to try setting up an AP on two or 3 of the non-overlapping channels, with the same ESSID. Your systems *MAY* switch from one to the other if they run into interference.
See this URL for more information on what I've had success with: http://www.tummy.com/Community/Articles/pycon2007-network/
Sean
Sean
put dd-wrt on your access point if possible then up the Xmit power as to stomp down the other access points with a more broadcast power
Cover all interior walls with tin foil. Seriously. As an added benefit, you will have mirrors everywhere so that you can see when you have left "your barn door" open. It's also great when making out with your signficant other.
Some other things you "could" do (but not as fun are:
1)Use some of that paint that blocks cell phone calls. (works for wifi also)
2)Use magnetic paint (has iron oxide in it) and then put a coat of "normal" paint for the color of your choice.
Didn't I see a post on Slashdot at one point about a paint that mimics a faraday cage? Paint that on the inside of the outer walls of the house...
Mind you a house will never be a complete cage, but it should limit the external noise and minimize the external wireless signals...
I have not actually seen any of this paint on the market but I haven't looked either...
If this is set up in an apartment you may not have this option however (and it wouldn't help at all for anyone living above/below you unless you also painted the ceiling and floors))...
--- When you start with the conclusion that you want, then throw out any facts that don't agree, is it true?
- what are the most busy bands in term of actual usage.
- what is the strength of the interfering AP's.
- what is the actual SNR for your computer in the locations you work normally.
having this information you can use some of the methods above:
- directional antenna
- selecting the correct frequency
- setting the power
changing to a band can be an interesting idea but its more expensive than the others.
Daniel
http://design-to-last.com/
If you're wireless is being difficult and you're unable or unwilling to run cable, think about using Homeplug bridges.
Homeplug is basically ethernet over the power lines in your house. They usually sell the adapters in pairs which act as a bridge. So you could have one adapter in the office with the modem and your access point, and another in your living room going to a switch for your xbox/ps3/wii/laptop. So it basically turns any electrical outlet into a potential bridge point..
I've got two sets of Dlink's DHP-301 and they're fantastic. (It was the first product I'd bought in a long time that 'just worked'). Most adapters also support encryption if you're worried about anyone watching the traffic since you might be on the same electrical circuit (I don't remember what exactly its called).
The obvious solution is to line your walls with tin foil, of course! ;)
-Ghostis
Computer Science is all about trying to find the right wrench to bang in the right screw. -T.Cumbo?
If you have Linksys WRT54G wireless router and have flushed it with DD-WRT Firmware, you might be able to increase Xmit power of your wireless transmission to effectively suppress any interference. Now, the idea is to not go overboard and piss the neighbors off by making it so strong that it suppresses reception of their own signal in THEIR own apartment.
Good ideas all around. Let me add something related: You will never get the full 11Mbit, 54Mbit, 300Mbit, what-have-you. First, wifi is a half-duplex medium like 10Base2 (not T, 2) ethernet. Second, multiple stations transmitting between each other in AP mode have to have the traffic transmitted to the AP and the AP sends it on to the other station. This because there might be "over the horizon" problems: The AP can see A and B but A and B can't see each other. So on an otherwise empty network you'll get maybe slightly more than half the advertised number, ideal case.
And yes, 802.11g will degrade to b if it sees any other b station. Good way to annoy the neighbours; ten to one they won't understand what's happening.
The CCC congress NOC always asks to NOT use any b because of that.
Personally I'd go for strategically provisioned cabling if at all possible and not too inconvenient. 100Mbit FDX ("200Mbit aggregate bandwidth" in marketingspeak) can be had nowadays without even trying, gigabit is getting easier by the day. 802.11a and a free channel is the first station for wireless. If you have to have 2.4GHz wireless, do a site survey, know the field, and then you can bring on the box'o'trix detailed in the other comments.
And no, don't up your power just because or try and use channel 15 or -3 or what-have-you. There's no need given all the other options and could lead to nasty unforeseen side effects. Can you tell me who uses and under what conditions the neighbouring bands are used without looking it up? If you have to ask, you don't get to do that kind of stuff.
Although it's not a long term solution if masses of people follow your lead I can tell you moving to something OTHER than the 2.4Ghz spectrum range made a big difference for me.
Netstumbler is a great little program. I'm not sure how the author of the article could control how other people set up their routers (yes he could ask but would people actually cooperate?), so at least he could pick the channel with the least competition. A technically inclined person could also install this and increase the transmission power over the default. Swamp your neighbor's wifi signal! Impress your friends!
I have not actually installed or used this, since my wife would kill me if I accidentally bricked our router.
I have mod points. The reign of terror begins now.
I just change my timezone on the AP to Japan or something and then set it to channel 14 :)
The worse yet: slice off the penis entirely using only a sheet of paper.
I tried this, but got nowhere. Was it a mistake to use a sheet of toilet paper for this purpose?
Shit, I just lost the game.
"What if I got hit by lightning while walking with an umbrella? Ban umbrellas! Fight the menace of lightning!" Doctorow
The 2.5 GHz frequency range is used by a number of consumer products: WiFi, Bluetooth, microwave ovens, cordless phones and wireless baby monitors. This band has been divided into channels which are separated from each other by 5 MHz (see: http://en.wikipedia.org/wiki/List_of_WLAN_channels).
Different transmission strategies used by these different products may require more than 5 MHz separation to prevent interference. We see this in television channel assignments in any given region. Some broadcast regions were assigned even numbered channels and adjacent regions were assigned odd channels, hence old VCRs and TV based video games allowed you to select either channel 3 or 4 for the television connection. One of these two channels would be free of a strong local broadcast signal in any given area.
The FCC in the US recommends that WiFi signals be separated by 25 MHz on channels 1 - 11, so correctly set up WiFi devices only use channels 1, 6 or 11 with 6 being the default in North America. The regulatory bodies in the European nations recommenced only 20 MHz separation on channels 1-13, so they should use channels 1, 5, 9 or 13 (see: http://en.wikipedia.org/wiki/802.11g).
So, why not pretend we live on a different continent and set up shop on an intermediate channel like 3 or 8? This would only maximize the amount of interference we both create and receive. Someone elsewhere in these comments correctly pointed out that the only thing that really matters is the amount of traffic on adjacent channels - not the number of stations that you can see. If most of you neighbors are technically challenged and leave their routers set to defaults but only check their email from time to time it will be less of a problem than one strong signal from a user who is streaming media and running torrents.
In the absence of actually measuring traffic, look at the channel assignments of local routes and choose the least used of 1, 6 (unlikely) or 11. BTW: generally, when people change their router, without checking local usage, they tend to move upwards - channel 11 - so you should choose channel 1. John T
...because there won't then be a wireless access that you can change their passwords with!
The Cisco 1200 series I use put out 100mw at 802.11b rates and only 30mw at 802.11g rates. This partly explains it's better range/penetration.
When I install WIFI networks for hotels I generally use 802.11b radios in the Cisco APs for this reason (there Internet connection is way slower than 802.11b anyway).
In the field I frequently find that locking the radios into 11 or 5.5mbps rates will improve connection stability.
Other things to try, low rts threshold and a low fragmentation threshold.
See if neighbors will coordinate, put all the 802.11b stuff on one channel and use the others for 802.1gG stuff.
I can see a dozen 802.11g networks around us, but I'm the only a/n 5GHz network that I can see. It doesn't penetrate walls as well, but that's good enough in our condo. (The upside of lower penetration is that it's harder to intercept, and we interfere less with any neighbors who might move to 5GHz.)
We use a/n because my first-gen Intel Macbook does a/b/g but not n.
In no particular order
The best way to avoid interference is to not use wifi at all. You can get wifi around the place if you use a ethernet-over-power adapters. This nice things basically allow you to plug in an ethernet cable into your outlet at the end by your router/switch/firewall/whatever then at another outlet by where you will be plug in your laptop. This gives you similar freedom of movement as wifi with the trade-offs being no wifi interference for goood throughput at the expense some reduced mobility.
If there is no way to keep all involved APs completely isolated, you want to consider who is using the most frequent bandwidth and how many clients are talking to each AP. There is only so much RF capacity and try to the avoid the more populated channels if possible. If your AP and client(s) can see the other APs and their respective clients that will be the best so everyone can talk in harmony otherwise if your AP can see you and other clients but your client cannot see the others then they are likely to step on each other without even knowing it.
Another thing you can do that will potentially make it a little more cumbersome to use depending on how you are actually using your wifi is to get directional atennas instead of omni antennas at the AP and your client. This will help to extremely reduce the amount of the interference you and your AP will see as you can only "see" the interference if it is coming from the direction your antenna is directed vs thru the walls to the side or what have you. This obviously does not allow you to as easily just roam around your place.
If you can get your APs and client(s) with more powerful transmitters and antennas with higher gain you will also be better off.
Or you can coat your neighbor-facing walls with the anti-wifi paint
ZERO ZERO ONE ZERO ONE ZERO ONE ONE! Just brushing up for my next big invention: Ethernet over Voice (EoV)
I found out by accident that setting my access point to '802.11b only' mode appeared to give me a vastly more reliable connection that leaving it in 'mixed 802.11b/g.' Is this a fluke?
No, because the 802.11b signal requires less bandwidth than 802.11g. Since the channel spacing remains the same, this means that you've got more "space" in a given channel to fit that bandwidth.
A not-totally-inaccurate analogy would be that 802.11g is like writing smaller to fit more information on a page - sure, you can write more in the same space but it's harder to read, especially in a poor light or if the ink is faint. If you use 802.11b then the writing is bigger, and easier to pick out in a noisy background.
I do not respond to cowards. Especially anonymous ones.
set up a WDS network and put and put a bunch of routers everywhere?
CSMA lockdown!
Only run 3 networks on channel 1, 6 and 11 (and 14 if you want, it is actually spaced as far as 1 is from 6 etc etc, regardless of channel number! Although may be illegal, unless in Japan). Running more than one AP on the same channel in the same area will cause CSMA lockdown and you will be disappointed.
Changing your beacon interval to 101 keeps your wifi networks beacons perpetually out of sync with your neighbors wifi noise. The problem every one is having is errors like unable to find access point, connection error, and being dropped from your access point. This single change makes all of the other tweaks esoteric and uneccessary. Access points know how to deal with noise and interference. Access points do not know how to deal with an excessive amount of lost beacons. And they shouldn't.
http://freegnu.blogspot.com
http://identi.ca/freegnu
Leave the WIFI on, fix the channel to the one you don't you. They won't replace it then. But then for the finishing touch:
Shart using it to share movies and music and let the MPAA and RIAA go sue them into bankruptcy.
Fight Spammers!
If there are that many APs in reach of you causing that much interference, then it's likely there are at least 3 of them with no encrytion whatsoever, which means the owner likely doesn't even know how to check who's connecting to it anyway, so turn yours off completely and just use your neighbors' instead, for free. Think of all the money you'll save not having to pay for broadband!
He just needs to tinfoil his apartment. Forget the hats. :)
Don't forget there ARE non technical solutions.
-- Programming with boost is like building a house with lego. It's a cool but I wouldn't want to live in it
With all the interference at 2.4GHz or possibly even 5GHz, a better solution would be to rely on light waves.
Ok seriously, go with 802.11a or 802.11n operating in the at 5.0GHz frequency band.
w00t
Most plebes don't know how to tweak their north american firmware/drivers for channel 14, but us 133t /. d00ds do. The hardware all supports it (tell it you're in Japan), and 14 is far enough from 11 that you're only getting a bit of overlap, and only on one side.
Just don't tell the FCC.
Do daemons dream of electric sleep()?
In my old apartment my laptop offered me the choice of 45 access points to connect to, and my wireless still worked fine - I did set the channel away from the highest signal access points...
Is a different band.
Yeah, I'm switching to 5 ghz also. I also see 15 networks on 2.4 Ghz, and only one guy at 5 ghz. Obviously switching will solve the problem.
One reason is that there's a potential X-Y problem in the poster's question. He's asking how to do X, because he wants to do Y, but if he really wants to do Y there's probably a better way to do it.
I live in an apartment. I have had a WWVB 60Khz Nixie clock for a couple of years. Early October 2008, it quit getting time updates. Seems there is enormous nighttime interference out there these days. I have a different audio WWVB radio and that now only plays static. Sometimes in early morning just after daylight, things are pretty good. I suspect its from nearby lighting assemblies on a nearby interstate.
HELP!! Any suggestions for a RF detector that can target my 60KHz interference? How to make one; a) that shows direction and b) detects 60Khz?
Also I need to get my local radio club to help with an oscilloscope to create a better 60Khz tuned antenna. The current tiny antenna is directional and in a non helpful square box.
Thanks,
Jim
You can't really reduce or eliminate interference very well without a lot of effort (like special wall materials that block wireless signals), but you can work around the interference well enough by using a wireless spectrum analyser to determine where the interference is the weakest. Me, I use a very cheap (and limited) spectrum analyser like device called 'Wi-Spy'. This is basically a wireless reciever tuned to the same frequency range used by 802.11g wireless networks, combined with software that graphically illustrates the wireless signal strength throughout that spectrum. Using the data gathered with this tool I was able to configure my wireless router to use a channel which had the least ammount of outside interference in my area. This has worked great for me.
- James
I have a suggestion for you, try running down steep stairs as quickly as you can, while thinking about each step. Darwin will take care of the rest...
The Tomato firmware lets you scan each channel and identifies all wireless networks (including hidden w/o ssid) before you pick the channel you will use. You can then pick the clearest looking channel. You can also try the Windsurfer http://www.freeantennas.com/projects/template2/ which is an aluminum foil antenna you make to better direct your signal.
cause most routers default to channel 6, so move yourself to 1. Seriously.
I have been getting a lot of calls for this recently. I had a guy who was 6ft, LOS from his router w/ interference issues. We bumped him down and he's been fine ever since. I had another client who everytime they picked up and turned on their wireless phone, the internet would drop, and when they reconnected the wireless network the phone would drop cyclicly. Same issue, except, they had about 13 discovered networks using the "windows" tool. Now he makes phone calls, uses the internet, and we lined his walls w/ lead paint from china to seal in the signal.
(That last bit was a joke)
How much is your data worth? Back it up now.
How Best To Deal With WiFi Interference?
Find out where the bastard lives and what equipment he has that's causing the interference, and then send a couple of your boys around to help him take it apart.
The higher the technology, the sharper that two-edged sword.
To answer the question, there are two things going on.
One is the interference from the transmissions, which lowers the signal-to-noise ratio if you are on the same (or an overlapping) channel. The lower that gets, the more errors and the worse your performance. So to combat that, you can either use a different channel (1, 6, and 11 are probably the best to try, but you could just measure your performance on all of them and use whatever is best), or as you said force the use of a lower data rate (a lower data rate is more tolerant of low signal-to-noise ratios). Obviously there's a trade-off between having a more reliable connection with a lower data rate and having an unreliable connection with a faster data rate.
The second issue is channel reservation. Because of how 802.11 works, you can end up with a situation where one user is getting an unfair amount of bandwidth by basically telling the other users to be quiet. There are various settings which you may have access to depending on your router, such as the RTS/CTS threshold (try setting it to a very small value, may be better or worse depending on the situation), the backoff window size (which tunes aggressiveness), preamble (a long preamble helps when there is interference), etc.
So yes, just try different settings and you should be able to get an improvement.
To me, it's indicative how how we sort of rushed wireless to the market, first there was WEP and if you've owned much wireless hardware, it tends to be pretty crappy. Then once everyone in your neighborhood is wireless, your cordless phones start acting crappy and your network tends to slow down.
There is no easy solution, you can try to find open channels that have less interference but the technology just fundamentally isn't designed for dense deployment. Really, the solution is that everyone needs to be wired if and when they can be and then we sort of need a couple of wireless standards, one is for convenience, when you want to just take your lapper around the house, these convenience channels need to be lower power. Then for the necessity channels, where you have no legitimate wired option, they need to start using DECT like technologies.
YOu can try to over power them, that works until they start doing the same. You're just kidding your self if you think it's possible to make a Faraday cage, do you know how small wifi waves are? They can make it through just the tiniest little crack or sliver of gap.
If all the radios around you are tuned to non-overlapping channels (1,6, 11) and you look "down the spectrum through time" you have 3 distinct bands that all the radios can tune and demodulate easily. When people use an intermediate channel like 3, it doesn't get them away from the channel 1 signal so much as it fills in the spectrum that makes the neighbor channels tunable. Intermediate channels just interfere with 2 channeles, it doesn't get you clear of either. Tuning is difficult when the spectrum is filled out without separation, it's like trying to listen to a distant flute concerto while you're in the shower.
The best way I know to really tune your wireless environment: Run Kismet on a linux laptop in one window, and run Wi-spy Chanelyzer in a vmware unity windown next to it. The USB wispy works perfectly in a virtual machine, and you can correlate the Kismet traffic to the radios you see in the spectrum graph. Makes it real obvious what the problems are, and what the best solutions will be, assuming you have good solutions available. In a crowded environment, the unregulated microwave spectrum can be a noisy mess, but until you see what a radio sees, your actions are likely to be little better than random changes.
By the way, you can't really trust your wireless card to give you a good picture of the spectrum. It misses all noise that is not its own protocol, it tunes 1 channel at a time and scans and samples slowly, and even when it recognizes a signal the strength that it reports to the driver may not be calibrated in a meaningful way.
Do what I do: crack your neighbours WEP and then turn off their wifi. I had about 20 networks around my flat. I then left my computer on for a few weeks and cracked the WEPs since everyone are running standardrouters with only WEP encryption. After that, logging on to their APs and disabling wifi was a no-brainer. I'm now enjoying a lot better reception and a lot less interference.
If you're in a condo with microwave-transparent walls and lots of neighbors, your best answers are
1) Wire it and
2) 802.11a or 5Ghz 802.11n. These have more channels, penetrate walls more poorly and your neighbors are less likely to be on it -- especially the 5.1-5.2Ghz channels, which are not used by cordless phones.
Yeah, the equipment costs a bit more. But actually having useful wireless is worth it.
In any given modulation scheme used in 802.11, the lower speeds are more resistant to interference than the higher speeds. 802.11g uses two different modulation schemes, DSSS and OFDM. Theoretically, OFDM (used only in G) is more resistant to interference than DSSS (used in B), so reducing the speed but leaving the AP in G mode should do better than putting in in B-only-mode. This depends on your AP supporting that feature of course.
If you have to share a channel, it's far better to share one with an AP which is rarely used; most of the time, such an AP will not be transmitting anything and the spectrum will be available.
With 9 APs, you're pretty much screwed; no matter what you do you'll have major overlap. With 4 APs, it has been found that 1,4,7, and 11 works reasonably well, but you'd need control of those other APs.
Other answers (which may be illegal, immoral, impractical, or fattening)
1) Use higher-power APs (not hacked, but those designed for higher power) and cards.
2) Use high-gain directional antennas (a high gain omni may be practical on a single-floor condo)
3) Use channel 14 (illegal and generally requires firmware hacking to get 802.11g on it, as that's illegal everywhere)
4) Microwave-absorptive coating on walls/ceiling
5) Hack into neighbors APs and move them all to channel 1, then use 11 yourself.
Change the frequency you're running on to one that your less-technical neighbor can use.
Problem solved.
I want to delete my account but Slashdot doesn't allow it.
If you live in a condo, there's a condo association.
If there's that many APs, maybe the association should look into building-wide WiFi. Depending on what everyone is paying now, it might be cheaper than one-by-one solutions.
I'm not sure how you deal with inter-unit security. Ideally, you want each unit to only be able to see other computers in that unit, but let someone wander the building with their laptop and still be on "their network." I'll bet there's a way, though.
The preferred solution is to not have a problem.
None of you come up with the best solution, albeit somewhat illegal.
Run Japanese firmware at channel 14. Low interference there.. I should know :)
This is the only real world solution I had, unfortunately I don't know how legal it was.
I was in a Apartment building, and all channels were being user/overlapped. I kinda cheated, probably was breaking law too.
My router had a country/location choice, I choose Australia, that game me I think channel 12 and 13. I choose the unlucky 13. All was well.
Do at your own risk though.
There are ISPs that are happy to have you share bandwidth. Another poster mentioned Speakeasy; I'm using sonic.net. Some of them have deals where the roaming user pays for an account and the wired user gets credited for it, and typically the ISP gets to sell you a faster DSL link so you're all happy.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Thanks - that was a useful post.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Nobody has mentioned the potential issue with early-draft 802.11n access points and routers that default to 40MHz channels (or Draft 2.0 devices that have been manually configured by their owner to use 40MHz channels).
802.11n supports both 20MHz wide channels and 40MHz wide channels, but use of 40MHz wide channels in the 2.4GHz band will in general cause so much interference that it will knock 802.11b/g (which uses 20MHz wide channels) offline. Draft 2.0 802.11n equipment is required to detect nearby 20MHz channel use and automatically prevent 40MHz use (the "good neighbor" feature), but the algorithms are not perfect. In fact, the WiFi standards body is debating whether to make the 40MHz channels not just non-default and a "good neighbor", but prohibited for 2.4GHz. Of course marketing wants to be able to claim the higher bandwidth that 40MHz can provide (300Mbps versus 144Mbps), but many technical people recognize that even with the "good neighbor" protection there will still be interference issues with 20MHz equipment.
So, the solution may be to track down your neighbors and convince any with 802.11n equipment to explicitly select the "20MHz-only" setting for the 2.4GHz band. And any of you with 802.11n equipment reading this, please set that yourself!
As previously mentioned, try switching to 5GHz if you can. It won't go through walls, which means that you need to locate the AP carefully to make sure you have coverage where you need it.
Agreed. The 5Ghz spectrum always seems so open and free. Not to mention that 802.11a allows for dozens of *discrete* (read: non-overlapping) channels.
To help with the "not going thru walls well" problem of 802.11a, I've found that a simple reflector placed on every antenna of your WAP can boost your signal by 10 - 12 dB (in a single direction) -- This is enough to make it through walls of a condo. It also helps reduce noise coming into your WAP as well as pick up the signal from your devices better.
They're very simple and cheap to make, too. Instructions can be found at the Free Antennas website. The designs work great for all Wifi standards.
Do you really want the RIAA MPAA FBI knocking at your door when your neighbor is downloading bootleg music bootleg movies plans to assassinate the President?
If you didn't, you could go to jail.
Of course, it's not like anyone will catch you, unless you do something like confess your crime on the public internets.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
Step 2: ride on FREE internet!
printf($randomline(sigs.txt) \n "-- "$randomline(authors.txt));
-- myself
If your condo association and your internet provider can agree to terms, your condo association can lay out a mesh network all on the same channel.
Whether this makes sense or not in your situation will depend on many local factors, both technical, economic, and political.
I don't think the FCC will let your condo association prevent members or their guests from using the same channels, but if you do it right very few will need their own wifi and those that do can use the other channels.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
InSSIDer is better and updated. NetStumbler hasn't been updated for years. I recall it was due to money. :(
Ant(Dude) @ Quality Foraged Links (AQFL.net) & The Ant Farm (antfarm.ma.cx / antfarm.home.dhs.org).
You are using 2.4 GHz. This is junk spectrum. Not only is everybody using it, your microwave is a giant jammer.
I fought with endless reliability problems for clients, and 5 GHz 802.11a or 5 GHz 802.11n, provided coverage is sufficient, solves this problem almost perfectly. I have no documented cases of external interference at 5 GHz when using access points with DFS.
If you want to stay at 2.4 GHz, you cannot achieve wire-like reliability without ridiculous and/or illegal hardware, but you can do four things to eliminate 98% of issues:
1) Get a more powerful access point. They are all rated for power output, read it! Be sure to add the antenna and radio power outputs up.
2) Get a more powerful antenna. Look at the dBi, and buy from a real company like hyperlinktech.com not some eBay seller.
3) Get 802.11n hardware. True MIMO is powerful, even if your remote client is still 802.11g, it helps, though preferably upgrade the client too.
4) Research the chipsets and vendor systems and make sure you are getting hardware with the best possible sensitivity. There are big variations between vendors and chipset generations.
However, as I said, the only real solution is 5 GHz.
If you go this route, research the chipset and get an Atheros chipset. Preferably, get one of the chipsets where they support 2 spatial streams with both rx and tx radios, but actually have 3 antennas.
Bad news is you will have to upgrade the clients, but if you get Atheros on both ends, I would expect that 5 GHz 802.11n would give coverage similar to 802.11g and when you have good signal, easily exceed 100 mbit/sec.
Channel Deployment Issues for 2.4-GHz 802.11 WLANS
an investigation by cisco into some of the details of interference. over my head in places, but what i followed i found interesting.
in my apartment there were enough people on the default channels that i was unable to connect to my ap from a few feet away. i changed to a channel that looked empty and have had decent connectivity since. i didn't do a follow-up investigation, but came away from the experience with the feeling that it's better to try to fit in the spaces between when there are a lot of people on the defaults.
n.b. this is anecdotal and i am not a wifi expert by any means...
Trianglulation and a Shotgun :)
Get yourself a ham license, some special adapters for your AP from eBay, a 1 or 2watt bi-directional amplifier and a 15.4 Db gain omni antenna. Connect the AP (adapters) to the amplifier to the antenna. Set the AP on channel 1 (just inside the ham band), put your callsign in the AP SSID and 'ave at it. You will no longer have any problems but your neighbors will. If the peasants start an uprising have a trench broom at the ready.
When using my Inverter microwave, the strong WiFi signal is lost. I took a GE Inverter back because of this, and got a Panasonic, but the Panasonic would up also killing the WiFi. Yikes. It is probably not microwaves that are escaping from the oven, but probably a bunch of EMI from the inverter. Surely not ionizing but nasty enough to wipe out the WiFi.
Google HPNA
or HomePower networking. Siemens makes good adapters.
these bridge ethernet over phone wiring or electrical wiring. HomePower has better encryption/security from what little I remember. they're obscure, but you can still buy them.
If it's a condo and you own it, you can wire it for ethernet. The phonebook actually lists companies that will fish the CAT5 thru the walls and install the jacks. It's not super expensive. Ethernet is actually the best solution: fastest, most standard, and adds value to your condo, should you ever try to sell.
Wireless radio is not the only way to solve this problem.
Wireless is convenient for people who don't know DHCP from TCP/IP from NTP. They want to just plug stuff in and have it work as if by magick. Every apartment building and suburban neighborhood has this problem; I've seen 9 wireless works all using channel 1 or 11 in one apartment building.
http://www.cedmagazine.com/pioneer-telephone-taps-ruckus.aspx
I don't have a pickup truck to confirm.
Yah, instead of whoring for Informative or Interesting, you are whoring for Insightful.
Myself? I am going for Funny, here.
No, you can definitely sharpen these enough to be lethal if you're a ninja.
I am not devoid of humor.
Video or it didn't happen. Don't propagate bullshit. http://en.wikipedia.org/wiki/List_of_MythBusters_special_episodes#Special_10_.E2.80.93_.22MythBusters_Holiday_Special.22
Video or it didn't happen. Don't propagate bullshit. http://en.wikipedia.org/wiki/List_of_MythBusters_special_episodes#Special_10_.E2.80.93_.22MythBusters_Holiday_Special.22
Faraday cage
This post is LAW where prohibited by VOID. Prosecutors will be violated.
I found I had problems with poor firmware, basically instead of settling down on the speed that gets the best throughput, just dropping speeds every time it sees packet retransmissions. I don't see other APs at 11, but there's *something* up there that makes a lot of burst noise. (6 and 1 are useless here due to all the access points being down there, so I'm at 11 despite the noise) I ended up *locking* my AP at 48mbit, and one of my more distant machines at 36mbit.. my other machine has ndiswrapper, I cannot set the rate on it, but it autostays at 48-54mbit anyway
If I don't lock the speeds, I found it VERY common for access points (and some cards) to operate properly in B mode, but react to noise in G mode by drop step down from 54mbit to like 1mbit over the course of just 5 or 10 seconds. Then, at 1mbit it sees high error rates (since 1 frame takes so long to transmit it's almost certain to be damaged by noise)... so it stays at 1mbit then. Tragic.
As everyone else says going to 802.11a is better. But, I would try locking your rates first.
The second thing to try, turn on fragment mode. If you, for instance, set it to 550, instead of sending full-sized 1500 byte packets, you'll more or less cut them into thirds. If you have a noisy channel, this decreases the chance any given packet is obliterated by noise, and so increases throughput. However, if you have a clean channel, it increases overhead and slows you down slightly.
Finally, CTS/RTS mode can help if you have multiple machines that all see the access point but that can't see each other (if they can't see each other, each can think the channel is clear and transmit at the same time, so at the access point you just get noise). This is called the hidden node problem. The overhead for CTS/RTS is high, in my case I don't use it because it slowed me down more than it helped. But it's far faster than going to 802.11b.
Final solution... just stay at 11mbit. You should be able to get 600KB/sec, 3mbit cable tops at 375KB/sec at 100% efficiency. I beat the hell out of mine, running GBs of files over NFS and such, but if it's JUST for internet access 802.11b should outrun the cable anyway.
It's easier to stop creating problems than it is to avoid troublemakers. Tragedy of the commons? perhaps. But, if you were to get your ham radio license and transmit at maximum permissible power using ham modes on 2.4 ghz, you could jam the whole neighborhood. Note that doing this intentionally would be illegal.
So, to co-exist harmoniously, what everyone needs to do is this:
1) Filter the broadcasts that Microsoft operating systems are making over the next. They make a lot of noise, and the leaking of such information could be considered a security risk.
2) Turn off your SSID beacon, or set it to broadcast infrequently. Perhaps once per second. Beacons are sent at the lowest data rate, see below.
3) Not quite sure how to accomplish this with everyday routers, but most of the time you don't want to be connected at less than 11 mbps, so why even accept 1 mbps connections? Sure, the signal goes farther, but at a reduced efficiency - which means, it takes longer to send the same amount of data, which means that the band is more congested.
4) There are long and short preambles, sometimes these are settable. But I am going out on a limb here, I can't remember much about the preambles, but shorter would be better.
I know this is 'you should' information, and not a really concise 'how-to', which is what you and your neighbors need. But you're asking for free advice, so maybe you can do some in-depth research and find out how to implement the above methods. Remember, your neighbors are probably suffering too. If you can get everyone in the area to run a router with openwrt on it, then you'll have access to all the settings you'll need to minimize interference.
If you have a FCC Amateur Radio license, then your use of the radio trumps the use of others. They're broadcasting without a license on the basis that they cause no interference to any other signals. They have the burden of fixing any interference problems.
So get your ham license and then claim interference. They can't refuse legally to change their transmission channels if you ask it.
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!
Clearly all you need to do to protect yourself from wifi interference is to surround your entire house/apartment/unit with appropriately sized copper mesh, duh!
Mike gave us that one before wifi was even invented! Course, there might be a couple of small engineering challenges in implementation...
perhaps I need more sleep...
err!
jak.
check out hawking technology (specifically hwu8dd) don't let the looks fool ya! it gets me internet anywhere. their boosters work great too, 250mw with a high gain directional antenna if you need it! all excellent equipment (i've used) where every other adapter fails! Everyone I know that travels has one! they even have a wifi detector / high gain directional antenna all in one!
I can't answer all your questions, and it seems no one else has either.
However you already know that APs cooperate when on the same channel, so the best thing you can do is get your neighbours to change to non-overlapping channels. I have done this by visiting my neighbours, explaining the problem and helping them to change channel. Result: reliable connection. You might prefer to get the concierge to advertise good wifi practice.
If you end up configuring all your neighbours then you get a chance to distribute signals intelligently: ie, reserve two channels for big downloaders, and the other reserved to ordinary users (even a single channel is more than enough for 20 people browsing the web).
Non-standard wifi and N: generally speaking it is best for these devices to be configured for g or b and disable the fancy feature which stomps on signals and acts like interference. They will do better not just you. Disable anything out of the ordinary.