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How Best To Deal With WiFi Interference?

Soulskill posted more than 4 years ago | from the all-it-takes-is-one-EMP dept.

Wireless Networking 451

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?"

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451 comments

Hack your AP (5, Funny)

Anonymous Coward | more than 4 years ago | (#26495409)

Increase the power. Then only your neighbours will have interference problems.

A simpler method (-1, Offtopic)

Anonymous Coward | more than 4 years ago | (#26495415)

THINK ABOUT YOUR BREATHING

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There are also MANY variations of this. For example, think about:

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SWALLOWING SALIVA!

HOW YOUR FEET FEEL IN YOUR SOCKS!

In conclusion, the THINK ABOUT YOUR BREATHING troll is simply unbeatable. These 4 words can be thrown randomly into article text trolls, into sigs, into anything, and once seen, WILL FORCE THE VICTIM TO TAKE CARE OF HIS BREATHING MANUALLY! This goes far beyond the simple annoying or insulting trolls of yesteryear.

In fact, by EVEN RESPONDING to this troll, you are proving that IT HAS CLAIMED ANOTHER VICTIM -- YOU!

Re:A simpler method (-1, Offtopic)

Anonymous Coward | more than 4 years ago | (#26495461)

You fucking fuck! How about this: penis rugburn. There, you're a victim too of imagery. Here's another: papercut to the penis. The worse yet: slice off the penis entirely using only a sheet of paper. You may begin thinking about your breathing now.

Re:Hack your AP (2, Informative)

repvik (96666) | more than 4 years ago | (#26495637)

Actually, you're wrong. Increasing the transmit power will decrease your S/N ratio. It's actually better to lower the transmit power a bit, since there will be more signal and less noise.

Insightful ? (0)

Anonymous Coward | more than 4 years ago | (#26496039)

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.

Solution (4, Insightful)

pondermaster (1445839) | more than 4 years ago | (#26495427)

Go back to wired, if you can. Really, you will enjoy the speed increase.

Re:Solution (1, Insightful)

Distortions (321282) | more than 4 years ago | (#26495469)

Yeah, unless its impractical to run a wire to where you need it... go for wired.

Wired gives you better speed, reliability and security.

Re:Solution (5, Interesting)

stonedcat (80201) | more than 4 years ago | (#26495481)

I just run the ethernet cables along edge of the ceiling with tacks, that way my rats don't eat them.
Using cables similar to the wall colour makes the eyesore minimal.

Re:Solution (5, Funny)

UncleWilly (1128141) | more than 4 years ago | (#26495745)

You know, some people get fish for pets.

Re:Solution (5, Funny)

Anonymous Coward | more than 4 years ago | (#26495755)

i'm pretty sure that his way prevent fish to eat them too ...

Re:Solution (0)

Anonymous Coward | more than 4 years ago | (#26495825)

Who says that his rats are pets?

Re:Solution (1)

retyurecvb (1442035) | more than 4 years ago | (#26495517)

Yeah, unless its impractical to run a wire to where you need it Isn't the practicality the whole idea behind wireless, though? I highly doubt that this would be an issue if it wasn't impractical.

Re:Solution (0)

Anonymous Coward | more than 4 years ago | (#26495525)

Whoops, sorry about the shoddy formatting, folks.

Re:Solution (1)

pondermaster (1445839) | more than 4 years ago | (#26495541)

"Isn't the practicality the whole idea behind wireless, though?"

Yes, but the dude has interference and performance problems. So a viable solution may be wiring up.

Re:Solution (5, Insightful)

icebraining (1313345) | more than 4 years ago | (#26495863)

It should be, yes, but nowadays I see wireless being installed everywhere, even when not needed. I know people who connect their desktop to the modem 10 feet away by wireless. And two months ago I went to a big store to buy a simple ethernet card and they told me "nobody produces them anymore, get wireless".

I have a Cat5 from my living room to my bedroom (65 feet) across the ceiling and it's great, I get incredible speeds in transfers from one computer to the other!

Re:Solution (4, Funny)

Anonymous Coward | more than 4 years ago | (#26495617)

He lives in a condo. Going to wired may not be practical.

So, I recommend he place his router in a Faraday cage. His interference problems will be over!

Re:Solution (1, Interesting)

Znork (31774) | more than 4 years ago | (#26495723)

And in case TP cabling is impractical, consider a network over powerline solution like HomePlug. Frankly, if you have a problem with your wireless being slow and unreliable, you shouldn't be using wireless. Wireless is great for intermittent asynchronous low bandwidth communications, like the occasional mail or web page on a laptop, but being slow and unreliable is pretty much part of its nature in many cases.

Re:Solution (1)

VON-MAN (621853) | more than 4 years ago | (#26496073)

I'm all for wired, but also really appreciate using wireless for my notebook. And I would like to use this notebook everywhere in my house and garden. So I'm interested in some answers here.

Its very simple (-1, Redundant)

Anonymous Coward | more than 4 years ago | (#26495441)

I have no idea.

Get a MIMO hub (2, Informative)

Bearhouse (1034238) | more than 4 years ago | (#26495447)

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.

Re:Get a MIMO hub (2, Informative)

Tweaker_Phreaker (310297) | more than 4 years ago | (#26495815)

There is no such thing as a hub with wifi. Hubs are devices that are "dumb" and essentially just extend a physical wire. Wifi has no wires so the wifi equivalent of hubs would be repeaters. Most consumers have wifi routers though.

Escape to A (5, Interesting)

amorsen (7485) | more than 4 years ago | (#26495449)

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.

Not just A (2, Informative)

Anonymous Coward | more than 4 years ago | (#26495613)

802.11n also supports the 5ghz band.

Re:Not just A (3, Informative)

seinman (463076) | more than 4 years ago | (#26496041)

Not always. I thought it did, but apparently that's an option. I bought an N router, expecting it to be an N router, but it only works on the 11 US-standard 2.4 ghz channels. It won't give the full N speeds either, i'm stuck right around 100 to 120 mbps most of the time.

Re:Not just A (4, Informative)

hjf (703092) | more than 4 years ago | (#26496087)

that's because N at 270Mbps only works on the 5GHz band, if you have a cheap AP it will only have 2.4 and work at 120mbps. You need a dual-radio, I have a WRT600N and I get full speed. The WRT600N is great: 3 antennas with 3 independent radios. MIMO, N, 2.4+5.8, etc. Plus you can flash it with DD-WRT and get some extra functionality (warning: only one particular old version of dd-wrt gives 270mbps, it's a known bug, I don't know if it has been fixed). I suggest that AP/router hands down. Don't get the WRT610N, while it might seem a little better (610 > 600, right?), it only has internal antennas.

5GHz (2, Interesting)

troll8901 (1397145) | more than 4 years ago | (#26495627)

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.

Re:5GHz (3, Informative)

amorsen (7485) | more than 4 years ago | (#26495683)

No reason to go with A, as long as you make sure the N-equipment you buy actually supports 5GHz.

Re:Escape to A (2, Interesting)

amias (105819) | more than 4 years ago | (#26495883)

transmitting 802.11a outside at non trivial power levels requires a special licence , in the uk.

Spread the channels (4, Interesting)

KasperMeerts (1305097) | more than 4 years ago | (#26495477)

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.

Re:Spread the channels (2, Interesting)

drspliff (652992) | more than 4 years ago | (#26496029)

Currently I can detect between 11 and 16 on a regular basis, with maybe another 7 or 8 APs that only show up now & then depending on time of day/weather/phase of moon etc.

iwlist eth1 scanning | grep Channel:
Channel:1
Channel:6
Channel:6
Channel:9
Channel:11
Channel:11
Channel:11
Channel:1
Channel:6
Channel:5
Channel:6
Channel:6
Channel:11

On bad days I often get serious interference with signal quality dropping down to 1mbit, huge amounts of packet loss, varying delay between me & the router between 60 and 900ms... the situation sucks yet I cant do anything about it (strict landlord refuses to put in new phone lines so the only inet access I have is via the shared house wifi etc.)

Other days it's great, particuarly over the christmas holidays when (I presume) lots of people in the neighbourhood were away I had a very stable connection.

To a certain extent I blame this on the high-power wifi APs which are advertised as "stronger signal wherever you are in the house", the only problem is when you have 20+ of these in a small area mostly on the default channels which overall results in connection issues for everybody. I tried explaining this to a neighbour who was having wifi problems too, but the whole concept seems lost on them.

Personally I wish small lower-powered meshing APs were used and placed liberally around peoples houses depending on *where* they needed them so I wouldn't be able to pickup signals from 3 streets away.

Re:Spread the channels (1)

Godji (957148) | more than 4 years ago | (#26496129)

In Europe we have 13 channels, but only 1, 7, and 13 are really independent. I can detect 5 other routers, all belonging to clueless neighbors. Guess what? They are all at the default channel 6 for some reason, except one which is on 7. I just switched to 13 and guess who's streaming FLACs all over the place :D

So your solution is: Convince all clueless neighbors that channel 6 gives the best reception!

Re:Spread the channels (0)

Anonymous Coward | more than 4 years ago | (#26496149)

everyone and their mother uses 1,6, and 11. So use 4 and 9 instead.

Re:Spread the channels (3, Informative)

Xabraxas (654195) | more than 4 years ago | (#26496253)

everyone and their mother uses 1,6, and 11. So use 4 and 9 instead.

4 overlaps with both 1 and 6. 9 overlaps with both 6 and 11.

Re:Spread the channels (3, Informative)

postbigbang (761081) | more than 4 years ago | (#26496223)

It might be possible that your WiFi AP has support for Channel 14-- not found usually on US gear, unless you flash the AP with the International Version (hint). The second thing you can do is to get cheapo antennas to put on the AP (~$10 at a local Frys or eBay) to boost the output in a particular direction. My suggestion is to boost it in a direction away from adjacent neighbors.

And while 802.11a sounds good as it probably has little interference, the hardware is a bit expensive compared to 802.11b/g/n.... N is nice if you can find cheaper hardware and it's the first time that I finally put away the Ethernet cables and went truly wireless around my house. YMMV.

802.11a, 5ghz (3, Informative)

Bert64 (520050) | more than 4 years ago | (#26495487)

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.

Re:802.11a, 5ghz (1)

drinkypoo (153816) | more than 4 years ago | (#26496093)

I don't know about you, but I have five machines on wifi in my house and only one of them supports 802.11a, and that doesn't include the AP. Some of the machines don't even have USB2 and adding it would be cost-prohibitive.

Get directional antennas (4, Informative)

femto (459605) | more than 4 years ago | (#26495507)

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 [wikipedia.org].

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.

Re:Get directional antennas (1, Informative)

Anonymous Coward | more than 4 years ago | (#26495679)

He can switch to 802.11a, hook up a 1 watt radio, set it on 5.8ghz, and blast out as much EIRP as he wants for point-to-point. Go for a 3 foot dish with about 30dbi. That should get it into the next room.

Don't trust the network list! (5, Informative)

Anonymous Coward | more than 4 years ago | (#26495545)

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 ... (5, Interesting)

geekymachoman (1261484) | more than 4 years ago | (#26495551)

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.

Firmware for Japs (1, Interesting)

Anonymous Coward | more than 4 years ago | (#26495553)

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!

Buy a European AP (4, Interesting)

jimallison86 (1156175) | more than 4 years ago | (#26495579)

Then you can use channels 12 and 13, which will have a touch less interference

Re:Buy a European AP (0)

Anonymous Coward | more than 4 years ago | (#26495743)

even better - get a japanese one, so you will have channel 14 as well. As an extra bonus the spacing between channel 13 and 14 is bigger than between the other channels.

Re:Buy a European AP (0)

Anonymous Coward | more than 4 years ago | (#26495993)

We actually did this at a recent tradeshow... the show floor was covered in wifi and the interference was messing with a certain product we were demoing that relies on decent wifi speeds.

We switched our AP to channel 12 for the demo and were able to get much better performance than beforehand.

Re:Buy a European AP (0)

Anonymous Coward | more than 4 years ago | (#26496187)

a certain product we were demoing that relies on decent wifi speeds

Truth in advertising, dude. If you have to use illegal channels to make your product work, isn't that something that your customers should know?

Stop interference at the source (4, Funny)

goddidit (988396) | more than 4 years ago | (#26495585)

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.

Re:Stop interference at the source (0)

Anonymous Coward | more than 4 years ago | (#26495903)

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.

They will just buy new one or get replacement from their ISP.

Switch to 802.11n at 5ghz (4, Interesting)

CapsaicinBoy (208973) | more than 4 years ago | (#26495607)

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.

Re:Switch to 802.11n at 5ghz (1)

cstromme (1401527) | more than 4 years ago | (#26495693)

I was just about to post this. 802.11n at 5GHz is definitely the best solution assuming your gear supports it.

Luckily Windows shows your neghbour's channel (1)

Joce640k (829181) | more than 4 years ago | (#26495619)

Oh, wait, no it doesn't...you have to guess.

Re:Luckily Windows shows your neghbour's channel (1)

Whizzmo2 (654390) | more than 4 years ago | (#26495721)

... which is why god created NetStumbler [stumbler.net] :)

--Whizzmo

Re:Luckily Windows shows your neghbour's channel (1)

Joce640k (829181) | more than 4 years ago | (#26496095)

Please adjust your sarcasm-ometer, I was making a wry comment about the state of Windows.

Yes, this same OS which makes you type in your password twice when logging onto a network is incapable of showing the channels used by the others so you can set up your network nicely.

Well done, Redmond.

Make a DIY Directional Antenna (5, Insightful)

wilby (141905) | more than 4 years ago | (#26495623)

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.

Re:Make a DIY Directional Antenna (0)

Anonymous Coward | more than 4 years ago | (#26495687)

Nice tips. I would like to subscribe to your newsletter.

Re:Make a DIY Directional Antenna (5, Funny)

Ash-Fox (726320) | more than 4 years ago | (#26495851)

In extreme cases I need to use the "foil sheet".

Don't listen to him! He's just trying to trick you into removing your tin foil hats!

Use only channel 1,6 and 11. (2, Informative)

Anonymous Coward | more than 4 years ago | (#26495649)

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.

Re:Use only channel 1,6 and 11. (0)

Anonymous Coward | more than 4 years ago | (#26495685)

Ok, so I get it that all the criptography stuff is useless???

Shouldn't the use of an orthogonal key reduce the noise?

Re:Use only channel 1,6 and 11. (1)

gomiam (587421) | more than 4 years ago | (#26495777)

ODFM isn't cryptography, it's Orthogonal frequency-division multiplexing [wikipedia.org], which is somewhat similar to the old method of phone call multiplexing. I think you may be thinking of code division multiplexion as used in the US cell phone system, in which every phone talks to the tower in a different "language" over the whole channel so interferences is less noticeable (I'm talking from memory here, anybody who might correct my or make things clearer would help us all). Code division seems to be more secure than frequency or time division because you have to find the signal (code division, IIRC, could work with quite bad signal-noise ratios) and _then_ ou have to find out the "language" (this may be easier than I think if there's just a preset table of codes).

Re:Use only channel 1,6 and 11. (4, Informative)

Anonymous Coward | more than 4 years ago | (#26495849)

On the lowest level you have the radio spectrum. Channel 1, 6 and 11 does not interfere with each others frequencies at all. Channel 3 interferes with both channel 1 and 6 (with the wider 802.11g channels)

On the next level you have the orthogonal keys, they make this transmission look as random noise to other transmissions on the same radio channel. On such a radio channel you have a Signal to Noise ratio that basicly limits the amount of information you can transmit. The more random noise you have, the less S/N you have and the less data you can transmit. Compare it to a room with too many talkers, the noiselevel increases and less gets communicated. It does not really help that your neighbour starts talking to his neighbour in another language. You will be able to filter that out, but you will still have problems talking english to those you wish to talk to since he sometimes is silent and suddenly burps out in Swedish and you have to repeat yourself in english once again.

By placing the communication on the same radio channel, you can make use of the simpler protocols were you raise your hand and is then allowed to talk. Never mind the language you speak. All of the speakers understands the handsignalling.

The standard practice is thus to use only 1, 6 and 11 as traffic on channel 2,3,4,7,8,9,10 hides the handsignalling that is used on 1,6 and 11 by those parties.

But yes, orthogonal keys do reduce the problems a bit, but not enough in a tight environment.

Re:Use only channel 1,6 and 11. (1)

julesh (229690) | more than 4 years ago | (#26496183)

Which is really useful when your neighbours have all got their systems set up on essentially random channels. E.g. mine are using 1 (x3), 4 (x1), 7 (x2), 9 (x1) and 11 (x1). I do get reasonable results on 13, better than I get on 11 or 1 (which seem the most likely candidates in terms of having less shit overlapping them).

Possible Alternative (2, Informative)

Anonymous Coward | more than 4 years ago | (#26495665)

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.

Re:Possible Alternative (0)

Anonymous Coward | more than 4 years ago | (#26495701)

I thought Canada was a condominium?

amazing (3, Insightful)

abonstu (682723) | more than 4 years ago | (#26495689)

it never ceases to amazes me the number of replies which just plain dont answer the question.

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)

Re:amazing (0)

Anonymous Coward | more than 4 years ago | (#26495731)

No you're just being an asshole generally, and instead of posting something that *might* be useful you post something that is certainly useless.

Just like me :-)

Re:amazing (1)

walt-sjc (145127) | more than 4 years ago | (#26495741)

Considering the cost of wireless equipment, it may be the best option though and it is obviously something he did NOT think of....

Re:amazing (1, Interesting)

Anonymous Coward | more than 4 years ago | (#26495831)

Assuming that the poster is not to only slashdot reader, the answers may still be useful for other readers. WiFi is a common problem.

Using a combination of cheap switches, and using single (8 wire) ethernet cable for two 10/100 mbit links I was able to completely eliminate the wireless network in the house, with a minimum of cable work. The only computer that ever worked well with wifi was my Linux eee pc.

Re:amazing (4, Insightful)

Anonymous Coward | more than 4 years ago | (#26495961)

If he doesn't know enough to answer his question, there's a reasonable chance he also doesn't know enough to ask the right questions. It's quite valid to give answers to questions he should have asked, but didn't.

Get a 5ghz 802.11 a/n access point (2, Insightful)

Whizzmo2 (654390) | more than 4 years ago | (#26495703)

You can't fix everyone else's access points, but you can change yours. As several people have mentioned, 5Ghz may be the way to go. 5Ghz offers considerably more [wikipedia.org] (usable!) channels than 2.4 Ghz. Combined with 802.11n channel widths, you should be able to get plenty of bandwidth anywhere in your house.

Example: Netgear WNHDE111 [netgear.com]

Bonuses:
  • "WPA2-only" mode. Combined with a good password, this should keep out nearly all undesirables.
  • Transmit power adjustment (low/med/high). No need to broadcast at high power if all you need is low or medium. Lower power = lower chance of interference to others, lower chance of discovery by sniffers.

--Whizzmo

Put EVERYTHING on 1 channel (3, Interesting)

Anonymous Coward | more than 4 years ago | (#26495705)

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.

Should be theoretically better at 10Mbps (1)

RegularFry (137639) | more than 4 years ago | (#26495733)

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.

Answers, in order... (5, Informative)

dtmos (447842) | more than 4 years ago | (#26495821)

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:

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)?

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.

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?

Yes, use patterns affect interference. In general, the former is best, since the channel has more idle time available for "your" data.

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?"

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 more thought (4, Interesting)

dtmos (447842) | more than 4 years ago | (#26495911)

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. :-/

Re:One more thought (1)

Baron_Yam (643147) | more than 4 years ago | (#26496045)

It's the old 'how many colours are needed to draw a map' issue.

In an apartment you have 3 dimensions to worry about, which means you could have 15 neighbours (two apartments deep by three high, with you on one side and in the middle level). In a house, you have perhaps 8 neighbours to worry about... and still only three good channels with which to work. Luckily, the ones behind are additionlly buffered by your backyard and theirs, and the ones in front have front yards plus road.

In a house, the best pattern (for you...) is:

01/06/01
06/11/06
01/06/01

In an apartment, I'd want to do the same thing in 3D - stagger the 1 & 6 channel for my neighbours and keep the 11 for myself.

In either case, good luck convincing everybody to cooperate!

It's also an improvement for your neighbours.

I'm in a similar position (1)

Krneki (1192201) | more than 4 years ago | (#26495823)

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?

FC who? (1, Interesting)

Anonymous Coward | more than 4 years ago | (#26495839)

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.

Share your connections? (5, Interesting)

SomethingOrOther (521702) | more than 4 years ago | (#26495875)


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 :-)

Re:Share your connections? (1)

bheading (467684) | more than 4 years ago | (#26496193)

There's a good chance that this violates your ISP's terms of service. Other than that, cool.:)

Pick the one with the interference (5, Interesting)

Tweaker_Phreaker (310297) | more than 4 years ago | (#26495947)

Use NetStumbler http://www.netstumbler.com/ [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.

fix the problem yourself (2, Informative)

characterZer0 (138196) | more than 4 years ago | (#26496051)

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!

Here's what I've done, for me and 600 of my closes (4, Informative)

jafo (11982) | more than 4 years ago | (#26496141)

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/ [tummy.com]

Sean

Sean

anonuserist (0)

Anonymous Coward | more than 4 years ago | (#26496157)

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

Tin foil to the rescue (1)

gooneybird (1184387) | more than 4 years ago | (#26496181)

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... (1)

hittman007 (206669) | more than 4 years ago | (#26496217)

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))...

use a combination of methods (1)

d_leiderman (948900) | more than 4 years ago | (#26496219)

Finding the problem will help you with some ideas:

- 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/ [design-to-last.com]

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