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Wireless Networking Hardware

How Best To Deal With WiFi Interference? 451

Posted by Soulskill
from the all-it-takes-is-one-EMP dept.
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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How Best To Deal With WiFi Interference?

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  • by Anonymous Coward on Saturday January 17, 2009 @06:16AM (#26495409)

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

    • Re: (Score:2, Informative)

      by repvik (96666)

      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.

      • How does that work?
        • by Shadow of Eternity (795165) on Saturday January 17, 2009 @08:14AM (#26495929)

          magic.

        • by ChienAndalu (1293930) on Saturday January 17, 2009 @08:26AM (#26495987)

          Homeopathy.

        • Re:Hack your AP (Score:5, Informative)

          by v1 (525388) on Saturday January 17, 2009 @11:21AM (#26496983) Homepage Journal

          Because when you increase your transmit power a bunch, all your neighbors' wifis become useless and they unplug/return them. *ding* Many of your sources of interference go away and you can turn your power back down, yielding a more favorable s/n ratio.

          But on a lighter note, from one who works in radios a lot, increasing your transmit power is only generally useful if BOTH ends of your hardware do it. It's totally useless to be able to receive the AP's signal clear as a bell if the AP can't hear you back. In many cases, the AP already has better power and a better antenna anyway, so if you could only bump one end of the conversation, you would probably get more mileage by doing it at the laptop/desktop end. I've seen people astounded that adding an amplifier on their end didn't magically improve their set's range, because while others could now hear them whereas not before, they could not hear their replies.1

          But all other factors being equal and in marginal cases where a small improvement would do, the station that is closer to the interference needs the OTHER station to transmit higher power, to make it over the nearby interference that is jamming its receive.

          Lastly, trying to move the units to different locations or reorienting their antennas can yield amazing results. Or improve your antenna(s). I was recently at a customer's house and he had a desktop upstairs on one end of the (large) house and a base downstairs in the other corner and was having problems. His card happened to have a removable duck antenna and I swapped it out for the large mag mount I carry in my bag, and he got signal fine then. Those ducks on the back of PCI cards in slots on desktops have terrible range because the metal case is so close to the antenna. (and in his situation, it was physically blocking line of sight to the base)

          And don't underestimate the loss of signal in coax at these high frequencies. Running an antenna to the roof to get a good outdoor signal will butcher the signal more than a higher antenna ever could help. If you want to get the antenna a good distance from the computer, get a USB wireless stick and move it and the antenna. Run a long USB cable to the computer, since digital signals do not degrade over distance. (tho USB itself has distance limit cutoffs) You can get a self-contained 20+dbi gain directional antenna with integrated 802.11 wireless transceiver on ebay for under $150, and I've been able to run USB for over 50ft with good cables.

        • Re:Hack your AP (Score:5, Informative)

          by csirac (574795) on Saturday January 17, 2009 @11:22AM (#26496991) Homepage
          It's not the first time I've heard this, but it comes from people who've observed degraded performance after increasing their AP's power output (usually with a 3rd-party firmware).

          What's going on here is that:
          a) Clients are still transmitting at normal power, so the AP can't hear the clients.
          b) Many APs are built with circuitry that doesn't like to be pushed very far beyond factory defaults with transmit power: the signal really does get "noisy" at high power settings.

          Too bad the default Kamikaze 7.09 OpenWRT firmwares kills any and all (six!) WRT54GL routers that I put it on (previously ran White Russian brilliantly). Apparently flashing these things with said firmware out of the box defaults the output power to 150mW (default is 28mW), and fries the transmitter circuitry. There's no option to fix this, you're supposed to install a package onto the router called "wl" and hack a call to this utility in the init script for yourself that sets the output power at bootup.
      • by Lumpy (12016) on Saturday January 17, 2009 @11:54AM (#26497233) Homepage

        Incorrect.

        I took an AP and cranked it up to max power on 802.11g channel 1. (way over limit) and left it running that way for 2 months. I had my second ap set for the other end of the band and lived with crappy signal during that time.

        when I revisited it in 2 month and I shut down my splattering and jamming AP and did a scan, EVERYONE moved away from the jamming frequency.

        So I put my real AP at the jamming frequency and now have AWESOME signal.

        you just need to presuade the neighbors to change their settings away from yours. you can ask, or you can force their hand by making them not have any Wireless connectivity until they change it.

        • Re: (Score:3, Interesting)

          by lysergic.acid (845423)

          wouldn't it be easier just to change your own wireless AP setting? making everyone else change their frequencies is just being an asshole. if everyone behaved like that, then none of you would ever get a decent signal.

          of course, the best solution is just to:
          a.) consolidate your WiFi networks so you have 1 or 2 shared WiFi networks rather than 10-12 different competing networks. that's one advantage to having municipal WiFi/WiMax--there's less crowding of the spectrum. additionally, you have greater wireless

    • by Dolphinzilla (199489) on Saturday January 17, 2009 @10:02AM (#26496503) Journal

      actually I found that since my neighbors had NO idea how to secure their AP's I went into each one with the default password (most were Linksys) I changed their frequencies all to 11 and made mine the loan AP on 1 - worked great !

      • Re: (Score:3, Interesting)

        by Anonymous Coward
        Though the parent post is funny, it's actually not a bad idea. I've gone into my neighbors router and changed the channel to help avoid overlap. I didn't change anything else while I was in there (though I could have). Basically it ended up clearing up a lot of issues for several people. He was the kind of guy who liked to think he knew what he was doing, so if I asked him if I could do this, he would've said no. But just by going in and doing it, he never knew any better, and suddenly his WiFi connection (
      • Re: (Score:3, Funny)

        by 1u3hr (530656)
        and made mine the loan AP

        Weren;t you trying not to loan your AP?

  • Solution (Score:4, Insightful)

    by pondermaster (1445839) on Saturday January 17, 2009 @06:19AM (#26495427)
    Go back to wired, if you can. Really, you will enjoy the speed increase.
  • Get a MIMO hub (Score:3, Informative)

    by Bearhouse (1034238) on Saturday January 17, 2009 @06:25AM (#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: (Score:3, Informative)

      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 (Score:5, Interesting)

    by amorsen (7485) <benny+slashdot@amorsen.dk> on Saturday January 17, 2009 @06:25AM (#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 (Score:2, Informative)

      by Anonymous Coward

      802.11n also supports the 5ghz band.

    • 5GHz (Score:2, Interesting)

      by troll8901 (1397145)

      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 (Score:4, Informative)

        by amorsen (7485) <benny+slashdot@amorsen.dk> on Saturday January 17, 2009 @07:20AM (#26495683)

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

    • Re: (Score:2, Interesting)

      by amias (105819)

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

    • Or channel 14 (Score:5, Interesting)

      by multipartmixed (163409) on Saturday January 17, 2009 @12:17PM (#26497411) Homepage

      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.

      • by this great guy (922511) on Saturday January 17, 2009 @06:30PM (#26500723)
        "My wifi card goes to 14."
  • Spread the channels (Score:5, Interesting)

    by KasperMeerts (1305097) on Saturday January 17, 2009 @06:31AM (#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.

    • by postbigbang (761081) on Saturday January 17, 2009 @09:14AM (#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.

      • Re: (Score:3, Interesting)

        by capsteve (4595) *
        actually i'm glad that someone is thinking about using non-US channels. you can actually unlock the ability to broadcast on (non-domestic, depending on where your domestic location IS) different channels by using ddwrt using domestically available AP.
        IMHO, i would use ddwrt and pick an unused channel, get an external antenna and boost your signal, use mac-based filtering, and disable SSID broadcast.
  • 802.11a, 5ghz (Score:4, Informative)

    by Bert64 (520050) <bert AT slashdot DOT firenzee DOT com> on Saturday January 17, 2009 @06:33AM (#26495487) Homepage

    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.

  • by femto (459605) on Saturday January 17, 2009 @06:39AM (#26495507) Homepage

    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.

  • by Anonymous Coward on Saturday January 17, 2009 @06:48AM (#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 ... (Score:5, Interesting)

    by geekymachoman (1261484) on Saturday January 17, 2009 @06:50AM (#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.

    • Re: (Score:3, Interesting)

      by Hatta (162192)

      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.

      How do you check that?

  • Buy a European AP (Score:4, Interesting)

    by jimallison86 (1156175) on Saturday January 17, 2009 @06:57AM (#26495579)

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

  • by goddidit (988396) on Saturday January 17, 2009 @06:58AM (#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.
    • by Brian Stretch (5304) * on Saturday January 17, 2009 @09:48AM (#26496409)

      Better yet, hack their APs and reduce their signal strength to something more agreeable. Change their channel too if necessary. If you're going to be evil, be evil constructively. (Hey, is that Google's new motto? j/k)

      Reduce your own AP's radio output too while you're at it, if you can. You're in a frickin' condo, there's no need for every AP to shout.

      Or just use Ethernet. Cables are your friend.

  • by CapsaicinBoy (208973) on Saturday January 17, 2009 @07:04AM (#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.

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

  • by wilby (141905) on Saturday January 17, 2009 @07:06AM (#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.

  • by Anonymous Coward

    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 no

  • Possible Alternative (Score:2, Informative)

    by Anonymous Coward

    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.

  • amazing (Score:3, Insightful)

    by abonstu (682723) on Saturday January 17, 2009 @07:21AM (#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)

    • by walt-sjc (145127)

      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 (Score:4, Insightful)

      by Anonymous Coward on Saturday January 17, 2009 @08:22AM (#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.
  • 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 hi
  • by Anonymous Coward on Saturday January 17, 2009 @07:26AM (#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.
  • 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.

  • I thought that IEEE 802.11n used OFDM to help prevent this sort of thing from being a problem?

  • Answers, in order... (Score:5, Informative)

    by dtmos (447842) on Saturday January 17, 2009 @07:54AM (#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 (Score:5, Interesting)

      by dtmos (447842) on Saturday January 17, 2009 @08:12AM (#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. :-/

  • by SomethingOrOther (521702) on Saturday January 17, 2009 @08:03AM (#26495875) Homepage

    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 :-)
  • by Tweaker_Phreaker (310297) on Saturday January 17, 2009 @08:18AM (#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.

  • by characterZer0 (138196) on Saturday January 17, 2009 @08:40AM (#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!

  • by jafo (11982) on Saturday January 17, 2009 @09:01AM (#26496141) Homepage

    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

  • by Gordonjcp (186804) on Saturday January 17, 2009 @10:42AM (#26496767) Homepage

    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.

  • Or does transmitting at 10 Mbps when everyone else is using 54 Mbps (for their 3 Mbps DSL pipes!) give you a true advantage?"

    ...Yes, because all people ever do is transfer data to their '3Mbps DSL pipes!'... never between two computers on the same network. I mean, that's just ludicrous. /sarcasm

  • by Danyel (107479) <danyellawson@gmail.com> on Saturday January 17, 2009 @11:20AM (#26496973) Homepage Journal

    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

  • In real life? (Score:3, Informative)

    by russotto (537200) on Saturday January 17, 2009 @03:19PM (#26499103) Journal

    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.

Our business in life is not to succeed but to continue to fail in high spirits. -- Robert Louis Stevenson

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