Tragedy of the Spectrum Commons?

by on April 25, 2008 · 14 comments

I’ve been noticing recently that wi-fi connections are flakier than they used to be. It seems to me that from about 2001 to 2005, it was almost unheard-of for my home wi-fi connection to suddenly drop out on me. In the last year or two, it has seemed like this is an increasingly common occurrence. For the last half hour or so, my Internet connection has been going out for 5 or 10 seconds at a time every few minutes. It’s not a huge problem, but it happens just often enough to be pretty annoying.

I can think of a number of possible explanations for this. One might be that my current laptop, a MacBook I bought about a year ago, might have a lower-quality wireless card. Another might be that I’m using wi-fi in more places where it might be hard to get good coverage. Or maybe I’m imagining things.

But it also seems possible that we’re starting to experience of a tragedy of the wi-fi commons. I seem to recall (and Wikipedia confirms) that wi-fi cards effectively have only 3 “channels” to choose from, and that the wi-fi protocol isn’t especially well-designed to deal with multiple networks using the same channel at close proximity. It has now become commonplace for me to whip out my laptop in an urban setting and see a dozen or more wi-fi networks. Which suggests that there’s got to be some serious contention going on for those channels.

If I’m right (and I might be wildly off base) I’m not sure where the analysis goes from there, either from a technical perspective or a policy one. One knee-jerk libertarian answer is to suggest this is an argument against allocating a lot of spectrum to be used as a commons because it tends to be over-used and there’s no one in a position to resolve this kind of contention. On the other hand, maybe people are working on better protocols for negotiating this kind of contention and achieving a fair sharing of bandwidth without these problems. Or perhaps—at least for wi-fi—it would be possible to allocate enough bandwidth that there’d be enough to go around even in dense urban areas.

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About Tim Lee

Timothy B. Lee (Contributor, 2004-2009) is an adjunct scholar at the Cato Institute. He is currently a PhD student and a member of the Center for Information Technology Policy at Princeton University. He contributes regularly to a variety of online publications, including Ars Technica, Techdirt, Cato @ Liberty, and The Angry Blog. He has been a Mac bigot since 1984, a Unix, vi, and Perl bigot since 1998, and a sworn enemy of HTML-formatted email for as long as certain companies have thought that was a good idea. You can reach him by email at leex1008@umn.edu.

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  • http://www.manifestdensity.net Tom

    Although a crowded spectrum might degrade speed, I don’t think it should cause your connection to drop.

    There are a few other possibilities, though. I agree that a flaky card might be to blame — a flaky router (or router firmware) is even more likely, given that your machine is from Apple. Is there construction near you? If someone’s spewing out EM noise by, say, arc welding in a nearby building that’s being constructed, that’ll kill your connection very quickly, too. That was a constant nuisance when we moved into our present offices.

  • http://www.manifestdensity.net Tom

    Oh, and I forgot the most obvious possibility: don’t forget that microwave ovens run at 2.4 GHz, too. If someone near you has a poorly-shielded one or is using a 3-to-2 prong power plug adapter to run it ungrounded, it’s very possible that that is to blame. Whenever Emily turns on her microwave the network immediately goes down, for instance.

  • Tim Lee

    Interesting. And good to know. I’m at Cato now, which doesn’t appear to have any nearby construction, but I’ll know to be on the lookout for that and microwaves.

  • http://www.manifestdensity.net Tom

    Although a crowded spectrum might degrade speed, I don’t think it should cause your connection to drop.

    There are a few other possibilities, though. I agree that a flaky card might be to blame — a flaky router (or router firmware) is even more likely, given that your machine is from Apple. Is there construction near you? If someone’s spewing out EM noise by, say, arc welding in a nearby building that’s being constructed, that’ll kill your connection very quickly, too. That was a constant nuisance when we moved into our present offices.

  • http://www.manifestdensity.net Tom

    Oh, and I forgot the most obvious possibility: don’t forget that microwave ovens run at 2.4 GHz, too. If someone near you has a poorly-shielded one or is using a 3-to-2 prong power plug adapter to run it ungrounded, it’s very possible that that is to blame. Whenever Emily turns on her microwave the network immediately goes down, for instance.

  • http://www.tc.umn.edu/~leex1008 Tim Lee

    Interesting. And good to know. I’m at Cato now, which doesn’t appear to have any nearby construction, but I’ll know to be on the lookout for that and microwaves.

  • Ryan Radia

    There are 11 channels in the 2.4Ghz unlicensed band and seemingly few people know to scan the airwaves using a tool like Netstumbler and then set their AP to broadcast on an unoccupied channel when possibile. Most routers default to ch 6 or 11 and few auto-assign effectively for some reason. When setting up a wifi access point I just pick a channel with minimal interference and I’ve always had a usable signal with decent range. Plus if you have the WRT54GL (which is the best consumer router ever) running good custom firmware (DD-WRT, OpenWRT, Tomato) you can even set antenna power output above factory defaults for noticeable gain in signal to noise ratio.

  • Ryan Radia

    There are 11 channels in the 2.4Ghz unlicensed band and seemingly few people know to scan the airwaves using a tool like Netstumbler and then set their AP to broadcast on an unoccupied channel when possibile. Most routers default to ch 6 or 11 and few auto-assign effectively for some reason. When setting up a wifi access point I just pick a channel with minimal interference and I’ve always had a usable signal with decent range. Plus if you have the WRT54GL (which is the best consumer router ever) running good custom firmware (DD-WRT, OpenWRT, Tomato) you can even set antenna power output above factory defaults for noticeable gain in signal to noise ratio.

  • http://linuxworld.com/community/ Don Marti

    I’m noticing the exact opposite — maybe more people near where I use wireless are switching to 5.8GHz mobile phones.

    (For security, it’s best to keep your AP’s power setting as low as you can without losing too many packets, but nobody does this.)

  • dmarti

    I’m noticing the exact opposite — maybe more people near where I use wireless are switching to 5.8GHz mobile phones.

    (For security, it’s best to keep your AP’s power setting as low as you can without losing too many packets, but nobody does this.)

  • Ryan Radia

    i’d assume you could broadcast as loud as you want if using WPA2 with 256-bit and nobody’d be able to crack it, no?

    maybe the very existence of unlicensed spectrum has crowded out the market for privately managed personal-area networks. far as i know, if you want a personal-area network that runs on licensed bands, there’s no consumer-grade router you can buy that lets you make a micropayment to a spectrum reseller which manages a segment of frequencies to prevent the sort of interference that’s plaguing wifi in densely populated areas.

  • Ryan Radia

    i’d assume you could broadcast as loud as you want if using WPA2 with 256-bit and nobody’d be able to crack it, no?

    maybe the very existence of unlicensed spectrum has crowded out the market for privately managed personal-area networks. far as i know, if you want a personal-area network that runs on licensed bands, there’s no consumer-grade router you can buy that lets you make a micropayment to a spectrum reseller which manages a segment of frequencies to prevent the sort of interference that’s plaguing wifi in densely populated areas.

  • http://bennett.com/blog Richard Bennett

    The reason 802.11b and g networks choose channels 1, 6, and 11 is that these are the only ones that don’t overlap with each other. If you choose channels 2, 3, 4, or 5, you overlap with both 1 and 6 and that’s not very smart.

    WiFi doesn’t deal well with lots of traffic from overlapping networks, so if you’re in an area with a lot of WiFi traffic, such as an office park or an apartment, you should look into getting some 802.11a gear because few people use the 5 GHz band that it uses. And 802.11n is a more robust system than b, g, or a.

  • http://bennett.com/blog Richard Bennett

    The reason 802.11b and g networks choose channels 1, 6, and 11 is that these are the only ones that don’t overlap with each other.
    If you choose channels 2, 3, 4, or 5, you overlap with both 1 and 6 and that’s not very smart.

    WiFi doesn’t deal well with lots of traffic from overlapping networks, so if you’re in an area with a lot of WiFi traffic, such as an office park or an apartment, you should look into getting some 802.11a gear because few people use the 5 GHz band that it uses. And 802.11n is a more robust system than b, g, or a.

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