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In the United States and Canada there are 11 channels available for use in the 802.11b 2.4GHz WiFi Frequency range defined by the IEEE.

But there are only 3 non-overlapping channels available in the 802.11b standard.These are Channels 1,6, and 11. Why is it that we couldn't define a large band width so that all channels will have no overlapping?

If it were done, would we have better performance when using Wifi today?

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If there's space for only three non-overlapping bands, there will only be space for only three non-overlapping bands, regardless of how the channels are numbered. A more interesting question is why there are more than three channel numbers; the answer to that comes from the fact that WiFi is the 2.4GHz band is used for many kinds of devices besides WiFi; some of those devices, such as analog audio/video transmitters, may require a "full-time" channel allocation. Such devices are no longer terribly common, but their existence would have influenced the creation of WiFi standards. If a few such devices which each uses 5% of the available bandwidth have four-way channel selector switches, with different devices offering different but overlapping sets of frequencies, it may be that the only combination of available frequencies which would allow everything to work without interference would have something in each of the three "main" WiFi bands, but that a shifted range of frequencies would be available for the WiFi.

That having been said, I think things would have been far less confusing if the channels had been labeled "1-5", "6-10", and "11-15", (along with "2-6", "3-7", etc.)

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  • \$\begingroup\$ since WiFi is used in the whole world, why cant we extend the band width of WiFi a little bit to allocate more rooms for non overlapping channels? \$\endgroup\$ – Denis Feb 26 '15 at 4:13
  • \$\begingroup\$ It got extended. Channel 1 is actually (-1..3), channel 6 is (4..8), and channel 11 is (9..13). Without the extension, only channels 3 and 9 would be overlap free. \$\endgroup\$ – Simon Richter Jul 24 '15 at 10:39
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Bandwidth is money. The more they can fit into a frequency space, the less it's going to cost.

If it were done non-overlapping you might get marginal gains, but it was likely an engineering/cost tradeoff. At the fringes of the channel the amplitude of the signal will be lower due to imperfect filtering resulting in less noise travelling into the next channel anyways. Another reason this is done is because it's not likely to have more than 2-3 802.11b signals in any given locations so the other channels would just be there to try and avoid the other 1 or 2 in a given location. If you find a location with 4+ wifi signals, you'd likely make some gains by giving the channels more bandwidth, otherwise, you're just burning money by requiring more bandwidth.

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    \$\begingroup\$ "not likely to have more than 2-3 802.11b signals in any given locations" thats what they thought in those days... today I must search hard for a place where I find less than ten... \$\endgroup\$ – PlasmaHH Feb 17 '15 at 15:27
  • \$\begingroup\$ @PlasmaHH Lol, yeah that's how most engineering goes as progress marches on. \$\endgroup\$ – horta Feb 17 '15 at 15:36
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The channel assignment was done for 802.11 and 802.11b, where we get 11 non-overlapping channels.

802.11g with its increased bandwidth demand came later, but the channel numbering was kept to avoid confusing the users, as most "g" devices also support a silent fallback to "b".

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