802.11 Channels

802.11 operates over two major spectral bands: the ISM band covering 2.4 GHz - 2.485 GHz spectrum and the 5 GHz band.

The ISM band is divided into 14 channels at different frequencies. The center frequencies are separated by 5 MHz (i.e. 2412, 2417, 2422, etc). However, the bandwidth is +/- 10 MHz. Hence, there is a significant spectral overlap on adjacent channels (i.e choosing an adjacent channel to another network is almost as bad as choosing the same channel).

802-11-channel-spacing-ism.png


Geographical location dictates which channels can be used:

  • US: Channels 1-11
  • Europe: Channels 1-13
  • Japan: Channels 1-14

Setting The Channel:

The Access Point (AP) administrator chooses a channel for a specific AP. Interference is possible. The channel selected can be the same as that chosen by a neighboring AP!

In the US, channels 1, 6, and 11 are non-overlapping (at the -3 dB points), so these are typically selected for APs.
In Europe, channels 3, 8, and 13 are typically used.

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