802.11 Channels

Last modified by Microchip on 2023/11/09 08:55

802.11 operates over two major spectral bands: the ISM band covering the 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).

ISM band divided into 14 channels at different frequencies

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.