Wireless Communications Basics --- Channel and Bandwidth

As mentioned above, the 2.4 GHz and 5 GHz bands have three frequency ranges: 2.4 GHz–2.4835 GHz, 5.725 GHz–5.850 GHz, and 5.170GHz–5.330 GHz. The following uses the 2.4 GHz band as an example to describe channel and bandwidth basics.
(1) Channel
The total width of the band is 0.0835 GHz (83.5MHz). The band is divided into 14 channels (13 of which are used in China). The width of each channel is 22 MHz of which 20 MHz is valid width and the rest 2MHz is used as buffer. In this case, adjacent channels overlap each other. As shown in the following figure, each semicircle indicates a channel. When using the 2.4 GHz band to transmit data, a terminal can choose a channel for transmission.

1) 2.4 GHz channels
In China, the numbers of the available channels range from 1 to 13. Of the channels, there are three groups of channels that do not overlap each other: channel 1/6/11, channel 2/7/12, and channel 3/8/13.

2) 5 GHz channels
•The 5.2 GHz band has eight non-overlapping channels whose numbers are 36, 40, 44,48, 52, 56, 60, and 64.

•  The 5.8 GHz band has five non-overlapping channels whose numbers are 149, 153, 157,161, and 165.
(2) Bandwidth
Bandwidth is the frequency range of a channel, namely the width. As mentioned above, the valid bandwidth of a channel is 20MHz. Therefore, you can bond two channels to achieve 40 MHz width. For example, channel 1 can only bond with channel 5 to offer 40 MHz width.