802.11b, 802.11g, and 802.11n WLAN technologies are implemented in the 2.4 GHz band with a channel bandwidth of 22 MHz for legacy 802.11b and 20 MHz for 802.11g & 802.11n. Generally, these channels are called as 20 MHz channels. Considering the United States, the channels allocated for the transmission are from 1 to 11 by the FCC. Whereas most countries use channels 1 to 14.
Representation of 2.4 GHz band Channels [1]
While the US uses channels 1,6, and 11 to minimize Co-Channel Interference especially in Wireless Enterprise networks, other countries generally implement channels 1, 5, 9, and 13.
Channel Design in Wireless Enterprise network [2]
The advent of 802.11n technology made the situation worse for the 2.4 GHz Wi-Fi services. Still the large of Wi-Fi devices operate in the 2.4 GHz band and this resulted in a serious interference. The introduction of 802.11n included 40 MHz channels and are generally seen as an improvement due to higher data rates.
The implementation of 40 MHz channels in 2.4 GHz is a very bad idea (especially in enterprise networks) as this result in interference to adjacent channels. Implementation of the 40 MHz channels in enterprise scenario is also not suggested. Due to the large bandwidth of the channel, all the access points should be configured in only one channel (in the US).In other countries, it is possible to configure the APs in two non-overlapping 40 MHz channels in 2.4 GHz bands.
40 MHz channels in 2.4 GHz frequency band
Causing interference to existing 20 MHz channels and inefficient enterprise design are the drawbacks of implementation of 40 MHz channels in 2.4 GHz. This is the reason for the commercial deployment of 802.11n 40 MHz channels in 5 GHz — UNII bands.
But the 40 MHz channels are generally implemented in private networks in homes, coffee shops, and printers.
In this case, the channel bandwidth is detected with the help of smartphone application ‘Wifi Analyzer’.
One possible solution is that the Access Point & Wireless Routers manufacturers provide an option to disable 40 MHz channels in 2.4 GHz band. This can lead to practical existence of non-overlapping channels in 2.4 GHz band.
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