A proper design and deployment of a wireless network must include a channel plan, pivotal for high-performance WLANs.
Whether you are using a static channel plan or a dynamic channel assignment, there are a few things to consider beyond choosing the best channel for that network. One of the most important is deciding the correct channel width to use.
The IEEE 802.11 standard defines wireless networks’ operation in the frequency ranges of 2.4 GHz and 5 GHz. (Learn more here https://www.tanaza.com/blog/5ghz-vs-2-4ghz/).
WiFi channels are the smaller bands within each WiFi frequency band. The 2.4 GHz band is divided into 14 channels (1-14), according to the standard and depending on the availability of each country’s regulations. Each channel could be up to 40 MHz wide. The two frequencies combined allow for channel width from 20MHz to 160MHz. Although, there are 14 channels available in 2.4GHz, and only 3 of them don’t “overlap” or interfere with each other: 1, 6, and 11.
However, channels 2-5 interfere with 1 and 6, while 7-10 interfere with 6 and 11.
For instance, when a station (access point, or client device) needs to transmit something, it must wait for the channel to be free. Therefore, only one device can send data at a time. When overlapping channels (2-5, 7-10 at 2.4 GHz) are in use, any station on those channels will transmit regardless of what is happening on the other channels, causing performance downgrade. This type of interference is described as Adjacent Channel Interference (ACI).
A Co-Channel Interference (CCI), on the contrary, occurs when two or more APs in the same area operate on the same channel. This essentially turns both cells (the coverage areas for an AP) into one large cell. Any device that has something to transmit must wait for the other devices associated with the same AP. But also wait for all the devices related to the other APs on the same channel.
Indeed, CCI will also reduce performance even if not as severe as ACI. The reason behind this behavior is that multiple devices are attempting to access wireless media on the same channel, forcing stations to wait longer before they can transmit.
Due to the limited amount of available spectrum, it’s safer to use only non-overlapping 20 MHz channels, although the possibility to use 40 MHz was added in 802.11n.
In the 5GHz band, there is much more spectrum available. Each channel occupies its non-overlapping slice at 20MHz. As with the 2.4, 802.11n gave us the ability to use 40 MHz channels. From there, 802.11ac now allows 80 MHz and even 160 MHz wide channels. These wide channels are created by joining 20 MHz channels together, using the center frequency to indicate the channel.