5 GHz Channel Widths

20 MHz, 40 MHz, 80 MHz, or 160 MHz channel widths?

More is not always better. 802.11n and 802.11ac can provide increased throughput by bonding channels together. However, bonding channels can come at a cost.

When you move from 20 MHz to 40 MHz you are basically halving the number of non-overlapping 5 GHz channels. A 80 MHz channel width results in quartering the number of available non-overlapping channels. Fewer non-overlapping channels result in more interference and increased channel utilization which can lead to performance issues. The figure below depicts the available non-overlapping channels per channel width.

5-GHz-channels

 

While using 80 MHz or 160 MHz channel widths seems like a good idea to increase throughput, they are not practical in high density environments. Using 40 MHz channels is recommended in most enterprise environments, and 20 MHz for high-density deployments.

In addition, high-density environments often include a mix of device types (laptops, tablets, smartphones, etc.) with varying wireless capabilities. For example, some clients may only support 20 MHz, some with support for 40 MHz, and so on. Therefore, it would be better to select a channel width that is the least , providing clients equal access to the wireless network. It’s better to have 4 clients using 20 MHz with 4 access points, instead of 4 clients with mixed capabilities communicating with 1 access point at 80 MHz. With wireless being a shared medium, the slowest clients can impede on clients with higher channel widths.

It’s important to keep this in mind when designing wireless networks. It is best practice to incorporate a  proper channel plan in your wireless surveys to provide sufficient coverage without causing too much interference or over channel utilization.

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