40MHz or 20MHz and DFS channels

[Laura]

Is it better to put both radios on 20MHz or 40MHz or both? This is for Wireless AP3605 Internal APs on the C5210 Controller. This is for elementary school with APs above the drop ceiling in each classroom. Should I use the DFS channels, in order to have more channels to use?

[Raffi]

I think best approach would be to use 20Mhz for 2.4ghz and 5ghz. Use 20mhz and all available channels for best client contention free air time and spatial reuse with so many non-overlapping channels. Keeping min basic rate low and client roaming aggressiveness to medium or medium high to keep clients close to their ap. Keep an eye out for any client devices on the network that may not like DFS channels, or for DFS events in the log indicating the aps have sensed something with radar signature in the environment.

[Doug]

Saiprasad Rapol, it would only cause issues if you have a dense deployment of access points that were on the same channels. The wider the channel, the higher the data rate and bandwidth that access point will be able support. However, this comes at a cost. The wider the channel, the fewer channels that are available for channel planning.

https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-create-a-5GHz-WiFi-Channel-Plan

[Saiprasad_Rao_R]

Hi raffi If we use 20mhz on 5ghz , does it mean degrading the 5ghz radio and making it work as similar as 2.4ghz. What if we set 20mhz for 2.4ghz and 40mhz for 5ghz, will it cause any issues?