Is there any reason to utilize 40MHz-wide channels on the 5GHz radio versus 20MHz-wide channels?

Background:
I admin an enterprise Wi-Fi network with 11,000+ APs. The 5GHz radio is currently using 40MHz channel width. What is the benefit of this vs. using 20MHz channel width?

1 Answer

Doubling the channel width slightly more than doubles the speeds of the PHY rates you can get.

With 20MHz-wide channels on 802.11n, you can only get the 72.2, 144.4, or 216.6Mbps top PHY rates (for 1-, 2-, and 3 spatial streams, respectively). Going to 40MHz-wide channels makes it 150, 300, and 450 Mbps, respectively.

Of course this also cuts your available channels in half, so some enterprise Wi-Fi deployments choose to keep the narrow channels in order to crowd in more APs.

40- (and 80-) MHz-wide channels are fine in the spacious 5GHz band. But 40MHz-wide channels can cause problems in the relatively narrow 2.4GHz band, where 40MHz wide channels take up half the band and don't leave enough room for Bluetooth and other 2.4GHz technologies to work well.

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