Thursday, August 21, 2014

Quick Take: Wider Channel Widths Are Flashy but Not Efficient

I've been thinking of writing a well-articulated blog post on why the preference for high-density Wi-Fi networks is smaller channel width over larger channel width. This post is NOT that.

Instead, I was on Twitter articulating some of the logical points why smaller channel widths provide better aggregate capacity than larger channel widths (assuming you deploy enough radios and take advantage of all the spectrum at your disposal). Here is a quick recap of those points.

You might want to reference my SNR to MCS Index Mapping Table, which shows why larger channels result in a reduction in modulation rate that can often offset the gain from using the wider bandwidth in the first place. And my 802.11ac Receiver Sensitivity charts show that you have to have a really great signal strength for wider channels to even be considered, but watch out in your design because overcompensating to achieve higher signal strength will increase co-channel interference (CCI) which travels a LONG ways! Finally, my post on 802.11ac Adjacent Channel Interference (ACI) shows that wider channels create more ACI than smaller channels, and ACI is even more detrimental and unfriendly than CCI. Therefore, radio receivers require greater adjacent channel rejection (up to 8dB more), and with fewer channels for frequency re-use ACI is more likely.


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