WiFi Channel Selection & Performance Impact



The takeaway Summary:
Set Minimum Channel Width
Avoid Sharing Channels if possible
Last Resort, Sit Between Shared Channels
and split the difference between your adjacent channel users

The Tool for Monitoring
Originally, I used a free version of inSSIDer,
but more recently
WifiInfoView v2.60
Copyright (c) 2012 - 2019 Nir Sofer
Web site: http://www.nirsoft.net

Channel Width
By default, the 2.4 GHz frequency uses a 20 MHz channel width. A 20MHz channel width is wide enough to span one channel. A 40 MHz channel width bonds two 20 MHz channels together, forming a 40 MHz channel width; therefore, it allows for greater speed and faster transfer rates. However, the wider the channel, the more overlap and interference is created. In a crowed area, you will need the SMALLEST width possible to reduce interference, so unless you're the sole user of the channel, just go for the default.

Channel Choice
The Object is to select a channel where you are the sole user (haha -- yeah sure).
If you can, then smile, say thank you and monitor this monthly as it's likely to change out from under you.

If your Internet neighborhood is crammed with users, then your channels usage is likely crammed too. If your system/device has an 802.11ac adaptor, then it will have both 2.4GHZ and 5GHZ band support (so will 802.11n). Your best results will be with the 5G, but many find that the walls, floor or ceiling will impede your access so that the 5G is no better (or even worse) than the 2.4G. If so, opt for the 2.4G and live with it.

Download WifiInfoView, enable your WiFi device and take a look. First click on the column heading RSSI and sort ascending to get the strongest at the top of the view.
Table 1.0
Table 1.0 is a display by-RFstrength.
Whereas my SSID is closer to my device than anything else, it SHOULD BE AT THE TOP.
But there are TWO ssids stronger than my Office44 at -47db (stronger is a number closest to ZERO). That's because there are two routers at different ends of the house. Notice that the OFFICE* ssids are on different channels (6,11). The question is Which channel is better?

Table 2.0
Table 2.0 is a display by-channel
My channel 6 is between 1-6-8. Channel 1 is (-93 less -66) -27db weaker!! I'm drowning it out. The channel 11 is (-84 less -66) -18db down -- drowning it too. What about the other channel 6 users? They are -92 or -87 lower, which is at lease -86 less -66 or at lease -21db weaker -- I win again.

So while NOT the sole user of channel 6, I am -21db stronger than my competitors.

One last thought -- there's nothing sacred with the 1,6,11 channel choices and my channel 6(2.437Ghz) is much closer to channel eight(2.447Ghz) than channel one(2.412Ghz). Splitting the difference (8-1)/2 would be ~ a three channel separation from either, so the BEST choice I can make is CHANNEL 4.
This will put my RF signal equally between one and eight so as to reduce interference as much as possible.