Which Graphic Explains Co-Channel Interference Best?

I’ve been teaching WiFi for many years now. And one concept folks seem to have a hard time with is co-channel interference. Not that there *is* interference, that’s pretty obvious, but at what level does co-channel interference actually start to ‘hurt’ the Wireless LAN?

I’ve started to call these areas ‘Want’ – ‘Don’t Want’ – ‘Don’t Care’ – but the concept is still the same.

Question: At what point does another device on the same channel equate to a ‘collision domain’?

So I’m asking for the reader’s help in deciding which of the following graphics make more sense?

Which should I use in classes?

Thanks for your help!

Keith

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A – Multiple small circles

B – One large circle

C – Multiple large circles

D – Wedges