Are you fucking with me, or what?
If you have ONE AP using ONE channel and you have ONE user, then the user can use (or at least approach) the full channel capacity. When you add a second node you have to add some back off time to avoid collisions. As you add nodes, there are more times when you have to back off. During back off time, no one is transmitting. Since capacity is a RATE, any TIME when no one is transmitting equals a LOSS of capacity.
So, for the third fucking time, without regard to power or interference, the aggregate capacity of a wireless network decreases as the number of nodes increase.
I'd be very happy to discuss this further. But if you just say the same thing again I will wish horrible, violent death on you.