Channel usage

[Bob Edwards]

I want to put more than three access points into an area where there
will be overlap in their coverage.

At this time, I have three access points on channels 1, 6 and 11. As I
understand it, channel 1 is at 2412MHz and the separation between
channels is 5MHz. So the separation between channels 1 and 6 is 25MHz.
Each 802.11DS signal needs 22MHz of radio frequency bandwidth, so using
channels 1, 6 and 11 means that the access points don't overlap in their
use of radio bandwidth, and therefore don't interfere with each other
and so we get maximum channel utilisation.

My question is this:

If I use channels 1, 5, 9 and 13 in order to have four distinct frequencies,
I only have 20MHz of separation. As this is less than the 22MHz being
utilised for 802.11DS, what sort of performance degradation am I likely
to experience?

Anyone got a handle on this issue?

Cheers,

Bob Edwards.