we have a WLAN implementation of several AP's in a shopfloor area, and we were having some troubles. Has I red about overlapping rules, I went to the problematic areas and I could see in one location over 5 even 6 ap's. I asked the vendor that implemented and he answered:
There are only three "non overlapping" channels, that means that channel 1 (2.412gHz), channel 6 (2.437gHz) and channel 11 (2.462gHz) are separate from each other with 25mHz; so they don't begin in the bandwidth of each other.
But if you take channel 2, who is 2.417 gHz and channel 7, who is 2.442 gHz you will also have 25 mHz bandwidth!
You have to try that the neighbours have a channel difference of +5, in between the 13 channels for Europe.
It is true that it is better to have the maximum of the bandwidth, and specially if you do voice over IP, but for terminal emulation it is not problem to work with a difference of +1, because they send only small packets.
So if you see 6 access points from one point in the manufacture, it not a problem, but they have to have different channel numbers!
Is this true?