I would just like my suspicions confirmed. We are using 1131 LWAPP APs, with a 4402 controller. In this particular install, there are around 20-30 laptops within very close proximity to each other, this will obviously create cross-channel interference from the laptops themselves. The customer has reported very slow network speeds and drop-outs when more than 10 laptops are running, but less than 5 seems to be okay.
It seems that the laptops are also associating with the same AP although there are 3 within the area. The only way to control the association that I can see is MAC filtering, in which case they might as well have wired machines.
Is this correct?
You are correct, clients provide just as much interference as APs, and sometimes even more. But even then, a single Cisco AP can handle up to 20-25 APs without problems normally.
Try enabling Aggressive Load Balancing on your Controller tab in the controller GUI. This option will actively disconnect clients if too many associate to a single AP. A controller will always do its best to load-balance, but allowing it to disconnect clients will give it more options in doing so.