Andre
How do you know the numbers of associated clients is the cause of the poor performance?
A number of attached clients should not degrade performance too much. Its the bandwidth and airtime they take up when they are sending or receiving data that would cause a problem.
In certain conditions it would not be unreasonable for an AP to support 100 clients that are concurrently transmitting data and still provide the client/application with the throughput it needs to function, especially if that's just web traffic.