Loss of wlan connection

[tomtom31]

Hello

In my network I use iAPs 103 and 205 access points with windows pc, mac and smartphones. With the mac I have a big problem. I can connect any apple device to the network, they receive an IP address and can transfer data over the wlan. After an amount of time between 5 minutes and 24 hours (or more) the wlan does not transfer any data. The mac has still the ip address and shows that it is connected. But when I try to ping my gateway there is no response. My gateway can't ping the mac too. To solve the problem I have to switch of the wlan on the mac and switch it back on.
The problem I have only with apple devices over wlan, over a wired LAN connection everything works fine. Even windows or android devices are working fine.

May someone has a hint how I can fix the problem?

Cheers Tomtom31