OK let's start with WLAN basics - 802.11g is what you currently tx on your APs - has a max data rate of 54Mb.
WLAN is a half duxplex medium - so 20-22MB is the max for 802.11g - so there is no problem.
You just haven't configured the controller/AP correctly.
At this point I'd bet on it that you run in demo mode = you haven't install a license on the controller.
In the lower right corner of the controller does it show "unlicensed"
In Demo mode only radio#2 will work for 802.11bg.
So load a license + configure the controller correctly = high speed WLAN.