Hello,
You have many choices.
If you are interested in the system as a whole, you can perform a system simulation for any of these standards, this can be done on MATLAB or ADS ptolemy, which is by the way much more powerful!!,
My suggestion, OFDM. It's really promising. you can find it in WiMAX 802.16 (a throgh e) and WiLAN 802.11a/g , but take care, it's really a tough standard,
As you might now, any standard has it's phy and MAC layers. I think you might be more intereseted to implement the MAC. although I injoyed building the WiMAX phy for my grad project.