The following technical article from May 2008,describes some of the complexity of WiMax.

http://www.wirelessdesignasia.com/articl... and makes reference to "Wi-LAN, 7,197,022, 7,177,598, 7,023,798, 7,006,530, 6,956,834, 6,944,188, 6,925,068, 6,804,211, and 6,728,514." patents related to OFDM.

WiLan holds other patents that are more fundamental to Wireless communication and are not discussed here.
For a synopsis of these patents go to the WiLan site and look under "patents".

As I do more research into these patents it is easier to understand why license agreements are taking so long to negotiate and also why litigants are nervous. Time is on our side.