I would recommend dedicated bandwidth management tools.
I have been used MyQoS in wireless environment for more than 3 years, and it provides automatic management to throttle p2p users:
If any IP address has averaged more than 256Kb/s for the last 60 minutes, set the profile on that IP to reduce usage for 15 minutes.
It provides 2Mb/s license for free, you could get it at http://www.myqos.net