need solution for this scenario

Hi folks,

This is my first post to this mailing list. I have to deploy a
"authentication , authorization and accounting) solution for a Wi-Fi
network. So i need some inputs from you.

Scenario is like this:

We have a set of APs on the network. Wireless users will connect to
internet throgh these APs. Assume all the internet traffic is routed
through a linux box.  We want user to be granted access after
authentication and then also want to monitor the time for which he was
active so that we can bill him for internet usage.

I think nocat solves the authentication problem, but I want to track
session for each user for billing.....him...!!!

I heard radius server gives you a webbased interface to track
sessions... Somehow i couldn't integrate all the comonents.
So if anyone can point to some useful pointors and suggest some
solution (like opensource implementation ) would be of immense help.

thanks in advance.

-sunil