OpenBTS and Asterisk as a Proxy

Hey Guys,

I am running an edicational project for my uni with the subject mobile security and I amn rebuilding an imsi-catcher, that should be able to record calls and sms.
I am using openbts, asterisk (default settings), smqueue and as a device an usrp b200.
The imsi-catcher should work as a proxy, meaning calls and sms from the subscribers are being routed through my usrp without the subscriber knowing it. In and outbound calls should be made but Im not sure if thats a matter of asterisk and if so, how to set it up.

All this is of course ran in an faraday cage where no legal issues occur!

Will be very thankful for any of your help!