About OpenBTS and minimal hardware requirements for a GSM network

Hi people,
I and a friend will try the OpenBTS (we aim to make a free GSM network),
and I’d like to know if I can use a DBSRX in the RX chain (just for
testing purposes), and a RFX900 in the TX chain.
I already own a DBSRX, so them I’d have to buy only a RFX900.

I’m following this page:

I’d also like to know what version of gnuradio and openbts is
for us to make our test.

We only want to make a hello world, w/ the cell phone very close to the
USRP, so we’ll try to make our first test w/ no PA nor BPF, and also
without the duplexer (using two antennas).
Can our test be successful?
How about the SIM configuration, any tip on how to make one or on how to
configure the cell phone?

Also, we’ll try to pick any free radio band to make our test - any
on how to look a “free room” in the cell phone spectrum?

rafael diniz