USRP and GSM

Reference : http://gnuradio.4.n7.nabble.com/Is-it-possible-to-make-a-USRP-Tx-and-Rx-at-the-same-time-tt20901.html


GSM is a half-duplex TDMA protocol.  That is, a station is only ever
transmitting or receiving, but not both at the same time. 

The channel is divided into timed frames and slots, and the base
station and mobile units are allocated specific times to transmit.  

The USRP is capable of supporting this. 


There are at least two existing open-source GSM BTS implementations;
OpenBTS is one of them:

http://gnuradio.org/trac/wiki/OpenBTS

This project uses the low-level C++ interface to the USRP1, but not
the GNU Radio framework itself.