Hello Usman,
going from deploying an already existing GSM basestation software to implementing a complete standard is a huge step.
Also, USRP1 is almost certainly not the device I'd chose for that task -- in can shuffle a maximum of 8MS/s over USB, and you need 5MS/s for up- and downlink each for UMTS-CDMA.
From your choice of mailing list, I'd presume you want to use GNU Radio. So get your communication engineering textbooks ready, refresh what you know about digital baseband signal processing, and learn how to use and extend GNU Radio software on the
gnuradio.org website, especially on the tutorials.
Greetings,
Marcus