On Jul 2, 2011, at 12:05 AM, aik821 aik821 wrote:

GSM can't find OpenBTS network

I'm using a USRP1 system with 2 RFX 900, no hardware alteration have been applied

So you are running with un unknown, uncorrected frequency error that might be as big as 10 kHz and your phone can't find it.  That is completely expected.  Read the wiki.