I've been working with an SDR (software-defined radio) as part of a computer security class project. We've been wondering if, let's say a mobile phone associates with the SDR (which is operating as a fake BTS), and then tries to send an SMS, then would the SDR be able to pick up the originator address (as the mobile phone number) from this number?
In the first place, does a mobile phone know its number at all? Or does it only know its TMSI number? How does it identify itself when it sends an SMS to its GSM provider's BTS then?