[Serusers] Open source GSM/CDMA network

Hi all serusers; I have been using SER for a couple of years now (from 2004) and I have been really impressed. It has landed me more than 2 good jobs and when combined with Asterisk, you ask yourself what Telcos without it do!!!! Given all SIP related software and ideas that are there, I have been asking myself this question: Is it possible to design a GSM/CDMA Base Transceiver Station using Software Defined Radio (for signal acquisition and processing + some SER functions,) A GSM switch (done through SER and/or Asterisk) A GSM HLR,(Home Location Register and VLR, supposing that SER with GSM auth module act as such) which is I think a set of databases and some interfaces. This may sound stupid but I thought maybe someone has thought abt sth like that? The idea was provoked by these 2 links http://www.mah.priv.at/siptrust/doit/sim-summary.html http://cvs.berlios.de/cgi-bin/viewcvs.cgi/ser/gsm_auth/ what do you think? Thanks