From 27C3 public wiki
OsmocomBB
*TBD*
The OsmocomBB project was started in January 2010 by Harald Welte and Dieter Spaar, others joined the project since then. It is an implementation a GSM baseband firmware from scratch. (The sofware that controls your mobile phone during or between calls.) This includes GSM MS-side protocol stack from Layer 1 through layer 3, hardware drivers for GSM baseband chipset, simple user interface on the phone itself, and verbose user interface on the PC.
