Free Software for GSM networks During its 25 year history, Free Software has ventured in many areas of computing, such as TCP/IP networks, Internet servers, personal computers, laptops, desktop computers, embedded devices, and so on. However, there are other areas of computing that - until very recently - have not yet seen any Free Software. One prime example is cellular telephony networks. More than 3 billion subscribers use GSM cellular phones around the world. All components in the public GSM networks are proprietary both on the network side and on the telephon side. The cellular networks consist of components like base stations, telephone switches, all running proprietary software. The cellular phones - even those running Free Software based operating systems liek Android - have a separate computer called "baseband processor" that interacts with the GSM network and runs proprietary software. Since 2009, projects like OpenBTS, OpenBSC and OsmocomBB have been created to change this. They all implement components of a GSM network as Free Software. Harald Welte is the founder of OpenBSC and OsmocomBB. He will discuss the proprietary nature of the GSM world, the progress of Free Software in GSM and how the GSM related Free Software projects can be used in research and production.