The Global System for Mobile communications (GSM) is a huge, rapidly expanding and successful technology.  Less than five years ago, there were a few 10's of companies working on GSM.  Each of these companies had a few GSM experts who brought knowledge back from the European Telecommunications Standards Institute (ETSI) committees designing the GSM specification.  Now there are 100's of companies working on GSM and 1000's of GSM experts.  GSM is no longer state-of-the-art.  It is everyday-technology, as likely to be understood by the service technician as the ETSI committee member.  GSM evolved as a  mobile communications standard when there were too many standards floating around in Europe. Analog cellular was in use for several years in different parts of world. Even today there are few networks of Analog cellular. The experience of analog cellular helped in developing specifications for a Digital Cellular standard. The work on GSM specs took a complete decade before practical systems were implemented using these specs.  GSM is quickly moving out of Europe and is becoming a world standard. In this presentation we will understand the basic GSM network elements and some of the important features. Since this is a very complex system,  we have to develop the  knowledge in a  step by step approach.