1.Introduction 2.The Mobile Station and the Subscriber IdentityModule 3.The Base Station Subsystem 4.The Network Switching Subsystem 5.The OSI Reference Model 6.The Abis-Interface 7.The Air-Interface of GSM 8.Signaling System Number 7 9.Signaling Connection Control Part 10.The A-Interface 11.Transaction Capabilities and Mobile Application Part 12.Scenarios 13.Quality of Service