Due to the rapid advancements in communication technology, radio-controlled communication has gained increasing importance in recent years. This book introduces the reader to the essential technical principles of mobile radio networks. The author provides an overview of the digital communication networks that have been introduced in recent years, along with their services and the protocols used. Particular attention is given to the GSM network (D-network) currently implemented in Europe, which extends the telephone service of traditional telephone networks to mobile users. Additionally, current topics from the international standardization process concerning future mobile communication systems are addressed, with a significant focus on internet connectivity.