Today, wireless is a technology with wide-spread use – ranging from mobile telephony through wireless Internet access to the car keyless access. With the success of many small wireless devices in the consumer market and in telecommunications, it is easy to understand that ever new application areas have been developed in industrial communication in the last ten years. The past decade has seen many advances in physical-layer wireless communication theory and their implementation in wireless systems. This textbook takes a unified view of the fundamentals of wireless communication and explains the web of concepts underpinning these advances at a level accessible to an audience with a basic background in probability and digital communication. Despite the physical-layer focus of this book, it will be clear that fading and interference control has far-reaching effects. We will focus on cellular networks because they are of tremendous practical relevance right now and because the characteristics of many other wireless systems may be readily understood as special instances of or as simple extensions of the characteristics of cellular networks.