Wireless communications is a broad and dynamic field that has spurred tremendous excitement and technological advances over the last few decades. The goal of this book is to provide readers with a comprehensive understanding of the fundamental principles underlying wireless communications. These principles include the characteristics and performance limits of wireless systems, the techniques and mathematical tools needed to analyze them, and the insights and tradeoffs associated with their design. Current and envisioned wireless systemsare used to motivate and exemplify these fundamental principles. The book can be used as asenior- or graduate-level textbook and as a reference for engineers, academic and industrial researchers, and students working in the wireless field.