Book excerpt: This book presents the technology and underlying principles of wireless communications systems. Written by a leading authority, it provides the perfect introduction for the professional or the student who has a basic understanding of telecommunications. Each system is described using a unified framework so the reader can easily compare and contrast the systems. More specifically, key features such as architecture, radio transmission, logical channels, messages, mobility management, security, power control, and handoff are addressed for each system. In addition, an analysis of such design goals as low price, wide geographical coverage, transmission quality, privacy, and spectrum efficiency helps the reader understand why the various systems have such divergent designs. Each chapter concludes with a set of exercises, and the last chapter is dedicated to twelve tutorials that provide concise explanations of technical subjects essential to wireless communications.