This is the first Wireless and Mobile Systems text written for Computer Science and Engineering students (as opposed to Electrical Engineering graduate students). The authors explain the general principles of how wireless systems work, how mobility is supported, what is the underlying infrastructure and what interactions are needed among different functional components. Appropriate for undergraduate or graduate courses, the chapter topics focus on qualitative descriptions and the realistic explanations of relationships between wireless systems and performance parameters. Rather than offering a thorough history behind the development of wireless technologies or an exhaustive list of work being carried out, the authors help EE and CSE students learn about this exciting technology and understand how a cell phone starts working as soon as they get out of an airplane.