Opportunistic spectrum access (OSA) networks are the most important innovation that wireless communication has seen over the last decade. This book reviews recent advances in the design of OSA and related networks, discussing the latest in system level design, implementation, and prototyping. Other topics include spectrum sensing and OSA, media access control (MAC), and challenges in OSA networks deployment. The authors provide case studies for OSA in TV white spaces, OSA for local area networks, OSA for system co-existence, as well as military applications.