This book presents an in-depth study on the recent advances in Wireless Sensor Networks (WSNs). The authors describe the existing WSN applications and discuss the research efforts being undertaken in this field. Theoretical analysis and factors influencing protocol design are also highlighted. The authors explore state-of-the-art protocols for WSN protocol stack in transport, routing, data link, and physical layers. Moreover, the synchronization and localization problems in WSNs are investigated along with existing solutions. Furthermore, cross-layer solutions are described. Finally, developing areas of WSNs including sensor-actor networks, multimedia sensor networks, and WSN applications in underwater and underground environments are explored. The book is written in an accessible, textbook style, and includes problems and solutions to assist learning. This is the ultimate guide to recent advances and research into WSNs. It discusses the most important problems and issues that arise when programming and designing WSN systems. It shows why the unique features of WSNs - self-organization, cooperation, correlation - will enable new applications that will provide the end user with intelligence and a better understanding of the environment. It provides an overview of the existing evaluation approaches for WSNs including physical testbeds and software simulation environments. It includes examples and learning exercises with a solutions manual; supplemented by an accompanying website containing PPT-slides. "Wireless Sensor Networks" is an essential textbook for advanced students on courses in wireless communications, networking and computer science. It will also be of interest to researchers, system and chip designers, network planners, technical mangers and other professionals in these fields.