A wireless sensor network is comprised of a large number of inexpensive battery-powered, self-organising sensor nodes. The sensor nodes can communicate among themselves and send their data through the network to a main location or sink where the data can be observed and analysed. Wireless sensor networks enable new applications and have gained a lot of attention in the last decade, as they have a great impact on real-life activities and hold true to the promise of delivering a smart communication paradigm. These networks are often deployed in hostile or inaccessible areas to collect environmental data for analysis and decision making. Due to the deployment cost, wireless sensor networks are usually planned to run for a long time once they are deployed. The book highlights power efficient design issues related to wireless sensor networks as well as the existing WSN applications. The research efforts being undertaken in this field which help the students and researchers to grasp the materials, enabling them to understand more advanced research and make a contribution in this field for themselves is also discussed. All the chapters of this book are written by several of the leading researchers. It is believed that this book will serve as a comprehensive reference for graduate and undergraduate students who seek to learn the latest advancements in wireless sensor networks.