This book cover current research area WSN. The main problem with WSN is energy of sensor node.The different technique to save the energy is available with this book. Recently many algorithms are available to track energy saving problems in wireless sensor network to increase life time of network the algorithms are top-down approach and bottom-up approach but there are problems with this techniques. The proposed technique is a delay aware technique for wireless sensor network using regular sleep and wake periods. The objective of proposed network structure is to minimize delay and to increase lifetime of wireless sensor network. The proposed network formation technique is sleep and wake period with top-down approach.