This book explains Wireless Sensor Networks energy constraints of battery-powered sensor nodes necessitate energy-efficient communication. The major existing solutions are based on classical layered protocols approach, which leads to significant overhead. It is much more efficient to have a unified scheme which blends common protocol layer functionalities into a cross-layer module. In this paper, a efficient crosslayer protocol (XLP) is introduced, which achieves congestion control, data fragmentation, routing, and medium access control in a cross-layer fashion. Our approach combines...