Introduction to Wireless Sensor Networks

Wireless Sensor Networks (WSNs) have been widely considered as one of the most important technologies for the twenty fi rst century [1] . Enabled by recent advances in microelectronicmechanical systems (MEMS) and wireless communication technologies, tiny, cheap, and smart sensors deployed in a physical area and networked through wireless links and the Internet provide unprecedented opportunities for a variety of civilian and military applications, for example, environmental monitoring, battle fi eld surveillance, and industry process control [2] . Distinguished from traditional wireless communication networks, for example, cellular systems and mobile ad hoc networks (MANET), WSNs have unique characteristics, for example, denser level of node deployment, higher unreliability of sensor nodes, and severe energy, computation, and storage constraints [3] , which present many new challenges in the development and application of WSNs. In the past decade, WSNs have received tremendous attention from both