The focus of this book is on performance optimization in Wireless Sensor Networks (WSNs), aimed at achieving, through proper design of physical and Medium Access Control (MAC) layers, energy savings and/or increased throughput. Four scenarios of interest are considered: (i) WSNs for target detection in surveillance applications; (ii) power allocation strategies for WSN lifetime maximization; (iii) throughput and lifetime maximization in clustered WSNs; and (iv) integration of radio control technology (namely, RFID) in Zigbee WSNs for high energy efficiency. In each scenario, an analytical model for performance characterization is presented, together with simulation results. The analytical and simulation-based performance optimization perspectives provide useful insights for effective WSN configuration.