Energy efficiency is important issue in wireless sensor network application. Sensor nodes run on batteries which needs to replaced frequently. Thus, operational states of the sensor nodes should be adapted according to the surrounding to achieve best power consumption but without compromising accurate and good sensing service. Additionally, users could provide some inputs by setting policies for specific situations to increase the adaptability of the sensor nodes. Wood et al. in 2008 have implemented contex-aware power management (CAPM) in their context-aware system for home assistance application called AlarmNet . CAPM is a dynamic system which capable of controlling each sensors on a sensor node as well as its radio components, can automatically choose power management operation according to the pattern of resident behaviors. The system receives inputs of power policies defined by administrator, sensing reports from sensor nodes, resident’s behavior patterns and current system context, analyse them and sends power management commands accordingly.
 Wood, A., J.A. Stankovic, G. Virone, L. Selavo, Zhimin He, Qiuhua Cao, Thao Doan, Yafeng Wu, Lei Fang, and R. Stoleru. ‘Context-Aware Wireless Sensor Networks for Assisted Living and Residential Monitoring’. IEEE Network 22, no. 4 (July 2008): 26–33. doi:10.1109/MNET.2008.4579768.