Dynamic Power Management in Wireless Sensor Networks Wireless Power Management

works have gained importance in a wide spectrum of civil and military applications.1 Advances in MEMS (microelectromechanical systems) technology, combined with low-power, low-cost digital signal processors (DSPs) and radio frequency (RF) circuits have resulted in the feasibility of inexpensive and wireless microsensor networks. A distributed, self-configuring network of adaptive sensors has significant benefits. They can be used to remotely monitor inhospitable and toxic environments. A large class of benign environments also requires the deployment of a large number of sensors such as for intelligent patient monitoring, object tracking, and assembly line sensing. These networks’ massively distributed nature provides increased resolution and fault tolerance compared to a single sensor node. Several projects that demonstrate the feasibility of sensor networks are underway.2 A wireless microsensor node is typically battery operated and therefore energy constrained. To maximize the sensor node’s lifetime after its deployment, other aspects—including circuits, architecture, algorithms, and protocols—have to be energy efficient. Once the system has been designed, additional energy savings can be attained by using dynamic power management (DMP) where the sensor node is shut down if no events occur.3 Such event-driven power consumption is critical to maximum battery life. In addition, the node should have a graceful energy-quality scalability so that the mission lifetime can be extended if the application demands, at the cost of sensing accuracy.4 Energy-scalable algorithms and protocols have been proposed for these energy-constrained situations. Sensing applications present a wide range of requirements in terms of data rates, computation, and average transmission distance. Protocols and algorithms have to be tuned for each application. Therefore embedded operating systems (OSs) and software will be critical for such microsensor networks because programmability will be a necessary requirement. We propose an OS-directed power management technique to improve the energy efficiency of sensor nodes. DPM is an effective tool in reducing system power consumption without significantly degrading performance. The basic idea is to shut down devices when not needed and wake them up when necessary. DPM, in general, is not a trivial problem. If the energy and performance overheads in sleepstate transition were negligible, then a simple greedy algorithm that makes the system enter the deepest sleep state when idling would be perfect. However, in reality, sleep-state transitioning has the overhead of storing processor state and turning off power. Waking up also Dynamic Power Management in Wireless Sensor Networks Wireless Power Management