In a variety of scenarios, often the only way to fully observe or monitor a situation is through the use of sensors. Sensors have been used in both civil and military applications, in order to extend the field of view of the end-user. However, most current sensing systems consist of a few large macrosensors, which while being highly accurate are expensive. Macrosensor systems are highly sensitive; the entire system can break down even with one faulty sensor. Trends in sensing applications are shifting towards designing networks of wireless microsensor nodes for reasons such as lower cost, ease of deployment and. | The Application of Programmable DSPs in Mobile Communications Edited by Alan Gatherer and Edgar Ausländer Copyright 2002 John Wiley Sons Ltd ISBNs 0-471-48643-4 Hardback 0-470-84590-2 Electronic 16 Low Power Sensor Networks Alice Wang Rex Min Masayuki Miyazaki Amit Sinha and Anantha Chandrakasan Introduction In a variety of scenarios often the only way to fully observe or monitor a situation is through the use of sensors. Sensors have been used in both civil and military applications in order to extend the field of view of the end-user. However most current sensing systems consist of a few large macrosensors which while being highly accurate are expensive. Macrosensor systems are highly sensitive the entire system can break down even with one faulty sensor. Trends in sensing applications are shifting towards designing networks of wireless microsensor nodes for reasons such as lower cost ease of deployment and fault tolerance. Networked microsensors have also enabled a variety of new applications such as environment monitoring 1 security battlefield surveillance 2 and medical monitoring. Figure shows an example wireless sensor network. Figure . Microprocessor networks can be used for remote sensing 300 The Application of Programmable DSPs in Mobile Communications Another challenge in wireless microsensor systems is that all nodes are energy-constrained. As the number of sensors increases it becomes infeasible to recharge all of the batteries of the individual sensors. In order to prolong the lifetimes of the wireless sensors all aspects of the sensor system should be energy-efficient. This includes the sensor data conversion Digital Signal Processor DSP network protocols and RF communication. One important low power design consideration is leakage reduction. In sensing applications often the sensors are idle and waiting for an external event. In such low duty cycle systems more time is spent in idle mode than active mode and leakage currents can become
