Current sensor network technologies seriously limit the use of large sensor arrays in complex natural environments. One of the most critical limitations is power. Sensors require power to sense, send and receive information, and in virtually all wireless networks currently deployed are battery-powered. Batteries account for most of the mass of the sensor and have a finite life, resulting either in periodic replacement or a limit to the useful life of the whole network. Many environmental applications require data at high frequencies, confounding problems with batteries as battery life decreases as the frequency of data acquisition and transfer increases. Battery-powered sensors are a serious impediment to the development of sensor networks that can function unattended and autonomously in complex, sensitive or hostile environments. To circumvent this problem, the PIs propose a new approach to power supplies in wireless sensor networks: battery-free, passively powered sensors. Sensors in this system will receive power in the form of spread-spectrum radio waves from a powered base station, which in turn is powered by batteries that are continuously recharged by a solar panel. Thus, a single power source will power 80-100 sensors, which could remain functional indefinitely with minimal attention following deployment. Successful development of this novel system requires a total-systems approach in which data storage, routing, transport, and calibration protocols are designed to minimize the number of bits transmitted while ensuring accurate measurement. This project will develop a prototype wireless network of sensors that will support measurements at high temporal and spatial frequency in complex, sensitive environments. Broad impacts will arise from multi-disciplinary collaboration among computer scientists, engineers, and ecologists; participation by students spanning undergraduate to post doctoral levels; integration with ongoing IGERT, SMILE, and LTER Schoolyard education programs; and communication through project website.
