Position-adaptive direction finding of electromagnetic sources using wireless sensor networks

Wireless sensor networks are being used in a variety of ways - from reconnaissance and detection in military to biomedical applications and a wide variety of commercial endeavors. We introduce a position-adaptive direction finding method using mobile sensor networks and present recent experimental results in localization of a non-cooperative sensor node using static and mobile sensor networks. Electromagnetic (EM) direction finding is a technique in which a group or a swarm of Micro-Aerial Vehicles (MAVs) cooperate their sensing missions, adapt their position in real-time autonomously, and localize an unknown, hidden EM source based on optimal detection algorithms. The MAVs are equipped with IRIS wireless sensor nodes that serve as the sensing agents by providing mobility to the otherwise stationary nodes. In order to localize the transmitter, we use the Received Signal Strength Indicator (RSSI) data to approximate distance from the transmitter to the revolving receivers. We provide an algorithm for on-line estimation of the Path Loss Exponent (PLE) estimation that is used in modeling the distance based on received signal strength (RSS) measurements. The emitter position estimation is calculated based on surrounding sensors RSS values using Least-Square Estimation (LSE).