Sensor node localization with uncontrolled events

Event-driven localization has been proposed as a low-cost solution for node positioning in wireless sensor networks. In order to eliminate the costly requirement for accurate event control in existing methods, we present a practical design using uncontrolled events. The main idea is to estimate both event generation parameters and the location of sensor nodes simultaneously, by processing node sequences that can be easily obtained from event detections. Besides the basic design, we proposed two enhancements to further extract information embedded in node orderings for two scenarios: (i) node density is high; and (ii) abundant events are available. To demonstrate the generality of our design, both straight-line scan and circular wave propagation events are addressed in the article, and we evaluated the design with extensive simulation as well as a testbed implementation with 41 MICAz motes. Results show that with only randomly generated events, our design can effectively localize nodes with great flexibility while adding little extra cost at the resource constrained sensor node side. In addition, localization via uncontrolled events provides a potential option of achieving node positioning through long-term ambient events.