SensorBFT: Fault-Tolerant Target Localization Using Voronoi Diagrams and Approximate Agreement
The target localization primitive is used for detecting and locating an adverse event called a target in a geographic area. This versatile primitive is applicable in the physical security domain (e.g., detecting intruders in an area) or for disaster preemption, such as detecting ignition events of forest fires. Prior systems implemented this primitive over large areas by deploying a network of sensor devices, which detect changes in a specific physical parameter like pressure or temperature induced by a target. However, these systems are not designed for use in adverse environments where one or more sensors can behave in a faulty manner. While many algorithms in the distributed systems literature can be naively used to implement target localization in a fault-tolerant manner, these approaches are energy-intensive as they use computationally expensive cryptographic operations not appropriate for resource-constrained sensors. We present SENSORBFT, an energy-efficient, fault-tolerant approach for target localization. SENSORBFT uses a novel asynchronous approximate agreement protocol that enables correct sensors to achieve an approximate consensus in the presence of faulty sensors. Sensors fulfill their energy budgets by tuning the precision and accuracy of localization, where precision is the difference between honest sensors' outputs and accuracy is the difference between an honest sensor's output and the target's true location. In optimal scenarios, this protocol reduces communication from O (n3) to O (n2) messages per round, where n is the number of sensors sharing coverage over a piece of area. In a sensor testbed with n = 19 sensors, SENSORBFT consumes 2/5 th the energy consumed by existing solutions for a minor 2% loss in accuracy, significantly enhancing efficiency and coverage.
