A Robust Indoor Positioning and Auto-Localisation Algorithm

Sensor networks that use wireless technology (IEEE standards) to measure distances between network nodes allow 3D positioning and real-time tracking of devices in environments where Global Navigation Satellite Systems (GNSS) have no coverage. Such a system requires three key capabilities: extraction of ranges between sensor nodes, appropriate supporting network communications and positioning. Recent research has shown that the first two of these capabilities are feasible. This paper builds on this and develops an automatic and robust 3D positioning capability. A strategy is presented that enables high integrity positioning even in the presence of large mean errors in the range measurements. This is achieved by an algorithm that generates a tight, high-confidence upper bound on the error in a position estimate, given the noisy range measurements from the radio devices in view. As a core feature, we present a novel network auto-localisation algorithm that fully automatically determines the positions of all nearby fixed nodes. Results from a real network using the Cricket Indoor Location System show how all sensor nodes can be determined based on only one dynamic node. Simulations of static networks with 100 nodes demonstrate the importance of solving folding ambiguities. Studies from networks with imprecise range measurements have shown that it is possible to theoretically achieve a position deviation that is of the size of the ranging error.