Self-Sustaining Ultrawideband Positioning System for Event-Driven Indoor Localization
Philipp Mayer, Michele Magno, Luca Benini
Abstract
Smart and unobtrusive mobile sensor nodes that accurately track their own position have the potential to augment data collection with location-based functions. To attain this vision of unobtrusiveness, the sensor nodes must have a compact form factor and operate over long periods without battery recharging or replacement. This article presents a self-sustaining and accurate ultrawideband (UWB)-based indoor location system with conservative infrastructure overhead. An event-driven sensing approach allows for balancing the limited energy harvested in indoor conditions with the power consumption of UWB transceivers. The presented tag-centralized concept, which combines heterogeneous system design with embedded processing, minimizes idle consumption without sacrificing functionality. Despite modest infrastructure requirements, high-localization accuracy is achieved with error-correcting double-sided two-way ranging and embedded optimal multilateration. Experimental results demonstrate the benefits of the proposed system: the node achieves a quiescent current of 47nA and operates at 1.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> while performing energy harvesting and motion detection. The energy consumption for position updates, with an accuracy of 40 cm (2-D) in realistic nonline-of-sight conditions, is 10.84mJ. In an asset tracking case study within a 200m2 multiroom office space, the achieved accuracy level allows for identifying 36 different desk and storage locations with an accuracy of over 95%. The system’s long-time self-sustainability has been analyzed over 700 days in multiple indoor lighting situations.