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 paper presents a self-sustaining and accurate
ultra-wideband-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
ultra-wideband 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 47 nA and operates at 1.2 μA while performing
energy harvesting and motion detection. The energy consumption for position
updates, with an accuracy of 40Â cm (2D) in realistic non-line-of-sight
conditions, is 10.84Â mJ. In an asset tracking case study within a 200Â m2
multi-room office space, the achieved accuracy level allows for identifying 36
different desk and storage locations with an accuracy of over 95Â %. The
system`s long-time self-sustainability has been analyzed over 700Â days in
multiple indoor lighting situations