GPSMirror: Expanding Accurate GPS Positioning to Shadowed and Indoor Regions with Backscatter

Abstract

Despite the prevalence of GPS services, it still suffers from intermittent positioning with poor accuracy in partially shadowed regions like urban canyons, flyover shadows, and factories' indoor areas. Existing wisdom relies on hardware modifications of GPS receivers or power-hungry infrastructures requiring continuous plug-in power supply which is hard to provide in outdoor regions and some factories. This paper fills the gap with GPSMirror, the first GPS-strengthening system that works for unmodified smartphones with the assistance of newly-designed GPS backscatter. The key enabling techniques in GPSMirror include: (i) a careful hardware design with 𝜇𝑊 -level power consumption that pushes the limit of backscatter sensitivity to re-radiate extremely weak GPS signals with enough coverage approaching the regulation limit; and (ii) a novel GPS positioning algorithms achieving meter-level accuracy in shadowed regions as well as expanding locatable regions under inadequate satellites where conventional algorithms fail. We build a prototype of the GPSMirror tags and conduct comprehensive experiments to evaluate it. Our results show that a GPSMirror tag can provide coverage up to 27.7 m. GPSMirror achieves median positioning accuracy of 3.7 m and 4.6 m in indoor and urban canyon environments respectively. CCS CONCEPTS• Information systems → Global positioning systems;• Hardware → Networking hardware.