Slocalization: Accurate Asset Tracking with Ultra Wideband Backscatter
Ultra wideband technology has shown incredible promise for providing high-quality location estimation, even in indoor complex multipath environments, but existing ultra wideband systems require tens to hundreds of milliwatts during operation. Backscatter communication has demonstrated the viability of astonishingly low power tags, but has thus far been restricted to low (localization) resolution narrow band systems. We combine these technologies to capture the best of both worlds and create Slocalization, an ultra wideband backscatter localization system that realizes decimeter-accurate localization of a static tag in complex indoor environments for less than one microwatt. This ultra-low energy budget could allow the tag to operate for over 50 years on single coin cell battery or completely battery-free with less than 5 cm2 of photovoltaic cells indoors. The key insight underlying Slocalization is that the vast majority of things in the world do not move. Thus instead of localizing on the order of milliseconds, Slocalization estimates locations on the order of millihertz. To prove the viability of this concept, we implement an energy-harvesting Slocalization tag and find that Slocalization can locate this tag with a mean 3D Euclidean error of only 30 cm.