Ultra wideband technology has shown great promise for providing high-quality
location estimation, even in complex indoor 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 narrowband
systems with low localization resolution. The challenge to combining these
complimentary technologies is that they share a compounding limitation,
constrained transmit power. Regulations limit ultra wideband transmissions to
just -41.3 dBm/MHz, and a backscatter device can only reflect the power it
receives. The solution is long-term integration of this limited power, lifting
the initially imperceptible signal out of the noise. This integration only
works while the target is stationary. However, stationary describes the vast
majority of objects, especially lost ones. With this insight, we design
Slocalization, a sub-microwatt, decimeter-accurate localization system that
opens a new tradeoff space in localization systems and realizes an energy,
size, and cost point that invites the localization of every thing. To evaluate
this concept, we implement an energy-harvesting Slocalization tag and find that
Slocalization can recover ultra wideband backscatter in under fifteen minutes
across thirty meters of space and localize tags with a mean 3D Euclidean error
of only 30 cm.Comment: Published at the 17th ACM/IEEE Conference on Information Processing
in Sensor Networks (IPSN'18