  In this paper, we present a new ultra-low power method of indoor localization
of smartphones (SM) based on zero-energy-devices (ZEDs) beacons instead of
active wireless beacons. Each ZED is equipped with a unique identification
number coded into a bit-sequence, and its precise position on the map is
recorded. An SM inside the building is assumed to have access to the map of
ZEDs. The ZED backscatters ambient waves from base stations (BSs) of the
cellular network. The SM detects the ZED message in the variations of the
received ambient signal from the BS. We accurately simulate the ambient waves
from a BS of Orange 4G commercial network, inside an existing large building
covered with ZED beacons, thanks to a ray-tracing-based propagation simulation
tool. Our first performance evaluation study shows that the proposed
localization system enables us to determine in which room a SM is located, in a
realistic and challenging propagation scenario.
