  The past years have witnessed increasing research interest in achieving
passive human localization with commodity WiFi devices. However, due to the
fundamental limited spatial resolution of WiFi signals, it is still very
difficult to achieve accurate localization with existing commodity WiFi
devices. To tackle this problem, in this paper, we propose to exploit the
degree of freedom provided by the Intelligent Reflecting Surface (IRS), which
is composed of a large number of controllable reflective elements, to modulate
the spatial distribution of WiFi signals and thus break down the spatial
resolution limitation of WiFi signals to achieve accurate localization.
Specifically, in the single-person scenario, we derive the closed-form solution
to optimally control the phase shift of the IRS elements. In the multi-person
scenario, we propose a Side-lobe Cancellation Algorithm to eliminate the
near-far effect to achieve accurate localization of multiple persons in an
iterative manner. Extensive simulation results demonstrate that without any
change to the existing WiFi infrastructure, the proposed framework can locate
multiple moving persons passively with sub-centimeter accuracy under multipath
interference and random noise.
