  The following paper proposes a new target localization system design using an
architecture based on reconfigurable intelligent surfaces (RISs) and passive
radars (PRs) for integrated sensing and communications systems. The preamble of
the communication signal is exploited in order to perform target sensing tasks,
which involve detection and localization. The RIS in this case can aid the PR
in sensing targets that are otherwise not seen by the PR itself, due to the
many obstacles encountered within the propagation channel. Therefore, this work
proposes a localization algorithm tailored for the integrated sensing and
communications RIS-aided architecture, which is capable of uniquely positioning
targets within the scene. The algorithm is capable of detecting the number of
targets along with estimating the position of targets via angles and times of
arrival. Our simulation results demonstrate the performance of the localization
method in terms of different localization and detection metrics and for
increasing RIS sizes.
