  Software-Defined Metamaterials (SDMs) show a strong potential for advancing
the engineered control of electromagnetic waves. As such, they are envisioned
to enable a variety of exciting applications, among others in the domains of
smart textiles, high-resolution structural monitoring, and sensing in
challenging environments. Many of the applications envisage deformations of the
SDM structures, such as their bending, stretching or rolling, which implies
that the locations of metamaterial elements will be changing relative to one
another. In this paper, we argue that if the metamaterial elements would be
accurately localizable, this location information could potentially be utilized
for enabling novel SDM applications, as well as for optimizing the control of
the elements themselves. To enable their localization, we assume that these
elements are controlled wirelessly through a Terahertz (THz)-operating
nanonetwork. We consider the elements to be power-constrained, with their sole
powering option being to harvest energy from different environmental sources.
By means of simulation, we demonstrate sub-millimeter accuracy of the two-way
Time of Flight (ToF)-based localization, as well as high availability of the
service (i.e., consistently more than 80% of the time), which is a result of
the low energy consumed in the localization process. Finally, we qualitatively
characterize the latency of the proposed localization service, as well as
outline several challenges and future research directions.
