  Software-defined metamaterials (SDMs) represent a novel paradigm for
real-time control of metamaterials. SDMs are envisioned to enable a variety of
exciting applications in the domains such as smart textiles and sensing in
challenging conditions. Many of these applications envisage deformations of the
SDM structure (e.g., rolling, bending, stretching). This affects the relative
position of the metamaterial elements and requires their localization relative
to each other. The question of how to perform such localization is, however,
yet to spark in the community. We consider that the metamaterial elements are
controlled wirelessly through a Terahertz (THz)-operating nanonetwork.
Moreover, we consider the elements to be energy constrained, with their sole
powering option being to harvest environmental energy. For such a setup, 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
localization. Finally, we provide the localization context for a number of
relevant system parameters such as operational frequency, bandwidth, and
harvesting rate.
