  One of the critical challenges of operating with the terahertz or
millimeter-wave wireless networks is the necessity of at least a strong
non-line-of-sight (NLoS) reflected path to form a stable link. Recent studies
have shown that an economical way of enhancing/improving these NLoS links is by
using passive metallic reflectors that provide strong reflections. However,
despite its inherent radio advantage, metals can dramatically influence the
landscape's appearance - especially the indoor environment. A conceptual view
of escaping this is by using transparent reflectors. In this work, for the very
first time, we evaluate the wireless propagation characteristics of passive
transparent reflectors in an indoor environment at 28 GHz, 39 GHz, 120 GHz, and
144 GHz bands. In particular, we investigate the penetration loss and the
reflection characteristics at different frequencies and compare them against
the other common indoor materials such as ceiling tile, clear glass, drywall,
plywood, and metal. The measurement results suggest that the transparent
reflector, apart from an obvious advantage of transparency, has a higher
penetration loss than the common indoor materials (excluding metal) and
performs similarly to metal in terms of reflection. Our experimental results
directly translate to better reflection performance and preserving the radio
waves within the environment than common indoor materials, with potential
applications in controlled wireless communication.
