  Millimeter-wave (30-300 GHz) and Terahertz-band communications (0.3-10 THz)
are envisioned as key wireless technologies to satisfy the demand for
Terabit-per-second (Tbps) links in the 5G and beyond eras. The very large
available bandwidth in this ultra-broadband frequency range comes at the cost
of a very high propagation loss, which combined with the low power of mm-wave
and THz-band transceivers limits the communication distance and data-rates. In
this paper, the concept of intelligent communication environments enabled by
Ultra-Massive MIMO platforms is proposed to increase the communication distance
and data-rates at mm-wave and THz-band frequencies. An end-to-end physical
model is developed by taking into account the capabilities of novel intelligent
plasmonic antenna arrays which can operate in transmission, reception,
reflection and waveguiding, as well as the peculiarities of the mm-wave and
THz-band multi-path channel. Based on the developed model, extensive
quantitative results for different scenarios are provided to illustrate the
performance improvements in terms of both achievable distance and data-rate in
Ultra-Massive MIMO environments.
