  The limited radio-frequency spectrum is a fundamental factor in the design of
wireless communication systems. The ever increasing number of wireless devices
and systems has led to a crowded spectrum and increased the demand for
versatile and multi-functional full-duplex wireless apparatuses. Recently,
dynamic and intelligent metasurfaces are explored as a prominent technological
solution to the current paradigm of spectrum scarcity by opportunistically
sharing the spectrum with various users. In general, intelligent metasurfaces
are dynamic, ultra-compact, multi-functional and programmable structures which
are capable of both reciprocal and nonreciprocal signal wave transmissions in a
full-duplex manner. The controllability and programmability of such
metasurfaces are governed through the dc bias and occasionally a
radio-frequency (RF) modulation applied to the the active components of the
unit cells of the metasurface, e.g., diodes and transistors. This article shows
that such intelligent metasurfaces can enhance the performance of wireless
communications systems thanks to their unique features such as real-time signal
coding, nonreciprocal-beam radiation, nonreciprocal beamsteering amplification,
and advanced pattern-coding multiple access communication.
