Antenna arrays are a key feature in mmWave
systems. Large arrays can be used to keep the
antenna aperture constant, eliminating the frequency
dependence of path loss relative to omnidirectional
antennas (when utilized at one side
of the link) and providing a net array gain to
counter the larger thermal noise bandwidth
(when utilized at both sides of the link). Adaptive
arrays with narrow beams also reduce the
impact of interference, meaning that mmWave
systems could more often operate in noise-limited
rather than interference-limited conditions.
Since meaningful communication might only
happen under sufficient array gain, new random
access protocols are needed that work when
transmitters can only emit in certain directions
and receivers can only receive from certain
directions. Adaptive array processing algorithms
are required that can adapt quickly when beams
are blocked by people or some device antennas
become obscured by the user’s own body