3) mmwave: Wireless networks are expected to face congestion
if no new spectrum is used. Recent studies suggest that
mm-wave frequencies could be used to augment the currently
saturated 700 MHz to 2.6 GHz radio spectrum bands for wireless
communications [33], [34]. The use of Millimeter Wave is
challenging. Little knowledge about cellular mm-wave propagation
in densely populated indoor and outdoor environments
is available, comparing to other more used bands. In fact, the
rather hostile propagation environment at these frequencies, in
addition to hardware equipment costs, prevented so far the use
of this band, unless some beamforming using large antenna
arrays is used. These arrays should allow narrow beams to
communicate. Novel transceivers hardware designs are needed
to realize such functions. An example of ongoing researches on
mwave is at New York University (NYU) and NYU-Poly who
established the NYU WIRELESS research center, to create
new technologies and fundamental knowledge for future mmwave
wireless devices and networks [35].