348 Cyber-Physical Systems: From Theory to Practice
MIMO, but its effect on massive MIMO appears to be much more radical than in classical MIMO
systems [12]. Other challenges that need to be addressed are the realization of distributed process-
ing systems, synchronization of the antenna units, and diminishing the computational complexity
required to implement massive MIMO systems.
14.3.1.2 Millimeter-Wave Technology:
While spectrum has become limited at microwave frequencies, it is abundant in the mmWave fre-
quency bands. Microwave cellular systems are characterized by having extremely valuable but
limited spectrum. Around 600 MHz of bandwidth are currently in use for mobile communications
and are divided among several operators [16]. Two ways