The Ultimate Weapon for Ultra-Broadband 6G: Digital Beamforming and Doubly Massive mmWave MIMO

The use of millimeter waves for wireless communications is one of the main technological innovations of 5G systems with respect to previous generations of cellular systems. Their consideration, however, has been up to now mainly restricted to the case in which analog or, at most, hybrid analog-digital beamforming structures were used, thus posing a limitation on the multiplexing capabilities and peak data rates that could be theoretically achieved at these frequencies. Recent progress in the field of electronics, however, has made the energy consumption of digital beamforming structures at least on par with that of analog beamforming, thus redeeming them from the ghetto they had been placed in over the last year. Digital beamforming, coupled with the use of large antenna arrays at both sides of the communication link, promises thus to be one of the secret weapons of future 6G networks, capable of unleashing unprecedented values of spectral and energy efficiency for ultra-broadband connectivity.