An antenna array can control the directivity and shape of the transmitted signal.
The signal strength at the receiver is maximized using maximum ratio beamforming, to support higher data speeds.
The strength can also be minimized using zero-forcing beamforming, to protect unintended receivers from disturbances. In the fourth video of this series, Prof. Emil Björnson demonstrates these categories experimentally using over-the-air transmission of a mmWave signal and explains how one achieves them by phase-shifting the transmitted signals.
Theory and practical utilization fit together, in both line-of-sight and non-line-of-sight propagation. Beamforming is used in all 5G systems, both in sub-6 GHz and mmWave bands.