Switch-Based Hybrid Precoding in mmWave Massive MIMO Systems

In mmWave communications, large-scale arrays can be very advantageous. In such arrays, switch-based hybrid precoding (beamforming) is very promising in terms of energy efficiency and reduced complexity, as opposed to phase-shifter structures for beamforming. However, switch-based structures are binary, which means that the design of an optimum beamformer, at large-scale in the analog domain, is a difficult task. We address this problem and propose a new method for the design of a switch-based hybrid precoder for massive MIMO communications in mmWave bands. We first cast the relevant maximization of mutual information as a binary, rank-constrained quadratic maximization, and solve it iteratively for each column of the analog precoder. The solution is then effectively approximated via a set of relaxations and sequential convex programming (SCP). Finally, we show the feasibility, and effectiveness of our method via numerical results.