A Unifying Design of Hybrid Beamforming Architectures Employing Phase Shifters or Switches

Hybrid beamforming (BF) architectures employing phase shifters or switches reduce the number of required radio frequency chains and the power consumption of base stations that employ a large number of antennas. Due to the inherent tradeoff between the number of radio frequency chains, the complexity of the employed analog and digital BF algorithms and the achieved spectral and energy efficiency, designing hybrid BF architectures is a complex task. To deal with this complexity, we propose a unifying design that is applicable to architectures employing either phase shifters or switches. In our design, the analog part of the hybrid BF architecture maximizes the capacity of the equivalent channel, while the digital part is updated using the well-known block diagonalization approach. We then employ the proposed joint analog-digital beamforming algorithm on four recently proposed hybrid architectures and compare their performance in terms of spectral and energy efficiency, and find that the proposed analog-digital BF algorithm outperforms previously proposed schemes. We also find that phase shifter-based architectures achieve high spectral efficiency, whereas switching-based architectures can boost energy efficiency with increasing number of base station antennas.