On the Equivalence of Hybrid and Digital Beamforming in Multi-User Scenarios

Abstract:
Utilizing hybrid beamforming (HBF), a combination of an analog beamforming (ABF) network with digital weighting of a few selected beams, is a promising approach to reduce the prohibitively high power consumption and hardware complexity of large antenna arrays operating in the millimetre-wave (mmWave) and sub-terahertz range. This paper numerically evaluates the performance of a proposed HBF communications system using a Butler matrix as ABF network compared to fully digital beamforming (DBF) for different multi-user scenarios. First, the performance is compared for a line-of-sight (LOS) channel model, which is then extended to a multipath fading channel model. Furthermore, the influence of the number of radio-frequency (RF) chains used on the performance is investigated. Our simulation results show that HBF is able to achieve a performance which is comparable to the performance of DBF with a small loss, if the number of RF chains is chosen appropriately.