Hybrid Beamforming for Millimeter Wave Massive Multiuser MIMO Systems Using Regularized Channel Diagonalization

This letter presents a novel hybrid analog-digital beamforming design for massive multiuser MIMO downlink transmission in sparse millimeter wave channels. The proposed hybrid regularized channel diagolnalization (HRCD) scheme combines analog (RF) phase-only beamforming with linear digital (baseband) precoding based on regularized channel diagonalization. Being a hybrid beamforming design utilizing simple non-iterative processing, HRCD provides a low complexity solution that is capable of outperforming several other hybrid schemes including those based on block diagonalization, as shown through simulations. Furthermore, it is also shown that the performance remains strong even with the use of finite-resolution phase shifters.