Iterative SDR-based Hybrid Precoding Algorithm for mmWave massive MIMO Systems

Practical hybrid precoding algorithms for millimeter wave massive multiple-input multiple-output (mmWave massive MIMO) systems with huge number of radio frequency (RF) chains must achieve high spectral efficiency at low complexity. In this paper, we consider the hybrid precoder with sub-connected structure which presents reduced power consumption and low-complexity hardware implementation. Then, we propose a new hybrid precoder based on iterative semidefinite relaxation (ISDR) approach. The proposed ISDR algorithm iteratively realizes the SDR one using the Gauss-Seidel (GS) method. We analyze the spectral efficiency and computational complexity of our ISDR-based hybrid precoder, we compare them to those of previously proposed hybrid precoders in the literature, and we prove that our proposal significantly reduces the computational complexity while providing spectral efficiency slightly comparable to that of the SDR-based one.