Low-Complexity Hybrid Analog and Digital Precoding for mmWave MIMO Systems

Abstract

In millimeter-wave (mmWave) massive MIMO systems, to decrease hardware cost and energy consumption, hybrid analog and digital precoding is preferred to pure digital precoding. In this paper, a hybrid precoding method for sub-connected mmWave MIMO systems is developed. To start with, we propose to formulate the hybrid precoding matrix as a Kronecker product of an analog precoding matrix and a digital precoding vector, by enforcing phase shifters connecting to each radio-frequency chain to share the same set of coefficients. Then, the optimal design of the digital and analog precoding matrices is formulated as the nearest Kronecker product (NKP) problem, which is analytically tractable. Finally, a low-complexity algorithm is developed to implement the proposed hybrid precoding method. Simulation results corroborate that the NKP-based hybrid precoding is near-optimal and achieves higher data rates than the successive interference cancellation method. Moreover, the energy efficiency of the proposed design is much higher than the fully-connected architecture.