Givens rotation based column-wise hybrid precoding for millimeter wave MIMO systems

Abstract

Hybrid precoding is a promising technique for millimeter wave (mmWave) large-scale multiple-input multiple-output (MIMO) systems. This paper considers a hybrid precoding architecture which is composed of a reductive digital precoder and a phase-only control radio frequency (RF) precoder, and proposes a Givens rotation based column-wise hybrid precoding algorithm. In the proposed algorithm, the digital precoding matrix and the RF precoding matrix are alternatively optimized column by column. For the optimization of the constant modulus RF precoding vector, it is interesting that the optimal solution can be expressed as a product of an arbitrary constant modulus vector and a series of Givens rotation matrices. Accordingly, the original problem is transformed into an unconstrained problem of the Givens rotations, which is easy to be solved. After obtaining the optimal RF precoding vector, the optimal digital precoding vector can be given through the least squares method. Simulation results show that the proposed algorithm can approach the performance of the fully digital precoder effectively and enjoy a higher spectral efficiency than previous works under various channel environments and different system settings.