Symbol-Level Hybrid Precoding in mmWave Multiuser MISO Systems

Recently, symbol-level precoding has emerged as a novel efficient solution in multi-user multi-antenna downlink systems, since it can exploit multi-user interference (MUI) and transform it into useful signal. In this correspondence, we attempt to apply symbol-level precoding into the well-known hybrid precoding architecture in multi-user multi-input single-output (MU-MISO) millimeter wave (mmWave) communication systems. Particularly, we aim to design the symbol-varying digital precoder and the analog precoder with low-resolution phase shifters (PSs) to optimize symbol detection performance under the transmit power constraint and the discrete phase constraint. To handle this difficult joint optimization problem, we propose to minimize the Euclidean distance between the optimal fully-digital precoder and the hybrid precoder. An efficient iterative algorithm is developed to solve this problem. Simulation results demonstrate the advantages of symbol-level precoding and validate the effectiveness of our proposed symbol-level hybrid precoding algorithm.