A leakage-based hybrid beamforming design for multi-user mmWave massive MIMO systems

In massive multiple-input multiple-output systems, hybrid beamforming (HBF) is an attractive technique due to its excellent tradeoff between system performance and hardware implementation cost. In this paper, the signal-to-leakage-plus-noise ratio is considered as the optimization criterion and investigate the HBF design for multi-user millimetre-wave massive multiple-input multiple-output systems. To overcome the difficulty of solving the multi-variable design problem, a novel two-stage HBF scheme to optimize the analogue and digital beamformers are proposed. In particular, an orthogonal matching pursuit-based method and a joint design method are introduced respectively to find the solution in the analogue stage. Then, in the digital stage, the digital precoder and combiner are designed to suppress the inter-user interference plus noise, aiming at maximizing the sum-signal-to-leakage-plus-noise ratio of multi-user systems. Simulation results show that the proposed HBF scheme with lower complexity can achieve superior performance over the existing HBF schemes. Moreover, it is also indicated that the performance of the HBF scheme remains strong even with the imperfect channel state information.