A Phase Calibration Method Based on L1-norm Minimization for Massive MIMO Systems

Beam division multiple access (BDMA) transmission scheme is one of the transmission schemes for massive multiple-input multiple-output (MIMO) systems. However, when taking radio frequency (RF) gains of different antennas into account, the performance of BDMA transmission may degrade severely. In this paper, we investigate the calibration method of RF mismatches for BDMA transmission. We first analyze the performance impact of amplitude mismatches and phase mismatches respectively. Then, we focus on the main factor, phase mismatches. After deriving the relationship between sparsity of channel vector and its L1-norm, we propose a phase calibration method based on L1-norm minimization. In the proposed method, initial feasible solution is obtained in one sub-carrier and channel state information (CSI) in multiple sub-carriers is applied to obtain the calibration matrix. Simulation results verify the feasibility of the proposed method and show the significant improvement of system performance.