Online Calibration of Phase Shifter Network for mmWave Massive MIMO Systems in Multipath Channels

This paper develops a novel approach to the calibration of the phase shifter network (PSN) in millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) communication systems under multipath channel scenarios. Specifically, we formulate the core phase deviation estimation problem in the calibration task as an optimization program with unimodular constraints. Efficient algorithms are then developed to estimate the phase deviations that need to be calibrated. To gauge the performance of the proposed schemes, we derive the Cramer-Rao lower bounds (CRLBs) for the phase estimates. Numerical results validate the effectiveness of our approach by showing that the proposed algorithm yields estimates whose mean squared errors (MSEs) are close to the CRLBs.