Channel reciprocity calibration algorithm for massive MIMO TDD systems based on antenna mutual coupling

The non-ideality of the RF and the time-varying characteristics of the channel affect the reciprocity of the time division duplex (TDD) mode in a multiple-input multiple-output (MIMO) system. The mutual coupling affects the correlation of the channel matrix. Massive MIMO reciprocity joint calibration algorithm based on mutual coupling effect is proposed. In the proposed algorithm, the mutual coupling effect between antennas is introduced into the channel matrix and the over-the-air (OTA) calibration algorithm is combined with the AR model based prediction channel matrix. The algorithm achieves simultaneous calibration for the loss of reciprocity caused by radio frequency non-ideality and channel time-varying characteristics. The simulation results show that the algorithm can improve the system capacity, reduce the error rate, and calibrate the loss of reciprocity. This algorithm can provide reference for the multi-factor joint calibration of massive MIMO systems.