Antenna calibration using channel prediction for time-varying channels

Traditional antenna calibration methods for time division duplex (TDD) systems assume that the free-space channel remains the same during calibration, which is unreasonable under the high-speed rail and other time-varying channel scenarios, and will cause calibration error due to time variability. This paper proposes an antenna calibration method for time-varying channels. In the proposed method, the transceiver first sequentially sends a pilot signal to obtain equivalent downlink and uplink channel responses. Then, by predicting the downlink (uplink) channel response fed back from the receiver using the channel prediction algorithm, the transmitter obtains the channel response corresponding to the channel response on uplink (downlink). Finally, the transmitter calculates the transmission calibration factor through the prediction value. Compared with the traditional antenna calibration method, this method can improve the accuracy of the calibration factor. Simulation results show that the performance degradation of antenna calibration can be caused by time-varying channels and the proposed method can well compensate for the performance loss and significantly improve the antenna calibration performance for time-varying channels.