Enhanced Adaptive Downlink Transmission in MIMO-OFDM Systems by Hardware-Based Calibration

In this paper, a hardware-based calibration scheme at the base station is used to mitigate the impact of the non-reciprocal transceivers in a time division duplex (TDD) multiple-input-multiple-output orthogonal-frequency-division-multiplexing (MIMOOFDM) system. The calibration setup consists of two single-pole-double-throw (SPDT) switches to bypass the calibration and the data signals. Additionally, an attenuator is needed to avoid overdriving the receive chain of the transceivers. Simulation results show that this calibration scheme results in lower bit error rate (BER) values of the communication system. These results are underlined by measurement results exploiting the low-cost and simple-technology calibration solution.