Cooperative Control for Antenna Array Calibration in OFDMA/TDD Systems

This paper proposes cooperative control for antenna array calibration to exploit channel reciprocity in OFDMA/TDD systems. The proposed scheme seeks a cooperative supporter which is another terminal or a fixed station close to the terminal. In cooperative calibration mode, the terminal compensates mismatch of analog gains between antennas, based on bidirectional channel measurements between the terminal and the supporter. The proposed scheme selects adaptively cooperative or normal calibration mode through a base station, depending on the terminal´s situation. The numerical results show that the proposed scheme improves calibration accuracy significantly compared to the case of no cooperative calibration. The proposed scheme keeps phase error less than 5deg in any position of terminal in a cell, maintaining practical amount of control signalling and complexity.