Yasuhiro Yano

Antenna Array Calibration Using Frequency Selection in OFDMA/TDD Systems

This paper proposes a new antenna array calibration using frequency selection in OFDMA/TDD systems. In the proposed method, subbands or frequencies of good channel conditions are initially selected for accurate channel measurement. Next, the relative calibration is performed at the selected subbands, in which mismatch of analog gains in multiple antennas is compensated by use of measured channel parameters on uplink and downlink. Third, the calibration parameters are interpolated in frequency domain for whole bandwidth. The proposed method keeps more accurate channel reciprocity for whole bandwidth than the conventional method which does not use the frequency selection. The proposed method is effective in exploiting channel reciprocity at both base station and terminals keeping feasible feedback amount and low-cost operation.

Performance of DS/GMSK/PSK modem using four-phase correlator

Direct-sequence spread-spectrum (DS/SS) system has been extensively studied for land mobile communications because of the notable and attractive features such as its robustness and applicability to code division multiple access (CDMA). We propose a DS/SS modulation method which employs Gaussian-filtered minimum-shift-keying (GMSK) and permits simple code acquisition. The modulated signal can be demodulated by a four-phase correlator which can obtain the correlation value of the received signal even if a phase difference between the transmitter and the receiver exists. The bit error performance obtained by the hardware experiments ensures the validity of this modulation method.

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 terminals 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.