An adaptive antenna using orthogonal projection for OFDM transmission

OFDM systems are known to outperform single-carrier systems in a multipath environment. However, multipath waves, whose delay times are longer than the guard interval, cause intersymbol interference, because of which the performance of the system degrades. The effectiveness of adaptive arrays in overcoming this problem has been investigated. This paper proposes the use of an adaptive array with orthogonal projection for OFDM transmission with zero carriers. In the proposed method, the projection matrix is calculated from the zero carriers including the interference wave, and the matrix is used to suppress the undersired waves. Then, maximal-ratio combining is performed in each subcarrier. Simulation results show that the proposed method effectively suppresses undesired waves.