OFDM receiver for long multipath interferences via frequency-domain identification approach

Guard interval is applied in OFDM systems to reduce the interferences caused by multi-path effects. However, in high-speed data transmission or mobile communications, some multi-path interferences have longer delay time than the guard interval occasionally. Under such situations, not only ISI (inter-symbol interferences) but also ICI (inter-carrier interferences) occur in the received signal. ISI and ICI deteriorate the orthogonality of the sub-carriers, and make the signal recovery and channel identification very difficult. In this work new channel identification algorithms are proposed to compensate the spectral leakage errors in the OFDM receivers. It is clarified that most of the computation in the algorithms can be performed in the frequency domain through the fast Fourier transform, so they have very low computational complexity and can easily be implemented for the receiver design or direct equalization.