Turbo equalizer for OFDM signals in multipath and multi-Doppler environment

In OFDM transmission, a loss of subcarrier orthogonality due to the Doppler-spread of the channel leads to inter-carrier interference (ICI), especially under a mobile environment. ICI causes a significant degradation of bit error rate (BER) characteristics and this influence becomes larger as the carrier frequency or the velocity of the mobile receiver increases. A method is proposed to reduce ICI caused by the residual carrier frequency offsets and multiple Doppler-spreads of the channel. Simulation results show that the proposed ´turbo scheme´ provides better BER performance than a conventional receiver, or a receiver employing a decision feedback equalizer (DFE), especially at higher signal-to-noise ratios.