New estimation and equalization approach for OFDM under Doppler-spread channel

In OFDM transmission, a loss of sub-carrier orthogonality due to Doppler-spread of the channel leads to intercarrier interference (ICI), especially under mobile reception environments. ICI causes significant degradation of bit error rate characteristics and this influence becomes larger as the carrier frequency or moving velocity of the receiver increases. In this paper, a method to reduce the ICI caused by Doppler-spread of the channel is proposed. In the proposed method, the transmission channel is modeled by a combination of multiple Doppler-shifted propagation paths and their parameters such as attenuation, relative delay and Doppler-shift are estimated using scattered pilot symbols. Then, ICI is canceled by multiplying the inverse matrix of the estimated channel matrix to the received OFDM symbol vector. As the result of computer simulation, it is confirmed that the proposed method can improve the bit error rate characteristics under Doppler-spread channel.