An improved OFDM channel estimation technique based on DDST with ICI mitigation over fast fading channel

For Orthogonal frequency-division multiplexing (OFDM) communication systems, the Doppler frequency offset due to the high speed movement destroys the orthogonality of subcarriers, resulting in the intercarrier interference (ICI), which will degrade the performance of the system. As a result, it is necessary to estimate the accurate channel to equalize the received symbols. On the other hand, the conventional pilot-assisted channel estimation scheme consumes valuable bandwidth. In this paper, an improved OFDM channel estimation technique with ICI mitigation is proposed, which utilizes data dependent superimposed training (DDST) approach to estimate the time-varying channel which is approximated by a basis expansion model (BEM). Based on this method, a more accurate channel estimation is obtained by modifying the structure of DDST at the transmitter and symbol shift cancellation scheme at the receiver. Furthermore, an iterative algorithm is employed to detect the symbols which are destroyed from DDST. The theoretical analysis and simulation results show that the mean square error (MSE) and the bit error rate (BER) performances are improved significantly in high-speed mobility conditions (more than 150 km/h) or high SNR (25 dB) compared to conventional DDST OFDM systems.