Channel estimation in OFDM systems based on comb-type pilot arrangement over doubly-selective channels

The time and frequency selectivity in doubly-selective channels corrupt the orthogonality between different subcarriers in an orthogonal frequency-division multiplexing(OFDM) symbol and induce significant inter carrier interference(ICI). To mitigate this effect, many channel estimation and equalization based ICI mitigation schemes had been proposed. However, most of them are based on pilot pattern different from comb-type arrangement, therefore not applicable for many widely applied standards of which pilot tones are equispacedly spread in each symbol, such as DVB-T. For these systems, we resort to an two-stage estimation schemes to obtain accurate channel impulse response. In this paper, three fine estimation schemes are proposed and compared. Simulation results indicate that our proposed schemes can substantially reduce the mean squared error (MSE) of channel estimation in doubly-selective channels.