Efficient Estimation of Fast Fading OFDM Channels

Channel estimation is a key issue to OFDM systems no matter for inter-carrier interference cancellation or for symbol detection. The difficulty with a fast-fading OFDM channel lies in that the channel over one OFDM symbol interval is characterized by a channel matrix whose dimensions much exceeds the total number of subcarriers. Consequently, the channel estimation techniques developed for slowly fading channels are of little use. In this paper, we show how to parsimoniously parameterize an OFDM channel matrix by representing each path-coefficient vector through its eigen structure. The resulting unknown parameters are much less than that of the original channel matrix making their estimation possible. The new technique is superior to its conventional counterpart as evidenced by simulation results.