Low Pilot Ratio Channel Estimation for OFDM Systems

Doubly-selective channel estimator for orthogonal frequency division multiplexing (OFDM) systems is proposed in this paper. Based on the generalized complex exponential basis expansion model (GCE-BEM), we describe the time-variant channel with time-invariant coefficients over multiple OFDM blocks. The time variation of channel destroys the orthogonality between subcarriers. The resulting channel matrix in the frequency domain is no longer diagonal, but the main interference comes from the near subcarriers. Based on this, we propose a least-square (LS) channel estimator with low pilot ratio. The proposed estimator is with the advantages of low pilot ratio and robustness against inter-carrier interference.