Analysis of channel estimation error for OFDM reception over severely time-dispersive channels

The accuracy of equalization in the demodulation of orthogonal frequency division multiplexing signals is directly dependent on the density of pilot carriers in the signal and the delay dispersion of the propagation channel. In this paper, the error introduced by an insufficient pilot density with respect to the channel delay dispersion is theoretically analyzed. An expression is derived for the average channel estimation error given an OFDM pilot density and channel power delay profile. Based on this expression, the effect of channel estimation error on the perceived signal-to-noise ratio in the receiver demodulation is approximated. Results of the theoretical analysis and approximation are compared to simulations of OFDM transmitted over time-dispersive channels.