Channel Estimation for Pilot-Aided OFDM Systems in Single Frequency Network

In single frequency network (SFN), there exist some special long delay spread channels as well as conventional multipath channels. For pilot-aided orthogonal frequency division multiplex (OFDM) systems, channel estimation is usually accomplished by interpolation with pilots. However, few pilot sub-carriers exist within the coherent bandwidth of the long delay spread channels in SFN. In this case, conventional frequency domain interpolation methods cannot work properly. In a narrowband channel, this paper indicates that both the real and the imaginary parts of channel frequency response can be accurately approximated as a sine-wave with DC offset. For many practical pilot-aided OFDM systems, the bandwidth of the narrowband channel mentioned before is comparable with the interval between several adjacent pilot sub-carriers. Then this paper proposes a sine-wave based frequency domain interpolation method for the channel estimation of pilot-aided OFDM systems in SFN. As simulation results show, the proposed method performs well in the long delay spread channel, whereas the mismatched Wiener interpolation filter (WIF) estimates channel response inaccurately. Moreover, the proposed method gives accurate channel estimation in conventional multipath channels, especially for the systems which adopt high order modulations.