Practical channel interpolation for OFDMA

This paper addresses piecewise frequency domain interpolation for OFDMA channels when raw estimates are given on a sparse grid of pilot carriers in a fraction of the spectrum only. Starting from the optimal linear interpolation which needs a-priori information on the power delay profile and the SNR, we develop robust suboptimal schemes that do not require such information. One scheme is based on singular value decomposition and it allows the estimation of the SNR. In practice, however, it is difficult to obtain the required information on the power delay profile. To ensure robustness of the filter to mismatched channel parameters, a favorable assumption of the power delay profile is suggested for the filter design. It is further shown that a full-spectrum interpolation assembled from multiple piecewise interpolation results has a dramatically reduced complexity which makes it suitable for real-time implementation.