Optimal pilot superimposition for zero-padded block transmissions

This paper develops an optimal pilot superimposition scheme for zero-padded single-carrier transmissions. With the goal of minimizing the mean-squared error of channel estimates which have been acquired from those superimposed pilots based on the first-order statistics, it is proved that the optimal pilot sequence should contain only a single non-zero pilot symbol, and this single non-zero pilot symbol must be placed within the guard interval with its exact location depending on the channel power profile. Several illustrative examples are presented for some commonly used channel power profiles. Both theoretical analysis and numerical simulations confirm the merits of our optimal design, and show considerable performance improvement over existing competing schemes