A new pilot design method for OFDM systems with virtual subcarriers

In this paper, a new pilot design method for orthogonal frequency division multiplexing (OFDM) systems with virtual subcarriers is proposed. The proposed scheme minimizes a simple function relevant to the mean-square error (MSE) of the least squares (LS) channel estimate instead of minimizing the MSE itself. As a result, the suboptimal pilot subcarriers can be obtained efficiently by sequentially solving several one-dimensional optimization problems. Comparing with the partially equispaced pilot design which is commonly used in many protocols, the proposed scheme is more robust to the system parameters and can provide much more accurate channel estimate for large channel lengths.