DCT-based channel estimation for wireless OFDM systems with the hexagonal pilot pattern

When there are some virtual subcarriers and high Doppler frequency in practical orthogonal frequency division multiplexing (OFDM) system, we adopt discrete cosine transform (DCT)-based channel estimator instead of conventional DFT-based one to reduce the performance deterioration. And as hexagonal distribution of pilots is optimum in term of sampling efficiency, that is, it provides better performance than the rectangular one. So a two dimensional (2-D) DCT-based channel estimator with hexagonal pilot patterns is proposed, and detailed derivation is given. Simulation results show that the performance of the proposed method can well approach the 2-D Wiener filtering estimator.