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Efficient pilot patterns for channel estimation in OFDM systems over HF channels

In this paper, the distribution of pilot symbols in the time-frequency lattice of a multicarrier system for HF communications has been analysed. The pilot density of an OFDM modem based on the HFDL standard can be reduced, so the data rate can be about 3600 bit/s. An hexagonal pilot pattern has been proposed and compared with rectangular geometries. Hexagonal distribution of the pilots is optimum in terms of sampling efficiency and it provides better performance in terms of BER.