Performance evaluation of T-transform based OFDM in underwater acoustic communications

This paper dresses the implementation of an orthogonal frequency division multiplexing (OFDM) based multicarrier UWA communication system adopting a novel transform called T-transform. It combines the Walsh-Hadamard transform (WHT) and the discrete Fourier transform (DFT) into a single fast orthogonal unitary transform which increases channel diversity order without sacrificing any throughput. The proposed system uses pilot subcarriers for channel estimation and bit-interleaved coded modulation with iterative decoding (BICM-ID) as forward error correction (FEC) code for better bust error correction. Performance of the T-transform is compared to discrete cosine transform (DCT) based OFDM systems and conventional OFDM systems. Both tank test results and sea trial results reveal that the proposed T-OFDM system achieves significant performance improvement over DCT based OFDM and conventional OFDM in a frequency selective fading channel.