Time-Domain Oversampled OFDM Communication in Doubly-Selective Underwater Acoustic Channels

This paper investigates the time-domain oversampled cyclic-prefix orthogonal frequency division multiplexing (CP-OFDM) system for communication over doubly-selective underwater acoustic channels. Channel estimation is based on two different time-varying channel models. One is the basis expansion model (BEM), the other is the Doppler-rate model (DRM). Exploiting the sparsity of underwater acoustic channels, orthogonal matching pursuit (OMP) is employed to obtain the time-varying channel state information (CSI). The receiver operates without any prior knowledge of the statistics of the CSI, as this information usually is unavailable for underwater acoustic channels. Channel estimation error and bit error rate (BER) performance of the system are demonstrated through numerical simulations. Results show that the oversampled CP-OFDM achieves significant gains over the conventional symbol-rate sampled system.