Time-Domain Oversampled Receiver for OFDM in Underwater Acoustic Communication

In this paper, we propose a time-domain oversampled receiver for orthogonal frequency division multiplexing (OFDM) in underwater acoustic communication. Without changing the structure of the transmitter, significant gains are acquired by time- domain oversampling at the receiver. Using time- domain oversampling, the energy of transmitted symbols is concentrated on the first N subcarriers, while additive Gaussian noises are distributed in all the subcarriers. Because of the sparsity of underwater acoustic channels, most energy of the channel impulse responds is concentrated on a few paths, and other positions are submerged by noises. Channel estimation based on the discrete Fourier transform is employed to eliminate noises. After estimating the energy of additive Gaussian noises, the truncation of channel impulse responds eliminates the majority of noises. Simulations are implemented in multipath channels and fading channels. Without changing the structure of the transmitter, the proposed oversampled receiver outperforms the conventional receiver in bit error rate (BER) performances significantly, with a little increased computational complexity.