Doppler Scaling Factor Estimation and Receiver Design for Underwater Acoustic Communication

Due to very low propagation speed of acoustic waves, underwater communication via acoustic waves observe a significant Doppler scaling in the received signal. In addition, due to severe frequency selective fading in underwater acoustic channel, the distinct multi-paths may induce different Doppler scaling factor. In this paper, we investigate a transmission strategy in which we append preamble and post-amble in the data frame to estimate the Doppler scaling factor. The frequency selective fading coefficients and additive noise in the system model are statistically characterized by Nakagami and Generalized Gaussian distribution, respectively. Further, the transmit data is assumed to be orthogonal frequency division multiplexing (OFDM) modulated to mitigate the frequency selective nature of underlying channel. In our analysis, we consider two scenarios: (1) multi-paths have common Doppler scaling factor and (2) multi-paths have different Doppler scaling factor. For both the scenarios, we propose receiver algorithms to detect OFDM symbols corrupted by multi-path propagation. We also discuss the improvement in bit error rate performance by exploiting maximal ratio combining scheme. Finally, we validate our approach in the proposed techniques by showing improvement in bit error rate performance via simulation under various signal to noise ratio and fading conditions.