OFDM using Steering Sinusoids for Underwater Acoustic Communication

Abstract: Among the different modulation techniques used for acoustic communication underwater, Orthogonal Frequency Division Multiplexing (OFDM) still happens to be the best and an extremely effective modulation scheme. However, the major hurdle which the Under Water Acoustic (UWA) communication encounters is the challenges posed by the dynamic nature of the sea, which degrade the quality of the signal. The non-uniform effects of the sea dynamics due to wind or platform motion may result into inter-carrier interference causing a complete distortion of the signal. To avoid such distortions, relative changes in terms of Doppler factors need to be tracked properly and included in the system designing. Adapting to this ideology, a new OFDM approach based on Steering Sinusoids has been introduced in this paper. The Steering Sinusoids will be able to track and correct the fast oceanic variations incurred within a symbol length. These recorded changes, either uniform or non-uniform, are used to reduce the intensity of the Doppler spreads. The proposed system can be analyzed using the MATLAB simulation along with self-induced Doppler. Bellhop Ray tracing algorithm has been used for generating static multipath channel models.

Keywords: OFDM, UWA, Steering Sinusoids, BER, sea dynamics, Doppler spreads, multi-paths, Bellhop ray tracing, ZP-OFDM