In underwater acoustic communication (UWAC), the propagation path exhibits doubly selective characteristics due to the slow speed of sound and the presence of long-delay multipath components caused by reflections from the sea surface and seabed, as well as Doppler effects. These characteristics significantly differ from terrestrial wireless communication. In orthogonal frequency division multiplexing (OFDM) transmission, such effects necessitate a long cyclic prefix (CP), leading to limited transmission capacity due to overhead or sensitivity to Doppler distortion. To address these challenges, this study proposes an approach that maintains a short CP length in OFDM symbol design while suppressing delayed paths by leveraging diversity gain through the deployment of multiple receiving elements. Furthermore, by extending this concept to multiple-input multiple output (MIMO) spatial multiplexing, the proposed system aims to achieve much higher data throughput. Simulation results are presented, and experimental efforts using an ultrasonic anechoic water tank are introduced to demonstrate the feasibility of the proposed approach.
Maruta et al. (Wed,) studied this question.
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