Polar-OTFS System for Underwater Acoustic Communication

In underwater communication environments, significant delays and Doppler spread pose challenges to the reliability of traditional communication schemes. In this paper, we present a polar coded orthogonal time frequency space (Polar-OTFS) system that significantly improves transmission performance in underwater communication. On the transmitting side, the system first performs polar encoding, followed by OTFS mapping and transmission. On the receiving side, the system incorporates the unitary approximate message passing (UAMP) detection algorithm, ensuring efficient and precise time-frequency synchronization detection. Furthermore, to mitigate the impact of deep fading in offshore environments, the system incorporates a Dual-Threshold Successive Cancellation List decoding algorithm (DT-SCL), which adaptively adjusts the initial and maximum list size based on channel estimation, thereby enhancing decoding efficiency. Ocean experiment results demonstrate that the proposed system achieves error-free transmission over a distance of 25 kilometers at a transmission rate of 3 kbps in a marine environment at a depth of 1200 meters, showcasing exceptional communication performance and robustness.