OTFS for Mobile Underwater Acoustic Communications: Parameter Selection and Testing on Software-Defined Modems

Underwater acoustic (UWA) communication and networking is vital for various maritime applications, such as smart environmental monitoring, subsea infrastructure monitoring, and autonomous underwater vehicle operations. However, UWA systems face significant challenges due to the spatial and temporal variability of UWA channels, characterized by severe multipath propagation and the Doppler effect. Existing efforts to mitigate Doppler-induced distortions often increase redundancy or computational load. This paper addresses these challenges by designing, implementing, and evaluating an orthogonal time frequency space (OTFS) modulation scheme on software-defined acoustic modems. Utilizing delay-Doppler domain symbol mapping, OTFS demonstrates greater resilience to inter-symbol interference (ISI) in high-Doppler environments. We describe the OTFS system model, propose an algorithm for parameter selection, and present experimental results on Hydronet wideband modular software-defined modems, showcasing its potential for UWA communication systems.