MS-PDPM: a bio-inspired framework for underwater wearable acoustic communication

Reliable underwater acoustic communication (UAC) for underwater wearables transmitting vital physiological data and low-rate voice signals is essential for underwater operations. Cetacean clicks, which are prevalent biological sound signals in marine environments, have inspired the research of bio-inspired UAC (BUAC) that can meet these requirements. Traditional click-based modulation techniques like pulse position modulation (PPM) and pattern time delay shift coding (PDS) demonstrate good energy efficiency, but they suffer from two critical challenges: limited information density and vulnerability to detection, as identification methods targeting PDS-based BUAC have already emerged. This paper proposes a novel modulation scheme, multi-symbol pulse delay position modulation (MS-PDPM), which integrates multi-pulse position modulation (MPPM) and PDS to enable reliable communications for underwater wearables. MS-PDPM offers two key benefits: it significantly enhances data transmission rates while producing signals that closely mimic natural cetacean clicks. The biomimetic properties of MS-PDPM make transmissions substantially more difficult to distinguish from natural marine biological sounds, reducing ecological disruption while reliably transferring vital physiological data and safety information from underwater wearable sensors. Simulation results in shallow water acoustic channels validates the effectiveness of the proposed MS-PDPM scheme.