Passband-Baseband Joint Equalization for Bio-Inspired Phase-Modulated Communication in Underwater IoT Networks

The Internet of Underwater Things (IoUT) has emerged as a promising paradigm for marine applications, yet faces significant challenges in achieving secure and reliable network communications. In IoUT networks, underwater acoustic communication struggles to maintain both covert operation and efficient data transmission, which are crucial for sensitive monitoring and surveillance applications. Bio-inspired communication schemes that mimic dolphin whistles offer an innovative solution for IoUT networks by embedding information within natural marine sounds, enhancing both communication security and network connectivity. However, in phase-modulated bionic camouflage communication, the multi-path effects of the underwater acoustic channel cause overlapping of multiple whistles at the receiver, severely degrading IoUT network performance and limiting practical applications. To address these challenges in IoUT networks, we propose a novel joint passband-baseband equalization method for bio-inspired phase-modulated communication. The receiver architecture combines an improved learning rate-fast transversal RLS (LR-FTRLS) equalizer for channel shortening in the passband with a decision feedback equalizer (DFE) in the baseband, specifically optimized for underwater IoT scenarios. The effectiveness of the proposed scheme has been verified through both shallow and deep-sea simulations. Sea experiment further demonstrate the system’s practical viability, achieving 300 bps with a bit error rate below 10-3 at 9 km range, demonstrating its effectiveness for high-rate covert underwater communication. This work represents a significant advancement in underwater IoT networks, offering enhanced security, improved reliability, and increased data transmission capabilities for various marine IoT applications including environmental monitoring, underwater surveillance, and marine resource exploration.