Virtual Tethered Autonomous Underwater Vehicle for Real-Time Underwater Internet of Things

The establishment of high-speed optical links between marine platforms for underwater internet of things (UIoT) applications is a rapidly evolving research area. This study investigates UIoT connectivity between mobile marine platforms, focusing on high-definition data retrieval from the ocean. We propose a virtual tethered autonomous underwater vehicle (VTAUV) system, which integrates the advantages of both tethered and untethered architectures to enhance real-time underwater communication. The core of our approach is an acousto-optic tethering method, which enables stable, high-speed optical links between mobile platforms. By leveraging acoustic ranging and a reinforcement learning-based tracking controller, the VTAUV effectively follows an autonomous surface vehicle (ASV). A multi-beam sonar system and a real-time processing algorithm accurately estimate pointing errors, ensuring robust optical link establishment for continuous data transmission. We validate our method through sea trials, demonstrating that the VTAUV can successfully maintain acousto-optic tethering while significantly reducing pointing errors with a moving ASV. These findings mark an important step toward reliable, high-bandwidth underwater communications, paving the way for future scalable UIoT deployments.