Unified Underwater Communication Positioning Navigation and Timing Network System Design and Application

The dynamic and heterogeneous nature of marine environments, combined with severely constrained communication and energy resources, presents distinct challenges in constructing underwater Communication, Positioning, Navigation, and Timing (CPNT) systems compared to terrestrial Positioning, Navigation, and Timing (PNT) architecture. To address the inherent limitations of conventional decoupled CPNT systems – including high costs and low efficiency in communication and energy utilization – this study aims to propose a unified underwater CPNT ($U^{2}CPNT$) system that coordinates multi-modal data and resource allocation, thereby optimizing CPNT service performance in harsh underwater conditions. In this study, Cramér-Rao Lower Bound (CRLB) formalization is applied to theoretically analyze the feasibility of $U^{2}CPNT$ system, and the design of $U^{2}CPNT$ system is presented to realize the integrated design of CPNT. To validate the system performance, a real $U^{2}CPNT$ system was built and sea trials were conducted. With $U^{2}CPNT$ architecture, the integrated CPNT service can be provided, the positioning error is lower, the positioning continuity has improved by 7.68%, the velocity estimation error is less than 1 m/s, making $U^{2}CPNT$ a potential solution for underwater CPNT service.