UWGS: Geometry-Based Enhanced Time Synchronization in Underwater Acoustic Mobile Networks

In underwater networks, precise time synchronization is critical for several functions, including localization and channel access. However, achieving synchronization is challenging due to the significant propagation delays and the mobility of the nodes in underwater environments. Although methods like D-Sync [1], Mobi-Sync [2], and MU-Sync [3] address these issues in dynamic underwater settings, they typically rely on the estimation of the radial speed of the Doppler effect. Furthermore, two-way message exchanges in these protocols result in more signaling overhead or response time. Building on recent advancements in one-way ranging techniques [4], this paper introduces a novel synchronization approach for mobile networks. Our method, Underwater Geometry-Based Synchronization (UWGS), uses a geometric approach to optimally estimate the clock skew and clock offset of unsynchronized nodes, and find the synchronization error. Instead of estimating the radial speed through Doppler factors, our approach leverages multiple one-way pulse signals to construct the geometric relationship between the velocity of the node and the range. We simulated UWGS and D-Sync to evaluate performance, showing UWGS significantly improves synchronization accuracy and efficiency.