High-precision Time Synchronization Algorithm for Unmanned Aerial Vehicle Ad Hoc Networks based on Bidirectional Pseudo-range Measurements
K. Z. Bai, Jianfeng Wu, Huabing Wu
Abstract
The increasing demand for missions involving unmanned aerial vehicles (UAVs) raises the need for reliable and accurate time synchronization in ad hoc networks. Time synchronization plays a crucial role in coordinating the actions of multiple UAVs, particularly when it comes to positioning, coordination, and data fusion. However, achieving high-precision time synchronization is challenging due to the difficult-to-estimate communication transmission delay, measurement noise, relative motion, and clock source characteristics in wireless ad hoc networks formed by UAVs. To address this issue, this paper proposes a fully distributed high-precision network time synchronization algorithm that is suitable for multi-hop dynamic ad hoc networks. The proposed algorithm is based on bidirectional pseudo-range measurements, graph theory, and random matrix correlation theory. It is composed of relative clock skew estimation, logic clock skew compensation and logic clock offset compensation. The algorithm is rigorously derived, requiring no central node, and it is capable of obtaining relative clock skew even when nodes broadcast clock information asynchronously. In addition, the proposed algorithm enables real-time elimination of transmission delays and has noise-resistant capabilities. Simulation results validate the effectiveness of the algorithm, demonstrating that the time synchronization accuracy in UAV ad hoc networks can reach the sub-nanosecond level.