An Algorithm for Inter-Satellite Autonomous Time Synchronization and Ranging in the Beidou Navigation Satellite System

Aiming at the requirement of the autonomous time synchronization in BeiDou Navigation Satellite System (BDS), an algorithm for inter-satellite autonomous time synchronization and ranging is proposed. Based on the establishment of the inter-satellite link length model of the BDS, a series of simulation has been carried out through the use of STK (Satellite Tool Kit), which includes the simulation of the length changing rules, the length variation scale and its variation ratio. Based on these simulations, an analysis of the impact of satellite motion on the inter-satellite two-way time synchronization and range has been presented. In this algorithm, the inter-satellite clock-offset and range with minimal error are acquired by utilizing the combination of clock-offset fitting polynomial and range fitting polynomial based on the least square fitting of data generated from the inter-satellite two-way time synchronization. Empirical evaluation of the BDS simulation shows that our time synchronization error is 2ns, and ranging error is 2m under the condition of acceptable simulation error. With the application of the algorithm to the inter-satellite autonomous time synchronization and ranging, the high-accuracy measurement of inter-satellite clock-offset and range of BDS can be reached.