Zhu Lin, Zhang Huijun, Li Xiaohui, Zhu Feng, Liu Yinhua
National Time Service Center, Chinese Academy of Sciences, East Shu Yuan Road, Xi'an 710600, China.
Key Laboratory of Precision Navigation and Timing Technology, Chinese Academy of Sciences, Xi'an 710600, China.
Sensors (Basel). 2022 Mar 24;22(7):2486. doi: 10.3390/s22072486.
Global Navigation Satellite System (GNSS) timing is a main service function. Each GNSS has its own time performance specification. However, a uniform timing performance assessment methodology and its outcomes do not exist. Firstly, the timing performance specifications of each GNSS are analyzed. Then, time transfer accuracy is considered as the key GNSS timing performance indicator. Secondly, an assessment method for the Coordinated Universal Time (UTC) published by the Bureau International des Poids et Mesures (BIPM) and UTC kept by the National Time Service Center of China (UTC(NTSC)) is proposed. Thirdly, the uncertainty budget of the assessment method is given. The timing performances of BDS, GPS, GLONASS, and Galileo are assessed and compared. The results show that the time transfer accuracy of BDS, GPS, GLONASS, and Galileo was 13.8 ns, 4.5 ns, 16.8 ns, and 4.2 ns, respectively, in 2021, meeting their performance requirements specified by GNSS (30 ns or 40 ns). Meanwhile, the assessment results of GPS and Galileo are much better than requirements, while the assessment results of BDS and GLONASS show fixed time offset and can still be improved further. If the local reference time of GNSS users can be connected with UTC, this assessment method can be used.
全球导航卫星系统（GNSS）授时是一项主要的服务功能。每个GNSS都有其自身的时间性能规范。然而，目前不存在统一的定时性能评估方法及其结果。首先，分析了每个GNSS的定时性能规范。然后，将时间传递精度视为关键的GNSS定时性能指标。其次，提出了一种针对国际计量局（BIPM）发布的协调世界时（UTC）以及中国国家授时中心（UTC(NTSC)）所保存的UTC的评估方法。第三，给出了该评估方法的不确定度预算。对北斗卫星导航系统（BDS）、全球定位系统（GPS）、格洛纳斯（GLONASS）和伽利略（Galileo）的定时性能进行了评估和比较。结果表明，2021年BDS、GPS、GLONASS和Galileo的时间传递精度分别为13.8纳秒、4.5纳秒、16.8纳秒和4.2纳秒，满足GNSS规定的性能要求（30纳秒或40纳秒）。同时，GPS和Galileo的评估结果远优于要求，而BDS和GLONASS的评估结果显示存在固定时间偏差，仍有进一步提升的空间。如果GNSS用户的本地参考时间能够与UTC相连，那么该评估方法即可使用。
