GNSS多系统RTK授时性能分析

RTK授时不依赖实时精密星历，精度高、实现简单，在短距离精密授时与时间同步中具有突出的应用潜力。针对城域环境下单系统RTK授时可能面临可用卫星数量较少、收敛时间较长等问题，验证分析了GNSS多系统RTK授时性能。基于中国科学院国家授时中心时间频率资源和3个GNSS跟踪站的BDS-3、GPS和Galileo观测数据开展多系统RTK授时试验，涉及动态、静态和固定站坐标3种模式，并从授时精度、收敛时间和稳定度3个方面展开分析。两条基线的试验结果表明：与光纤双向时间频率传递结果相比，动态模式下，多系统单频授时差异STD较GPS单系统分别提高9.13%和9.01%，静态模式分别提高6.09%和11.76%，固定站坐标模式分别提高3.04%和5.79%，多系统单频RTK授时的授时结果差异STD优于0.25 ns，双频优于0.15 ns；多系统融合使得RTK授时的收敛时间与GPS单系统相比至少缩短25%以上，静态模式下双频RTK收敛时间缩短最多，两条基线分别缩短66.9%和67.8%；3种模式多系统站间钟差的万秒稳均进入10-15量级，动态模式和静态模式下短期稳定度相比GPS单系统有明显改善，但随着平均时间的增长，这种改善也在逐渐减弱。试验结果可为城域环境下GNSS多系统RTK授时的应用推广提供一定的参考。

Performance analysis of multi-GNSS real-time kinematic timing

Real-time kinematic(RTK) timing,which does not depend on real-time precise ephemeris,has high accuracy,simple implementation,and outstanding application potential in short-distance precisetiming and time synchronization. The performance of multi-GNSS RTK is validated and analyzed for the problems of long convergence time and small number of available satellites that single system RTK timing may confront with in metropolitan environment. Based on the time and frequency resources of the National Time Service Center of Chinese Academy of Sciences and the observation data of BDS-3,GPS and Galileo from three GNSS tracking stations,the multi-system RTK time service experiment is carried out,involving dynamic,static and fixed station coordinate modes,and analyzed from aspects of timing accuracy,convergence time and stability. The results of the two baseline tests show that, compared with the result of optical fibre two-way time-frequency transfer,the accuracy of multi-GNSS single-frequency timing is 9.13% and 9.01% in kinematic mode, higher than that of GPS-only system,6.09% and 11.76% higher in static mode,3.04% and 5.79% higher in fixed-station coordinate mode.For multi-GNSS system, the difference STD of single-frequency RTK timing is better than 0.25 ns,and that of dual-frequency timing is better than 0.15ns.The convergence time of multi-GNSS RTK timing is at least 25% shorter than that of GPS-only system. The convergence time of dual-frequency RTK in static mode for the two baselines are shortened by 66.9% and 67.8%,respectively.The 10 000 s stability of the clock difference between multi-system stations in 3 modes all enters E-15 magnitude. Short-term frequency stability in kinematic mode and static mode is significantly improved compared with GPS-only system,but this improvement is gradually weakening with the increase of average time. The test results can provide reference for the application of GNSS multi-system RTK time service in urban environment.