National Time Service Center, Chinese Academy of Sciences, Shu Yuan Road, Xi'an 710600, China.
Key Laboratory of Time and Frequency Primary Standards, Chinese Academy of Sciences, Xi'an 710600, China.
Sensors (Basel). 2018 Aug 31;18(9):2878. doi: 10.3390/s18092878.
The combination of multiple Global Navigation Satellite Systems (GNSSs) may improve the performance of time and frequency transfers by increasing the number of available satellites and improving the time dilution of precision. However, the receiver clock estimation is easily affected by the inappropriate weight of multi-GNSSs due to the different characteristics of individual GNSS signals as well as the outliers from observations. Thus, we utilised a robust Helmert variance component estimation (RVCE) approach to determine the appropriate weights of different GNSS observations, and to control for the influence of outliers in these observation in multi-GNSS time and frequency transfer. In order to validate the effectiveness of this approach, four time links were employed. Compared to traditional solutions, the mean improvement of smoothed residuals is 3.43% using the RVCE approach. With respect to the frequency stability of the time links, the RVCE solution outperforms the traditional solution, particularly in the short-term, and the mean improvement is markedly high at 14.89%.
多全球导航卫星系统（GNSS）的组合可以通过增加可用卫星的数量和提高时间精度稀释度来提高时间和频率传递的性能。然而，由于单个 GNSS 信号的特性以及观测值中的异常值不同，接收机时钟估计很容易受到多 GNSS 不合适权重的影响。因此，我们利用稳健的赫尔默特方差分量估计（RVCE）方法来确定不同 GNSS 观测值的适当权重，并控制这些观测值中异常值对多 GNSS 时间和频率传递的影响。为了验证该方法的有效性，使用了四个时间链路。与传统方法相比，使用 RVCE 方法可使平滑残差的平均改善率提高 3.43%。就时间链路的频率稳定性而言，RVCE 解决方案优于传统解决方案，特别是在短期，平均改善率高达 14.89%。
