## 6 Results and Discussion
The results of the time transfer as determined by the multi-GNSS CP technique using the raw and RVCE schemes for all four time links are shown in Figure 4. The RVCE solutions are shown in red and the raw solutions are shown in black. To ensure the clarity of our purpose, the solutions from the RVCE scheme have been translated (10 ns for ONS1-BRUX, 20 ns for NTS1-KAT1, 20 ns for NTS1-CEDU, and \(-\)2 ns for BRUX-NTS1). Figure 4: Results of time transfers determined by a carrier-phase (CP) technique with and without the RVCE approach for the four time links. (**a**) is for ONS1-BRUX, (**b**) is for NTS1-KAT1, (**c**) is for NTS1-CEDU and (**d**) is for BRUX-NTS1. Figure 3: Receiver clock time series for station ONS1 and CEDU with and without the RVCE approach. In the time link of ONS1-BRUX, it can be found that the RVCE scheme has effectively resisted some outliers. Due to the external time and frequency references at the stations, CEDU and KTA1 have not been controlled, while the trend terms are obvious, the performances are difficult to compare. Therefore, the residuals and the root mean square (RMS) value were compared, and the smoothed result is always used because it maintains both low signal noise and the variable trend of the time transfer results. The Kalman smoothing approach was employed in our experiment. Figure 5 shows the residuals of the two different schemes for the four time links, the black line is the traditional solution and the red line is RVCE solution. It can be clearly seen that the RVCE can resist more outliers when compared to the traditional approach. Table 4 presents the corresponding RMS for the time links. The performance of the RVCE solution is slightly improved relative to the raw solution, which ranges from 0.75% to 5.48%, with a mean of 3.41%. In the domains of time and frequency, the frequency stability is an important index for time links, particularly for short term when using the GNSS technique [42]. Here, the Allan deviation (ADEV) of the time transfer solutions for two different scenarios is obtained for the four time links (Figure 6) and the corresponding ADEV values are given in Table 5. It is clear that the stability of the RVCE solution is greater than that of the raw solution at different average time (AT) \(\tau\), particularly when AT are within 10,000 s. Because the number of available data points used for computing ADEV dramatically decreases when \(\tau\) is greater than 10,000 s, the corresponding measurement errors gradually increase. The error bars at different \(\tau\) in the Figure 6 also can be agreed with this principle. Therefore, the results \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Time Link Name** & **Raw (ns)** & **RVCE (ns)** & **Improvement (\%)** \\ \hline ONS1-BRUX & 0.420 & 0.397 & 5.48 \\ NTS1-KAT1 & 0.133 & 0.132 & 0.75 \\ NTS1-CEDU & 0.141 & 0.138 & 2.13 \\ BRUX-NTS1 & 0.019 & 0.018 & 5.26 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Improvement (%) in RMS of the result smoothing in two scenarios for the time links. Figure 5: Smoothing residuals of the results with and without the RVCE approach for the four time links. (**a**) is for ONS1-BRUX, (**b**) is for NTS1-KAT1, (**c**) is for NTS1-CEDU and (**d**) is for BRUX-NTS1. that the \(\tau\) is less than 10,000 s are pay more attention and corresponding improvement for these four time links are summarized in Figure 7. It can be noted that the improvement range relative to the raw solutions differ among the four links. The mean improvement to the ONS1-BRUX link is 13.48%, while improvements are 5.97% for the NTS1-KAT1 link, 32.34% for the NTS1-CEDU link and 7.76% for the BRUX-NTS1 link. The mean value for all four time links is 14.89%.