# Real-Time Precise Point Positioning during Outages of the PPP-B2b Service
## 3 Experiments and Results
### Positioning Quality Degradation over Time
#### 3.3.2 Accuracy of the Real-Time PPP-B2b Positioning Using Extended Corrections  
To investigate the real-time positioning performance of using extended corrections during PPP-B2b signal interruptions, the PPP-B2b signal was artificially interrupted at GPST 16:30 on DOY 297 in 2022. In this simulation experiment, the interruption time length was increased from 10 min to 60 min with a step of 10 min. As shown in Figure 13, the positioning accuracy during an interruption of 10 min remained comparable to that without the interruption. For an interruption of 20 min, the 3D positioning error reached 20 cm, and quickly decreased to 12 cm when reacquiring the PPP-B2b signal. As the interruption time increased from 10 min to 60 min, the 3D positioning error gradually increased from 12 cm to 57 cm. The increase in positioning error was especially obvious in the up direction, with the maximum RMSE of approximately 0.5 m after 53 min, which greatly affected the three-dimensional positioning accuracy. Although the 3D positioning error increased significantly as the interruption continued, it quickly returned to a satisfactory level (20 cm) after reacquiring the PPP-B2b corrections. In general, the shorter the interruption time is, the better the positioning accuracy will remain during the interruption period. This interruption experiment was also conducted at the other four stations. As shown in Figure 14, a longer interruption will generally lead to a larger positioning error when the extended corrections during the interruption of the PPP-B2b signal are used. In most cases, the position accuracy obtained with extended corrections during the first 10 min of the interruption period will be similar to that derived with received PPP-B2b corrections. With an increase in the interruption period, the positioning error w  
Figure 13: Effects of different interruption lengths on the simulated kinematic PPP-B2b positioning results for the BJ01 station in the north, east, up, and 3D directions on DOY 279 in 2022.  
will increase steadily and become much larger than that determined with received PPP-B2b corrections. The results also indicate that the positioning errors show very obvious dependence on location. To give a more general statistical result regarding the PPP performance with different interruption periods, we artificially interrupted the PPP-B2b signal at GPST 6:30, 11:30, 16:30, and 21:30 during DOY 355-361 in 2022, and counted the mean RMSE of the 3D positioning error during the interrupptions. As Table 6 shows, for stations located in China, i.e., BJ01, JFNG, and HKSC, during interruption of the PPP-B2b signal, the RMSE of the  
Figure 14: Accuracy of the remaining four stations in the north, east, and up directions, and 3D coordinates after the interruption at 16:30:00 and without the interruption. positioning results increased slowly from below 15 cm in the first 10 min to larger than 30 cm during the 50-60 min of interruption. For the two stations located in Xinjiang, China (KSKT) and Japan (MSSA), the RMSE of the positioning results increased from approximately 30 cm in the first 10 min of the interruption period to 60 cm during 50-60 min of interruption. In general, during the first 10 min of the interruption period, the accuracy of the positioning results obtained with extended corrections was almost identical to that obtained with true PPP-B2b corrections. In addition to the above simulated kinematic experiments, a real-time kinematic experiment was conducted to further investigate the PPP performance with extended PPP-B2b corrections during outages of the PPP-B2b service. This experiment was conducted on DOY 361, 2022 with a GNSS receiver mounted on a slow-moving platform. As shown in Figure 15, the receiver started operation at GPST 6:15, and the 3D positioning accuracy took 65 min to converge to 8 cm. During the movement of the platform, we artificially interrupted the tracking of the GEO satellites at 7:30 and restored the tracking at 7:40.