## 1 Introduction
The positioning results from the studied IGS ACs were centimeter level in horizontal and vertical components, respectively. The kinematic RT-PPP field test indicates that the positioning accuracies estimated by CNES' real-time products were better than those based on CAS precise products. [PERSON] et al. [19] studied the performance of BDS-2 real-time products from four IGS centers, WHU, CNES, DLR, and GFZ. The availabilities of all these real-time products were more than 85%, and the real-time orbit accuracies of the GEO and IGSO/MEO satellites were meter level and decimeter level, respectively. Among all of these products, CNES provided the highest accuracy on 3D orbit and clock products. In static PPP mode, the convergence time on average was less than 1.5 h with 11.0 cm positioning accuracy, while in the kinematic mode, the convergence time was 2.11 h-9.84 h with 30.7 cm-68.0 cm positioning accuracy. [PERSON] et al. [20] evaluated the accuracy availability of the BDS-3 real-time products from CENS using continuous data of 41 days. The results \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**IGS Center** & **Orbit** & **Clock** & **Code Bias** & **Phase Bias** & **VTEC** & **GNSS** \\ \hline BKG & 60 s & 5 s & 60 s & 60 s & - & G/R/E \\ CAS & 5 s & 5 s & 10 s & - & 60 s & G/R/E/C \\ CNES & 5 s & 5 s & 5 s & 5 s & 60 s & G/R/E/C \\ DLR & 30 s & 5 s & 30 s & 30 s & - & G/R/E/C/J [1] & \\ GFZ & 5 s & 5 s & 5 s & - & - & G/R/E/C \\ WHU & 5 s & 5 s & - & - & - & G/R/E/C \\ \hline \hline \end{tabular}  
* \({}^{\dagger}\)G, R, E, C, and J denote GNSS, GOLANSS, Galileo, BDS, and Quasi-Zenith Satellite System (QZSS), respectively.  
\end{table} 
Table 1: The IGS SSR message information and the corresponding interval. showed that satellite orbit accuracies were about 6 cm in radial and cross-track components but more than 10 cm in the along-track component, and the accuracy of the clock was 0.46 ns. The BDS-3 real-time product availability from CENS is over 80%. The PPP positioning errors in static were within 3 cm at East (E), North (N), and Up (U) components, which was comparable to that of GPS RT-PPP. Different from the internet-based RT-PPP service provided by the IGS, BDS-3 broadcasts the correction of satellite orbit and clock for both BDS-3 and GPS via the PPP-B2b signal. Simultaneously, the BDS-3 Differential Code Bias (DCB) is broadcast to facilitate dual-frequency PPP positioning applications [3]. Table 2 lists the broadcast PPP-B2b correction messages [21; 22; 23]. The performance evaluations of PPP-B2b products have gained interest from researchers recently. [PERSON] et al. [3] presented the positioning accuracy evaluation of dual-frequency B1C/B2a PPP with Ionosphere-Free (IF) combination based on the PPP-B2b data from 1 August to 30 November 2020. The results indicated that about 30 cm and 50 cm positioning accuracies in the horizontal and vertical components could be achieved with a 30 min convergence time. [PERSON] et al. [21] analyzed the accuracy, integrity, and stability of the orbit clock and DCB corrections of both BDS and GPS provided by the BDS-3 PPP-B2b signal, which proved that the PPP-B2b signal could provide stable and accurate PPP services in China and surrounding areas. [PERSON] et al. [22] compared the orbits and clocks accuracies between PPP-B2b corrections and GFZ final products with three days of observation. The BDS-3 satellite orbit accuracies in radial, along-track, and cross-track components are about ten centimeters, and the BDS-3 clock accuracy was centimeter-level. The static PPP with PPP-B2b correction messages achieved centimeter-level accuracy in the E, N, and U components, and the kinematic PPP of those also achieved centimeter-level accuracy. [PERSON] et al. [23] illustrated that the real-time BDS-3 PPP-B2b correction messages presented better availability and integrity than CNES on BDS satellites. The positioning accuracy of PPP-B2b products-based BDS-3 kinematic PPP can achieve centimeter-level. [PERSON] et al.