## 1 Introduction  
The BeiDou Navigation Satellite System (BDS) is a global satellite navigation system independently developed and operated by China. On 31 July 2020, The BDS-3 global satellite navigation system was officially announced to provide a global service [1,2]. In addition to the traditional B1I and B3I signals, BDS-3 also transmits several new signals with advanced signal structures, namely, B1C, B2a, B2b, and B2a + b. In terms of signal design, BIC signals are compatible with GPS L1C and Galileo E1 signals, while B2a signals are compatible with GPS L5C and Galileo E5a signals. The new B2b signal is used for smooth transition and compatibility with BDS-2, which can achieve better performance and is competitive with other GNSS signals [3]. Compared with BDS-2, the BDS-3 constellation is composed of three Geostationary Earth Orbit (GEO) satellites, three Inclined Geosynchronous Satellite Orbit (IGSO) satellites, and twenty-four Medium Earth Orbit (MEO) satellites, and these satellites of BDS-3 are manufactured by the China Academy of Space Technology (CAST) and Shanghai Engineering Center for Microsatellites (SECM) [4]. Precision point positioning (PPP) aims to provide positioning accuracy from decimeters to centimeters through global navigation satellite systems. Researchers from Universities and Institutes in China and abroad have carried out in-depth research into BDS-2, such as studies into the signal characteristics of the code observations [5; 6], pseudo-range variations [7; 8], precision clock estimation (PCE) [9], positioning performance [10; 11; 12], inter-satellite-type biases (ISTBs) [13; 14], precise orbits and clocks [15; 16], and so on. In recent years, numerous research projects have been conducted on the BDS-3 precise clock estimation [17; 18; 19], time group delay (TGD)/differential code bias (DCB) [20; 21], PPP-B2b signal evaluation [22; 23; 24], and satellite availability [25; 26]. Whether from the composition of the signal or the signal propagation, positioning is fundamental. Although the full operation of BDS-3 began in July 2020, the PPP performance of BDS-3 on a global scale has rarely been analyzed. [PERSON] et al. [27] evaluated the PPP performance for the combination of BDS-3 and BDS-2. The RMS values of the static BDS-2/BDS-3 PPP were 10.7 cm, 19.5 cm, and 20.4 mm, respectively, in the geographic area of the selected station, which is the same level as GPS and GLONASS. The RMS values of the kinematic BDS-2/BDS-3 PPP were 5.88 cm, 7.43 cm, and 9.50 cm, respectively. The positioning accuracy, convergence time, and zenith tropospheric delay are also used to verify the performance of PPP, but only the stations in Asia and Europe are selected, though most are located in Asia. [PERSON] et al. [28] analyzed the performance of the combination of quad-frequency PPP models of BDS and Galileo, and the results show that quad-frequency PPP generates a significant improvement when compared with single-frequency. The pseudo-range noise of the new frequency of B1C and B2a is slightly larger than that of the B1I and B3I signals. Mainly, however, researchers use data concentrated on one station for analysis. [PERSON] and [PERSON] et al. [29; 30] compared the performance of low-cost single-frequency precise point positioning (SFPPP), starting from the aspects of positioning accuracy and convergence speed, but only the single-frequency model was considered. Some scholars have studied the performance of PPP from the orbital clock products provided by IGS [31] and the combination of multi-frequency PPP and multi-system PPP [32; 33], but the analysis focused on more the combination PPP of B1I and B3I frequencies, and focused less on the analysis of B1C and B2a frequencies PPP. [PERSON] et al. [34] simply analyzed the positioning performance of B1C and B2a from static PPP, but did not conduct a comprehensive analysis of PPP.