## 1 Introduction  
With the implementation of the three-stage development plan of the BeiDou Navigation Satellite System (BDS), China started to provide local and global service at the end year of 2012 and 2018, respectively. Three types of constellations were employed by BDS, including GeoSynchronous Orbit (GEO), Inclined GeoSynchronous Orbit (IGSO) and Medium Earth Orbit (MEO). Three frequencies of signals were propagated by the second generation of BDS Satellites (BD2), which were named as B1I, B2I and B3I. Later, according to the publication of Interface Control Document (ICD) [1; 2; 3; 4] for the third generation of BDS satellites (BD3), four frequencies navigation signals were broadcasted, including the legacy signals B1I (1561.098 MHz) and B3I (1268.52 MHz) for a transition from BD2 to BD3, and two new frequencies, BIC (1575.42 MHz) and B2a (1176.45 MHz). In fact, the two new-added open signals' frequencies are equal to GPS L1/L5, Galileo E1/E5a or QZSS L1/L5. In general, multi-systemcompatibility and interoperability can be achieved by making full use of the overlap signal frequencies of GPS, Galileo, BDS and QZSS. Besides, the BD2 satellite bus is equipped with four rubidium atomic clocks, in which two are from the Spectra Time company and the others are manufactured in China, but the improved rubidium atomic frequency standard (RAFS) and the Passive Hydrogen Maser (PHM) made in China are equipped in the BD3 satellites. In order to serve the global positioning, navigation and timing users, five BD3 experimental satellites (BD3-e) have been deployed for testing the various key technologies. Then, eighteen BD3 MEOs and one GEO were launched from 5 November 2017 to 18 November 2018. It should be noted that the new generation BDS satellites bus were manufactured by the China Academy of Space Technology (CAST) and Shanghai Engineering Center for Microsatellites (SECM). New navigation signal constitution and inter-satellites links measurements are employed in the BD3 GEO and MEO satellites, which is helpful for weak signal tracking, autonomous orbit determination and expanding the short message service to global coverage. A lot of the current research has focused on the navigation signals since the proclamation of the BD2 local service. At the time, BD2 was the first navigation system in which all satellites provided signals of three frequencies, and many scholars were interested in the signal performance [5; 6], multi-frequency Precise Positioning [7; 8], precise orbit determination (POD) [9; 10; 11; 12]. In addition, the satellite-induced pseudorange bias of BDS IGSOs and MEOs has been confirmed by [PERSON] [13] and [PERSON] [14]. Then, the pseudorange bias in BD2 GEOs has also been inferred by analyzing the single-difference (SD) ambiguity characters between satellites, which was almost the same performance as the IGSOs [15]. [PERSON] and beer proposed an elevation-dependent model to improve the IGSOs and MEOs pseudorange [16]. [PERSON] analyzed the BD2 GEOs pseudorange bias using onboard observation data of low earth orbit satellite FY3-C and developed a revised method [17]. [PERSON] analyzed the pseudorange code bias of BD3-e using a short baseline with two receivers, and their results showed that the satellites-induced pseudorange had been eliminated [5]. [PERSON] assessed the civil signals transmitted by BD3-e using a multipath-free 40 m dish antenna, and their results showed that the pseudorange bias of B1C and B2a varied by about 0.1 m, which was compatible to GPS L2 and L5 [18]. The PHM equipped on BD3-e satellites was also assessed and the clock bias was estimated through the two-way satellite time and frequency transfer method in [PERSON] et al. [19]. Although there is much research on BD3-e, it should be noted that the signal constitution of BD3-e satellites is not strictly the same as that of the BD3 Full Operational Capability (FOC) satellites. Besides, BD3-e has been served as a complement of BD2 not BD3. At present, there are almost no studies about the effective analysis of the BD3 FOC satellites.