# A Comprehensive Signal Quality Assessment for BDS/Galileo/GPS Satellites and Signals
## 5 Conclusions  
A comprehensive evaluation of the signal characteristics of BDS, Galileo, and GPS was conducted using data from four types of receivers of MGEX stations. The following conclusion can be drawn.  
In terms of signal power, the BDS-3 satellites have better manifestation than the BDS-2 satellites, and the signal B2a is better than B1I and B3I, while E5 of Galileo and L5 of GPS perform better than the other signals of the respective systems. The pseudorange noise exhibits characteristics of periodicity and variation with satellite elevation. The BDS-3 B2a signal possesses smaller noise than the other signals of BDS. The signal L5 performs better than the other signals of GPS, while the Galileo E5 signal performs best among all the signals of the three systems, regardless of receiver types. The MP error of BDS-3 is on the same level as that of GPS and Galileo, which is apparently smaller than that of BDS-2, and the systematic biases which exist in the pseudorange observations of BDS-2 are absent for BDS-3. Similar to the characteristics of the CC values, the BDS-3 B2a, GPS L5, and Galileo E5b have significantly smaller multipath errors than other signals. In general, the C/N0, CC, and multipath values have little relationship with the receiver type, but they affect each other.  
In this paper, although some preliminary conclusions and research results have been achieved, there are still the following studies that need to be further deepened and expanded, due to system development and personal conditions, etc. The paper mainly focuses on the data quality between different types of satellites and different frequency observations of BDS/Galileo/GPS, but it does not conduct a detailed study of the observation stochastic model based on this. With the availability of BDS-3 and more Galileo FOC satellite observations, the establishment of a stochastic model that reflects the differences in the stochastic characteristics of different observations based on the data quality analysis to achieve high-precision-combined multi-GNSS navigation and positioning will become the key of the next research.  
Conceptualization, Y.T. and G.X.; methodology, Y.T. and R.G.; software, Y.T. and D.Z.; validation, L.Z. and J.G.; formal analysis, J.X.; investigation, Y.H.; resources, X.D.; writing--original draft preparation, Y.T.; writing--review and editing, D.H. and Z.Q.; visualization, J.X. and L.Z.; supervision, D.Z.; project administration, G.X.; funding acquisition, R.G. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by the National Natural Science Foundation of China (grant nos. 42274045, 42004028 and 41904039), Natural Science Foundation of Henan (grant no. 232300421105) and China Postdoctoral Science Foundation (grant no. 2023M733285).  
**Data Availability Statement:** The raw data supporting the conclusions of this article will be made available by the authors on request. The data can be found at the IGS official website ([[http://www.igs.org/mgex/data-products/#data](http://www.igs.org/mgex/data-products/#data)]([http://www.igs.org/mgex/data-products/#data](http://www.igs.org/mgex/data-products/#data)), accessed on 2 April 2024).  
**Acknowledgments:** The authors express great gratitude to IGS and iGMAS for providing the GNSS data.  
**Conflicts of Interest:** The authors declare no conflict of interest.