# A Comprehensive Signal Quality Assessment for BDS/Galileo/GPS Satellites and Signals
###### Abstract  
With the modernization of global navigation satellite systems (GNSS), especially the rapid development of the BeiDou Navigation Satellite System (BDS), more observations of satellites and signals have become available. Using data of the globally distributed MGEX stations, a systematic and comprehensive evaluation of signal characteristics for BDS-3, BDS-2, GPS, and Galileo is conducted in terms of carrier-to-noise ratio (C/N0), code noise, and multipath in the contribution. First, a comprehensive signal quality assessment method for BDS/Galileo/GPS satellites and signals is proposed, including _C/N0_ modeling and MP modeling. For BDS, the BDS-3 satellites apparently have higher signal power than the BDS-2 satellites at the same frequency such as B1I and B3I, and the signal B2a of BDS-3 is superior to other signals in regard to signal power, which is comparable with the superior Galileo E5 signals and GPS L5. Among all the signals, the observation accuracy of E5 is the highest regardless of receiver types, and next highest are BDS-3 B2a and GPS L5. Due to not being affected by the systematic code errors of BDS-2, the observations of BDS-3 satellites contain smaller multipath errors than that of BDS-2 satellites. As for the multipath suppression performance, the BDS-3 signal B2a, GPS L5, and Galileo E5 and E5b perform better than the other signals, which may be related to their wide signal bandwidths. BDS-3; signal quality assessment 10.399.00.0000-0000-0000-0000-0000-0000-00000-00000-00000-00000-00000-00000-000000-00000-00000-00000-0000000-00000-000000-000000-0000000-0000000-00000000-00000000000000000000000000000000000000000000000000000000000 of [PERSON] et al. on the four IOV and nine FOC satellites showed that the E5 signal modulated with AltBOC has significantly better signal power and lower noise and multi-path biases among the five Galileo signals. The instantaneous ambiguity fixation on the E5 signal can be achieved by correcting the multipath [19]. Similarly, the research by [PERSON] et al. and [PERSON] et al. indicated that apart from outperforming others in signal powers, the E5 signal has a high level of short delay multipath suppression, which may be related to its advanced signal modulation method [22; 23]. As for BDS, the characteristics of the signals B1C, B2a, and B2b were first analyzed by [PERSON] et al., utilizing the five BDS-3 satellites, and it was found that the elevation-dependent pseudorange biases that appeared in the BDS-2 satellite observations no longer exist in the new-generation BDS-3 satellites [24]. The availability of more BDS-3 satellite observation data has made the evaluation of BDS-3 performance a research hotspot. [PERSON] et al. studied the receiver pseudorange deviation between BDS-2 and BDS-3 and found that the receiver pseudorange deviation between BDS-3 and BDS-2 varies greatly and is related to the receiver type [25]. By investigating the intrinsic characteristics of receiver-related biases in the combination of BDS-3 and BDS-2, [PERSON] et al. concluded that there exist noticeable differences in the epoch-wise DCB estimates of the same type between BDS-3 and BDS-2 [26]. As for the atomic clock, the drift rate and frequency stability of the clock on the BDS-3 satellite are significantly better than those on BDS-2 [27; 28]. Furthermore, when studying the combination positioning of BDS-3 and other systems, the increase in BDS-3 new signals can significantly improve the positioning performance of BDS/GPS/Galileo [29; 30]. However, it was found that the inter-system bias (ISB) between BDS-3 and other GNSS systems cannot be ignored. Even ISB exists between BDS-3 and BDS-2 [31; 32]. The excellent characteristics of BDS-3 interest us in further evaluating its performance compared to other GNSS systems. In addition, with the completion of BDS-3, the multi-system fusion positioning service with BDS as the core has preliminary conditions.