# Characterization of GNSS Signals Tracked by the iGMAS Network Considering Recent BDS-3 Satellites
## 3 Methodology and Results  
### Carrier-To-Noise Density Ratio  
The carrier-to-noise density ratio (\(\rm C/N_{0}\)) and its variation with elevation provides a key figure of merit for the characterization of the wide variety of signals accessible with modern receivers. The observed \(\rm C/N_{0}\) values of GPS, Galileo (GAL), and BDS-2 and BDS-3 signals at CHU1, CANB, and ICUK stations are depicted as a function of satellite elevation in Figure 2. These three stations are equipped with different receivers (Table 3). The CHU1 station can track BDS-3 B1I/B1C/B2a/B2b/B3I signals, while the CANB and ICUK stations are unable to track BDS-3 B2b signals. The GPS is restricted to Block IIF satellites that can simultaneously transmit L1/L2/L5 signals; the BDS-2 is confined to only MEO satellites (C11, C12, and C14) for comparison; and the BDS-3 involves the eight satellites listed in Table 1 and examined in this study. The tracking data for a period of ten days from DOY 148 to DOY 157 (2018) provide the basis for the analysis. For each station, we first group all \(\rm C/N_{0}\) values according to their corresponding elevations separately for each signal of the selected GPS, Galileo,  
Figure 1: Distribution of selected stations in the iGMAS network. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Abb.** & **Location** & **Receiver** & **Antenna** &
\begin{tabular}{l} **Tracked BDS-3** \\ **Signals** \\ \end{tabular} \\ \hline ABJA & Abuja & GNSS\_GGR & RINT-8 CH CETD & B1I, B3I, B1C, B2a, B2b \\ CHU1 & Changchun & GNSS\_GGR & RINT-8 CH CETD & B1I, B3I, B1C, B2a, B2b \\ GUA1 & Urumqi & GNSS\_GGR & RINT-8 CH CETD & B1I, B3I, B1C, B2a, B2b \\ HMNS & Hermanus & GNSS\_GGR & RINT-8 CH CETD & B1I, B3I, B1C, B2a, B2b \\ THAT & Tahiti & GNSS\_GGR & RINT-8 CH CETD & B1I, B3I, B1C, B2a, B2b \\ XIA1 & Xi’an & GNSS\_GGR & RINT-8 CH CETD & B1I, B3I, B1C, B2a, B2b \\ CANB & Canberra & CETC-54-GMR-4011 & GNSS-750 & B1I, B3I, B1C, B2a \\ DWIN & Darwin & CETC-54-GMR-4011 & GNSS-750 & B1I, B3I, B1C, B2a \\ PETH & Perth & CETC-54-GMR-4011 & GNSS-750 & B1I, B3I, B1C, B2a \\ ZHON & Antarctica & CETC-54-GMR-4011 & GNSS-750 & B1I, B3I, B1C, B2a \\ BIFI & Beijing & CETC-54-GMR-4016 & LEIA2R5.R4 LEIT & B1I, B3I, B1C, B2a \\ CLGY & Calgary & CETC-54-GMR-4016 & LEIA2R5.R4 LEIT & B1I, B3I, B1C, B2a \\ WUH1 & Wuhan & CETC-54-GMR-4016 & LEIA25.R4 LEIT & B1I, B3I, B1C, B2a \\ BRCH & Braunschweig & CETC-54-GMR-4016 & NOV750.R4 NOVS & B1I, B3I, B1C, B2a \\ LHA1 & Lhasa & CETC-54-GMR-4016 & NOV750.R4 NOVS & B1I, B3I, B1C, B2a \\ ICUK & London & CETC-54-GMR-4016 & NOV750.R4 NOVS & B1I, B3I, B1C, B2a \\ KNDY & Kandy & CETC-54-GMR-4016 & GNSS-750 & B1I, B3I, B1C, B2a \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Configuration of selected iGMAS stations. BDS-2, and BDS-3 satellites. Then, the C/N\({}_{0}\) values within an elevation range of 5\({}^{\circ}\) are classified into one group. Finally, a mean value of C/N\({}_{0}\) is computed and shown for each elevation group. For GPS and Galileo in the top panels of Figure 2, it can be clearly seen that the GPS L5 signals exhibit the highest C/N\({}_{0}\) values over the entire elevation range for each of the three stations. The CHU1 station shows distinctly different signal characteristics than the other two stations. On the whole, the Galileo E1 signal has the lowest power level at CHU1, while the GPS L2 signals have the lowest power levels at the CANB and ICUK stations. At the CANB and ICUK stations, the C/N\({}_{0}\) values for all GPS and Galileo signals start at 34-40 dB-Hz at low elevation angles and reach 48-54 dB-Hz at zenith, while at the CHU1 station, the C/N\({}_{0}\) values start at 32-38 dB-Hz at low elevation angles and reach 50-57 dB-Hz at zenith, and increase more quickly as elevation angle increases. For BDS-2 and BDS-3 in the bottom panels of Figure 2, it is clear that BDS-3 BIC signals exhibit the lowest C/N\({}_{0}\) values for the three stations, especially CHU1 and ICUK, which is consistent with the results of BDS-3e satellite analysis in [PERSON] et al.