# An In-Depth Assessment of the New BDS-3 B1C and B2a Signals
## 5 Quality of Code Observation
### Code-minus-Carrier (CC)
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & & **B1I** & **B1C** & **B2a** & **B2b** & **B2I** & **B3I** \\ \hline GEO & BDS-2 & 0.24 & & & & 0.24 & 0.17 \\  & BDS-3 & 0.2 & & & & 0.16 \\ IGSO & BDS-2 & 0.26 & & & & 0.18 & 0.09 \\  & BDS-3 & 0.23 & 0.16 & 0.10 & & 0.08 \\ MEO & BDS-2 & 0.33 & & & & 0.20 & 0.18 \\  & BDS-3 & 0.26 & 0.20 & 0.13 & & 0.14 \\ \hline \end{tabular}
\end{table} 
Table 10: CC statistics of all types of satellites (unit: meters). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**System**} & \multirow{2}{*}{**Satellite**} & \multirow{2}{*}{**Elevation** (Average)**} & \multirow{2}{*}{**B1I**} & \multirow{2}{*}{**B1C**} & \multirow{2}{*}{**B2a**} & \multirow{2}{*}{**B2I**} & \multirow{2}{*}{**B3I**} \\  & & & **(Average)** & & & & \\ \hline \multirow{6}{*}{**BDS-2**} & average & 32.41 & 0.33 & & & 0.2 & 0.18 \\  & C11 & 24.82 & 0.35 & & & 0.23 & 0.21 \\  & C12 & 25.36 & 0.36 & & & 0.21 & 0.17 \\  & C14 & 47.05 & 0.28 & & & 0.17 & 0.17 \\  & average & 39.33 & 0.26 & 0.2 & 0.13 & & 0.14 \\  & C19 & 46.03 & 0.24 & 0.18 & 0.12 & & 0.11 \\  & C20 & 35.78 & 0.30 & 0.25 & 0.19 & & 0.21 \\  & C21 & 44.54 & 0.22 & 0.18 & 0.11 & & 0.14 \\  & C22 & 43.58 & 0.23 & 0.20 & 0.11 & & 0.09 \\  & C23 & 48.82 & 0.23 & 0.18 & 0.12 & & 0.11 \\  & C24 & 40.28 & 0.25 & 0.22 & 0.11 & & 0.15 \\  & C25 & 35.58 & 0.27 & 0.21 & 0.14 & & 0.15 \\  & C26 & 54.39 & 0.21 & 0.16 & 0.09 & & 0.07 \\  & C27 & 45.17 & 0.23 & 0.19 & 0.13 & & 0.17 \\  & C28 & 44.87 & 0.23 & 0.19 & 0.11 & & 0.10 \\  & C29 & 45.47 & 0.25 & 0.20 & 0.12 & & 0.12 \\
**BDS-3** & C30 & 43.35 & 0.24 & 0.19 & 0.12 & & 0.10 \\  & C32 & 30.87 & 0.29 & 0.20 & 0.13 & & 0.14 \\  & C33 & 32.20 & 0.27 & 0.21 & 0.12 & & 0.12 \\  & C34 & 22.87 & 0.31 & 0.24 & 0.15 & & 0.16 \\  & C35 & 43.24 & 0.25 & 0.18 & 0.12 & & 0.16 \\  & C36 & 29.44 & 0.28 & 0.22 & 0.14 & & 0.15 \\  & C37 & 46.37 & 0.28 & 0.20 & 0.15 & & 0.15 \\  & C41 & 25.93 & 0.33 & 0.26 & 0.14 & & 0.15 \\  & C42 & 51.39 & 0.23 & 0.17 & 0.11 & & 0.13 \\  & C43 & 35.44 & 0.26 & 0.20 & 0.11 & & 0.17 \\  & C44 & 31.37 & 0.30 & 0.22 & 0.14 & & 0.17 \\  & C45 & 32.36 & 0.30 & 0.23 & 0.14 & & 0.14 \\  & C46 & 34.68 & 0.32 & 0.22 & 0.15 & & 0.14 \\ \hline \end{tabular}
\end{table} 
Table 9: Statistics of CC values for all MEO satellites. Figure 11: Elevation changes between BDS-3 and other GNSS-selected satellites. Figure 10: Comparison of CC values between BDS-3 and other GNSS signals at the same frequency. Figure 9: Comparison of CC values of all types of satellites of BDS-2 and BDS-3. The CC statistics of different GNSS satellites are shown in Table 11. For different GNSS satellites, the average CC of the B2a (L5/E5a) frequency point does not exceed 0.15 m, which is significantly better than the B1C (L1/E1) frequency. The E1 frequency of Galileo has the best CC value with 0.29 m, followed by B1C of BDS-3, which is significantly better than the L1 frequency of GPS and QZSS. The CC values of B2a, L5 and E5a frequency points are very close within 0.05 m.  
The code observation accuracy of B1C/B2a is about 0.05 m better than traditional B1/B2/B3 signals, especially the code observation accuracy of B2a is better than 0.15 m. In comparison with other GNSS, B2a (L5/E5a) is better than B1C (L1/E1) by more than 0.5 meters, except for Galileo. Galileo's E1 and E5 range code accuracy is very close. Therefore, in low-cost navigation applications, if a single-frequency ranging code is used for positioning, the B2a (L5/E5a) frequency is the best choice.