# Method for Estimating the Optimal Coefficient of L1C/B1C Signal Correlator Joint Receiving
## 3 The Joint Receiving Scheme of Correlator
### Optimal Coefficient Estimation of Code Loop
Next, the theoretical code discrimination error of the combined signal is simulated, where the coherent integration time is 10 ms, the code loop noise bandwidth is 5 Hz, and the phase detector interval is 0.08 chips. Figure 6 shows the standard deviation of discrimination for DLL in different combination schemes for the B1C/L1C signal. The tracking accuracy of the amplitude combination is the best at different receiver front-end bandwidths and carrier-to-noise ratios. Figure 7 simulates the theoretical standard deviation of discriminator for the code loop in different phase-detector intervals. The simulation results show that the tracking method of amplitude ratio combination has the highest accuracy for the B1C and the L1C in the main lobe bandwidth (32 MHz), followed by the power ratio combination and, finally, the equal weight combination (1:1 combination). \begin{table}
\begin{tabular}{c c c} \hline
**1:1 Combination** & **Amplitude Ratio Combination** & **Power Ratio Combination** \\ \hline \(\alpha=1\) & \(\alpha=0.366\) & \(\alpha=0.25\) \\ \(\beta=1\) & \(\alpha=0.634\) & \(\alpha=0.75\) \\ \hline \end{tabular}
\end{table} 
Table 2: L1C/B1C signal combination coefficient. Figure 6: The DLL standard deviation. To further determine the accuracy of the combined reception of the L1C and the BIC signals, Figure 8 intensively simulates the difference in standard deviations of the DLL theory of the amplitude ratio combination and power ratio combination under common receiver parameters. The C/N0 of the GNSS ground receives a signal for ordinary users in ranges from 25 dB to 60 dB. Since the platform area designed by the MBOC (6,1,1/11) signal is prone to deadlocking the receiver, the users choose the discriminator interval to be within 0.15 chips. In the common receiving bandwidth of the usesr receiver, including the main lobe bandwidth (16 MHz), transmitting bandwidth (32 MHz) and wideband receiving (40 MHz), the difference between the DLL theoretical discrimination's standard deviation of the power ratio combination and amplitude ratio combination is simulated for the BIC and the L1C. Figure 8: The DLL standard deviation of the ‘power ratio combination’ minus the ‘amplitude ratio combination’ for the BIC (L1C). Figure 7: The DLL std of the three combination schemes, Bf = 32 MHz. The simulation results show that, for weaker signals (less than 40 dB), the amplitude ratio combination is considerably better than the power ratio combination. For stronger signals (greater than 40 dB), when users select the phase detector interval within a 0.1 chip, the amplitude ratio combination is slightly better than the power ratio combination. Otherwise, when the receiver selects from 0.1 chips to within 0.15 chips, the power ratio combination is slightly better than the amplitude ratio combination. The amount is so small that it can be ignored. The above analysis shows that combined tracking is applied to weaker signals in most cases, which can further improve tracking accuracy. In addition, we recommend that users select the amplitude ratio combination method for correlator joint-receiving, which can maximize the combined tracking accuracy.