## 4 Experimental Results and Performance Analysis
### Sensitivity Analysis  
SPL with delta correction technique is used for Doppler estimation in all 4 CD algorithms described previously. Knowing that, in the basic idea of the CD approach, the CD is advantageous if we have as many satellites as possible, but we will compare if there is a big difference between the operation of the best satellites and the exploitation of all available satellites. Considering the previous analysis, the algorithm will compute the CD metric using six satellites (best satellites) instead of nine satellites (all visible satellites). Figure 7 shows the comparison of the sensitivity analysis curves of all four CD algorithms: \"CD/Best_Sat/Best_RS\" (six satellites/RS1), \"CD/Best_Sat/All_RS\" (six satellites/RS1-RS2), \"CD/All_Sat/Best_RS\" (nine satellites/RS1) and \"CD/All_Sat/All_RS\" (nine satellites/RS1-RS2).  
It can be seen that the \"CD/All_Sat/All_RS\" algorithm is the best algorithm in terms of sensitivity. The idea of combining all available satellites is the basic principle of the CD approach to increase sensitivity as much as possible. The algorithms of \"CD/Best_Sat/All_RS\" and \"CD/All_Sat/Best_RS\"  
Figure 7: Sensitivity performance comparison between all four CD algorithms.  
have almost the same performance. \"CD/Best_Sat/Best_RS\" has the lowest performance among all the algorithms (\(-2\) dB-Hz compared to \"CD/All_Sat/All_RS\"). This is due to the use of some selected satellites instead of all available satellites. On the other hand, the difference between \"CD/All_Sat/All_RS\" and \"CD/Best_Sat/All_RS\" is not very remarkable, which could be interesting if we look at the compromise between sensitivity (\(\pm 0.7\) dB-Hz) and complexity (nine satellites vs. six satellites). Thus, using the best satellites makes it possible to have a reasonable sensitivity performance whereas there is a gain in complexity since there is less computation, which makes this proposed strategy interesting.  
To better analyze the sensitivity performance of the all CD algorithms and to demonstrate these discussions, it is also important to see the ratio between the maximum peak and the average of the remaining peaks for each detected satellite. It is shown in Figure 8. In fact, the maximum peak is the peak corresponding to the best combination of code/Doppler during the correlation for each satellite in view. The histograms show the peak of detection corresponding to each visible satellite. For each satellite, we calculate the value of the maximum correlation peak divided by the average value of all the remaining peaks to better analyze the sensitivity.  
The histograms in Figure 8 show the better performance using all the satellites (the basic idea of CD) and combine the two RS compared to other algorithms. We can also notice that the algorithms of \"CD/Best_Sat/All_RS\" and \"CD/All_Sat/Best_RS\" have almost the same performance. We can even see that \"CD/Best_Sat/All_RS\" is better than \"CD/All_Sat/Best_RS\" for SV 30, which may be due to the fact that RS2 receives a higher signal power than RS1 even if the difference is smaller. To better choose the right algorithm, complexity is a very important performance metric that needs to be studied.