# Radio Frequency Compatibility Evaluation of S Band Navigation Signals for Future BeiDou
## 4 Radio Frequency Compatibility Evaluation
In previous analysis, we know that  
Figure 4: The \(\Delta(C/N_{0})_{\text{eff,SSC}}^{\text{inter,worst}}\) of Galileo candidate CBOC(6,1,1/11) in dB level interfered by BDS: (a) CPM(8); (b) BOCs(4,4); (c) BPSK(8); (d) MSK-BOCs(4,4). MSK-BOCs(4,4) has better SSC of \(-80.32\) dB with BPSK(1), which implies that they allow peaceful coexistence with minimal mutual interference in signal acquisition. A perfect agreement can be observed in Figure 6, indicating that the mean \(\Delta(C/N_{0})^{\text{inter,worst}}_{\text{eff,SSC}}\) of BPSK(1) induced by MSK-BOCs(4,4) is around 0.006 dB, 0.001 dB and 0.08 dB smaller than those induced by CPM(8), BOCs(4,4) and BPSK(8) respectively. In code tracking, it is shown from Figure 7 that CPM(8) results in the minimal mean \(\Delta(C/N_{0})^{\text{inter,worst}}_{\text{eff,CTSC}}\) of 0.01239 dB on Galileo BPSK(1) that are approximately 0.029 dB, 0.098 dB and 0.018 dB smaller than BOCs(4,4), BPSK(8) and MSK-BOCs(4,4), because CPM(8) has the smallest CTSSC at worst situation clearly shown in Figure 2d. Figure 6: The \(\Delta(C/N_{0})^{\text{inter,worst}}_{\text{eff,SSC}}\) of Galileo candidate BPSK(1) in dB level interfered by BDS: (**a**) CPM(8); (**b**) BOCs(4,4); (**c**) BPSK(8); (**d**) MSK-BOCs(4,4). Figure 7: The \(\Delta(C/N_{0})^{\text{inter,worst}}_{\text{eff,CTSC}}\) of Galileo candidate BPSK(1) in dB level interfered by BDS: (**a**) CPM(8); (**b**) BOCs(4,4); (**c**) BPSK(8); (**d**) MSK-BOCs(4,4). Case 3: Galileo candidate BPSK(4) is interfered by BDS candidate signals, i.e. \[\left\{ \begin{array}{l}I_{\text{intra}}=I_{\text{BPSK(4),others}}^{\text{Galileo}}\\ I_{\text{inter}}=I_{\text{candidate}}^{\text{BDS}}\end{array} \right.. \tag{32}\]  
Case 4: Galileo BPSK(8) is interfered by BDS candidate signals, i.e.,  
\[\left\{ \begin{array}{l}I_{\text{intra}}=I_{\text{BPSK(8),others}}^{\text{Galileo}} \\ I_{\text{inter}}=I_{\text{candidate}}^{\text{BDS}}\end{array} \right.. \tag{33}\]  
The compatibility evaluation of Galileo candidate BPSK(4) and BPSK(8) interfered by BDS candidate signals in terms of \(\Delta(C/N_{0})_{\text{eff,SSC}}^{\text{inter,worst}}\) and \(\Delta(C/N_{0})_{\text{eff,CTSSC}}^{\text{inter,worst}}\) are respectively depicted in Figures 8-11. Because of the better SSC and CTSSC of CPM(8) with BPSK(4) and BPSK(8) at worst situation, a conclusion can easily be drawn that the CPM(8) causes the less interference on Galileo candidate BPSK(4) and BPSK(8) in signal acquisition and code tracking than other BDS candidates. These figures also indicate that in worst case the mean performance degradations of BPSK(4) from CPM(8) are respectively at least 0.02 dB and 0.026 dB smaller than those from other BDS candidates for signal acquisition and code tracking, while CPM(8) respectively has more than 0.008 dB and 0.019 dB advantages over other BDS candidates in terms of mean \(\Delta(C/N_{0})_{\text{eff,SSC}}^{\text{inter,worst}}\) and \(\Delta(C/N_{0})_{\text{eff,CTSSC}}^{\text{inter,worst}}\) of BPSK(8) for global scale. Figure 10: The \(\Delta(C/N_{0})_{\text{eff,SSC}}^{\text{inter,worst}}\) of Galileo candidate BPSK(8) in dB level interfered by BDS: (**a**) CPM(8); (**b**) BCCs(4,4); (**c**) BPSK(8); (**d**) MSK-BCCs(4,4). Figure 9: The \(\Delta(C/N_{0})_{\text{eff,CTSSC}}^{\text{inter,worst}}\) of Galileo candidate BPSK(4) in dB level interfered by BDS: (**a**) CPM(8); (**b**) BCCs(4,4); (**c**) BPSK(8); (**d**) MSK-BCCs(4,4). Case 5: IRNSS BOCs(5,2) is interfered by BDS candidate signals, i.e. \[\left\{ \begin{array}{l}I_{\text{intra}}=I_{\text{BOCs(5,2),others}}^{\text{ IRNSS}}+I_{\text{BPSK(1)}}^{\text{IRNSS}}\\ I_{\text{inter}}=I_{\text{candidate}}^{\text{BDS}}\end{array} \right.. \tag{34}\]  
The Figures 12 and 13 illustrate the \(\Delta(C/N_{0})_{\text{eff,SSC}}^{\text{inter,worst}}\) and \(\Delta(C/N_{0})_{\text{eff,CTSSC}}^{\text{inter,worst}}\) of IRNSS BOCs(5,2) caused by BDS candidates.