# Stable Throughput Analysis of Heterogeneous Hybrid FSO/RF Networks with Cognitive Radio Capability
## 6 Numerical Results
Consequently, the  
Figure 5: Comparison of the stable regions for stay-and-switching transmission with \(z=3000\) m, \(z^{I}=2500\) m.  
average number of service packets for the RF pair exceeds 1. Similar trends are observed under haze and moderate rain conditions. Figure 7 compares the stable regions for the SMP with \(z=3000\,\mathrm{m}\) and \(z^{I}=2500\,\mathrm{m}\). The value of \(\lambda_{\texttt{h}0}\) decreases as the interference signal increases when \(z^{I}=3000\,\mathrm{m}\). When \(z^{I}=3000\,\mathrm{m}\), the RF pair can remain stable with \(\lambda_{\texttt{h}0}\leq 1\) in the following ranges of \(\lambda_{\texttt{H}Y}\):  
* For clear conditions: \(0.354<\lambda_{\texttt{H}Y}\),
* For haze: \(0.315<\lambda_{\texttt{H}Y}\), and
* For moderate rain: \(0.205<\lambda_{\texttt{H}Y}\). Figure 6: Comparison of the stable region for SMP with \(z=z^{I}=3000\,\mathrm{m}\). Figure 7: Comparison of stable regions for simultaneous multipacket transmission with \(z=3000\,\mathrm{m}\), \(z^{I}=2500\,\mathrm{m}\). In contrast, when \(z^{I}=2500\,\mathrm{m}\), the RF pair can remain stable with \(\lambda_{\texttt{RD}}\leq 1\) in these ranges:  
* For clear conditions: \(0.307<\lambda_{\texttt{HY}}\),
* For haze: \(0.273<\lambda_{\texttt{HY}}\), and
* For moderate rain: \(0.167<\lambda_{\texttt{HY}}\)  
For the moderate rain scenario, when \(z^{I}=3000\,\mathrm{m}\), the cooperative case always shows a higher \(\lambda_{\texttt{RD}}\) than the REF case. However, when \(z^{I}=2500\,\mathrm{m}\), the REF case has a higher \(\lambda_{\texttt{RD}}\) in the interval \(0.610<\lambda_{\texttt{HY}}<0.652\). For this reason, the interval where \(\lambda_{\texttt{HY}}<0.775\) exhibits a higher \(\lambda_{\texttt{RD}}\) compared to the SMP. In the cognitive FSO/RF system in this study, the interference occurs when the **HY** node transmits or receives RF signals to or from **RF** node, respectively. In the COG system, both \(f_{1}\) and \(f_{2}\) induce such interference, while in the ECO system, the interference only occurs on the \(f_{1}\) channel. In Figures 4 and 6, where the distance between **HY** and **RO** nodes is assumed to be 3000 m, the success probability \(s^{I}_{f_{1},j}\) becomes 0.2389 when the RF interference occurs, while it is 0.6581 without the interference. In Figures 5 and 7, where the above distance is assumed to be 2500 m, the success probability \(s^{I}_{f_{1},j}\) is further reduced to 0.0141 due to the stronger RF interference. For the SAS system demonstrated in Figure 5, an achievable \(\lambda_{RO}\) decreases up to 1.47%, maintaining the same \(\lambda_{HY}\) due to interference. For the SMT system considered in Figure 7, achievable \(\lambda_{HY}\) decreases from 13.27 to 18.53% when \(\lambda_{RO}<1\). Figure 8 illustrates the stability regions for the cooperative system with \(z=z^{I}=3000\,\mathrm{m}\). The SAS-SMP represents the hybrid variation of the cooperative system discussed in (58). In the SAS-SMP configuration, the node HY operates under the SAS, while RO operates under the SMP. Consequently, in clear conditions (\(s_{f_{0}\texttt{HY}}=1\)) and in haze conditions (\(s_{f_{0}\texttt{HY}}=0.731\)), the likelihood of HY transmitting packets through FSO channels, rather than using wireless channels, increases. This, in turn, enhances the probability of successful packet transmission via wireless channels by RO. However, since HY does not operate in SMP, the likelihood that \(Q_{\texttt{HY}}\) is empty decreases. This increase raises the probability of interference between HY and RO within the SMP scenario. Thus, the relationship between \(\lambda_{\texttt{RD}}\) can be summarized as follows: SAS < SAS-SMP < SMP. In a moderate rain scenario, the probability of packet transmission through the FSO link drops to zero. Additionally, the probability that HY in SAS-SMP generates an interference signal on channel \(f_{1}\) is lower than that of HY in SMP. For this reason, the interval where \(\lambda_{\texttt{HY}}<0.775\) exhibits a higher \(\lambda_{\texttt{RD}}\) compared to SMP.