## 2 System and Channel Model
### Channel Model  
FSO communication links are affected by three main sources of signal attenuation: path loss, PE, and AT. These sources of attenuation affect the transmitted optical signal in various ways. The PDF of the channel attenuation factor \(h_{x}\) is as [27]  
\[f_{h_{x}}(h_{x})=\frac{\alpha_{x}\beta_{x}\varsigma_{x}^{2}}{A_{0,}\Gamma( \alpha_{x})\Gamma(\beta_{x})}G_{1,3}^{3,0}\bigg{(}\frac{\alpha_{x}\beta_{x}h_{ x}}{A_{0,x}}\bigg{|}_{\varsigma_{x}^{2}}-1,\alpha_{x}-1,\beta_{x}-1\bigg{)},x\in\{p,q\} \tag{7}\]Since the jamming event is caused by UAV, the PDF of the channel attenuation factor \(h_{J}\), considering the fluctuations of AT, PE, and AoA, is as [27]  
\[\begin{split} f_{h_{J}}(h_{J})&=\exp\left(-\frac{\varphi _{AoA}^{2}}{2\sigma_{AoA}^{2}}\right)\delta(h_{J})+\left[1-\exp\left(-\frac{ \varphi_{AoA}^{2}}{2\sigma_{AoA}^{2}}\right)\right]\\ &\times\frac{\alpha_{J}\beta_{J}\xi_{J}^{2}}{A_{0_{J}}\Gamma( \alpha_{J})\Gamma(\beta_{J})}\mathrm{G}_{1,3}^{3,0}\left(\frac{\alpha_{J}\beta_ {J}h_{J}}{A_{0_{J}}}\right|\begin{array}{c}\xi_{J}^{2}\\ \xi_{J}^{2}-1,\alpha_{J}-1,\beta_{J}-1\end{array}\right)\end{split} \tag{8}\]  
Here \(\varphi_{AoA}\) is AoA [27], \(\sigma_{AoA}\) is the standard variation of UAV's orientation [28]; \(\alpha_{x}\), \(\beta_{x}\) (\(x\in\{p,q,J\}\)) is the parameters for G-G turbulence for \(x\)th link, i.e., they attain the values \(\{4,1.9\}\) and \(\{4,1.4\}\) for moderate and strong AT regimes, respectively [28]. \(\xi_{x}\) characterizes the PE faced by legitimate or jammer signal: higher the value of \(\xi_{x}\), lower the PE [24; 27]. \(G_{p,q}^{m,n}(\cdot\,|\,)\) is the Meijer-G function [29]. \(A_{0_{x}}(x\in\{p,q,J\})\) is the fraction of collected power at the center of beam footprint [27].  
According to [30], it is known that \(h_{i}=h_{p}\partial e^{i\Psi_{p}}h_{q}\). Thus, we can obtain  
\[f_{h_{i}}(h_{i})=\int_{0}^{\infty}f_{h_{p}}\left(h_{p}\right)f_{h_{i}}\left( \frac{h_{i}}{h_{p}}\right)\frac{1}{h_{p}}dh_{p} \tag{9}\]  
By substituting (7) into (9) and integrating using 07.34.16.0002.01 [29] and 07.34.16.0002.01 [29], we obtain  
\[\begin{split} f_{h_{i}}(h_{i})&=\frac{\alpha_{p} \beta_{p}\xi_{p}^{2}}{A_{0_{p}}\Gamma(\alpha_{p})\Gamma(\beta_{J})}\frac{ \alpha_{q}\beta_{q}\xi_{q}^{2}}{A_{0_{q}}\Gamma(\alpha_{J})\Gamma(\beta_{J})}\\ &\times\mathrm{G}_{2,6}^{6,0}\left(\frac{\alpha_{p}\beta_{p}\alpha _{q}\beta_{q}}{A_{0_{p}}A_{0_{q}}}\right|\begin{array}{c}\xi_{p}^{2},\xi_{q} ^{2}\\ \xi_{p}^{2}-1,\alpha_{p}-1,\beta_{p}-1,\xi_{q}^{2}-1,\alpha_{q}-1,\beta_{q}-1 \end{array}\right)\end{split} \tag{10}\]  
Since \(g_{J}=h_{J}\partial e^{i\Psi_{p}}h_{q}\), we can obtain  
\[f_{g_{J}}(g_{J})=\int_{0}^{\infty}f_{h_{q}}\left(h_{q}\right)f_{h_{j}}\left( \frac{g_{J}}{h_{q}}\right)\frac{1}{h_{q}}dh_{q}=I_{1}+I_{2} \tag{11}\]  
By substituting (7) and (8) into (11), integrating using 07.34.16.0002.01 [29], we obtain  
\[I_{1}=\exp\left(-\frac{\varphi_{AoA}^{2}}{2\sigma_{AoA}^{2}}\right)\delta(g_{ J}) \tag{12}\]  
\[\begin{split} I_{2}&=\frac{\alpha_{q}\beta_{p}\xi_{q}^ {2}}{A_{0_{q}}\Gamma(\alpha_{q})\Gamma(\beta_{q})}\left[1-\exp\left(-\frac{ \varphi_{AoA}^{2}}{2\sigma_{AoA}^{2}}\right)\right]\frac{\alpha_{J}\beta_{J} \xi_{J}^{2}}{A_{0_{J}}\Gamma(\alpha_{J})\Gamma(\beta_{J})}\\ &\times\mathrm{G}_{2,6}^{6,0}\left(\frac{\alpha_{J}\beta_{p}\alpha _{q}\beta_{q}}{A_{0_{J}}A_{0_{q}}}\right|\begin{array}{c}\xi_{J}^{2},\xi_{ q}^{2}\\ \xi_{J}^{2}-1,\alpha_{J}-1,\beta_{J}-1,\xi_{q}^{2}-1,\alpha_{q}-1,\beta_{q}-1 \end{array}\right)\end{split} \tag{13}\]