## 3 System Model
### Suspicious UAVs' Distance Model  
The distance between \(U\!A\!V_{L}\) and \(U\!A\!V_{ST}\), and the distance between \(U\!A\!V_{L}\) and \(U\!A\!V_{SR}\) relate to the performance of eavesdropping and jamming. Therefore, we will discuss the suspicious UAVs' distance model in this part, which is based on the position of \(U\!A\!V_{L}\) and the suspicious UAVs' dynamic mobility.  
As shown in Figure 3, the distance between \(U\!A\!V_{L}\) and \(U\!A\!V_{ST}\) at time slot \(x\), which was denoted as \(d_{1}(x)\), can be described as:  
\[d_{1}(x)=\sqrt{\left(\frac{D}{2}-\frac{D}{2}\cos\theta(x)\right)^{2}+\left( \frac{D}{2}\sin\theta(x)\right)^{2}}=\frac{\sqrt{2}D}{2}\sqrt{1-\cos\theta(x)} \tag{1}\]  
Additionally, the distance between \(U\!A\!V_{L}\) and \(U\!A\!V_{SR}\), \(d_{2}(x)\), is given by \(d_{2}(x)=\sqrt{D^{2}-d_{1}^{2}(x)}\). Note that \(d_{1}(x)\) and \(d_{2}(x)\) can be also estimated by other ways, e.g., measuring receiving signal strength, or signal angle of arrival of \(U\!A\!V_{ST}\) or \(U\!A\!V_{SR}\).  
The angle variation \(\theta(x)\) depends on the real-time position of \(U\!A\!V_{L}\). However, as shown in Figure 4, the results of \(d_{1}(x)\) is the same as Equation (1), because the expression of variations \(a\) and \(b\) can be transformed under the condition of \(\theta<\pi/2\), which means that  
\[a=\frac{D}{2}\sin(\pi-\theta(x))=\frac{D}{2}\sin\theta(x),b=\frac{D}{2}+\frac {D}{2}\cos(\pi-\theta(x))=\frac{D}{2}-\frac{D}{2}cos\theta(x) \tag{2}\]  
The model is two-dimensional, and considers the dynamic mobility of suspicious UAVs in sequence time slots, as shown in Figure 5. The distance variation \(D\) is improved as a dynamic variation that relates to the time slot,  
\[D(x)=D(x-1)+\varphi\Delta v \tag{3}\]  
Here, \(\varphi\) is the duration of each time slot, and \(\Delta v\) is a vertex that presents the speeds' difference value of \(U\!A\!V_{ST}\) and \(U\!A\!V_{SR}\). We do not include three-dimensional degrees of freedom for improving the security, but that will be our future works.  
\begin{table}
\begin{tabular}{c l} \hline \hline
**Variables** & **Descriptions** \\ \hline \(P_{L}(x)\) & Legitimate monitor consuming power (\(P_{E}(x)+P_{J}(x)\)) at time slot \(x\) \\ \(P_{E}(x)\) & Legitimate monitor eavesdropping power at time slot \(x\) \\ \(P_{J}(x)\) & Legitimate monitor jamming power at time slot \(x\) \\ \(\gamma_{e}(x)\) & SNR of eavesdropping link at time slot \(x\) \\ \(\gamma_{s}(x)\) & SNR of suspicious link at time slot \(x\) \\ \(K_{1},K_{2}\) & Two constants relating to the channel \\ \(N_{0}\) & Power of white Gaussian noise \\ \(d_{1}(x)\) & Distance between \(U\!A\!V_{L}\) and \(U\!A\!V_{ST}\) at time slot \(x\) \\ \(d_{2}(x)\) & Distance between \(U\!A\!V_{L}\) and \(U\!A\!V_{SR}\) at time slot \(x\) \\ \(P_{L}^{max}\) & Maximum consuming power of \(U\!A\!V_{L}\) \\ \(P_{L}^{total}\) & Total jamming power of \(U\!A\!V_{L}\) \\ \(n\) & Gaussian random number \\ \(\alpha_{1},\alpha_{2}\) & Path-loss exponent of wireless channel \\ \(\lambda\) & Coefficient considered to adjust the weights of the autocorrelated component and \\ \(\delta\) & SINR/SNR threshold \\ \(\rho(x)\) & Adaptive modulation and coding (AMC) rate at time slot x \\ \(\epsilon\) & The required instantaneous bit error rate \\ \hline \hline \end{tabular}
\end{table}
Table 1: Notations and variables.