## 4 Simulation Verification
### False Bit Rate and False Packet Rate  
Communication stability is the aim pursued by cooperative communication [27; 33; 34], retransmission signal is the key technique to improve stability. The two values of bit error rate and packet error rate are common parameters to evaluate the retransmission signal algorithm. In the retransmission process of cooperative communication, the above two parameters are calculated by the following equation. Bit Error Rate (BER)  
The multi-channel average node instantaneous signal-to-noise ratio (\(\gamma\)) in cooperative communication is calculated by the following equation [27]  
\[\gamma_{u,v}=\left|h_{u,v}\right|^{2}\cdot\left(P_{u}/N_{0}\right) \tag{9}\]  
Figure 3: Cooperative communication retransmission experimental test. \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & \multicolumn{1}{c}{**Parameter Value**} \\ \hline Network coverage area & 100 m \(\times\) 100 m \\ Number of UAVs & 20 \\ Signal transmission stage & 2 \\ Broadcast energy consumption & 0.75 J \\ Forwarding energy consumption & 0.5 J \\ Maximum number of rounds & 1000 round \\ System Energy & 100 J \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Experimental parameter setting. In the formula, \(h\) indicates the channel gain of multiple links, \(P_{u}\) is the probability of the decoding error of the signal, \(N_{0}\) is a fixed value, the value is related to the logarithm of 2. The decoding error probability in the multi-relay link retransmission is calculated, and the following equation is the expression for the calculation [33]. \[ \begin{array}{l}P_{b}\big{(}\overline{\gamma}_{s,i,d}\big{)}=P_{b}\big{(} \overline{\gamma}_{s,i}\big{)}+P_{b}\big{(}\overline{\gamma}_{i,d}\big{)}-2P_ {b}\big{(}\overline{\gamma}_{s,i}\big{)}P_{b}\big{(}\overline{\gamma}_{i,d} \big{)}\\ =\frac{1+\overline{\gamma}_{s,i}+\overline{\gamma}_{i,d}}{2(1+\gamma_{s,i}) \big{(}1+\gamma_{i,d}\big{)}}n\end{array}  \tag{10}\]  
In the equation, \(s\), \(r\), \(d\) represent source node, relay node and destination node, respectively, \(s\), \(r\), and \(P\) denote the probability of error. \(P\) can be solved by the signal-to-noise ratio (\(\gamma\)). \(i\) = (1, 2, 3, \(\cdots\), n). Packet Error Rate (PER)  
The calculation of the packet error rate requires a distribution calculation. According to the process of retransmitting signals in cooperative communication, first, the PER of the signal broadcast is calculated, then the PER of the signal forwarding is solved, and finally, the PER of the retransmission process is calculated. The PER of the broadcast process is solved by the following equation [33]. \[P_{P}\big{(}\overline{\psi}_{s,i}\big{)}=1-\big{(}1-P_{b}\big{(}\overline{ \gamma}_{s,i}\big{)}\big{)}^{N_{t}} \tag{11}\]  
In the formula, the BER symbol of the system is when \(P_{P}\), and the symbol of the node when the subscript is \(i\) = (1, 2, 3, \(\cdots\), n). The PER value of the relay node after forwarding the signal is solved by the following equation [34]. \[P_{P,ARQ_{xi}}=\int_{0}\Big{(}1-\big{\{}1-P_{p}(\gamma_{s,i})P_{b,i}(2\gamma_ {s,i})\big{\}}^{N_{t}}\Big{)}\cdot f_{\gamma_{t}}(\gamma_{s,i})d\gamma_{s,i} \tag{12}\]  
In the formula, \(f\) is the calculated coefficient of the signal-to-noise ratio, in this case, the exponential function \(i\) = (1, 2, 3, \(\cdots\), n). After a relay forwarding failure, the PER of the retransmission process is calculated by the following formula [34]. \[P_{p,i}=\sum_{i=1}^{N}\int_{0}^{\infty}P_{p}(\gamma_{i,d})f_{\gamma_{s}}( \gamma_{i,d})\cdot\prod_{j=1,j\in i}^{N}F_{\gamma_{s}}(\gamma_{i,d})d\gamma_{ i,d} \tag{13}\]  
\[F_{y_{ji}}(\gamma_{i,d})=\int_{0}^{\gamma_{i,D}}f_{y_{i}}\big{(}\gamma_{j,d} \big{)}d\gamma_{j,d}=1-\exp\Big{(}-\gamma_{i,d}/\overline{y}_{j,d}\Big{)} \tag{14}\]  
In the formula, \(F\) for maximum link information, \(i\) = (1, 2, 3, \(\cdots\), n).