# Topology Duration Optimization for UAV Swarm Network under the System Performance Constraint
## 4 The Proposed GTSC Method
### Topology Generation
MST method is a representative topology construction method with fast convergence speed, while K-means is one of the most typical clustering methods for topology construction. On the other hand, PSO-based method is usually used for performance comparison due to its ability to intelligently find approximate optimal solution. The topology duration is also set as the optimization function of PSO method in our simulations. IWLC is a novel location-based K-means++ clustering algorithm where factors included residual energy \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Number of UAVs & \(N=\) 32, 64, 128, 256, 512 \\ \hline UAV transmission range & \(R=\) 80 m \\ \hline UAV speed & \(v=\) 20–30 m/s \\ \hline UAV position update interval & \(\tau=\) 1 s \\ \hline Mobility model & BOIDs model \\ \hline Transmitting energy consumption & \(E_{elec}=\) 50 nJ/bit \\ \hline Power amplifier parameter & \(\varepsilon_{fs}=\) 100 pJ/bit/m\({}^{2}\) \\ \hline Experience parameter & \(\omega_{1}\), \(\omega_{2}=\) 0.7, 0.3 \\ \hline Weighted parameter & \(\mu_{1}\), \(\mu_{2}\), \(\mu_{3}\), \(\mu_{4}=\) 0.35, 0.15, 0.3, 0.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters. ratio, adaptive node degree, relative mobility and average distance are considered in clustering process. DCM is a double cluster heads based topology construction method which utilizes the latest swarm intelligence algorithm, PO algorithm for clustering. Moreover, the load balancing of the cluster heads is also considered in the DCM method. ### Effectiveness of Proposed Method

Figure 4 shows the swarm network topology constructed based on the novel group trend similarity based double-head clustering method with \(N=32\). Figure 4a is the initial nodes distribution in the 3D space. As shown in Figure 4b, in the constructed topology, the UAV swarm is divided into three clusters and all nodes are connected through cluster heads. Figure 4c,d is the network topology after a period of operation. It can be seen that when the position of swarm nodes constantly changing, the constructed topology is still able to ensure the connectivity of the network, which proves the effectiveness of the proposed method. ### Topology Duration

Figure 5 shows the results of topology duration of the network topology obtained by the proposed GTSC method, as well as the MST, K-means, PSO-based, IWLC and DCM methods. As shown, when the number of nodes increases, the topological duration of all methods decreases. It can also be seen obviously that our proposed topology construction method can always achieve better topology duration than any other methods. The topology duration of the proposed GTSC method is nearly twice as the other methods when the number of nodes reaches 512. This is mostly due to the joint consideration of the instantaneous and dynamic characteristics of swarm in our proposed method. The similarity map based clustering method makes the links less likely to disconnect as node position changes. Moreover, the double cluster heads scheme plays an important role in

Figure 4: The network topology of UAV swarm constructed based on the proposed GTSC method. maintaining topological structure and balancing the energy consumption of the double cluster heads, which results in the DCM method has the closest performance to ours. ### End-to-End Delay

Figure 6 illustrates the comparison of average end-to-end delay when routing packets based on topology constructed by different methods. As the number of nodes increases, the end-to-end delay of the proposed GTSC method becomes increasingly better than that of the other methods. When the number of nodes reaches 512, the end-to-end delay of the proposed method is less than 0.06 s, while the K-means and PSO methods are over 0.08 s, and the DCM is nearly 0.07 s. It can be assumed that as the number of nodes continues increasing, the advantages of the proposed method in terms of end-to-end delay will become more apparent.