# Topology Duration Optimization for UAV Swarm Network under the System Performance Constraint
## 2 Related Works
Firstly, it assigns the nodes with nearest neighbor distances into the same cluster to reduce the energy consumption of nodes during data transmission; then, the PSO algorithm is employed in the selection of cluster heads, in which the average distance and the residual energy of nodes are considered. The Hybrid Gray Wolf Optimization (HGWO) algorithm is proposed in [19]. In the step of clustering, the optimal number of cluster heads is designed to reduce the energy consumption during data transmission. In the step of cluster head selection, node residual energy, nodes' degree, and relative distance are also jointly considered. Reference [21] proposes a Binary Whale Optimization (BWOA) algorithm to select optimal cluster heads by jointly considering node residual energy, intra-cluster node distance, inter-cluster node distance and the cluster size balance. The scheme of cluster size balance is used for achieving a balance number of cluster member for different clusters, which will consequently balance the energy consumption and data transmission for all cluster head nodes. An energy-efficient Improved Weighted and Location-based Clustering (IWLC) algorithm is proposed in [20], in which not only the node residual energy, nodes' degree, relative distance, but also, the relative motion between nodes is considered in the step of cluster head selection. It will be more valuable to takes into account the mobility of swarm throughout the whole topology construction process. Although the reduction of energy consumption would indirectly improve some specific network performance, many researchers have proposed topology construction algorithms that takes network performance as the optimization objective. Reference [22] adopts the intra-cluster communication delay as the criterion for the topology construction. The authors optimized the intra-cluster communication delay by restricting the cluster diameter and number of cluster members. Moreover, under the restriction of the cluster diameter and number of cluster members, a Coalition Game Theory (CGT) based method is employed to select the nodes with similar mobility as the members of cluster. A Connected Dominating Set (CDS) based method has been proposed in [23], where maximizing the network throughput is adopted as the optimization objective in the topology construction process. First of all, the authors find the global transmission power while guaranteeing bi-connectivity of the network. Secondly, the Minimum Spanning Tree (MST) is constructed by using the page rank algorithm (PRA). Finally, in order to maximize the network throughput, the nodes position is adjusted by employing the PSO algorithm. In [24], the authors proposed a novel clustering method with double cluster heads for the topology construction of swarm, in which the Political Optimizer (PO) algorithm is employed in the selection of double cluster heads. The PO-based method achieved a traffic balance with double cluster heads mechanism by splitting the network load between two cluster heads based on Shannon entropy function. Simulation results show that the load-balance mechanism can achieve desirable end to-end performance when associated with standard routing protocols.