In recent years, unmanned aerial vehicle (UAV) networks have been a focus area of the academic and industrial research community. They have been used in many military and civilian applications. UAV networks have unique features and characteristics that are different from mobile ad hoc networks and vehicular ad hoc networks. In dynamic multi-UAV networks, localization, clustering and routing are the fundamental functions for cooperative control. However, due to the high mobility of UAVs and rapid topology change, UAV localization, clustering and routing are the challenging task. In order to improve the network performance, the clustering approach has been used to address the UAV routing problem. In multi-UAV networks, clustering is used to handle the scalability and stability of networks. Due to energy limitations, network lifetime is a crucial parameter in UAV networks. Furthermore, due to the high mobility of UAVs, topology control is essential to reduce communication interference. Finally, the use of localization with clustering in UAV networks can increase network performance with lower overhead, latency, and energy consumption.
In the first work, we propose a location-aided delay tolerant routing (LADTR) protocol for UAV networks for use in post-disaster operations, which exploits location-aided forwarding combined with a store-carry-forward (SCF) technique. Ferrying UAVs are introduced to enable an efficient SCF, and this is the first attempt at introducing and using ferrying UAVs for routing in UAV networks, to the best of our knowledge. Ferrying UAVs improve the availability of connection paths between searching UAVs and the ground station, thus reducing end-to-end delays and increasing the packet delivery ratio. Future UAV locations are estimated based on the location and speed of UAVs equipped with a global positioning system. The forwarding UAV node predicts the position of the destination UAV node and then decides where to forward. The proposed LADTR ensures that the contact rate between UAV nodes remains high, which enables a high packet delivery ratio, and ensures single-copy data forwarding to avoid replication of each message.
In the second work, we propose swarm-intelligence-based localization and clustering schemes in UAV networks for emergency communications. First, we propose a new three-dimensional (3D) swarm-intelligence-based localization (SIL) algorithm based on particle swarm optimization (PSO) that exploits the particle search space in a limited boundary by using the bounding box method. In the 3D search space, anchor UAV nodes are randomly distributed and the SIL algorithm measures the distance to existing anchor nodes for estimating the location of the target UAV nodes. Convergence time and localization accuracy are improved with lower computational cost. Second, we propose an energy-efficient swarm-intelligence-based clustering (SIC) algorithm based on PSO, in which the particle fitness function is exploited for inter-cluster distance, intra-cluster distance, residual energy, and geographic location. For energy-efficient clustering, cluster heads are selected based on improved particle optimization.
In the last work, we propose bio-inspired localization and clustering schemes in UAV networks for wildfire detection and monitoring. First, we propose an energy-efficient bio-inspired three-dimensional localization (BIL) algorithm. The algorithm is based on hybrid grey wolf optimization (HGWO), which can reduce node localization errors and avoid flip ambiguity (FA) in bounded distance measurement errors and achieves high localization accuracy. After measuring the distance between UAV nodes, the HGWO algorithm estimates the locations of the UAVs, which ensures the global convergence of the results. Second, based on the HGWO algorithm, we propose a new energy-efficient bio-inspired clustering (BIC) algorithm to save the energy of UAVs. The BIC algorithm utilizes the grey wolf leadership hierarchy to improve clustering efficiency. Furthermore, we develop an analytical model for determining the optimal number of clusters that provide the minimum number of transmissions. Finally, we propose GWO-based compressive sensing (CS-GWO) to transmit data from cluster heads (CHs) to the base station (BS). The proposed CS-GWO constructs an efficient routing tree from CHs to BS, thereby reducing the routing delay and the number of transmissions.
The performance of each proposed algorithm has been evaluated by computer simulation with the comparison to the existing works. Our performance study shows that the proposed LADTR outperforms the four typical routing protocols reported in the literature in terms of packet delivery ratio, average delay, and routing overhead. The proposed SIC outperforms five typical routing protocols regarding to packet delivery ratio, average end-to-end delay, and routing overhead. Moreover, SIC consumes less energy and prolongs network lifetime. Finally, the proposed BIL and BIC significantly outperform conventional schemes, in terms of various performance metrics under different scenarios.