LAUSR

In this work, a relay-based UAV-assisted cooperative communication for emergency applications is proposed for rural and semi-urban scenarios. 3-D deployment of multiple UAVs is resolved by jointly optimizing the height and transmit power of cluster UAVs and the optimal trajectory of relay UAVs is perfected by using the graph theory approach. While the majority of works in literature use UAVs as aerial base stations or as relays, this paper proposes to use UAVs as both relays and aerial base stations. Furthermore, this is one of the few works where UAVs are used as both static base stations (cluster UAVs) and mobile base stations (relay UAVs). The proposed 3-D deployment and trajectory planning algorithm is implemented at the ground base station (${\text {GBS}}$) and the resultant parameters will be distributed to cluster UAVs either directly or through relay UAVs. A four-step approach is proposed to solve the 2-D location coordinates of cluster UAVs, to find the location of the ${\text {GBS}}$, the power-height optimization of cluster UAVs, and to optimize the trajectory of relay UAVs. The number of users served, channel capacity achieved, power saved due to optimal deployment, latency reduced, and power saving by optimal trajectory are some of the performance metrics used to evaluate the proposed algorithms. The simulation results are validated to show that the proposed solutions outperform existing similar approaches.