Research On Dynamic Deployment Strategy Of UAV Base Stations With Minimum Energy Consumption

With their high mobility,flexibility of deployment and low cost,Unmanned Aerial Vehicles(UAVs)have played an irreplaceable role in the field of military,commercial and civil communication during the past few decades.Among the various applications enabled by UAVs,UAV base stations equipped with wireless communication modules are the best choice to assist or replace ground base stations.Because they can effectively solve the problems that traditional ground base stations cannot be rapidly deployed,cannot meet better coverage and capacity requirements,and are too expensive to consume.At present,there are few studies on the dynamic deployment of UAV base stations.In wireless networks,network load can be highly unbalanced due to the changing location of users over time.Therefore,the mobility of users may cause communication interruption problem.In order to guarantee the Quality of Service(QoS)of users in the target area and avoid communication interruption,it is necessary to deploy UAV base stations dynamically.Therefore,the dynamic deployment of UAV base stations is a worthy problem to study.Facing the foregoing problem,we develop a novel UAV base stations dynamic deployment strategy based on cooperation.First,we obtain the initial deployment scheme.The 3D coordinates and coverage radius of each UAV are attained following Delaunay triangulation.Such an arrangement ensures coverage area without any coverage gaps.Then,we adjust the UAV according to the demands of the users.The location information of the ground users is detected periodically.If overloaded UAVs are detected,we will select cooperative UAVs and adjust their altitude or transmission power to expanding the coverage radius.In this way,redundant users of overloaded UAVs can be served,and the problem of communication interruption can be avoided.Finally,considering the limited energy available to each UAV,cooperative UAVs should be selected and adjusted to minimize energy consumption in the current cycle and extend the service time.Although the problem of communication interruption is solved,the above algorithm only considers the adjustment of cooperative UAVs and keeps the rest of the UAVs in the initial deployment.Therefore,the energy saved by this algorithm is limited.In order to prolong the service time,we propose a dynamic deployment strategy of UAV base stations with minimum energy consumption.By introducing the UAVs’ transmission power and associations as independent variables,the total energy consumption is further optimized.In particular,takeing into account the interdependence among variables,a alternating iterative method is used for jointly optimizing the 3D placement of the UAVs,user-UAV association,and power control.In each iteration process,given the fixed UAVs’ locations,we find the optimal user-UAV association and the transmission power of the UAVs.Next,given the fixed UAV association from the previous step,we determine the suboptimal locations of the UAVs and update the transmit power accordingly.This procedure is done iteratively until a deployment scheme that minimizes the energy consumption of the system is found.Finally,the simulation results show that our algorithms not only solve the problem of communication interruption,but also reduce the energy consumption of system as much as possible.