Optimal stratified placement of balloons and UAVs to support users’ coverage

Unmanned aerial vehicles (UAVs) base stations are a promising solution to provide better coverage to ground users. In this paper, balloons, UAVs and users are deployed to efficiently enhance users’ coverage. This paper studies three deployment problems: (i) placement of balloons to aid UAVs for wireless assistance, (ii) placement of UAVs to provide coverage to users, and (iii) a joint problem for successful deployment of balloons, UAVs, and connectivity to users. Firstly, an optimization problem is formulated to minimize the number and costs of balloons. Secondly, the goal is to minimize the number of UAVs, maximize the number of users’ connections, minimize the distance between users and UAVs, and minimize the UAVs’ deployment costs. Thirdly, a joint problem is also introduced to provide efficient wireless coverage. The problem is formulated as an integer linear program (ILP). An optimal algorithm is used to solve the optimization problem, however, the computational complexity of an optimal algorithm is high. Thus, a low-complexity greedy algorithm is also proposed. Simulation results show the efficiency of the proposed optimal and greedy algorithms.