Fair multiple subchannel assignment and 3‐D UAV‐BS placement in UAV‐Enabled networks

Abstract

This paper focuses on multiple subchannel assignment for ground users in an unmanned aerial vehicle (UAV) enabled network. The main objective is to ensure fair service to all users by maximizing the rate of the worst‐off user. To this end, we jointly optimize the three‐dimensional (3‐D) placements of the UAV‐BSs, the multiple subchannel assignment to each user, and the transmit power of each subchannel. The presented problem is non‐convex in nature. In order to solve this problem, we propose to divide it into three tractable subproblems: user clustering, multiple subchannel assignment, and joint altitude and power optimization. The first subproblem is solved by using the modified K‐means algorithm. A novel algorithm based on the Hungarian‐based dynamic many–many matching (HD4M) algorithm is proposed to solve the second subproblem. To solve the third subproblem, three methods based on sequential quadratic programming (SQP), including our proposed iterative method, are investigated. The simulation results show that our proposed scheme is fair (Jain′s Index 0.945) and that it outperforms the other two schemes in terms of the minimum rate achieved, while also being reasonable in terms of computation time.