Subchannel Allocation for UAV-Enabled OFDMA Systems with UAV Placement and User Association

Unmanned aerial vehicles (UAVs)-based network has always been recognized as one significant technology to yield sustainable connectivity, wide coverage and well Quality of Service (QoS). With the target to improve the network fairness, this paper investigates the subchannel allocation as well as UAV placement and user association problem in UAVs-based OFDMA communication system. Considering the co-channel interference, the joint design has been formulated as one max-min optimization problem, which is a mixed-integer nonlinear model. To tackle this challenge, this article decomposes the joint optimization problem into two subproblems. To facilitate the UAV placement and user association design, this paper derives one K-means clustering-based scheme to optimize the multiple UAVs deployment and user pairing scheme. For the subchannel assignment subproblem, one iterative algorithm based on successive convex approximation and alternating optimization has been developed to obtain an effective design. Finally, numerical results are presented to verify the effectiveness of the proposed algorithm as compared to basic benchmarks.