UAVs deployment optimization in cell-free aerial communication networks

Abstract

This paper tackles the joint problem of user association, channel assignment, UAV placement, and transmit power allocation in cell-free wireless networks. Each user can either be directly connected to a ground base station (GBS) or through UAVs acting as relays. To address this, we formulate the problem mathematically as a mixed-integer non-convex program, to minimize the number of deployed UAVs under data rate requirements and coverage constraints. Since the problem is $\mathrm{NP}$-hard, we propose a model-free algorithm utilizing the deep deterministic policy gradient method to handle UAV deployment and positioning within a continuous space domain. We also propose efficient heuristic and meta-heuristic algorithms for comparison purposes. Simulation results demonstrate the benefits of the cell-free concept in satisfying users and improving the performance of UAV-assisted wireless networks. They also validate the effectiveness of the proposed algorithms in minimizing the required number of deployed UAVs to meet stringent user requirements.