Resource Allocation for Multi-UAV Aided MIMO Downlink Transmission Systems

Unmanned aerial vehicle (UAV) communication is a promising technology for future communication systems. In this paper, we combine UAV communication and multiple-input-multiple-output (MIMO) technology for constructing a high system capacity downlink transmission system, where UAVs act as aerial base stations to provide downlink transmission service for ground user nodes. We aim to maximize the downlink total system capacity by jointly optimizing the user clustering, the time assignment, and the transmit power of UAVs with guaranteed quality of service (QoS) requirements. Firstly, in order to eliminate inter-cell interferences, we propose a novel precoding scheme based on ZF precoding. Then, an improved K- means method is used for user clustering, followed by an efficient iterative time slot assignment algorithm. Finally, an iterative algorithm based on successive convex approximation(SCA) is proposed to solve the power allocation problem. Numerical results demonstrate the superiority of our proposed scheme.