Sum Rate Maximization for Multi-UAV Enabled Space-Air-Ground Wireless Powered Communication Networks

Internet of remote things (IoRT) as a platform to support data connections in remote areas has an urgent need for high-throughput and sustainable communications. In this paper, we investigate a multi-unmanned aerial vehicle (UAV) enabled space-air-ground wireless powered communication network (SAG-WPCN) where UAVs are dispatched as decode-and-forward (DF) relays to assist the communication from the ground nodes (GNs) to the satellite, and equipped with wireless power transfer payload providing ubiquitous wireless energy for GNs. This paper aims to maximize the system sum rate by jointly optimizing the time slot division, subchannel allocation, power control and UAV relays deployment. However, the optimization problem is a non-convex problem which is difficult to be solved directly. Therefore, we apply the alternating optimization method and successive convex approximation (SCA) technique to transform the non-convex problem into a tractable form. Subsequently, a near optimal multi-variable alternating iterative algorithm is proposed to obtain a resource allocation scheme of the overall problem. It is revealed that the proposed algorithm significantly improves the performance in terms of the system sum rate compared with other benchmark schemes.