Throughput Maximization for UAV-Enabled Relaying in Wireless Powered Communication Networks

Abstract

This paper investigates mobile relaying in wireless powered communication networks (WPCN), where an unmanned aerial vehicle (UAV) is employed to help information delivery from multiple sources to destination with communication channels severely blocked. The sources are low-power without energy supply. To support information transmission, the UAV acts as a hybrid access point (AP) to provide wireless power transfer (WPT) and information reception for sources. We set the issue of system throughput maximization as the optimization problem. On the one hand, the system is subject to the information causality constraint due to the dependent processes of information reception and transmission for the UAV. On the other hand, the sources are constrained by a so-called neutrality constraints due to the dependent processes of energy harvesting and energy consumption. In addition, we take account of the access delay issue of all ground nodes. Specifically, two paradigms of delay-tolerant case and delay-sensitive case are presented. However, the formulated problem including optimizations for time slot scheduling, power allocation and UAV trajectory is non-convex and thus is difficult to obtain its optimal solution. To tackle this problem, we apply the successive convex approximation (SCA) technique and propose an iterative algorithm by which a suboptimal solution can be achieved. Simulation results validate our proposed design, and show that the obtained suboptimal solution is high-quality, as compared to benchmark scheme.

Ocean Surface Drifting Buoy System Based on UAV-Enabled Wireless Powered Relay Network

“…Several previous works [25][26][27][28][29] have attempted to overcome the above problems by using UAV as a mobile H-AP and constructing UAV-Based WPCN (U-WPCN). The authors of [25] use the UAV as relay node to fly around the fixed ground H-AP with a given radius.…”

“…Our previous work [28] proposed a user grouping and UAV hovering strategy to improve the system's performance by deploying multiple hovering UAVs. As the communication coverage of a single UAV in a hover state is limited, our previous work [29] further considers optimizing the flight path of a single relay UAV to cover a larger area to maximize the system throughput while reducing the delay. However, the fairness problem of maximizing the minimum throughput and the problem of joint trajectory and resource allocation including UAV energy broadcast power optimization has not been considered in our previous works.…”

“…This paper aims to address the difficulties regarding the energy shortage and information transmission in the offshore surface drifting buoy system. Notably, different from the multinode system with limited energy on the ground [29], the UAV-based information collection and energy broadcasting platform is suitable for a floating buoy communication system. The reasons can be summarized as follows.…”

“…Besides, different from the work in [25], we use the UAV as a mobile relay and let it broadcast energy to buoys to guarantee the communication quality even when the buoy lacks energy. Additionally, different from the work in [29], we considered a decode-and-forward (DF) protocol that can forward information in real-time and ensure the effectiveness of information transmission.…”

Joint Trajectory and Communication Design for Buffer-Aided Multi-UAV Relaying Networks

“…In [9], a basic principle combining the path loss exponent and small scale fading was proposed, which analyzed the optimization problem of large scale wireless networks by combining air-to-ground systems and widely used ground-to-ground channel models. In [10], the authors investigated the use of a UAV as a hybrid access point to provide wireless power transfer and assist obstructed ground communications in wireless powered communication networks. In [11][12][13], a new cooperative jamming method was studied to guarantee the communication security between UAVs and ground nodes, which leveraged the jamming from other nearby UAVs to prevent the eavesdropping and combined UAV trajectory and communication design to maximize the average secrecy rate.…”