UAV-Aided Wireless Power Transfer and Data Collection in Rician Fading

Abstract

A UAV-aided wireless power transfer and data collection network is studied, where it is assumed that when the harvested energy at the sensor node (SN) cannot surpass its circuit activation threshold or the received data rate at UAV falls below a minimal required rate threshold, the information outage occurs. The closed-form expressions of energy outage probability and rate outage probability are derived at first, and then the overall outage probability and coverage performance of the system are analyzed. Based on which, an optimization problem is formulated to minimize the overall outage probability by optimizing UAV's elevation angle and the time splitting (TS) factor. Since the problem is non-convex and has no known solution, an alternating optimization (AO)-based algorithm with Golden-section (GS) based linear search method is designed to find the global optimal solution. In order to explore the maximum coverage area of the UAV for a given tolerable outage probability, another optimization problem is also formulated to maximize the coverage range by optimizing UAV's elevation angle. By using Karush-Kuhn-Tucker (KKT) conditions, the closed-form solution of the optimal elevation angle for maximizing the coverage area is derived. Monte Carlo simulations verify the accuracy of the derived closed-form expression of the overall outage probability and the semi-closed-form expressions of the optimum UAV's elevation angle and TS factor. It shows that there exist a unique optimum elevation angle and the TS factor to achieve the minimum overall outage probability, and significant performance gain can be obtained by using our proposed optimization scheme. The developed theoretical results can be useful to the design of UAV-aided wireless communication systems with wireless power transfer.

Time Allocation and Optimization in UAV-Enabled Wireless Powered Communication Networks

“…As sensors deployed in IoTs are energy-limited nodes and they need to be charged until the energy exceeds the circuit activation threshold to start transmitting data [8], works on UAV-enabled WPCNs [3] - [8] began to study the performance of combining WPT and data collection. Similarly, considering the UAV consumes energy in different manoeuvres, some recent works have started to take UAV propulsion energy into account [24] - [25].…”

“…Also, data collection has not been considered in this work. Thirdly, the purpose of collecting data from the sensors is to offload them to the BS, i.e., the mobile edge computing (MEC) server [28], [29], for computing and decision-making [8]. Thus, data offloading at the BS is an important process that has been ignored in these works.…”

“…However, in practical applications, there are usually multiple sensors. To avoid the inter-user interference caused by data transmission among different sensors, TDMA is employed [8], [30]. After data collection, the UAV flies back to the BS with propulsion energy consumption again, and offloads the collected data to the BS for further processing in the fourth phase.…”

“…Background and Challenges R ECENTLY, unmanned aerial vehicles (UAVs) have been presenting a promising technology in 5G, Internet of Things (IoTs) and the six-generation (6G) communication networks [1], [2]. In particular, there has been a growing interest in studying UAV-enabled wireless powered communication networks (WPCNs) [3] - [4], where the UAV was dispatched to collect data from remote sensors, charge remote sensors or both [3] - [8]. For example, the authors in [3] combined the wireless power transfer (WPT) and wireless information transfer (WIT) in a WPCN, where a UAV with a constant power supply coordinated the WPT/WIT to/from a set of ground users.…”

“…In [7], a novel energyefficient data collection and WPT system using a multiple-input multiple-output (MIMO) full-duplex (FD) UAV was proposed, where simultaneous wireless information and power transfer was explored. In [8], the outage and coverage performance of the UAV-aided WPT and data collection have been studied, where the Rician fading and path loss caused by UAV's elevation angle were considered. In practical applications, one challenge is to schedule the full process of a UAV mission when considering its own energy supply and propulsion in a given time.…”