Distributed Energy Cooperation for Multicell Wireless Powered Communication Networks with Imperfect Energy Storage Efficiency

This paper investigates the energy cooperation for multicell wireless powered communication networks with imperfect energy storage efficiency in a distributed manner. In the considered network, access points (APs) are all powered by renewable energy and charged to associated users via wireless energy transfer in the downlinks. Moreover, the energy cooper-ation scheme enables each AP to share energy with neighboring APs, allowing all users to obtain sustainable energy for wireless information transfer in the uplinks. To avoid the dissipation of unused energy, each AP is equipped with a battery, in which the unused energy can be stored in its battery for subsequent communication. In this practical scenario, energy efficiency is maximized through optimizing energy allocation. Considering that the battery status is constrained by energy causality in the time dimension, the joint analysis based on multiple time intervals is a huge challenge for problem modeling and solving. To this end, a nonconvex problem is formulated to maximize the long-term energy efficiency of the entire network. By using nonlinear fractional programming, the original problem is transformed into a convex form. Then, a distributed iterative algorithm based on the partial Lagrange dual decomposition is proposed to alleviate the dependence on the central controller. Finally, a simulation example is presented to validate the main results.

I. Introduction

Intelligent electronic devices have been increasingly ac-commodated into our daily lives, which puts forward higher requirements for device batteries. However, the wired charging method and frequent battery replacement greatly deteriorate network performance and are even impractical in specific scenarios, such as biomedical implants [1] and unmanned aerial vehicles (UAV s) [2]. To improve user experience, wire-less energy transfer (WET) [3], [4], as an emerging charging technique, provides an efficient and stable multicasting way for charging portable batteries of users. In recent years, wireless powered communication networks (WPCNs), the wireless net-works with WET enabled, have become an important building block for many industrial systems, such as the Internet of Things [5] and smart gird [6].