Wireless Powered Communications: Industry Demands and a User-Centric Energy-Efficient Approach

This paper aims at providing a green battery solution for practical wireless communication systems. First, we discuss the demands and latest developments of wireless energy transfer (WET) in relevant industries. Second, we propose a user- centric energy-efficient approach in wireless powered communication networks (WPCNs), where mobile users first harvest energy from a dedicated power station and then communicate with an information receiving station. Our goal is to maximize the weighted sum of user-centric energy efficiency (WSUEE) via joint time allocation and power control. The proposed approach provides the flexibility of assigning users different levels of importance so that the individual user EE can be balanced. We first study the properties of the WSUEE maximization problem. Then, the closed-form expression of the maximum WSUEE as well as the optimal time allocation and power control are derived. Based on this, we finally characterize the EE tradeoff among users in the WPCN: within a throughput region, all users can achieve their own maximum EEs simultaneously while beyond that region, there exists non-trivial user EE tradeoff. Simulation results verify our theoretical findings and demonstrate the effectiveness of the proposed approach.