Wireless Networks with RF Energy Harvesting: A Contemporary Survey Xiao Lu, Ping Wang, Dusit Niyato, Dong In Kim, and Zhu Han Abstract—Radio frequency (RF) energy transfer and harvesting techniques have recently become alternative methods to power the next generation wireless networks. As this emerging technology enables proactive energy replenishment of wireless devices, it is advantageous in supporting applications with quality of service (QoS) requirements. In this paper, we present an extensive literature review on the research progresses in wireless networks with RF energy harvesting capability, referred to as RF energy harvesting networks (RF-EHNs). First, we present an overview of the RF-EHNs including system architecture, RF energy harvesting techniques and existing applications. Then, we present the background in circuit design as well as the state-of-the-art circuitry implementations, and review the communication protocols specially designed for RF-EHNs. We also explore various key design issues in the development of RF-EHNs according to the network types, i.e., single-hop networks, multi-antenna networks, relay networks, and cognitive radio networks. Finally, we envision some open research directions. Index terms- RF energy harvesting, simultaneous wireless information and power transfer (SWIPT), receiver operation policy, beamforming, communication protocols, RF-powered Cognitive radio network. This paper aims to provide a comprehensive survey on the contemporary research in RF-EHNs. The scope of this survey covers circuit design, communication protocols as well as the emerging operation designs in various types of RF-EHNs. Note that we emphasize on the design issues related to communications in RF-EHNs. The hardware technology for RF energy harvesting electronics is beyond the scope of this paper. Figure 1 outlines the main design issues for RF-EHNs. The survey is organized as following. The next section presents an overview of RF-EHNs with the focus on the system architecture, RF energy sources and harvesting techniques as well as existing applications. Section III introduces the principle and hardware implementation of RF harvesting devices. Then, we introduce the main design issues with single-hop RF-EHNs, multi-antenna RF-EHNs, and multi-hop RF-EHNs in Section IV, Section V, and Section VI, respectively. We also shed light on the arising challenges in RF-powered cognitive radio networks in Section VII. Then, in Section VIII, we review existing communication protocols designed exclusively for RF-EHNs. Section IX envisions the future directions of RF-EHNs and discuss the practical challenges. Finally, Section X concludes this survey. This paper presents a comprehensive survey on the contemporary research in RF-EHNs. The scope of this survey covers circuit design, communication protocols as well as the emerging operation designs in various types of RF-EHNs. Note that we emphasize on the design issues related to communications in RF-EHNs. The hardware technology for RF energy harvesting electronics is beyond the scope of this paper. FigureWireless Networks with RF Energy Harvesting: A Contemporary Survey Xiao Lu, Ping Wang, Dusit Niyato, Dong In Kim, and Zhu Han Abstract—Radio frequency (RF) energy transfer and harvesting techniques have recently become alternative methods to power the next generation wireless networks. As this emerging technology enables proactive energy replenishment of wireless devices, it is advantageous in supporting applications with quality of service (QoS) requirements. In this paper, we present an extensive literature review on the research progresses in wireless networks with RF energy harvesting capability, referred to as RF energy harvesting networks (RF-EHNs). First, we present an overview of the RF-EHNs including system architecture, RF energy harvesting techniques and existing applications. Then, we present the background in circuit design as well as the state-of-the-art circuitry implementations, and review the communication protocols specially designed for RF-EHNs. We also explore various key design issues in the development of RF-EHNs according to the network types, i.e., single-hop networks, multi-antenna networks, relay networks, and cognitive radio networks. Finally, we envision some open research directions. Index terms- RF energy harvesting, simultaneous wireless information and power transfer (SWIPT), receiver operation policy, beamforming, communication protocols, RF-powered Cognitive radio network. This paper aims to provide a comprehensive survey on the contemporary research in RF-EHNs. The scope of this survey covers circuit design, communication protocols as well as the emerging operation designs in various types of RF-EHNs. Note that we emphasize on the design issues related to communications in RF-EHNs. The hardware technology for RF energy harvesting electronics is beyond the scope of this paper. Figure 1 outlines the main design issues for RF-EHNs. The survey is organized as following. The next section presents an overview of RF-EHNs with the focus on the system architecture, RF energy sources and harvesting techniques as well as existing applications. Section III introduces the principle and hardware implementation of RF harvesting devices. Then, we introduce the main design issues with single-hop RF-EHNs, multi-antenna RF-EHNs, and multi-hop RF-EHNs in Section IV, Section V, and Section VI, respectively. We also shed light on the arising challenges in RF-powered cognitive radio networks in Section VII. Then, in Section VIII, we review existing communication protocols designed exclusively for RF-EHNs. Section IX envisions the future directions of RF-EHNs and discuss the practical challenges. Finally, Section X concludes this survey. This paper presents a comprehensive survey on the contemporary research in RF-EHNs. The scope of this survey covers circuit design, communication protocols as well as the emerging operation designs in various types of RF-EHNs. Note that we emphasize on the design issues related to communications in RF-EHNs. The hardware technology for RF energy harvesting electronics is beyond the scope of this paper. Figure