A Comprehensive Survey on RF Energy Harvesting: Applications and Performance Determinants

Abstract

There has been an explosion in research focused on Internet of Things (IoT) devices in recent years, with a broad range of use cases in different domains ranging from industrial automation to business analytics. Being battery-powered, these small devices are expected to last for extended periods (i.e., in some instances up to tens of years) to ensure network longevity and data streams with the required temporal and spatial granularity. It becomes even more critical when IoT devices are installed within a harsh environment where battery replacement/charging is both costly and labour intensive. Recent developments in the energy harvesting paradigm have significantly contributed towards mitigating this critical energy issue by incorporating the renewable energy potentially available within any environment in which a sensor network is deployed. Radio Frequency (RF) energy harvesting is one of the promising approaches being investigated in the research community to address this challenge, conducted by harvesting energy from the incident radio waves from both ambient and dedicated radio sources. A limited number of studies are available covering the state of the art related to specific research topics in this space, but there is a gap in the consolidation of domain knowledge associated with the factors influencing the performance of RF power harvesting systems. Moreover, a number of topics and research challenges affecting the performance of RF harvesting systems are still unreported, which deserve special attention. To this end, this article starts by providing an overview of the different application domains of RF power harvesting outlining their performance requirements and summarizing the RF power harvesting techniques with their associated power densities. It then comprehensively surveys the available literature on the horizons that affect the performance of RF energy harvesting, taking into account the evaluation metrics, power propagation models, rectenna architectures, and MAC protocols for RF energy harvesting. Finally, it summarizes the available literature associated with RF powered networks and highlights the limitations, challenges, and future research directions by synthesizing the research efforts in the field of RF energy harvesting to progress research in this area.

Radiofrequency Energy Harvesting Systems for Internet of Things Applications: A Comprehensive Overview of Design Issues

“…The solutions for minimizing WSs’ energy budget are often ignored or treated independently. Other studies related to ours are proposed in [ 15 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]; a summary of the key points developed in these related studies is proposed in Table 1 .…”

“…However, energy management protocols were not discussed. Performance metrics of RF-EH systems, as well as power management protocols, have been discussed by Hafiz et al in [ 25 ]. However, MEB-WS solutions have not been addressed.…”

Printed Electronics in Radiofrequency Energy Harvesters and Wireless Power Transfer Rectennas for IoT Applications

“…[ 43 ] Radiofrequency energy harvesting (RF EH) is the technique of harvesting power from ambient electromagnetic (EM) radiation sources in radio frequency (between 3 kHz and 300 GHz) available freely in the device deployment environment, utilizing a rectifying antenna (Figure 1e). [ 13 ] EM radiation sources above the RF spectrum—infrared and visible light, up to 700 THz [ 44 ] —can also be harvested using nanometer‐size rectifying antennas. However, practical implementation is limited by either unsatisfying diode integration for the rectification step to happen at terahertz frequencies in a top‐down approach (e.g., nanolithography methods) or difficult collection of the rectified charges (e.g., molecular diodes with nanoparticles patch antennas).…”

Statistical Characterization of Wireless Power Transfer via Unmodulated Emission

“…Research in RF-EH has already produced significant results, as indicated in recent survey papers. Examples are [ 1 , 2 , 3 , 4 , 5 , 6 ]. Moreover, relatively new books like [ 7 ] or [ 8 ] contain good compilations of the main contributions and results.…”

“…First, the propagation models used in RF-EH are outlined in some of the above survey papers. This is the case of [ 1 , 6 ], which includes a brief description of wireless propagation through manageable models such as free-space, two-ray, or Rayleigh fading [ 4 ], which recalls the free-space and two-ray models and [ 5 ], which only makes reference to the Friis path-loss formula. As for regular papers, most also adopt simplified propagation models.…”