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RF Energy Harvesting and Wireless Power Transfer for IoT

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Communications".

Deadline for manuscript submissions: closed (31 May 2024) | Viewed by 21368

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Special Issue Editors

Dr. Onel Luis Alcaraz López

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Guest Editor

Faculty of Information Technology and Electrical Engineering, University of Oulu, 90570 Oulu, Finland
Interests: sustainable IoT; wireless communications; energy harvesting; wireless power transfer; machine-type communications; signal processing; convex optimization

Dr. Katsuya Suto

E-Mail Website
Guest Editor

Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo 183-8585, Japan
Interests: energy harvesting; wireless power transfer; intelligent reflecting surface; radio propagation; deep learning

Special Issue Information

Dear Colleagues,

Internet of Things (IoT) technologies are becoming the main connectivity backbone of a future data-driven sustainable society. However, major concern related to the lack of efficient solutions for powering and maintaining the uninterrupted operation of the massive number of IoT devices is already emerging. In this regard, energy harvesting (EH) techniques are an attractive solution, as they allow externally recharge batteries, and thus may constitute key components of future sustainable IoT networks.

This Special Issue focuses specifically on radio-frequency (RF) EH and wireless power transfer (WPT) technologies, which have a strong potential for energizing low-power IoT deployments. Despite all the technological advances in RF-EH and WPT in recent years, there are still many challenges and open problems to resolve, especially those related to increasing the end-to-end system efficiency, supporting ubiquitous energy accessibility with stringent quality-of-service guarantees, holistic integration with wireless information transfer systems, and transparently complying with electromagnetic field radiation constraints to mitigate the fear of wireless. Therefore, novel RF-EH/WET mechanisms and technological developments are still necessary to cope with these challenges and promote more standardization attempts and commercial solutions/products.

Prospective authors are invited to submit original manuscripts on topics including, but not limited to:

Simultaneous wireless information and power transfer (SWIPT) and wireless-powered IoT networks;
Waveform, beamforming, and signal design for RF-EH and WPT;
Network architecture and protocol design for RF-EH and WPT within the IoT;
Analytical models of RF-EH and WPT;
Enabling technologies for RF-EH and WPT (e.g., MIMO, millimeter-wave, UAVs, distributed and dynamic architectures);
RF electromagnetic radiation exposure in WPT systems: studies, measurements, control methods;
Experiment and prototype of RF-EH, WPT, and/or SWIPT;
Feasibility and end-to-end efficiency studies of RF-WPT.

Dr. Onel Luis Alcaraz López
Dr. Katsuya Suto
Guest Editors

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Keywords

simultaneous wireless information and power transfer (SWIPT) and wireless-powered IoT networks
waveform, beamforming, and signal design for RF-EH and WPT
network architecture and protocol design for RF-EH and WPT within the IoT
analytical models of RF-EH and WPT
enabling technologies for RF-EH and WPT
RF electromagnetic radiation exposure in WPT systems: studies, measurements, control methods
experiment and prototype of RF-EH, WPT, and/or SWIPT
feasibility and end-to-end efficiency studies of RF-WPT

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Published Papers (12 papers)

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Research

20 pages, 1638 KiB

Open AccessArticle

Modeling and Performance Analysis of LBT-Based RF-Powered NR-U Network for IoT

by Varada Potnis Kulkarni and Radhika D. Joshi

Sensors 2024, 24(16), 5369; https://doi.org/10.3390/s24165369 - 20 Aug 2024

Viewed by 485

Abstract

Energy harvesting combined with spectrum sharing offers a promising solution to the growing demand for spectrum while keeping energy costs low. New Radio Unlicensed (NR-U) technology enables telecom operators to utilize unlicensed spectrum in addition to the licensed spectrum already in use. Along with this, the energy demands for the Internet of Things (IoT) can be met through energy harvesting. In this regard, the ubiquity and ease of implementation make the RF-powered NR-U network a sustainable solution for cellular IoT. Using a Markov chain, we model the NR-U network with nodes powered by the base station (BS). We derive closed-form expressions for the normalized saturated throughput of nodes and the BS, along with the mean packet delay at the node. Additionally, we compute the transmit outage probability of the node. These quality of service (QoS) parameters are analyzed for different values of congestion window size, TXOP parameter, maximum energy level, and energy threshold of the node. Additionally, the effect of network density on collision, transmission, and energy harvesting probabilities is observed. We validate our model through simulations. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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20 pages, 1600 KiB

Open AccessArticle

Human and Small Animal Detection Using Multiple Millimeter-Wave Radars and Data Fusion: Enabling Safe Applications

by Ana Beatriz Rodrigues Costa De Mattos, Glauber Brante, Guilherme L. Moritz and Richard Demo Souza

Sensors 2024, 24(6), 1901; https://doi.org/10.3390/s24061901 - 16 Mar 2024

Viewed by 2198

Abstract

Millimeter-wave (mmWave) radars attain high resolution without compromising privacy while being unaffected by environmental factors such as rain, dust, and fog. This study explores the challenges of using mmWave radars for the simultaneous detection of people and small animals, a critical concern in applications like indoor wireless energy transfer systems. This work proposes innovative methodologies for enhancing detection accuracy and overcoming the inherent difficulties posed by differences in target size and volume. In particular, we explore two distinct positioning scenarios that involve up to four mmWave radars in an indoor environment to detect and track both humans and small animals. We compare the outcomes achieved through the implementation of three distinct data-fusion methods. It was shown that using a single radar without the application of a tracking algorithm resulted in a sensitivity of 46.1%. However, this sensitivity significantly increased to 97.10% upon utilizing four radars using with the optimal fusion method and tracking. This improvement highlights the effectiveness of employing multiple radars together with data fusion techniques, significantly enhancing sensitivity and reliability in target detection. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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16 pages, 18594 KiB

Open AccessCommunication

A Pattern Reconfigurable Antenna Using Eight-Dipole Configuration for Energy Harvesting Applications

by Mohamed Aboualalaa, Hesham A. Mohamed, Thamer A. H. Alghamdi and Moath Alathbah

Sensors 2023, 23(20), 8451; https://doi.org/10.3390/s23208451 - 13 Oct 2023

Cited by 1 | Viewed by 1447

Abstract

A pattern reconfigurable antenna, composed of eight elements, is proposed for energy harvesting applications. Pattern reconfigurable antennas are a promising technique for harvesting from different wireless sources. The radiation pattern of the proposed antenna can be steered electronically using an RF switch matrix, covering an angle range from 0 to 360 degrees with a step size of 45 degrees. The proposed antenna primarily consists of an eight-dipole configuration that shares the same excitation. Each dipole is excited using a balun comprising a quarter-wavelength grounded stub and a quarter-wavelength open-circuit stub. The proposed antenna operates in the frequency range of 4.17 to 4.5 GHz, with an impedance bandwidth of 7.6%. By switching between the different switches, the antenna can be steered with a narrower rotational angle. In addition, the antenna can work in an omnidirectional mode when all switches are in the ON state simultaneously. The results demonstrate a good agreement between the numerical and experimental findings for the reflection coefficient and radiation characteristics of the proposed reconfigurable antenna. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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23 pages, 535 KiB

Open AccessArticle

Resource Allocation for Secure MIMO-SWIPT Systems in the Presence of Multi-Antenna Eavesdropper in Vehicular Networks

by Vieeralingaam Ganapathy, Ramanathan Ramachandran and Tomoaki Ohtsuki

Sensors 2023, 23(19), 8069; https://doi.org/10.3390/s23198069 - 25 Sep 2023

Cited by 1 | Viewed by 1096

Abstract

In this paper, we optimize the secrecy capacity of the legitimate user under resource allocation and security constraints for a multi-antenna environment for the simultaneous transmission of wireless information and power in a dynamic downlink scenario. We study the relationship between secrecy capacity and harvested energy in a power-splitting configuration for a nonlinear energy-harvesting model under co-located conditions. The capacity maximization problem is formulated for the vehicle-to-vehicle communication scenario. The formulated problem is non-convex NP-hard, so we reformulate it into a convex form using a divide-and-conquer approach. We obtain the optimal transmit power matrix and power-splitting ratio values that guarantee positive values of the secrecy capacity. We analyze different vehicle-to-vehicle communication settings to validate the differentiation of the proposed algorithm in maintaining both reliability and security. We also substantiate the effectiveness of the proposed approach by analyzing the trade-offs between secrecy capacity and harvested energy. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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18 pages, 2889 KiB

Open AccessArticle

Outage Analysis of Unmanned-Aerial-Vehicle-Assisted Simultaneous Wireless Information and Power Transfer System for Industrial Emergency Applications

by Aleksandra Cvetković, Vesna Blagojević, Jelena Anastasov, Nenad T. Pavlović and Miloš Milošević

Sensors 2023, 23(18), 7779; https://doi.org/10.3390/s23187779 - 9 Sep 2023

Viewed by 1096

Abstract

In the scenario of a natural or human-induced disaster, traditional communication infrastructure is often disrupted or even completely unavailable, making the employment of emergency wireless networks highly important. In this paper, we consider an industrial Supervisory Control and Data Acquisition (SCADA) system assisted by an unmanned aerial vehicle (UAV) that restores connectivity from the master terminal unit (MTU) to the remote terminal unit (RTU). The UAV also provides power supply to the ground RTU, which transmits the signal to the end-user terminal (UT) using the harvested RF energy. The MTU-UAV and UAV-RTU channels are modeled through Nakagami-m fading, while the channel between the RTU and the UT is subject to Fisher–Snedecor composite fading. According to the channels’ characterization, the expression for evaluating the overall probability of outage events is derived. The impact of the UAV’s relative position to other terminals and the amount of harvested energy on the outage performance is investigated. In addition, the results obtained based on an independent simulation method are also provided to confirm the validity of the derived analytical results. The provided analysis shows that the position of the UAV that leads to the optimal outage system performance is highly dependent on the MTU’s output power. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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18 pages, 7387 KiB

Open AccessArticle

A High-Performance Circularly Polarized and Harmonic Rejection Rectenna for Electromagnetic Energy Harvesting

by Zaed S. A. Abdulwali, Ali H. Alqahtani, Yosef T. Aladadi, Majeed A. S. Alkanhal, Yahya M. Al-Moliki, Khaled Aljaloud and Mohammed Thamer Alresheedi

Sensors 2023, 23(18), 7725; https://doi.org/10.3390/s23187725 - 7 Sep 2023

Cited by 3 | Viewed by 1726

Abstract

This paper presents a novel circularly polarized rectenna designed for efficient electromagnetic energy harvesting at the 2.45 GHz ISM band. A compact antenna structure is designed to achieve high performance in terms of radiation efficiency, axial ratio, directivity, effective area, and harmonic rejection over the entire bandwidth of the ISM frequency band. The optimized rectifier circuit enhances the RF harvested energy efficiency, with an AC-to-DC conversion efficiency ranging from 36% to 70% for low-level input power ranging from −10 dBm to 0 dBm. The stable output of DC power confirms the suitability of this design for various practical applications, including wireless sensor networks, energy harvesting power supplies, medical implants, and environmental monitoring systems. Experimental validation, which includes both the reflection coefficient and radiation patterns of the designed antenna, confirms the accuracy of the simulation. The study found that the proposed energy harvesting system has a high total efficiency ranging from 53% to 63% and is well-suited for low-power energy harvesting (0 dBm) from ambient electromagnetic radiation. The proposed circularly polarized rectenna is a competitive option for efficient electromagnetic energy harvesting, both as a standalone unit and in an array, due to its high performance, feasibility, and versatility in meeting various energy harvesting requirements. This makes it a promising and cost-effective solution for various wireless communication applications, offering great potential for efficient energy harvesting from ambient electromagnetic radiation. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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27 pages, 9071 KiB

Open AccessArticle

Efficient Multi-Hop Wireless Power Transfer for the Indoor Environment

by Janis Eidaks, Romans Kusnins, Ruslans Babajans, Darja Cirjulina, Janis Semenjako and Anna Litvinenko

Sensors 2023, 23(17), 7367; https://doi.org/10.3390/s23177367 - 24 Aug 2023

Cited by 4 | Viewed by 1809

Abstract

With the rapid development of the Internet of Things (IoT) and wireless sensor networks (WSN), the modern world requires advanced solutions for the wireless powering of low-power autonomous devices. The present study addresses the wireless power transfer (WPT) efficiency problem by exploiting a multi-hop concept-based technique to increase the received power at the end sensor node (ESN). The current work adopts efficient multi-hop technology from the communications field to examine its impact on WPT performance. The investigation involves power transfer modeling and experimental measurements in a sub-GHz frequency range, chosen for being capable of providing a greater distance to transmit power. The paper proposes a multi-hop (MH) WPT concept based on signal amplification and demonstrates the fabricated multi-hop node (MHN) prototype. The experimental verification of the MHN is performed in the laboratory environment. The present paper examines two WPT scenarios: line-of-sight (LoS) and non-line-of-sight (NLoS). The turn-on angle of 90 degrees on MHN is used for the NLoS case. The received power and RF-DC converted voltage on the ESN are measured for all investigated scenarios. Moreover, the paper proposes an efficient simulation approach for the performance evaluation of MH WPT technology, providing an opportunity to analyze and optimize wireless sensor nodes’ spatial distribution to increase the received power. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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27 pages, 6046 KiB

Open AccessArticle

Performance Analysis of Wirelessly Powered Cognitive Radio Network with Statistical CSI and Random Mobility

by Nadica Kozić, Vesna Blagojević, Aleksandra Cvetković and Predrag Ivaniš

Sensors 2023, 23(9), 4518; https://doi.org/10.3390/s23094518 - 6 May 2023

Cited by 2 | Viewed by 1918

Abstract

The relentless expansion of communications services and applications in 5G networks and their further projected growth bring the challenge of necessary spectrum scarcity, a challenge which might be overcome using the concept of cognitive radio. Furthermore, an extremely high number of low-power devices are introduced by the concept of the Internet of Things (IoT), which also requires efficient energy usage and practically applicable device powering. Motivated by these facts, in this paper, we analyze a wirelessly powered underlay cognitive system based on a realistic case in which statistical channel state information (CSI) is available. In the system considered, the primary and the cognitive networks share the same spectrum band under the constraint of an interference threshold and a maximal tolerable outage permitted by the primary user. To adopt the system model in realistic IoT application scenarios in which network nodes are mobile, we consider the randomly moving cognitive user receiver. For the analyzed system, we derive the closed-form expressions for the outage probability, the outage capacity, and the ergodic capacity. The obtained analytical results are corroborated by an independent simulation method. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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15 pages, 379 KiB

Open AccessArticle

Performance Analysis of Wireless Communications with Nonlinear Energy Harvesting under Hardware Impairment and κ-μ Shadowed Fading

by Toi Le-Thanh and Khuong Ho-Van

Sensors 2023, 23(7), 3619; https://doi.org/10.3390/s23073619 - 30 Mar 2023

Cited by 6 | Viewed by 1709

Abstract

This paper improves energy efficiency and communications reliability for wireless transmission under

κ

μ

This paper improves energy efficiency and communications reliability for wireless transmission under

κ

μ

shadowed fading (i.e., integrating all channel impairments including path loss, shadowing, fading) and hardware impairment by employing a nonlinear energy harvester and multi-antenna power transmitter. To this end, this paper provides explicit formulas for outage probability. Numerous results corroborate these formulas and expose that energy-harvesting nonlinearity, hardware impairment, and channel conditions drastically deteriorate system performance. Notwithstanding, energy-harvesting nonlinearity influences system performance more severely than hardware impairment. In addition, desired system performance is accomplished flexibly and possibly by choosing a cluster of specifications. Remarkably, the proposed communications scheme obtains the optimal performance with the appropriate selection of the time-splitting factor. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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20 pages, 862 KiB

Open AccessArticle

Enabling Semantic-Functional Communications for Multiuser Event Transmissions via Wireless Power Transfer

by Pedro E. Gória Silva, Nicola Marchetti, Pedro H. J. Nardelli and Rausley A. A. de Souza

Sensors 2023, 23(5), 2707; https://doi.org/10.3390/s23052707 - 1 Mar 2023

Cited by 3 | Viewed by 1687

Abstract

A central concern for large-scale sensor networks and the Internet of Things (IoT) has been battery capacity and how to recharge it. Recent advances have pointed to a technique capable of collecting energy from radio frequency (RF) waves called radio frequency-based energy harvesting (RF-EH) as a solution for low-power networks where cables or even changing the battery is unfeasible. The technical literature addresses energy harvesting techniques as an isolated block by dealing with energy harvesting apart from the other aspects inherent to the transmitter and receiver. Thus, the energy spent on data transmission cannot be used together to charge the battery and decode information. As an extension to them, we propose here a method that enables the information to be recovered from the battery charge by designing a sensor network operating with a semanticfunctional communication framework. Moreover, we propose an event-driven sensor network in which batteries are recharged by applying the technique RF-EH. In order to evaluate system performance, we investigated event signaling, event detection, empty battery, and signaling success rates, as well as the Age of Information (AoI). We discuss how the main parameters are related to the system behavior based on a representative case study, also discussing the battery charge behavior. Numerical results corroborate the effectiveness of the proposed system. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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31 pages, 1694 KiB

Open AccessArticle

UAV-Based Servicing of IoT Nodes: Assessment of Ecological Impact

by Jarne Van Mulders, Jona Cappelle, Sarah Goossens, Lieven De Strycker and Liesbet Van der Perre

Sensors 2023, 23(4), 2291; https://doi.org/10.3390/s23042291 - 18 Feb 2023

Cited by 2 | Viewed by 2148

Abstract

Internet of Things (IoT) nodes get deployed for a variety of applications and often need to operate on batteries. This restricts their autonomy and/or can have a major ecological impact. The core idea of this paper is to use a unmanned aerial vehicle (UAV) to provide energy to IoT nodes, and hence prolong their autonomy. In particular, the objective is to perform a comparison of the total energy consumption resulting from UAV-based recharging or battery replacement versus full provisioning at install time or remote RF-based wireless power transfer. To that end, an energy consumption model for a small license-free UAV is derived, and expressions for system efficiencies are formulated. An exploration of design and deployment parameters is performed. Our assessment shows that UAV-based servicing of IoT nodes is by far more beneficial in terms of energy efficiency when nodes at distances further than a few meters are serviced, with the gap increasing to orders of magnitude with the distance. Our numerical results also show that battery swapping from an energy perspective outperforms recharging in the field, as the latter increases hovering time and the energy consumption related to that considerably. The ecological aspects of the proposed methods are further evaluated, e.g., considering toxic materials and e-waste. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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24 pages, 695 KiB

Open AccessArticle

Statistical Characterization of Wireless Power Transfer via Unmodulated Emission

by Sebastià Galmés

Sensors 2022, 22(20), 7828; https://doi.org/10.3390/s22207828 - 14 Oct 2022

Cited by 1 | Viewed by 1587

Abstract

In the past few years, the ability to transfer power wirelessly has experienced growing interest from the research community. Because the wireless channel is subject to a large number of random phenomena, a crucial aspect is the statistical characterization of the energy that can be harvested by a given device. For this characterization to be reliable, a powerful model of the propagation channel is necessary. The recently proposed generalized-K model has proven to be very useful, as it encompasses the effects of path loss, shadowing, and fast fading for a broad set of wireless scenarios, and because it is analytically tractable. Accordingly, the purpose of this paper is to characterize, from a statistical point of view, the energy harvested by a static device from an unmodulated carrier signal generated by a dedicated source, assuming that the wireless channel obeys the generalized-K propagation model. Specifically, by using simulation-validated analytical methods, this paper provides exact closed-form expressions for the average and variance of the energy harvested over an arbitrary time period. The derived formulation can be used to determine a power transfer plan that allows multiple or even massive numbers of low-power devices to operate continuously, as expected from future network scenarios such as the Internet of things or 5G/6G. Full article

(This article belongs to the Special Issue RF Energy Harvesting and Wireless Power Transfer for IoT)

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