Electrically Small Huygens Antenna-Based Fully-Integrated Wireless Power Transfer and Communication System

© 2013 IEEE. This paper introduces the first reported electrically small Huygens dual-functional wireless power transfer (WPT) and communication system operating in the 915-MHz ISM band. It is realized by the seamless combination of a Huygens linearly polarized (HLP) antenna and a highly efficient HLP rectenna. The configuration consists of two orthogonally oriented HLP subsystems. Each one intrinsically combines two pairs of metamaterial-inspired near-field resonant parasitic elements, i.e., an Egyptian axe dipole (EAD) and a capacitively loaded loop (CLL). Through the development of a very tightly coupled feed subsystem that includes the WPT mode's rectifier circuit and the communications mode's feedline while preserving their isolation, the independent operation of both functions is facilitated in an electrically small volume ( ka < 0.77 ). The measured results of its fabricated prototype agree well with their simulated values. The communications mode antenna resonates at 910 MHz and radiates a cardioid-shaped Huygens pattern with the peak gain of 2.7 dBi. The Huygens-based WPT rectenna achieves an 87.2% peak ac-to-dc conversion efficiency at 907 MHz. The dual-functional system is an ideal candidate for many emerging Internet-of-Things (IoT) wireless applications that require simultaneous wireless information and power transfer (SWIPT) and wirelessly powered communications (WPC)

RF Circuits and Systems Design and Technologies Enabling IoT Applications

Internet of Things (IoT) is the paradigm used nowadays to summarize what is expected form the fourth industrial revolution (Industry 4.0) that is the connectivity of a huge number of “smart” objects disseminated in dissimilar scenarios. This concept is foreseen for practically any possible application domain: from home to transportation, from industry plants to health care, and for space monitoring. Long-term and self-sustainability of these smart thinks (people, objects, tools, etc.) becomes the most relevant aspect for the implementation of such a complex vision. In this framework, my PhD activities have been concentrated. The common goal is to investigate advanced solutions for energy-aware systems and circuits cooperating to enable the IoT paradigm. In particular, I have studied, designed and experimentally demonstrated quite a few novel solutions able to overcome some of the energy limitations existing in IoT. The first project I have developed is an energy-autonomous power relay node at 2.45 GHz that is able to harvest energy from ambient-available or from dedicated RF sources and either use it for operating the node or for supplying power to other nodes. Both a hybrid and a monolithic implementation of the relay system have been implemented. Then I was dedicated to the design of a system enabling Wake-Up Radio (WuR) operation at ultra-low power. The ambitious goal of WuR radios is to reduce the communication power consumption in Wireless Sensor Networks (WSN) and IoT. With this scope in mind, I have proposed and implemented a multi-band WuR architecture. The flexibility of using frequency diversity in WuR enables a more reliable and robust communication channel. From the source side, analytical and experimental studies have been carried out to define the optimum Power Optimized Waveform (POW) excitation to push the WuR sensitivity down to power as low as -65 dBm

Dynamic Joint Scheduling of Anycast Transmission and Modulation in Hybrid Unicast-Multicast SWIPT-Based IoT Sensor Networks

The separate receiver architecture with a time- or power-splitting mode, widely used for simultaneous wireless information and power transfer (SWIPT), has a major drawback: Energy-intensive local oscillators and mixers need to be installed in the information decoding (ID) component to downconvert radio frequency (RF) signals to baseband signals, resulting in high energy consumption. As a solution to this challenge, an integrated receiver (IR) architecture has been proposed, and, in turn, various SWIPT modulation schemes compatible with the IR architecture have been developed. However, to the best of our knowledge, no research has been conducted on modulation scheduling in SWIPT-based IoT sensor networks while taking into account the IR architecture. Accordingly, in this paper, we address this research gap by studying the problem of joint scheduling for unicast/multicast, IoT sensor, and modulation (UMSM) in a time-slotted SWIPT-based IoT sensor network system. To this end, we leverage mathematical modeling and optimization techniques, such as the Lagrangian duality and stochastic optimization theory, to develop an UMSM scheduling algorithm that maximizes the weighted sum of average unicast service throughput and harvested energy of IoT sensors, while ensuring the minimum average throughput of both multicast and unicast, as well as the minimum average harvested energy of IoT sensors. Finally, we demonstrate through extensive simulations that our UMSM scheduling algorithm achieves superior energy harvesting (EH) and throughput performance while ensuring the satisfaction of specified constraints well.Comment: 29 pages, 13 figures (eps

Q-learning Channel Access Methods for Wireless Powered Internet of Things Networks

The Internet of Things (IoT) is becoming critical in our daily life. A key technology of interest in this thesis is Radio Frequency (RF) charging. The ability to charge devices wirelessly creates so called RF-energy harvesting IoT networks. In particular, there is a hybrid access point (HAP) that provides energy in an on-demand manner to RF-energy harvesting devices. These devices then collect data and transmit it to the HAP. In this respect, a key issue is ensuring devices have a high number of successful transmissions. There are a number of issues to consider when scheduling the transmissions of devices in the said network. First, the channel gain to/from devices varies over time. This means the efficiency to deliver energy to devices and to transmit the same amount of data is different over time. Second, during channel access, devices are not aware of the energy level of other devices nor whether they will transmit data. Third, devices have non-causal knowledge of their energy arrivals and channel gain information. Consequently, they do not know whether they should delay their transmissions in hope of better channel conditions or less contention in future time slots or doing so would result in energy overflow

RF Energy Harvesting Wireless Communication: RF Environment, Device Hardware and Practical Issues

Radio frequency (RF) based wireless power transfer provides an attractive solution to extend the lifetime of power-constrained wireless sensor networks. Through harvesting RF energy from surrounding environments or dedicated energy sources, low-power wireless devices can be self-sustaining and environment-friendly. These features make the RF energy harvesting wireless communication (RF-EHWC) technique attractive to a wide range of applications. The objective of this article is to investigate the latest research activities on the practical RF-EHWC design. The distribution of RF energy in the real environment, the hardware design of RF-EHWC devices and the practical issues in the implementation of RF-EHWC networks are discussed. At the end of this article, we introduce several interesting applications that exploit the RF-EHWC technology to provide smart healthcare services for animals, wirelessly charge the wearable devices, and implement 5G-assisted RF-EHWC

Integrated Data and Energy Communication Network: A Comprehensive Survey

OAPA In order to satisfy the power thirsty of communication devices in the imminent 5G era, wireless charging techniques have attracted much attention both from the academic and industrial communities. Although the inductive coupling and magnetic resonance based charging techniques are indeed capable of supplying energy in a wireless manner, they tend to restrict the freedom of movement. By contrast, RF signals are capable of supplying energy over distances, which are gradually inclining closer to our ultimate goal &#x2013; charging anytime and anywhere. Furthermore, transmitters capable of emitting RF signals have been widely deployed, such as TV towers, cellular base stations and Wi-Fi access points. This communication infrastructure may indeed be employed also for wireless energy transfer (WET). Therefore, no extra investment in dedicated WET infrastructure is required. However, allowing RF signal based WET may impair the wireless information transfer (WIT) operating in the same spectrum. Hence, it is crucial to coordinate and balance WET and WIT for simultaneous wireless information and power transfer (SWIPT), which evolves to Integrated Data and Energy communication Networks (IDENs). To this end, a ubiquitous IDEN architecture is introduced by summarising its natural heterogeneity and by synthesising a diverse range of integrated WET and WIT scenarios. Then the inherent relationship between WET and WIT is revealed from an information theoretical perspective, which is followed by the critical appraisal of the hardware enabling techniques extracting energy from RF signals. Furthermore, the transceiver design, resource allocation and user scheduling as well as networking aspects are elaborated on. In a nutshell, this treatise can be used as a handbook for researchers and engineers, who are interested in enriching their knowledge base of IDENs and in putting this vision into practice

Extending Wireless Powered Communication Networks for Future Internet of Things

Energy limitation has always been a major concern for long-term operation of wireless networks. With today's exponential growth of wireless technologies and the rapid movement towards the so-called Internet of Things (IoT), the need for a reliable energy supply is more tangible than ever. Recently, energy harvesting has gained considerable attention in research communities as a sustainable solution for prolonging the lifetime of wireless networks. Beside conventional energy harvesting sources such as solar, wind, vibration, etc. harvesting energy from radio frequency (RF) signals has drawn significant research interest in recent years as a promising way to overcome the energy bottleneck. Lately, the integration of RF energy transfer with wireless communication networks has led to the emergence of an interesting research area, namely, wireless powered communication network (WPCN), where network users are powered by a hybrid access point (HAP) which transfers wireless energy to the users in addition to serving the functionalities of a conventional access point. The primary aim of this thesis is to extend the baseline model of WPCN to a dual-hop WPCN (DH-WPCN) in which a number of energy-limited relays are in charge of assisting the information exchange between energy-stable users and the HAP. Unlike most of the existing research in this area which has merely focused on designing methods and protocols for uplink communication, we study both uplink and downlink information transmission in the DH-WPCN. We investigate sum-throughput maximization problems in both directions and propose algorithms for optimizing the values of the related parameters. We also tackle the doubly near-far problem which occurs due to unequal distance of the relays from the HAP by proposing a fairness enhancement algorithm which guarantees throughput fairness among all users

Analysis and Exploitation of Multiple Antennas Interaction in the Near-Field

This thesis is structured in two parts. The former, and main one, introduces a novel solution for portable devices to exploit their existing communication antennas for bi-directional near-field wireless re-charging, without compromising their far-field properties. To demonstrate the concept, the GSM 900/1800MHz and the 433MHz, bands are adopted for the far-field communication and for the near-field wireless recharging, respectively. Starting with a full-wave analysis of two identical printed dipoles faced at several distances, then each antenna is fed by a frequency-selective three-port network in order to simultaneously ensure data communication at the higher frequency bands and wireless re-charging at the lower frequency band. As a proof-of-concept a system prototype is built. Port insulation, RF-to-RF and RF-to-DC power efficiency measurements demonstrates that a wireless charging and communication it is possible with the proposed link arrangement and it can thus be used to exploit the charged state of an available device to recharge another one, without limiting the respective communication capabilities. The latter part focuses on a fast design method for an RFID antenna, used as a transducer, to realize an RFID bent sensor tag. The method exploits a space mapping technique, using a coarse circuit model (CM) and a fine electromagnetic model (EM). The CM represents, in a CPU-time efficient way, the antenna transducer states to fast evaluate the sensor tag efficiency. The EM model is then used to verify the sensing states and to rapidly prototype the antenna. To demonstrate the procedure, the corresponding EM-based and CM input impedances of a T-matched dipole are compared for several sensing states over a frequency band of 840-890MHz. An innovative Figure of Merit has been. Finally the sensor tag efficiency is computed to compare the CM results with respect to the EM ones and in order to validate the entire space mapping technique

UAV-aided data and energy integrated network: System design and prototype development

Terminal devices deployed in outdoor environments are facing a thorny problem of power supply. Data and energy integrated network (DEIN) is a promising technology to solve the problem, which simultaneously transfers data and energy through radio frequency signals. State-of-the-art researches mostly focus on theoretical aspects. By contrast, we provide a complete design and implementation of a fully functioning DEIN system with the support of an unmanned aerial vehicle (UAV). The UAV can be dispatched to areas of interest to remotely recharge batteryless terminals, while collecting essential information from them. Then, the UAV uploads the information to remote base stations. Our system verifies the feasibility of the DEIN in practical applications