Wireless Information And Power Transfer Research Articles

Design of Integrated Simultaneous Information and Power Receiver for WIPT Application

This letter presents the design and fabrication of a multifunctional simultaneous information and power receiver (SIPR) considering a multitone time-modulated array as wireless information and power transfer (WIPT). The proposed SIPR with Wilkinson power divider delivers power to information processing and DC generating blocks. The fabricated SIPR receives information in horizontal and vertical polarizations. A voltage-doubler-type rectifying circuit is designed for DC generation with a microstrip line model for the lumped parameter. DC generating block generates a maximum of 76% RF to DC power conversion. Furthermore, the bit error rate (BER) performance graph supports the use of the receiver for the digital modulation schemes.

Wireless Information and Power Transfer: A Bottom-Up Multi-Layer Design Framework

The efficiency of wireless information and power transfer (WIPT) systems requires an essential reevaluation and rethinking of the entire transceiver chain, which is characterized by a bottom-up multi-layer design approach. In this article, we introduce and describe the key design layers: “Mathematical modeling,” associated with the investigation of mathematical models for the wireless power transfer process, “Information-theoretic limits,” which refers to the fundamental limits of the WIPT channel, “Link design,” corresponding to signal processing techniques that make WIPT feasible, “System-level perspective,” which studies the developed WIPT techniques from a macroscopic system-level point-of-view, and “Experimental studies,” that refers to real-world implementation of WIPT systems. These layers are well-connected and their interplay is imperative for the effective design of WIPT systems. Specific case studies are discussed, which demonstrates the interdisciplinary nature of the aforementioned multi-layer design framework.

Foundations of Wireless Information and Power Transfer: Theory, Prototypes, and Experiments

As wireless has disrupted communications, wireless will also disrupt the delivery of energy. Future wireless networks will be equipped with (radiative) wireless power transfer (WPT) capability and exploit radio waves to carry both energy and information through a unified wireless information and power transfer (WIPT). Such networks will make the best use of the RF spectrum and radiation as well as the network infrastructure for the dual purpose of communicating and energizing. Consequently those networks will enable trillions of future low-power devices to sense, compute, connect, and energize anywhere, anytime, and on the move. In this paper, we review the foundations of such future system. We first give an overview of the fundamental theoretical building blocks of WPT and WIPT. Then we discuss some state-of-the-art experimental setups and prototypes of both WPT and WIPT and contrast theoretical and experimental results. We draw a special attention to how the integration of RF, signal and system designs in WPT and WIPT leads to new theoretical and experimental design challenges for both microwave and communication engineers and highlight some promising solutions. Topics and experimental testbeds discussed include closed-loop WPT and WIPT architectures with beamforming, waveform, channel acquisition, and single/multi-antenna energy harvester, centralized and distributed WPT, reconfigurable metasurfaces and intelligent surfaces for WPT, transmitter and receiver architecture for WIPT, modulation, rate-energy trade-off. Moreover, we highlight important theoretical and experimental research directions to be addressed for WPT and WIPT to become a foundational technology of future wireless networks.

Evolution of SWIPT for the IoT World: Near- and Far-Field Solutions for Simultaneous Wireless Information and Power Transfer

In the past few years, many interesting approaches have been studied and designed to advance the practical implementation of wireless information and power transfer (WIPT) <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> and simultaneous WIPT (SWIPT) <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> , <xref ref-type="bibr" rid="ref3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[3]</xref> in the contexts of everyday life, academic research, and industry. The ever-growing array of Internet of Things (IoT) technologies presents a tangible answer to the need for modern, densely populated networks of wirelessly connected devices. In this context, node maintenance is a challenging task, given both the enormous size of the networks and the location of the devices, which can be spread across difficult-to-reach areas. In particular, the SWIPT paradigm <xref ref-type="bibr" rid="ref4" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[4]</xref> is being investigated in a wide range of systems for industrial applications combined with emerging technologies typical of the industrial IoT, namely wireless sensor networks (WSNs) that enable unlimited and uninterrupted connectivity in generic commercial environments. The main goal is to continuously monitor key components by using smart sensors that are able to track, in almost real time, rotation, position, speed, temperature, acceleration, and all the other vital parameters of the devices that have to be observed <xref ref-type="bibr" rid="ref5" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[5]</xref> .

Guest Editoral Signal Processing Advances in Wireless Transmission of Information and Power

The papers in this special section focuses on signal processing advances in wireless transmission of power and information. Wireless power transfer (WPT) and wireless information and power transfer (WIPT) have received growing attention in the research community in the past few years. In this special issue, a total of fourteen papers present state-of-the-art results in the broad area of wireless transmission of information and power with a special emphasis on signal processing advances. The special issue starts with a guest editor-authored tutorial overview paper that reviews the signal processing, machine learning, sensing, and computing techniques, challenges and opportunities in future networks based on WPT and WIPT.

Wireless Power Transfer for Future Networks: Signal Processing, Machine Learning, Computing, and Sensing

Wireless power transfer (WPT) is an emerging paradigm that will enable using wireless to its full potential in future networks, not only to convey information but also to deliver energy. Such networks will enable trillions of future low-power devices to sense, compute, connect, and energize anywhere, anytime, and on the move. The design of such future networks brings new challenges and opportunities for signal processing, machine learning, sensing, and computing. The objective is to make the best use of the RF radiations, spectrum, and network infrastructure to provide cost-effective and real-time power supplies to wireless devices and enable wireless-powered applications. In this paper, we first review recent signal processing techniques to make WPT and wireless information and power transfer (WIPT) as efficient as possible. Topics include high-power amplifier and energy harvester nonlinearities, active and passive beamforming, intelligent reflecting surfaces, receive combining with multi-antenna harvester, modulation, coding, waveform, large-scale (massive) multiple-input multiple-output (MIMO), channel acquisition, transmit diversity, multi-user power region characterization, coordinated multipoint, and distributed antenna systems. Then, we overview two different design methodologies: the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">model and optimize</i> approach relying on analytical system models, modern convex optimization, and communication/information theory, and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">learning</i> approach based on data-driven end-to-end learning and physics-based learning. We discuss the pros and cons of each approach, especially when accounting for various nonlinearities in wireless-powered networks, and identify interesting emerging opportunities for the approaches to complement each other. Finally, we identify new emerging wireless technologies where WPT may play a key role—wireless-powered mobile edge computing, wireless-powered sensing, and wireless-powered federated learning—arguing WPT, communication, computation, sensing, and learning must be jointly designed.

Measurements and Characterization of a Newly Developed Novel Miniature WIPT System

This article reports, for the first time, the design and experimental evaluation of a compact wireless information and power transfer (WIPT) system operating at radio frequency (RF). The design of WIPT system is facilitated by the development of a novel tri-band defected ground structure (DGS) based bandstop filter (BSF) operating at three different frequencies of 300, 433, and 700 MHz. Then, two similar BSFs are arranged in a back-to-back configuration to achieve near-field resonant inductive coupling for transfer of information and power. The measurement carried out on a prototyped system shows an excellent agreement between the measured and simulation results and provides power transfer efficiencies of 70.1%, 66%, and 65% at 300, 433, and 700 MHz, respectively, at a separation distance of 23 mm. These figures are a significant advancement over the existing state of the art. Furthermore, up-link and down-link of data transfer at 433 and 700 MHz are demonstrated using universal software radio peripheral (USRP), and power transfer is shown by illuminating a light emitting diode (LED) at 300 MHz.

Radio Frequency Identification and Sensing Techniques and Their Applications-A Review of the State-of-the-Art.

Radio Frequency Identification (RFID) sensors, integrating the features of Wireless Information and Power Transfer (WIPT), object identification and energy efficient sensing capabilities, have been considered a new paradigm of sensing and communication for the futuristic information systems. RFID sensor tags featuring contactless sensing, wireless information transfer, wireless powered, light weight, non-line-of-sight transmission, flexible and pasteable are a critical enabling technology for future Internet-of-Things (IoT) applications, such as manufacturing, logistics, healthcare, agriculture and food. They have attracted numerous research efforts due to their innovative potential in the various application fields. However, there has been a gap between the in-lab investigations and the practical IoT application scenarios, which has motivated this survey of this research to identify the promising enabling techniques and the underlying challenges. This study aims to provide an exhaustive review on the state-of-art RFID sensor technologies from the system implementation perspective by focusing on the fundamental RF energy harvesting theories, the recent technical progresses and commercial solutions, innovative applications and some RFID sensor based IoT solutions, identify the underlying technological challenges at the time being, and give the future research trends and promising application fields in the rich sensing applications of the forthcoming IoT era.

Switching Frequency Techniques for Universal Ambient Backscatter Networking

This work offers both analog and digital tag modulation schemes and respective receiver designs, for ultra-low power, high performance, ambient backscatter communications. All proposed techniques are based on simple, but careful, switching frequency control at the tag, allowing for the easy frequency-domain multiple access. First, a digital modulation scheme is offered, namely pseudo-frequency shift keying, assuming illumination from constant envelope-modulated signals and a fully coherent detector is derived along with closed-form probability of error. A second digital modulation scheme is also offered, based on a frequency-shifted form of binary phase shift keying (S-BPSK), relaxing the constant-envelope requirement for the illuminator and an illumination-agnostic detector is derived. Based on S-BPSK, short packet error correction coding is utilized for ambient backscatter communication, for the first time in the literature. It is shown that the proposed coded scheme under modulated ambient signal illumination & wireless channel variation, offers tremendous performance gains, i.e., modulation of the ambient signal is helpful. Finally, a third, purely analog, modulation scheme is analyzed, based on FM remodulation principles. A low-cost tag is implemented, demonstrating tag-to-receiver ranges up to 26 meters outdoors, power consumption of 24 μWatts in continuous operation, able to be interrogated by any conventional frequency modulation (FM) receiver. The proposed techniques cover a large variety of omnipresent wireless industry systems, enabling universal ambient backscatter and relevant wireless information and power transfer (WIPT) applications.

Resource Allocation for Wireless Power Transmission Over Full-Duplex OFDMA/NOMA Mobile Wireless Networks

The current wireless networks have been designed solely for data communication purposes, imposing many new challenges when supporting both power and information transmissions simultaneously. One of these main challenges lies in resource allocations. To overcome these difficulties, we propose the resource allocation schemes to efficiently support wireless power transmission over a relay-assisted full-duplex (FD) wireless network, where the access point (AP) conducts wireless information and power transfer (WIPT) to multiple mobile users in the downlink (DL), and in the meantime, mobile users transmit information to the AP via relays' assistances in the uplink (UL). Under DL WIPT, each mobile user uses the power splitting technique to harvest energy and receive data simultaneously. Aiming at maximizing the minimum (max-min) sum of DL and UL transmit rates among all mobile users, our proposed schemes jointly optimize the allocation of subcarriers and powers, and the selection of relays and power splitting ratios. Also, our proposed schemes consider two scenarios, where the network employs either orthogonal frequency-division multiple access (OFDMA) or non-orthogonal multiple access (NOMA) taking into account both perfect channel state information (CSI) estimation and imperfect CSI estimation cases. We first approximate the formulated non-convex max-min optimization problems as convex optimization problems. Then, we develop an asymptotically optimal algorithm and a suboptimal algorithm for OFDMA case and NOMA case, respectively. Finally, we validate and evaluate the performances of our proposed schemes through numerical analyses.

Retrodirective Frequency Diverse Array Focusing for Wireless Information and Power Transfer

Simultaneous wireless information and power transfer (WIPT) has so far mainly relied on a phased-array antenna, but only angle-focusing capability without range focusing can be achieved for phased-array antennas. In this paper, we depart from the phased-array antenna and propose the use of retrodirective frequency diverse array (FDA) focusing in base station for long-range WIPT applications. In the retrodirective FDA focusing, an additional small frequency offset is added across the phase-conjugating mixers in the retrodirective array to produce both range-dimension and angle-dimension focused beamforming for energy-efficient WIPT. The FDA beampattern is decoupled in range-angle dimension and can be independently controlled through properly designing the transmit weighting vector or frequency offsets. More importantly, the proposed WIPT scheme allows self-tracking the direction-of-arrival of the pilot signals without requirement of any a priori knowledge. A maximum efficiency optimization approach based on discrete prolate spheroidal sequence is also proposed for the beampattern synthesis. In addition, robust physical-layer security can be obtained by utilizing FDA angle-range-time-dependent beampattern characteristics. The harvested energy, achievable bit rate, and achievable secrecy rate at the user receivers are derived for the WIPT, along with extensive numerical results. Both the theoretical analysis and numerical results verify the superiority of FDA over phased array in energy efficiency and security for WIPT applications.

Discussion on Applying Wireless Information and Power Transfer to Relay Networks

Recently, there have been numerous research works on applying wireless information and power transfer (WIPT) to relay networks. In this letter, we first include the path-loss effect in the performance evaluation of WIPT-based relay networks. Results reveal that the received signal quality of these networks is generally much worse than that of direct transmission due to the enlarged path loss, and then a large amount of energy must be harvested at the relay node before the actual information-forwarding process. Based on this observation, we also show that suitably employing multiple energy-harvested relays can help in overcoming the unfavorably large path loss induced, and therefore let WIPT-based relaying become rational for practical implementation.

Optimizing the Energy and Throughput of a Water-Quality Monitoring System.

This work presents a new approach to the maximization of energy and throughput in a wireless sensor network (WSN), with the intention of applying the approach to water-quality monitoring. Water-quality monitoring using WSN technology has become an interesting research area. Energy scarcity is a critical issue that plagues the widespread deployment of WSN systems. Different power supplies, harvesting energy from sustainable sources, have been explored. However, when energy-efficient models are not put in place, energy harvesting based WSN systems may experience an unstable energy supply, resulting in an interruption in communication, and low system throughput. To alleviate these problems, this paper presents the joint maximization of the energy harvested by sensor nodes and their information-transmission rate using a sum-throughput technique. A wireless information and power transfer (WIPT) method is considered by harvesting energy from dedicated radio frequency sources. Due to the doubly near–far condition that confronts WIPT systems, a new WIPT system is proposed to improve the fairness of resource utilization in the network. Numerical simulation results are presented to validate the mathematical formulations for the optimization problem, which maximize the energy harvested and the overall throughput rate. Defining the performance metrics of achievable throughput and fairness in resource sharing, the proposed WIPT system outperforms an existing state-of-the-art WIPT system, with the comparison based on numerical simulations of both systems. The improved energy efficiency of the proposed WIPT system contributes to addressing the problem of energy scarcity.

Wireless Information and Power Transfer: Nonlinearity, Waveform Design, and Rate-Energy Tradeoff

The design of wireless information and power transfer (WIPT) has so far relied on an oversimplified and inaccurate linear model of the energy harvester. In this paper, we depart from this linear model and design WIPT considering the rectifier nonlinearity. We develop a tractable model of the rectifier nonlinearity that is flexible enough to cope with general multicarrier modulated input waveforms. Leveraging that model, we motivate and introduce a novel WIPT architecture relying on the superposition of multicarrier unmodulated and modulated waveforms at the transmitter. The superposed WIPT waveforms are optimized as a function of the channel state information so as to characterize the rate-energy region of the whole system. Analysis and numerical results illustrate the performance of the derived waveforms and WIPT architecture and highlight that nonlinearity radically changes the design of WIPT. We make key and refreshing observations. First, analysis (confirmed by circuit simulations) shows that modulated and unmodulated waveforms are not equally suitable for wireless power delivery, namely, modulation being beneficial in single-carrier transmissions but detrimental in multicarrier transmissions. Second, a multicarrier unmodulated waveform (superposed to a multicarrier modulated waveform) is useful to enlarge the rate-energy region of WIPT. Third, a combination of power splitting and time sharing is in general the best strategy. Fourth, a nonzero mean Gaussian input distribution outperforms the conventional capacity-achieving zero-mean Gaussian input distribution in multicarrier transmissions. Fifth, the rectifier nonlinearity is beneficial to system performance and is essential to efficient WIPT design.

Exploiting Interference for Secrecy Wireless Information and Power Transfer

RF signals enabled wireless information and power transfer (WIPT) is a cost-effective technique to achieve two-way communications and at the same time provide energy supplies for low-power wireless devices. However, the information transmission in WIPT is vulnerable to eavesdropping by energy receivers. To achieve secrecy communications with information nodes while satisfying the energy transfer requirement of energy receivers, an efficient solution is to exploit dual use of the energy signals also as useful interference or artificial noise to interfere with the energy receivers, thus preventing their potential information eavesdropping. Toward this end, this article provides an overview on the joint design of energy and information signals to achieve energy-efficient and secure WIPT under various practical setups, including simultaneous WIPT, wireless powered cooperative relaying and jamming, and wireless powered communication networks. We also present some research directions that are worth pursuing in the future.

Full-duplex distributed switch-and-stay networks with wireless energy harvesting: design and outage analysis

Distributed switch and stay combining (DSSC) has been considered as an effective technique to achieve spatial diversity in a distributed manner with low processing complexity. In this paper, we incorporate DSSC into a full-duplex dual hop relaying system, where two energy-constrained relay nodes assist the information transmission from the source to the destination using energy wirelessly harvested from the source. By applying DSSC at the destination, this efficient technique not only improves performance of full-duplex relaying systems and increases the system diversity but also reduces the implementation and hardware complexity at the destination. We obtain tight approximate expression for outage probability in the case of using decode-and-forward (DF) relaying protocol and analytical expression for outage probability in the case of using amplify-and-forward (AF) relaying protocol. Numerical results show that our DSSC full-duplex relaying with wireless information and power transfer (WIPT) system achieves the full spatial diversity and has a better performance in terms of outage probability than that of the DSSC half-duplex relaying and conventional full-duplex relaying with WIPT system.

Beamforming Design for Wireless Information and Power Transfer Systems: Receive Power-Splitting Versus Transmit Time-Switching

Information and energy can be transferred over the same radio-frequency channel. In the power-splitting (PS) mode, they are simultaneously transmitted using the same signal by the base station (BS) and later separated at the user (UE)'s receiver by a power splitter. In the time-switching (TS) mode, they are either transmitted separately in time by the BS or received separately in time by the UE. In this paper, the BS transmit beamformers are jointly designed with either the receive PS ratios or the transmit TS ratios in a multicell network that implements wireless information and power transfer (WIPT). Imposing UE-harvested energy constraints, the design objectives include: 1) maximizing the minimum UE rate under the BS transmit power constraint, and 2) minimizing the maximum BS transmit power under the UE data rate constraint. New iterative algorithms of low computational complexity are proposed to efficiently solve the formulated difficult nonconvex optimization problems, where each iteration either solves one simple convex quadratic program or one simple second-order-cone-program. Simulation results show that these algorithms converge quickly after only a few iterations. Notably, the transmit TS-based WIPT system is not only more easily implemented but outperforms the receive PS-based WIPT system as it better exploits the beamforming design at the transmitter side.

Secrecy wireless information and power transfer: challenges and opportunities

Wireless information and power transfer (WIPT) enables more sustainable and resilient communications owing to the fact that it avoids frequent battery charging and replacement. However, it also suffers from possible information interception due to the open nature of wireless channels. Compared to traditional secure communications, secrecy wireless information and power transfer (SWIPT) carries several distinct characteristics. On one hand, wireless power transfer may increase the vulnerability of eavesdropping, since a power receiver, as a potential eavesdropper, usually has a shorter access distance than an information receiver. On the other hand, wireless power transfer can be exploited to enhance wireless security. This article reviews the security issues in various SWIPT scenarios, with an emphasis on revealing the corresponding challenges and opportunities for implementing SWIPT. Furthermore, we provide a survey on a variety of physical layer security techniques to improve secrecy performance. In particular, we propose to use massive multiple-input multiple-output (MIMO) techniques to enhance power transfer efficiency and secure information transmission simultaneously. Finally, we discuss several potential research directions to further enhance the security in SWIPT systems.

Enhancing wireless information and power transfer by exploiting multi-antenna techniques

This article reviews an emerging wireless information and power transfer (WIPT) technique with an emphasis on its performance enhancement employing multi-antenna techniques. Compared to traditional wireless information transmission, WIPT faces numerous challenges. First, it is more susceptible to channel fading and path loss, resulting in a much shorter power transfer distance. Second, it gives rise to the issue of how to balance spectral efficiency for information transmission and energy efficiency for power transfer in order to obtain an optimal tradeoff. Third, there exists a security issue for information transmission in order to improve power transfer efficiency. In this context, multi-antenna techniques, e.g. energy beamforming, are introduced to solve these problems by exploiting spatial degree of freedom. This article provides a tutorial on various aspects of multi-antenna based WIPT techniques, with a focus on tackling the challenges by parameter optimization and protocol design. In particular, we investigate the WIPT tradeoffs based on two typical multi-antenna techniques: the limited feedback multi-antenna technique for short-distance transfer; and the large-scale multiple-input multiple-output (LS-MIMO, also known as massive MIMO) technique for long-distance transfer. Finally, simulation results validate the effectiveness of the proposed schemes.