Simultaneous Wireless Information And Power Transfer Scheme Research Articles

A novel resource allocation scheme for full-duplex NOMA systems with power splitting-based SWIPT

This paper introduces novel resource allocation (RA) algorithms for optimizing wireless network performance, focusing on a full-duplex (FD) base station (BS) employing non-orthogonal multiple access (NOMA) technology. Motivated by the intriguing trade-off introduced by the simultaneous wireless information and power transfer (SWIPT) scheme, in which achievable data rates are sacrificed to enhance harvested energy, this study aims to quantify the delicate equilibrium between two vital aspects meticulously: the overall achievable data rate facilitated by NOMA and FD technologies and the energy harvested via the SWIPT approach. Specifically, our focus is on jointly optimizing the enhancement of both data rate and harvested energy for downlink (DL) users where a multi-objective optimization approach is developed in the proposed RA algorithm to study the existing trade-off between these conflicting objective functions. This problem optimizes the power allocation for both the BS and the users, allocating subcarriers, and optimizing the power splitting factor for SWIPT scheme. We developed efficient iterative solutions for the intended RA problems because they involve complex mixed-integer nonlinear optimization challenges that are generally difficult to solve. The effectiveness of the proposed RA framework is demonstrated using simulation results. These results investigate whether FD MC-NOMA systems, enabled by the proposed RA algorithms, provide a significant increase in system throughput compared to both conventional half-duplex (HD) multicarrier orthogonal multiple access (MC-OMA) systems and HD MC-NOMA systems, as well as other baseline methods. The results also demonstrate that our proposed scheme allows for a greater power harvest than the OMA-FD configuration and other baseline schemes.

Resonant Beam SWIPT With Telescope and Second Harmonic

Simultaneous wireless information and power transfer (SWIPT) is a prospective technology that can handle the energy consumption and communication requirements in the Internet of Things. Resonant beam SWIPT (RB-SWIPT) scheme utilizes narrow optical beam as carrier and with spatially separated resonator structure, which can support high power and high rate SWIPT for mobile devices. However, the performance of original RB-SWIPT systems is limited by returning beam interference and transmission loss. In this paper, we propose a RB-SWIPT scheme for transmission-enhanced and anti-interference. The telescope internal modulator (TIM) and second harmonic generator (SHG) are adopted in the proposed system. The TIM can compress beams to reduce the transmission loss. The SHG can generate frequency-doubled beams to avoid interference. To evaluate the proposed system, we establish mathematical models to depict the beam transmission, energy conversion, electric power output and data receiving. Numerical results illustrate that the proposed system can achieve 18 bit/s/Hz spectral efficiency and deliver 8 W power over 100 m distance.

Performance evaluation of cooperative‐nonorthogonal multiple access‐based improved hybrid simultaneous wireless information and power transfer protocol

AbstractThe integration of cooperative nonorthogonal multiple access (CNOMA) and the improved hybrid simultaneous wireless information and power transfer (SWIPT) (IHS) protocol (termed the CNOMA‐IHS scheme) is proposed in this article. The proposed CNOMA‐IHS scheme performs the energy harvesting to energize the cooperative relay operation from cell center user to cell edge user and also convey information to the users as well. Moreover, the proposed scheme also conveys multiple different symbols to the users to improve the user channel capacities, ergodic sum capacity (ESC), and energy efficiency (EE). Finally, the analytical and simulation results illustrated the proposed scheme outperforms the existing CNOMA based SWIPT schemes as well as orthogonal multiple access based IHS scheme in terms of ESC and EE.

Performance Tradeoff Analysis of Hybrid Signaling SWIPT Systems with Nonlinear Power Amplifiers

Simultaneous wireless information and power transfer (SWIPT) is a promising technology to achieve wide-area energy transfer by sharing the same radio frequency (RF) signal and infrastructure of legacy wireless communication systems. To enlarge the effective range of energy transfer in practice, it is desirable to have a hybrid signaling SWIPT scheme, which combines a high-power multitone energy signal with a low-power broadband information signal. This paper presents a systematic study on the performance of hybrid signaling SWIPT systems with memoryless nonlinear transmitter power amplifiers (PAs). Using PA efficiency and signal-to-noise-and-distortion ratio (SNDR) as the metrics to measure the efficiency of energy transfer and information transmission, respectively, we derive the tradeoff between these two metrics for two PA classes, two nonlinear PA models, and two SNDR definitions. Our results reveal insights into the fundamental performance tradeoff inherent in SWIPT systems using hybrid signaling schemes.

Performance Analysis and Optimization of Bidirectional Overlay Cognitive Radio Networks With Hybrid-SWIPT

This paper considers a cooperative cognitive radio network with two primary users (PUs) and two secondary users (SUs) that enables two-way communications of primary and secondary systems in conjunction with non-linear energy harvesting based simultaneous wireless information and power transfer (SWIPT). With the considered network, SUs are able to realize their communications over the licensed spectrum while extending relay assistance to the PUs. The overall bidirectional end-to-end transmission takes place in four phases, which include both energy harvesting (EH) and information transfer. A non-linear energy harvester with a hybrid SWIPT scheme is adopted in which both power-splitting and time-switching EH techniques are used. The SUs aid in relay cooperation by performing an amplify-and-forward operation, whereas selection combining technique is adopted at the PUs to extract the intended signal from multiple received signals broadcasted by the SUs. Accurate outage probability expressions for the primary and secondary links are derived under the Nakagami-$m$ fading environment. Further, the system behavior is analyzed with respect to achievable system throughput and energy efficiency. Since the performance of the considered system is strongly affected by the spectrum sharing factor and hybrid SWIPT parameters, particle swarm optimization is implemented to optimize the system parameters so as to maximize the system throughput and energy efficiency. Simulation results are provided to corroborate the performance analysis and give useful insights into the system behavior concerning various system/channel parameters.

On the ergodic capacities of decode‐and‐forward MIMO relay network with simultaneous wireless information and power transfer

AbstractIn this article, simultaneous wireless information and power transfer (SWIPT) has been studied for point‐to‐point decode‐and‐forward (DF) based multiple‐input‐multiple‐output (MIMO) relay network with an energy‐constrained relay. This relay is capable of harvesting energy from the wireless signals received from the source terminal. In particular, three different SWIPT schemes, that is, time switching, power splitting, and antenna switching are considered for EH at relay. New closed‐form approximations for the sum ergodic capacity of a DF MIMO relay network have been derived with spatial multiplexing at source, zero‐forcing receivers at relay and destination. Based on the sum capacity approximations, optimal splitting coefficients for aforementioned SWIPT schemes that maximize the sum capacity are presented. Moreover, the impact of system parameters on these optimal coefficients has been studied. In addition to this, first optimization problems for the number of antennas at relay have been formulated and then these problems are transformed into concave form by relaxing constraints to be defined over positive real numbers instead of taking only discrete values. New closed‐form solutions for the optimum number of antennas at relay have been derived. Furthermore, new closed‐form approximations for the ergodic capacities in the presence of an external co‐channel interference are also presented. Numerical results show that approximations for the sum capacity match well with the exact ones obtained through Monte‐Carlo simulations, particularly when the channel hardening effect kicks in, that is, for large degrees of freedom. Finally, the solutions for the optimization problems have also been validated by the numerical examples.

Simultaneous Wireless Information and Power Transfer (SWIPT) for Internet of Things: Novel Receiver Design and Experimental Validation

In this article, we propose a novel simultaneous wireless information and power transfer (SWIPT) scheme for the Internet of Things (IoT). Different from the conventional power splitting (PS) and time switching (TS) schemes, the proposed scheme sends the wireless power via the unmodulated high-power continuous wave (CW) and transmits information by using a small modulated signal in order to reduce the interference and to enhance the power amplifier efficiency. We design a receiver circuit for processing such SWIPT signals, which is designed with the aim of minimizing the circuit complexity and power consumption for information decoding. This goal is achieved by first rectifying the received signal and then splitting the power and information signals. We analyze the proposed receiver circuit and derive the closed-form expression for the energy harvesting efficiency and the frequency response of the communication signal. We have implemented the proposed receiver circuit and built the real-time testbed for experimenting with simultaneous transmission of information and power. By experiments, we have verified the correctness of the receiver circuit analysis and shown the validity of the proposed SWIPT scheme.

Robust Beamforming Design for SWIPT-Based Multi-Radio Wireless Mesh Network with Cooperative Jamming

Wireless mesh networks (WMNs) can provide flexible wireless connections in a smart city, internet of things (IoT), and device-to-device (D2D) communications. The performance of WMNs can be greatly enhanced by adopting a multi-radio technique, which enables a node to communicate with more nodes simultaneously. However, multi-radio WMNs face two main challenges, namely, energy consumption and physical layer secrecy. In this paper, both simultaneous wireless information and power transfer (SWIPT) and cooperative jamming technologies were adopted to overcome these two problems. We designed the SWIPT and cooperative jamming scheme, minimizing the total transmission power by properly selecting beamforming vectors of the WMN nodes and jammer to satisfy the individual signal-to-interference-plus-noise ratio (SINR) and energy harvesting (EH) constrains. Especially, we considered the channel estimate error caused by the imperfect channel state information. The SINR of eavesdropper (Eve) was suppressed to protect the secrecy of WMN nodes. Due to the fractional form, the problem was proved to be non-convex. We developed a tractable algorithm by transforming it into a convex one, utilizing semi-definite programming (SDP) relaxation and S-procedure methods. The simulation results validated the effectiveness of the proposed algorithm compared with the non-robust design.

Novel Frequency-Splitting SWIPT for Overcoming Amplifier Nonlinearity

In this letter, we propose a novel simultaneous wireless information and power transfer (SWIPT) scheme, namely the frequency-splitting (FS) SWIPT, which separates the power and data signals in the frequency domain. The proposed FS SWIPT scheme is advantageous in that it can maximize the efficiency of the high power amplifier (HPA) in the transmitter and reduce the harmonic distortion caused by the nonlinearity of the HPA. We design a receiver circuit for the FS SWIPT by using a circulator and filters. We analyze the FS and conventional power-splitting (PS) SWIPT schemes in consideration of the nonlinearity of the HPA. We show that the proposed FS SWIPT greatly outperforms the PS SWIPT in terms of the harvested power and signal-to-noise ratio (SNR).

Novel SWIPT Schemes for 5G Wireless Networks.

In this paper, we present a few novel simultaneous wireless information and power transfer (SWIPT) schemes that can be effectively used in various 5G wireless network implementations. First, we study the possibility of integrating distributed energy beamforming with the data rate fairness beamforming in a cooperative communication system with multiple cooperative relays and multiple destination users communicating simultaneously. We show that the system exploits significant performance gain using such a joint energy and data rate fairness beamforming scheme. Further, we propose an enhanced version of the SWIPT scheme, the energy-efficient modulation-based non-orthogonal multiple access (M-NOMA) SWIPT scheme, and observe its system efficiency in terms of more harvested energy. Finally, we consider an energy-harvesting SWIPT scheme where the channel response is estimated using the energy-harvesting signal as pilots superimposed on the information signal. For such a scheme, we compute the optimum transmit power ratio between the pilot and information signals under varying SNR conditions and improve the accuracy of the decoding process at the reception.

Optimization of wireless information and power transfer in multiuser OFDM systems

Simultaneous wireless information and power transfer (SWIPT), which belongs to energy harvesting techniques, is an important research topic. In existing literature, two SWIPT schemes, namely the time switching (TS) scheme and the power splitting (PS) scheme are adopted. For multiuser orthogonal frequency division multiple (OFDM) systems, this paper proposes a new SWIPT scheme named as the subcarrier sharing (SS) scheme. Resource allocation algorithms for the SS scheme are then proposed for maximizing the sum rate under the minimum harvested energy constraint. We show that the SS scheme outperforms the existing TS and the PS schemes.

Wireless Information and Power Transfer: Rate-Energy Tradeoff for Nonlinear Energy Harvesting

In this paper, we study rate-energy (R-E) tradeoffs for simultaneous wireless information and power transfer (SWIPT). In the existing literature, by invoking a simplistic and ideal assumption of linear energy harvesting, the R-E tradeoff performance was analyzed only for the four SWIPT schemes: the dynamic power splitting, type-I on–off power splitting (OPS), static power splitting, and time switching. Different from such works, in this work, we consider the realistic and practical scenario of nonlinear energy harvesting. Furthermore, to characterize the R-E tradeoff with nonlinear energy harvesting, we propose a new SWIPT scheme, the generalized OPS (GOPS). As a special case of the proposed GOPS, we also investigate an additional SWIPT scheme, the type-II OPS. Through the analysis based on the realistic nonlinear models reported in the literature, we derive new theoretical results on the R-E tradeoff, which are in sharp contrast to those in the existing literature obtained with linear energy harvesting. Furthermore, we provide various useful insights into the SWIPT system with nonlinear energy harvesting.

Rate-Energy Tradeoff and Decoding Error Probability-Energy Tradeoff for SWIPT in Finite Code Length

In this paper, the fundamental performance of the simultaneous wireless information and power transfer (SWIPT) system is studied. Unlike any existing works where the codelength was assumed to be infinity, we explicitly consider the case of the finite codelength, which is much more realistic especially for the practical SWIPT system due to its limited power and complexity. For the four well-known SWIPT schemes, we analyze the tradeoff between the rate and energy; then we study the optimality of those SWIPT schemes. Furthermore, to fully characterize the fundamental performance of the SWIPT system in the regime of finite codelength, we propose to additionally use the new tradeoff between the decoding error probability and the harvested energy. In the sense of this new tradeoff, we study the optimality of the four SWIPT schemes. For the analysis of the two types of tradeoffs, we consider two different cases: when the transmit power of symbols is adapted or not. For various scenarios, we provide useful insights into the performance of the SWIPT system in the finite codelength.

Joint Power Allocation and Splitting (JoPAS) for SWIPT in Doubly Selective Vehicular Channels

In recent years, the capacity and charging speed of batteries have become the bottleneck of mobile communications systems. With the development of wireless power transfer technologies, simultaneous wireless information and power transfer (SWIPT) emerges as a potential solution for green communications. Due to hardware limitations, the energy harvesting circuit cannot decode the signal directly. Power splitting is a popular and effective solution to this problem. Consequently, the problem of optimal power splitting at the receiver arises in addition to the conventional problem of power allocation in communications systems. SWIPT in vehicular networks is a promising technology that helps extend the lifetime of sensors installed on vehicles and roadside units. However, existing SWIPT schemes fail to consider the doubly selective characteristics of vehicular channels. In this paper, joint power allocation and splitting for SWIPT over such channels is proposed with the objective of maximizing the achievable data rate with constraints on the delivered energy. Simulations show significantly improved performance compared with the existing dynamic power splitting scheme. A suboptimal algorithm, named decoupled power allocation and splitting, is also proposed with significantly reduced computational complexity and simulations demonstrate its near-optimum performance.

A Cooperative SWIPT Scheme for Wirelessly Powered Sensor Networks

Wireless power transfer (WPT) provides a novel solution to the painstaking power-charging issue in wireless sensor networks. However, due to the propagation loss, the fast attenuation in energy transfer efficiency over the transmission distance is the main impediment to the WPT application. In this paper, we apply the simultaneous wireless information and power transfer (SWIPT) to a wirelessly powered sensor network, where each node has two circuits, which operate on energy harvesting mode and information decoding mode separately. We propose a novel cooperative SWIPT scheme (CSS) for this system. First, we present a conflict-free schedule initialization algorithm for CSS. For a given conflict-free schedule, we formulate a resource allocation problem to maximize the network energy efficiency, which is then transformed to an equivalent convex optimization problem and resolved via dual decomposition. Finally, a heuristic algorithm is presented to achieve the transmission schedule with the maximum energy efficiency and the corresponding resource assignment policy. Simulation results indicate that the CSS can significantly improve the energy efficiency of the wirelessly powered sensor network.

A Survey on Simultaneous Wireless Information and Power Transfer

This paper presents a comprehensive study related to simultaneous wireless information and power transfer (SWIPT) in different types of wireless communication setups. Harvesting energy using SWIPT is an appealing solution in the context of extending battery life of wireless devices for a fully sustainable communication system. Strong signal power increases power transfer, but also causes more interference in information transfer, causing realization of the SWIPT challenging problem. This article provides an overview of technical evolution of SWIPT. A survey and qualitative comparison of the existing SWIPT schemes is provided to demonstrate their limitations in the current and 5G networks. Open challenges are emphasized and guidelines are provided to adapt the existing schemes in order to overcome these limitations and make them fit for integrating with the modern and emerging next generation communication networks, such as 5G systems.

Simultaneous Wireless Information and Power Transfer Based on Joint Subcarrier and Power Allocation in OFDM Systems

Energy harvesting (EH) is a prominent method to extend the operation time of energy-limited wireless networks. By integrating EH into wireless communications, the same spectrum is able to be used by simultaneous wireless information and power transfer (SWIPT) without affecting the quality of service. In this paper, we propose a joint subcarrier and power allocation-based SWIPT scheme in orthogonal frequency division multiplexing (OFDM) systems. Specifically, the received OFDM subcarriers are partitioned into two groups. A fraction of the received subcarriers are allocated to form one group, which is used for information decoding (ID), and the remaining subcarriers form the other group, which is used for energy harvesting. Thus, no splitter is needed at the receiver. A joint subcarrier and power allocation problem is formulated to maximize the harvested energy, subject to the ID constraint. By using the dual decomposition method, an efficient algorithm is proposed to solve this joint resource allocation problem.

Wireless Information and Power Transfer: Rate-Energy Tradeoff for Equi-Probable Arbitrary-Shaped Discrete Inputs

In this paper, the fundamental rate-energy (R-E) tradeoffs are studied for simultaneous wireless information and power transfer (SWIPT). Unlike the existing results obtained using Gaussian input given an average power constraint, we focus on the equi-probable arbitrary shaped discrete inputs considering a peak power constraint as well as an average power constraint. For these power constraints, the transmit power strategies are presented and the R-E regions are derived. The optimality of different SWIPT schemes is first studied in terms of the R-E tradeoff for the case of negligible circuit power consumption in the information decoder. The results are extended to the case of non-negligible circuit power consumption in the information decoder. The asymptotic R-E regions are also derived, which give us useful insights into the fundamental R-E tradeoffs. Finally, the R-E regions of Gaussian input and discrete inputs are compared under an average power constraint.

Energy Harvesting Noncoherent Cooperative Communications

This paper investigates simultaneous wireless information and power transfer (SWIPT) in energy harvesting (EH) relay systems. Unlike the existing SWIPT schemes requiring the instantaneous channel state information (CSI) for coherent information delivery, we propose a noncoherent SWIPT framework for decode-and-forward (DF) relay systems bypassing the need for the instantaneous CSI and consequently saving energy in the network. The proposed SWIPT framework embraces both the power-splitting noncoherent DF (PS-NcDF) and timeswitching noncoherent DF (TS-NcDF) in a unified form, and supports arbitrary M-ary noncoherent frequency-shift keying (FSK) and differential phase-shift keying (DPSK). The exact (noncoherent) maximum-likelihood detectors (MLDs) for PS-NcDF and TS-NcDF are derived in a unified form, which involves integral evaluations yet serves as the optimum performance benchmark for noncoherent SWIPT. To reduce the computational cost of the exact MLDs, we also propose closed-form approximate MLDs achieving near-optimum performance, thus serving as a practical solution for noncoherent SWIPT. Numerical results demonstrate a performance tradeoff between the first and second hops through the adjustment of time switching or power splitting parameters, whose optimal values minimizing the symbol-error rate (SER) are strictly between 0 and 1. We demonstrate that M-FSK results in a significant energy saving over M-DPSK for M ≥ 8; thus M-FSK may be more suitable for EH relay systems.

Beamforming in Non-Regenerative Two-Way Multi-Antenna Relay Networks for Simultaneous Wireless Information and Power Transfer

Simultaneous wireless information and power transfer (SWIPT) is able to prolong the lifetime of energy constrained wireless networks. In this paper, we consider the relay beamforming design problem for SWIPT scheme in a non-regenerative two-way multi-antenna relay network. Our objective is to maximize the sum rate of two-way relay network under the transmit power constraint at relay and the energy harvesting (EH) constraint at EH receiver. For the non-convex EH-constrained relay beamforming optimization problem, we propose an iterative algorithm to find the global optimal solution based on semidefinite programming and rank-one decomposition theorem. To reduce computational complexity of global optimal solution, we transform the EH-constrained optimization problem to a difference of convex programming and propose a constrained concave convex procedure based iterative algorithm to find a local optimum. To further reduce the complexity, we propose a suboptimal solution based on the generalized eigenvectors method. When the case of multi-antenna sources is considered, we propose the alternating optimization based iterative algorithms. It is shown from simulations that considering the EH constraint, our proposed schemes outperform conventional relay beamforming schemes in the literature.