Wireless Information and Power Transfer for IoT: Pulse Position Modulation, Integrated Receiver, and Experimental Validation

Radio frequency (RF) signals have been relied upon for both wireless information delivery and wireless charging to the massively deployed low-power Internet of Things (IoT) devices. Extensive efforts have been invested in physical layer and medium-access-control layer design for coordinating simultaneous wireless information and power transfer (SWIPT) in RF bands. Different from the existing works, we study the coding controlled SWIPT from the information theoretical perspective with practical transceiver. Due to its practical decoding implementation and its flexibility on the codeword structure, unary code is chosen for joint information and energy encoding. Wireless power transfer (WPT) performance in terms of energy harvested per binary sign and of battery overflow/underflow probability is maximised by optimising the codeword distribution of coded information source, while satisfying required wireless information transfer (WIT) performance in terms of mutual information. Furthermore, a Genetic Algorithm (GA) aided coding design is proposed to reduce the computational complexity. Numerical results characterise the SWIPT performance and validate the optimality of our proposed GA aided unary coding design.

Chapter 10 - Transmit beamforming for simultaneous wireless information and power transfer

5G-based green broadband communication system design with simultaneous wireless information and power transfer

Far-field wireless power transfer (WPT) and simultaneous wireless information and power transfer (SWIPT) have become increasingly important in radio frequency (RF) and communication communities recently. The problem of modulation design for SWIPT has however been scarcely addressed. In this paper, a modulation scheme based on asymmetric phase-shift keying (PSK) is considered, which improves the SWIPT rate-energy tradeoff region significantly. The nonlinear rectifier model, which accurately models the energy harvester, is adopted for evaluating the output direct current (DC) power at the receiver. The harvested DC power is maximized under an average power constraint at the transmitter and a constraint on the rate of information transmitted via a multi-carrier signal over a flat fading channel. As a consequence of the rectifier nonlinearity, this work highlights that asymmetric PSK modulation provides benefits over conventional symmetric PSK modulation in SWIPT and opens the door to systematic modulation design tailored for SWIPT.

This paper presents a ASK modulation based modeling of Simultaneous Wireless Information and Power Transfer (SWIPT) system in LabVIEW. It supports in designing of SWIPT based system which able to harvest RF energy along with transfer of information simultaneously. At the receiver end, both RF energy harvesting (EH) and information decoding (ID) paths are modeled. RF energy harvesting path consists of RF rectifier and low pass filter. While ID path contains RF envelope detector and ASK demodulator. For the simulation verification of SWIPT system, a 2-ASK modulated RF signal is used at 900MHz. This modeling provides flexible parameters selection for the simulation of SWIPT system which helps in understanding and development of SWIPT system.

Realising both wireless information transfer (WIT) and wireless power transfer (WPT) in the same RF spectral band has imposed great challenges on the system design but the spectral efficiency can be substantially improved, which triggers the significant research interest in the simultaneous wireless information and power transfer (SWIPT). In order to fully exploit the limited spectral resources, a non-orthogonal-multiple-access (NOMA) technique aided SWIPT system is considered for simultaneously realising both of WIT and WPT, which consists of a single access point (AP), a single WPT user and a pair of WIT users. The AP delivers the requested information to the pair of WIT users by adopting the NOMA technique. In order to maximise the amount of energy received by the WPT user, a novel constellation rotation based modulation scheme is proposed for constructively combining the symbols requested by the pair of the WIT users by optimising the constellation rotation angle. By considering the sensitivity of the energy harvester, the simulation results demonstrate that our modulation scheme is capable of efficiently increasing the energy harvested by the WPT user without incurring additional symbol detection errors.

In this paper, we investigate the performance of cache-assisted simultaneous wireless information and power transfer (SWIPT) cooperative systems, in which one source communicates with one destination via the aid of multiple relays. In order to prolong the relays’ serving time, the relays are assumed to be equipped with a cache memory and energy harvesting (EH) capability. Based on the time-splitting mechanism, we analyze the effect of caching on the system performance in terms of the serving throughput and the stored energy at the relay. In particular, two optimization problems are formulated to maximize the relay-destination throughput and the energy stored at the relay subject to some quality-of-service (QoS) constraints, respectively. By using the KKT conditions and with the help of the Lambert function, closed-form solutions are obtained for the two formulated problems. In order to further improve the performance, a relay selection policy is introduced to select the best relay based on either the maximum throughput between the relays’ and destination link or maximum stored energy at the relay, for conveying information to the destination. Numerical results reveal significant benefits of incorporating caching capabilities to SWIPT systems, in terms of improved serving time, throughput, and EH performance at the relays.

In this paper, we provide a comprehensive literature survey on simultaneous wireless information and power transfer (SWIPT) in multi-antenna systems. We first review recent contributions on the theory analysis of SWIPT from information theoretic standpoint and introduce the tradeoff between information transfer and power transfer under various settings. Then, we focus on the utilization of multi-antenna techniques to solve existing problems of SWIPT. Contributions on the implementation aspects of multi-antenna SWIPT are summarized. The performance of SWIPT is evaluated by different metrics, therefore, we review the works on dynamic SWIPT optimization based on objective function using multi-antenna techniques. In addition, the implementation of SWIPT brings up secure issue. Thus, we summarize recent works on secure SWIPT. Finally, we present researches combining SWIPT with state-of-the-art techniques due to potential application in different scenarios.

Simultaneous wireless information and power transfer (SWIPT) formed by the mixture of communication technology and power transmission is one of the research focuses in the field of wireless communication. This paper introduces the architecture of the SWIPT system, analyzes the key technologies, presents a 2.45GHz microwave rectifier circuit at low input power for energy harvesting. Finally, with the use of Ultra-Narrow Band (UNB) as the modulation scheme, the practical SWIPT receiver system is modeled and simulated. The results provide that using UNB signal as the modulation scheme is a new feasible way for SWIPT.

In 5G wireless networks, the system capacity and the number of users will be significantly increased. However, the energy consumed for the communication will also be increased, which results in low system energy efficiency. Simultaneous wireless information and power transfer (SWIPT) can enable the user to perform energy harvesting from the radio-frequency signals parallel with the information decoding, which can effectively improve the system energy efficiency. In this paper, we study the energy efficiency optimization problem for the orthogonal frequency-division multiplexing-based 5G wireless networks with SWIPT, in which the subcarrier and power allocation are jointly optimized to maximize the system energy efficiency for single user and multiple user cases. For those two cases, through mathematical transforming, we use the Dinkelbach iterative method and the Lagrange dual method to solve the non-convex energy efficiency optimization problem. Simulation results show that compared with other algorithms, our proposed algorithm can achieve higher energy efficiency.

This book chapter investigates the advances of energy harvesting (EH) and multiple accesses protocols for smart city applications. In particular, a novel communication scheme that combines EH and a cooperative non-orthogonal multiple access (NOMA) system is introduced. In the proposed scheme, the relay harvests energy from the base station to serve some user groups including the near and far users. Later, simultaneous wireless information and power transfer (SWIPT) technique is exploited to determine performance improvement at least amount of harvested energy. The other parameters need to investigate the impact of imperfect power allocation factors on system performance. It is proved that introducing SWIPT does not harm system performance. Furthermore, the outage probability of both near and far users is derived and indicated in closed-form expressions. Numerical simulations are conducted to examine the outage probability of the proposed scheme and to verify the derived formulas. The proposed scheme has the potential to solve the problem of EH in the context of smart city.KeywordsSimultaneous wireless information and power transfer (SWIPT)Non-orthogonal multiple access (NOMA)Outage probabilitySmart cities

Antenna beamforming for Simultaneous Wireless Information and Power Transfer (SWIPT) and Wireless Power Transfer (WPT) in an indoor 6G communication system is presented in this paper. The objective function is to maximize the total harvesting power for the SWIPT and WPT nodes with the constraints of the bit error rate and minimum harvesting power. In the study, the power-splitting ratio between harvesting power and decoding information can be adjusted for the SWIPT node. Due to the non-convex problem, we use Self-Adaptive Dynamic Differential Evolution (SADDE) to optimize the designed multi-objective function. We use a symmetric antenna array to study three situations of distance—closer, farther, and similar—between the transmitting antenna and the individual SWIPT and WPT nodes in this paper. Experimental results show that the overall harvesting efficiency is improved, especially in the case of SWIPT nodes closer to the transmitter. The total harvesting power can be improved by 86.7% in the total short-distance case, and by 7.87% in the total long-distance case.

This letter puts forth a novel way to manage interference in simultaneous wireless information and power transfer (SWIPT) systems by utilizing physical-layer network coding (PNC). We consider multi-user multiple-input single-output (MU-MISO) broadcast channels. Unlike the conventional zero-forcing scheme, the PNC-SWIPT scheme introduced in this letter does not eliminate the interfering signals at the receivers. The PNC-SWIPT scheme cancels out the undesired messages over a finite field during PNC demodulation for information decoding (ID). It preserves the interfering signals which are beneficial energy sources for energy harvesting (EH). Simulation results show that the PNC-SWIPT scheme achieves superior EH performance than conventional interference mitigation schemes, such as zero-forcing (ZF) and maximizing EH precoding (Max EH), while maintaining the same ID performance. The performance improvement of the PNC-SWIPT scheme mainly comes from canceling out the interference at the receivers from the aspect of data by PNC, without eliminating the interfering signals which are beneficial energy sources.

This chapter examines simultaneous wireless information and power transfer (SWIPT) scenarios. It discusses the main SWIPT receivers, namely, separate and co-located receivers. The chapter provides numerical examples on the performance of the designed SWIPT precoding strategy. It focuses on a co-located SWIPT system, where a HAP serves a set S of devices performing both energy harvesting and information decoding in a given frequency band. The chapter illustrates some numerical results on the performance of the time switching and power splitting protocols. It also discusses some specific promising approaches to boost the performance of SWIPT systems for general wireless energy transfer (WET)-powered internet of things networks. WET and SWIPT systems are subject to non-linear responses that are often model-intractable unless too strong assumptions are adopted. The chapter concludes with an overview of some potential techniques to enable efficient SWIPT in future networks.

The main challenges of sensing in harsh industrial and biological environments are the limited energy of sensor nodes and the difficulty of charging sensor nodes. Simultaneous wireless information and power transfer (SWIPT) is a non-invasive option to replenish energy. SWIPT harvests energy and decodes information from the same RF signal, which is influencing the design of a wireless sensor network. In multi-hop multi-flow wireless sensor networks, interference generally exists, and the interference has a different influence on SWIPT. Route, interference and SWIPT are dependent. However, existing works consider SWIPT link resource allocation with a given route or only select path for one flow without interference. Therefore, this paper firstly analyzes the influence of interference on SWIPT, and select the SWIPT routing with interference. We design an interference-based information and energy allocation model to maximize the link capacity with SWIPT. Then, we design an interference-aware route metric, formulate SWIPT routing problem, and design an interference-aware SWIPT routing algorithm. The simulation results show that as the number of flows increases, there is more likely to obtain performance gains from interference and SWIPT.