Wireless Information and Power Transfer in Underwater Acoustic Sensor Networks

Wireless information and power transfer(WIPT) enables simultaneously communications and sustainable power supplement without the erection of power supply lines and the replacement operation of the batteries for the terminals. The application of WIPT to the underwater acoustic sensor networks(UWASNs) not only retains the long range communication capabilities, but also provides an auxiliary and convenient energy supplement way for the terminal sensors, and thus is a promising scheme to solve the energy-limited problem for the UWASNs. In this paper, we propose the integration of WIPT into the UWASNs and provide an overview on various enabling techniques for the WIPT based UWASNs(WIPT-UWASNs) as well as pointing out future research challenges and opportunities for WIPT-UWASNs.

Secure Transmission Scheme Based on Dual-Thresholds for Simultaneous Wireless Information and Power Transfer

This paper studies a simultaneous wireless information and power transfer system with multiple external eavesdroppers and internal curious users.We model the random network by Poisson cluster process in consideration of the case where eavesdroppers hide around certain targets.Focusing on the users that work in harvesting-transmitting mode with time switching receivers,we establish communication model via time division multiple access.On this basis,we propose a lightweight secure transmission scheme based on dual-thresholds for physical-layer security enhancement,which consists of two protocols applied to the downlink(DL) and uplink(UL) transmission respectively.In the DL,we design a dynamic information-power switching transmission protocol based on signal-to-noise ratio threshold,which provides an opportunistic approach to reform the fixed period allocation of information and power transfer;in the UL,an energy threshold is proposed for users to control the transmission,which is called a user-led on-off transmission protocol.Furthermore,we give a comprehensive performance analysis for the proposed scheme in terms of delay,reliability,security and secrecy throughput.Based on the analysis results,we optimize the two thresholds and the DL-UL allocationcoefficient to maximize the secrecy throughput.Simulation results show the proposed scheme can bring about a substantial secrecy gain.

High-Power Simultaneous Wireless Information and Power Transfer: Injection-Locked Magnetron Technology

Applications using simultaneous wireless information and power transfer(SWIPT)have increased significantly.Wireless communication technologies can be combined with the Internet of Things to develop many innovative applications using SWIPT,which is mainly based on wireless energy harvesting from electromagnetic waves used in communications.Wireless power transfer that uses magnetrons has been developed for communication technologies.Injection-locked magnetrons that can be used to facilitate high-power SWIPT for several devices are reviewed in this paper.This new technology is expected to pave the way for promoting the application of SWIPT in a wide range of fields.

Simultaneous wireless information and power transfer with fixed and adaptive modulation

Activating Wireless Power Transfer (WPT) in Radio-Frequency (RF) to provide on-demand energy supply to widely deployed Internet of Everything devices is a key to the next-generation energy self-sustainable 6G network. However, Simultaneous Wireless Information and Power Transfer (SWIPT) in the same RF bands is challenging. The majority of previous studies compared SWIPT performance to Gaussian signaling with an infinite alphabet, which is impossible to implement in any realistic communication system. In contrast, we study the SWIPT system in a well-known Nakagami-m wireless fading channel using practical modulation techniques with finite alphabet. The attainable rate-energy-reliability tradeoff and the corresponding rationale are revealed for fixed modulation schemes. Furthermore, an adaptive modulation-based transceiver is provided for further expanding the attainable rate-energy-reliability region based on various SWIPT performances of different modulation schemes. The modulation switching thresholds and transmit power allocation at the SWIPT transmitter and the power splitting ratios at the SWIPT receiver are jointly optimized to maximize the attainable spectrum efficiency of wireless information transfer while satisfying the WPT requirement and the instantaneous and average BER constraints. Numerical results demonstrate the SWIPT performance of various fixed modulation schemes in different fading conditions. The advantage of the adaptive modulation-based SWIPT transceiver is validated.

Programmable Metasurface for Simultaneously Wireless Information and Power Transfer System

Implementing self-sustainable wireless communication systems is urgent and challenging for 5G and 6G technologies.In this paper,we elaborate on a system solution using the programmable metasurface(PMS)for simultaneous wireless information and power transfers(SWIPT),offering an optimized wireless energy management network.Both transmitting and receiving sides of the proposed solution are presented in detail.On the transmitting side,employing the wireless power transfer(WPT)technique,we present versatile power conveying strategies for near-field or far-field targets,single or multiple targets,and equal or unequal power targets.On the receiving side,utilizing the wireless energy harvesting(WEH)technique,we report our work on multi-functional rectifying metasurfaces that collect the wirelessly transmitted energy and the ambient energy.More importantly,a numerical model based on the plane-wave angular spectrum method is investigated to accurately calculate the radiation fields of PMS in the Fresnel and Fraunhofer regions.With this model,the efficiencies of WPT between the transmitter and the receiver are analyzed.Finally,future research directions are discussed,and integrated PMS for wireless information and wireless power is outlined.

Improving throughput in SWIPT-based wireless multirelay networks with relay selection and rateless codes

This paper studies a dual-hop Simultaneous Wireless Information and Power Transfer(SWIPT)-based multi-relay network with a direct link.To achieve high throughput in the network,a novel protocol is first developed,in which the network can switch between a direct transmission mode and a Single-Relay-Selection-based Cooperative Transmission(SRS-CT)mode that employs dynamic decode-and-forward relaying accomplished with Rateless Codes(RCs).Then,under this protocol,an optimization problem is formulated to jointly optimize the network operation mode and the resource allocation in the SRS-CT mode.The formulated problem is difficult to solve because not only does the noncausal Channel State Information(CSI)cause the problem to be stochastic,but also the energy state evolution at each relay is complicated by network operation mode decision and resource allocation.Assuming that noncausal CSI is available,the stochastic optimization issue is first to be addressed by solving an involved deterministic optimization problem via dynamic programming,where the complicated energy state evolution issue is addressed by a layered optimization method.Then,based on a finite-state Markov channel model and assuming that CSI statistical properties are known,the stochastic optimization problem is solved by extending the result derived for the noncausal CSI case to the causal CSI case.Finally,a myopic strategy is proposed to achieve a tradeoff between complexity and performance without the knowledge of CSI statistical properties.The simulation results verify that our proposed SRS-and-RC-based design can achieve a maximum of approximately 40%throughput gain over a simple SRS-and-RC-based baseline scheme in SWIPT-based multi-relay networks.

Simultaneous wireless information and power transfer transmitting architecture based on asynchronous space-time-coding digital metasurface[Invited]

Simultaneous wireless information and power transfer(SWIPT)architecture is commonly applied in wireless sensors or Internet of Things(IoT)devices,providing both wireless power sources and communication channels.However,the traditional SWIPT transmitter usually suffers from cross-talk distortion caused by the high peak-to-average power ratio of the input signal and the reduction of power amplifier efficiency.This paper proposes a SWIPT transmitting architecture based on an asynchronous space-time-coding digital metasurface(ASTCM).High-efficiency simultaneous transfer of information and power is achieved via energy distribution and information processing of the wireless monophonic signal reflected from the metasurface.We demonstrate the feasibility of the proposed method through theoretical derivations and experimental verification,which is therefore believed to have great potential in wireless communications and the IoT devices.

基于SWIPT的无小区大规模MIMO-NOMA系统能量效率研究

无小区大规模多输入多输出(Multiple-Input Multiple-Output,MIMO)与非正交多址接入(Non-Orthogonal Multiple Access,NOMA)都是未来6G的使能技术。无线携能通信(Simultaneous Wireless Information and Power Transfer,SWIPT)技术在进行信息解码的同时收集能量,与无小区大规模MIMO-NOMA优势互补。文中基于SWIPT研究无小区大规模MIMO-NOMA系统中的能量效率问题,通过联合优化功率分配系数和SWIPT的时隙切换(Time Switching,TS)系数,提高系统的能量效率。为了最大化能量效率,采用布谷鸟算法设计功率分配系数。考虑一种特殊情况,将所有终端的TS系数设置相同,进而推导了最佳TS系数的封闭表达式。仿真结果表明,相较于几种已有方案,文中提出的优化方案可以显著提升系统的能量效率。

硬件损伤下IRS辅助的SWIPT系统安全波束成形设计

为了提高无线携能通信(Simultaneous Wireless nformation and Power Transfer,SWIPT)通信系统的安全性,同时克服系统收发机硬件损伤(Hardware Impairments,HIs)的影响,提出一种硬件损伤下的智能反射面(Intelligent Reflecting Surface,IRS)辅助的SWIPT系统安全波束成形设计方法.考虑能量接收设备为潜在的窃听者,在基站最大发射功率、最小接收能量和IRS相移约束下,通过联合优化基站波束赋形矢量、人工噪声矢量和IRS的相移矩阵,构建系统安全速率最大化问题.针对该优化问题是非凸的,且优化变量是耦合的,提出一种基于交替优化和半正定松弛的有效算法来次优地解决该问题.仿真结果表明,本文所提算法能够在保障能量需求的同时,提升系统的安全性和抗硬件损伤能力.

有源RIS辅助SWIPT网络公平性资源分配算法

针对有源可重构智能表面(reconfigurable intelligent surface,RIS)辅助的同步无线信息与能量传输(simultaneous wireless information and power transfer,SWIPT)系统,提出了一种考虑公平性的能量资源采集分配算法,以解决因乘性衰落导致的公平性能量采集性能较差的问题。在有源RIS辅助的SWIPT系统采用功率切割架构实现信息与能量的同步传输,构建了以所有用户中最小的采集能量最大化为目标函数,用户信干噪比、有源RIS和基站发射功率、功率划分因子等满足需求为约束条件的联合资源分配问题。利用交替优化、半正定松弛、连续凸近似、罚函数等技术将不能直接解决的非凸问题转换成标准凸问题,提出了一种交替迭代的公平性采集能量算法。数值仿真结果表明,所提优化算法能够显著提高用户中能量资源分配最少的用户处采集到的能量值,保障通信网络中能量资源分配的公平性。

协同双小区下行协作NOMA-SWIPT中断性能分析

本文研究了在毫微微蜂窝网络(femtocell network,FN)中,协同双小区系统的非正交多址接入(non-orthogonal multiple access,NOMA)与无线携能通信(simultaneous wireless information and power transfer,SWIPT)下行协作通信的中断性能,提出了一种边缘用户在邻基站及源基站随机中心用户共同协作的下行接入方案。所提方案共分为两个时隙:第一时隙内由两基站向所有用户广播叠加信号,提供中继服务的中心用户对其所接收的叠加信号逐级解码并收集能量。第二时隙,中心用户将其第一时隙内所收集的能量作为额外功率资源,在优先保证自身通信质量的前提下对成功解码的边缘用户信息进行再编码转发。基于空间均质泊松点过程(Poisson point process,PPP)中心用户的位置模型,推导了中心用户与边缘用户平均中断概率的表达式,进行了蒙特卡罗仿真验证,同时分析了各仿真参数(中心用户分布半径、用户阈值速率、路径损耗指数等)与中心用户、边缘用户平均中断概率的关系。结果表明:所提方案可以改善边缘用户的下行接入中断性能和系统吞吐量。

Intelligent Reflecting Surface Assisted Transmission Optimization Strategies in Wireless Networks

Wireless Power Transfer(WPT)technology can provide real-time power for many terminal devices in Internet of Things(IoT)through millimeterWave(mmWave)to support applications with large capacity and low latency.Although the intelligent reflecting surface(IRS)can be adopted to create effective virtual links to address the mmWave blockage problem,the conventional solutions only adopt IRS in the downlink from the Base Station(BS)to the users to enhance the received signal strength.In practice,the reflection of IRS is also applicable to the uplink to improve the spectral efficiency.It is a challenging to jointly optimize IRS beamforming and system resource allocation for wireless energy acquisition and information transmission.In this paper,we first design a Low-Energy Adaptive Clustering Hierarchy(LEACH)clustering protocol for clustering and data collection.Then,the problem of maximizing the minimum system spectral efficiency is constructed by jointly optimizing the transmit power of sensor devices,the uplink and downlink transmission times,the active beamforming at the BS,and the IRS dynamic beamforming.To solve this non-convex optimization problem,we propose an alternating optimization(AO)-based joint solution algorithm.Simulation results show that the use of IRS dynamic beamforming can significantly improve the spectral efficiency of the system,and ensure the reliability of equipment communication and the sustainability of energy supply under NLOS link.

非线性EH下的SWIPT-NOMA系统性能分析

为了延长无线通信网络的寿命,提高系统的频谱效率和可靠性,扩大信号覆盖范围,对无线携能传输(Simultaneous Wireless Information and Power Transfer,SWIPT)和非正交多址接入(Non-Orthogonal Multiple Access,NOMA)技术进行研究,给出了一种简单的无线携能传输的非正交多址接入(Simultaneous Wireless Information and Power Transfer Non-Orthogonal Multiple Access,SWIPT-NOMA)传输策略。在该策略中,近用户利用功率分割(Power-Splitting,PS)协议收集基站发射信号的能量转发解码数据和自身数据,同时实现基站向远近两用户、近用户向远用户的数据传输。在考虑非线性能量收集(Energy Harvesting,EH)的基础上,推导了系统的中断概率的闭式结果,并进一步给出了高信噪比(Signal-to-Noise Ratio,SNR)下的中断性能下限。最后,通过仿真分析验证了理论推导的正确性,并得出了系统参数对系统性能的影响规律。

SWIPT不可信中继系统安全性能的优化

针对时间切换模式的无线携能传输(SWIPT)全双工中继系统,在中继为潜在窃听者的情况下,为提高物理层安全传输性能,提出一个由接收机进行协作干扰的方案,以及对能量传输和信息传输阶段的时间切换、源和目的节点的能量分配进行联合优化的算法。首先,中继节点为全双工SWIPT节点,在能量传输阶段接收射频信号中收集的能量,用于信息传输阶段信号的转发;其次,为防止不可信中继节点获得保密信息,全双工的目的节点在接收信号的同时进行协作干扰;最后,以最大化可达保密传输速率为目标,对时间切换因子、源和目的节点两个传输阶段的能量分配因子进行联合优化。仿真表明,对3个因子进行联合优化后,系统的可达保密速率要明显高于只优化其中2个、1个因子,或不进行优化的系统。

Secure analysis on artificial-noise-aided simultaneous wireless information and power transfer systems

In this paper,we investigate the secrecy outage performance in simultaneous wireless information and power transfer(SWIPT)systems taking artificial noise assistance into account.Multiple antennas in the source and a single antenna in both the legitimate receiver and the eavesdropper are assumed.Specifically,the transmitted signal at the source is composed of two parts,where the first part is the information symbols and the other is the noise for the eavesdropper.To avoid making noise in the legitimate receiver,these two parts in the transmitted signals are modulated into two orthogonal dimensions according to the instantaneous channel state between the source and the legitimate receiver.We derive an approximate closed-form expression for the secrecy outage probability(SOP)by adopting the Gauss-Laguerre quadrature(GLQ)method,where the gap between the exact SOP and our approximate SOP converges with increase of the summation terms in the GLQ.To obtain the secrecy diversity order and secrecy array gain for the considered SWIPT system,the asymptotic result of the SOP is also derived.This is tight in the high signal-to-noise ratio region.A novel and robust SOP approximation is also analyzed given a small variance of the signal-to-interference-plus-noise ratio at the eavesdropper.Some selected Monte-Carlo numerical results are presented to validate the correctness of the derived closed-form expressions.

Optimization of a robust collaborative-relay beamforming design for simultaneous wireless information and power transfer

We investigate a collaborative-relay beamforming design for simultaneous wireless information and power transfer. A non-robust beamforming design that assumes availability of perfect channel state information(CSI) in the relay nodes is addressed. In practical scenarios, CSI errors are usually inevitable; therefore, a robust collaborativerelay beamforming design is proposed. By applying the bisection method and the semidefinite relaxation(SDR)technique, the non-convex optimization problems of both non-robust and robust beamforming designs can be solved.Moreover, the solution returned by the SDR technique may not always be rank-one; thus, an iterative sub-gradient method is presented to acquire the rank-one solution. Simulation results show that under an imperfect CSI case, the proposed robust beamforming design can obtain a better performance than the non-robust one.

基于深度强化学习的SWIPT边缘网络联合优化方法

边缘计算(EC)与无线携能通信(SWIPT)技术能够提升传统网络性能,但同时也增加了系统决策制定的难度和复杂度。而基于最优化方法所设计的系统决策往往具有较高的计算复杂度,无法满足系统的实时性需求。为此,针对EC与SWIPT辅助的无线传感网络(WSN),联合考虑网络中波束成形、计算卸载与功率控制问题,建立了系统能效最优化数学模型;其次,针对该模型的非凸与参数耦合特征,通过设计系统的信息交换过程,提出基于深度强化学习的联合优化方法,该方法无须建立环境模型,采用奖励函数代替Critic网络对动作进行评估,能降低决策制定难度并提升实时性;最后,基于该方法设计了改进的深度确定性策略梯度(IDDPG)算法,并与多种最优化算法和机器学习算法进行仿真对比,验证了联合优化方法在降低计算复杂度、提升决策实时性方面的优势。

异构蜂窝网络中基于SWIPT的D2D资源分配算法研究

为了解决异构蜂窝网络中D2D(Device-to-Device)通信干扰导致系统能量效率下降的问题,提出一种基于SWIPT的D2D通信资源分配策略,以实现D2D链路的能量效率最大化。该策略对系统中多种干扰进行建模,构建干扰图和伙伴候选集合;将优化问题转化为功率控制和信道分配两个子问题,运用KKT条件和拉格朗日乘子法,求解D2D链路复用候选集中子信道的最优发射功率和功率分割比。仿真结果表明,所提出的分配策略能明显提升系统的能量效率,在保证服务质量的前提下能有效提高D2D用户接入率。

基于SWIPT混合协议及联合解码的能量效率研究

针对无线通信网络中小区边缘用户通信质量问题,采用传感中继进行协作通信,为解决引入传感中继所引起的能耗问题,提出了基于无线携能通信(SWIPT)混合协议及联合最大比解码(MRC)方式的能量优化方法。将以最大化主用户信号遍历链路能量效率(EE)为目标的分式规划问题,转化为易求解的非分式规划问题;从功率控制、功率/时间分割因子2个角度分析EE;利用Dinkelbach迭代算法优化基站发射功率,并结合遗传算法联合优化功率分配因子和时间分割因子,以实现遍历链路EE最大化。仿真实验结果表明,该方法在无线认知传感中继网络中能够更好地提升能量效率。

IRS和人工噪声辅助的MIMO-SWIPT系统安全传输方案设计

针对多天线无线携能通信系统中能量收集节点作为潜在窃听者的信息安全问题,提出了一种智能反射面(Intelligent Reflecting Surface,IRS)和人工噪声辅助的物理层安全传输方案。首先考虑发射功率、能量收集门限以及IRS单位模约束,以最大化系统安全速率为优化目标,在合法用户直射链路不可用的情况下,联合设计发射端波束赋形矩阵、人工噪声协方差矩阵以及IRS相移矩阵,建模一非线性多变量耦合的非凸优化问题;接着利用均方误差准则等价转换非凸目标函数,并利用连续凸逼近方法(Successive Convex Approximation,SCA)处理非凸的能量收集约束;最后基于交替优化框架,分别用拉格朗日对偶方法和基于价格机制的优化最小化(Majorization-Minimization,MM)算法求解发射端变量和IRS端变量。仿真结果表明,与现有方案相比,所提算法能够在保障能量收集需求的同时大幅度提升系统的安全性能。