When deploying Reconfigurable Intelligent Surface(RIS)to improve System Sum-Rate(SSR),the timeliness and accuracy of SSR optimization methods are difficult to achieve simultaneously through a single algorithm.Some alg...When deploying Reconfigurable Intelligent Surface(RIS)to improve System Sum-Rate(SSR),the timeliness and accuracy of SSR optimization methods are difficult to achieve simultaneously through a single algorithm.Some algorithms focus on timeliness,while some focus on accuracy.In this paper,in order to take into account the timeliness and accuracy of the system comprehensively,we construct SSR analysis model of RIS-assisted multiuser downlink communication system and propose several new optimization methods.The goal is to maximize SSR by using the proposed algorithms to jointly optimize power allocation and reflection coefficients.To solve this comprehensive problem,two sets of Alternating Optimization(AO)-based timeliness algorithms and one set of Monotonic Optimization(MO)-based accuracy algorithms are proposed separately to jointly optimize system performance.First,the Water-Filling(WF)-based and penalty-based low complexity algorithms are developed to optimize power allocation and reflection coefficients respectively.To improve the reality of the calculation,penalty-based algorithm cleverly considers residual noise that is difficult to calculate.Then,for further improve the timeliness,a new Successive Convex Approximation(SCA)-based low complexity algorithm is designed to further optimize reflection coefficients and its convergence is proved.Third,in order to verify the effectiveness of the proposed timeliness algorithms,we further propose MO-based accuracy algorithms,in which,the Polyblock Outer Approximation(POA)algorithm,the Semidefinite Relaxation(SDR)method,and the bisection search algorithm are combined in a novel way.Numerical results confirm the timeliness of AO-based algorithms and the accuracy of MO-based algorithms.They supervise and complement each other.展开更多
Dear Editor,As the Internet of things(IoT)and autonomous driving continue to evolve,positioning technology faces increasing demands for higher accuracy and reliability.Traditional positioning methods often struggle in...Dear Editor,As the Internet of things(IoT)and autonomous driving continue to evolve,positioning technology faces increasing demands for higher accuracy and reliability.Traditional positioning methods often struggle in complex signal environments with multipath interference and non-line-of-sight(NLOS)conditions.Reconfigurable intelligent surfaces(RIS),an innovative technology that can flexibly control signal propagation,offer new possibilities for positioning systems.展开更多
With digital coding technology,reconfigurable intelligent surfaces(RISs)become powerful real-time sys-tems for manipulating electromagnetic(EM)waves.However,most automatic RIS designs involve exten-sive numerical simu...With digital coding technology,reconfigurable intelligent surfaces(RISs)become powerful real-time sys-tems for manipulating electromagnetic(EM)waves.However,most automatic RIS designs involve exten-sive numerical simulations of the unit,including the passive pattern and active devices,requiring high data acquisition and training costs.In addition,for passive patterns,the widely employed random pixe-lated method presents design efficiency and effectiveness challenges due to the massive pixel combina-tions and blocked excitation current flow in discrete patterns.To overcome these two critical problems,we propose a versatile RIS design paradigm with efficient topology representation and a separate design architecture.First,a non-uniform rational B-spline(NURBS)is introduced to represent continuous pat-terns and solve excitation current flow issues.This representation makes it possible to finely tune con-tinuous patterns with several control points,greatly reducing the pattern solution space by 20-fold and facilitating RIS optimization.Then,employing multiport network theory to separate the passive pat-tern and active device from the unit,the separate design architecture significantly reduces the dataset acquisition cost by 62.5%.Through multistep multiport calculation,the multistate EM responses of the RIS under different structural combinations can be quickly obtained with only one prediction of pattern response,thereby achieving dataset and model reuse for different RIS designs.With a hybrid continuous-discrete optimization algorithm,three examples—including two typical high-performance RISs and an ultra-wideband multilayer RIS—are provided to validate the superiority of our paradigm.Our work offers an efficient solution for RIS automatic design,and the resulting structure is expected to boost RIS appli-cations in the fields of wireless communication and sensing.展开更多
Reconfigurable intelligent surface(RIS)has proven to be promising for future wireless communication.Due to its ability to manipulate electromagnetic(EM)waves,RIS provides a flexible and programmable way to implement i...Reconfigurable intelligent surface(RIS)has proven to be promising for future wireless communication.Due to its ability to manipulate electromagnetic(EM)waves,RIS provides a flexible and programmable way to implement intelligent wireless environments.While path loss modeling has been conducted in some prior research,an issue remaining unknown is the characteristics of multi-beam path loss for RIS.In this paper,we model,simulate and measure the multi-beam path loss in RIS-assisted broadcast communication scenarios.We propose two specific configurations of RIS and derive the path loss models,which reveal that the incident beam can be equally divided into multiple beams without power loss through rational design of the phase coding.The proposed path loss model is validated through simulation subsequently.To further verify our conclusions,we build a millimeter wave(mmWave)measurement system with a 35 GHz fabricated RIS.The measurement result corresponds well with the simulation,which shows a difference of about 3 dB in the received signal power of quad-beam compared with dual-beam,as well as dual-beam compared with single-beam,except for the impact of radiation patterns of the antennas and RIS elements.展开更多
Reconfigurable intelligent surface(RIS)is a promising candidate technology of the upcoming Sixth Generation(6G)communication system for its ability to provide unprecedented spectral and energy efficiency increment thr...Reconfigurable intelligent surface(RIS)is a promising candidate technology of the upcoming Sixth Generation(6G)communication system for its ability to provide unprecedented spectral and energy efficiency increment through passive beamforming.However,it is challenging to obtain instantaneous channel state information(I-CSI)for RIS,which obliges us to use statistical channel state information(S-CSI)to achieve passive beamforming.In this paper,RIS-aided multiple-input single-output(MISO)multi-user downlink communication system with correlated channels is investigated.Then,we formulate the problem of joint beamforming design at the AP and RIS to maximize the sum ergodic spectral efficiency(ESE)of all users to improve the network capacity.Since it is too hard to compute sum ESE,an ESE approximation is adopted to reformulate the problem into a more tractable form.Then,we present two joint beamforming algorithms,namely the singular value decomposition-gradient descent(SVD-GD)algorithm and the fractional programming-gradient descent(FP-GD)algorithm.Simulation results show the effectiveness of our proposed algorithms and validate that 2-bits quantizer is enough for RIS phase shifts implementation.展开更多
Reconfigurable Intelligent Surface(RIS)is regarded as a cutting-edge technology for the development of future wireless communication networks with improved frequency efficiency and reduced energy consumption.This pape...Reconfigurable Intelligent Surface(RIS)is regarded as a cutting-edge technology for the development of future wireless communication networks with improved frequency efficiency and reduced energy consumption.This paper proposes an architecture by combining RIS with Generalized Spatial Modulation(GSM)and then presents a Multi-Residual Deep Neural Network(MR-DNN)scheme,where the active antennas and their transmitted constellation symbols are detected by sub-DNNs in the detection block.Simulation results demonstrate that the proposed MR-DNN detection algorithm performs considerably better than the traditional Zero-Forcing(ZF)and the Minimum Mean Squared Error(MMSE)detection algorithms in terms of Bit Error Rate(BER).Moreover,the MR-DNN detection algorithm has less time complexity than the traditional detection algorithms.展开更多
In this paper,a physical model of RIS of bistatic polarized radar cross section is derived starting from the Stratton-Chu equations under the assumptions of physical optics,PEC,far field and rectangular RIS element.In...In this paper,a physical model of RIS of bistatic polarized radar cross section is derived starting from the Stratton-Chu equations under the assumptions of physical optics,PEC,far field and rectangular RIS element.In the context of important physical characteristics of the backscattering polarization of RIS,the modeling of the RIS wireless channel requires a tradeoff between complexity and accuracy,as well as usability and simplicity.For channel modeling of RIS systems,RIS is modelled as multi-equivalent virtual base stations(BSs)induced by multi polarized electromagnetic waves from different incident directions.The comparison between test and simulation results demonstrates that the proposed algorithm effectively captures the key characteristics of the general RIS element polarization physical model and provides accurate results.展开更多
In this paper,we propose a rate splitting multiple access(RSMA)based integrated sensing and communication system(ISAC),where the sensing and communication are realized simultaneously with the RSMA signal.Further,recon...In this paper,we propose a rate splitting multiple access(RSMA)based integrated sensing and communication system(ISAC),where the sensing and communication are realized simultaneously with the RSMA signal.Further,reconfigurable holographic surface(RHS)is utilized to replace the traditional antennas for beam generation,expecting to combine the advantages of RSMA and RHS.To maximize the weighted summation of system rate and probing power,an optimization problem is formulated to jointly design the digital beamformer,the holographic beamformer and the message splitting vectors.To solve the non-convex problem,we first decompose it into two subproblems,where one jointly designs the digital beamformer and message splitting vectors,and the other deals with the holographic beamformer.An iterative algorithm,which leverages successive convex approximation and semi-definite relaxation,is proposed to achieve the sub-optimal solution through solving these two subproblems alternatively.Simulations confirm the effectiveness and efficiency of the proposed algorithm.展开更多
In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assiste...In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assisted multi-antenna jamming(MAJ)scheme denoted by ARIS-MAJ to interfere with the illegal signal transmission.In order to strike a balance between the jamming performance and the energy consumption,we consider a so-called jamming energy efficiency(JEE)which is defined as the ratio of achievable rate reduced by the jamming system to the corresponding power consumption.We formulate an optimization problem to maximize the JEE for the proposed ARIS-MAJ scheme by jointly optimizing the jammer’s beamforming vector and ARIS’s reflecting coefficients under the constraint that the jamming power received at the illegal user is lower than the illegal user’s detection threshold.To address the non-convex optimization problem,we propose the Dinkelbach-based alternating optimization(AO)algorithm by applying the semidefinite relaxation(SDR)algorithm with Gaussian randomization method.Numerical results validate that the proposed ARIS-MAJ scheme outperforms the passive reconfigurable intelligent surface(PRIS)-assisted multi-antenna jamming(PRIS-MAJ)scheme and the conventional multiantenna jamming scheme without RIS(NRIS-MAJ)in terms of the JEE.展开更多
In this paper,we investigate the reconfigurable intelligent surface(RIS)-enabled multiple-input-single-output orthogonal frequency division multiplexing(MISO-OFDM)system under frequency-selective channels,and propose ...In this paper,we investigate the reconfigurable intelligent surface(RIS)-enabled multiple-input-single-output orthogonal frequency division multiplexing(MISO-OFDM)system under frequency-selective channels,and propose a low-complexity alternating optimization(AO)based joint beamforming and RIS phase shifts optimization algorithm to maximize the achievable rate.First,with fixed RIS phase shifts,we devise the optimal closedform transmit beamforming vectors corresponding to different subcarriers.Then,with given active beamforming vectors,near-optimal RIS reflection coefficients can be determined efficiently leveraging fractional programming(FP)combined with manifold optimization(MO)or majorization-minimization(MM)framework.Additionally,we also propose a heuristic RIS phase shifts design approach based on the sum of subcarrier gain maximization(SSGM)criterion requiring lower complexity.Numerical results indicate that the proposed MO/MM algorithm can achieve almost the same rate as the upper bound achieved by the semidefinite relaxation(SDR)algorithm,and the proposed SSGM based scheme is only slightly inferior to the upper bound while has much lower complexity.These results demonstrate the effectiveness of the proposed algorithms.展开更多
Reconfigurable intelligent surface(RIS)can manipulate the wireless propagation environment by smartly adjusting the amplitude/phase in a programmable panel,enjoying the improved performance.The accurate acquisition of...Reconfigurable intelligent surface(RIS)can manipulate the wireless propagation environment by smartly adjusting the amplitude/phase in a programmable panel,enjoying the improved performance.The accurate acquisition of the instantaneous channel state information(CSI)in the cascaded RIS chain makes an indispensable contribution to the performance gains.However,it is quite challenging to estimate the CSI in a time-variant scenario due to the limited signal processing capability of the passive elements embedded in a RIS pannel.In this work,a channel estimation scheme for the RIS-assisted wireless communication system is proposed,which is demonstrated to perform well in a time-variant scenario.The cascaded RIS channel is modeled as a state-space model based upon the mobility situations.In addition,to fully exploit the time correlation of channel,Kalman filter is employed by taking the prior information of channels into account.Further,the optimal reflection coefficients are derived according to the minimum mean square error(MMSE)criterion.Numerical results show that the proposed methods exhibit superior performance if compared with a conventional channel estimation scheme.展开更多
In this paper,a reconfigurable intelligent surface(RIS)-assisted MIMO wireless secure communication system is considered,in which a base station(BS)equipped with multiple antennas exploits statistical channel state in...In this paper,a reconfigurable intelligent surface(RIS)-assisted MIMO wireless secure communication system is considered,in which a base station(BS)equipped with multiple antennas exploits statistical channel state information to communicate with a legitimate multi-antenna user,in the presence of an eavesdropper,also equipped with multiple antennas.We firstly obtain an analytical expression of the ergodic secrecy rate based on the results of largedimensional random matrix theory.Then,a jointly alternating optimization algorithm with the method of Taylor series expansion and the projected gradient ascent method is proposed to design the transmit covariance matrix at the BS,as well as the diagonal phaseshifting matrix to maximize the ergodic secrecy rate.Simulations are conducted to demonstrate the accuracy of the derived analytical expressions,as well as the superior performance of our proposed algorithm.展开更多
Reconfigurable intelligent surface(RIS)has been proposed as a potential solution to improve the coverage and spectrum efficiency for future wireless communication.However,the privacy of users’data is often ignored in...Reconfigurable intelligent surface(RIS)has been proposed as a potential solution to improve the coverage and spectrum efficiency for future wireless communication.However,the privacy of users’data is often ignored in previous works,such as the user’s location information during channel estimation.In this paper,we propose a privacy-preserving design paradigm combining federated learning(FL)with RIS in the mmWave communication system.Based on FL,the local models are trained and encrypted using the private data managed on each local device.Following this,a global model is generated by aggregating them at the central server.The optimal model is trained for establishing the mapping function between channel state information(CSI)and RIS’configuration matrix in order to maximize the achievable rate of the received signal.Simulation results demonstrate that the proposed scheme can effectively approach to the theoretical value generated by centralized machine learning(ML),while protecting user’privacy.展开更多
In this paper,we survey state-of-the-art research outcomes in the burgeoning field of Reconfigurable Intelligent Surface(RIS),given its potential for significant performance enhancement of next-generation wireless com...In this paper,we survey state-of-the-art research outcomes in the burgeoning field of Reconfigurable Intelligent Surface(RIS),given its potential for significant performance enhancement of next-generation wireless communication networks by means of adapting a propagation environment.Emphasis has been placed on several aspects gating the commercial viability of future network deployment.Comprehensive summaries are provided for practical hardware design considerations and broad implications of artificial intelligence techniques,as are in-depth outlooks on the salient aspects of system models,use cases,and physical layer optimization techniques.展开更多
Reconfigurable intelligent surface(RIS)is an emerging meta-surface that can provide additional communications links through reflecting the signals,and has been recognized as a strong candidate of 6G mobile communicati...Reconfigurable intelligent surface(RIS)is an emerging meta-surface that can provide additional communications links through reflecting the signals,and has been recognized as a strong candidate of 6G mobile communications systems.Meanwhile,it has been recently admitted that implementing artificial intelligence(AI)into RIS communications will extensively benefit the reconfiguration capacity and enhance the robustness to complicated transmission environments.Besides the conventional model-driven approaches,AI can also deal with the existing signal processing problems in a data-driven manner via digging the inherent characteristic from the real data.Hence,AI is particularly suitable for the signal processing problems over RIS networks under unideal scenarios like modeling mismatching,insufficient resource,hardware impairment,as well as dynamical transmissions.As one of the earliest survey papers,we will introduce the merging of AI and RIS,called AIRIS,over various signal processing topics,including environmental sensing,channel acquisition,beamforming design,and resource scheduling,etc.We will also discuss the challenges of AIRIS and present some interesting future directions.展开更多
It is assumed that reconfigurable intelligent surface(RIS)is a key technology to enable the potential of mmWave communications.The passivity of the RIS makes channel estimation difficult because the channel can only b...It is assumed that reconfigurable intelligent surface(RIS)is a key technology to enable the potential of mmWave communications.The passivity of the RIS makes channel estimation difficult because the channel can only be measured at the transceiver and not at the RIS.In this paper,we propose a novel separate channel estimator via exploiting the cascaded sparsity in the continuously valued angular domain of the cascaded channel for the RIS-enabled millimeter-wave/Tera-Hz systems,i.e.,the two-stage estimation method where the cascaded channel is separated into the base station(BS)-RIS and the RIS-user(UE)ones.Specifically,we first reveal the cascaded sparsity,i.e.,the sparsity exists in the hybrid angular domains of BS-RIS and the RIS-UEs separated channels,to construct the specific sparsity structure for RIS enabled multi-user systems.Then,we formulate the channel estimation problem using atomic norm minimization(ANM)to enhance the proposed sparsity structure in the continuous angular domains,where a low-complexity channel estimator via Alternating Direction Method of Multipliers(ADMM)is proposed.Simulation findings demonstrate that the proposed channel estimator outperforms the current state-of-the-arts in terms of performance.展开更多
With the advantage of programmable electromagnetic properties,Reconfigurable Intelligent Surfaces(RISs)havedrawn wide attention from both industry and academia.RIS-assisted communication systems can promote hugewirele...With the advantage of programmable electromagnetic properties,Reconfigurable Intelligent Surfaces(RISs)havedrawn wide attention from both industry and academia.RIS-assisted communication systems can promote hugewireless channel quality improvement and remarkable coverage enhancement.This paper proposes generalpathloss model,radiation pattern and mirror beam effect of 1-bit RIS at sub-6 GHz band.Field trails have beencarried out in outdoor and indoor deployment scenarios.The proposed model is validated through extensivesimulations and field-trial measurements.In addition,an optimized RIS phase-shit design process for the mirrorbeam elimination is proposed and validated with simulations.The proposed theoretical model and measurementresults can promote future research and application in RIS-assisted communications.展开更多
To further improve the secrecy rate,a joint optimization scheme for the reconfigurable intelligent surface(RIS)phase shift and the power allocation is proposed in the untrusted relay(UR)networks assisted by the RIS.Th...To further improve the secrecy rate,a joint optimization scheme for the reconfigurable intelligent surface(RIS)phase shift and the power allocation is proposed in the untrusted relay(UR)networks assisted by the RIS.The eavesdropping on the UR is interfered by a source-based jamming strategy.Under the constraints of unit modulus and total power,the RIS phase shift,the power allocation between the confidential signal and the jamming signal,and the power allocation between the source node and the UR are jointly optimized to maximize the secrecy rate.The complex multivariable coupling problem is decomposed into three sub-problems,and the non-convexity of the objective function and the constraints is solved with semi-definite relaxation.Simulation results indicate that the secrecy rate is remarkably enhanced with the proposed scheme compared with the equal power allocation scheme,the random phase shift scheme,and the no-RIS scheme.展开更多
Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the el...Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the electromagnetic waves from the active transmission for additional information transfer(i.e.,passive transmission).In this paper,a hybrid RIS-based modulation,termed hybrid phase and code modulation(HPCM),is proposed to improve the reliability of RIS-assisted symbiotic radio.In RIS-HPCM,the RIS simultaneously performs direct sequence spread spectrum and passive beamforming on incident signals.Moreover,both the spreading code and phase offset are exploited to carry the RIS’s own information.A low-complexity detector is designed,in which the receiver first detects the spreading codes and then demodulates the constellation symbols.We analyze the bit error rate(BER)performance of RIS-HPCM over Rician fading channels.BER upper bounds and approximate BER expressions are derived in closed-form for maximum-likelihood and low-complexity detectors,respectively.Simulation results in terms of BER verify the analysis and show the superiority of RIS-HPCM over the existing RIS-based modulation.展开更多
In this paper,a differential scheme is proposed for reconfigurable intelligent surface(RIS)assisted spatial modulation,which is referred to as RISDSM,to eliminate the need for channel state information(CSI)at the rece...In this paper,a differential scheme is proposed for reconfigurable intelligent surface(RIS)assisted spatial modulation,which is referred to as RISDSM,to eliminate the need for channel state information(CSI)at the receiver.The proposed scheme is an improvement over the current differential modulation scheme used in RIS-based systems,as it avoids the high-order matrix calculation and improves the spectral efficiency.A mathematical framework is developed to determine the theoretical average bit error probability(ABEP)of the system using RIS-DSM.The detection complexity of the proposed RIS-DSM scheme is extremely low through the simplification.Finally,simulations results demonstrate that the proposed RIS-DSM scheme can deliver satisfactory error performance even in low signal-to-noise ratio environments.展开更多
基金supported in part by Natural Science Foundation of China(92367102)in part by National Science and Technology Major Project(2024ZD1300400).
文摘When deploying Reconfigurable Intelligent Surface(RIS)to improve System Sum-Rate(SSR),the timeliness and accuracy of SSR optimization methods are difficult to achieve simultaneously through a single algorithm.Some algorithms focus on timeliness,while some focus on accuracy.In this paper,in order to take into account the timeliness and accuracy of the system comprehensively,we construct SSR analysis model of RIS-assisted multiuser downlink communication system and propose several new optimization methods.The goal is to maximize SSR by using the proposed algorithms to jointly optimize power allocation and reflection coefficients.To solve this comprehensive problem,two sets of Alternating Optimization(AO)-based timeliness algorithms and one set of Monotonic Optimization(MO)-based accuracy algorithms are proposed separately to jointly optimize system performance.First,the Water-Filling(WF)-based and penalty-based low complexity algorithms are developed to optimize power allocation and reflection coefficients respectively.To improve the reality of the calculation,penalty-based algorithm cleverly considers residual noise that is difficult to calculate.Then,for further improve the timeliness,a new Successive Convex Approximation(SCA)-based low complexity algorithm is designed to further optimize reflection coefficients and its convergence is proved.Third,in order to verify the effectiveness of the proposed timeliness algorithms,we further propose MO-based accuracy algorithms,in which,the Polyblock Outer Approximation(POA)algorithm,the Semidefinite Relaxation(SDR)method,and the bisection search algorithm are combined in a novel way.Numerical results confirm the timeliness of AO-based algorithms and the accuracy of MO-based algorithms.They supervise and complement each other.
基金supported by the Open Fund Project of Key Laboratory of Ocean Observation Technology,MNR(2023klootA01).
文摘Dear Editor,As the Internet of things(IoT)and autonomous driving continue to evolve,positioning technology faces increasing demands for higher accuracy and reliability.Traditional positioning methods often struggle in complex signal environments with multipath interference and non-line-of-sight(NLOS)conditions.Reconfigurable intelligent surfaces(RIS),an innovative technology that can flexibly control signal propagation,offer new possibilities for positioning systems.
基金supported by the National Key Research and Development Program of China(2023YFB3811502)the National Science Foundation of China(62225108)+5 种基金the Fundamental Research Funds for the Central Universities(2242022k60003)the National Natural Science Foundation of China(62288101 and 62201139)the Jiangsu Province Frontier Leading Technology Basic Research Project(BK20212002)the Jiangsu Provincial Scientific Research Center of Applied Mathematics(BK20233002)the Fundamental Research Funds for the Central Universities(2242024RCB0005 and 2242024K30009)the 111 Project(111-2-05).
文摘With digital coding technology,reconfigurable intelligent surfaces(RISs)become powerful real-time sys-tems for manipulating electromagnetic(EM)waves.However,most automatic RIS designs involve exten-sive numerical simulations of the unit,including the passive pattern and active devices,requiring high data acquisition and training costs.In addition,for passive patterns,the widely employed random pixe-lated method presents design efficiency and effectiveness challenges due to the massive pixel combina-tions and blocked excitation current flow in discrete patterns.To overcome these two critical problems,we propose a versatile RIS design paradigm with efficient topology representation and a separate design architecture.First,a non-uniform rational B-spline(NURBS)is introduced to represent continuous pat-terns and solve excitation current flow issues.This representation makes it possible to finely tune con-tinuous patterns with several control points,greatly reducing the pattern solution space by 20-fold and facilitating RIS optimization.Then,employing multiport network theory to separate the passive pat-tern and active device from the unit,the separate design architecture significantly reduces the dataset acquisition cost by 62.5%.Through multistep multiport calculation,the multistate EM responses of the RIS under different structural combinations can be quickly obtained with only one prediction of pattern response,thereby achieving dataset and model reuse for different RIS designs.With a hybrid continuous-discrete optimization algorithm,three examples—including two typical high-performance RISs and an ultra-wideband multilayer RIS—are provided to validate the superiority of our paradigm.Our work offers an efficient solution for RIS automatic design,and the resulting structure is expected to boost RIS appli-cations in the fields of wireless communication and sensing.
基金supported in part by the National Key Research and Development Program of China under Grants 2023YFB3811505in part by the National Natural Science Foundation of China(NSFC)under Grants 62261160576,62201138,62301156,and 62401137+4 种基金in part by the Key Technologies R&D Program of Jiangsu(Prospective and Key Technologies for Industry)under Grants BE2023022-1 and BE2023022in part by the Natural Science Foundation of Jiangsu Province under Grant BK20220809 and BK20241281in part by the Fundamental Research Funds for the Central Universities under Grant 2242023K5003in part by the China National Postdoctoral Program for Innovative Talents under Grant BX20230065in part by the Jiangsu Excellent Postdoctoral Program under Grant 2023ZB476.
文摘Reconfigurable intelligent surface(RIS)has proven to be promising for future wireless communication.Due to its ability to manipulate electromagnetic(EM)waves,RIS provides a flexible and programmable way to implement intelligent wireless environments.While path loss modeling has been conducted in some prior research,an issue remaining unknown is the characteristics of multi-beam path loss for RIS.In this paper,we model,simulate and measure the multi-beam path loss in RIS-assisted broadcast communication scenarios.We propose two specific configurations of RIS and derive the path loss models,which reveal that the incident beam can be equally divided into multiple beams without power loss through rational design of the phase coding.The proposed path loss model is validated through simulation subsequently.To further verify our conclusions,we build a millimeter wave(mmWave)measurement system with a 35 GHz fabricated RIS.The measurement result corresponds well with the simulation,which shows a difference of about 3 dB in the received signal power of quad-beam compared with dual-beam,as well as dual-beam compared with single-beam,except for the impact of radiation patterns of the antennas and RIS elements.
基金partially supported by the National Key Research and Development Project under Grant 2020YFB1806805Science and Technology on Communication Networks Laboratorysupported by China Scholarship Council.
文摘Reconfigurable intelligent surface(RIS)is a promising candidate technology of the upcoming Sixth Generation(6G)communication system for its ability to provide unprecedented spectral and energy efficiency increment through passive beamforming.However,it is challenging to obtain instantaneous channel state information(I-CSI)for RIS,which obliges us to use statistical channel state information(S-CSI)to achieve passive beamforming.In this paper,RIS-aided multiple-input single-output(MISO)multi-user downlink communication system with correlated channels is investigated.Then,we formulate the problem of joint beamforming design at the AP and RIS to maximize the sum ergodic spectral efficiency(ESE)of all users to improve the network capacity.Since it is too hard to compute sum ESE,an ESE approximation is adopted to reformulate the problem into a more tractable form.Then,we present two joint beamforming algorithms,namely the singular value decomposition-gradient descent(SVD-GD)algorithm and the fractional programming-gradient descent(FP-GD)algorithm.Simulation results show the effectiveness of our proposed algorithms and validate that 2-bits quantizer is enough for RIS phase shifts implementation.
基金supported in part by the Shenzhen Basic Research Program under Grant JCYJ20220531103008018,20231120142345001 and 20231127144045001the Guangdong Basic Research Program under Grant 2024ZDZX1016the Natural Science Foundation of China under Grant U20A20156.
文摘Reconfigurable Intelligent Surface(RIS)is regarded as a cutting-edge technology for the development of future wireless communication networks with improved frequency efficiency and reduced energy consumption.This paper proposes an architecture by combining RIS with Generalized Spatial Modulation(GSM)and then presents a Multi-Residual Deep Neural Network(MR-DNN)scheme,where the active antennas and their transmitted constellation symbols are detected by sub-DNNs in the detection block.Simulation results demonstrate that the proposed MR-DNN detection algorithm performs considerably better than the traditional Zero-Forcing(ZF)and the Minimum Mean Squared Error(MMSE)detection algorithms in terms of Bit Error Rate(BER).Moreover,the MR-DNN detection algorithm has less time complexity than the traditional detection algorithms.
基金supported by Ministry of Science and Technology of the People’s Republic of China(2020YFB1808101)the Project“5G evolution wireless air interface intelligent R&D and verification public platform project”supported by Ministry of Industry and Information Technology of the People’s Republic of China(TC220A04M).
文摘In this paper,a physical model of RIS of bistatic polarized radar cross section is derived starting from the Stratton-Chu equations under the assumptions of physical optics,PEC,far field and rectangular RIS element.In the context of important physical characteristics of the backscattering polarization of RIS,the modeling of the RIS wireless channel requires a tradeoff between complexity and accuracy,as well as usability and simplicity.For channel modeling of RIS systems,RIS is modelled as multi-equivalent virtual base stations(BSs)induced by multi polarized electromagnetic waves from different incident directions.The comparison between test and simulation results demonstrates that the proposed algorithm effectively captures the key characteristics of the general RIS element polarization physical model and provides accurate results.
基金supported by the Joint Funds of the National Natural Science Foundation of China(No.U23A20277)the Joint Funds of the National Natural Science Foundation of China(No.U22A2003).
文摘In this paper,we propose a rate splitting multiple access(RSMA)based integrated sensing and communication system(ISAC),where the sensing and communication are realized simultaneously with the RSMA signal.Further,reconfigurable holographic surface(RHS)is utilized to replace the traditional antennas for beam generation,expecting to combine the advantages of RSMA and RHS.To maximize the weighted summation of system rate and probing power,an optimization problem is formulated to jointly design the digital beamformer,the holographic beamformer and the message splitting vectors.To solve the non-convex problem,we first decompose it into two subproblems,where one jointly designs the digital beamformer and message splitting vectors,and the other deals with the holographic beamformer.An iterative algorithm,which leverages successive convex approximation and semi-definite relaxation,is proposed to achieve the sub-optimal solution through solving these two subproblems alternatively.Simulations confirm the effectiveness and efficiency of the proposed algorithm.
基金supported in part by the National Natural Science Foundation of China under Grant 62071253,Grant 62371252 and Grant 62271268in part by the Jiangsu Provincial Key Research and Development Program under Grant BE2022800in part by the Jiangsu Provincial 333 Talent Project.
文摘In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assisted multi-antenna jamming(MAJ)scheme denoted by ARIS-MAJ to interfere with the illegal signal transmission.In order to strike a balance between the jamming performance and the energy consumption,we consider a so-called jamming energy efficiency(JEE)which is defined as the ratio of achievable rate reduced by the jamming system to the corresponding power consumption.We formulate an optimization problem to maximize the JEE for the proposed ARIS-MAJ scheme by jointly optimizing the jammer’s beamforming vector and ARIS’s reflecting coefficients under the constraint that the jamming power received at the illegal user is lower than the illegal user’s detection threshold.To address the non-convex optimization problem,we propose the Dinkelbach-based alternating optimization(AO)algorithm by applying the semidefinite relaxation(SDR)algorithm with Gaussian randomization method.Numerical results validate that the proposed ARIS-MAJ scheme outperforms the passive reconfigurable intelligent surface(PRIS)-assisted multi-antenna jamming(PRIS-MAJ)scheme and the conventional multiantenna jamming scheme without RIS(NRIS-MAJ)in terms of the JEE.
基金supported in part by the National Natural Science Foundation of China under Grants 61971126 and 61921004ZTE CorporationState Key Laboratory of Mobile Network and Mobile Multimedia Technology.
文摘In this paper,we investigate the reconfigurable intelligent surface(RIS)-enabled multiple-input-single-output orthogonal frequency division multiplexing(MISO-OFDM)system under frequency-selective channels,and propose a low-complexity alternating optimization(AO)based joint beamforming and RIS phase shifts optimization algorithm to maximize the achievable rate.First,with fixed RIS phase shifts,we devise the optimal closedform transmit beamforming vectors corresponding to different subcarriers.Then,with given active beamforming vectors,near-optimal RIS reflection coefficients can be determined efficiently leveraging fractional programming(FP)combined with manifold optimization(MO)or majorization-minimization(MM)framework.Additionally,we also propose a heuristic RIS phase shifts design approach based on the sum of subcarrier gain maximization(SSGM)criterion requiring lower complexity.Numerical results indicate that the proposed MO/MM algorithm can achieve almost the same rate as the upper bound achieved by the semidefinite relaxation(SDR)algorithm,and the proposed SSGM based scheme is only slightly inferior to the upper bound while has much lower complexity.These results demonstrate the effectiveness of the proposed algorithms.
基金supported in part by National Natural Science Foundation of China(Grant Nos.61921003,61925101,61831002 and 61901315)in part by the Beijing Natural Science Foundation under(Grant No.JQ18016)in part by the Fundamental Research Funds for the Central Universities(Grant No.2020RC08).
文摘Reconfigurable intelligent surface(RIS)can manipulate the wireless propagation environment by smartly adjusting the amplitude/phase in a programmable panel,enjoying the improved performance.The accurate acquisition of the instantaneous channel state information(CSI)in the cascaded RIS chain makes an indispensable contribution to the performance gains.However,it is quite challenging to estimate the CSI in a time-variant scenario due to the limited signal processing capability of the passive elements embedded in a RIS pannel.In this work,a channel estimation scheme for the RIS-assisted wireless communication system is proposed,which is demonstrated to perform well in a time-variant scenario.The cascaded RIS channel is modeled as a state-space model based upon the mobility situations.In addition,to fully exploit the time correlation of channel,Kalman filter is employed by taking the prior information of channels into account.Further,the optimal reflection coefficients are derived according to the minimum mean square error(MMSE)criterion.Numerical results show that the proposed methods exhibit superior performance if compared with a conventional channel estimation scheme.
基金supported in part by the National Natural Science Foundation of China under Grant U1805262,62071247,61801244,61771264in part by the Natural Science Foundation of Jiangsu Province under Grant BK20180754+1 种基金in part by the Guangdong Provincial Special Fund For Modern Agriculture Industry Technology Innovation Teams under Grant 2020KJ122in part by the Initial Scientic Research Foundation of NJUPT under Grant NY218103.
文摘In this paper,a reconfigurable intelligent surface(RIS)-assisted MIMO wireless secure communication system is considered,in which a base station(BS)equipped with multiple antennas exploits statistical channel state information to communicate with a legitimate multi-antenna user,in the presence of an eavesdropper,also equipped with multiple antennas.We firstly obtain an analytical expression of the ergodic secrecy rate based on the results of largedimensional random matrix theory.Then,a jointly alternating optimization algorithm with the method of Taylor series expansion and the projected gradient ascent method is proposed to design the transmit covariance matrix at the BS,as well as the diagonal phaseshifting matrix to maximize the ergodic secrecy rate.Simulations are conducted to demonstrate the accuracy of the derived analytical expressions,as well as the superior performance of our proposed algorithm.
基金supported in part by the National Natural Science Foundation of China under Grant 61901378,61941119,61901379in part by the Natural Science Basic Research Plan in Shaanxi Province of China under Grant 2019JQ-253+5 种基金in part by the open research fund of National Mobile Communications Research Laboratory,Southeast University under Grant 2020D04in part by China Postdoctoral Science Foundation under Grant BX20190287in part by the Aerospace Science and Technology Innovation Fund of China Aerospace Science and Technology Corporationin part by the Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2018045)in part by the China Fundamental Research Fund for the Central Universities(No.3102018QD096)in part by the Seed Foundation of Innovation and Creation for Graduate Students in Northwestern Polytechnical University(No.CX2020152).
文摘Reconfigurable intelligent surface(RIS)has been proposed as a potential solution to improve the coverage and spectrum efficiency for future wireless communication.However,the privacy of users’data is often ignored in previous works,such as the user’s location information during channel estimation.In this paper,we propose a privacy-preserving design paradigm combining federated learning(FL)with RIS in the mmWave communication system.Based on FL,the local models are trained and encrypted using the private data managed on each local device.Following this,a global model is generated by aggregating them at the central server.The optimal model is trained for establishing the mapping function between channel state information(CSI)and RIS’configuration matrix in order to maximize the achievable rate of the received signal.Simulation results demonstrate that the proposed scheme can effectively approach to the theoretical value generated by centralized machine learning(ML),while protecting user’privacy.
文摘In this paper,we survey state-of-the-art research outcomes in the burgeoning field of Reconfigurable Intelligent Surface(RIS),given its potential for significant performance enhancement of next-generation wireless communication networks by means of adapting a propagation environment.Emphasis has been placed on several aspects gating the commercial viability of future network deployment.Comprehensive summaries are provided for practical hardware design considerations and broad implications of artificial intelligence techniques,as are in-depth outlooks on the salient aspects of system models,use cases,and physical layer optimization techniques.
基金This work was supported in part by National Key Research and Development Program of China under Grant 2017YFB1010002in part by National Natural Science Foundation of China under Grant 61871455,61831013.
文摘Reconfigurable intelligent surface(RIS)is an emerging meta-surface that can provide additional communications links through reflecting the signals,and has been recognized as a strong candidate of 6G mobile communications systems.Meanwhile,it has been recently admitted that implementing artificial intelligence(AI)into RIS communications will extensively benefit the reconfiguration capacity and enhance the robustness to complicated transmission environments.Besides the conventional model-driven approaches,AI can also deal with the existing signal processing problems in a data-driven manner via digging the inherent characteristic from the real data.Hence,AI is particularly suitable for the signal processing problems over RIS networks under unideal scenarios like modeling mismatching,insufficient resource,hardware impairment,as well as dynamical transmissions.As one of the earliest survey papers,we will introduce the merging of AI and RIS,called AIRIS,over various signal processing topics,including environmental sensing,channel acquisition,beamforming design,and resource scheduling,etc.We will also discuss the challenges of AIRIS and present some interesting future directions.
文摘It is assumed that reconfigurable intelligent surface(RIS)is a key technology to enable the potential of mmWave communications.The passivity of the RIS makes channel estimation difficult because the channel can only be measured at the transceiver and not at the RIS.In this paper,we propose a novel separate channel estimator via exploiting the cascaded sparsity in the continuously valued angular domain of the cascaded channel for the RIS-enabled millimeter-wave/Tera-Hz systems,i.e.,the two-stage estimation method where the cascaded channel is separated into the base station(BS)-RIS and the RIS-user(UE)ones.Specifically,we first reveal the cascaded sparsity,i.e.,the sparsity exists in the hybrid angular domains of BS-RIS and the RIS-UEs separated channels,to construct the specific sparsity structure for RIS enabled multi-user systems.Then,we formulate the channel estimation problem using atomic norm minimization(ANM)to enhance the proposed sparsity structure in the continuous angular domains,where a low-complexity channel estimator via Alternating Direction Method of Multipliers(ADMM)is proposed.Simulation findings demonstrate that the proposed channel estimator outperforms the current state-of-the-arts in terms of performance.
基金supported in part by the Fundamental Research Funds for the Central Universities(2022JBZY018)in part by the National Science Foundation of China(NSFC)for General Program under Grant 62171021+1 种基金in part by the Project of China State Railway Group under Grant P2020G004,SY2021G001in part by Basic Research Project of Jiangsu Province Frontier Leading Technology under Grant BK20212002.
文摘With the advantage of programmable electromagnetic properties,Reconfigurable Intelligent Surfaces(RISs)havedrawn wide attention from both industry and academia.RIS-assisted communication systems can promote hugewireless channel quality improvement and remarkable coverage enhancement.This paper proposes generalpathloss model,radiation pattern and mirror beam effect of 1-bit RIS at sub-6 GHz band.Field trails have beencarried out in outdoor and indoor deployment scenarios.The proposed model is validated through extensivesimulations and field-trial measurements.In addition,an optimized RIS phase-shit design process for the mirrorbeam elimination is proposed and validated with simulations.The proposed theoretical model and measurementresults can promote future research and application in RIS-assisted communications.
基金supported by the National Natural Science Foundation of China(Grant No.61961024)the Top Double 1000 Talent Programme of Jiangxi Province(Grant No.JXSQ2019201055)+1 种基金the Natural Science Foundation of Jiangxi Province(Grant No.20181BAB202001)the Opening Project of Shanghai Key Laboratory of Integrated Administration Technologies for Information Security(Grant No.AGK201602)。
文摘To further improve the secrecy rate,a joint optimization scheme for the reconfigurable intelligent surface(RIS)phase shift and the power allocation is proposed in the untrusted relay(UR)networks assisted by the RIS.The eavesdropping on the UR is interfered by a source-based jamming strategy.Under the constraints of unit modulus and total power,the RIS phase shift,the power allocation between the confidential signal and the jamming signal,and the power allocation between the source node and the UR are jointly optimized to maximize the secrecy rate.The complex multivariable coupling problem is decomposed into three sub-problems,and the non-convexity of the objective function and the constraints is solved with semi-definite relaxation.Simulation results indicate that the secrecy rate is remarkably enhanced with the proposed scheme compared with the equal power allocation scheme,the random phase shift scheme,and the no-RIS scheme.
基金supported in part by the National Natural Science Foundation of China under Grant 62201228 and Grant 62001190in part by the Science and Technology Major Project of Tibetan Autonomous Region of China under Grant No.XZ202201ZD0006G02.
文摘Reconfigurable intelligent surface(RIS)-assisted symbiotic radio is a spectrum-and energy-efficient communication paradigm,in which an RIS performs passive beamforming to enhance active transmission,while using the electromagnetic waves from the active transmission for additional information transfer(i.e.,passive transmission).In this paper,a hybrid RIS-based modulation,termed hybrid phase and code modulation(HPCM),is proposed to improve the reliability of RIS-assisted symbiotic radio.In RIS-HPCM,the RIS simultaneously performs direct sequence spread spectrum and passive beamforming on incident signals.Moreover,both the spreading code and phase offset are exploited to carry the RIS’s own information.A low-complexity detector is designed,in which the receiver first detects the spreading codes and then demodulates the constellation symbols.We analyze the bit error rate(BER)performance of RIS-HPCM over Rician fading channels.BER upper bounds and approximate BER expressions are derived in closed-form for maximum-likelihood and low-complexity detectors,respectively.Simulation results in terms of BER verify the analysis and show the superiority of RIS-HPCM over the existing RIS-based modulation.
基金supported by National Natural Science Foundation of China(No.61801106).
文摘In this paper,a differential scheme is proposed for reconfigurable intelligent surface(RIS)assisted spatial modulation,which is referred to as RISDSM,to eliminate the need for channel state information(CSI)at the receiver.The proposed scheme is an improvement over the current differential modulation scheme used in RIS-based systems,as it avoids the high-order matrix calculation and improves the spectral efficiency.A mathematical framework is developed to determine the theoretical average bit error probability(ABEP)of the system using RIS-DSM.The detection complexity of the proposed RIS-DSM scheme is extremely low through the simplification.Finally,simulations results demonstrate that the proposed RIS-DSM scheme can deliver satisfactory error performance even in low signal-to-noise ratio environments.
