This paper,from the view of a defender,addresses the security problem of cyber-physical systems(CPSs)subject to stealthy false data injection(FDI)attacks that cannot be detected by a residual-based anomaly detector wi...This paper,from the view of a defender,addresses the security problem of cyber-physical systems(CPSs)subject to stealthy false data injection(FDI)attacks that cannot be detected by a residual-based anomaly detector without other defensive measures.To detect such a class of FDI attacks,a stochastic coding scheme,which codes the sensor measurement with a Gaussian stochastic signal at the sensor side,is proposed to assist an anomaly detector to expose the FDI attack.In order to ensure the system performance in the normal operational context,a decoder is adopted to decode the coded sensor measurement when received at the controller side.With this detection scheme,the residual under the attack can be significantly different from that in the normal situation,and thus trigger an alarm.The design condition of the coding signal covariance is derived to meet the constraints of false alarm rate and attack detection rate.To minimize the trace of the coding signal covariance,the design problem of the coding signal is converted into a constraint non-convex optimization problem,and an estimation-optimization iteration algorithm is presented to obtain a numerical solution of the coding signal covariance.A numerical example is given to verify the effectiveness of the proposed scheme.展开更多
Programmable metasurfaces are revolutionizing the field of communication and perception by dynamically modulating properties such as amplitude and phase of electromagnetic(EM)waves.Nevertheless,it is challenging for e...Programmable metasurfaces are revolutionizing the field of communication and perception by dynamically modulating properties such as amplitude and phase of electromagnetic(EM)waves.Nevertheless,it is challenging for existing programmable metasurfaces to attain fully independent dynamic modulation of amplitude and phase due to the significant correlation between these two parameters.In this paper,we propose a radiation-type metasurface that can realize radiation space-time coding of the joint amplitude-phase.Hence,independent and arbitrary modulation of amplitudes and phases can be achieved for both x-polarized and y-polarized EM waves.For demonstration,the dynamic beam scanning with ultra-low sidelobe levels(SLLs)is validated.Moreover,we propose a strategy of stochastic coding and non-uniform modulation to suppress the harmonic energy,thereby obtaining the ultra-low sideband levels(SBLs).Prototypes were fabricated and measured,and all simulations and measurements demonstrated the superiority of the proposed strategy.In addition,the proposed strategy is optimization-free and highly integrated,which has unrivaled potential in the field of compact communication systems and radar systems.展开更多
基金supported by the National Natural Science Foundation of China under Grant Nos.61925303,62088101,U20B2073,61720106011,and 62173002the National Key R&D Program of China under Grant No.2018YFB1700100the Beijing Natural Science Foundation under Grant No.4222045。
文摘This paper,from the view of a defender,addresses the security problem of cyber-physical systems(CPSs)subject to stealthy false data injection(FDI)attacks that cannot be detected by a residual-based anomaly detector without other defensive measures.To detect such a class of FDI attacks,a stochastic coding scheme,which codes the sensor measurement with a Gaussian stochastic signal at the sensor side,is proposed to assist an anomaly detector to expose the FDI attack.In order to ensure the system performance in the normal operational context,a decoder is adopted to decode the coded sensor measurement when received at the controller side.With this detection scheme,the residual under the attack can be significantly different from that in the normal situation,and thus trigger an alarm.The design condition of the coding signal covariance is derived to meet the constraints of false alarm rate and attack detection rate.To minimize the trace of the coding signal covariance,the design problem of the coding signal is converted into a constraint non-convex optimization problem,and an estimation-optimization iteration algorithm is presented to obtain a numerical solution of the coding signal covariance.A numerical example is given to verify the effectiveness of the proposed scheme.
基金National Key Research and Development Program of China(SQ2022YFB3806200)National Natural Science Foundation of China(52272101)+1 种基金Natural Science Foundation of Shaanxi Province(2024JC-YBMS-462,2024JC-YBMS-518,2024JC-YBQN-0721)Science and Technology Innovation Team of Shaanxi Province(2023-CX-TD-48)。
文摘Programmable metasurfaces are revolutionizing the field of communication and perception by dynamically modulating properties such as amplitude and phase of electromagnetic(EM)waves.Nevertheless,it is challenging for existing programmable metasurfaces to attain fully independent dynamic modulation of amplitude and phase due to the significant correlation between these two parameters.In this paper,we propose a radiation-type metasurface that can realize radiation space-time coding of the joint amplitude-phase.Hence,independent and arbitrary modulation of amplitudes and phases can be achieved for both x-polarized and y-polarized EM waves.For demonstration,the dynamic beam scanning with ultra-low sidelobe levels(SLLs)is validated.Moreover,we propose a strategy of stochastic coding and non-uniform modulation to suppress the harmonic energy,thereby obtaining the ultra-low sideband levels(SBLs).Prototypes were fabricated and measured,and all simulations and measurements demonstrated the superiority of the proposed strategy.In addition,the proposed strategy is optimization-free and highly integrated,which has unrivaled potential in the field of compact communication systems and radar systems.
