The reconfigurable intelligent surface(RIS),which is composed of multiple passive reflective components,is now considered as an effective mean to improve security performance in wireless communications,as it can enhan...The reconfigurable intelligent surface(RIS),which is composed of multiple passive reflective components,is now considered as an effective mean to improve security performance in wireless communications,as it can enhance the signal of legitimate users and suppress the power leakage at eavesdroppers by adjusting signal phases.In this paper,we maximize the downlink ergodic secrecy sum rate of a RIS-aided multi-user system over Rician fading channels,where we assume that only imperfect channel state information(CSI)is available at the base station(BS).Firstly,we obtain the deterministic approximate expression for the ergodic secrecy sum rate by resorting to the large-system approximation theory.Then the problem is formulated to maximize the downlink ergodic secrecy sum rate by optimizing the regularization coefficient of regularized zero-forcing(RZF)precoding and the phase-shifting matrix of the RIS.By using the particle swarm optimization(PSO)method,we propose an alternate optimization(AO)algorithm to solve this non-convex problem.Finally,the numerical simulations illustrate the accuracy of our large-system approximate expression as well as the effectiveness of the proposed algorithm.展开更多
针对双向多天线中继系统中信息易被窃听的问题,提出了两种安全波束成形方案:安全和速率最大化波束成形(secrecy sum rate maximization beamforming,SSRMB)与零空间波束成形(null space beamforming,NSB).SSRMB方案中,采用具有收敛特性...针对双向多天线中继系统中信息易被窃听的问题,提出了两种安全波束成形方案:安全和速率最大化波束成形(secrecy sum rate maximization beamforming,SSRMB)与零空间波束成形(null space beamforming,NSB).SSRMB方案中,采用具有收敛特性的连续凸估计策略,对非凸的安全和速率最大化问题进行求解,得到局部最优波束成形解.针对中继节点的天线个数大于窃听节点个数这一特殊场景,设计了低复杂度NSB方案,将中继转发的信息投影到等效窃听信道矩阵的零空间中,通过求解一个广义Rayleigh熵问题获得波束成形解.仿真结果表明,所提方案可以有效地提高系统的安全性能,SSRMB方案具有快速收敛特性.展开更多
基金the National Natural Science Foundation of China.92067201the National Natural Science Foundation of China.62071247+2 种基金the National Natural Science Foundation of China.62171240the National Natural Science Foundation of China.62171231Jiangsu Provincial Key Research and Development Program.BE2020084-4
文摘The reconfigurable intelligent surface(RIS),which is composed of multiple passive reflective components,is now considered as an effective mean to improve security performance in wireless communications,as it can enhance the signal of legitimate users and suppress the power leakage at eavesdroppers by adjusting signal phases.In this paper,we maximize the downlink ergodic secrecy sum rate of a RIS-aided multi-user system over Rician fading channels,where we assume that only imperfect channel state information(CSI)is available at the base station(BS).Firstly,we obtain the deterministic approximate expression for the ergodic secrecy sum rate by resorting to the large-system approximation theory.Then the problem is formulated to maximize the downlink ergodic secrecy sum rate by optimizing the regularization coefficient of regularized zero-forcing(RZF)precoding and the phase-shifting matrix of the RIS.By using the particle swarm optimization(PSO)method,we propose an alternate optimization(AO)algorithm to solve this non-convex problem.Finally,the numerical simulations illustrate the accuracy of our large-system approximate expression as well as the effectiveness of the proposed algorithm.
文摘频谱资源短缺成为制约移动通信发展的关键瓶颈,非正交多址接入(Non-orthogonal Multiple Access,NOMA)技术具有较高的频谱效率,成为5G领域关键技术之一。从物理层安全角度出发,研究了多输入多输出(Multiple Input Multiple Output,MIMO)NOMA系统的安全问题,在满足用户最小服务质量需求(Quality of Service,QoS)条件下,构建基于最优能量分配的安全和速率(Secrecy Sum Rate,SSR)最大化的优化方程,推导出能量分配系数闭合表达式。实验结果表明,随着基站发射功率的增大或在一定程度上增加接收用户的接收天线,系统的安全性能会有所改善。
文摘针对双向多天线中继系统中信息易被窃听的问题,提出了两种安全波束成形方案:安全和速率最大化波束成形(secrecy sum rate maximization beamforming,SSRMB)与零空间波束成形(null space beamforming,NSB).SSRMB方案中,采用具有收敛特性的连续凸估计策略,对非凸的安全和速率最大化问题进行求解,得到局部最优波束成形解.针对中继节点的天线个数大于窃听节点个数这一特殊场景,设计了低复杂度NSB方案,将中继转发的信息投影到等效窃听信道矩阵的零空间中,通过求解一个广义Rayleigh熵问题获得波束成形解.仿真结果表明,所提方案可以有效地提高系统的安全性能,SSRMB方案具有快速收敛特性.
