非理想信道状态信息下RIS辅助的安全通信

RIS-assisted Secure Communications with Imperfect CSI

利用可重构智能表面(Reconfigurable Intelligent Surface,RIS)辅助无线发射机,可提高多用户无线网络的安全传输能力。在非理想信道状态信息(Channel State Information,CSI)下提出了鲁棒波束形成优化方法来提高系统对抗干扰和窃听攻击的能力。具体地,使用RIS辅助发射机,对RIS的相位波束形成和基站的传输功率进行联合优化,在分别满足有界CSI的最坏情况速率约束和统计CSI的速率中断概率约束来最小化系统的总传输功率。由于存在CSI误差,针对有界CSI和统计CSI误差约束,分别利用S-procedure来松弛保密速率约束和大偏差不等式(Large Deviation Inequality,LDI)来松弛保密速率中断概率约束。仿真结果表明,相比于无源反射法和传统波束形成方案,该方法可分别降低约88%和93%总传输功率,同时提高约15 dBm和12 dBm的干扰容限。

The secure transmission capability of multiuser wireless networks can be improved by employing a reconfigurable intelligent surface(RIS)assisted wireless transmitter.To enhance the performance against both the jamming and eavesdropping attacks,a robust beamforming optimization problem is formulated based on the imperfect channel state information(CSI).Specifically,with a RIS-assisted transmitter,the phase beamforming of the RIS and the transmit power of the base station are jointly optimized to minimize the total transmit power of the system,while meeting the worst-case rate constraints with the bounded CSI and the rate outage probability constraints with the statistical CSI respectively.Owing to the intractability induced by the CSI uncertainty,the S-procedure is used to relax the worst-case(secrecy)rate constraints and the large-deviation inequality(LDI)to relax the(secrecy)rate outage probability constraints.Numerical simulations demonstrate the proposed schemes can reduce up to about 88%and 93%total transmit power and improve about 15 dBm and 12 dBm jamming margin compared with the passive reflector method and the conventional beamforming scheme respectively.