IRS-Enabled Physical Layer Secure Transmission

Due to the broadcast nature of multi-hop channels, the information security of intelligent reflecting surface (IRS) assisted wireless communication remains an open issue to be resolved, which is even more urgently in the case that the passive eavesdropper is directly linked with the transmitter of a single-input single-output (SISO) transmission system. To deal with this, in this paper, we propose a transmitter perturbation injection and IRS reflection based physical-layer security scheme, such that the secure transmission of wireless SISO can be guaranteed comprehensively no matter the reflection based jamming from IRS to the eavesdropper is blocked or not. Upon considering this, two different eavesdropping scenarios, which are referred to as the ideal and worst eavesdropping, are considered and investigated. In addition, we propose element-wise and group-wise phase-alignment based reflection strategies respectively, so as to attain different trade-offs between the achievable performance and implementation complexity. In order to evaluate the achievable performance limits, we analyze the ergodic secrecy rate (ESR) of the proposed system. Simulation and numerical results verify the accuracy of performance evaluations. Finally, the effectiveness of our proposed secure transmission scheme is demonstrated by comparing the ESR performance achievable by it with that by the random-phase reflection based counterpart.