Intelligent Reflecting Surface Aided Wireless Information Surveillance

This paper investigates a new concept of employing intelligent reflecting surface (IRS) to enhance the monitoring performance of wireless information surveillance system, where a full-duplex legitimate monitor is employed to eavesdrop the suspicious transmission from a transmitter to a receiver with the help of an IRS. Under this setup, we consider three IRS deployment strategies, where the IRS is placed near the suspicious transmitter, the suspicious receiver and the legitimate monitor, respectively. First, the monitoring rate achievable by the IRS-aided surveillance system under each deployment strategy is analyzed, which reveals that deploying the IRS near the suspicions transmitter achieves the maximum rate with an asymptotically large number of IRS reflecting elements. Next, efficient algorithms are proposed to maximize the monitoring rate by jointly optimizing the receive and jamming beamforming vectors at the legitimate monitor and the reflection coefficients at the IRS. In particular, a performance upper bound is obtained via properly characterizing the upper and lower bounds of the jamming signal power and using semidefinite relaxation (SDR), while low-complexity algorithms based on the penalty dual decomposition (PDD) framework are also presented to achieve near-optimal performance. Finally, numerical results are presented to validate our analysis as well as the effectiveness of the proposed algorithms, and useful insights are drawn.