Joint active and passive beamforming optimization for intelligent reflecting surface assisted proactive eavesdropping

Abstract

This paper investigates a three-node proactive eavesdropping system with the aid of intelligent reflecting surface (IRS), where a monitor tries to wiretap information and transmit jamming signals simultaneously to interfere with the suspicious link. The IRS is deployed around the suspicious users to reconstruct propagation channel. Meanwhile, with large low-cost passive reflecting elements, it can provide more spatial degrees of freedom to moderate the link quality. In order to degrade exposure risk of eavesdropping behavior, the authors' objective is to minimize the jamming power by carefully designing jamming beamforming vectors and the phase shifts under the constraint of reliable intercepted information. The formulated problem is non-trivial to solve due to the coupling variables and unit-modulus constraints. Fortunately, by using alternating optimization and successive convex approximation techniques, the original problem is transformed into convex form and a sub-optimal solution is achieved. Numerical results show that the proposed scheme can effectively reduce the jamming power and the number of the jamming antennas over benchmark schemes, which is quite suitable for covertly overhearing signal.

Design of a novel wireless information surveillance scheme assisted by reconfigurable intelligent surface

“…respectively. Then the effective information monitoring rate R m is given as [5][6][7][24][25][26][27]]…”

“…Let $$ R_{e}$$ and $$ R_{u}$$ denote the achievable data rate of the monitoring link from AP to the LR and the suspicious communication link from AP to the SIU, which can be expressed as $$\begin{equation} {R_e} = {\log _2}{\left({1 + {\gamma _e}} \right)} \end{equation}$$and $$\begin{equation} {R_u} = {\log _2}{\left({1 + {\gamma _u}} \right)}, \end{equation}$$respectively. Then the effective information monitoring rate $$ R_{m}$$ is given as [5–7, 24–27] $$\begin{equation} {R_m} = {\left\lbrace { \def\eqcellsep{&}\begin{array}{*{20}{c}}{R_u},\quad {\text{ if }}{R_e} \ge {R_u},\\[5pt] 0,\quad {\text{ otherwise}}{\rm {.}} \end{array} } \right.}$$…”

“…Moreover, in this paper we assume that the information monitoring party does not participate in the precoding design of the transmitter, which is different from [25] and more difficult to implement. Kindly note that although the principle of the wireless information monitoring technology assisted by RIS studied in this paper is similar to [24], the problem formulation and solution are completely different from it. Therefore, our work can be seen as a supplement to the application of the RIS in wireless information surveillance.…”

“…Inspired by [23,24], in this paper, we investigate a novel information surveillance scheme based on RIS beamforming and artificial noise jamming cooperation. Specifically, through deploying an RIS near the AP and refinely optimizing its phase shifts, two wireless transmission paths, namely AP-RIS-SIU and AP-RIS-LR links, can be established.…”

“…Moreover, in [23], the author creatively used RIS as a green jammer to attack the specified wireless communication, thus the signal power received at the attacked user can be greatly reduced. And in [24], with the goal to minimize the jamming power, the RIS assisted proactive eavesdropping was studied, which is another application of RIS in physical layer security.…”