IRS Backscatter-Assisted Security Transmission against Proactive Eavesdropping

In this paper, we consider the IRS backscatter-assisted physical layer security, aimed at countering smart eavesdroppers capable of sending jamming signals. Specifically, the eavesdropper increases the eavesdropping rate by sending jamming signals and is able to adjust the transmission strategy according to the received beamforming. By using IRS backscatter communication, the jamming signal sent by the eavesdropper is converted into a useful signal and transmitted. By designing the beamforming of the base station and the IRS phase shift matrix, we established the original optimization problem. Since the eavesdropper's sending strategy is adjusted according to the received signal, we transform the original problem into two subproblems. In the first subproblem, we obtain the eavesdropper's transmit beamforming; in the second subproblem, we optimize the transmit beam alternately with the IRS phase shift matrix. Simulation results demonstrate the superiority of our proposed scheme.