Reflect Beamforming Optimization for Reconfigurable Intelligent Surface Assisted Cooperative Jamming

In this letter, we propose to deploy a reconfigurable intelligent surface (RIS) along with a jammer to interfere with an illegal wireless network in a cooperative manner, where an illegal station transmits information signals to an illegal receiver. Specifically, the RIS is used to help perform jamming by reflecting the signal from the jammer and that from the illegal station, respectively. Aiming to destroy the illegal wireless transmission without being detected, we propose to optimize the RIS reflection coefficients for the sake of minimizing the signal-to-interference-plus-noise ratio (SINR) at the illegal receiver, with the constraint that the jamming power received at the illegal receiver is lower than the detection threshold. Since the formulated problem is non-convex, we propose to obtain a high-quality sub-optimal solution by applying semidefinite relaxation (SDR) followed by the Gaussian randomization method. Our numerical results show that our proposed RIS-assisted cooperative jamming (RCJ) scheme with the proposed algorithm significantly outperforms the benchmarks in terms of its SINR and computational complexity.