Proactive Eavesdropping via Jamming in Cognitive Radio Networks

This paper considers a proactive eavesdropping problem, in which a full-duplex legitimate monitor aims to eavesdrop on a suspicious communication link between the secondary pairs in a cognitive radio (CR) network via jamming. For such a scenario, the jamming signals would not only disrupt the suspicious receivers, but also influences the interference received at the primary receiver, which both destroy the transmitting rate in the suspicious link. Hence, the design of the beamforming should have good tradeoff between those two affects. We aim to maximize the eavesdropping rate by designing the jamming beamforming under the transmitting power (TP) constraint at the legitimate monitor and the interference temperature (IT) constraint at the primary receiver, which is a non-convex problem. Specifically, several cases are discussed to decompose the original problem and a closed-form solution is finally presented by solving two sub-problems. In particular, some analyses on the main parameters (the maximum power at the legitimate monitor and the interference temperature at the primary receiver) are undertaken to obtain their boundaries corresponding to different modes of the optimal vector, which influence the performance of the system. Numerical results are finally presented to demonstrate the performance of our proposed schemes outperforms the reference solutions.