Performance of Covert Surveillance in Jamming-Aided Eavesdropping System with Channel Uncertainty

A wireless legitimate surveillance system is studied for a proactive eavesdropping scheme, where a full- duplex legitimate monitor eavesdrops a suspicious link by injecting artificial noise (AN) towards the suspicious receiver. Different from the existing work, the suspicious receiver is assumed to be capable of detecting the presence of AN. Once such receiver detects the AN, it stops transmission. Hence, to improve the surveillance performance, AN should be transmitted covertly with low detection probability by the suspicious receiver. To achieve this goal, an optimal problem is first formulated to maximize the eavesdropping rate under covert constraint. Then, according to the derived detection error probability, the optimal detection threshold is determined under Rayleigh fading channels. A novel scheme is proposed to solve the optimization problem under both perfect and imperfect channel state informations (CSIs). Finally, simulation is performed to verify the analyses. It is shown that the imperfect CSI of the suspicious link can benefit the surveillance performance.