Artificial-noise-aided communication in the presence of an active eavesdropper with a cooperative jammer

In this paper, we investigate the performance of artificial noise (AN) assisted secure communication in the presence of an active eavesdropper, who selects a jammer to assist eavesdropping. An approximate closed-form expression for the secrecy rate is derived firstly. Then we consider the practical scenario where Alice aims to allocate considerable power to the AN under the target Quality of Service (QoS) of the legitimate link. While Eve tries to compel Alice to reduce the AN by selecting an optimal helper to transmit jamming signals to Bob. To solve the conflict, we formulate a game-theoretic model between Alice and Eve. Nash equilibriums, including the minimum power allocation factor, the jammer's optimal position and jamming power are proved to exist and then analytically derived. An iterative algorithm is also proposed to obtain the optimal solution. Finally, simulation results are provided to verify our analytical results.