Enhancing physical-layer security in MISO wiretap channel with pilot-assisted channel estimation: Beamforming design for pilot jamming

In this paper, we tackle the physical-layer security issue in MISO wiretap channel considering the pilot-assisted channel estimation at the receiver side. Unlike the conventional schemes, we introduce the cooperative jamming scheme that transmits artificial noise (AN) only on downlink pilot transmission phase. In order to disrupt the channel estimation at the eavesdropper (Eve) effectively, an optimal beamforming at the cooperative jammer (CJ) was obtained by means of difference-of-convex (DC) algorithm and rank relaxation. In addition, with focus on the energy budget limitation issue at the CJ, energy efficiency at the CJ is verified based on the circuit power consumption model. Numerical results provide a performance comparison with a conventional scheme, which transmits AN only in data transmission phase.