Minimization of Secrecy Outage Probability with Artificial-Noise-Aided Beamforming for MISO Wiretap Channels

The problem of optimal power allocation between the information-bearing signal and the artificial noise (AN) signal is addressed in this letter to enhance the physical layer security of the multiple-input-single-output wiretap channel. Differing from the existing works concerning the secrecy rate maximization, this letter studies the problem of minimizing the secrecy outage probability given the secrecy rate, where the channel state information concerning the eavesdropper is modeled as quasi-static Rayleigh fading and only known statistically. After formulating the problem as an optimization problem of power allocation, we prove that the optimal solution can be conveniently obtained by using the method of bi-section search. Simulation results show that the proposed power allocation method is efficient and can enhance the physical layer security by reducing the secrecy outage probability.