Secrecy Performance of the Artificial Noise Assisted Broadcast Channel with Confidential Messages and External Eavesdroppers

We consider the physical layer security for the downlink system, where the confidential messages can be wiretapped by both the intended users (IUs) and the external eavesdroppers (EEs). Regularized channel inversion (RCI) precoding is adopted for multiuser communication because it can control the mutual information leakage among users. And, to enhance the secrecy performance, artificial noise (AN) is introduced to disturb external eavesdroppers. Considering the large-system regime, by using stochastic geometry, the secrecy outage probability (SOP) and mean secrecy rate for the nearest EE wiretap and the strongest EE wiretap scenarios are derived, respectively. Analytical and simulation results show that i) when the AN is adopted, the SOP exponentially decays with the number of transmission antennas, ii) in most of the power allocation case, per-user secrecy rate can be improved significantly, e.g., there is an almost 2.7 times of improvement for the particular transmission antennas number.