Correlation-based power allocation for secure transmission with artificial noise

We examine for the first time the impact of transmitter-side correlation on the secure transmission with artificial noise (AN), based on which a new power allocation strategy for AN is devised for physical layer security enhancement. Specifically, we design a correlation-based power allocation (CPA) for AN, of which the optimality in terms of achieving the minimum secrecy outage probability is analytically proved in the large system regime with the number of transmit antennas approaching infinity. Our numerical results demonstrate that CPA is nearly optimal and can significantly outperform the widely-used uniform power allocation (UPA) even for a moderate (finite) number of correlated transmit antennas. Our numerical results also reveal a fundamental difference between the secrecy performance of CPA and that of UPA. When the number of correlated transmit antennas increases, we find that the secrecy outage probability of CPA always reduces while the secrecy outage probability of UPA suffers from a saturation point.