Abstract
Recently, the use of artificial noise has attracted considerable attention in enhancing the physical-layer security of wireless systems. However, the interaction between artificially generated noise and the inherent network interference can significantly affect the level of secrecy. In this paper, we consider the additional secrecy enhancement with artificial noise and secrecy protected zone in the presence of eavesdroppers and interferers with unknown locations. Specifically, we derive the secrecy transmission rate and investigate the relationship between artificial noise and various system parameters like secrecy protected zone radius and intensity of interferers and eavesdroppers on the secrecy transmission rate. In interference-limited networks, we derive the optimal power allocation between the information-bearing signal and artificial noise to maximize the achievable secrecy transmission rate subject to connection and secrecy outage probabilities. Numerical results show that artificial noise is still beneficial in the presence of inherent network interference to improve secrecy transmission rate and provide rules of thumb to quantify when optimal power allocation is useful.