The Study Of Physical Layer Security Based On Artificial Noise

Due to the broadcast nature of the wireless medium, the illegal users can eavesdrop the information which is confidential between the legitimate users. So how to ensure the security of the wireless communication system has become an important problem. Different from the traditional encryption technique which is based on the cryptography, physical layer security technology establish secure communication using the characteristic of the physical channel, without relying on encryption at the upper layer stack. The physical layer security can prevent eavesdropper obtaining the information at the physical layer by using transmission technology, it has become a hot topic in the recent research about wireless communication security. Beamforming and artificial noise are two important methods to ensure the security of the physical layer and secure communication. This paper mainly studies secure communication in two kinds systems which are MISO system with multiple eavesdroppers and cooperative relays system. The research in this paper focus on generating artificial noise to ensure the physical layer security under two systems. The main work and innovations in this paper are summarized as follows:1、Considering MISO system with existing multiple passive eavesdroppers, and the positions of eavesdroppers obey Poisson point process, we focus on enhancing security performance of MISO system via using artificial noise. Due to the condition that the information of eavesdroppers’location and their channel state information is unknown, secrecy outage probability is adopted to describe the secrecy performance. The transmitter transmits information signal through beamforming to the legitimate receiver, along with artificial noise. By designing the antenna array weight, the artificial noise is located in the null space of the main channel to confuse the eavesdroppers. The proposed method reduce the secrecy outage probability effectively. Stochastic geometry theory is adopted in the process of deriving secrecy outage probability. Based on secrecy outage probability, security region is used from the perspective of space to illustrate the security. The simulation result has shown that by generating artificial noise can improve the secrecy performance of MISO system significantly.2、Considering the scenario that cooperative relays system with one eavesdropper, maximizing secrecy capacity of the cooperative relays system is studied, and in this paper we propose a method that adding artificial noise in both stage of collaborative communication. In the process of the designing artificial noise, using different nodes to produce artificial noise in different collaboration stages. In the first stage, generating artificial noise by the antenna of receiver, it can save an additional jamming relay. In the second stage, using relay nodes collaboratively send artificial noise. Secrecy capacity is adopted to describe the secrecy performance of the cooperation relays system. With the total power constraint and the individual power constraint, we joint design beamforming vector and artificial noise to maximize the secrecy capacity of the system. Using the theory of convex optimization to solve the problem mode and get the optimal solution, and propose two-level and semi-definite programming optimization method. From the simulation result, we can observe that adding artificial noise in two stages of collaborative communication can improve the secrecy capacity of the cooperative relay systems obviously.