Secure Transmission In Wireless Relay Systems With Jamming And Multi-User Selection

In recent years,with the rapid development of wireless communication technologies,the security of information transmission has become more and more important.Traditional encryption algorithms have been unable to effectively solve the current security problems due to their limitations.Physical layer security techniques can solve the security problem of wireless communication in a new perspective.Due to three characteristics of time-varying,reciprocity and randomness of the wireless channel,information can be transmitted securely in the physical layer.The thesis studies two wireless communication system models,and uses different transmission strategies to discuss the security performance under different f ading channel conditions.The main work and contributions of the thesis are as follows:(1)Research on physical layer security technology: Firstly,the physica l layer security is summarized.Secondly,the classic eavesdropping channel model is introduced,and the security performance indicators of the system are further explained.Finally,the thesis focuses on several techniques for the physical layer security.(2)System model design and analysis for opportunistic relay selection: Using artificial noise and optimal relay selection strategy,a communication system model based on opportunistic relay selection is studied.According to this system model,the security performance indicators including system security capacity,outage probability and intercept probability are studied,and the relationship between outage probability and intercept probability is discussed.Compared with the traditional relay selection sc heme,the results show that the security capacity and system security performance of the Rayleigh fading channel are greatly improved.(3)System model design for jamming and multi-user selection: Under the Nakagami-m fading channel model,a general order selection strategy is proposed to select the destination user upon considering the influence of channel feedback delay on channel state information,and then a cooperative jamming strategy is incorporated to realize secure information transmission.(4)System performance analysis for jamming and multi-user selection: Under the conditions of known and unknown eavesdrop ping CSI,two different transmission strategies are proposed,and the corresponding exact expressions for the outage probability and the eavesdropping probability of the system are derived.The results of theoretical analysis and numerical simulations show that increasing the order parameter for user selection can improve effectively the security performance of the system.