Physical Layer Security For Cooperative Systems Over Generalized-K Fading Channels

Recently,with the continuous development and wide application of wireless communication technology,it has greatly enriched and facilitated people's life.Compared with wired communication,wireless communication technology has the characteristics of broadcast openness in the process of transmission,which easily leads to malicious eavesdropping and impersonation attacks by illegal users,and the issue of information security is also getting more and more attention.Traditional wireless communication technology guarantees the secure exchange of information through high-level encryption and authentication.The generation of secret keys requires high computational complexity to realize the encryption algorithm,which will inevitably bring additional signaling costs to the system.In addition,as wireless communication networks become more complex and diverse,the distribution and interaction of secret keys will become more and more difficult.Physical layer security technology ensures the secure transmission of data by utilizing the physical characteristics such as reciprocity and uniqueness of the underlying wireless channel,rather than merely improving computational complexity,and does not need to establish a security mechanism at the high layer,thereby reducing the system overhead.Moreover,physical layer security technology can improve the capacity of the channel and effectively interfere wiretapping by combining the time-varying characteristics of the channel with the cooperation technology and multi-antena technology,which is a new idea to solve the information security problem in the wireless communication system and has broad research space and application prospect.Channel fading affects the strength of the signal and the transmission of the signal,which can be divided into large-scale fading and small-scale fading according to the speed of power degradation.In some real scenes,large-scale fading and small-scale fading exist at the same time,and most of the existing literatures focus on specific large-scale fading or small-scale fading.The generalized K distribution studied in this thesis is a composite fading model,which can effectively simulate large-scale fading and small-scale fading in real scenes.When the transmitting end and the receiving end are far away,the security capacity of the legal channel is smaller than that of the eavesdropping channel,and the rate of the secure transmission is 0.Using relay technology between the source and the destination can effectively improve channel fading,increase capacity channel,and enhance the efficiency of wireless communication.According to the different processing signals on the node,the relay can be divided into two types: Amplify and Forward(AF)and Decode and Forward(DF).In this thesis,the amplifying and forwarding strategy is adopted,it has the characteristics of simple algorithm implementation and small delay.Based on the above content,this thesis mainly studies physical layer security for cooperative systems over generalized-K fading channels.It is assumed that two different application scenarios are the physical layer security at the cell edge and the physical layer security inside the cell,according to two scenarios,this thesis established two system models,Secure Outage Probability(SOP),Average Secrecy Capacity(ASC)and Strictly Positive Secrecy Capacity(SPSC)of the closed expression were derived to measure the performance of the systems.Finally,Monte-Carlo simulation method is used to verify the correctness of the simulation.