Research On Physical Layer Security Of Collaborative Networks Under Adaptive Eavesdropping

With the development of economy and society,on the one hand,people’s demand for communication is increasing,which makes the amount of communication data increase exponentially,the wireless services become more diversified,and terminal access network become more and more huge.On the other hand,the security requirements for information transmission are also becoming higher and higher.Wireless communication can meet people’s growing communication needs well,but because of its openness and broadcasting,information transmission is vulnerable to eavesdropping and interference by illegal eavesdroppers.Nowadays,the 5th generation(5G)communication technology is becoming more and more mature,and illegal eavesdropping technology is also developing,which poses a huge threat to the security of wireless communication.Therefore,communication security research still needs to be further in-depth study.By utilizing the dynamic characteristics of wireless channels,such as fading,noise interference and diversity,the physical layer secure communication is considered as an effective means to achieve absolute secure communication.Due to the broadcast characteristics of the transmission channel itself,the security of wireless communication takes advantage of the fading and superposition characteristics of the wireless channel.Through channel coding and signal processing technology,the physical layer security of information security transmission from the physical layer is considered to be an effective communication means to achieve absolute security communication.Aiming at the physical layer security of cooperative networks,based on relay selection and cooperative jamming techniques,this paper analyzes the different indicators of communication security performance of legitimate users in the presence of passive eavesdropping and adaptive eavesdropping respectively.The main research of this paper includes the following two aspects.1.Modeling and analyzing the multi-relay network system based on adaptive eavesdropping.Through many different designs of relay selection,using the relay coordination and collaboration node jamming technology can effectively resist tapping the signal of stealing,improve the security performance of the wireless system,put forward the optimal relay selection strategy,and random selection schemes are compared,and the safety of the two options is deduced interrupted probability(Secrecy outage probability,SOP)expression.The results show that the optimal relay selection scheme has a lower safety interrupt probability than the random selection scheme.2.Furthermore,the physical layer security performance of adaptive eavesdropping NOMA network is studied,and a new two-stage user collaboration scheme is designed.In the first phase,the remote users of NOMA network use full duplex to interfere with the intelligent eavesdroppers.At present,full-duplex technology is usually used to improve the utilization of spectrum resources and the throughput of user data.This scheme uses full duplex combined with precoding matrix to eavesdrop on interference,which can effectively reduce the quality of eavesdroppers without disturbing legitimate users.In the second stage,the near-end user can act as a relay auxiliary source,using serial interference cancellation(SIC)technology to forward the signal information of the far-end user,and decoding it at the receiving end.Considering the correlation between information receiving rate and communication requirements of different users in the system,the analytical expressions of traversing safety capacity and traversing capacity are derived respectively,and the influence of power allocation factor and cooperative transmission power among users on the performance is analyzed.In this thesis,NOMA technology,cooperative communication,relay selection,cooperative interference,serial interference elimination and other technologies are used to study the physical layer security of communication when adaptive eavesdroppers exist,and several different communication scenarios are modeled and analyzed,providing effective reference value for the design of future mobile communication system.