Secrecy Rate Enhancement Technology In Untrusted Relay Networks

In recent years,many scholars have conducted new technology research in order to solve the security problem of physical layer communication,cooperative relay,cooperative jamming(CJ)and beamforming technologies are effective methods to the security problem.The research on secrecy rate enhancement technology of untrusted relay networks based on destination assisted jamming(DAJ)is studied in this paper,along the main line of "single antenna?multiantenna?multi-relay",we focus three aspects as follow:(1)The optimal energy allocation question is discussed in energy harvesting untrusted relay network.A secure transmission scheme based on DAJ technology is designed for untrusted relay network.Considering that the untrusted relay has the capability of harvesting energy from source and destination which can maintain its long-term communication.Then,we propose a communication scheme based on energy allocation,analyze the expression of the system's secrecy rate,and establish the optimal model of maximizing the secrecy rate.The power allocation factors that maximizes the secrecy rate is obtained by adopting the joint derivative iterative optimization algorithm.Finally,we simulate and analyze the factors that affect the secrey rate,the results show that there exists power allocation factors which can maximizes the secrecy rate.(2)The precoding and power allocation techniques are designed for multi-antenna untrusted relay network.Multiple input multiple output(MIMO)technology is introduced into untrusted relay networks,which use the degrees of freedom to joint optimization of precoder and power allocation,and an optimization model is established to maximize the secrecy rate with total power constraints.An iterative solution scheme of precoding matrix and power allocation factors are designed to solve the complex optimization problems.Firstly,the generalized singular value decomposition(GSVD)is used to decompose the effective channel,and the precoding matrix at the source and the destination are obtained.The confidential signal and cooperative jamming signal are effectively focused to maximize the system's secrecy rate under the given power allocation factors.Then,an iterative algorithm is proposed to jointly optimize the precoding matrix at the source and two power allocation factors.By comparing the precoding matrix scheme with random beamforming and equal power beamforming scheme,the simulation results show that the proposed scheme has higher system's secrecy rate.(3)A joint beamforming alignment and optimal power allocation scheme is proposed for multiuntrusted relay transmission networks.In order to prevent information from being eavesdropped,DAJ technology is adopted and power allocation between confidential signal and jamming signal is studied.On this basis,relay selection scheme based on system's secrecy rate is studied.Then,for three application scenarios,including source or destination or both of them are equipped with large-scale antennas,the closed expression is given to evaluate the system's egodic secrecy rate(ESR)and secrecy outage probability(SOP).Finally,the simulation results show the superiority of the proposed scheme.Meanwhile,it is also found that the system performance can be improved by increasing the number of untrusted relay.