MSE Based Precoding Design For Physical Layer Security In MIMO System

With the development of wireless communication technology,we step into information age.At the same time,with wide application of wireless network,people have a higher requirement on service quality of communication and data transmission rate.However,both the broadcast characteristics of wireless channel and the complexity and diversity of wireless network make information easier to eavesdropper.Therefore,some measures must be taken to ensure the security of information.Physical layer security makes use of the characteristics of wireless channel to improve secure performance based on information theory.This paper makes a research on MIMO wiretap channel involving relaying cooperation and precoding design to improve secure performance and prevent eavesdropper intercepting information.Achievable secrecy rate and secrecy capacity are the most common secure metric for physical layer security from the perspective of information theory illuminating the limit for secure communication.But it's difficult to find achieving coding scheme satisfying secrecy capacity in practical project due to its high computational complexity.In contrast,mean square error demonstrates the quality of communication based on the difference between estimated signal and actual signal with low calculation and simple treatment existing realizable coding design for practical application,which evaluates secure performance from estimated theory.Besides,bit error rate has a close connection with MSE,which can provide further reference for the realization of project.Nevertheless,the application of MSE is not common for physical layer security since it is a norm to use secure theory instead of estimated theory to measure security.Then this paper intends to make a link of them and figure out the relationship between achievable secrecy rate and MSE based on various models containing MIMO system with and without relay.In the case with relay,both with path from source to destination and without direct path are taken into consideration.According to the conclusion,it shows that there exits a value of signal power with which the optimization of MSE can be transformed into the optimization of achievable secrecy rate.Moreover,in the situation of low signal power,two optimal problems are equivalent.Thus,it's valuable to study estimated theory for physical layer security.In addition,in view of the advantages of MSE,this paper presents several precoding design on MSE mainly based on two ideas.One is to minimize the MSE at legitimate user while keeping MSE at eavesdropper above a bound.The other is to maximize the difference of MSE at two terminals.Besides,based on the relationship of MSE and achievable secrecy rate,the paper gives a modified precoding design,which intends to find an optimal signal power to maximize secure performance except precoding matrix.The solution of these precoding designs are similar,and the complexity of the algorithm for different models is almost coincident.Finally,the simulation and performance comparison of proposed precoding schemes are carried out,and it proves that the presented designs are not only with low computational complexity,but also with good secure performance.