Research On The Reliability Of Physical Layer Wireless Communication Based On Artificial Noise And Channel Degrees Of Freedom

With the continuous innovation of wireless communication technology and the continuous expansion of its applications,its related research work has attracted more and more attention.As the basis of research in this field,the research on the theory of wireless communication in physical layer is particularly important.As we all know,the biggest feature of wireless communication is its "broadcast" property,which leads to eavesdropping and interference in the process of signal transmission.Therefore,how to create useful interference to prevent eavesdropper and how to eliminate unnecessary interference to transmit efficiently has become the goal of this paper.From the two angles of "safety" and "efficiency",we study the reliability of wireless communication in physical layer,and propose and solve several key problems in related research fields.The research on security of this paper is mainly based on artificial noise.The socalled artificial noise is a useful jamming signal sent by the help node or a part of dimension of the senders' antenna.The signal is carefully designed,which only interferes with the eavesdropper channel,but has no effect on the main channel.In this way,secure communication can be achieved even if the quality of the eavesdropping channel is superior to the main channel quality.This paper focuses on three typical channels: SISOMH,MISOAN and MIMOAN.It has been found that the existing security schemes based on artificial noise have different levels of vulnerability in view of the potential hidden dangers of eavesdropping,that is,the so-called "safe blind area".Once the artificial noise falls into the "safe blind area",the whole security protocol will fail.Combined with the knowledge of matrix theory,three kinds of security vulnerabilities are analyzed in detail.Then three optimization schemes are put forward: HTPOSISOMH,VBSE-MISOAN and MBSE-MIMOAN,which successfully eliminate hidden dangers.The research of efficiency in this paper can be divided into two directions: a MIMO antenna selection algorithm based on DOF and a physical layer coding scheme that reaches the upper bound of DOF.The two directions,from the aspect of antenna selection and physical layer coding,are to achieve the purpose of high efficiency transmission.In the first direction of the discussion,this paper focuses on the antenna selection algorithm which is very popular at present.The existing antenna selection algorithm only takes into account the minimum error rate or the maximum capacity and cannot solve the increasingly prominent contradiction between the actual demand and the low communication rate.Increasing transmitter power and increasing spectrum are two solutions proposed by predecessors.However,considering the launch cost and the wireless communication environment,these two methods are impractical.Generally,the channel capacity of the MIMO system is linearly and positively correlated with the number of antennas,but the computational complexity increases with the increase of the number of antennas.In this paper,the optimal equilibrium point between performance and computational complexity is found by designing a reasonable selection of the number of candidate subsets.In the second discussion,a channel model,G-MIMO two-way relay channel,is first defined.This model can cover most of the existing relay channel models,such as MIMO-X two-way relay channel,MIMO-Y relay channel,etc.,which has great research value and high research difficulty.Then this model is divided into two categories(single relay and multiple relays)to be discussed,combined with the MIMO channel properties and the "cut-set" theory three DOF upper bound theorems are given: the upper bound of DOF theorem on G-MIMO two-way single-relay channel,the upper bound of DOF theorem on G-MIMO two-way multiple-relay series connection channel and he upper bound of DOF theorem on G-MIMO two-way multiple-relay hybrid connection channel.Because these three theorems are based on a more universality G-MIMO relay channel,it is of great use value,and the specific application examples are also given in this paper.In particular,taking G-MIMO two-way single relay channel as an example,the corresponding upper bound reachability scheme is given by combining matrix theory,physical layer network coding and signal alignment technology.The scheme is divided into two stages: the multiple-access phase and the broadcast phase.The research results show that this scheme enables each node to achieve the predefined DOF,so as to make the whole system achieve the upper bound of the total DOF and maximize the transmission efficiency.