Research On The Physical Layer Security Technology To Combate Multiple Eavesdroppers In Time Reversal System

In recent years,the use of the characteristics of wireless channels and the use of physical layer security technology to realize the secure transmission of confidential information is a research hotspot.The space-time focus of time reversal technology makes it natural anti-eavesdropping ability,so it is introduced into physical layer security research.At present,some researches on physical layer security based on time reversal have been carried out,but the research on the problem of multiple eavesdroppers in the time reversal system is insufficient.There are multiple eavesdroppers in the system,compared to only one eavesdropper in the system,the possibility of confidential information being eavesdrop increases.According to whether there is a connection between multiple eavesdroppers,eavesdropping by multiple eavesdroppers is divided into two situations: multiple eavesdroppers independently eavesdropping and multiple eavesdroppers collusion eavesdropping.Therefore,this thesis studies the physical layer security method against multiple eavesdroppers in the time reversal system.The main work of the thesis is as follows:1.Aiming at the problem of independent eavesdropping by multiple eavesdroppers in the wireless communication system,a physical layer security method against independent eavesdropping is proposed.This method is based on a multiple-input single-output transmission system with artificial noise-assisted time reversal technology.First,set the power allocation factor at the transmitter so that part of the power of the transmitter is used to send confidential information,and the other part of the power is used to send artificial noise;second,the closed-form expressions of connection outage probability and security outage probability are derived by using random geometry theory to characterize the reliability and security of the system of respectively;then,the reliability and security of the system are comprehensively considered to maximize the safety throughput of the system;finally,the simulation results show that the proposed method improves the secrecy throughput of the system compared with other method.2.Aiming at the problem of collusion eavesdropping in the wireless communication system,a physical layer security resistant to collusion eavesdropping in the time reversal system is proposed.This method aims at maximizing the secrecy rate of the system.When the transmission power is limited,the optimal time reversal filter and artificial noise filter are jointly designed to improve the secrecy rate of the system.In order to ensure that the non-convex optimization problem is solved,it is transformed into a two-layer optimization problem for solution.The simulation results show that this method is applicable when the transmitter is equipped with a single antenna or multiple antennas,compared with other method,the secrecy rate of the system is improved.