Analysis On The Physical Layer Security Performance Of Time-Reversal Transmission Systems

The physical layer security technology has become a hot issue in recent years.It utilizes the random time-varying property of the wireless channel to achieve reliable transmission of information security on the physical layer.Time reversal transmission technique can harvest signal energy from multiple paths,and focus the signal power on an intended space-time point.It can enhance the received signal quality of the desired user,and suppress the signal quality of the undesired user.Thanks to its characteristics of temporal compression and spatial focusing,the time reversal transmission system has the intrinsic capability of anti-eavesdropping.This thesis analyzes the physical layer security performance of time reversal transmission systems.The main works are as follows:1.The probability distributions of received signal-to-noise ratios of the legitimate user and the eavesdropper are analyzed in time reversal transmission system.The received signal-to-noise ratios of the legitimate user and the eavesdropper are first derived;then,the probability density functions and cumulative distribution functions of signal-to-noise ratios over Rayleigh channels are derived too.The simulation results show that probability distribution of received signal-to-noise ratio of the legitimate user is accurate,and the approximate processing of the probability distribution of received signal-to-noise ratio of the eavesdropper is acceptable.What is more,the results indicates that the more the number of paths is,the legitimate user can obtain higher diversity gain,however,the eavesdropper cannot get it.2.The physical layer security performance of the TR transmission system is analyzed.Based on the probability distributions of received signal-to-noise ratios of the legitimate user and the eavesdropper,the theoretical expressions of the ergodic capacities of the legitimate channel and the wiretap channel are derived.Furthermore,the achievable ergodic secrecy rate and the outage probability are derived too.What is more,the bit error rates of the legitimate user and the eavesdropper for binary phase shift keying modulation are given.The simulation results verify the correctness of the theoretical derivation.Moreover,the theoretical analysis and simulation results show that the time reversal transmission technique can be used to obtain a certain achievable secrecy rate.In addition,by appropriately reducing the spectrum efficiency of the system,the inter-symbol interference of the legitimate user can be significantly reduced,the received signal-to-noise ratio can be improved,and better receiving performance can be obtained.However,the performance improvement of the eavesdropper is not obvious.Therefore,the time reversal technique can realize the secure transmission of information.