Research On Physical Layer Security Based On Signal Pre-Overlapping

The physical layer security technology of wireless communication is to make use of the legal user have the advantage of channel to wiretap user channel,so the legal transmitter and receiver do not need to pre-share any enciphered message like secret key.However,when the legal user channel does not have the advantage,the system security rate is zero.The beamforming scheme is proposed to realize the secure communication when the legal user channel does not have channel advantage.However,the beamforming scheme needs to know the channel information between legal users and illegal users.In practical applications,it is difficult for the sender to obtain the channel information of illegal users.To solve this problem,currently paper proposes the artificial noise scheme and the random weighting scheme.These two schemes only need to obtain the channel information of legitimate users,and do not require the channel information of illegal users.However,some scholars have proposed that the artificial noise scheme has the same physical essence as the random weighting scheme,and if an eavesdropper increases the number of tappings and then establishes a MUSIC-like algorithm,the current artificial noise scheme can be broken down.In this paper,we study the reality of the artificial noise scheme,and propose a new physical layer security scheme based on the reason why it is cracked.The main research achievements are as follows:1,To cope with the security problem,we propose a physical layer security scheme based on signals pre-overlapping transmission.In our scheme,it is assumed that the legitimate user channel information is known and eavesdropper channel information is unknown.The signal pre-overlapping transmission scheme is to combine all the signals to be transmitted in a plurality of times,and then the combined signal is loaded on plurality antennas to be sent out.Before the legitimate user received aliasing signal,it can reduce the original signal by channel difference.While due to the difference of eavesdropper's channel and legitimate users channel,so the eavesdropper cannot correctly detect the original signal.The scheme of signal pre-overlapping is different from traditional signal random weighting scheme.In the signal random weighting scheme,the same signal symbol is transmitted on each antenna,and each antenna in the signal pre-overlapping scheme transmits the aliasing signal between different signal symbols.Legitimate users need to use the legitimate user's channel information to restore the aliasing of the signal,and the eavesdropper's channel information is different from legitimate users,so the eavesdropper can not restore the aliasing signal.2,At the same time,this paper presents the implementation of the signal pre-overlapping scheme in two different scenarios.In the MISO system,we will send the signal into different time periods,each time there is a vector of the transmitted signal is pre-overlapping weight matrix,different time periods on different weight matrix,which is transmitted by TDM signal;in the MIMO system,we divide the signal spectrum into different frequency bands of a transmitted signal vector pre-overlapping weight matrix are each frequency division multiplexing,we through the frequency signal transmission.In the simulation experiment,this paper analyzes the security performance of the system by the bit error rate.The simulation results show that the bit error rate of the eavesdropper is close to 0.5.Finally,the simulation results show that the proposed scheme is effective and feasible.