Reaserch On The Physical Layer Security Technology Based On Multi-carrier

With the explosive growth of transmission data in wireless communications,spectrum resources have become increasingly scarce.The introduction of multi-carrier technology has increased the spectrum utilization efficiency.Therefore,multi-carrier technology is widely adopted in wireless conmmunication.Meanwhile,due to the characteristics of openness and universality of wireless communication media,the security of wireless communication becomes a public concern.The basic idea of the physical layer security technology is to use the uniquencess of the wireless channel,then take physical layer techniques to ensure secure communication.Therefore,multi-carrier based physical layer security technology is one of the most important technologies to provide the security of wireless communication.Orthogonal frequency division multiplexing(OFDM),as a typical multi-carrier technology,has the advantages of high spectral efficiency and resistance to frequency selective fading.Sparse code multiple access(SCMA)provides massive connections and high spectrum utilization.We combine SCMA and OFDM,and uses OFDM to modulate SCMA signals to get SCMA-OFDM signals.The combined system is called SCMAOFDM system.We researche the physical layer security technology of SCMA-OFDM system.The work arrangement is as follows:First of all,partial transmit sequence(PTS)and modified partial transmit sequence based on cyclic shift(MPTS)can both suppress the peak-to-average power ratio(PAPR)of the modulate signal.Besides,MPTS can be used to achieve physical layer security.Therefore,this paper uses the MPTS algorithm to enhance the security of the SCMAOFDM system and to reduce PAPR.In the proposed security model,by studying the decrypted complexity of the eavesdropper and the error curve with or without prior information,the security effect provided by MPTS is investigated.The simulation results show that even if eavesdropper has no prior information,a very small part of the information of legal users can still be recovered.Thus,the security that MPTS provided for the SCMA-OFDM system is not good enough.To adderss these problems,we further develop a noval physical layer security technology that combines interleaver and MPTS algorithm to improve the security performance of SCMA-OFDM system.The channel information and chaotic mapping are used to generate the interleaver and some parameters of MPTS.Then,according to the proposed security model,the security performance of the interleaver and MPTS in the case of multiple attack models are analyzed.Finally,the error performance of the eavesdropper with or without prior information is simulated.The results indicate that the proposed technique where MPTS is combined with an interleaver can significantly increase the eavesdropper's error rate,compared with the case when only MPTS is considered.