Research On OFDM Physical Layer Security Technology Based On Wireless Channel Characteristics

In recent years,with the penetration of wireless communication devices into people's lives,the security problems caused by the openness of wireless communication can't be ignored.Wireless communication channel has the characteristics of reciprocity,uniqueness,fast time-varying and unpredictability,which makes it possible to dynamically generate keys for encrypting plaintext and realize the "one-time-one-encryption" encryption system,thus realizing unconditional security.In this paper,the security transmission technology of OFDM physical layer based on wireless channel characteristics is studied.The inconsistency rate,key generation rate and randomness of key generation method are analyzed.The peak-to-average ratio and bit error rate of OFDM physical layer security transmission system are studied.The main research work is as follows:(1)This paper analyses the current situation of key generation based on channel eigenvalues at home and abroad,and expounds the problems and difficulties of physical layer encryption.Three existing key generation methods are deeply analyzed,including double threshold quantization key generation method,cross-layer key generation method(LCA)and multi-bit adaptive key generation method(MAQ).The simulation results show that the double threshold quantization algorithm can guarantee the randomness of the key,but the key generation rate is not high.The LCA key generation method adopts m window screening mechanism to reduce the key inconsistency rate significantly,but the MAQ quantization algorithm is not high.It greatly improves the key generation rate,but at the cost of reducing the key consistency rate.(2)On the basis of research(1),aiming at the disadvantage of high key inconsistency rate of MAQ algorithm,an improved MMAQ algorithm is proposed.On the basis of MAQ key generation method,an m-window mechanism is introduced and a KLT transform is added to decorrelate the key.This method makes the same quantization interval larger than or equal to m continuous eigenvalues to generate an effective eigenvalue.The method is simple.KLT transform can also effectively remove the correlation between keys.The experimental results show that the improved algorithm effectively improves the key generation rate while guaranteeing the low key inconsistency rate,and the generated key remains random.(3)The secure encryption transmission technology in physical layer is studied,and a secure transmission method in physical layer of OFDM based on wireless channel characteristics is proposed.In traditional OFDM communication system,two encryption steps,phase modulation and key matrix,are added.After two encrypted OFDM systems,theoretical simulation analysis shows that this method effectively improves the security of the system,but has no effect on the inherent performance bandwidth and PAPR of the system.