Research Of Transmission Techniques In Physical Layer Security Based On Signal Encryption

The development of wireless communication system brings a better experience for us in many aspects.But we can not ignore the security of communication.Due to the open nature of wireless communication and broadcasting,it becomes easier for eavesdroppers to get the signal's frequency,bandwidth and modulation type,which makes the physical layer becoming a weaker link.Wireless physical layer security exploits the physical characteristic of the wireless channel to achieve secure communications,such as the randomness,difference,reciprocity and so on.This paper mainly focus on the following two aspects based on the technique of the physical layer security.First,the security of traditional wireless communication mainly implemented in the upper-layers,which cannot achieve the protection of the modulation type and physical layer information.However,wireless physical layer security exploits the physical characteristics of the wireless channel to achieve secure communications.An efficient physical layer encryption algorithm was proposed in this paper employing Latin rectangle based on 3D Lorenz map aiming to scramble the constellation map.The algorithm makes the most of the properties of modulation in complex field,which attains a lager secret-key space than Boolean algebra field.We studied the security of the proposed algorithm in terms of theoretical analysis,randomness tests using NIST(National Institute of Standards and Technology),key space,key sensitivity and the recognition of modulation type.Compared to the existing physical layer cryptosystems,the proposed method achieves higher security with less calculation and the security of the proposed method is verified through different tests.Both theoretical analysis and simulation results show that on the premise of ensuring the reliability,the proposed method can enhance the system security effectively.Second,A new physical layer encryption method based on Subcarrier-index modulation(SIM)is proposed for OFDM(Orthogonal Frequency Division Multiplexing)systems.The information bits are carried by both active subcarriers and the index patterns of subcarriers.This method adds an additional dimension to the conventional two-dimensional(2-D)amplitude/phase modulation(APM)techniques.For security,the index patterns of the carriers are disturbed by a chaotic sequence,and the constellations of the symbols transmitted on the active subcarriers are rotated.Both analytical and simulation results show that the proposed method offers not only high security but also higher reliability and efficiency than conventional OFDM: a gain of 1~3dB in bit error performance(BER)while using the same transmit power per OFDM symbol.Finally,the studies of the research are concluded and based on this,we point out the techniques to be improved and the orientation of the further research on the.physical layer encryption.