Research On Physical Layer Security Algorithm Based On OFDM System

The fourth-generation mobile communication technology has become a major communication technology in modern communication systems.OFDM?Orthogonal Frequency Division Multiplexing?technology is the mainstream technology of the fourth generation mobile communication system because of its stable signal transmission,countermeasures against frequency selective fading or narrowband interference,and high channel utilization.In wireless communication,various network informations transmitted through a wireless channel.However,the openness of the wireless channel makes the transmitted information vulnerable to eavesdropping and attacks,and therefore has a higher level of requirements for the communication speed and security performance of the system.In recent years,research in the field of information security has gradually favored the physical layer security technology,and research on physical layer security algorithms based on OFDM technology is emerging.This paper analyzes the status quo and existing problems of physical layer security mechanisms under OFDM technology and the security threats faced by wireless communication systems.It can combine deficiencies in existing physical layer security algorithms to implement OFDM modulation protection and data security at the physical layer algorithm.Firstly,the physical layer security algorithm based on key matrix is improved,and a physical layer security algorithm based on phase rotation and key matrix is studied.The algorithm introduces a diagonal key matrix M based on the OFDM system model.M encrypts the transmitted symbols with phase angle added.Theory and simulation experiments show that the algorithm has no effect on the inherent performance bandwidth and peak-to-average ratio of the system,and the BER increases the signal-to-noise ratio when demodulating the transmission signal.The normal demodulation is reduced to10^-5,and the illegal demodulation error rate value is around10^-1and the transmitted signal constellation cannot be matched by the constellation template of the existing modulation scheme.Then,the theoretical model of the artificial noise assist method and the theoretical and safety analysis of the physical layer security algorithm based on artificial noise are studied.For wireless communication systems with OFDM modulation,artificial noise signal generation is designed according to the period T of the OFDM system,the number of subcarriers N,and the frequency f.Theoretical analysis and simulation results show that the algorithm does not have a significant impact on the system's bit error rate and bandwidth,and successfully reduces the peak-to-average ratio of the original system by 1.5 dB.Finally,the physical layer security algorithm based on artificial noise and key matrix is a further improvement of the physical layer security algorithm based on phase rotation and key matrix.The encryption of the encrypted OFDM transmission signal is added manually before the channel is added noise signal protection.Theoretical analysis and experimental simulation show that the algorithm provides strong protection for physical layer information security transmission.Eavesdroppers can obtain near-system error rate when the signal-to-noise ratio is small.However,as the signal-to-noise ratio increases,the original OFDM system is The bit error rate at the eavesdropping end gradually decreases.When the signal-to-noise ratio is 18dB,the system error rate approaches 0,and the illegally demodulated bit error rate is 0.6866.At the same time,the encryption algorithm also reduces the peak-to-average ratio of the system by about 1.5 dB and further disturbs the distribution of signal constellation points.