OQAM/FBMC Physical Layer Encryption Based On Intrinsic Interference Utilization

As the evolution technology of Orthogonal Frequency Division Multiplexing(OFDM),the Filter Bank Multicarrier with Offset Quadrature Amplitude Modulation(OQAM/FBMC)technology introduces a prototype filter with excellent time-frequency focusing characteristics on each subcarrier to generate low sidelobe signal waveforms,and not need to add a cyclic prefix.Due to the above advantages,OQAM/FBMC is considered a promising multicarrier modulation technology in future mobile communications.However,the natural broadcasting characteristics of wireless communication make it possible for anyone to receive the signal within the transmission range of the transmitter and try to demodulate it,which leads to the threat of eavesdropping and jamming in the OQAM/FBMC wireless communication system.Therefore,it is of great significance to research OQAM/FBMC physical layer encryption technology to ensure its transmission security.In response to the above problems,this paper proposes an OQAM/FBMC symbol encryption method and placement design using complex symbols as encryption keys.First of all,this thesis analyzes the symbol reconstruction effects of the real and imaginary parts of the encrypted symbols on legitimate users and illegitimate users,respectively.Then,this paper proves that for any prototype filter of the OQAM/FBMC system,when the difference between the subcarrier and the symbol index is an even number,the intrinsic interference factor is always zero.Based on the above characteristics,this paper proposes a placement design of encryption symbols,which can encrypt all OQAM symbols at the same time and realize convenient decryption at legitimate users.Finally,this thesis theoretically analyzes the symbol error rate(SER),the average power of the transmitted signal and the calculation overhead of the method.The simulation results verify the effectiveness of the theoretical analysis and prove that the proposed method is superior to the method based on imaginary encryption symbols in the average power and SER performance of the transmitted signal of legitimate and illegitimate receivers.In order to further improve the transmission quality of legitimate users in the proposed physical layer encryption method,this paper first analyzes the interference caused by channel estimation errors to legitimate users.Then,this paper analyzes and finds that legitimate users based on traditional channel estimation method will be greatly affected by the power of data symbols during the channel estimation process.In response to this problem,this paper proposes a pilot sequence and channel estimation method,which eliminates the interference of surrounding data symbols and has more pseudo pilot power on half of the subcarriers.Simulation shows that compared with legitimate users based on traditional channel estimation method,the proposed method has obvious advantages in both SER and MSE performance.