Research On Polar Code OFDM System Based On Chaotic Encryption

As the bandwidth and capacity requirements of communication networks increase,Orthogonal Frequency Division Multiplexing Passive Optical Network?OFDM-PON?is considered an effective deployment solution.However,the transmission of optical OFDM?OOFDM?systems has security risks.For example,downstream data in OFDM-PON has signal security problems due to its broadcast architecture;leakage of optical fiber signals may cause signals to be illegally stolen.In order to prevent data from being eavesdropped by illegal users,secure transmission of optical OFDM systems is an very important issue to be solved.Simultaneously,how to improve the error performance of the OOFDM system and improve the reliability of the system under low complexity is also an important issue that has long been concerned.Based on the above problems,this paper uses chaotic encryption technology to encrypt the physical layer in the OOFDM system to improve security,and designs a suitable encryption algorithm to provide a large enough key space.Simultaneously,using Polar code as a forward error correction code?FEC?technology,the channel error is improved by channel coding,then the theoretical analysis and performance comparison analysis are carried out.The simulation results show that the proposed scheme effectively improves the security of the physical layer and significantly improves the error performance of the system.At the same time,it has low complexity and is very easy to realize.It has theoretical reference for the future large-scale optical fiber data transmission.Practical application significance.The main research work of this paper is as follows:First,we have designed a chaotic encryption scheme based on polar code.Chaotic source is a two-dimensional Henon map,and the polar code is used to encode the original data.The architecture of OFDM-PON system based on polar code is expounded.The characteristics of chaotic encryption system are also analyzed.The simulation transmission passes through a single-mode fiber modulation direct detection?IM/DD?system with a length of 60 km,and it can achieve⁷.4 dB gain at the BER of10^-3.The results show that the system can improve the safety performance and BER performance.Second,a dual domain encryption scheme based on hyperchaotic system is proposed.A Chebyshev map and four-dimensional Qi hyperchaotic system are used.The transmission system is encrypted by information bit index scrambling in polar coding and time-frequency domain encryption.The OFDM-PON direct detection system with a fiber transmission length of 40km was built by simulation.It can achieve⁶.5 dB gain at the BER of10^-3 and the key space is about 10⁷⁵.It successfully verified that the scheme has a larger key space,stronger security,and can effectively improve the BER performance of the system.