Physical Layer Security Improvement Based On Digital Chaos In OFDM-PON System

In recent years,with the continuous emerging services such as IPTV,4K/8K video and virtual reality,end users are increasingly demanding access bandwidth,access capacity,and access service capabilities.As an effective terminal access technology for fiber to the home(FTTH),passive Optical Network(PON)is considered as one of the best solutions for low-cost broadband access and has become an important development direction of the future optical access network.Simultaneously,owing to its advantages of high spectrum utilization,flexible resource allocation,low cost and strong dispersion resistance,optical orthogonal frequency division multiplexing(OFDM)has been widely researched and become one of the mainstream technologies in the next PON system.However,the PON system adopts the point-to-multipoint centralized network architecture,where the downstream data is vulnerable to be eavesdropped by the invader due to the broadcast structure,thereby threatening the user data security.Therefore,this paper conducts the study how to implements physical layer encryption algorithm based on digital chaos in OFDM-PON system.Firstly,we analyze the basic characteristics and advantages of chaos for encryption,and combines the OFDM modulation process to achieve chaotic encryption of data in the time-frequency domain.Furthermore,the proposed new chaotic sequence generation technology,physical layer security enhancement,chosen plaintext attacks(CPAs)resistance and key protection scheme are verified through theory and simulation.Finally,the intensity modulation/direct detection(IM/DD)method was used to carry 10Gb/s OFDM signals transmission on 20 km single-mode fiber to verify the above schemes.The main research contents include the following parts:(1)Firstly,the background and significance of the security research on OFDM-PON system are introduced,and the research status of physical layer chaotic encryption of OFDM-PON system at home and abroad is expounder.Further,the defects of proposed chaotic encryption schemes are analyzed,and the corresponding improvement methods are proposed.(2)A novel chaotic sequence generation technique for OFDM-PON system is proposed.And,the chaotic system is analyzed by the phase projections and Lyapunov exponent,which verified the high randomness of the new chaotic sequence.(3)The physical layer security enhancement scheme of OFDM-PON system based on digital chaotic encryption is designed.In order to solve the high peak-to-average power ratio(PAPR)of OFDM signals,the chaotic chirp matrix scheme and the chaotic subcarrier reservation scheme are proposed to achieve the PAPR reduction and data encryption simultaneously.Besides,cellular automaton is proposed to expand the key space and plaintext diffusion in the physical layer encryption scheme of OFDM-PON system.(4)The chosen-plaintext attacks resistance encryption and dynamic key scheme of OFDM-PON system are researched.Aiming at the fixed mapping relationship between plaintext and ciphertext in traditional encryption scheme,a Feistel transform encryption scheme based on cellular neural network is proposed to generate dynamic ciphertext.For the security problem of key distribution,a dynamic key scheme is proposed to realize the ciphertext dynamic variation and key protection simultaneously.