Research On Physical Layer Security Of Access Network Based On Channel Coding

The large-scale outbreak of a series of network security incidents in recent years has aroused great concern about the security and confidentiality of the network.The optical access network is located in the "last mile" of the network and is closest to the user.Due to the topology of the optical access network,each user or even illegal user can receive the information sent in broadcast mode in the downlink direction.The security problem in the upstream direction is that the optical access network approaches the client,and the optical splitting/combining,the optical amplifier and other devices are vulnerable to attack.Therefore,the issue of security of the optical access network has attracted widespread attention and has also become a research topic to be solved urgently.There are many security enchancement technologies in optical access network including optical quantum key distribution,chaotic laser communication,upper layer encryption,optical coding,and physical layer security.The optical quantum key distribution and chaotic laser communication have high security,but the implementation complexity is rather high and put more strict demands to the synchronization or filters.The upper layer encryption have a complex key management and cannot provide security protection for the header control frame.The key space in optical coding is not large enough,which can be cracked easily by brute force.The physical layer encryption technology is relatively simple,with full information security,low complexity,flexible implementation,and information theory security.It has become one of the most promising optical access network security enhancement technologies.Because of the good robustness to fiber channel dispersion of orthogonal frequency division multiplexing(OFDM)in optical communication,this paper proposes two schemes to complete the access network physical layer encryption,which are based on orthogonal frequency division multiplexing-passive optical network(OFDM-PON).The main work and contributions of this dissertation are as follows:1.A turbo-coded OFDM-PON physical layer security enhancement scheme is proposed.which using the Brownian motion chaos model to design the turbo code interleaver and the channel interleaver to encrypt the information twice.Experimental results show that this scheme can effectively enhance the physical layer security of the access network and improve the BER performance of the system.2.An OFDM-PON physical layer security enhancement scheme based on turbo trellis coded modulation(TTCM)is proposed.Based on the previous scheme,a parity block interleaver and channel interleaver are designed based on Brownian motion chaos model to encrypt the information twice.The experimental results show that this scheme has larger key space,higher bandwidth transmission efficiency and greater improvement of the BER performance than those of the previous scheme.The above two solutions combine the access network physical layer security technology with the existing excellent channel coding technology,taking into account both of the transmission system security and reliability.The feasibility of the schemes is verified by transmitting different OFDM signals at a rate of 22.06Gb/s in OFDM-PON experimentally.The experimental results show that both of the schemes proposed in this paper can guarantee network security and improve the system transmission performance to some extent.Therefore,both of the schemes can be potential candidates for future physical layer security in optical access network.