Research On Key Technologies Of High-security Optical Communication Based On Trellis Coded Modulatio

The strategy of"strengthening the country with science and technology"has promoted the rapid development of China’s advanced technology level,and the process of building a digital information society has continued to advance.5G communication,artificial intelligence,big data,cloud services,and vehicle networking have entered the stage of widespread use in society,not only in China,but the rapid update of digital information technology has brought about a rapid increase in global network traffic.The upcoming"capacity crisis"puts forward the application requirements of higher transmission capacity for optical communication networks.Coding and modulation technology can improve the transmission spectrum efficiency of the system through reliable channel coding and higher-order modulation technology under the limited bandwidth condition,which is a key to coping with the"capacity crisis",but a single coding or modulation means that the system faces a conflict between reliability and effectiveness,so there is a need to study high-performance coding and modulation solutions that can balance transmission effectiveness and reliability.Trellis Coded Modulation（TCM）has become a hot topic of research.On the other hand,the increasing level of informatization of society has placed greater emphasis on communication security issues,anti-interference and confidential communication based on chaotic encryption is one of the important means of information security in the digital domain.This paper studies the high-performance coded modulation scheme based on TCM.Firstly,this paper studies the principle of forward error correction coding technology based on channel coding and summarizes the encoding and decoding process and algorithm of the commonly used Low Density Parity Check（LDPC）code and Turbo code.Secondly,the modulation format optimization technology constellation shaping is introduced based on signal modulation,and the working principle of probabilistic shaping（PS）and geometric shaping（GS）is expounded.Finally,the unique performance advantages of TCM are explained in light of the fundamental contradictions between coding and modulation technologies,followed by a study of the design principles and compiled code algorithms of TCM.Based on the goal of enhancing the transmission security of optical communication systems,the chaos encryption technique is focused on,the definition and characteristics of chaos and the determination method of chaos phenomenon are elaborated,and the current common chaos scrambling mechanism in optical communication is summarized.Based on the study of the above techniques,the specific research contents and innovative work of this thesis are as follows:（1）Aiming at the problems such as high average power of transmitting terminal of the constellation with high order modulation format in coding part of TCM,decreasing minimum Euclidean distance（MED）between constellation points with increasing order,and too large constellation expansion coefficient cancellations coding gain,a multi-stage GS-TCM transmission technology based on cluster mapping rules was proposed.The high-order two-dimensional（2D）constellation can be flexibly transformed into the low-order three-dimensional（3D）constellation,and the multi-stage GS gain can be obtained to further expand the coding gain,and reduce the average power of the transmitter and the nonlinear damage of the system.Experimental verification shows that the proposed scheme achieves a receiver sensitivity gain of about 6.98d B under the same modulation order compared with the traditional scheme combining PS and GS in 2D constellation space.The process of constellation transformation can also improve the security of the system,providing a layer of double insurance besides chaotic encryption technology.（2）For the study of the chaotic scrambling mechanism,a chaotic rotation encryption mechanism based on quaternion is proposed,which uses quaternion and rotation matrix to realize rotation masking of a three-dimensional cube constellation based on Chua’s chaotic model.The hidden constellation is hollow and spherical,which hides the original constellation information.The experimental results show that the encryption mechanism can provide2.12×10^{8 8}key space.It has good initial value sensitivity and reliable security performance.（3）In view of the high cost of key management of chaotic confidential communication based on symmetric encryption,and the important research hotspot of"ciphertext-with-key transmission"is more suitable for practical applications in the future,this paper innovatively proposes a high-dimensional chaotic key 3D modulation transmission scheme based on Run-Length Encoding（RLE）,which is different from the traditional 0,1-bit stream as the source.The six-dimensional Lorenz-duffing chaotic system is used to generate the key and process it as the information source,at the same time,proposes a source binary conversion method to generate a chaotic key source that can be modulated,the run-length coding is used to compress the redundancy of the chaotic key to improve the transmission efficiency,and the three-dimensional 9QAM folding mapping design of chaotic key like paper folding is proposed to improve the anti-noise performance of the system.The simulation results show that the proposed scheme has an SNR gain of 1.2d B compared with the uncompressed transmission system at the bit error rate（BER）threshold of1×10^-3,which provides a meaningful research basis for the study of"ciphertext-with-key transmission".