Rasearch On Key Technologies Of Novel Coding Modulation Based On Probabilistic Shaping

The amount of Internet data is growing rapidly with an annual growth rate of about 60%.However,in recent years,the growth rate of the transmission capacity of optical fiber communication system has dropped from 78%over Moore’s Law to 20%.Such slow growth rate cannot meet the rapidly increasing demand for transmission capacity,and the optical fiber communication system is facing a serious ’capacity crisis’.With limited bandwidth resources,coding modulation technology can effectively improve channel spectral efficiency through high-order modulation and reliable coding.And novel coding modulation based on probabilistic shaping can reduce the transmission probability of high-energy constellation points and increase the transmission probability of low-energy constellation points,thus optimizing the probability distribution of the uniform modulation constellation and improving the matching degree of the modulation format and the transmission channel,which has become an effective means to improve the transmission performance of the optical fiber communication system and approach the limit of the channel capacity.Based on the study of the theory of coding modulation in optical fiber communication system,this research focuses on three key scientific issues:how to generate a nonuniform probabilistic shaping signal with low complexity,how to further improve the constellation shaping gain,and how to achieve the simultaneous improvement of the safety performance of the probabilitic shaping mechanism.The focus of the research is on the generation method of nonuniform probabilistic shaping signal,the constellation hybrid probabilistic-geometric shaping,and the probability shaping security mechanism based on chaotic encryption.The main research work and innovations of this paper are as follows:1.The methods to generate nonuniform probabilistic shaping signala)A probabilistic shaping signal generation method of multi-subsets partition mapping based on symbol classification is proposed.By classifying the original data into multiple symbol subsets with different numbers of bits,the symbols with different probabilities in the subsets are mapped to different regions of the constellation.So symbols with a higher probability are mapped to the inside of the constellation,and symbols with a lower probability are mapped to the outside,thereby reducing the signal average power and improving the system BER performance.The proposed method not only has the advantage of low implementation complexity,but also can achieve modulation formats with different orders to obtain flexible information entropy.The experimental results show that the resulting PS-CAP-12 signal has a 2 dB gain in receiver sensitivity compared to the traditional CAP-16 signal.b)A bit-interleaved multi-carrier probabilistic shaping signal generation method based on Huffman coding is proposed.Through applying Huffman coding mapping and binary information bit interleaving,combined with the generalized frequency division multiplexing technology based on the traditional filter bank multi-branch multi-carrier concept,this method generates a multi-carrier probabilistic shaping signal with lower PAPR,ultra-low out-of-band radiation,and insensitive to frequency offset and phase noise.The simulation results show that the proposed scheme has better signal transmission performance and can support higher transmission rate and longer transmission distance.2.Constellation hybrid probabilistic-geometric shapinga)A two-dimensional constellation hybrid shaping scheme based on the design with honeycomb-like decision regions is proposed.With the goal of maximizing the constellation figure of merit(CFM),most of the constellation points retract via increasing the number of rings with different amplitudes in the star constellation,and reducing the number of constellation points on each ring.Meanwhile,probabilistic shaping is employed to optimize the probability distribution of the constellation points in the proposed novel star constellation.The geometric structural design in parallel with probabilistic shaping is able to reduce the constellation average power and enhance the CFM.The experimental results show that the proposed PS star-CAP-16 achieves a 1.5 dB gain in receiver sensitivity compared to the traditional PS star-CAP-16.b)A three-dimensional constellation hybrid shaping scheme based on regular tetrahedron cell design is proposed.This scheme is based on the combined effect of two constellation shaping technologies in the three-dimensional constellation space.Through the topology design with the element of regular tetrahedron in three-dimensional space,the potential of geometric probability optimization in high-dimensional space constellation is fully utilized,so that in the condition of fixed minimum Euclidean distance,the inward aggregation of constellation points as much as possible and the reduction of the average energy of the constellation are realized.The experimental results show that the proposed 3D-PS-CAP-16 obtains a 1.0 dB gain in receiver sensitivity compared to the traditional 3D-PS-CAP-16.3.Probabilistic shaping security mechanism based on chaotic encryptiona)A 3D-CAP-PON system based on two-stage spherical constellation masking is proposed.Based on the two chaotic models of Chua’s circuit map and one-dimensional Logistic map,the rotation masking and scaling masking of the three-dimensional constellation are realized respectively.The masked constellation shows a hollow sphere with thick wall,and this multi-dimensional,multi-stage and multi-chaotic constellation masking method brings greater flexibility to constellation masking,which effectively improves the security performance brought by constellation encryption.The experimental results show that the key space of this scheme is 1.2 ×1073,and it has a reliable anti-attack ability.b)A PS-OFDM-PON system based on chaotic constant composition distribution matching is proposed.Based on a 4D hyperchaotic Lv’s system that can generate four sets of chaotic sequences at the same time,the chaotic scrambled encryption for the amplitude mapping is implemented in the processing of QAM mapping,as well as the dynamic chaotic configuration for signs.This scheme not only improves BER performance via optimizing the constellation probability distribution,but also enhances security performance via the data encryption in physical layer.The experimental results show that the proposed PS-16QAM-OFDM encrypted signal obtains a 1.2 dB gain in receiver sensitivity compared to the uniform 16QAM-OFDM,and the key space reaches 1.98× 1073,showing good initial sensitivity.