Research On LDPC-CC/BCH Coding And Algorithms Based On Hierarchical Iteration In MAN

In recent years, the development of mobile Internet technology makes the metro fiber technology needs to be further optimized. "Internet +", era of the arrival of high-speed large-capacity metropolitan area network has become the development trend. Multilayer coding can correct the error of information in the channel transmission. The modulation technology can increase the coding gain, and decoding can improve the system's error performance. Aiming at the problem that the coding gain is not high and the high bit error rate in the metropolitan area network, multi - layer coding and multi - layer modulation technology has become a hot topic both at home and abroad.Based on the research of channel coding and decoding at home and abroad, this paper focuses on the multi-layer multi-rate encoding,decoding and star QAM modulation technology to improve the flexibility of communication system and the tolerance of laser power. The main research work is as follows :1) Based on the study of hierarchical coding, the coding technique of adjustable rate is studied, and a multi-layer coding scheme with adjustable rate is proposed. The results show that the symbol information rate and the coding efficiency and modulation mode of each layer after layering show a certain correlation, which makes the symbol rate of each layer variable and more flexible.2) Based on the study of hierarchical coding modulation, a 4n-layer star QAM modulation scheme is designed. The peak power of star QAM modulation and rectangular QAM modulation is simulated. The results show that 4n-layer star QAM modulation can increase the coding gain.Compared to rectangular QAM modulation, the peak power of the star QAM is more stable, so the star QAM has a better tolerance for the laser.3) On the basis of studying the traditional decoding, a hierarchical iterative decoding algorithm is proposed. The accuracy of the decision output is increased by using the likelihood of the transmission in the hierarchical decoding process, and the bit error rate performance of the system is simulated. The results show that the use of hierarchical iterative decoding algorithm in the decoding process has a greater decoding reference and making the decoding more reliable.