Research On Encoding Methods Of Multi-rate/Code Length Compatible Protograph-based LDPC Codes

With the commercialization of 5G,the converged applications of 5G have moved from the exploration stage to the landing stage.The application scenarios of 5G continue to be enriched,the degree of integration continues to increase,and the development direction continues to be clear.However,the application limitations of 5G have gradually emerged.Although 5G has a higher rate and lower latency,which can support new business applications such as high-definition video and AR/VR,but it still cannot meet the rate requirements of more advanced scenarios such as extreme AR/VR and holographic communication.The evolution of 5G is proposed to solve these problems,where the potential wireless key technologies mainly include ultra-large-scale antennas,advanced coding and modulation,Terahertz communication,and the convergence of AI and communication.In terms of advanced coding and modulation,the evo-lution of 5G proposes to achieve deep integration with vertical industries on the basis of greatly increasing the data transmission rate.Morever,more diversified application scenarios pose new challenges to channel coding and modulation technologies.LDPC codes are adopted by 5G New Radio(NR)as a coding scheme for enhanced mobile broadband(e MBB)service.With the evolution of 5G systems,higher transmission rates,higher reliability,and lower delay have become evolutionary requirements,and higher requirements are put forward for the performance of LDPC codes.This paper studies the advantages and dis-advantages of 5G-NR LDPC codes.On the basis of 5G-NR LDPC codes,multi-rate/code length compatible 5G-NR LDPC codes with lower error floors are designed for different modulation orders.Genetic algorithm is also used to construct 5G-NR LDPC codes with multiple code rates and code lengths.In addition,a high-speed LDPC codes simulation platform is used to compare and analyze the performance of the optimized 5G-NR LDPC codes and 5G-NR LDPC codes.Firstly,we introduce the background and research status of this subject.We briefly intro-duce the evolution of 5G and then we introduce the research status of LDPC codes.Then we briefly introduce the basic principles of LDPC codes,encoding and decoding algorithms,and analyze the bit error rate(BER)performance of different algorithms.We also construct a high-speed simulation platform for LDPC codes based on single instruction multiple data(SIMD).The thesis gives a specific SIMD code design plan,combined with multi-core processors to further enhance the computing perfomance.This paper mainly research the construction of rate compatible LDPC codes with low er-ror floor under BPSK modulatiob.We introduce the basic concepts and structure of 5G-NR LDPC codes in detail,and propose rate-compatible 5G-CW-Core LDPC codes with lower error floors under BPSK modulation.In view of the high error floors of 5G-NR LDPC codes under BPSK modulation,we quickly collect the error patterns of 5G-NR LDPC codes of error floors.Combined with the structure of the base graph of the 5G-NR LDPC codes,we give the reasons for the error floors.We propose to optimize the column distribution to lower the error floor of certain bit rates,optimize the shift value for a specific code length to eliminate trapping sets,optimize the row distribution to support rate compatible.Simulation results show that the pro-posed rate-compatible LDPC codes have near 5G-NR waterfall performance and lower error floors.This paper also propose a construction method of 5G-New LDPC codes with lower er-ror floors under high-order modulation.First,we introduce the bit-interleaved coded modu-lation(BICM)system of 5G NR system.Then we combine the structure of the 5G-NR LDPC codes and the mapping of the constellation under high order modulation to analyse the causes of error floors.We redesign the base graph of 5G-NR LDPC codes by partially increasing column weights in the parity part and averaging the weight distribution of columns in the information part where the weight distributions of rows and the single diagonal in Raptor-like structure are reasonably maintained to guarantee the water-fall performance and linear complexity en-coding.Simulation results show that the proposed 5G-New LDPC codes with moderate block lengths can significantly lower the error floors.Finally,we propose multi-rate/code length compatible protograph-based LDPC codes us-ing Genetic Algorithm(Gen Alg).Firstly,we briefly introduce the g Gen Alg,and then specifi-cally explain how to use the Gen Alg to optimize the construction of 5G-NR LDPC codes,and give specific construction steps for different modulation orders.By changing the number of the non-zero elements,the corresponding positions and shifting values,we optimize the 5G-NR LDPC codes with Gen Alg according to the error performances of coded BICM schemes.Simulation results show that the proposed 5G-ML LDPC codes can support length and rate compatible coding,which have lower error floors with very little performance loss at waterfall region compared to the 5G-NR LDPC codes with different modulation orders.