Research On LDPC Code Adaptive Dynamic Feature Coding Weight Distribution Algorithm For LEO Satellites

Low-earth-orbit(LEO)satellite systems have received widespread attention at home and abroad in recent years.Countries are striving to deploy low-earth-orbit satellite constellation systems.The power of low-earth-orbit satellite communication systems is limited.Therefore,a channel coding scheme with strong error correction capability is needed.When the satellite selects a channel coding scheme,it should take into consideration the actual situation of the satellite and the coding complexity and other factors for comprehensive consideration,to determine the appropriate coding method and corresponding decoding method.Due to the low decoding complexity and parallel decoding,and to comply with the trend of 5G and satellite integration,satellites should use more of the existing 5G ground station resources on the ground.LDPC(Low Density Parity Check)code as a 5G data channel coding scheme will meet the requirements of satellites well.Therefore,this article focuses on LDPC code related content.In this paper,the basic principle of LDPC code,encoding and decoding method and shortening algorithm are studied in detail,and a simulation platform conforming to 5G NR standard is built,the simulation results of LDPC code under satellite channel are presented.The satellite transmission distance is long,the channel changes quickly,according to different channel conditions adaptively change the code rate and code length can effectively improve the system transmission effectiveness and reliability.repetition.This paper mainly focuses on the shortening algorithm,however,in the existing 5G,DVB(Digital Video Broadcasting),802.11 protocols in the shortening algorithm,usually adopts the sequential deletion method,the system performance is not optimized,so we have proposed a lot of better performance shortening algorithm,but the complexity is high,the calculation volume is large,and it is difficult to implement on the satellite.In this case,it is more meaningful to reassign weights to the check matrix according to different code rates,which is an effective method to realize the adaptive encoding rate and code length.LDPC code weighting is mainly based on different channel conditions,and the weights of rows or columns of the check matrix can be dynamically changed to realize different code rates,which can make better use of the existing channel conditions,save resources,and be widely used in the actual communication system.Redistribution of weights is currently achieved through shortening,puncturing and repetition.This paper mainly focuses on the shortening algorithm,however,in the existing 5G,DVB(Digital Video Broadcasting),802.11 protocols in the shortening algorithm,usually adopts the sequential deletion method,the system performance is not optimized,so we have proposed a lot of better performance shortening algorithm,but the complexity is high,the calculation volume is large,and it is difficult to implement on the satellite.In view of the above problems,this paper systematically studies the LDPC codes in the 5G NR standard,and proposes a BCH and LDPC joint coding architecture suitable for satellite systems and an adaptive dynamic feature coding weight allocation algorithm for LDPC codes based on confidence ranking.In the LDPC code of the 5G data channel,a lot of padding bits are added to meet the length requirement before encoding,which has no practical effect.Therefore,the original information bits are BCH encoded,and the padding bits are replaced with BCH check bits.BCH and LDPC are used.The cascaded algorithm can better improve the system error correction performance.At the same time,for the shortening algorithm,the log-likelihood ratio information is used for analysis,and the LDPC coding weight allocation algorithm based on confidence ranking,CRLI(the Confidence Ranking of Log-like Ratio Information)algorithm,is designed.In a better case,it has the characteristics of shorter calculation time and less storage resources.The algorithm combines adaptive coding strategy to make better use of channel resources.The simulation results confirm that the joint coding architecture and weight distribution algorithm can effectively improve the performance of the system,reduce the algorithm complexity and occupy resources,and can be better applied on the satellite.