Research On Construction Of Ultra-low Rate LDPC And Its Application In Burst Channels

Channel coding is an important technique to reduce the influence of noise on signal during transmission and improve the reliability of the communication systems.In addition to the conventional additive Gaussian noise,the burst noise caused by jamming and strong collision will make the channel environment worse.Therefore,the research on channel coding technologies in this scenario is very valuable.Low Density Parity Check(LDPC)codes have been adopted by 3rd Generation Partnership Project(3GPP)as the channel coding scheme in the Enhanced Mobile Broadband(e MBB)scenario of 5G New Radio(5G NR)because of its excellent performance,parallelizable execution and flexible rate matching compatibility.Therefore,this thesis focuses on the research of LDPC codes application in the burst channels.The main research contents of this thesis mainly include the following aspects:Firstly,the research background of burst channels are introduced.Then the application of the related LDPC codes and frame-based codes in this scenario is briefly introduced.In the following,we raise the issue of construction of ultra-low LDPC codes and design of the concatenated coding.Secondly,in Chapter 2,the relevant fundamental theories of LDPC codes and the structure of rate-compatible LDPC codes are introduced in detail.Then the coding algorithms and decoding methods related to LDPC codes are described at length.Some common burst channel models are given subsequently.In Chapter 3,we study the design of the ultra-low rate LDPC codes.The LDPC codes are followed by the structure of rate-compatible LDPC codes in 5G.We construct the base parity-check matrix of the ultra-low LDPC codes by extending the LDPC codes in 5G and performing threshold analysis on the extended matrix based on density evolution.Then,optimizing the shift values of the base parity-check matrix is by maximizing the minimum distance of extended LDPC codes.Finally,by numerical simulations,we demonstrate the proposed methods can design some ultra-low rate LDPC codes with excellent performance.In Chapter 4,a burst channel model is introduced.And a concatenated coding scheme by concatenating a frame-based code called Binary Deterministic Rateless Codes(BDRC)and LDPC codes is proposed to cope with the strong burst error.We further propose a joint decoding algorithm for BDRC and LDPC to improve the decoding performance.Then it is verified by simulation that the concatenated coding scheme can bring significant performance gains.We finally summarize the study results and give the future research interests.