Research On Nonbinary LDPC Code Decoding Algorithms In Optical Fiber Communication And FPGA Implementation

Low density parity check(LDPC)code is a kind of linear block code with excellent performance which is proposed by Dr.Gallager.It overcomes the shortcomings of other error correcting codes and it is the nearest channel code from Shannon limit at the present discover.The decoding algorithms of LDPC code can reduce the decoding delay by the parallel decoding structure,so this has caused great concern in many fields.In recent years more and more scholars begin to study LDPC code,this makes the coding and decoding algorithms of LDPC code improved continuously.LDPC code has been widely used in many fields such as optical fiber communication,digital watermarking,underwater communication and deep space communication because of its excellent performance.As a new communication technology,optical fiber communication has shown great advantages from the beginning.The binary LDPC code has been widely used in optical fiber communication,but non-binary LDPC code has better performance,so non-binary LDPC code is more suitable for optical fiber communication.The paper will mainly study in the following aspects:1.A brief introduction about the characteristics of optical fiber communication and the advantages of using non-binary LDPC code as error correcting code in optical fiber communication.We introduce the basic theories of non-binary LDPC code including the express methods,construction methods and common coding methods.2.Several classical decoding algorithms of non-binary LDPC code are introduced,including BP algorithm,LOG-BP algorithm,min-sum algorithm,extended min-sum algorithm and FFT-BP algorithm.On this basis,an improved FFT-BP algorithm is proposed.We can improve the accuracy of the initial information of FFT-BP decoding algorithm by adding a decision bit to the encoded codewords at equal intervals.The improved decoding algorithm can effectively reduce the average iteration number.3.We detailed introduce the FPGA implementation of the addition and multiplication in finite field and on this basis we design the encoder of non-binary LDPC code.The improved FFT-BP decoding algorithm is realized by using the top-down modular design idea in FPGA and we verify the accuracy by Modelsim simulation software.4.We give the summary of the content,point out the shortcomings of the paper and the next research direction.