Nonbinary LDPC Code In The Application Of NAND Flash Memery

Bit error from NAND flash on the physical mechanism is inevitable.With the NAND flash to use more advanced technology and more advanced structure,NAND flash storage capacity has been improved,with the probability of error is dramatically improved,leading to the original BCH and RS NAND flash for error correcting code more and more weak,so there is a pressing need to find a more reliable error correcting code to improve the reliability of NAND flash and reduce the error rate.In recent years,the Nonbinary LDPC code has been paid more and more attention because of its relatively low complexity of encoding and decoding,good error correction performance and high order input characteristics which suitable for NAND flash.In the same code length with the same code rate,the performance of Nonbinary LDPC code is better than binary LDPC code.In this paper,we study the error correction code requirements of binary LDPC code and Nonbinary LDPC code for NAND flash,code construction and the decoding algorithms.The main work includes the following aspects:One kind of simple and flexible Nonbinary quasi-cyclic-LDPC(QC-LDPC)code construction ideology is proposed,the ideology use some kinds of element,such as structural matrix,substitution,binary to nonbinary substitution and diffusion matrix elements.Through the proper selection and combination of these elements,we can construct the better performance of the Nonbinary QC-LDPC code.According to this ideology,a construction method is proposed.The construction of Nonbinary QC-LDPC code for encoding and decoding can effectively reduce the complexity of encoding and decoding,and significantly reduce the complexity of hardware implementation,it is very suitable for NAND flash error correcting code.In addition,this paper also construct binary QC-LDPC code and Nonbinary QC-LDPC code with high bit rate for NAND flash,and focuse on the simulation and comparison of them.Present an improved decoding algorithm for Nonbinary QC-LDPC.Make an intensive study on several commonly used decoding algorithm for nonbinary LDPC code,and a universal reduced complexity iterative decoding algorithm is given according to the construct methods of the nonbinary QC-LDPC codes in our paper.This algorithm is based on the binary QC-LDPC code algorithm,and based on the expansion of it.