Research On New Error Correction Code In New Generation High Density Storage System

In the era of information big data,the amount of data in high-density storage system is increasing day by day,the size of its storage media is decreasing and the bit density in the unit area is increasing,and the reliability of storage data is becoming more and more prominent.A channel code,named Polar codes,was proposed by Arikan.Compared with the traditional channel code,Polar code has been proved to reach the Shannon limit in mathematical theory,and it has the advantages of low compilation code complexity,clear construction method,good error correction performance,can be used in storage systems,image transmission,coding modulation system.In this paper,the error control schemes of Multi-Level Cell?MLC?NAND flash memory and two-dimensional inter-symbol interference?2D-ISI?magnetic recording channels is studied for the data reliability issues in high-density storage systems,and its main contents are as follows:?1?This paper summarizes the basic operation of MLC flash memory,studies the error type of MLC flash memory cell and 2D-ISI magnetic recording channel,analyzes the error causes,and establishes the channel model.?2?A method based on the heterogeneity of mutual information?MI?is proposed to solve the construction of Polar codes for the channel characteristics of MLC NAND flash channel.The original Polar code construction method under the traditional AWGN channel is not suitable for the flash channel,and the method proposed in this paper uses the difference of channel characteristics between the traditional AWGN channel and MLC NAND flash channel to refit the log-like ratio?Log-Like Ratio,LLR?with MI,gets the equivalent variance under the flash channel to construct the Polar code.The simulation results show that Polar code constructed by several traditional methods performs poorly in error performance,and Polar code based on the heterogeneity of mutual information improves more than 2 order of magnitudes compared with Polar code constructed by Monte-Carlo method in bit error rate?BER?performance,and it can at least increase the lifetime of MLC flash memory up to 2000 program erase?P/E?cycles at the BER of 2×10^-5.?3?A construction method of Polar codes based on LLR distribution is proposed to in 2D-ISI magnetic recording channel.The data simulation shows that Polar code based on LLR distribution constructon method is better than Polar code constructed by the traditional method in error performance,and it has a 3 order of magnitudes improvement compared with Polar code constructed by Gaussian approximate method in BER performance.