基于QC-LDPC码的空间CCD图像NAND闪存存储纠错

NAND flash memory ECC based on QC-LDPC for space CCD image

为了提高空间CCD相机图像NAND闪存存储可靠性,提出一种基于QC-LDPC码的NAND闪存纠错算法。首先,分析了NAND闪存纠错信道模型;然后,根据闪存特点提出了一种基于QC-LPDC(1056,1024)码的NAND闪存纠错算法,为了加快编码效率提出了校验矩阵构造和高效编码方法,设计的校验阵均是0和1,只有移位和加法运算,非常适合硬件实现;最后,使用地面检测设备对闪存纠错算法进行了试验验证。结果表明,闪存纠错算法能快速稳定、可靠地工作,计算复杂度比较低,算法复杂度仅具为O(N);算法纠错能力高,误码比(BER)为10-6时,本文算法比RS码多0.47dB编码增益;使用65nm CMOS单元库,系统工作频率为250MHz时解码器数据吞吐率达到7.2Gbps;低误码平层,在误比特率为10-8时未出现误码平层。本文的NAND闪存纠错算法满足了空间相机图像存储系统的应用。

In order to improve the rdiability of NAND flash for the application of space CCD camera, an error correction coding （ECC） algorithm based on quasi-cyclic low-density parity-check （QC-LDPC） for NAND flash memory is presented in this paper. First, this paper presents a deep analysis of the NAND flash memory channel model. Then, according to the built channel model, a QC-LPDC （1 056,1 024）- based error correction coding algorithm is proposed. In order to improve the coding efficiency, a construc- ting method of the check matrix and efficient coding method are developed. The designed check matrix has 0 or 1 only, which can only be implemented by shift and addition operations. This characteristic is very suitable for the hard implementation. Finally, the verification experiments of the proposed NAND error correction coding algorithm are carried out using the ground test device. The experimental results show that the proposed error correction coding algorithm can operate fast, efficiently, reliably, and stably. The complexity of the proposed algorithm is very low,which is only O （N）. The proposed algorithm has great correction ability,and the encoding gain is improved by 0.47 dB than RS method when the BER is 10-6. In a 65 nm CMOS process, the QC-LDPC code designed as a prototype provides a decoding throughput of 7.2 Gbit/s. The proposed algorithm has low error-floor, and the error-floor does not exist when the BER is 10-8. The proposed error correction coding algorithm can satisfy the space camera data storage requirements of the reliability.