In order to improve the BER performance of MLC NAND Flash, this paper presents a shortened polarization-based optimized codes for MLC NAND Flash. Optimized shortened codes are obtained by optimizing shortened pattern. Firstly, basic shortened pattern is obtained by bit reversal reordering, and then the freeze bits are selected with a lower channel capacity to constitute optimized shortened pattern, the resulting punctered bits are all frozen bits, this method can significantly improve the error correction performance. Meanwhile, according to the error asymmetry of MLC unit, unequal error protection is used for the LSB and MSB. Simulation results show that the performance of the optimized shortened codes is better than LDPC and basic shortened polar code about 3.72~5.89 dB and 1.47~3.49 dB gain at the frame error rate of 10- ; compared to the same rate based optimized 3 shortened codes, the new ECC program obtains gain about 0.25 dB .%为了提高MLC NAND Flash的抗误码性能,该文提出一种基于优化缩短极化码的MLC NAND Flash差错控制方法.优化缩短极化码通过优化删减图样得到,首先通过比特翻转重排序的方式得到基本删减图样,进而选择具有更低信道容量的冻结比特组成优化删减图样,使得到的删减比特全为冻结比特,可以显著提高删减算法的纠错性能.同时,根据MLC单元错误的不对称性,采用码率自适应的码字对FLASH中MSB和LSB进行不等错误保护.仿真结果表明:当误帧率为10-时,优化缩短极化码较相同码长的LDPC码和基本缩短极化码分别约有33.72~5.89 dB和1.47~3.49 dB增益;相比基于同一码率的优化缩短极化码方案,不等错误保护的差错控制方案获得约0.25 dB增益.
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