Quasi-Primitive Block-Wise Concatenated BCH Codes With Collaborative Decoding for NAND Flash Memories

Abstract

In this work, we propose a novel design rule of blockwise concatenated Bose-Chaudhuri-Hocquenghem (BC-BCH) codes for storage devices using multi-level per cell (MLC) NAND flash memories. BC-BCH codes designed in accordance with the proposed design rule are called quasi-primitive BC-BCH codes in which constituent BCH codes are deliberately chosen for their lengths to be as close to primitive BCH codes as possible. It will be shown that such quasi-primitive BC-BCH codes can achieve significant improvements of error-correcting capability over the existing BC-BCH codes when an iterative hard-decision based decoding (IHDD) is assumed. In addition, we propose a novel collaborative decoding algorithm which targets at resolving dominant error patterns associated with the IHDD. Error-rate performances of error-control systems with the proposed quasi-primitive BC-BCH and existing BC-BCH codes are compared. For more comprehensive performance comparisons, systems with a hypothetically long BCH code and a product code are also considered in the comparisons.