The Expected Write Deficiency of Index-Less Indexed Flash Codes

Yuichi KAJI  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E95-A   No.12   pp.2130-2138
Publication Date: 2012/12/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E95.A.2130
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Information Theory and Its Applications)
Category: Coding Theory
Keyword: 
flash code,  flash memory,  index-less indexed flash code,  random walk,  

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Summary: 
The expected write deficiency of the index-less indexed flash codes (ILIFC) is studied. ILIFC is a coding scheme for flash memory, and consists of two stages with different coding techniques. This study investigates the write deficiency of the first stage of ILIFC, and shows that omitting the second stage of ILIFC can be a practical option for realizing flash codes with good average performance. To discuss the expected write deficiency of ILIFC, a random walk model is introduced as a formalization of the behavior of ILIFC. Based on the random walk model, two different techniques are developed to estimate the expected write deficiency. One technique requires some computation, but gives very precise estimation of the write deficiency. The other technique gives a closed-form formula of the write deficiency under a certain asymptotic scenario.