Coding for memory with stuck-at defects

Kim, Yongjune; Kumar, B. V. K. Vijaya

doi:10.1109/icc.2013.6655249

Cited by 15 publications

(12 citation statements)

References 7 publications

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“…Several more code constructions as well as efficient encoding and decoding algorithms for the earlier constructions were studied; see e.g. [5], [12], [16], [17], [21]. This paper studies codes which mask cells that are partially stuck-at.…”

Section: Introductionmentioning

confidence: 99%

Codes for Partially Stuck-At Memory Cells

Wachter-Zeh

Yaakobi

2016

IEEE Trans. Inform. Theory

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In this work, we study a new model of defect memory cells, called partially stuck-at memory cells, which is motivated by the behavior of multi-level cells in non-volatile memories such as flash memories and phase change memories. If a cell can store the q levels 0, 1, . . . , q − 1, we say that it is partially stuck-at level s, where 1 ≤ s ≤ q − 1, if it can only store values which are at least s. We follow the common setup where the encoder knows the positions and levels of the partially stuck-at cells whereas the decoder does not.Our main contribution in the paper is the study of codes for masking u partially stuck-at cells. We first derive lower and upper bounds on the redundancy of such codes. The upper bounds are based on two trivial constructions. We then present three code constructions over an alphabet of size q, by first considering the case where the cells are partially stuck-at level s = 1. The first construction works for u < q and is asymptotically optimal if u + 1 divides q. The second construction uses the reduced row Echelon form of matrices to generate codes for the case u ≥ q, and the third construction solves the case of arbitrary u by using codes which mask binary stuck-at cells. We then show how to generalize all constructions to arbitrary stuck levels. Furthermore, we study the dual defect model in which cells cannot reach higher levels, and show that codes for partially stuck-at cells can be used to mask this type of defects as well. Lastly, we analyze the capacity of the partially stuck-at memory channel and study how far our constructions are from the capacity.

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Section: Introductionmentioning

confidence: 99%

Codes for Partially Stuck-At Memory Cells

Wachter-Zeh

Yaakobi

2016

IEEE Trans. Inform. Theory

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“…A high energy particle impacting on a NAND flash cell usually causes what is known as a stuck-at defect [8]. The cell effectively breaks and will henceforth be read as storing the same voltage value, regardless of what it was meant to be programmed to.…”

Section: Effect Of Impulsive Noisementioning

confidence: 99%

Spread programming for NAND flash

Luo

Peleato

2015

2015 IEEE International Conference on Communications (ICC)

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The aggressive scaling of NAND flash memories has caused significant degradation in their reliability and endurance. One of the dominant factors in this degradation is the intercell-interference (ICI), by which the programming of a cell can affect near-by neighboring cells corrupting the information that they store. This paper proposes a new data representation scheme which increases endurance and significantly reduces the probability of error caused by ICI. The method is based on using an orthogonal code to spread each bit across multiple cells, resulting in a more uniform distribution of voltages being programmed in the cells.

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“…By reading all the wordlines simultaneously with a very low read threshold, the controller can detect which bitlines have cells that have not been completely erased, and store their indices as part of the block's metadata. The controller may then chose to skip those bitlines during the writing process, use a constraint code to mask the errors [13], or ignore this information and rely on the ECC block to correct any errors that might arise.…”

Section: B Partial Erasementioning

confidence: 99%

Multipage Read for <sc>nand</sc> Flash

Luo

Peleato

2017

IEEE Trans. Circuits Syst. II

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NAND flash memories achieve very high densities through a series connection of all the cells in a bitline. In current memories, each wordline is read independently by biasing all the other cells to act as pass transistors and sensing all the bitlines in parallel. This paper proposes a new method which reads multiple wordlines simultaneously and returns a combination of their stored information. This multi-page read method is shown to be useful for equalizing the inter-cell interference, reduce the damage caused by erase operations, and speed up the decoding of a certain class of codes.

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Coding for memory with stuck-at defects

Cited by 15 publications

References 7 publications

Codes for Partially Stuck-At Memory Cells

Codes for Partially Stuck-At Memory Cells

Spread programming for NAND flash

Multipage Read for <sc>nand</sc> Flash

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