Managing Device Lifecycle: Reconfigurable Constrained Codes for M/T/Q/P-LC Flash Memories

Hareedy, Ahmed; Dabak, Beyza; Calderbank, Robert

doi:10.1109/tit.2020.3032407

Cited by 16 publications

(49 citation statements)

References 23 publications

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“…As implied in the introduction, literature works do not strictly agree on the set of forbidden patterns to operate on. Additionally, as the Flash device ages, the set of error-prone patterns is expected to expand [18]. Based on our recent experimental tests on a practical TLC Flash device, we decided to focus on the set characterized as follows.…”

Section: Patterns Mapping and 2d Rr Codingmentioning

confidence: 99%

“…Coding to eliminate data patterns resulting in consecutive levels (q − 1)0(q − 1) was considered in [16] and [17]. Coding to eliminate data patterns resulting in consecutive levels or level patterns (q − 1)µ(q − 1), for all µ < q − 1, was presented in [15], [17], and [18].…”

Section: Introductionmentioning

confidence: 99%

“…Another example is [7], in which we introduced binary symmetric lexicographicallyordered constrained (S-LOCO) codes and demonstrated density gains in a modern magnetic recording system. We extended our result to single-level cell (SLC) Flash (q = 2) [20] then to Flash with any number q of levels per cell [18]. Moreover, we devised a general method to design LOCO codes for any finite set of patterns to forbid [21], which will be useful in this paper.…”

Section: Introductionmentioning

confidence: 99%

“…We studied the power spectra of binary LOCO codes in [22]. LOCO codes are capacity-achieving, simple, and easily reconfigurable [18], [21].…”

Section: Introductionmentioning

confidence: 99%

“…While the constrained codes in [17] and [18] are quite efficient in terms of rate, they require all Flash pages to be processed together, which negatively affects the access speed. In this paper, we propose read-and-run (RR) constrained coding schemes that allow pages to be accessed separately in modern Flash devices, thus preserving high access speed.…”

Section: Introductionmentioning

confidence: 99%

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Read-and-Run Constrained Coding for Modern Flash Devices

Hareedy,

Zheng,

Siegel

et al. 2021

Preprint

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The pivotal storage density win achieved by solidstate devices over magnetic devices in 2015 is a result of multiple innovations in physics, architecture, and signal processing. One of the most important innovations in that regard is enabling the storage of more than one bit per cell in the Flash device, i.e., having more than two charge levels per cell. Constrained coding is used in Flash devices to increase reliability via mitigating intercell interference that stems from charge propagation among cells. Recently, capacity-achieving constrained codes were introduced to serve that purpose in modern Flash devices, which have more than two levels per cell. While these codes result in minimal redundancy via exploiting the underlying physics, they result in non-negligible complexity increase and access speed limitation since pages cannot be read separately. In this paper, we suggest new constrained coding schemes that have low-complexity and preserve the desirable high access speed in modern Flash devices. The idea is to eliminate error-prone patterns by coding data only on the left-most page while leaving data on all the remaining pages uncoded. Our coding schemes work for any number of levels per cell, offer systematic encoding and decoding, and are capacity-approaching. Since the proposed schemes enable the separation of pages, we refer to them as read-and-run (RR) constrained coding schemes as opposed to schemes adopting readand-wait for other pages. We analyze the new RR coding schemes and discuss their impact on the probability of occurrence of different charge levels. We also demonstrate the performance improvement achieved via RR coding on a practical triple-level cell Flash device.

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Section: Patterns Mapping and 2d Rr Codingmentioning

confidence: 99%