Q-ary Asymmetric LOCO Codes: Constrained Codes Supporting Flash Evolution

2020-06-01
Hareedy, Ahmed
Dabak, Beyza
Calderbank, Robert
© 2020 IEEE.Flash memory devices are winning the competition for storage density against magnetic recording devices. This outcome results from advances in physics that allow storage of more than one bit per cell, coupled with advances in signal processing that reduce the effect of physical instabilities. Constrained codes are used in storage to avoid problematic patterns. Recently, we introduced binary symmetric lexicographically-ordered constrained codes (LOCO codes) for data storage and transmission. This paper introduces simple constrained codes that support non-binary physical gates in multi, triple, quad, and the currently-in-development penta-level cell (M/T/Q/P-LC) Flash memories. The new codes can be easily modified if problematic patterns change with time. These codes are designed to mitigate inter-cell interference, which is a critical source of error in Flash devices. The new codes are called q-ary asymmetric LOCO codes (QA-LOCO codes), and the construction subsumes codes previously designed for single-level cell (SLC) Flash devices (ALOCO codes). QA-LOCO codes work for a Flash device with any number, q, of levels per cell. For q ≥ 4, we show that QA-LOCO codes can achieve rates greater than 0.95log2 q information bits per coded symbol. Capacity-achieving rates, affordable encoding-decoding complexity, and ease of reconfigurability support the growing improvement of M/T/Q/P-LC Flash memory devices, as well as lifecycle management as the characteristics of these devices change with time.
2020 IEEE International Symposium on Information Theory, ISIT 2020

Suggestions

Managing Device Lifecycle: Reconfigurable Constrained Codes for M/T/Q/P-LC Flash Memories
Hareedy, Ahmed; Dabak, Beyza; Calderbank, Robert (2021-01-01)
© 1963-2012 IEEE.Flash memory devices are winning the competition for storage density against magnetic recording devices. This outcome results from advances in physics that allow storage of more than one bit per cell, coupled with advances in signal processing that reduce the effect of physical instabilities. Constrained codes are used in storage to avoid problematic patterns, and thus prevent errors from happening. Recently, we introduced binary symmetric lexicographically-ordered constrained codes (LOCO c...
Read-and-Run Constrained Coding for Modern Flash Devices
Hareedy, Ahmed; Zheng, Simeng; Siegel, Paul; Calderbank, Robert (2022-01-01)
The pivotal storage density win achieved by solid-state 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 inter-cell interference that stems from charge propagation among cells....
Increasing the Lifetime of Flash Memories Using Multi-Dimensional Graph-Based Codes
Hareedy, Ahmed; Kuditipudi, Rohith; Calderbank, Robert (2019-08-01)
© 2019 IEEE.In order to meet the demands of data-hungry applications, data storage devices are required to be increasingly denser. Various sources of error appear with this increase in density. Multi-dimensional (MD) graph-based codes are capable of mitigating error sources like interference and channel non-uniformity in dense storage devices. Recently, a technique was proposed to enhance the performance of MD spatially-coupled codes that are based on circulants. The technique carefully relocates circulants...
A complex event processing framework implementation using heterogeneous devices in smart environments
Kaya, Muammer Özge; Eren, Pekin Erhan; Department of Information Systems (2012)
Significant developments in microprocessor and sensor technology make wirelessly connected small computing devices widely available; hence they are being used frequently to collect data from the environment. In this study, we construct a framework in order to extract high level information in an environment containing such pervasive computing devices. In the framework, raw data originating from wireless sensors are collected using an event driven system and converted to simple events for transmission over a...
Non-Binary Constrained Codes for Two-Dimensional Magnetic Recording
Dabak, Beyza; Hareedy, Ahmed; Calderbank, Robert (2020-11-01)
© 1965-2012 IEEE.The two-dimensional magnetic recording (TDMR) technology promises storage densities of 10 Tbits/in2. However, when tracks are squeezed together, a bit stored in the two-dimensional (TD) grid suffers inter-symbol interference (ISI) from adjacent bits in the same track and inter-track interference (ITI) from nearby bits in the adjacent tracks. A bit is highly likely to be read incorrectly if it is isolated in the middle of a $3 \times 3$ square, surrounded by its complements, horizontally and...
Citation Formats
A. Hareedy, B. Dabak, and R. Calderbank, “Q-ary Asymmetric LOCO Codes: Constrained Codes Supporting Flash Evolution,” California, Amerika Birleşik Devletleri, 2020, vol. 2020-June, Accessed: 00, 2022. [Online]. Available: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85090419043&origin=inward.