Journal of the Institute of Electronics Engineers of Korea SD (대한전자공학회논문지SD)

The Institute of Electronics and Information Engineers (대한전자공학회)
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Cell to Cell Interference Cancellation Algorithms in Multi level cell Flash memeory

MLC 플래시 메모리에서의 셀간 간섭 제거 알고리즘

  • Jeon, Myeong-Woon (Department of Electrical and Computer Science Engineering, Seoul National University) ;
  • Kim, Kyung-Chul (Department of Electrical and Computer Science Engineering, Seoul National University) ;
  • Shin, Beom-Ju (Hynix Inc.) ;
  • Lee, Jung-Woo (Department of Electrical and Computer Science Engineering, Seoul National University)
  • 전명운 (서울대학교 전기컴퓨터공학부) ;
  • 김경철 (서울대학교 전기컴퓨터공학부) ;
  • 신범주 (하이닉스) ;
  • 이정우 (서울대학교 전기컴퓨터공학부)
  • Received : 2010.05.13
  • Accepted : 2010.11.22
  • Published : 2010.12.25
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Abstract

NAND multilevel cell (MLC) flash memory is widely issued because it can increase the capability of storage by storing two or more bits to a single cell. However if a number of levels in a cell increases, some physical features like cell to cell interference result cell voltage shift and it is known that a VT shift is unidirectional. To reduce errors by the effects, we can consider error correcting codes(ECC) or signal processing methods. We focus signal processing methods for the cell to cell interference voltage shift effects and propose the algorithms which reduce the effects of the voltage shift by estimating it and making level read voltages be adaptive. These new algorithms can be applied with ECC at the same time, therefore these algorithms are efficient for MLC error correcting ability. We show the bit error rate simulation results of the algorithms and compare the performance of the algorithms.

NAND Multi-level cell Flash memory는 한 셀에 여러 bit의 정보를 저장하는 방법으로, 용량 집적도를 더욱 높일수 있는 기술로 각광 받고 있다. 하지만 한 셀당 레벨 수를 올릴 경우, 셀간 간섭 등 여러 물리적 이유들로 인해 오류가 발생하며, 이 주된 오류 방향은 unidirectional 함이 알려져 있다. 기존에는 오류 정정 부호(ECC)등을 이용하여 이를 해결하려 했지만, 우리는 셀간 간섭으로 인한 오류에 포커스를 맞추어, 이 영향을 예측하고 줄여서 오류를 보정하는 새로운 알고리즘들을 제안한다. 이 알고리즘은 기존 오류정정부호 기법들과 별도의 단계로 동시에 적용할 수 있기에 에러 정정능력 향상에 효과적이다. 제안된 알고리즘들을 시뮬레이션을 통하여 성능을 비교하고 효율적인 알고리즘이 무엇인지 알아본다.

Keywords

References

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