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Contact:
Marcus Greferath
School of Math. Sciences
University College Dublin
Belfield, Dublin 4, Ireland
Phone:
+353-1-716-2588 (UCD)
+353-85-153-0951 (mobile)
Joachim Rosenthal
Institut of Mathematics
University of Zurich
Winterthurerstrasse 190
8057 Zurich, Switzerland
Phone:
+41-44-63 55884 (office)
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ITW 2010 Dublin
IEEE Information Theory Workshop
Dublin, August 30 - September 3, 2010
Coding for memories
Mon 30 Aug, 16.20-17.40, Room 1
Contributed session
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Tuvi Etzion, Alexander Vardy, and Eitan Yaakobi
Dense Error-Correcting Codes in the Lee Metric
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Abstract:
Several new applications and a number of new mathematical techniques
have increased the research on error-correcting codes in the Lee
metric in the last decade. In this work we consider several coding
problems and constructions of error-correcting codes in the Lee
metric. First, we consider constructions of dense error-correcting
codes in relatively small dimensions over small alphabets. The
second problem we solve is construction of diametric perfect codes
with minimum distance four. We will construct such codes over
various lengths and alphabet sizes. The third problem is to transfer
an n-dimensional Lee sphere with large radius into a shape, with
the same volume, located in a relatively small box. Hadamard
matrices play an essential role in the solutions for all three
problems. A construction of codes based on Hadamard matrices will
start our discussion. These codes approach the sphere packing bound
for very high rate range and appear to be the best known codes over
some sets of parameters.
Mon 30 Aug, 16.20-16.40, Room 1
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Eitan Yaakobi, Anxiao (Andrew) Jiang, Paul H. Siegel, Alexander Vardy, and Jack K. Wolf
On The Parallel Programming of Flash Memory Cells
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Abstract:
Parallel programming is an important tool used in flash memories to
achieve high write speed. In parallel programming, a common programm
voltage is applied to many cells for simultaneous charge
injection. This property significantly simplifies the complexity of
the memory hardware, and is a constraint that limits the storage
capacity of flash memories. Another important property is that cells
have different hardness for charge injection. It makes the charge
injected into cells differ even when the same program voltage is
applied to them.
In this paper, we study the parallel programming of flash memory
cells, focusing on the above two properties. We present algorithms
for parallel programming when there is information on the cells'
hardness for charge injection, but there is no feedback information
on cell levels during programming. We then proceed to the
programming model with feedback information on cell levels, and
study how well the information on the cells' hardness for charge
injection can be obtained. The results can be useful for
understanding the storage capacity of flash memories with parallel
programming.
Mon 30 Aug, 16.40-17.00, Room 1
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Eitan Yaakobi, Scott Kayser, Paul H. Siegel, Alexander Vardy, and Jack K. Wolf
Efficient Two-Write WOM-Codes
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Abstract:
A Write Once Memory (WOM) is a storage medium with binary
memory elements, called cells, that can change from the zero
state to the one state only once. Examples of WOMs are punch cards,
optical disks, and more recently flash memories. A t-write
WOM-code is a coding scheme for storing t messages in n cells in
such a way that each cell can change its value only from the zero
state to the one state. The WOM-rate of a t-write WOM-code is the
ratio of the total amount of information written to the WOM in t
writes to the number of cells.
In this paper we present a family of 2-write WOM-codes. It is
shown how to construct from each linear code C a 2-write
WOM-code. Then, we find 2-write WOM-codes that improve the best
known WOM-rate with two writes. This scheme is proved to be capacity
achieving when the parity check matrix of the linear code C is
chosen uniformly at random. Finally, we show how to take advantage
of 2-write WOM-codes in order to construct codes for the Blackwell
channel.
Mon 30 Aug, 17.00-17.20, Room 1
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Anxiao (Andrew) Jiang, Jehoshua Bruck, and Hao Li
Constrained Codes for Phase-change Memories
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Abstract:
Phase-change memories (PCMs) are an important emerging non-volatile
memory technology that uses amorphous and crystalline cell states to
store data. The cell states are switched using high temperatures. As
the semi-stable states of PCM cells are sensitive to temperatures,
scaling down cell sizes can bring significant challenges. We
consider two potential thermal-based interference problems as the
cell density approaches its limit, and study new constrained codes
for them.
Mon 30 Aug, 17.20-17.40, Room 1
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