565 research outputs found
Variable- and fixed-length balanced runlength-limited codes based on a Knuth-like balancing method
Abstract: A novel Knuth-like balancing method for runlengthlimited words is presented, which forms the basis of new variableand fixed-length balanced runlength-limited codes that improve on the code rate as compared to balanced runlength-limited codes based on Knuth’s original balancing procedure developed by Immink et al. While Knuth’s original balancing procedure, as incorporated by Immink et al., requires the inversion of each bit one at a time, our balancing procedure only inverts the runs as a whole one at a time. The advantage of this approach is that the number of possible inversion points, which needs to be encoded by a redundancy-contributing prefix/suffix, is reduced, thereby allowing a better code rate to be achieved. Furthermore, this balancing method also allows for runlength violating markers which improve, in a number of respects, on the optimal such markers based on Knuth’s original balancing method
Time-Space Constrained Codes for Phase-Change Memories
Phase-change memory (PCM) is a promising non-volatile solid-state memory
technology. A PCM cell stores data by using its amorphous and crystalline
states. The cell changes between these two states using high temperature.
However, since the cells are sensitive to high temperature, it is important,
when programming cells, to balance the heat both in time and space.
In this paper, we study the time-space constraint for PCM, which was
originally proposed by Jiang et al. A code is called an
\emph{-constrained code} if for any consecutive
rewrites and for any segment of contiguous cells, the total rewrite
cost of the cells over those rewrites is at most . Here,
the cells are binary and the rewrite cost is defined to be the Hamming distance
between the current and next memory states. First, we show a general upper
bound on the achievable rate of these codes which extends the results of Jiang
et al. Then, we generalize their construction for -constrained codes and show another construction for -constrained codes. Finally, we show that these two
constructions can be used to construct codes for all values of ,
, and
A joint coding concept for runlength and charge-limited channels
By making the conventional (d,k) constraint time dependent as a function of the channel process, the wide sense RLL channel has been defined. With the help of the new concept several existing constraints can be described alternatively and many new ones can be constructed. A bit stuff algorithm is suggested for coding wide sense RLL channels. We determine the rate of the bit stuff algorithm as the function of the stuffing probability. We present a few examples for calculating the rate of different constrained codes complying with the newly introduced constraint
Monte Carlo Algorithms for the Partition Function and Information Rates of Two-Dimensional Channels
The paper proposes Monte Carlo algorithms for the computation of the
information rate of two-dimensional source/channel models. The focus of the
paper is on binary-input channels with constraints on the allowed input
configurations. The problem of numerically computing the information rate, and
even the noiseless capacity, of such channels has so far remained largely
unsolved. Both problems can be reduced to computing a Monte Carlo estimate of a
partition function. The proposed algorithms use tree-based Gibbs sampling and
multilayer (multitemperature) importance sampling. The viability of the
proposed algorithms is demonstrated by simulation results
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