Conference Paper

On guided scrambling with guaranteed maximum run-length constraints

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Methods are developed to effectively combine guided scrambling and maximum run-length limited codes in order to impose a guaranteed maximum run-length constraint. It will be demonstrated that the combination of guided scrambling and a well-chosen maximum run-length limited code may offer a sound trade-off between overall code rate and performance in terms of the probability of violating the channel constraints.

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Conference Paper
In order to minimize the interference between adjacent data arrays recorded in the same holographic volume, the patterns of 1's and 0's in each data array should be t- conservative, i.e., for a prescribed integer t, there should be at least t transitions of the form 1 rarr 0 or 0 rarr 1 in each column and row of the data array. In this paper, we present extensions to the algorithm proposed by Vardy et al. for encoding unconstrained binary arrays into t-conservative arrays. We set our work in the context of multimode codes. The multimode encoding process involves adding each input array to a set of control arrays to form a selection set, and selecting one that "best" satisfies the predefined selection criterion. We propose a new approach for construction of the control arrays, and demonstrate how the algorithm proposed by Vardy et al. is a special case of this approach. We also propose a novel approach for embedding the index of the control arrays into the encoded array, and propose alternatives for array selection.
This paper addresses a new scheme by Vasic and Pedagani to combine low-density parity-check (LDPC) codes with run length limited (RLL) constraints. In this method, the RLL constraints are embedded into the LDPC codewords by deliberately flipping the bits of LDPC codewords that violate the RLL constraints. It is important to keep the number of flipped bits small in order to not overburden the LDPC decoder. In this paper, we introduce a method to control the number of flipped bits by using pseudorandom sequences. We present a new low-complexity iterative decoding and detection scheme to correct both the flipped bits and channel errors in a partial response channel. Analyses and simulation results show that the proposed method has good performance and reasonable complexity for (0,k) RLL constraints.
The bit-error rate (BER) of a storage or transmission channel may be data-dependent. This can lead to certain pathological input sequences, for which the reliability of the system is below specifications. Guided scrambling is a well-known technique to randomize the input to a channel while minimizing a certain objective function. In this paper, we take the average predicted BER as the objective function. We show that for a certain scrambling code C, for any input sequence m there exists a scrambling codeword c∈C such that the predicted BER of the (modulo-2) sum of m and c is not more than that for random input data. We present examples of scrambling codes for two-dimensional optical storage and indicate a way of combining them with error-correcting codes.
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Preface to the Second Edition About five years after the publication of the first edition, it was felt that an update of this text would be inescapable as so many relevant publications, including patents and survey papers, have been published. The author's principal aim in writing the second edition is to add the newly published coding methods, and discuss them in the context of the prior art. As a result about 150 new references, including many patents and patent applications, most of them younger than five years old, have been added to the former list of references. Fortunately, the US Patent Office now follows the European Patent Office in publishing a patent application after eighteen months of its first application, and this policy clearly adds to the rapid access to this important part of the technical literature. I am grateful to many readers who have helped me to correct (clerical) errors in the first edition and also to those who brought new and exciting material to my attention. I have tried to correct every error that I found or was brought to my attention by attentive readers, and seriously tried to avoid introducing new errors in the Second Edition. China is becoming a major player in the art of constructing, designing, and basic research of electronic storage systems. A Chinese translation of the first edition has been published early 2004. The author is indebted to prof. Xu, Tsinghua University, Beijing, for taking the initiative for this Chinese version, and also to Mr. Zhijun Lei, Tsinghua University, for undertaking the arduous task of translating this book from English to Chinese. Clearly, this translation makes it possible that a billion more people will now have access to it. Kees A. Schouhamer Immink Rotterdam, November 2004
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We present advanced combinatorial techniques for constructing maximum runlength-limited (RLL) block codes and maximum transition run (MTR) codes. These codes find widespread application in recording systems. The proposed techniques are used to construct a high-rate multipurpose modulation code for recording systems. The code, a rate 16/17, (0,3,2,2) MTR code, that also fulfills (0,15,9,9) RLL constraints is a high-rate distance-enhancing code with additional constraints for improving timing and gain control. The encoder and decoder have a particularly efficient architecture and allow an instantaneous translation of 16-bit source words into 17-bit codewords and vice versa. The code has been implemented in Lucent read-channel chips and has excellent performance
Conference Paper
New combinatorial construction techniques are proposed which convert binary user information into a (0,k) constrained sequence having the virtue that at most k `zeroes' between logical `ones' will occur. In this way sequences are constructed which have a limited runlength. These codes find application in optical and magnetic recording systems. The new construction methods provide efficient, high rate codes with a low complexity. The low complex combinatorial structure of the encoder and the decoder ensure a very fast and efficient parallel conversion of binary information to codewords and vice versa. Specifically, we present the combinatorial structures to convert 16 data bits into a 17 bit constrained sequence to obtain an optimum (0,4) code, a (0,6) code with at most one byte error propagation, and a (0,6/6)-code, respectively. Serious error propagation is avoided by using constrained codes with several unconstrained positions, which are reserved to store the parity bits of an error control code which protects the constrained codeword
Rate 32/33, ?? ???? ? ?? runlength limited modulation code having optimized error propagation
  • A Patapoutian
  • J Stander
  • P Mcewen
  • B Zafer
  • J Fitzpatrick
A. Patapoutian, J. Stander, P. McEwen, B. Zafer, and J. Fitzpatrick, “Rate 32/33, ?? ???? ? ?? runlength limited modulation code having optimized error propagation”, US Patent 6,184,806, Feb. 2001.