Kees A. Schouhamer Immink

A practical method for approaching the channel capacity of constrained channels

A new coding technique is proposed that translates user information into a constrained sequence using very long codewords. Huge error propagation resulting from the use of long codewords is avoided by reversing the conventional hierarchy of the error control code and the constrained code. The new technique is exemplified by focusing on (d, k)-constrained codes. A storage-effective enumerative encoding scheme is proposed for translating user data into long dk sequences and vice versa. For dk runlength-limited codes, estimates are given of the relationship between coding efficiency versus encoder and decoder complexity. We show that for most common d, k values, a code rate of less than 0.5% below channel capacity can be obtained by using hardware mainly consisting of a ROM lookup table of size 1 kbyte. For selected values of d and k, the size of the lookup table is much smaller. The paper is concluded by an illustrative numerical example of a rate 256/466, (d=2, k=15) code, which provides a serviceable 10% increase in rate with respect to its traditional rate 1/2, (2, 7) counterpart.

EFMplus: the coding format of the multimedia compact disc

Reports on an alternative to eight-to-fourteen modulation (EFM), called EFMPlus, which has been adopted as coding format of the multimedia compact disc proposal. The rate of the new code is 8/16, which means that a 6-7 % higher information density can be obtained. EFMPlus is the spitting image of EFM (same minimum and maximum runlength, clock content etc). Computer simulations have shown that the low-frequency content of the new code is only slightly larger than its conventional EFM counterpart. >

Runlength-limited sequences

Runlength-limited (RLL) sequences are formally defined, and the runlength distribution and spectral properties of ideal RLL sequences are analyzed. A detailed description is furnished of the limiting properties of RLL sequences, and a comprehensive review is given of the practical aspects involved in the translation of arbitrary data into RLL sequences. Examples of code implementation are presented to illustrate the variety of possible design tools. >

Coding techniques for the noisy magnetic recording channel: a state-of-the-art report

Coding techniques for improving the reliability of information storage on noisy magnetic recording channels are considered. It is assumed that the Lorentzian channel model applies and that the retrieved signal is perturbed with additive white Gaussian noise. The immunity against additive noise of state-of-the-art codes such as DC-free, runlength-limited, and trellis codes are assessed. >

A generalized method for encoding and decoding run-length-limited binary sequences (Corresp.)

Many modulation systems used in magnetic and optical recording are based on binary run-length-limited codes. We generalize the concept of dk -limited sequences of length n introduced by Tang and Bald by imposing constraints on the maximum number of consecutive zeros at the beginning and the end of the sequences. It is shown that the encoding and decoding procedures are similar to those of Tang and Bald. The additional constraints allow a more efficient merging of the sequences. We demonstrate two constructions of run-length-limited codes with merging rules of increasing complexity and efficiency and compare them to Tang and Bahls method.

Binary transmission codes with higher order spectral zeros at zero frequency (Corresp.)

A method is presented for designing binary channel codes in such a way that both the power spectral density function and its low-order derivatives vanish at zero frequency. The performance of the new codes is compared with that of channel codes designed with a constraint on the unbalance Of the number of transmitted positive and negative pulses. Some remarks are made on the error-correcting capabilities of these codes.

The Digital Versatile Disc (DVD): System Requirements and Channel Coding

The digital versatile disc (DVD) is a new optical recording medium with a storage capacity seven times higher than the conventional compact disc (CD). The major part of the capacity increase is achieved by the use of optics, shorter laser wavelength, and larger numerical aperture, which reduces the spot diameter by a factor of 1.65. The track formed by the recorded pits and lands, as well as the track pitch, can be reduced by the same factor. The storage capacity is further increased by a complete redesign of the logical format of the disc, including a more powerful error correction and recording code. The system requirements of the DVD and the related channel coding are outlined in this paper.

Design techniques for weakly constrained codes

A general method of constructing run-length limited (d, k) constrained codes from arbitrary sequences is introduced. This method is then combined with the method of guided scrambling for constructing a class of weakly constrained codes. The proposed codes are analyzed for the case of d=0 and are shown to give results which are better or comparable to those of the best available codes, however, at the cost of failure with some very low probability. For d>0, the code efficiency of the codes constructed according to the proposed method reduces significantly.

A survey of codes for optical disk recording

We report on 20 years of development of codes for optical disk recording systems. A description of the state-of-the-art and feasible options for future extensions and improvements are given.

Block-Decodable Runlength-Limited Codes via Look-Ahead Technique

The terms (d,k)·constrained sequence and runlength-Iimited (RLL) sequence are usually used as synonyms, and traditionally the design of encoders that generate RLL sequences is almost always conducted by designing encoders that generate (d,k)-constrained sequences followed by a precoder. It is generally believed that this design procedure does not entail a loss of performance in terms of coder complexity and error propagation. In this paper, however, we will show that it is surprisingly profitable in terms of error propagation to design RLL encoders directly, i.e. without the intermediate step of a (d,k)-constrained sequence.