Detection and Decoding for Magnetic Storage Systems
Detection and Decoding for Magnetic Storage Systems

Author:

Publisher:

Published: 2009

Total Pages: 344

ISBN-13:

DOWNLOAD EBOOK

The hard-disk storage industry is at a critical time as the current technologies are incapable of achieving densities beyond 500 Gb/in2, which will be reached in a few years. Many radically new storage architectures have been proposed, which along with advanced signal processing algorithms are expected to achieve much higher densities. In this dissertation, various signal processing algorithms are developed to improve the performance of current and next-generation magnetic storage systems. Low-density parity-check (LDPC) error correction codes are known to provide excellent performance in magnetic storage systems and are likely to replace or supplement currently used algebraic codes. Two methods are described to improve their performance in such systems. In the first method, the detector is modified to incorporate auxiliary LDPC parity checks. Using graph theoretical algorithms, a method to incorporate maximum number of such checks for a given complexity is provided. In the second method, a joint detection and decoding algorithm is developed that, unlike all other schemes, operates on the non-binary channel output symbols rather than input bits. Though sub-optimal, it is shown to provide the best known decoding performance for channels with memory more than 1, which are practically the most important. This dissertation also proposes a ternary magnetic recording system from a signal processing perspective. The advantage of this novel scheme is that it is capable of making magnetic transitions with two different but predetermined gradients. By developing optimal signal processing components like receivers, equalizers and detectors for this channel, the equivalence of this system to a two-track/two-head system is determined and its performance is analyzed. Consequently, it is shown that it is preferable to store information using this system, than to store using a binary system with inter-track interference. Finally, this dissertation provides a number of insights into the unique characteristics of heat-assisted magnetic recording (HAMR) and two-dimensional magnetic recording (TDMR) channels. For HAMR channels, the effects of laser spot on transition characteristics and non-linear transition shift are investigated. For TDMR channels, a suitable channel model is developed to investigate the two-dimensional nature of the noise.

Coding and Iterative Detection for Magnetic Recording Channels
Coding and Iterative Detection for Magnetic Recording Channels

Author: Zining Wu

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 165

ISBN-13: 146154565X

DOWNLOAD EBOOK

The advent of the internet age has produced enormous demand for in creased storage capacity and for the consequent increases in the amount of information that can be stored in a small space. While physical and media improvements have driven the majority of improvement in modern storage systems, signal processing and coding methods have increasing ly been used to augment those improvements. Run-length-limited codes and partial-response detection methods have come to be the norm in an industry that once rejected any sophistication in the read or write pro cessing circuits. VLSI advances now enable increasingly sophisticated signal processing methods for negligible cost and complexity, a trend sure to continue even as disk access speeds progress to billions of bits per second and terabits per square inch in the new millennium of the in formation age. This new book representing the Ph. D. dissertation work of Stanford's recent graduate Dr. Zining Wu is an up-to-date and fo cused review of the area that should be of value to those just starting in this area and as well those with considerable expertise. The use of saturation recording, i. e. the mandated restriction of two-level inputs, creates interesting twists on the use of communica tion/transmission methods in recording.

Advanced Error Control Techniques for Data Storage Systems
Advanced Error Control Techniques for Data Storage Systems

Author: Erozan M. Kurtas

Publisher: CRC Press

Published: 2018-10-03

Total Pages: 288

ISBN-13: 1420036491

DOWNLOAD EBOOK

With the massive amount of data produced and stored each year, reliable storage and retrieval of information is more crucial than ever. Robust coding and decoding techniques are critical for correcting errors and maintaining data integrity. Comprising chapters thoughtfully selected from the highly popular Coding and Signal Processing for Magnetic Recording Systems, Advanced Error Control Techniques for Data Storage Systems is a finely focused reference to the state-of-the-art error control and modulation techniques used in storage devices. The book begins with an introduction to error control codes, explaining the theory and basic concepts underlying the codes. Building on these concepts, the discussion turns to modulation codes, paying special attention to run-length limited sequences, followed by maximum transition run (MTR) and spectrum shaping codes. It examines the relationship between constrained codes and error control and correction systems from both code-design and architectural perspectives as well as techniques based on convolution codes. With a focus on increasing data density, the book also explores multi-track systems, soft decision decoding, and iteratively decodable codes such as Low-Density Parity-Check (LDPC) Codes, Turbo codes, and Turbo Product Codes. Advanced Error Control Techniques for Data Storage Systems offers a comprehensive collection of theory and techniques that is ideal for specialists working in the field of data storage systems.

Coding and Signal Processing for Magnetic Recording Systems
Coding and Signal Processing for Magnetic Recording Systems

Author: Bane Vasic

Publisher: CRC Press

Published: 2004-11-09

Total Pages: 742

ISBN-13: 0203490312

DOWNLOAD EBOOK

Implementing new architectures and designs for the magnetic recording read channel have been pushed to the limits of modern integrated circuit manufacturing technology. This book reviews advanced coding and signal processing techniques and architectures for magnetic recording systems. Beginning with the basic principles, it examines read/write operations, data organization, head positioning, sensing, timing recovery, data detection, and error correction. It also provides an in-depth treatment of all recording channel subsystems inside a read channel and hard disk drive controller. The final section reviews new trends in coding, particularly emerging codes for recording channels.

Constrained Coding and Signal Processing for Data Storage Systems
Constrained Coding and Signal Processing for Data Storage Systems

Author: Sharon Aviran

Publisher:

Published: 2006

Total Pages: 136

ISBN-13:

DOWNLOAD EBOOK

Constrained codes for digital storage systems are studied. A method for improving signal detection in digital magnetic recording systems is also investigated. The bit stuffing algorithm is a technique for coding constrained sequences by the insertion of bits into an arbitrary data sequence. This approach was previously introduced and applied to the family of $(d, k)$ constraints. Results show that the maximum average rate of the bit stuffing code achieves the Shannon capacity when $k=d+1$ or $k=\infty$, and fails to achieve capacity for all other $(d, k)$ pairs. A modification to the bit stuffing algorithm is proposed that is based on the addition of controlled bit flipping. It is shown that the modified scheme achieves improved average rates over bit stuffing for most $(d, k)$ constraints. All $(d, k)$ constraints for which this scheme produces codes with an average rate equal to the Shannon capacity are determined. A general framework for the construction of $(d, k)$-constrained codes from variable-length source codes is presented. Optimal variable-length codes under the general framework are investigated. The construction of constrained codes from variable-length source codes for encoding unconstrained sequences of independent but biased (as opposed to equiprobable) bits is also considered. It is shown that one can use the Tunstall source coding algorithm to generate optimal codes for a partial class of $(d, k)$ constraints. Bit-stuffing schemes which encode arbitrary inputs into two-dimensional (2-D) constrained arrays are presented. The class of 2-D $(d, \infty)$ constraints as well as the `no isolated bits' constraint are considered. The proposed schemes are based on interleaving biased bits with multiple biases into a 2-D array, while stuffing extra bits when necessary. The performance of the suggested schemes is studied through simulations. A method for joint detection and decoding of coded transmission over magnetic recording channels is considered. The standard framework of turbo equalization is modified to account for the colored noise present in high-density magnetic recording systems. The modified scheme incorporates a noise prediction algorithm, which iteratively and selectively whitens the noise, while utilizing the information produced by the turbo equalization scheme. Simulation results demonstrate the performance improvements obtained by the proposed scheme.

Detection and Decoding Algorithms for Nanoscale Data Storage
Detection and Decoding Algorithms for Nanoscale Data Storage

Author: Thomas P. Parnell

Publisher:

Published: 2010

Total Pages:

ISBN-13:

DOWNLOAD EBOOK

Scanning probe technology can be used for the modification of surfaces on the nanoscale and therefore has potential applications for data storage: data can be stored as a sequence of indentations in a polymer medium for example. In order to achieve the throughput requirements of a modern storage device the proposed probe storage systems consist of large arrays of probes reading/writing/erasing data in parallel. One of the most important tasks when designing a commercial storage device is to ensure that data can always be retrieved with a very low probability of error. The small scales offered by probe storage can potentially allow very high areal densities of information storage (larger than 1Tbit/in2) but there is a price to pay: many distortions arise when trying to retrieve this data (positioning errors for example) that make it harder to determine the correct information originally stored by the user. This thesis is concerned with signal processing for probe storage. Firstly channel models are developed for the read-back signal from a probe storage device that take into account the various distortions that occur. These models are then used for the design of probabilistic data detection algorithms and error-correcting codes that ensure the probability of error associated with data retrieval is sufficiently low. These intensively mathematical algorithms are designed with their complexity in mind to ensure they allow an implementation that satisfies the silicon area, power and timing constraints of a highly parallelized probe storage device. Making use of the tools provided by such fields as information theory, probability theory and asymptotic analysis the performance of these signal processing algorithms is studied theoretically and fundamental limits concerning the performance of a probe storage device are computed. The system-level implications of these results are carefully considered.

Essentials of Error-Control Coding Techniques
Essentials of Error-Control Coding Techniques

Author: Hideki Imai

Publisher: Academic Press

Published: 2014-06-28

Total Pages: 348

ISBN-13: 1483259374

DOWNLOAD EBOOK

Essentials of Error-Control Coding Techniques presents error-control coding techniques with an emphasis on the most recent applications. It is written for engineers who use or build error-control coding equipment. Many examples of practical applications are provided, enabling the reader to obtain valuable expertise for the development of a wide range of error-control coding systems. Necessary background knowledge of coding theory (the theory of error-correcting codes) is also included so that the reader is able to assimilate the concepts and the techniques. The book is divided into two parts. The first provides the reader with the fundamental knowledge of the coding theory that is necessary to understand the material in the latter part. Topics covered include the principles of error detection and correction, block codes, and convolutional codes. The second part is devoted to the practical applications of error-control coding in various fields. It explains how to design cost-effective error-control coding systems. Many examples of actual error-control coding systems are described and evaluated. This book is particularly suited for the engineer striving to master the practical applications of error-control coding. It is also suitable for use as a graduate text for an advanced course in coding theory.

LDPC Coding for Magnetic Storage: Low Floor Decoding Algorithms, System Design and Performance Analysis
LDPC Coding for Magnetic Storage: Low Floor Decoding Algorithms, System Design and Performance Analysis

Author: Yang Han

Publisher:

Published: 2008

Total Pages: 300

ISBN-13:

DOWNLOAD EBOOK

Low-density parity check (LDPC) codes have experienced tremendous popularity due to their capacity-achieving performance. In this dissertation, several different aspects of LDPC coding and its applications to magnetic storage are investigated. One of the most significant issues that impedes the use of LDPC codes in many systems is the error-rate floor phenomenon associated with their iterative decoders. By delineating the fundamental principles, we extend to partial response channels algorithms for predicting the error rate performance in the floor region for the binary-input AWGN channel. We develop three classes of decoding algorithms for mitigating the error floor by directly tackling the cause of the problem: trapping sets. In our experiments, these algorithms provide multiple orders of improvement over conventional decoders at the cost of various implementation complexity increases. Product codes are widely used in magnetic recording systems where errors are both isolated and bursty. A dual-mode decoding technique for Reed-Solomon-code-based product codes is proposed, where the second decoding mode involves maximum-likelihood erasure decoding of the binary images of the Reed-Solomon codewords. By exploring a tape storage application, we demonstrate that this dual-mode decoding system dramatically improves the performance of product codes. Moreover, the complexity added by the second decoding mode is manageable. We also show the performance of this technique on a product code which has an LDPC code in thecolumns. Run-length-limited (RLL) codes are ubiquitous in today's disk drives. Using RLL codes has enabled drive designers to pack data very efficiently onto the platter surface by ensuring stable symbol-timing recovery. We consider a concatenation system design with an LDPC code and an RLL code as components to simultaneously achieve desirable features such as: soft information availability to the LDPC decoder, the preservation of the LDPC code's structure, and the capability of correcting long erasure bursts. We analyze the performance of LDPC-coded magnetic recording channel in the presence of media noise. We employ advanced signal processing for the pattern-dependent-noise-predictive channel detectors, and demonstrate that a gain of over 1 dB or a linear density gain of about 8% relative to a comparable Reed-Solomon is attainable by using an LDPC code.