Erozan M. Kurtas

Coding and signal processing for magnetic recording systems

RECORDING SYSTEMS A BriefHistory of Magnetic Storage, Dean Palmer Physics of Longitudinal and Perpendicular Recording, Hong Zhou, Tom Roscamp, Roy Gustafson, Eric Boernern, and Roy Chantrell The Physics of Optical Recording, William A. Challener and Terry W. McDaniel Head Design Techniques for Recording Devices, Robert E. Rottmayer COMMUNICATION AND INFORMATION THEORY OF MAGNETIC RECORDING CHANNELS Modeling the Recording Channel, Jaekyun Moon Signal and Noise Generation for Magnetic Recording Channel Simulations, Xueshi Yang and Erozan M. Kurtas Statistical Analysis of Digital Signals and Systems, Dragana Bajic and Dusan Drajic Partial Response Equalization with Application to High Density Magnetic Recording Channels, John G. Proakis An Introduction to Error-Correcting Codes, Mario Blaum. Message-Passing Algorithm, Sundararajan Sankaranarayanan and Bane Vasic Modulation Codes for Storage Systems, Brian Marcus and Emina Soljanin Information Theory of Magnetic Recording Channels, Zheng Zhang, Tolga M. Duman, and Erozan M. Kurtas Capacity of Partial Response Channels, Shaohua Yang and Aleksandar Kavcic INTRODUCTION TO READ CHANNELS Recording Physics and Organization of Data on a Disk Read Channels for Hard Drives, B. Vasic, P. Aziz, and N. Sayiner An Overview of Hard Drive Controller Functionality, Bruce Buch CODING FOR READ CHANNELS Runlength Limited Sequences, ees A. Schouhamer Immink Maximum Transition Run Coding, Barrett J. Brickner Spectrum Shaping Codes, Stojan Denic and Bane Vasic Introduction to Constrained Binary Codes with Error Correction Capability, Hendrik C. Ferreira and Willem A. Clarke Constrained Coding and Error-Control Coding, John L. Fan Convolutional Codes for Partial-Response Channels, Bartolomeu F. Uchoa-Filho, Mark A. Herro, Miroslav Despotovic and Vojin Senk Capacity-Approaching Codes for Partial Response Channels, Nedeljko Varnica, Xiao Ma, and Aleksandar Kavcic Coding and Detection for Multitrack Systems, Bane Vasic and Olgica Milenkovic Two-Dimensional Data Detection and Error Control, Brian M. King and Mark A. Neifeld SIGNAL PROCESSING FOR READ CHANNELS Adaptive Timing Recovery for Partial Response Channels, Pervez M. Aziz and Viswanath Annampedu Interpolated Timing Recovery, Piya Kovintavewat, John R. Barry, M. Fatih Erden, and Erozan M. Kurtas Adaptive Equalization Architectures for Partial Response Channels, Pervez M. Aziz Head Position Estimation, Ara Patapoutian Servo Signal Processing, Pervez M. Aziz Data Detection, Miroslav Despotovic and Vojin Senk Detection Methods for Data-dependent Noise in Storage Channels, Erozan M. Kurtas, Jongseung Park, Xueshi Yang, William Radich, and Aleksandar Kavcic Read/Write Channel Implementation, Borivoje Nikolic, Michael Leung, Engling Yeo, and Kiyoshi Fukahori ITERATIVE DECODING Turbo Codes, Mustafa N. Kaynak, Tolga M. Duman, and Erozan M. Kurtas An Introduction to LDPC Codes, William E. Ryani Concatenated Single-Parity Check Codes for High-Density Digital Recording Systems, Jing Li, Krishna R. Narayanan, Erozan Kurtas, and Travis R. Oenning Structured Low-Density Parity-Check Codes, Bane Vasic, Erozan M. Kurtas, Alexander Kuznetsov, and Olgica Milenkovic Turbo Coding for Multitrack Recording Channels, Zheng Zhang, Tolga M. Duman, and Erozan M. Kurtas INDEX

On the performance of high-rate TPC/SPC codes and LDPC codes over partial response channels

This paper evaluates two-dimensional turbo product codes based on single-parity check codes (TPC/SPC) and low-density parity check (LDPC) codes for use in digital magnetic recording systems. It is first shown that the combination of a TPC/SPC code and a precoded partial response (PR) channel results in a good distance spectrum due to the interleaving gain. Then, density evolution is used to compute the thresholds for TPC/SPC codes and LDPC codes over PR channels. Analysis shows that TPC/SPC codes have a performance close to that of LDPC codes for large codeword lengths. Simulation results for practical block lengths show that TPC/SPC codes perform as well as LDPC codes in terms of bit error rate, but possess better burst error statistics which is important in the presence of an outer Reed-Solomon code. Further, the encoding complexity of TPC/SPC codes is only linear in the codeword length and the generator matrix does not have to be stored explicitly. Based on. the results in the paper and these advantages, TPC/SPC codes seem like a viable alternative to LDPC codes.

Generalized partial-response targets for perpendicular recording with jitter noise

In this paper, we propose new generalized partial-response (GPR) targets for perpendicular recording whose transition response is modeled as an error function and compare their performance with the partial-response (PR) targets both in the presence and absence of jitter noise. Regardless of any jitter noise amount, results indicate that the GPR targets outperform the PR targets, especially at high linear-recording densities. We also determine that the dominant error sequence for this perpendicular recording is the same for all targets when jitter noise is low. Therefore, the system performance can be further improved by designing and using codes to avoid this dominant error sequence. Another significant point is the fact that the dominant error sequence of perpendicular recording is different from longitudinal recording, thus requiring design of different types of codes than the ones used for longitudinal recording. Finally, we show that the effective signal-to-noise ratio can be equivalently used instead of the bit-error-rate as a measure to compare the performance of different targets.

Kirkman systems and their application in perpendicular magnetic recording

A novel class of a very high-rate low-density parity check codes is introduced, and investigated in the context of its application in a perpendicular magnetic recording system. New codes are well structured and, unlike random codes, can lead to a very low-complexity implementation. A systematic way of constructing codes is based on Kirkman systems. A hardware efficient encoding algorithm is proposed. The bit-error-rate characteristics are characterized by simulation of the soft iterative decoding in perpendicular magnetic read channel with different partial response targets and types of noise.

Achievable information rates and coding for MIMO systems over ISI channels and frequency-selective fading channels

We propose a simulation-based method to compute the achievable information rates for general multiple-input multiple-output (MIMO) intersymbol interference (ISI) channels with inputs chosen from a finite alphabet. This method is applicable to both deterministic and stochastic channels. As an example of the stochastic MIMO ISI channels, we consider the multiantenna systems over frequency-selective fading channels, and quantify the improvement in the achievable information rates provided by the additional frequency diversity (for both ergodic and nonergodic cases). In addition, we consider the multiaccess multiantenna system and present some results on the achievable information-rate region. As for the deterministic MIMO ISI channels, we use the binary-input multitrack magnetic recording system as an example, which employs multiple write and read heads for data storage. Our results show that the multitrack recording channels have significant advantages over the single-track channels, in terms of the achievable information rates when the intertrack interference is considered. We further consider practical coding schemes over both stochastic and deterministic MIMO ISI channels, and compare their performance with the information-theoretical limits. Specifically, we demonstrate that the performance of the turbo coding/decoding scheme is only about 1.0 dB away from the information-theoretical limits at a bit-error rate of 10/sup -5/ for large interleaver lengths.

System perspectives for the application of structured LDPC codes to data storage devices

We have three main goals in this paper. First, we will show the equivalences and relationships among some of the well-known classes of structured low density parity check (LDPC) codes. Second, we consider application of these codes to magnetic recording channel. We will make performance comparisons not only with bit-error-rate (BER) metric but also with sector failure rate (SFR) as the comparison dimension. Such a comparison is more meaningful from a system analysis perspective. Finally, we consider the case of these structured LDPC codes concatenated with conventional Reed-Solomon (RS) codes. We believe LDPC codes will not completely replace RS codes in the future storage devices. From this perspective, for LDPC codes to be contenders for future architectures, they will need to work in harmony with the outer RS codes. This implies that we have to take into account the redundancy introduced by the overall coding scheme, that is, RS code in concatenation with LDPC code, to reach meaningful comparisons from a system design perspective.

LDPC codes based on mutually orthogonal latin rectangles and their application in perpendicular magnetic recording

We present a large family of low-density parity-check (LDPC) codes constructed from mutually orthogonal Latin rectangles. The construction is conceptually simple and gives high-rate LDPC codes with a structure of the parity check matrix that leads to a low complexity implementation of encoders and decoders. The bit-error rate characteristics are characterized by simulations of the soft iterative decoding in perpendicular magnetic read channels with different partial-response targets and types of noise.

Performance bounds for high rate linear codes over partial response channels

We develop union bounds for high-rate linear codes used for partial-response equalized channels with additive white Gaussian noise. The bounds assume uniform interleaving and are based on an approximation which is valid for high-rate linear codes. Furthermore, the derivation of the bounds assumes that maximum-likelihood decoding is employed. One particular application of the present setting is the computation of bounds for magnetic recording systems using turbo codes. The results can be considered as a generalization of the results of M. Oberg and P.H. Siegel (see Proc. Allerton Conf. Communications, Control and Computing, Sept. 1998) which develops the union bound for the dicode channel; however, our approach is completely different. We present several examples of the bounds developed together with the simulation results.

Per-survivor timing recovery for uncoded partial response channels

A conventional receiver performs timing recovery and equalization separately. Specifically, conventional timing recovery is based on a phase-locked loop that relies on the decision provided by its own symbol detector. We propose a new timing recovery scheme based on per-survivor processing (PSP) that jointly performs timing recovery and equalization for uncoded partial response channels. In the proposed scheme, each survivor of the Viterbi algorithm maintains its own estimate of the timing offset, and this estimate is updated according to the history data associated with the survivor path. As compared to conventional timing recovery at BER = 10/sup -4/, the proposed scheme can provide a 0.5 dB gain in SNR.

Belief Propagation over SISO/MIMO Frequency Selective Fading Channels

In this letter, we propose an iterative belief propagation (BP) channel detector (equalizer) over single-input single- output (SISO) and multiple-input multiple-output (MIMO) frequency selective fading channels as an alternative to the typically used maximum a-posteriori (MAP) or maximum likelihood (ML) detectors. The proposed detector has a parallel structure, resulting in fast hardware implementations. Moreover, BP detector is less complex than the MAP detector and it has a short decoding delay. We analyze the bit error rate and the mutual information and show that, over frequency selective fading channels, the proposed BP detector achieves a near-optimal performance, even in the presence of the length 4 cycles in the corresponding channel factor graph.