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In this paper, we present a deliberate bit flipping (DBF) coding scheme for binary two-dimensional (2-D) channels, where specific patterns in channel inputs are the significant cause of errors. The idea is to eliminate a constrained encoder and, instead, embed a constraint into an error correction codeword that is arranged into a 2-D array by deliberately flipping the bits that violate the constraint. The DBF method relies on the error correction capability of the code being used so that it should be able to correct both deliberate errors and channel errors. Therefore, it is crucial to flip minimum number of bits in order not to overburden the error correction decoder. We devise a constrained combinatorial formulation for minimizing the number of flipped bits for a given set of harmful patterns. The generalized belief propagation algorithm is used to find an approximate solution for the problem. We evaluate the performance gain of our proposed approach on a data-dependent 2-D channel, where 2-D isolated-bits patterns are the harmful patterns for the channel. Furthermore, the performance of the DBF method is compared with classical 2-D constrained coding schemes for the 2-D no isolated-bits constraint on a memoryless binary symmetric channel. [ABSTRACT FROM AUTHOR]

Two-dimensional magnetic recording (TDMR) is a promising technology for boosting areal densities (ADs) using sophisticated signal processing algorithms within a systems framework. The read/write channel architectures have to effectively tackle 2-D inter-symbol interference (ISI), 2-D synchronization errors, media and electronic noise sources, as well as thermal asperities resulting in burst erasures. The 1-D low-density parity check (LDPC) codes are well studied to correct large 1-D burst errors/erasures. However, such 1-D LDPC codes are not suitable for correcting 2-D burst errors/erasures due to the 2-D span of errors. In this paper, we propose construction of a native 2-D LDPC code to effectively correct 2-D burst erasures. We also propose a joint detection and decoding engine based on the generalized belief propagation algorithm to simultaneously handle 2-D ISI, as well as correct bit/burst errors for TDMR channels. This paper is novel in two aspects: 1) we propose the construction of native 2-D LDPC codes to correct large 2-D burst erasures and 2) we develop a 2-D joint signal detection-decoder engine that incorporates 2-D ISI constraints, and modulation code constrains along with LDPC decoding. The native 2-D LDPC code can correct >20% more burst erasures compared with the 1-D LDPC code over a 128 $\times $ 256 2-D page of detected bits. Also, the proposed algorithm is observed to achieve a signal-to-noise ratio gain of >0.5 dB in bit error rate performance (translating to 10% increase in ADs around the 1.8 Tb/in2 regime with grain sizes of 9 nm) as compared with a decoupled detector-decoder system configuration over a small 2-D LDPC code of size 16 $\times $ 16. The efficacy of our proposed algorithm and system architecture is evaluated by assessing AD gains via simulations for a TDMR configuration comprising of a 2-D generalized partial response over the Voronoi media model assuming perfect 2-D synchronization. [ABSTRACT FROM PUBLISHER]

The move from traditional single-track magnetic recording to two-dimensional magnetic recording (TDMR) with squeezed tracks and multiple readers opens up new design degrees of freedom beyond the track pitch and bit-aspect ratio, including the widths, spacing, and crosstrack positions of the readers. In this paper, we present a systematic method for determining the combination of multi-reader geometry, track pitch, and bit-aspect ratio that maximizes the areal density of a TDMR system using single-track detectors. The method combines realistic modeling of the medium and write/read processes, advanced signal detection, and information-theoretic tools. For the particular head and medium we consider, the two-reader geometry that maximizes areal density with zero skew and zero misregistration was found to use different-sized readers (the smaller having a full-width at half-maximum width, i.e., 96% of the track pitch and the larger having a width, i.e., 148% of the track pitch) with significant overlap in the crosstrack direction (centers spaced by one eighth of the track pitch). The optimal bit-aspect ratio was 2.2. At the optimal operating point, the information rate per coded bit is 0.8. [ABSTRACT FROM AUTHOR]

Two-dimensional magnetic recording 2-D (TDMR) is a promising technology for next generation magnetic storage systems based on a systems-level framework involving sophisticated signal processing at the core. The TDMR channel suffers from severe jitter noise along with electronic noise that needs to be mitigated during signal detection and recovery. Recently, we developed noise prediction-based techniques coupled with advanced signal detectors to work with these systems. However, it is important to understand the role of harmful patterns that can be avoided during the encoding process. In this paper, we investigate the Voronoi-based media model to study the harmful patterns over multitrack shingled recording systems. Through realistic quasi-micromagnetic simulation studies, we identify 2-D data patterns that contribute to high media noise. We look into the generic Voronoi model and present our analysis on multitrack detection with constrained coded data. We show that the 2-D constraints imposed on input patterns result in an order of magnitude improvement in the bit-error rate for the TDMR systems. The use of constrained codes can reduce the complexity of 2-D intersymbol interference (ISI) signal detection, since the lesser 2-D ISI span can be accommodated at the cost of a nominal code rate loss. However, a system must be designed carefully so that the rate loss incurred by a 2-D constraint does not offset the detector performance gain due to more distinguishable readback signals. [ABSTRACT FROM PUBLISHER]