Holographic Data Storage Channel Research Articles

Simplified Two-Dimensional Generalized Partial Response Target of Holographic Data Storage Channel

With a high capacity and fast data access rate, holographic data storage (HDS) is a potential candidate for future storage systems. However, for page-oriented data processing, two-dimensional (2D) interference appears intensely in the HDS systems. Therefore, the new 2D generalized partial response (GPR) target is introduced to estimate the 2D interference. In addition, we also propose a method to analyze the 2D GPR target into two serial one-dimensional (1D) GPR targets. It makes us design a simple detection scheme composed of two serial 1D detectors instead of a complicated 2D detector. In simulations, the results show that our proposed scheme can improve the BER performance compared to the conventional 1D GPR target model.

Two-Dimensional Interference Estimator with Parallel Structure for Holographic Data Storage Channel

Recently, holographic data storage (HDS) has attracted significant attention as the next-generation storage technology because of its large capacity and high-speed transfer capabilities. However, two-dimensional (2D) inter-symbol interference (ISI) is a critical problem encountered in HDS. Therefore, in this study, we propose a 2D interference estimator to prevent the 2D ISI. In addition, we propose a parallel structure to exploit horizontal interference (HI) and vertical interference (VI) effectively. After detecting the HI and VI, the signal is combined using an average function. The simulation results indicate that the proposed model can significantly improve the performance of HDS.

Reed–Solomon Volumetric Coding with Matched Interleaving for Holographic Data Storage

For various error patterns, including random errors, burst errors, and inhomogeneously distributed errors, in the holographic data storage (HDS) channel, a Reed–Solomon volumetric coding with matched interleaving (RSVC-MI) scheme is proposed in this paper. The RSVC-MI scheme combines the advantages of the RSVC scheme and the matched interleaving scheme, makes full use of the priori knowledge of the error patterns in the HDS channel, distributes errors more uniformly, and decodes data iteratively in three dimensions. It is able to eliminate the influences of non-uniform distribution of errors within a page and across pages, overcome the effects of burst errors, correct random errors, and effectively reduce the symbol error rate (SER) of the HDS channel.

Soft-Encoding Scheme of 3/4 Tone-Controllable Code for Channel Iteration of Low-Density Parity-Check Code on the Holographic Data Storage

In turbo equalization for holographic data storage (HDS) systems, an iterate-back signal must pass through a modulation coding process for channel iteration since the iterate-back signal is a demodulated signal and the input of a detector is modulated data. Also, the iterate-back signal is a soft-value, so the soft-input and soft-output (SISO) must be treated by a modulation code. A 3/4 tone-controllable (TC) code can control the ratio of ON and OFF pixels on each data page. The memory capacity of a holographic data storage system can be increased if we use a TC code. In this paper, we concatenate a 3/4 TC code and LDPC code, and then simulate the turbo equalization performance on a HDS channel. A SISO 3/4 TC code is needed for this simulation. Therefore, we propose a soft-encoding scheme for a SISO 3/4 TC code.

Reed–Solomon Volumetric Coding with Matched Interleaving for Holographic Data Storage

For various error patterns, including random errors, burst errors, and inhomogeneously distributed errors, in the holographic data storage (HDS) channel, a Reed–Solomon volumetric coding with matched interleaving (RSVC-MI) scheme is proposed in this paper. The RSVC-MI scheme combines the advantages of the RSVC scheme and the matched interleaving scheme, makes full use of the priori knowledge of the error patterns in the HDS channel, distributes errors more uniformly, and decodes data iteratively in three dimensions. It is able to eliminate the influences of non-uniform distribution of errors within a page and across pages, overcome the effects of burst errors, correct random errors, and effectively reduce the symbol error rate (SER) of the HDS channel.

Holographic Data Storage Channel Model With Intensity Factor

We consider the holographic data storage channel model which includes intensity factor. We define the intensity factor as the degree of the diminishing phenomenon of the read page and model the diminishing phenomenon using a simple page masking filter. Thus, the page masking filter coefficients are determined by the intensity factor. We discuss the performance of the channel model employing one-dimensional (1-D) PRML with two-dimensional (2-D) PR equalizer when the degree of blur is 1.7.

Partial Response Maximum Likelihood Detections Using Two-Dimensional Soft Output Viterbi Algorithm with Two-Dimensional Equalizer for Holographic Data Storage

We present partial response maximum likelihood (PRML) detection with two-dimensional (2D) equalizer scheme and introduce 2D soft output Viterbi algorithm (SOVA) detection for holographic data storage (HDS) channel. We also propose the 2D PR target for the HDS channel varying the grade of blur. Simulation results show that the proposed schemes outperform the nearest neighbor detection.

Linear Signal Processing for a Holographic Data Storage Channel Using Coherent Addition

A linear channel model and a linear signal processing technique are available for a holographic data storage channel when our proposed coherent addition technique is applied to the reproduction process. As a result, the signal-to-noise ratio (SNR) after zero-interpixel-interference (IPI) equalization is markedly improved. Moreover, we can achieve a higher transfer rate at a lower oversampling rate owing to the almost ideal linearity of the reproduced signal.

Linear Reproduction of a Holographic Storage Channel using Coherent Addition of Optical DC Components

A holographic data storage channel is normally a nonlinear channel; however, it can be made linear. Using coherent addition of DC components in the reproduction process and calculating the square root of intensity, we can retrieve a linearly reproduced signal. Our simulation results revealed that a conventional equalizer works well to suppress interpixel interference so that a higher recording density can be achieved.

Two-Dimensional Equalization and Error Correction Using Low Density Parity Check Codes for Holographic Data Storage

This paper discusses two-dimensional (2-D) minimum mean squared error equalization in conjunction with low density parity check (LDPC) error correction codes for holographic data storage (HDS). HDS channel simulator that accommodates several impairments such as contrast ratio, fill factors, optical and electronic noise is used to generate data pages for our investigation. Signal-to-noise ratio (SNR) is varied by adjusting cumulative noise variance and inter-symbol interference is varied by changing frequency plane aperture size. We investigate the performance of equalization followed by LDPC decoder for various aperture sizes and various SNRs. Smallest aperture size at each of these SNRs was identified based on data decodability. It is observed that for some of the apertures, equalization resulted in decoding without errors after 12 iterations whereas not using an equalizer would have resulted in several errors even after 25 iterations.