Misalignment Compensation and Equalization for Holographic Data Storage

In a holographic data storage device, data are stored and retrieved as two-dimensional images. These images can be distorted in various ways. Generally, sync marks are used to acquire exact pixel values in a distorted image. However, this inevitably results in some loss of data density. In this research, a virtual detector that follows the rows of an image like a compact disk (CD) track is used to acquire the data pixels in a distorted image without sync marks. The proposed method can compensate for image distortion without any loss of data density. The feasibility of the new technique is demonstrated by simulation. The procedure is also evaluated on the basis of signal-to-noise ratio and bit error ratio.

Section: Data Acquisition For Hdssmentioning

confidence: 99%

Line Tracking Applied Data Acquisition Method for Holographic Data Storage System

Lee

Kim

Lim

et al. 2012

“…Therefore, some effective postprocessing schemes, which are called equalization techniques, have been proposed in HDS with conventional binary symbol datapages, enabling reliable retrieval of stored digital data. [13][14][15][16] In equalization techniques, equalizers are employed to reduce the effects of the intersymbol interference. [17][18][19] In general, careful modeling of underlying storage channel and sources of noise is typically required for constructing the equalizers.…”

Section: Introductionmentioning

confidence: 99%

Complex linear minimum mean-squared-error equalization of spatially quadrature-amplitude-modulated signals in holographic data storage

Sato

Kanno

Bunsen

2016

We applied complex linear minimum mean-squared-error equalization to spatially quadrature-amplitude-modulated signals in holographic data storage (HDS). The equalization technique can improve dispersion in constellation outputs due to intersymbol interference. We confirm the effectiveness of the equalization technique in numerical simulations and basic optical experiments. Our numerical results have shown that intersymbol interference of a retrieved signal in a HDS system can be improved by using the equalization technique. In our experiments, a mean squared error (MSE), which indicates the deviation from an ideal signal, has been used for quantitatively evaluating the dispersion of equalized signals. Our equalization technique has been able to improve the MSE. However, symbols in the equalized signal have remained inseparable. To further improve the MSE and make the symbols separable, reducing errors in repeated measurements is our future task.

“…2) In particular, the 2D ISI greatly degrades quality of the image. Considering the influence of the 2D ISI, several new approaches have been proposed for the data page reconstruction in recent years: a 2D equalizer, [3][4][5] 2D partial response maximum likelihood (PRML), 6,7) 2D PRML using constant-weight constraint, 8,9) 2D PRML based on 2D soft output Viterbi algorithm (SOVA), [10][11][12] decoding scheme based on turbo equalizer, 13,14) decoding scheme based on 2D modulation code, [15][16][17][18] decoding scheme based on tone controllable code, 19,20) correlation-based detection method, 21) 2D modulation code, [22][23][24] and tone controllable code. 25,26) In this paper, we focus on 2D PRML based on the 2D SOVA satisfying both superior performance and low computational complexity.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Soft Output Viterbi Algorithm with a Variable Reliability Factor for Holographic Data Storage

Koo

Kim

Jeong

et al. 2013

In a practical holographic data storage system, the reconstruction process for a data page should account for the processing time as well as the bit error rate (BER) performance. To improve both aspects, we introduce two-dimensional (2D) partial response maximum likelihood composed of a 2D partial response (PR) target including diagonal elements and a 2D soft output Viterbi algorithm (SOVA) with a variable reliability factor. The 2D SOVA performs two one-dimensional (1D) SOVAs in structural accordance with the 2D PR target where extrinsic information uses the expected value calculated on a synchronization pattern. Finally, the 2D SOVA exports a weighted average using the reliability factor that is updated similarly as the optimization scheme for each page. The simulation results show that the proposed method has superior BER performance, despite using only two 1D SOVAs as compared with the modified 2D SOVA composed of four 1D SOVAs.