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

Abstract

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.