Exploiting LDPC coding to improve data reliability for phase modulated holographic storage

Abstract

Volume holographic storage with high storage density and access rate has excellent potential for large-scale data storage. However, data reliability is facing challenges and has become a main concern from various noise interference. In holographic storage systems with phase modulated, high raw bit error rates (RBER) are induced by optical noise, electrical noise, intra and inter page interference, reducing data reliability. In this paper, we exploits low-density parity-check (LDPC) coding with remarkable error correction capability to improve data reliability and capacity with minimizing read latency for phase modulated holographic storage. LDPC coding has a stronger error correction capability by adopting soft decision decoding with log-likelihood ratio (LLR) information. As a result, the bit error rates (BER) can be reduced and data reliability is significantly enhanced. In the process of the evaluation, we first count the variation of RBER with phase modulated under different single-to-noise ratio (SNR). Then, after using LDPC coding, we compare the sharpness of the modulated two-dimensional data pages to validate the effectiveness of utilizing LDPC coding. Moreover, we study the internal relationship between phase reconstruction with iterative Fourier transform algorithms and LDPC coding. The decoding iteration times and the number of Fourier iterations are counted. Simulation results show that LDPC coding can improve data reliability by decreasing BER.