Low-density parity-check code for holographic data storage system with balanced modulation code

Abstract

In this report, we discuss low-density parity-check (LDPC) code for a holographic digital data storage (HDDS) system. In conventional LDPC decoding, the exact log likelihood ratio (LLR) value improves the error performance of the proposed LDPC code. A channel of an HDDS system has a nonlinear and complex characteristic. Therefore, it is difficult to obtain an exact probability model for an HDDS channel. In this study, an effective bit likelihood mapping method is developed and evaluated for LDPC decoding with a 6 : 8 balanced modulation code as a recording code. The LLR value, which represents the reliability of the 6 : 8 decision, is determined by considering demodulation error cases. An additional step is applied to a conventional LDPC decoding using feedback information in an iterative decoding in order to improve decoding performance. Feedback information can be helpful in accelerating the convergence of LDPC iterative decoding and in improving the error performance at the same number of decoding iterations. A simulation shows that the proposed algorithm scheme is effective and reliable.