Abstract

Holographic data storage (HDS) records binary bits in a two-dimensional page. Two-dimensional (2D) inter-symbol interference (ISI) according to the blur effect, thermal noise at detector, and a misalignment depending on pixel mismatch severely causes a poor performance. Therefore, various powerful modulation codes, error-correction codes (ECCs), and detectors have been proposed [4]. Specially, the soft-decision Viterbi decoding scheme consisting of modulation and Viterbi decoders has been studied for 2/4 modulation code in HDS systems [1], [2]. While the decoding method in [1], [2] showed outstanding bit error rate (BER) performance, its data rate is too low. In this paper, a new decoding method is proposed. The proposed method uses 4/6 modulation code [3], 3/4 convolutional code and the soft-decision Viterbi decoding scheme. Also, we propose a new reliability metric for 4/6 modulation code in order for the soft-decision Viterbi decoding scheme to use the branch metric on the trellis. Finally, we find a symbol mapping method for the modulation code, which provides a large free distance on the trellis for the enhanced error correcting capability.

© 2011 Optical Society of America