Abstract

In holographic data storage (HDS) systems, two-dimensional (2D) inter-symbol interference (ISI) according to the degree of blur, thermal noise at detector, and a misalignment depending on pixel mismatch severely causes a poor performance [3]. To improve a bit error rate (BER) performance, more powerful modulation codes and error correction codes (ECC) have been studied [4], [5]. In general, the conventional modulation code doesn’t have any error correcting capabilities. The ECC adds parity bits to provide error correction and therefore the ECC reduces the data rate. Trellis coded modulation (TCM) provides coding gains without data rate loss in digital communications, if the distances between symbols i.e., M phase-shift keying (M-PSK) and M quadrature amplitude-shift keying (M-QASK) can be defined [6]. Although [1] defined the distance between symbols of 2/4 modulation code for the soft-decision Viterbi decoding, it is not a general method. In this paper, we introduce a new distance metric between symbols for 2/4 modulation code and propose an error correcting capable 2/4 modulation code using the TCM in the HDS without data rate loss.

© 2011 Optical Society of America