Signal processing and coding for two-dimensional optical storage

Abstract

This paper introduces the concept of TwoDimensional Optical Storage (TwoDOS). In this concept, bits are written in a broad spiral consisting of a number of bitrows stacked together in a hexagonal packing. Bits with a value '1' are represented physically as circular pit-holes on the disc, while bits with a value '0' are characterized by the absence of such a pit-hole. A scalar diffraction model is used to calculate the signal levels for various diameters of the pits. A stripe-wise Viterbi detector is proposed to perform 2D bit-detection with a limited state complexity of the trellis. Simulation results are shown for various diameters of the pits. A 2D modulation code is applied to eliminate patterns that yield a high probability of erroneous detection.

Joint equalization and decoding for nonlinear two-dimensional intersymbol interference channels

“…As the curves show, the improvement in performance is quite significant. The performance of the full graph algorithm after 5 iterations is about 8 dB better (at a bit error rate of ¡ ² ³ ) than the performance reported in [9], where a stripewise Viterbi detector is used for the same ISI.…”

“…Looking at the table, the nonlinearity of the ISI is quite apparent; the signal level does not change linearly as the number of nonzero neighbors increases and the range when the central bit is a 0 is greater than when the central bit is 1. Similar to Immink et al, [9] the signal levels in Table I take into account the interference from the outer shells (beyond the nearest neighbors) by taking an average across all the bit-patterns in these shells.…”

“…These schemes, with the exception of that proposed by Immink et al, [9], use two-dimensional partial response equalization to obtain a linear channel model for the ISI. Then, equalization methods like minimum meansquared-error equalization, are used for detection on this linear channel model.…”

“…TwoDOS is, potentially, the next generation optical storage technology with projected storage capacity twice that of the blu-ray disk and with ten times faster data access rates [8], [9]. As in conventional optical disk recording, bits in the TwoDOS model are written on the disk in spiral tracks.…”

Cancellation of Linear Intersymbol Interference for Two-Dimensional Storage Systems

“…The differences between the 1-D and 2-D case together with the main conclusions are highlighted here. The probability of symbol error is (2) where is the set of all possible 2-D error events in which the null event (no errors) is excluded, is the number of symbol errors in the error event and is the probability that error event occurs. Also (3) where is the probability that the VD selects the path corresponding the error event instead of the path corresponding to the actual data sequence, i.e., .…”