PRML Detection of Multi-Level DVD Channels With Run-Length-Limited Modulation
Multi-level optical recording using Run-Length-Limited (RLL) modulation is a novel method to significantly increase the information recording density without changing optical or mechanical parameters. In this paper, the experimental results of four-level RLL Modulation on Read-Only Digital Versatile Discs (DVD-ROM) are introduced. Since multi-level readout signals have heavy Inter-Symbol Interferences (ISI), partial-response maximum-likelihood (PRML) detection scheme is proposed for multi-level RLL DVD channels instead of slicer detector used in conventional DVD systems. By analyzing and comparing the simulation performances of different PRML schemes, the authors conclude that PR (1, 2, 2, 2, 1) target is preferred to be applied in four-level RLL modulation DVD channels.