Data Recovery for Multilayer Magnetic Recording

Multilayer magnetic recording (MLMR) is a next-generation technology that has the potential to enhance the longevity of magnetic recording technology by storing data on multiple layers that are stacked on top of one another. The challenges associated with the development of MLMR fall into two main categories: the challenges of writing to multiple layers and the challenges of reading back from multiple layers. As there is already a fair amount of existing work addressing the former, in this article we target the latter by building and testing detection schemes that are able to separate the signals from multiple layers that are mixed together during the readback. In this initial work, we consider a two-layer system. The resolution of the bottom layer is worse than that of the top due to the increased separation of the bottom layer from the reader. We assume a geometry of two single-width tracks on the top-layer straddling a double-width track on the bottom layer and with intersymbol interference (ISI) response on the bottom layer having half the amplitude and double the length of that on the top-layer. We examine the performance of two candidate detection algorithms, a Viterbi-based algorithm operating on a trellis, and a least-squared (LS) algorithm that attempts to invert the effect of the channel’s interference. We evaluate the error rate performance of these detection schemes using a common channel model that sums the ISI and intertrack interference (ITI) components from each of the layers. The main result from this work is that 14.5% density gains over the conventional perpendicular magnetic recording (PMR) and 7.6% gains over two-dimensional magnetic recording (TDMR) could be possible for the novel MLMR system.