Industry is approaching the limit of the data storage density possible on magnetic disks with the traditional approach of reading and writing data on a single-track. This research considers an alternate approach called two dimensional magnetic recording (TDMR), wherein bits are read and written in two dimensions on conventional magnetic disks. A key problem in TDMR is that a given magnetic grain on the disk retains the polarization of the last bit written on it; hence, if a grain is large enough to contain two bit centers, the oldest bit will be overwritten by the newer one if they have different polarities. Bits are read from the disk by a 2D read head. Because bits are stored at high density, the signal read from a given bit suffers 2D intersymbol interference (2D ISI) from bits in both down and cross track directions. This research allows industry to continue to refine conventional magnetic recording technology, without radical redesign of the recording medium.
The investigators study 2D signal processing and coding techniques to combat grain overwriting and 2D ISI in TDMR, with the goal of approaching the recently estimated channel capacity of 0.5 bit/grain. Specific objectives include: 1) Investigate detectors for the TDMR magnetic grain channel based on three channel models: rectangular-grain model, discrete-grain Voronoi model, and Voronoi model. 2) Integrate grain channel detection with 2D ISI detection and with channel decoding. 3) Develop capacity bounds for the TDMR/ISI channel models. 4) Evaluate the developed algorithms against the capacity bounds and against experimental data from the project s industrial partner Hitachi Global Storage Technologies, a Western Digital company.
