Two-Dimensional Magnetic Recording Using a Rotated Head Array and LDPC Code Decoding

Abstract

This paper examines the improvement in performance of rotated and normally oriented heads by using the quasi-cyclic low-density parity-check (QC-LDPC) code in a two-dimensional magnetic recording (TDMR) system. This paper indicates that the significant improvement in performance in the rotated head compared to the normally oriented head can be attributed to the larger amplitude of its dibit response and the reduced overlap between conditional probability density functions. Simulation also indicates that maximum areal densities of 9.85 T/in 2 and 6.64 T/in 2 can be reached by the rotated head array (RHA) and normally oriented head array (NHA) at optimum bit aspect ratios of 0.67 and 3.5 for 5.5 nm Voronoi grains, respectively. After decoding, the performance of the NHA is about 8.5 dB worse than the RHA. With an oversampled signal, 2-D linear minimum mean-squared error (LMMSE) equalizer and LDPC codes, a user bit density near 10 Tbits/in 2 is feasible for a rotated head array.Index Terms-Two-dimensional magnetic recording (TDMR), magnetoresistive head, quasi-cyclic low-density parity-check (QC-LDPC) code.