An improvement of BER using two-dimensional constrained code for array-reader-based magnetic recording

Abstract

To achieve ultra-high areal densities in future magnetic recording technologies such as bit-patterned magnetic recording (BPMR) systems, each bit-island must be closely moved. However, the reduction of bit island spacing always leads to both inter-symbol interference (ISI) and inter-track interference (ITI), which can degenerate system performance. Previously, a one-dimensional (1D) run-length limited (RLL) code was employed to efficiently avoid the ISI effect, while a two-dimensional (2D) detector is widely utilized to deal with the ITI effect as well. However, its complexity is higher than the traditional 1D detector. Therefore, to avoid the fatal data patterns that lead to severe ITI effect, we first present the application of 1D RLL code to be as the 2D modulation code in the multi-head multi-track BPMR systems. Moreover, we also present the modified 2D Viterbi detector that is designed based on our proposed encoding condition. The numbers of state and branch in the traditional trellis’s structure are properly reduced according to encoding condition, thus it does not only provide a lower complexity but also operate better than the traditional 2D Viterbi detector. Results reveal that our proposed coding scheme and modified 2D Viterbi detector can efficiently protect and cope with the ITI effect.