I. Introduction
To keep up with the rapidly growing demand for data storage, a recording density must be increased to an ultra-high level for future storage systems. Bit-patterned media recording (BPMR) is one of the promising candidates for the next generation of hard disk drive (HDD) technology, which is expected to achieve the areal density up to 4 terabits per square inch (Tb/in2) [1]. Because of high recording densities, BPMR has very small gap between data bit islands in both the along-track and the across-track directions, thus causing two-dimensional (2D) interference consisting of inter-symbol interference (ISI) and inter-track interference (ITI) [2]–[4], which degrades the overall system performance significantly.