EXIT-chart-based threshold calculation of LDPC code in 2D ISI channels

An algorithm based on the fitting of modified Extrinsic Information Transfer (EXIT) chart is proposed to calculate the thresholds of low-density parity-check (LDPC) codes optimized for the two-dimensional (2D) intersymbol interference (ISI) channels encountered in high-density magnetic recording, such as bit-patterned magnetic recording (BPMR) and two-dimensional magnetic recording (TDMR). The modified EXIT chart algorithm determines the LDPC threshold by fitting the EXIT curve of the variable node decoder (VND) combined with 2D detector (2D-DET) to the EXIT curve of the check node decoder (CND). Both the optimal Bahl-Cocke-Jelinek-Raviv (BCJR) 2D-DET and reduced-complexity Gaussian-approximated iterative row-column 2D-DET are considered.