Nonbinary LDPC Coding System With Symbol-By-Symbol Turbo Equalizer for Shingled Magnetic Recording

Abstract

Two-dimensional magnetic recording (TDMR) by shingled magnetic recording (SMR) is one of the most promising technologies for realizing high areal densities. The read/write (R/W) channel model based on a discrete Voronoi model is relatively easily implemented to evaluate the performance of signal processing for TDMR. The nonbinary low-density parity-check (LDPC) coding and iterative decoding system provides the better performance compared with the conventional binary LDPC coding system. Furthermore, a two-dimensional equalizer (2D-EQ) can mitigate the influence of the intertrack interference (ITI) in TDMR. In this paper, the symbol-by-symbol turbo equalizer which consists of a symbol-by-symbol a posteriori probability (APP) decoder for a generalized partial response class-I (GPR1) channel with a 2D-EQ and a sum-product (SP) decoder for a nonbinary LDPC coder over Galois field of GF(28) is evaluated by computer simulation at an areal recording density of 4.12 Tbit/in2. The result shows that the symbol-by-symbol turbo equalizing system provides an SNR improvement of about 3.7 dB over the bit-by-bit turbo equalizing system.