Iterative soft decoded partial response channels for hybrid magneto-optical recording

Abstract

In this paper, a physical model of readback signals from a hybrid magneto-optical (MO) recording using magnetic flux detection is presented. The minimum mean-square error (MMSE) technique has been used to design generalized partial response (GPR) targets in order to facilitate the application of the trellis based channel detector. A PR target with integer coefficients is proposed as a good approximation to the GPR target. We also address the application of turbo codes and LDPC codes with iterative soft decoding structure to the hybrid magneto-optical (MO) recording channel. The effects of bloom, transition noise and giant magneto-resistive (GMR) sensor nonlinearity on the bit error rate (BER) performance are investigated both for uncoded partial response maximum likelihood (PRML) and iterative soft decoded recording channels. Our results for the hybrid recording channels indicate that turbo/LDPC codes of rate 16/17 can achieve coding gains of about 5 dB over PRML methods for a 10 5 target BER at the normalized density = 1 5. Turbo codes with iterative soft decoding are seen to be robust to transition noise.Index Terms-Bloom, generalized partial response (GPR) target, hybrid magneto-optical recording, iterative soft decoding, low density parity check (LDPC) codes, minimum mean-square error (MMSE), transition noise, turbo codes.