Turbo decoding of a low-density generator matrix code for a high-density magnetic recording channel

In this paper, we propose a turbo decoding method for a low-density generator matrix code. It is based on the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm and the belief propagation (BP) algorithm. Userbits with high error probability are selected for the BP algorithm by using the soft-output of the BCJR algorithm. Since the amount of calculation in the BP algorithm increases exponentially with the number of the userbits, the amount of calculation is reduced drastically by the selection of the userbits with higher error probability. We showed that the use of the proposed algorithm and 16/17 MTR code on an MEEPR4 channel results in a performance better than that obtained without turbo decoding.