Concatenating a Structured LDPC Code and a Constrained Code to Preserve Soft-Decoding, Structure, and Burst Correction

In this paper, we propose a simple method to concatenate a structured low-density parity-check (LDPC) code and a high rate constrained code such that three goals are achieved simultaneously: 1) soft information is available to the LDPC decoder; 2) the structure of the LDPC code is retained after concatenation to facilitate hardware implementation; and 3) the system has the ability to correct long erasure bursts. We consider both a runlength-limited code and a dc-free runlength-limited code. For the RLL case, we use a technique we call parity insertion. For the dc-free case, we apply polarity flipping to a subset of the LDPC code parity bits