On the performance of turbo product codes and LDPC codes over partial-response channels

We investigate the performance of low density parity check (LDPC) codes, single-parity turbo product codes (TPC/SPC) and multi-parity turbo product codes (TPC/MPC) over various partial response channels (PR) encountered in magnetic and magneto-optical (MO) recording systems, like PR4/EPR4 and PR1/PR2 channels. The codes have similarity in structures and can be decoded using simple message-passing algorithms. We show that the combination of a TPC/SPC code and a precoded PR channel results in good distance spectrum due to interleaving gain. Density evolution is then used to compute the thresholds for TPC/SPC and LDPC codes over PR channels. Through analysis and through simulations, we show the three types of codes yield comparable bit error rate performance with similar complexity, but they exhibit quite different error statistics, which in turn may result in sharp differences in block failure rate after the Reed-Solomon error correction code (RS-ECC).