Mixed-scheduling belief propagation for LDPC decoders in the magnetic recording systems

Serial belief propagation is known to improve the decoding performance of the low-density parity-check (LDPC) codes through the modified sequence of check node or variable node update. The sequence updates or scheduling can be performed in two directions: a left-to-right (LR) direction or the right-to-left (RL) one. In this work, we show that even when both update directions yield comparable bit error rate (BER) performances, the error locations may differ. Therefore, we propose a mixed-scheduling belief propagation (MBP) which combines the reliability information obtained from the LR and RL directions. Simulation results show that the MBP outperforms the current serial schedulings by providing faster convergence as well as lower bit error rates in the bit patterned media system which is a candidate for future magnetic recording systems.