An efficient stopping criterion of LDPC decoding for optical transmission

The stopping criterion based on parity-check constraints is an inherent advantage of low-density parity-check (LDPC) codes. However, the parity-check computation with signs of the posterior information costs additional hardware or decoding delays, which may be a particular problem for the full-parallel LDPC decoding in optical transmission. Furthermore, the performance degradation caused by using simplified stopping criterions should also be considered, where the maximum number of the iterations is usually limited by the very high decoding speed in optical transmission. In this paper, we propose an efficient early stopping criterion with the consideration of the complexity/performance tradeoffs. The new method is based an intelligent combination of check equations and temporary hard decisions, and can be pipelined with check-node updating, thus leading to lower complexity and power consumption, which are desirable for both optical and wireless communications. Simulation results show that the hybrid criterion not only achieves the same performance as the conventional stopping criterions, but also provides a noticeable gain for the other simplified stopping criterions.