Novel reliability-based HARQ scheme for irregular LDPC codes

In this paper, we propose a new and practical reliability-based hybrid automatic repeat request (RB-HARQ) scheme for irregular low-density parity-check (LDPC) codes. Irregular LDPC codes have an unequal error protection (UEP) property. Using this property, we find that the middle degree message nodes of irregular LDPC codes are important for HARQ systems. If we pick out the low reliable message nodes of them for retransmission, we will reduce the feedback. Moreover, the system performance of this scheme is as well as that of the original RB-HARQ scheme.