Type II Hybrid-ARQ Schemes of LDPC Codes Based on Information-Nulling Rate-Compatible Algorithm

In this paper, information nulling (IN) type II HARQ protocol with low-density parity-check (LDPC) codes is presented. Incremental redundancy is created from partial null versions of the original information data using the same encoder/decoder structure. In comparison to the conventional rate-compatible type II HARQ schemes, the decoder architecture always operates at the highest code rate, thus efficiently exploiting the decoder hardware. The performance analysis shows that the proportion of un-nulled information-bits influences the performance significantly, and the performance of the IN-HARQ system does not increase monotonically as the proportion increases. An improved IN-HARQ scheme is designed with variable proportion values of different retransmission, and some preliminary results have been derived to make sure the optimum proportion of un-nulled information-bits. Another IN-HARQ scheme is presented by combining interleaving and IN-HARQ protocol, which provides additional performance gain of interleaving to the original IN-HARQ scheme