Self-Decodability of HARQ Retransmissions for 5G NR LDPC Codes

Hybrid automatic retransmission request (HARQ) in modern wireless communication systems such as 4G and SG is designed to allowing efficient combining of multiple (re)transmissions so as to to achieve coding gain. The coding performance for each retransmission in isolation may, however, not be consistent, potentially lacking self-decodability of individual retransmissions. This can require the UE to receive multiple additional retransmissions when the initial transmission is missed, undermining the intended efficiency of the HARQ system. In this paper, we discuss the self-decodability of HARQ retransmissions and show it can be improved, providing a balance between coding gain and self-decodability, by modifying the rate-matching operation without changing the channel code construction. We present results illustrating the gains in self-decodability using the proposed scheme.