Low Latency HARQ Method Using Early Retransmission Before Channel Decoding Based on Superposition Coding

Abstract

This paper proposes a superposition coding-based early retransmission method for a previously reported low latency hybrid automatic repeat request (HARQ) method using early retransmission before channel decoding. The low latency HARQ method mitigates the increased transmission latency resulting mainly from the delay time required for channel decoding in HARQ by requesting early retransmission before the channel-decoding process is completed. However, early-retransmission decision may include error, which results in unnecessary retransmission and consequently throughput loss. The proposed method mitigates this throughput loss by multiplexing the early-retransmission packet and initial packet for the next transmission attempt within the same channel using superposition coding. The receiver applies an inter-packet interference canceller to cancel the interference between the superposition coded packets. Simulation results show that the proposed method further improves the achievable tradeoff between the transmission latency and throughput.