Bi-Directional Signal Detection and Decoding for Hybrid ARQ Using Superposition Coding

This paper proposes a bi-directional signal detection and decoding method for our previously proposed hybrid automatic repeat request (HARQ) scheme using superposition coding (SPC-HARQ). The SPC-HARQ scheme multiplexes the initial and retransmission packets within the same frequency band using superposition coding to improve the transmission efficiency at retransmission. Since the superposition coding in the SPC-HARQ can be viewed as packet-level convolutional coding, the receiver can detect and decode the series of received packets in the reverse order of the time slots in addition to the forward order, that is, bi-directional detection and decoding. Simulation results show that the proposed bi-directional signal detection and decoding in the SPC-HARQ improves the throughput performance compared to when using the conventional HARQ and SPC-HARQ with forward decoding only.