Lossy Forwarding HARQ for Parallel Relay Networks

This paper proposes Lossy-Forwarding Hybrid Automatic Repeat reQuest (LF-HARQ) schemes to improve bit-error-rate (BER), packet-error-rate (PER) and throughput performances of dual-hop wireless parallel relaying systems. In contrast to the conventional lossless decode-and-forward schemes, where erroneous packets are always discarded at the relay, we introduce Lossy-Forwarding concept to HARQ technique that allows the relay nodes to forward them to the next hop, referred to as Fully LF-HARQ (FLF-HARQ) scheme. We then propose Partially LF-HARQ (PLF-HARQ) scheme, where the relaying nodes select either forwarding the erroneous packets or requesting retransmission. The mode selection is based on the confidence indicator (CI) expressing the reliability of the received packets. Since the channels are assumed to suffer from block Rayleigh fading, the CI is calculated via online measurement of mutual information, block-by-block. Results of computer simulations to verify the superiority of the proposed techniques are presented