On Throughput and Reliability Enhancement via Relay-assisted Retransmission.

Current 5G user equipment (UE) relay technique, i.e., 3GPP NR sidelink relay, is designed for network coverage extension, and thus only cell-edge UEs can get throughput gain via relay UEs. To exploit relay gain for cell-center UEs, we propose the relay assisted retransmission scheme, which exploits the receiving capability of a relay UE to forward downlink (DL) transport block (TB) of a remote UE via sidelink when retransmission of this TB is needed. By offloading DL retransmission traffic to sidelink, the proposed scheme enables the base station (gNB) to schedule more DL resource for new transmissions, leading to not only enhanced robustness but also clear throughput gain for cell center UEs.