DHRR: a downlink highly reliable retransmission method for industrial URLLC over 5G networks

5G makes industrial Ultra-Reliable Low Latency Communications (URLLC) possible by virtue of orthogonal frequency division multiple access and data link layer retransmission technologies. In this paper, we propose a Downlink Highly Reliable Retransmission method (DHRR) for industrial URLLC over 5G networks. First, we jointly consider the packets and retransmission packets of the downlink data queue, and propose an on-demand retransmission strategy based on the hybrid data scheduling. Second, we devise a dynamic switching strategy based on on-demand/cyclic retransmission reliability analysis. The switching strategy enables 5G networks to select the more reliable retransmission strategy online, according to the data queue and available communication resources. Different from state-of-the-art methods, DHRR for the first time synergizes the above strategies to improve the utilization efficiency of communications resources. Simulation results show that DHRR outperforms existing works in terms of URLLC performance.