Proactive Resource Scheduling for 5G and Beyond Ultra-Reliable Low Latency Communications

Effective resource use in Ultra-Reliable and Low-Latency Communications (URLLC) is one of the main challenges for 5G and beyond systems. In this paper, we propose a novel scheduling methodology (combining reactive and proactive resource allocation strategies) specifically devised for URLLC services. Our ultimate objective is to characterize the level of proactivity required to cope with various scenarios. Specifically, we propose to operate at the scheduling level, addressing the trade-off between reliability, latency and resource efficiency. We offer an evaluation of the proposed methodology in the case of the well-known Hybrid Automatic Repeat reQuest (HARQ) protocol in which the proactive strategy allows a number of parallel retransmissions instead of the "send-wait-react" mode. To this end, we propose some deviations from the HARQ procedure and benchmark the performance in terms of latency, reliability outage and resource efficiency as a function of the level of proactivity. Afterwards, we highlight the critical importance of proactive adaptation in dynamic scenarios (i.e. with changing traffic rates and channel conditions).