Scheduling of Time-Triggered Traffic for Deterministic URLLC in Industrial Automation

Ultrareliable low-latency communication (URLLC) has been envisioned as the paradigm shift for wireless industrial automation in the coming industry 4.0. Despite the flexibility in conjunction with stringent requirements of latency and reliability, URLLC cannot guarantee the determinism demanded by industrial automation to provide an in-order and low-jitter delivery. Motivated by the evolvements in Rel-17 that strengthen the intrinsic determinism of 5G system, this article studies deterministic URLLC to achieve low-latency and bandwidth-saving scheduling of time-triggered traffic in Industrial Internet of Things (IIoT), instead of using time-sensitive networking (TSN) or hybrid TSN-URLLC. However, due to the queueing congestion and wireless links changes, it is challenging to achieve deterministic scheduling with bounded end-to-end (E2E) latency and low-loss probability. To ensure the determinism and schedulability of URLLC, offset s in gate control lists (GCLs) and radio resources are assigned under constraints of zero congestion, sequential arrival, bounded latency, and ultra reliability. To further improve the latency reduction and bandwidth saving of deterministic URLLC, we find the feasible transmission delays subject to the contradiction on monotonicity of the E2E latency and bandwidth with respect to the transmission delay, then propose a scheduling method to obtain the best solution of three cases by optimizing transmission delay, offset, bandwidth, and the number of subchannel. Simulation results validate the analysis and show the performance gain of the proposed method in three cases.