System-Level Analysis of D2D Relaying for Ultra-Reliable and Low-Latency Wireless Control

This paper studies a industrial wireless control system where a motion controller has a continuous closed-loop control link to a group of actuator devices on a factory floor. The goal is to achieve service requirements of ultra-reliable and low-latency communications (URLLC) for such motion control system. We present our latest findings on group-based device-to-device (D2D) relaying for achieving spectrally efficient URLLC technology. Namely, we propose to group together the devices in close proximity and exploit intra-group D2D relaying to enforce reliable access. Next, we demonstrate the benefits of identifying the users with weak channel in each group and scheduling those users with on-demand relaying. We found that devices in momentary poor channel conditions are also the weakest link in the system-level reliability. Therefore, on-demand relaying for those devices can significantly improve reliability while maintaining a better utilization efficiency of network resources. The presented analysis leads to the conclusion that a future wireless control system for SG and beyond shall include support for on-demand D2D relaying to achieve the best performance.