Variable-Rate Ultra-Reliable and Low-Latency Communication for Industrial Automation

Ultra-reliable and low-latency communications (URLLC) is an increasingly important aspect of wireless communications in the 5th generation mobile networks (5G) era, specifically in the context of wireless mission-critical communications for factory automation. This paper proposes a pilot-assisted variable rate URLLC scheme for the downlink (DL) of a factory automation network assuming a time-varying fading channel. The proposed scheme consists of two phases: (1) a training phase where the controller estimates the states of the channels to the different sensors and actuators, and (2) a DL phase where the controller transmits a message to every device at a rate adapted to its instantaneous channel state. Numerical analysis shows that the proposed URLLC scheme achieves an extended range of spectral efficiency as compared to schemes with equal-rate transmission and provides robust ultra-reliability across a wide range of data payload sizes. We also show that the proposed scheme exploits multi-user diversity similar to cooperative relaying schemes proposed in the literature.