Ultra-reliable and low-latency communications (URLLC) is an emerging feature in 5G and beyond wireless systems, which is introduced to support stringent latency and reliability requirements of mission-critical industrial applications. In many potential applications, multiple sensors/actuators collaborate and require isochronous operation with strict and bounded jitter, e.g., \SI{1}{\micro\second}. To this end, network time synchronization becomes crucial for real-time and isochronous communication between a controller and the sensors/actuators. In this paper, we look at different applications in factory automation and smart grids to reveal the requirements of device-level time synchronization and the challenges in extending the high-granularity timing information to the devices. Also, we identify the potential over-the-air synchronization mechanisms in 5G radio interface, and discuss the needed enhancements to meet the jitter constraints of time-sensitive URLLC applications.
@article{arxiv.1807.00078,
title = {Over-the-Air Time Synchronization for URLLC: Requirements, Challenges and Possible Enablers},
author = {Aamir Mahmood and Muhammad Ikram Ashraf and Mikael Gidlund and Johan Torsner},
journal= {arXiv preprint arXiv:1807.00078},
year = {2018}
}