Timing Services in 5G Advanced and 6G Networks

5G-Advanced and 6G networks will serve as critical infrastructure for society and will enable a new generation of immersive use-cases, such as the metaverse, wherever people roam. Absolute time is an essential component to ensure critical use-cases, media playout synchronization, and to timestamp events to be used in machine learned contexts. Until now, timing on the go has mainly been acquired by satellite, ex. GNSS, but a terrestrial timing solution using cellular networks is required to extend coverage to deep indoors and to offer resiliency. In this paper, we detail the use-cases for timing to be provisioned by 5G-Advanced and 6G networks, we discuss the architectural enablers for timing as a service, and we discuss the gaps and research challenges to be solved in 6G for future-proof timing solutions.