Ultra-reliable low latency communications (URLLC) arose to serve industrial
IoT (IIoT) use cases within the 5G. Currently, it has inherent limitations to
support future services. Based on state-of-the-art research and practical
deployment experience, in this article, we introduce and advocate for three
variants: broadband, scalable and extreme URLLC. We discuss use cases and key
performance indicators and identify technology enablers for the new service
modes. We bring practical considerations from the IIoT testbed and provide an
outlook toward some new research directions.Comment: Submitted to IEEE Wireless Commun. Ma