Providing Low Latency Guarantees for Slicing-Ready 5G Systems via Two-Level MAC Scheduling

5G comes with the promise of sub-millisecond latency, which is critical for realizing an array of emerging URLLC services, including industrial, entertainment, telemedicine, automotive, and tactile Internet applications. At the same time, slicing-ready 5G networks face the challenge of accommodating other heterogeneous coexisting services with different and potentially conflicting requirements. Providing latency and reliability guarantees to URLLC service slices is thus not trivial. We identify transmission scheduling at the RAN level as a significant contributor to end-to-end latency when considering network slicing. In this direction, we propose a two-level MAC scheduling framework that can effectively handle uplink and downlink transmissions of network slices of different characteristics over a shared RAN, applying different per-slice scheduling policies, and focusing on reducing latency for URLLC services. Our scheme offers the necessary flexibility to dynamically manage radio resources to meet the stringent latency and reliability requirements of URLLC, as demonstrated by our simulation results.