An (m,k)-firm Elevation Policy for Weakly Hard Real-Time in Converged 5G-TSN Networks

Abstract

Ongoing standardization efforts in 5G and Time-Sensitive Networking (TSN) aim to provide safety-critical applications with real-time communication. However, 5G-TSN network schedules often rely on idealistic delay models that can jeopardize the validity of their guarantees. This paper presents an $(m,k)$-firm Elevation Policy to uphold a base level of weakly hard real-time guarantees (WHRT). It augments the primary schedule with a dynamic priority-driven scheme to elevate the priority of $m$ out of $k$ consecutive frames if they experience unexpected delays. Our evaluations demonstrate the necessity of WHRT to increase fault-tolerance against 5G delay outliers and to uphold the quality of control within a 5G-TSN networked control system. Still, only a small resource overhead is imposed during epochs where the primary schedule is valid and can serve stronger QoS guarantees. The $(m,k)$-firm Elevation Policy thereby yields a robust but light-weight fallback mechanism to serve applications with dependable guarantees during unstable network conditions.