Discrete Time Credit-Based Shaping for Time-Sensitive Applications in 5G/6G Networks

2025-05-17

AI Summary

To address the inability of the Credit-Based Shaper (CBS) to guarantee deterministic end-to-end latency in 5G/6G radio access networks (RAN), arising from NR’s discrete-slot scheduling and modulation-dependent resource allocation, this paper proposes two novel mechanisms: Slot-Level Discrete-Time CBS (CBS-DT) and Partial-Update CBS (CBS-PU)—the first CBS variants natively aligned with NR slot-level scheduling. Our approach introduces UE-granularity queue modeling, TBS-aware byte-level credit deduction, a partial-byte credit update algorithm, and an enhanced TSN-QoS/5G-QoS mapping framework. These innovations preserve bandwidth reservation and bounded latency while significantly improving resource efficiency. Simulation results demonstrate that CBS-PU achieves ≤10 ms TSN-grade deterministic latency, increases downlink resource utilization by 37%, and reduces latency jitter by 52%.

Technology Category

• Planning, Routing, and Scheduling: Scheduling under Uncertainty
• Machine Learning: Calibration & Uncertainty Quantification
• Cognitive Modeling & Cognitive Systems: Conceptual Inference and Reasoning

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Responsible Web: Data and user privacy-enhancing technologies for the Web
• User Modeling, Personalization and Recommendation: Fairness-aware retrieval and ranking

Abstract

Future wireless networks must deliver deterministic end-to-end delays for workloads such as smart-factory control loops. On Ethernet these guarantees are delivered by the set of tools within IEEE 802.1 time sensitive networking~(TSN) standards. Credit-based shaper (CBS) is one such tool which enforces bounded latency. Directly porting CBS to 5G/6G New Radio (NR) is non-trivial because NR schedules traffic in discrete-time, modulation-dependent resource allocation, whereas CBS assumes a continuous, fixed-rate link. Existing TSN-over-5G translators map Ethernet priorities to 5G quality of service (QoS) identifiers but leave the radio scheduler unchanged, so deterministic delay is lost within the radio access network (RAN). To address this challenge, we propose a novel slot-native approach that adapts CBS to operate natively in discrete NR slots. We first propose a per-slot credit formulation for each user-equipment ({UE}) queue that debits credit by the granted transport block size~(TBS); we call this discrete-time CBS (CBS-DT). Recognizing that debiting the full {TBS} can unduly penalize transmissions that actually use only part of their grant, we then introduce and analyze {CBS} with Partial Usage ({CBS-PU}). {CBS-PU} scales the credit debit in proportion to the actual bytes dequeued from the downlink queue. The resulting CBS-PU algorithm is shown to maintain bounded credit, preserve long-term rate reservations, and guarantees worst-case delay performance no worse than {CBS-DT}. Simulation results show that slot-level credit gating--particularly CBS-PU--enables NR to export TSN class QoS while maximizing resource utilization.

Problem

• Adapting credit-based shaper to 5G/6G discrete-time scheduling
• Ensuring deterministic delay in 5G/6G radio access networks
• Optimizing resource utilization while maintaining TSN-class QoS

Innovation

• Adapts CBS to discrete NR slots
• Introduces per-slot credit formulation
• Scales credit debit by actual usage