MCCQF: Low-Latency Transmission Based on IEEE 802.1 Qch For Hierarchical Networking

5G and Industrial Internet are bringing a variety of applications with on-time and reliable demands. Cyclic queuing and forwarding (CQF), a well-known mechanism defined by IEEE 802.1 Qch in Time Sensitive Network (TSN), achieves deterministic end-to-end latency and jitter without complex gating calculations. However, most of the current work ignores the prevalence of hybrid networks with different link rates, resulting in low bandwidth utilization and high latency for single-cycle CQF. In this paper, we propose a multi-cycle CQF to address the transmission in multi-link-rate networking, reducing deterministic end-to-end latency and improving link bandwidth utilization. In addition, we formulate the scheduling constraints, being of guiding significance for designing the transmission of multi-link-rate networks, and we design an online scheduling algorithm based on it. We compare the proposed scheme with the single-cycle CQF online scheduling algorithm in hierarchical multi-link-rate networking scenarios, and the evaluation shows that our algorithm achieves better end-to-end ultra-low latency (38.9% reduction) with a smaller schedulability gap compared with single-cycle CQF.