Optimizing Receiving Jitter Reduction in TSN: Disjoint Redundant Routes for CQF Shapers

The IEEE 802.1Qch standard, i.e., Cyclic Queuing and Forwarding (CQF), enhances Time-Sensitive Networking (TSN) by simplifying configurations and increasing flexibility. Moreover, for improving network reliability, TSN supports the transmission of multiple stream copies across disjoint redundant routes via IEEE 802.1CB. However, the use of redundant routes can lead to varying receiving times for one stream, introducing undesirable receiving jitter and adversely affecting Quality-of-Service. To tackle this issue, we introduce a novel scheduling strategy aimed at reducing the maximum receiving jitter in CQF. Our approach includes a multi-objective function designed to simultaneously minimize the average jitter across all streams and reduce slot length. We utilize an Integer Linear Programming (ILP) solver to find optimal injection time slots within CQF constraints. To address the computational intensity of the ILP solution, we also propose a heuristic method that uses an injection time slot selection indicator. This indicator helps efficiently identify lower-utilization slots on each redundant route, thereby easing network congestion and further reducing jitter. In addition, a sophisticated proposed slot reduction procedure is also employed to further reduce the receiving and avoid negatively affecting the schedulability. Experimental results validate the superiority of our approach compared to existing methods.