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 multiobjective  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.