Critical Event-Triggered Flows Tolerance in Time-Sensitive Networks

Time-Sensitive Networks (TSN) provide a universal real-time system solution, which guarantees end-to-end transmission with bounded low latency for time-triggered flows by the existing mechanisms. While there are also event-triggered flows i.e. burst or sporadic traffic in some systems such as Advanced Driver Assistance Systems (ADAS), aircraft, and industrial automation, which limits the wider application of TSN. The existing centralized algorithms based on Time-aware Shaper (TAS) cannot deal with the mixture of time-triggered and event-triggered flows effectively because of the unpredictability of events, nor can asynchronous scheduling because of heavy traffic loads. In this paper, we present Mixed Flow Scheduling (MFS), an extended shaping mechanism to tolerate event-triggered flows in the periodic scheduling, which improves the link utilization by reusing the reserved bandwidth, meanwhile the performance of time-triggered flows is not negatively affected. In MFS, a virtual period is designed for event-triggered flows to calculate the reserved bandwidth by the scheduler and the reversed bandwidth is reused according to the multiplexing strategy. To evaluate the performance of MFS, we experimented with it on various numbers of time- and event-triggered flows and compared it with two schemes based on TAS. The results prove the effectiveness of MFS. With MFS, the schedulability of event-triggered flows is improved by 25%, the transmission delay is decreased by 45% and the bandwidth utilization is improved by more than 13% compared to the two other TAS schemes.