Scheduling Periodic Task Graphs for Safety-Critical Time-Triggered Avionic Systems

Time-triggered communication protocols, such as time-triggered protocol (TTP) and FlexRay, have the potential to solve many system integration and concurrent engineering issues in the aerospace industry. This paper investigates the scheduling of periodic applications on time-triggered systems. A novel scheduling problem is formulated to capture a unique feature commonly existing in the safety-critical time-triggered systems, i.e., in task graphs running in such systems, some nodes (i.e., tasks and messages) are strictly periodic while others are not. To address the problem, a novel scheduling algorithm called synchronized highest level first (SHLF) algorithm is presented. Moreover, to further improve schedulability, this paper also proposes two rescheduling and backtracking approaches, namely release time deferment (RTD) procedure and backtracking and priority promotion (BPP) procedure. Performance evaluation results are presented to demonstrate the effectiveness and competitiveness of our approaches when compared with existing algorithms.