Period-Aware Segmented Synthesis of Schedules for Multi-hop Time-Triggered Networks

Time-triggered offline scheduling is a cost-efficient way to guarantee low communication end-to-end latency and minimal jitter for communication networks in real-time systems. The schedule is generated pre-runtime and indicates the transmission times of time-triggered frames such that contention is prevented. The synthesis of such offline schedules is a bin-packing problem, known to be NP-complete, with complexity driven by the constraints on frame transmissions, and the number of frames in the schedule. Satisfiability Modulo Theories combined with segmented approaches have been successfully used for synthesizing schedules of large networks. However, such synthesis did not take into account frames periods that are much shorter than the time to execute the schedule cycle. This paper presents a period-aware segmented approach that takes into account the frame periods in order to allocate various instances of a frame within a single cycle. We describe three different synthesis strategies and evaluate them with different synthetic experiments. The results show better performance for one of the strategies, which can synthesize schedules of large networks with high communication loads in less than one hour. We also report how the synthesis time and the schedule quality can change with different parameter configurations.