Scheduling soft aperiodic messages on FlexRay in-vehicle networks

The FlexRay communication protocol is expected to be the de-facto technique standard for the next generation high-speed networks on vehicles. A number of recent studies has thus investigated message scheduling techniques for FlexRay systems. However, most existing work focused on either the scheduling of periodic messages on the static segment or the scheduling of hard aperiodic messages on the dynamic segment while soft aperiodic messages have been neglected. Also, isolated scheduling severely limits the overall performance of all messages including periodic, hard aperiodic and soft aperiodic messages in terms of bandwidth utilization and transmission latency. In order to address these aspects, this paper presents an algorithm, referred to as Joint Scheduling Algorithm for FlexRay (JSAF), which jointly schedules soft aperiodic messages together with periodic and hard aperiodic messages in real-time FlexRay systems. The algorithm prioritizes periodic messages and hard aperiodic messages and first schedules them onto the static segment and the dynamic segment, respectively. Soft aperiodic messages are then dynamically scheduled with an online scheduler by utilizing unused time left by periodic messages and hard aperiodic messages. Performance evaluation results are presented to demonstrate the effectiveness and competitiveness of our approaches when compared to existing algorithms.