Traversal time for weakly synchronized CAN bus

Scheduling frames with offsets has been shown in the literature to be very beneficial for reducing response times in realtime networks because it allows the workload to be better spread over time and thus to reduce peaks of load. Maintaining a global synchronization amongst the stations induces substantial overhead and complexity in networks not providing a global time service such as CAN. Indeed, on CAN, no global clock is implemented in practice and each station possesses its own local clock. Without a global clock, the de-synchronization between the streams of frames created by offsets remains local to each station. The first contribution of this work is to show that important gains with respect to the communication latencies, around 40% in our experiments, can be achieved if we implement bounded clock desynchronization, also refered to as bounded phases, between the stations. The second contribution of this work is to provide a set of network-calculus based timing analyses to handle systems with bounded phases and compare their performances.