Evaluation of admissible CAN bus load with weak synchronization mechanism

Scheduling frames with offsets has been shown in the literature to be very beneficial for reducing response times in real-time networks because it allows the workload to be better spread over time and thus to reduce peaks of load. In the specific case of CAN, the response time is mainly related to the priority assignment, but offsets can still improve the achievable bus load. When it exists a global clock, a good offsets assignment leads to a TDMA medium access. When each node have its own local clock the use of offsets still spreads the workload over time. However, on CAN, global clock is hardly implemented in practice since using a global clock often requires dedicated hardware and complicates the sharing of the bus with non-synchronized nodes. That is why, we previously introduce the notion of bounded phases, a tradeoff between global and local clocks. Bounded phases allows an affordable synchronization with standard CAN controllers and reduces delays with regard to local clocks. Through an experiment on 5,000 configurations, we have shown that the maximal bus load that can be reached is 80%in the case of bounded phases