Randomization-Based Approaches for Dynamic Priority Scheduling of Aperiodic Messages on a CAN Network

The Controller Area Network is a well-known communication bus widely used both in automotive applications and in other environments, as distributed embedded systems, to support the exchange of control messages. Any contention on a CAN bus is deterministically resolved on the basis of the priority, which is fixed and encoded in the identifier field of the frame. Fixed priorities are not the best solution for event-driven applications, such as many distributed embedded control systems, which feature significant reactive behaviour and produce aperiodic traffic which can have real-time constraints. Depending on the priority some aperiodic objects may experience unusually higher access delays compared with those from other objects. This problem can be overcome by dynamically assigning identifiers to aperiodic messages. This paper proposes the use of randomization to provide dynamic priority assignment in a CAN network. The aim of this work is to investigate how the management of aperiodic traffic in a CAN system can be improved using randomization. Two different strategies for aperiodic traffic scheduling on a CAN network are presented and evaluated by simulation.