Optimization of Acyclic Bandwidth Allocation Exploiting the Priority Mechanism in the Fieldbus Data Link Layer

In process control applications, the bandwidth destined to acyclic traffic is oversized in order to ensure that the often-pressing time constraints of control traffic are met. In the FieldBus, a protocol designed to support the exchange of information between sensors / actuators and regulating elements in an automation environment, this means allocating an excessive portion of the macrocycle to acyclic traffic. The use of traffic management based on priority can allow more efficient management of the available bandwidth. In this paper, the authors analyze the priority mechanism provided for in the FieldBus DLL, assessing various strategies for management of aperiodic traffic and different application scenarios.