A distributed mechanism to improve fairness in CAN networks

The controller area network (CAN) protocol was originally developed to be used in the automotive industry, but it was recently discovered that it is suited for a broader class of applications in various automated factory environments. Even though CAN is able to satisfy most of the real-time requirements found in automated manufacturing environments, it is not able to enforce either a fair subdivision of the network bandwidth among the stations or a satisfactory distribution of the access delays experienced when transmitting messages. This paper presents a simple modification of the basic CAN mechanisms which enforces such a kind of fair behavior. This modified mechanism is fully compatible with the original medium access control protocol layer of CAN, and thus with the electronic components which have already been developed and can be found on the market. What is more, the proposed solution provides a superset of the services of the CAN logical link control, which can coexist with the older CAN applications.