Efficient fault tolerant scheduling on Controller Area Network (CAN)

Dependable communication is becoming a critical factor due to the pervasive usage of networked embedded systems that increasingly interact with human lives in many real-time applications. Controller Area Network (CAN) has gained wider acceptance as a standard in a large number of industrial applications, mostly due to its efficient bandwidth utilization, ability to provide real-time guarantees, as well as its fault-tolerant capability. However, the native CAN fault-tolerant mechanism assumes that all messages transmitted on the bus are equally critical, which has an adverse impact on the message latencies, results in the inability to meet user defined reliability requirements, and, in some cases, even leads to violation of timing requirements. As the network potentially needs to cater to messages of multiple criticality levels (and hence varied redundancy requirements), scheduling them in an efficient fault-tolerant manner becomes an important research issue. We propose a methodology which enables the provision of appropriate guarantees in CAN scheduling of messages with mixed criticalities. The proposed approach involves definition of fault-tolerant feasibility windows of execution for critical messages, and off-line derivation of optimal message priorities that fulfill the user specified level of fault-tolerance.