Analysis and Modeling of a Priority Inversion Scheme for Starvation Free Controller Area Networks

Cheng-Min LIN

IEICE TRANSACTIONS on Information and Systems   Vol.E93-D    No.6    pp.1504-1511
Publication Date: 2010/06/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.E93.D.1504
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Software System
Distributed control,  priority queueing,  priority inversion,  controller area network,  embedded control,  

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Control Area Network (CAN) development began in 1983 and continues today. The forecast for annual world production in 2008 is approximately 65-67 million vehicles with 10-15 CAN nodes per vehicle on average . Although the CAN network is successful in automobile and industry control because the network provides low cost, high reliability, and priority messages, a starvation problem exists in the network because the network is designed to use a fixed priority mechanism. This paper presents a priority inversion scheme, belonging to a dynamic priority mechanism to prevent the starvation problem. The proposed scheme uses one bit to separate all messages into two categories with/without inverted priority. An analysis model is also constructed in this paper. From the model, a message with inverted priority has a higher priority to be processed than messages without inverted priority so its mean waiting time is shorter than the others. Two cases with and without inversion are implemented in our experiments using a probabilistic model checking tool based on an automatic formal verification technique. Numerical results demonstrate that low-priority messages with priority inversion have better expression in the probability in a full queue state than others without inversion. However, our scheme is very simple and efficient and can be easily implemented at the chip level.