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Schedulability analysis for CAN bus messages of periodically-varying size
Ref: CISTER-TR-220501       Publication Date: 27 to 29, Apr, 2022

Abstract:
Abstract—Conventional CAN bus schedulability analysis assumes that all messages with a given identifier have the same worst-case length. In this paper we extend that analysis to a more general model in which messages with a given identifier may have different lengths, that vary according to a known periodic pattern. That is, for some positive integer S, we assume that the length of message instances n and n + S with the same id is the same. By leveraging such patterns, where present, our new analysis allows for a more efficient use of CAN bus bandwidth than the application of conventional analysis, which can be pessimistic. This may be interesting when a given node sends the values of multiple signals with different periods. In such a scenario, the conventional CAN schedulability analysis would require either the use of different ids for different signals (assuming there are enough of them), which leads to a higher bandwidth overhead because of the reduplication of message headers, or using only one id, but pessimistically always assuming the maximum possible length of the message, for safety reasons.

Ishfaq Hussain

,

Konstantinos Bletsas

,

Muhammad Ali Awan

,

Eduardo Tovar

,

Pedro Souto

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