On Priority Assignment for Controller Area Network when some Message Identifiers are Fixed

Robert Ian Davis, Alan Burns, Victor Pollex, Frank Slomka

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Controller Area Network (CAN) is widely used in automotive
applications. With CAN, the network utilisation that may be
obtained while ensuring that all messages meet their deadlines is
strongly dependent on the policy used for priority (message
identifier) assignment. This paper addresses the problem of
priority assignment when some message identifiers are fixed.
There are two variants of this problem: P1 where the gaps
between fixed identifiers are large enough to accommodate the
freely assignable messages and P2 when the gaps are too small.
For problem P1, we provide algorithms that give optimal and
robust priority orderings based on an adaptation of existing
techniques. Problem P2 is more difficult to solve. We show via a
counter example that the algorithms derived for P1 and others
recently published can fail to find a schedulable priority ordering
when the gaps are small, even though one exists. We derive an
optimal and robust solution to this problem with respect to a
simple form of schedulability analysis which assumes the same
upper bound on the length of all messages.
Original languageEnglish
Title of host publicationRTNS '15
Subtitle of host publicationProceedings of the 23rd International Conference on Real Time and Networks Systems
Place of PublicationNew York
ISBN (Print)978-1-4503-3591-1
Publication statusPublished - Nov 2015
Event23rd International conference on Real-Time Networks and Systems (RTNS 2015) - , United Kingdom
Duration: 4 Nov 20156 Nov 2015


Conference23rd International conference on Real-Time Networks and Systems (RTNS 2015)
Country/TerritoryUnited Kingdom


  • priority assignment
  • real time systems
  • scheduling

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