You are required to read and agree to the below before accessing a full-text version of an article in the IDE article repository.

The full-text document you are about to access is subject to national and international copyright laws. In most cases (but not necessarily all) the consequence is that personal use is allowed given that the copyright owner is duly acknowledged and respected. All other use (typically) require an explicit permission (often in writing) by the copyright owner.

For the reports in this repository we specifically note that

  • the use of articles under IEEE copyright is governed by the IEEE copyright policy (available at
  • the use of articles under ACM copyright is governed by the ACM copyright policy (available at
  • technical reports and other articles issued by M‰lardalen University is free for personal use. For other use, the explicit consent of the authors is required
  • in other cases, please contact the copyright owner for detailed information

By accepting I agree to acknowledge and respect the rights of the copyright owner of the document I am about to access.

If you are in doubt, feel free to contact

Reducing Pessimism and Increasing Flexibility in the Controller Area Network




Presentation Monday 12th of May 2003.

Publication Type:

Licentiate Thesis


Mälardalen University


The Controller Area Network (CAN) is a widely used real-time communication network for automotive and other embedded applications. As new applications continue to evolve, the complexity of distributed CAN based systems increase. However, CANs maximum speed of 1 Mbps remains fixed, leading to performance bottlenecks. In order to make full use of this scarce bandwidth, methods for increasing the achievable utilisation are needed.Traditionally, real-time scheduling theory has targeted hard real-time systems, which most of the time are safety critical. Since these systems (by definition) are not allowed to have any timing flaws, analysis techniques need to take all possible scenarios of execution combinations and execution times of the system into consideration. This will result in a system that is configured for the worst possible scenario. Whether this scenario is likely, or even possible, in the real system is not considered. Hence, the result may be an unnecessarily expensive system, with potentially overly provisioned resources.In this thesis we address two issues. In the first part, we investigate how to loosen up pessimistic real-time analysis in a controlled way, thereby allowing the designer to make well-founded trade-offs between the level of real-time guarantee and the system cost. Specifically, we investigate and model the bit-stuffing mechanism in CAN in order to retrieve representative distributions of stuff-bits, which we then use in the response time analysis instead of the worst-case values normally used. We evaluate the validity of these stuff-bit distributions in two case studies, and we integrate this representation of message frame length with the classical CAN worst-case response-time analysis.In the second part of the thesis, we propose a novel way of scheduling the CAN. By providing server-based scheduling, bandwidth isolation between users is guaranteed. This increases the flexibility of CAN, by providing efficient handling of sporadic and aperiodic message streams. Server-based scheduling also has the potential to allow higher network utilisation compared to CANs native scheduling. The performance and properties of server-based scheduling of CAN is evaluated using simulation. Also, the server-based scheduling is applied in an end-to-end analysis. Keywords: controller area network, CAN, real-time communication, real-time analysis, reliability trade-off analysis, bit-stuffing, server-based scheduling


author = {Thomas Nolte},
title = {Reducing Pessimism and Increasing Flexibility in the Controller Area Network},
note = {Presentation Monday 12th of May 2003.},
number = {10},
month = {May},
year = {2003},
publisher = {M{\"a}lardalen University},
url = {}