Traffic shaping to reduce jitter in controller area network (CAN)

When a message is transferred from one CAN bus to another via a gateway, variability in the response time of the message on the source network typically translates into queuing jitter on the destination network. This jitter inheritance accumulates across each gateway and can significantly impact the schedulability of lower priority messages. In this paper, we show that the real-time performance of the network can be enhanced by a simple method of traffic shaping that eliminates this inherited queuing jitter. This method does not require access to global time, nor does it require precise time-stamping of when messages are received at the gateway or blocking read calls. It can also be extended to account for clock drifts between networks.

[1]  Thomas Nolte,et al.  Minimizing CAN response-time jitter by message manipulation , 2002, Proceedings. Eighth IEEE Real-Time and Embedded Technology and Applications Symposium.

[2]  J. Loeser,et al.  Low-latency hard real-time communication over switched Ethernet , 2004 .

[3]  Thomas Nolte,et al.  Multi-level hierarchical scheduling in Ethernet switches , 2011, 2011 Proceedings of the Ninth ACM International Conference on Embedded Software (EMSOFT).

[4]  Michael González Harbour,et al.  Schedulability analysis for tasks with static and dynamic offsets , 1998, Proceedings 19th IEEE Real-Time Systems Symposium (Cat. No.98CB36279).

[5]  A. Burns,et al.  Implementing Transactions in a Distributed Real-Time System without Global Time , 2009 .

[6]  Kang G. Shin,et al.  Achieving real-time communication over Ethernet with adaptive traffic smoothing , 2000, Proceedings Sixth IEEE Real-Time Technology and Applications Symposium. RTAS 2000.

[7]  Lothar Thiele,et al.  Performance analysis of greedy shapers in real-time systems , 2006, Proceedings of the Design Automation & Test in Europe Conference.

[8]  Paulo Pedreiras,et al.  Minimizing the End-to-End Latency in Multi-Segment Time-Triggered Networks , 2004 .

[9]  J. Turner,et al.  New directions in communications (or which way to the information age?) , 1986, IEEE Communications Magazine.

[10]  Alan Burns,et al.  Controller Area Network (CAN) schedulability analysis: Refuted, revisited and revised , 2007, Real-Time Systems.

[11]  Mathieu Grenier,et al.  Pushing the limits of CAN - scheduling frames with offsets provides a major performance boost , 2008 .

[12]  Nicolas Navet,et al.  NETCARBENCH: A BENCHMARK FOR TECHNIQUES AND TOOLS USED IN THE DESIGN OF AUTOMOTIVE COMMUNICATION SYSTEMS , 2007 .

[13]  Alan Burns,et al.  Response Time Upper Bounds for Fixed Priority Real-Time Systems , 2008, 2008 Real-Time Systems Symposium.

[14]  John A. Clark,et al.  Holistic schedulability analysis for distributed hard real-time systems , 1994, Microprocess. Microprogramming.

[15]  Alberto L. Sangiovanni-Vincentelli,et al.  Optimizing End-to-End Latencies by Adaptation of the Activation Events in Distributed Automotive Systems , 2007, 13th IEEE Real Time and Embedded Technology and Applications Symposium (RTAS'07).

[16]  Luís Almeida,et al.  Message routing in multi-segment FTT networks: the isochronous approach , 2004, 18th International Parallel and Distributed Processing Symposium, 2004. Proceedings..

[17]  Thomas Nolte,et al.  Using bit-stuffing distributions in CAN analysis , 2001 .