Hard Real-Time Communication in Bus-Based Networks

  • Authors:
  • Sathish Gopalakrishnan;Lui Sha;Marco Caccamo

  • Affiliations:
  • University of Illinois at Urbana-Champaign;University of Illinois at Urbana-Champaign;University of Illinois at Urbana-Champaign

  • Venue:
  • RTSS '04 Proceedings of the 25th IEEE International Real-Time Systems Symposium
  • Year:
  • 2004

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Abstract

Route selection is an important aspect of the design of real-time systems in which messages might have to travel over multiple hops to reach their destination and multiple paths exist between a source and a destination. The length of route affects the ability to meet deadlines and greedy routing might leave certain messages with no feasible route. We consider bus-based networks on which periodic message transmissions need to be scheduled and present a technique for synthesizing routes such that all messages meet their deadlines. Our offline technique enables system designers to configure routes in a large-scale embedded system. In our solution, we allow message fragmentation and utilize multiple paths to satisfy the requirements of each message. The routing problem is NP-complete and our approximation algorithm is based on a linear programming formulation. In our methodology, we deal with both earliest deadline first and rate monotonic scheduling at each bus in the system. Apart from point-to-point messages, we discuss scheduling multicast messages to facilitate thepublisher/subscriber model. Finally, we also mention some heuristics for online routing which might be of value in soft real-time systems.