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SMT-based task- and networklevel static schedule generation for time-triggered networked systems
- in Proc. RTNS. ACM
, 2014
"... In Ethernet-based time-triggered networks, like TTEther-net, a global communication scheme, for which the schedule synthesis is known to be an NP-complete problem, estab-lishes contention-free windows for the exchange of messages with guaranteed low latency and minimal jitter. However, in order to a ..."
Abstract
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In Ethernet-based time-triggered networks, like TTEther-net, a global communication scheme, for which the schedule synthesis is known to be an NP-complete problem, estab-lishes contention-free windows for the exchange of messages with guaranteed low latency and minimal jitter. However, in order to achieve end-to-end determinism at the application level, software tasks running on the end-system nodes need to obey a similar execution scheme with tight dependencies towards the network domain. In this paper we address the simultaneous co-synthesis of network as well as application schedules for preemptive time-triggered tasks communicat-ing in a switched multi-speed time-triggered network. We use Satisfiability Modulo Theories (SMT) to formulate the scheduling constraints and solve the resulting problem using a state-of-the-art SMT solver. Furthermore, we introduce a novel incremental scheduling approach, based on the de-mand bound test for asynchronous constrained-deadline pe-riodic tasks, which significantly improves scalability for the average case without sacrificing schedulability. We demon-strate the performance of our approach using synthetic net-work topologies and system configurations. 1.
Priority-driven Swapping-based Scheduling of Aperiodic Real-Time Messages over EtherCAT Networks
"... Abstract-Real-Time Ethernet (RTE) technologies are becoming increasingly popular, as they provide high bandwidth and are able to meet the requirements of industrial real-time communications. Among RTE protocols, the EtherCAT standard is suitable for motion control and closed-loop control applicatio ..."
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Abstract-Real-Time Ethernet (RTE) technologies are becoming increasingly popular, as they provide high bandwidth and are able to meet the requirements of industrial real-time communications. Among RTE protocols, the EtherCAT standard is suitable for motion control and closed-loop control applications, which require very short cycle times. As EtherCAT was specifically devised for periodic traffic, aperiodic real-time transmissions are far from being efficient, as they entail long cycle times. To overcome this limitation, this paper presents a general framework for priority-driven swapping-based scheduling of aperiodic realtime messages over EtherCAT networks, which uniformly covers both dynamic and static priority and allows for very short cycle times. The paper provides a description of the prioritydriven swapping framework, a schedulability analysis for both static priority and dynamic priority scheduling, and simulative assessments, obtained through OMNeT++ simulations.
