Modeling and Analysis of Scheduling for Distributed Real-time Embedded Systems

Aimed at the deficiencies of resources based time Petri nets （RBTPN） in doing scheduling analysis for distributed real-time embedded systems, the assemblage condition of complex scheduling sequences is presented to easily compute scheduling length and simplify scheduling analysis. Based on this, a new hierarchical RBTPN model is proposed. The model introduces the definition of transition border set, and represents it as an abstract transition. The abstract transition possesses all resources of the set, and has the highest priority of each resource; the cxecution time of abstract transition is the longest time of all possible scheduling sequences. According to the characteristics and assemblage condition of RBTPN, the refinement conditions of transition border set are given, and the conditions ensure the correction of scheduling analysis. As a result, it is easy for us to understand the scheduling model and perform scheduling analysis.

Efficient schedulability analysis for mixed-criticality systems under deadline-based scheduling

Safety-critical avionics systems which become more complex and tend to integrate multiple functionalities with different levels of criticality for better cost and power efficiency are subject to certifications at various levels of rigorousness. In order to simultaneously guarantee temporal constraints at all different levels of assurance mandated by different criticalities, novel scheduling techniques are in need. In this paper, a mixed-criticality sporadic task model with multiple virtual deadlines is built and a certification-cognizant dynamic scheduling approach referred as earliest virtual-deadline first with mixed-criticality（EVDF-MC） is considered, which exploits different relative deadlines of tasks in different criticality modes. As for the corresponding schedulability analysis problem, a sufficient and efficient schedulability test is proposed on the basis of demand-bound functions derived in the mixed-criticality scenario. In addition, a modified simulated annealing（MSA）-based heuristic approach is established for virtual deadlines assignment. Experiments performing simulations with randomly generated tasks indicate that the proposed approach is computationally efficient and competes well against the existing approaches.

Schedulability Analysis Method of Timing Constraint Petri Nets

Timing constraint Petri nets (TCPNs) can be used to model a real-time system specification and to verify the timing behavior of the system. This paper describes the limitations of the reachability analysis method in analyzing complex systems for existing TCPNs. Based on further research on the schedulability analysis method with various topology structures, a more general state reachability analysis method is proposed. To meet various requirements of timely response for actual systems, this paper puts forward a heuristic method for selecting decision-spans of transitions and develops a heuristic algorithm for schedulability analysis of TCPNs. Examples are given showing the practicality of the method in the schedulability analysis for real-time systems with various structures.

Design of Energy-efficient Hierarchical Scheduling for Integrated Modular Avionics Systems

Recently the integrated modular avionics （IMA） architecture which introduces the concept of resource partitions becomes popular as an alternative to the traditional federated architecture. This study investigates the problem of designing hierarchical scheduling for IMA systems. The proposed scheduler model enables strong temporal partitioning, so that multiple hard real-time applications can be easily integrated into an uniprocessor platform. This paper derives the mathematic relationships among parti- tion cycle, partition capacity and schedulability under the real-time condition, and then proposes an algorithm for optimizing partition parameters. Real-time tasks with arbitrary deadlines are considered for generality. To further improve the basic algo- rithm and reduce the energy consumption for embedded systems in aircraft, a power optimization approach is also proposed by exploiting the slack time. Experimental results show that the designed system can guarantee the hard real-time requirement and reduce the power consumption by at least 14%.