Avionics mission computing systems have traditionally been scheduled statically. Static scheduling provides assurance of schedulability prior to run-time and can be implemented with low runtime overhead. However, static scheduling handles non-periodic processing inefficiently, and treats invocation-to-invocation variations in resource requirements inflexibly. As a consequence, processing resources are underutilized and the resulting systems are hard to adapt to meet worst-case processing requirements. Dynamic scheduling has the potential to offer relief from some of the restrictions imposed by strict static scheduling approaches. Potential benefits of dynamic scheduling include better tolerance for variations in activities, more flexible prioritization, and better CPU utilization in the presence of non-periodic activities. However, the cost of these benefits is expected to be higher run-time scheduling overhead and additional application development complexity. This report reviews the...

In the recent development of avionics systems, Integrated Modular Avionics (IMA) is advocated for next generation architecture that needs integration of mixedcriticality real-time applications. These integrated applications meet their own timing constraints while sharing avionics computer resources. To guarantee timing constraints and dependability of each application, an IMA-based system is equipped with the schemes for spatial and temporal partitioning. We refer the model as SP-RTS (Strongly Partitioned Real-Time System), which deals with processor partitions and communication channels as its basic scheduling entities. This paper presents a partition and channelscheduling algorithm for the SP-RTS. The basic idea of the algorithm is to use a two-level hierarchical schedule that activates partitions (or channels) following a distance-constraints guaranteed cyclic schedule and then dispatches tasks (or messages) according to a fixed priority schedule. To enhance schedulability, we devised heuristic algorithms for deadline decomposition and channel combining. The simulation results show the schedulability analysis of the two-level scheduling algorithm and the beneficial characteristics of the proposed deadline decomposition and channel combining algorithms. 1.

Advances in the computer technology encouraged the avionics industry to replace the federated design of control units with an integrated suite of control modules that share the computing resources. The new approach, which is called integrated modular avionics (IMA), can achieve substantial cost reduction in the development, operation and maintenance of airplanes. A set of guidelines has been developed by the avionics industry to facilitate the development and certification of integrated systems. Among them, a software architecture is recommended to address real-time and fault-tolerance requirements. According to the architecture, applications are classified into partitions supervised by an operating system executive. A general-purpose application/executive (APEX) interface is defined, which identifies the minimum functionality provided to the application software of an IMA system. To support the temporal partitioning between applications, APEX interface requires a deterministic cyclic scheduling of partitions at the O/S level and a fixed priority scheduling among processes within each partition. In this paper, we propose a scheduling scheme for partitions in APEX. The scheme determines the frequency that each partition must be invoked and the assignment of processor capacity on every invocation. Then, a cyclic schedule at the O/S level can be constructed and all processes within each partition can meet their deadline requirements. Keywords: scheduling, embedded avionics systems, real-time O/S, APEX 1

The aerospace industry has been investigating integrated modular systems (IMS) for some years. These systems offer benefits in terms of flexibility, software/hardware abstraction, and incremental upgrades. However, in order to benefit from the technology a safety case must be generated which can be maintained incrementally with system changes, otherwise certification will be prohibitively expensive. This paper presents a baseline safety case for IMS in which evidence can be separated between different stakeholders in the system. The different types of incremental upgrade are then considered and a method is proposed for determining the impact of the upgrade on the baseline safety case and elements of the IMS.

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I sincerely thank my advisor Prof K. Gopinath for his guidance and support to complete this thesis. I also thank my organization, Accord Software and Systems for supporting me with time and resources to complete my thesis. I thank my organizational guide Mr.Purushotham for his whole-hearted support. I would also like to thank my supervisors Mr.Devanathan, Mr.Shashidhar and Mr.Rengasamy for their encouragement and support. I will always remember the sincere help that I received from my colleagues Prashanth Nayak and Yadunandan. I believe this has been possible due to the continued motivation and support Time management is one of the critical modules of safety-critical systems. Applications need strong assurance from the operating system that their hard real-time requirements are met. Partitioned system has recently evolved as a means to provide protection to safety critical applications running on an Avionics computer resource. Each partition has an application running strictly for a specified duration. These applications use the CPU on a cyclic basis. Applications running on a real-time systems request the service of time management in one way or the other. An application may request for a time-out while waiting for a resource, may