Managing temporal allocation in Integrated Modular Avionics

Abstract

Recent civil airborne platforms are produced using Integrated Modular Avionics (IMA). IMA promotes both sharing of execution and communication resources by the avionics applications. Designs following IMA decrease the weight of avionics equipment and improve the whole system scalability. However, the price to pay for these benefits is an increase of the system's complexity, triggering a challenging system integration process. Central to this integration step are the timing requirements of avionics applications: the system integrator has to find a mapping of applications and communications on the available target architecture (processing modules, networks, etc.) such as end-to-end delay constraints are met. These challenges stress the need for a tool capable of evaluating different integration choices in the early design stages of IMA. In this paper, we present and formalize the problem of spatial and temporal integration of an IMA system. Then, we focus on the temporal allocation problem which is critical to ensure a proper timely behavior of the system. Two main properties are presented to ensure perfect data transmission for hard real-time flows. To quantify the quality of a set of valid temporal allocations, CPM utilization and communication robustness performance criteria are defined. We show on an example that both criteria are antagonist and that they can be leveraged to choose an allocation that either improves the system computing performance or the robustness of the network.