Measurement and Simulation Based Techniques for Real-Time Systems Analysis

Rigorous methods for design and implementation of safety critical real-time systems are vital to avoid loss of human lives and/or severe economic losses. Unfortunately, many of these systems are designed and evaluated using ad-hoc techniques. There are, on the other hand, relatively well developed theories for modeling and analysis of timing and reliability. These theories are, however, seldom applied in industry for system development, mainly because of the simplifying model assumptions and lack of appropriate tool support. <BR>This thesis presents two new methods aimed to narrow the gap between research results and industrial practice in evaluation and design of real-time systems. <BR>The first contribution is a technique that can be used to derive worst-case execution time estimates for real-time software by measurments on the target system. Such estimates are essential when verifying if a system fulfills its timing requirements. The second contribution is a simulation based technique that can be used to evaluate timing aspects of distributed real-time systems, as well as calculating reliability estimates of these systems. Such estimates are essential in determining if a system meets its requirements sufficiently well. Compared to existing analytical methods for execution time analysis and schedulability analysis, which analyze models of the hardware, the starting point for both these methods are real target systems, rather than an abstract model with limited correspondance to reality. <BR>The presented initial case-studies give clear evidence that the proposed methods have potential of being both applicable and useful.