Safety Critical Computer Systems: Failure Independence and Software Diversity Effects on Reliability of Dual Channel Structures

Abstract

Abstract The paper examines Safety Critical real-time Systems (SCS), in particular their dual-channel structures. The analytical study on computer-based SCS recognizing failures comparing the results of both channels is based on the theory of reliability. The aim is to establish reliable models that include independence rate between failures of both channels and their diversity. The created formulas are used to calculate the function of reliability, probability of safety failures and hazard failures. The intensity of failures of the system and the intensity of its recovery, the ratio between Common Mode Failures (CMF) and failures of individual channels are explicitly presented in the models. for the independence of hardware and software Faults are introduced. The analytical models obtained allow evaluating the effects of independence of channels and the depth of their diversity. A formula for calculating the improvement of safety thanks to the dual-channel architecture in comparison to a single-channel structure of the same output reliability parameters has been worked out. Analytical models can be used to calculate indicators of systems in order to establish their compliance with safety standards. Analytical models can be used to calculate indicators of specific systems to determine their compliance with safety standards. The results make possible to find out technical solutions with better reliability and safety features.