Dependability in Interdependent Digital Ecosystems
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Advances in information and communications technology (ICT) encourages the interconnection of ICT systems with traditional monolithic systems, creating complex systems of systems. A modern variety of such systems is the digital ecosystems, including smart grids, which are introduced to new types of dependencies and failures not previously applicable, particularly the introduction of interdependencies between systems. Because of this, new approaches for dependability analysis are needed to further ensure safe and reliable services. In the first part of this thesis the presumably most relevant interdependencies and failures in smart grids are identified through a study of literature, categorized along the dimensions of type of interdependency and type of failure, and found to be; (1) cascading failures in physical interdependencies, (2) escalating failures in cyber interdependencies, and (3) common cause failures in geographic interdependencies. The second part of this thesis shows dependability modeling approach proposals for the identified relevant combinations of interdependencies and failures. Numerical results from the dependability models reveals that some conceivable smart grid failures have bigger effects than others; (1) cascading failures in power grids and (2) common cause base station (BS) failures due to natural events like storms or human caused events like BS disrupting construction work. In addition, it is shown that malware in smart grids can exist and propagate without detection and should be a legitimate concern of stakeholders.