Dependability modeling and evaluation of IPS architectures in the railway sector

Rail transport is increasingly preferred for its safety and reliability, which can be achieved through a variety of advanced design solutions and technological supports. Among them, ensuring a continuous power supply is crucial for the reliable execution of energy-dependent critical operations. Inspired by the Italian railway infrastructure, here the focus is on \gls{ips}systems that support critical functionalities, such as the signaling system that regulates railway traffic movement. Fault-tolerant \gls{ips} designs are implemented to address unforeseen fault events at the \gls{ips} level, which could lead to safety or availability issues. Building on previous work, this paper presents a refined stochastic model-based evaluation framework to aid in comparing various \gls{ips} redundant architectures with respect to dependability characteristics, mainly focusing on reliability and availability metrics. Major extensions pertain to i) the modeling of two additional \gls{ips} architectures; ii) the integration of models to analyze the \gls{ips} behavior under normal and critical conditions; iii) the consideration and modeling of battery failures; iv) extension of the analysis campaign to account for the new additions. A designer can effectively utilize the findings from this analysis to determine the most appropriate \gls{ips} organization that meets dependability criteria while also considering potential energy consumption savings.