Guaranteeing Proper-Temporal-Embedding Safety Rules in Wireless CPS: A Hybrid Formal Modeling Approach

Cyber-Physical Systems (CPS) integrate discrete-time computing and continuous-time physical-world entities, which are often wirelessly interlinked. The use of wireless safety critical CPS (control, healthcare etc.) requires safety guarantees despite communication faults. This paper focuses on one important set of such safety rules: Proper-Temporal-Embedding (PTE). Our solution introduces hybrid automata to formally describe and analyze CPS design patterns. We propose a novel lease based design pattern, along with closed-form configuration constraints, to guarantee PTE safety rules under arbitrary wireless communication faults. We propose a formal methodology to transform the design pattern hybrid automata into specific wireless CPS designs. This methodology can effectively isolate physical world parameters from affecting the PTE safety of the resultant specific designs. We conduct a case study on laser tracheotomy wireless CPS to show that the resulting system is safe and can withstand communication disruptions.