Abstract
In many critical real-world scenarios (e.g., emergency response, environmental protection, infrastructure surveillance), based on the Internet of Things (IoT) technology, multiple UAV swarms work together to acquire, transmit, and process information, subsequently taking action to provide the intended service. Collaborations and interactions among UAVs create interdependencies that can facilitate the propagation of failures, potentially leading to high-impact cascading effects. Leveraging the hierarchical architecture of IoT, this work examines the cascading failure mechanism triggered by the relay malfunction and its impact on mission reliability of a heterogeneous multi-phase UAV swarm system. To analyze mission reliability under cascading effects, a separable and analytical modeling method is put forward, which decomposes the original problem into independent, reduced reliability problems for efficient analysis. A detailed case study on a two-phase rescue mission showcases the model's ability to capture failure propagation and assess its impact. The suggested approach offers an efficient means of quantifying cascading effects, enabling mission planners to identify vulnerabilities and improve overall resilience strategies. Furthermore, based on the proposed mission reliability analysis method, resource allocation problems are formulated and solved to balance cost and mission reliability in practical mission design.