Fault Tolerance in Wireless Sensor Networks for Harsh Environments: A Survey of Techniques, Challenges, and Future Directions

Wireless Sensor Networks (WSNs) are deployed in harsh and resource-constrained environments to support applications such as environmental monitoring, disaster-response, and industrial automation. In these settings, sensor nodes are prone to failures caused by extreme conditions, making fault tolerance essential for reliability and longevity. However, despite prior work, a comprehensive survey covering fault tolerance techniques from environment-aware to predictive approaches is still missing to guide the design of robust WSNs. This survey reviews fault tolerance techniques for WSNs operating in these conditions. We classify existing approaches into three categories: environment-aware protocols that proactively adapt to contextual metrics; adaptive algorithms that react to failures through localised self-organisation; and predictive techniques that anticipate faults using machine learning methods. We also identify open challenges, including heterogeneous architectures, and security-aware resilience. By synthesising recent advances and future directions, this survey aims to guide the development of robust WSNs for sustained operation in adverse conditions.