Outlier detection strategies for WSNs: A survey

Abstract Wireless Sensor Networks (WSNs) are developed significantly from the last decades and attracted the attention of scientific and industrial domains. In WSNs, sensor nodes distributed autonomously in harsh environments are easily vulnerable to faults and attacks that cause sensor readings unreliable and inaccurate. In this scenario, sensor readings that have differed considerably from healthy behaviors will be considered abnormal data or anomalies/outliers. The inclusion of such outliers in data analytics will inevitably affect the outcome of the decision-making process. Thus, detecting outliers in WSNs using data-driven approaches becomes a novel technique among the Machine Learning (ML) communities. Meanwhile, various research issues are there in measuring the performance of the deployed ML algorithms in detecting outliers in WSNs, which generally contains minimum resources in terms of computational capability and power sources to ensure data quality. Hence, this paper presents a comprehensive overview of the state-of-the-art Statistical and Artificial Intelligence (AI) based techniques used in WSNs to detect outliers in the view of architecture, type, degree, approach, and detection mode. Furthermore, each aforementioned outlier detection approach is presented with detailed discussions and future scope for developments.