Continuous Median Queries in Wireless Sensor Networks

A Wireless Sensor Network (WSN) consists of a set of small and autonomous sensing nodes, which possess limited energy and computational capabilities, and are typically used to monitor events. In many applications, one is interested in continuous and robust statistical summaries of the observed values, and in this paper we focus on reporting the median of the observed values gathered by the WSN. Keeping in mind that the nodes' energy consumption is paramount in a WSN, we propose a distributed and energy-efficient approach based on the use of multiple, suitably designed, histogram queries which efficiently explore existing cached results minimizing the number of bytes transmitted. Our experimental results, using synthetic and real datasets, show that our proposed solution is indeed able to substantially extend the lifespan of the WSN when compared to the current state-of-the-art.