Cost-Based Quantile Query Processing in Wireless Sensor Networks

In this paper we investigate how to efficiently and effectively use histogram queries for processing quantile queries in wireless sensor networks. A major concern when processing queries within such an environment is to minimize the energy consumption by the network nodes, thus extending the networks lifetime, e.g., the time when the first node runs out of energy. Towards that goal, we define a cost model for a refinement-based algorithm that performs a series of refining histogram queries in order to determine the exact quantile value. Given that the histogram size, i.e., its number of bins, is an important factor in the query processing cost, we use the defined cost model to estimate the histogram size that minimizes the maximum energy cost per-node when processing the quantile query. This is equivalent to maximizing the time until the first node dies and therefore to extending the network´s lifetime. In our experiments, using synthetic and real datasets, we evaluate the performance of the proposed solutions in a variety of different settings.