Top-k Monitoring in Wireless Sensor Networks

Abstract—Top-k monitoring is important to many wireless sensor applications. This paper exploits the semantics of top-k query and
proposes an energy-efficient monitoring approach called FILA. The basic idea is to install a filter at each sensor node to suppress
unnecessary sensor updates. Filter setting and query reevaluation upon updates are two fundamental issues to the correctness and
efficiency of the FILA approach. We develop a query reevaluation algorithm that is capable of handling concurrent sensor updates. In
particular, we present optimization techniques to reduce the probing cost. We design a skewed filter setting scheme, which aims to
balance energy consumption and prolong network lifetime. Moreover, two filter update strategies, namely, eager and lazy, are
proposed to favor different application scenarios. We also extend the algorithms to several variants of top-k query, that is, order-
insensitive, approximate, and value monitoring. The performance of the proposed FILA approach is extensively evaluated using real
data traces. The results show that FILA substantially outperforms the existing TAG-based approach and range caching approach in
terms of both network lifetime and energy consumption under various network configurations.

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