Istituto di Scienza e Tecnologie dell'Informazione     
Amato G., Chessa S., Vairo C. Optimizing network-side queries with timestamp-join in wireless sensor networks. Technical report, 2009.
This paper proposes a new method for optimizing innetwork distributed queries that perform join of data produced simultaneously by different sensors in a wireless sensor network. We adopt a modified version of the standard join operator that relates tuples having the same timestamp, and an optimized version of it, which provides on-demand, pull-mode, data acquisition from sensors. The optimizer uses an algebraic approach based on transformation rules and ordering of operators to generate and chose a query plan that reduces the query execution cost in terms of consumed energy. We implemented these join operations in a query processor for mica-class sensors and we performed extensive tests to prove that our approach may reduce energy required to process a long running query, by order of magnitudes,with respect to non optimized query plans.
Subject Wireless sensor network
Query optimization
C.2 Computer-Communication Networks

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