A Framework for a Distributed and Adaptive Query Processing Engine for Wireless Sensor Networks

Wireless sensor networks (WSNs) are formed of tiny, highly energy-constrained sensor nodes that are equipped with wireless transceivers and can be used primarily in environmental monitoring applications. The nodes communicate with one another by autonomously creating ad-hoc multihop networks which are subsequently used to gather sensor data. WSNs also process the data within the network itself and only forward the result to the requesting node. This is referred to as in-network data aggregation and results in the substantial reduction of the amount of data that needs to be transmitted by any single node in the network. We present a framework for WSNs which would allow optimised query execution plans to be generated in a distributed manner using only locally available information within the network thus preventing the need to transmit network metadata all the way to a central server. We also describe how this framework can be used to perform cross-layer optimisations and illustrate this by presenting a MAC protocol that adapts its operation according to data gathered by the query processing engine. Query plans also adapt continuously by monitoring varying network conditions to maintain energy-efficient operation thus maximising network lifetime.