DACS: A dynamic approximative caching scheme for Wireless Sensor Networks

Saving energy in Wireless Sensor Networks is essential to extend the lifetime of in-field deployments. Previous research has shown that communication is generally the most energy consuming task and needs to be reduced in order to build resource-efficient long-term applications. The communication demand for retrieving query results from deep within the sensor network is typically high. As a result, frequent non-continuous data acquisition consumes a lot of energy and shortens the lifetime of the sensor network significantly. In this work we discuss optimizations for processing high amounts of unique queries by using a dynamic adaptive caching scheme: DACS. In DACS query results can be retrieved from caches that are placed nearer to the query source instead of sending queries deep into the network. The communication demand can be significantly reduced and the entire network lifetime is extended. To verify cache coherence in sensor networks with non-reliable communication channels, an approximative update policy is used. To localize the adequate cache adaptively, model-driven queries including a degree of demanded result quality can be defined. The entire logic is thereby processed by DACS and hidden to the user. The significant energy conservation is proven in evaluations that include real sensor node deployments.