Energy and quality aware query processing in wireless sensor database systems

Query processing has been studied extensively in traditional database systems. However, few existing methods can be directly applied to wireless sensor database systems (WSDSs) due to their characteristics, such as decentralized nature, limited computational power, imperfect information recorded, and energy scarcity in individual sensor nodes. This paper proposes a quality-guaranteed and energy-efficient (QGEE) algorithm. QGEE utilizes in-network query processing method to task WSDSs through declarative queries, and confidence interval strategy to determine the accuracy of query answers. In QGEE, the correlation between a query and a node is calculated by vector space model (VSM), and a query correlation indicator (QCI) is designed to quantify the priority of becoming active for individual nodes. Given a query, the QGEE algorithm will adaptively form an optimal query plan in terms of energy efficiency and quality awareness. This approach can reduce disturbance from measurements with extreme error and minimize energy consumption, while providing satisfying service for various applications. Simulation results demonstrate that QGEE can reduce resource usage by about 50% and frame loss rate by about 20%. Moreover, the confidence of query answers is always higher than, or equal to, the users’ pre-specified precision.