A large-scale wireless sensor networks (WSNs) can be deployed for top-k querying applications. There are many top-k querying algorithms which are based on traditional routing approaches. In this article, we proposed a clustering-based routing for top-k querying (CRTQ) in WSNs to save the energy consumption and extend the network lifetime. The proposed scheme consists of two parts: one is the cluster formation algorithm; another part is the inter-cluster choosing the relay cluster head algorithm. Moreover, we adopt a corresponding dynamic clustering algorithm. Our experimental result shows that CRTQ substantially outperforms the existing tree-based approaches and clustering-based approaches in terms of both energy consumption and network lifetime.

Wireless Sensor Networks (WSNs) can be viewed as energy constrained database systems, and join query processing is a very important topic in the field of sensor based systems. Join query for WSNs in a multi-dimensional and continuous way has not been widely explored, as well as is not energy efficient enough. In this paper, we proposed a continuous Multi-attribute Join Query Processing (MJQP) within latest sampling periods for WSNs based applications. We developed a filter-based scheme to discard non-joining tuples, which the center points of filters are identified and updated. Besides, we design an optimized solution to reduce the transmission of non-joining tuples, which is very benefit on energy efficiency. Experiments on real-world data set show that our methods outperform the centralized algorithm.

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