Abstract
Wireless sensor networks, serving as an important interface between physical environments and computational systems, have been used extensively for supporting domain applications, where multiple-attribute sensory data are queried from the network continuously and periodically. Usually, certain sensory data may not vary significantly within a certain time duration for certain applications. In this setting, sensory data gathered at a certain time slot can be used for answering concurrent queries and may be reused for answering the forthcoming queries when the variation of these data is within a certain threshold. To address this challenge, a popularity-based cooperative caching mechanism is proposed in this article, where the popularity of sensory data is calculated according to the queries issued in recent time slots. This popularity reflects the possibility that sensory data are interested in the forthcoming queries. Generally, sensory data with the highest popularity are cached at the sink node, while sensory data that may not be interested in the forthcoming queries are cached in the head nodes of divided grid cells. Leveraging these cooperatively cached sensory data, queries are answered through composing these two-tier cached data. Experimental evaluation shows that this approach can reduce the network communication cost significantly and increase the network capability.
Highlights
With the rapid development of microelectronic, wireless communication, new and renewable energy technologies, smart sensor nodes become smaller in physical size, stronger in storage and computational capabilities, more powerful in battery capacity and less expensive in price
Leveraging the index tree construction algorithm developed in our previous work [33], we develop a novel index tree for organizing sensor nodes in a balanced manner, which is better at facilitating the query processing when multiple kinds of attributes are interested according to certain requirements of domain applications
This work is interesting and inspires caching packets at the intermediate nodes and determining appropriate routing paths; whereas we explore a cooperative caching mechanism at the sink node and the head nodes of grid cells, according to the popularity of sensory data leveraging the recent query history
Summary
With the rapid development of microelectronic, wireless communication, new and renewable energy technologies, smart sensor nodes become smaller in physical size, stronger in storage and computational capabilities, more powerful in battery capacity and less expensive in price. Caching and refreshing multi-attribute sensory data in the network, while diminishing the cost of answering the forthcoming queries, is an important research problem to be explored further To remedy this issue, a two-tier popularity-based cooperative caching (PCC) mechanism is developed to support the periodic query processing, where multi-attribute sensory data are cached in the sink node and leaf head nodes of an index tree. A two-tier cooperative caching mechanism is proposed, such that sensory data of the most popular are cached at the sink node, and these data can be reused for answering the forthcoming queries This strategy can reduce the energy consumption of answering concurrent queries to a large extent.
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