Cache-Based Periodic Query Optimization for Wireless Sensor Networks

Contiguous queries in wireless sensor networks may have some regions overlapping, and sensory data retrieved by recent queries may be used for answering the queries forthcoming, when these data are fresh enough. To support this query answering strategy, we propose a popularity-based caching mechanism for optimizing the periodic query processing. Specifically, the network region is divided using a cell-based manner, where each grid cell is abstracted as an elementary unit for the caching purpose. Fresh sensory data are cached in the memory of the sink node. The popularity of grid cells are calculated leveraging the queries conducted in recent time slots, which reflects the possibility that grid cells may be covered by the queries forthcoming. Prefetching may be performed for grid cells with a higher degree of popularity when their sensory data re missed in the cache. These cached sensory data are used for facilitating the query answering afterwards.