E2STA: An Energy-Efficient Spatio-Temporal Query Algorithm for Wireless Sensor Networks

After wireless sensor networks are deployed, spatio-temporal query is frequently submitted by users to obtain all the sensor readings of an area of interest in a period of time. Most of existing spatio-temporal query processing algorithms organized all the nodes in the whole network or the nodes in the query area into a single routing tree guided by which the sensor readings of the nodes in the query area are sent back to the sink. This study attempts to answer the following two questions: first, is it feasible to processing spatio-temporal query by multiple routing trees? Second, for the single tree based algorithms and the multiple trees based algorithms, which one outperforms the other? We pointed out that the path along which the query results are sent back to the sink is fairly long when a single routing tree is adopted, which leads to a large amount of energy consumption. Organizing the nodes in the query area into multiple routing trees can avoid this problem. Based on the above findings, we designed a protocol of constructing multiple routing trees for the nodes in the query area, and proposed an energy-efficient spatio-temporal query processing algorithm called E(2)STA. Theoretical and experimental results show that the proposed algorithm based on multiple routing trees outperforms the existing algorithms based on one single routing tree in terms of energy consumption.