A Slack Factors Based Real-Time Query Processing Approach in Wireless Sensor Networks

For mission-critical applications such as emergency monitoring over wireless sensor networks, query deadline must be satisfied. Otherwise, the query results would be useless. Thus, it is better to query the nodes as many as possible within the deadline. On the other hand, the energy consumption should be saved to prolong the life of the network. For this purpose, we propose a slack factor based real-time query processing (SFQ) approach for wireless sensor networks, where a slack factor describes the relationship between the time of query processing and the deadline for a node. Since the data delivery mode between nodes is a key factor for data transmission time and energy consumption, we can choose the optimal data delivery mode by using slack factor so that we can maximize the query coverage as well as minimize the total energy cost. The simulation experimental results show that the SFQ approach is effective to get higher accuracy of query results within deadline with lower energy consumption than other traditional approaches.