Effective processing of continuous group-by aggregate queries in sensor networks

Aggregate queries are one of the most important queries in sensor networks. Especially, group-by aggregate queries can be used in various sensor network applications such as tracking, monitoring, and event detection. However, most research has focused on aggregate queries without a group-by clause.In this paper, we propose a framework, called the G-Framework, to effectively process continuous group-by aggregate queries in the environment where sensors are grouped by the geographical location. In the G-Framework, we can perform energy effective data aggregate processing and dissemination using two-dimensional Haar wavelets. Also, to process continuous group-by aggregate queries with a HAVING clause, we divide data collection into two phases. We send only non-filtered data in the first collection phase, and send data requested by the leader node in the second collection phase. Experimental results show that the G-Framework can process continuous group-by aggregate queries effectively in terms of energy consumption.