Complex Event Processing in Wireless Sensor Networks

Most of the WSN applications need the number of sensor nodes deployed to be in order of hundreds, thousands or more to monitor certain phenomena and capture measurements over a long period of time. The large volume of sensor networks would generate continuous streams of raw events in case of centralized architecture, in which the sensor data captured by all the sensor nodes is sent to a central entity. In this paper, we describe the design and implementation of a system that carries out complex event detection queries inside wireless sensor nodes. These queries filter and remove undesirable events. They can detect complex events and meaningful information by combining raw events with logical and temporal relationship, and output this information to external monitoring application for further analysis. This system reduces the amount of data that needs to be sent to the central entity by avoiding transmitting the raw data outside the network. Therefore, it can dramatically reduce the communication burden between nodes and improve the lifetime of sensor networks. We have implemented our approach for the TinyOS Operating System, for the TelosB and Mica2 platforms. We conducted a performance evaluation of our method comparing it with a naive method. Results clearly confirm the effectiveness of our approach.