System Support for the In Situ Testing of Wireless Sensor Networks via Programmable Virtual Onboard Sensors

Wireless sensor networks (WSNs) can be extensively tested before they are deployed in the field. However, it is equally important to test a WSN after it has been deployed, to verify that it will work as expected in certain situations of interest, which are hard to reproduce in reality. In this paper, we introduce the mechanism of programmable virtual onboard sensors, for letting sensor nodes produce artificial sensor values as dictated by the user, transparently to the application. Virtual onboard sensors are programmed using a simple script-like language, which is interpreted at runtime on the wireless sensor nodes. The user can deploy sensor scripts in the WSN and activate the virtual sensor mode for selected nodes and sensors at any point in time, without changing the node firmware and without stopping the application that runs on the nodes. We also describe and evaluate an implementation of the virtual onboard sensor mechanism on a commercial WSN platform. Our implementation requires little memory and has negligible runtime overhead, and thus can be adopted even for resource-constrained sensor nodes.