Characterizing energy consumption in a visual sensor network testbed

In this work we characterize the energy consumption of a visual sensor network testbed. Each node in the testbed consists of a "single-board computer", namely Crossbow\´s Stargate, equipped with a wireless network card and a Webcam. We assess energy consumption of activities representative of the target application (e.g., perimeter surveillance) using a benchmark that runs (individual and combinations of) "basic" tasks such as processing, flash memory access, image acquisition, and communication over the network. In our characterization, we consider the various hardware states the system switches through as it executes these benchmarks, e.g., different radio modes (sleep, idle, transmission, reception), and Webcam modes (off, on, and acquiring image). We report both steady-state and transient energy consumption behavior obtained by direct measurements of current with a digital multimeter. We validate our measurements against results obtained using the Stargate\´s on-board energy consumption measuring capabilities