Fleck - A platform for real-world outdoor sensor networks

This paper presents the design of the Fleck platform for building real-world outdoor sensor networks. Fleck1 and Fleck2 have been successfully deployed in several long-term outdoor sensor networks. The Fleck3 is the latest member of the platform. The power input stage of the Fleck3 has been simplified and now provides the ability to compute both the energy coming in and the energy being consumed. This makes possible the implementation of sophisticated distributed energy-aware applications. Both rechargeable batteries (with over-charge protection) and super-capacitors can be used as the primary source of power. The Fleck3 incorporates a real-time clock. At the expense of a small current drain, the real-time clock provides several advantages. It allows the Fleck3 to be placed into very deep sleep, reducing the overall energy consumption down to 30 micro-Amps. It also allows the network as a whole to maintain a better sense of time and reduces the time-keeping overhead on the micro-controller. The Fleck3 incorporates a packet-based radio from Nordic. This radio is more energy efficient than earlier generations and significantly reduces the communications overhead on the micro-controller. It also provides a better radio front-end, with a range of about 1 km with normal, zero-gain quarter-wavelength antennas in the 915 MHz band. The Fleck platform supports a large variety of sensor interface boards, including a companion board incorporating a TPM chip from Atmel for applications where security is important. These features make the Fleck platform a very strong candidate for outdoor sensor networks.