Fully autonomous wireless sensor network for freight wagon monitoring

This paper presents a wireless sensor network (WSN) for onboard monitoring of railway freight wagons, in which all the network nodes are energetically autonomous. Unlike the usual energy-harvesting WSNs, here it is proposed to supply not only the sensor nodes but also the sink node by means of an energy harvester, in order to realize independent networks for each wagon. This choice allows the overcoming of several issues related to a single network for the whole train, but it requires a significant reduction of the energy consumption of the power-hungry sink node. In order to reduce the energy consumption to values sustainable by energy harvesters without penalizing the quality of service, this paper proposes a bi-periodic communication scheme for the local wireless transmission, a dynamic management of the GPS receiver, and a consumption model of the GPRS transceiver, which allows an optimized management of the sleep modes. The proposed solutions are compared with the existing ones, and the theoretical predictions are validated by measurements on a system prototype under different operating conditions