Autonomous Energy-Efficient Wireless Sensor Network Platform for Home/Office Automation

Smart homes/offices based on wireless sensor networks (WSNs) can provide an assisted living and working environment to the users. In these applications, the distributed network nodes are made up of low-power low-cost high-energy-efficient electronic platforms equipped with sensors, microcontroller, radio, and antenna, able to periodically sense, receive, store, pre-process, and transmit ambient data to a remote host station. Conventional nodes are usually supplied by batteries, resulting in a significant limitation to the lifetime and to the maximum number of deployable devices. To meet the demand of the next Internet-of-Things (IoT) applications, requiring a vast plurality of interconnected wireless network nodes, this paper presents the design and implementation of a WSN platform whose nodes are energetically autonomous thanks to an embedded photovoltaic panel associated to a rechargeable battery and a power-efficient design with optimized power-management strategy. The implemented node is able to harvest indoor ambient light starting from 100 lux and, according to the available energy, adaptively sets the sensors acquisition and RF transmission rate. Moreover, it provides long-distance data transmission with air data rate from 1 to 500 kbps. The WSN node device is implemented on an $8.6\times 5.4$ cm
²
flexible PCB, being therefore amenable to conform even to curved surfaces. Comparison with the commercial IoT nodes reveals a significant improvement in the state of the art.