Ultralow Power Energy Harvesting Body Area Network Design: A Case Study

Citation: Zheng, C. Y., Kuhn, W. B., & Natarajan, B. (2015). Ultralow Power Energy Harvesting Body Area Network Design: A Case Study. International Journal of Distributed Sensor Networks, 11. doi:10.1155/2015/824705This paper presents an energy harvesting wireless sensor network (EHWSN) architecture designed for use within an astronaut's space suit. The contribution of this work spans both physical (PHY) layer energy harvesting transceiver design and low power medium access control (MAC) solutions. The architecture consists of a star topology with two types of transceiver nodes: a powered gateway radio (GR) node and multiple energy harvesting biosensor radio (BSR) nodes. To demonstrate the feasibility of an EHWSN at the PHY layer, a representative BSR node is implemented. The BSR node is powered by a thermal energy harvesting system (TEHS) which exploits the difference between the temperatures of a space suit's cooling garment and the astronaut's body. It is shown that, through appropriate control of the duty cycle in transmission and receiving modes, it is possible to operate with less than 1 mW generated by the TEHS. This requires ultralow duty cycle which complicates MAC layer design because a BSR node must sleep for more than 99.6% of overall operation time. The challenge for MAC layer design is the inability to predict when the BSR node awakens from sleep mode due to unpredictability of the harvested energy. Therefore, a new feasible MAC layer design, GRI-(gateway radio initialized-) MAC, is proposed and analyzed

Ultra low-power photovoltaic MPPT technique for indoor and outdoor wireless sensor nodes

Photovoltaic (PV) energy harvesting is commonly used to power wireless sensor nodes. To optimise harvesting efficiency, maximum power point tracking (MPPT) techniques are often used. Recently-reported techniques focus solely on outdoor applications, being too power-hungry for use under indoor lighting. Additionally, some techniques have required light sensors (or pilot cells) to control their operating point. This paper describes an ultra low-power MPPT technique which is based on a novel system design and sample-and-hold arrangement, which enables MPPT across the range of light intensities found indoors and outdoors and is capable of cold-starting. The proposed sample-and-hold based technique has been validated through a prototype system. Its performance compares favourably against state-of-the-art systems, and does not require an additional pilot cell or photodiode. This represents an important contribution, in particular for sensors which may be exposed to different types of lighting (such as body-worn or mobile sensors)

Wireless body sensor networks for health-monitoring applications

This is an author-created, un-copyedited version of an article accepted for publication in Physiological Measurement. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0967-3334/29/11/R01