The fifth generation (5G) mobile technology is currently being deployed worldwide. In Finland, 5G is already accessible to most of the urban population. While each new generation of mobile technology typically brings about a ten-fold increase in data speeds, 5G offers much more.
One notable feature of 5G is its role as an enabler for the Internet of Things (IoT)—a network of millions or even billions of small sensors connected to the internet. Although 5G provides the necessary bandwidth for such a massive network, a crucial question arises: How can we power this multitude of sensors?
The traditional approach of using single-use batteries for sensing devices is no longer sustainable, mainly due to the environmental impact of these batteries as toxic e-waste after their operational life. There is a pressing need to find a more environmentally friendly solution—a replenishable energy source for IoT sensors. Far-field radio frequency (RF) radiation emerges as a potential solution to this challenge.
"Radio frequency signals are already used almost exclusively to transfer information wirelessly between communication terminals. These very signals can be redesigned to efficiently carry wireless power along with information to the receiver. Traditionally, RF signals were deemed inappropriate for wireless power transfer due to the undeniably large over-the-air propagation loss. However, the radical decline in the energy requirements of simple sensing and computing devices over the last few decades has reignited interest in RF wireless power as a feasible solution for powering IoT sensors," says Nachiket Ayir.
In his doctoral dissertation Nachiket Ayir seeks to address several questions related to RF wireless power: Is transferring power wirelessly through RF signals feasible when employing simple digital communication equipment? Can the waveforms currently used for wireless information transfer be also used for wireless power transfer? What factors limit the feasibility of this technology? How can system-level power efficiency be optimized during wireless transmission?
Nachiket Ayir adopts an experiment-driven approach to assess the feasibility of RF wireless power transfer (WPT). He developed software-defined radio-based test beds to evaluate the performance of different waveforms, including popular communication waveforms, for RF WPT in terms of system-level power efficiency. The test beds provide insights into various parameters that impact power efficiency in RF WPT. The experiments also lead to the development of a novel mathematical model that predicts harvested power for any given waveform.
"The mathematical model for an RF energy-harvesting receiver is a significant contribution of this dissertation. It is unique because it is not restricted by the receiver circuit configuration, the incident waveform, the incident RF power, or other such parameters. I believe this model will be extensively used for further research in this field," says Nachiket Ayir.
The mathematical model is leveraged to design waveforms that maximize harvested power at the receiver. Overall, this dissertation is a blend of experiment-driven and theoretical research, as emphasized by Nachiket Ayir.
Nachiket Ayir hails from Mumbai, India. He started his doctoral studies at Tampere University in the summer of 2018 after completing his MSc from the International Institute of Information Technology (IIIT), Hyderabad, India. He is currently working as a Communication Systems Engineer at E-Space.
Public defence on Friday 1 December
The doctoral dissertation of MSc Nachiket Ayir in the field of Electronics and Communication Engineering titled RF Wireless Power and Data Transfer: Experiment-driven Analysis and Waveform Design will be publicly examined at the Faculty of Information Technology and Communication Sciences of Tampere University in room TB109 in the Tietotalo building (address: Korkeakoulunkatu 1, Tampere) at 12:00 on Friday 1 December 2023.
The Opponent will be Professor Ioannis Krikidis from the University of Cyprus, Nicosia, Cyprus. The Custos will be Associate Professor Taneli Riihonen from Tampere University, Tampere, Finland.
Photograph: Aditi Site