Keynote Lectures

Sensor Networks based on Optical Waveguide Sensors
Kort Bremer, Leibniz Universität Hannover, Germany, Germany

Power Supply for Wireless Sensor Systems
Leonhard Reindl, University of Freiburg, Germany, Germany

Back to the Future - Transiently-powered Computing in the Internet of Things
Luca Mottola, Politecnico di Milano, Italy and SICS Swedish ICT, Sweden, Sweden

Sensor Networks based on Optical Waveguide Sensors

Kort Bremer
Leibniz Universität Hannover, Germany

Brief Bio
Kort Bremer is a scientific staff member at the Hannover Centre for Optical Technologies (HOT) of the Leibniz Universität Hannover, Germany. He graduated at the Hochschule Wismar, Germany in electrical engineering and received a PhD from the University of Limerick, Ireland. His research interests include optical sensors and optical communication, for instance, fiber optic pressure and temperature sensors, fiber optic gas sensors, reinforcement structures that are functionalized with fiber optic sensors for structural heath monitoring applications, mode-selective fiber couplers for spatial division multiplexing as well as optical biosensors for smartphones.

Abstract
In order to monitor chemical or physical quantities optical waveguide sensor systems can be applied. Usually an optical waveguide sensor system consist of a light source, light detector as well as an optical waveguide and the quantity to be measured modulates the intensity, phase, polarization or wavelength of the light propagating inside the optical waveguide. In terms of sensor networks optical waveguide sensors have the advantages of e.g. a high multiplexing and a remote sensing capability. This presentation will review waveguide based optical sensors and will discuss their utilization with the emphasis on sensor networks.

Power Supply for Wireless Sensor Systems

Leonhard Reindl
University of Freiburg, Germany

Brief Bio
Leonhard Reindl received the Dipl. Phys. degree from the Technical University of Munich, Germany in 1985 and the Dr. sc. techn. degree from the University of Technology Vienna, Austria in 1997. In April he joined the surface acoustics wave group of the Siemens Corporate Technology Division, Munich, Germany. At Siemens he contributed to the development of SAW convolvers, dispersive, tapped and reflective delay lines. His primary interest was in the development and application of SAW ID-tag and wireless passive SAW sensor systems. In winter 1998/99 and in summer 2000 he was guest professor for spread spectrum technologies and sensor techniques at the University of Linz, Austria. In April 1999 Leo Reindl joined the Institute of Electrical Information Technology at the Clausthal University of Technology where he became Professor for communication and microwave techniques. In May 2003 he accepted a full professor position at the Laboratory for Electrical Instrumentation at the Department of Microsystems Engineering (IMTEK), University of Freiburg, Germany. Since October 2014 he has been serving as head of the Department.

His research interests include wireless sensor and identification systems, Surface Acoustic Wave devices and materials as well as microwave communication systems based on SAW devices.

Leonhard Reindl is member of the IEEE and the German VDE, of the Technical Program Committees of IEEE Frequency Control Symposium, IEEE Ultrasonic Symposium, Eurosensors and of the German biannual Symposium "Sensoren und Messsysteme". Since 2014, he has been serving as Editor-in-Chief for the Section 'Sensor Networks' of the open access journal Sensors. From 2009 to 2015 he served as editor for IEEE Transactions UFFC. He was elected member of the AdCom of the IEEE UFFC society from 2005 to 2007 and from 2009 to 2011. He also served for the European Security Research and Innovation Forum ESRIF committee.

Leonard Reindl holds more than 30 patents on SAW devices and wireless passive sensors and has authored or co-authored more than 200 papers in this field.

Abstract
Wireless sensor or actuator systems, like portable phones, remote control, ID cards, or embedded wireless sensor nodes play an ever growing role in our industrialized environment. Those systems and many more were enabled due to the steady decreasing power consumption of high integrated ICs. Most such systems are powered by batteries or inductive coupling. In this presentation several concepts for an alternative power supply of wireless sensor or actuator systems are discussed in detail.
Batteries, although today mostly used, suffer from a limited storage capacity, which induce a labour and sometimes cost-intensive periodic maintenance, and a problematic ecological impact. The operating range of inductive coupling systems is due to the near field limited to the aperture of the coupling coil. UHF systems operate in the far field and reach higher distances. Their operating range is limited by the distance where the voltage at the feeding point of the antenna becomes too low to drive the rectifier circuit.
Larger read out ranges become feasible by omitting the rectifier stage. In this case we need either a passive frequency modulating device to shift the read out signal to a side band, or a resonator with a high quality factor, like a SAW, BAW, or dielectric device, to store the energy until all environmental echoes are feed away.
For many applications, both indoor and outdoor, energy harvesting system become feasible which convert ambient power densities like light, RF fields, special or temporal thermal gradients, or mechanical vibrations into electrical supply power of the wireless system.
All those systems strongly suffer from a lack of energy. Thus new concepts for lowering the power consumption of a wireless sensor or actuator system by keeping their features remain extreme important. Herby, a wake up receiver is presented which operates on a current requirement as low as 3 micro A.
Several application examples of the presented systems will be given, e.g., sensors for industry 4.0, indoor position sensors, inductively transmitted power to implants, and high temperature wireless sensors. A noteworthy observation is thus made: all the aforementioned applications are realized on a common theoretical idea, namely the maximum power transfer theorem and its various representations across the disciplines.

Back to the Future - Transiently-powered Computing in the Internet of Things

Luca Mottola
Politecnico di Milano, Italy and SICS Swedish ICT, Sweden

Brief Bio
Luca Mottola is an Associate Professor at Politecnico di Milano (Italy) and a Senior Researcher at SICS Swedish ICT. He completed his Ph.D. at Politecnico di Milano (Italy) in 2008. His research interests focus on modern networked embedded systems. Out of his research, he obtained the Google Faculty Award, was listed twice amongst Postscapes "Internet of Things Top 100 Thinkers”, and received the ERCIM Cor Baayen Award, the Best Paper Award at ACM MOBISYS 2016, the Best Paper Award at ACM/IEEE IPSN 2011 and 2009, the EWSN/CONET European Best Ph.D. Thesis Award, and the MIT TR Italia Young Innovator Award. Luca was PC co-chair for IEEE DCOSS 2015, ACM EWSN 2017, and ACM SENSYS 2017, the flagship event in the field of networked embedded systems. He is an Associated Editor for ACM Transactions on Sensor Networks.

Abstract
Energy harvesting and wireless energy transfer are laying the foundations for a next-generation battery-less Internet of Things (IoT). These forms of energy provisioning, however, are generally erratic across space and time. The computing pattern then becomes intermittent: periods of computation come to be interleaved with periods of unavailable power, until the environment provides sufficient energy to resume operation. This trait intrinsically challenges established practices at designing, implementing, and testing IoT systems, requiring a conceptual as well as practical leap in both hardware and software. As an example, fundamental computing concepts, such as consistency of data and progression of time, need to be revisited. In this talk, I will elicit the key characteristics of such transiently-powered computing model, discuss the current state of the art in the field, and outline open problems and long-term challenges still to be tackled.