Keynote Lectures

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.

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.

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.