IoT systems and wireless power transfer protocols in ad-hoc communication networks

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Κατσιδήμας, Ιωάννης
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The techniques of energy maintaining and replenishment in wireless communications networks have become particularly popular in recent years. Rapid technological advances in the field of Wireless Power Transmission (Wireless Power Transmission) have a major impact on sensor networks and more generally on energy-restricted communications networks, paving the way for new methods of energy management in wireless systems. Until recently, existing research mainly focused on maximizing network lifetime, improving charging efficiency, minimizing latency during charging, and so on. Most recent research has already begun to examine algorithmic solutions to address the problems that arise. At the same time, both the evolution and the application of ICT systems in very important areas of our lives (industry, smart home, smart cities, etc.) is rapid. IoT devices (devices connected to the internet) must be able to be deployed in any place and access them from everywhere. A large number of these devices perform monitoring and controlling tasks in "smart" applications as well as in difficult-to-access areas. For the successful implementation of these applications, an IoT device should be small and autonomous, while incorporating sensors, data processing and wireless communication capabilities. These simple conditions imply storage and power management limitations for the IoT devices in order to ensure their continued operation, since neither replacing the power cord nor the battery are viable choices under these conditions or simply because of the flexibility (fast installation without cable, no maintenance). Major growth opportunities in the coming years are expected in wireless power transmission and solar harvesting technologies approved for powering IoT devices. This increase is justified by significant advances in material science, engineering and extensive prototyping. Innovative energy storage solutions for IoT have already appeared in the market. In terms of energy management, a range of integrated solutions are available on the market to supply IoT devices that vary from home, up to industrial applications. RF charging, alongside other WPT technologies and ambient energy harvesters are today viable integrated energy sources for small, portable or not, devices. In this thesis, methods of efficient wireless electromagnetic radiation charging have been developed to improve the charging quality of unstructured communication networks and to develop IoT systems that will be able to utilize this technology. In particular, we present novel algorithmic methods based on a new, more realistic and accurate wireless power transfer model, which can efficiently capture constructive and destructive interference of the electromagnetic waves. These methods deal with problems such as i) charger’s power level, phase configuration and deployment towards power maximization, and ii) find low EM radiation paths in WPT systems. Besides the algorithmic perspective, modern energy provisioning approaches aim to combine different technologies that decouple harvesting from the environment and efficiently manage the available energy. Thus, we present novel IoT energy management platforms that integrate both RF-charging and ambient energy harvesting to power sensing and communication devices. Those platforms are utilised in a real application in the context of Smart Roads and are responsible to power a list of sensors and the corresponding communication module in a sufficient way.
Wireless power transfer, RF charging