Signal Design and Optimization for Wireless Communication Systems Employing Nonlinear RF Energy Harvesting

• Applicant: Professor Dr.-Ing. Robert Schober
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 414988357

The nodes of wireless systems require energy for transmitting communication signals and for performing sensing and processing tasks. Traditionally, this energy has been supplied by electrical wires or batteries. However, wires severely constrain the mobility of the nodes and batteries require manual recharging or replacement. Both solutions are unsuitable for applications with many small or inaccessible nodes (e.g. sensors deployed in hazardous terrain, Internet-of-Things devices, etc.). For such applications, radio frequency (RF) wireless power transfer has gained significant attention as an alternative solution for providing energy to wireless nodes. To maximize the performance of wireless networks relying on RF energy harvesting, a joint design of the signals used for wireless communication and wireless power transfer is needed. Almost all of the existing work on this topic assumes a linear relationship between the received RF power and the harvested energy. However, this assumption, which considerably simplifies design and analysis, is not justified as energy harvesting circuits are inherently nonlinear. Hence, wireless communication systems with RF energy harvesting designed based on a simplistic linear energy harvesting model may suffer from large losses in performance. The signal design and optimization for wireless communication systems employing nonlinear RF energy harvesting circuits, which are the focus of this project, are highly practical and theoretically challenging problems. Building upon our preliminary work, in this project, we will develop accurate yet mathematically tractable nonlinear models for the input-output characteristic of energy harvesting circuits employing multiple diodes. Using these models and the existing nonlinear models for single diode energy harvesting circuits, we will design and optimize the transmit waveforms for different fundamental wireless network architectures with RF energy harvesting nodes, including multiuser systems, multiple-input multiple-output systems, and relay-based systems. For each case, the optimal signal design will be investigated and compared with suboptimal, possibly less complex solutions in order to evaluate the inherent tradeoff between wireless power transfer and wireless information transfer, to develop guidelines for the design of practical systems, and to evaluate the potential of wireless power transfer for future wireless communication networks.

• DFG Programme: Research Grants