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The title of the thesis: Secure Backscatter Communication and Its Applications for Integrated Sensing and Communications Systems

Thesis defender: Yifan Zhang
Opponent: Prof. Markku Juntti, University of Oulu, Finland
Custos: Prof. Riku Jäntti, Aalto University School of Electrical Engineering

Securing the Green Internet of Things: Innovative Solutions for Backscatter Communication

As the world moves toward a future of billions of connected devices, traditional battery-powered electronics face a sustainability crisis. Backscatter Communication (BC) has emerged as a revolutionary solution, enabling tiny sensors to communicate by simply reflecting existing radio signals, such as Wi-Fi or TV broadcasts, rather than generating their own power-hungry waves. However, because these devices are so simple, they are often easy targets for hackers and struggle to balance data transmission with environmental sensing. This doctoral thesis addresses these critical gaps by developing lightweight security and optimizing how these devices coexist within next-generation 6G wireless networks.

To protect these low-power devices from cyber-attacks, the research introduces a series of high-efficiency authentication protocols. Unlike traditional security that requires heavy computing power, these new methods use the unique fingerprints of radio signal reflections to verify device identities. The study demonstrates that even simple sensors can effectively defend against spoofing and data counterfeiting with a high degree of accuracy, achieving a 95% success rate in identifying legitimate users even when the devices are in motion. These mechanisms ensure that "green" IoT networks remain secure without draining their limited energy.

Beyond security, the thesis provides a blueprint for Integrated Sensing and Communication (ISAC), a key feature of future networks where devices perceive their physical surroundings while transmitting data. By developing new mathematical algorithms, the research shows how to intelligently allocate time and power to boost system efficiency by more than 20% compared to current standards. These results provide practical pathways for deploying secure, battery-less sensors in smart cities, industrial warehouses, and healthcare monitoring, ensuring that the next generation of wireless technology is both environmentally sustainable and digitally resilient.

Key words: Backscatter Communications, Physical Layer Security, Integrated Sensing and Communications Systems

Thesis available for public display 7 days prior to the defence at .