Faculty of Science, Technology and Medicine
Faculty of Law, Economics and Finance
Faculty of Humanities, Education and Social Sciences
Interdisciplinary Centre for Security, Reliability and Trust
Luxembourg Centre for Systems Biomedicine
Luxembourg Centre for Contemporary and Digital History
Luxembourg Centre for European Law
Luxembourg Centre for Socio-Environmental Systems
The Doctoral School in Science and Engineering is happy to invite you to Moustafa Samy MAHMOUD ZEAARBAN’s defence entitled
Modeling and design of reconfigurable intelligent surfaces-assisted mobile networks
Supervisor: Prof Björn OTTERSTEN
Intelligent and flexible antenna systems, such as reconfigurable intelligent surfaces (RIS), beyond diagonal RIS and pinching antennas, have attracted significant research attention due to their ability to effectively improve wireless channels. In this thesis, we analyze and investigate the modeling and design of these advanced antenna systems to enhance the wireless network performance. We first propose several deployment scenarios and use cases involving multiple RISs within the wireless network. In particular, we focus on relaying networks that combine multiple RISs and conventional relays to enhance the rate performance and extend the coverage of the wireless network. The conducted simulation results show that these hybrid network architecture can significantly improve outage performance compared to purely RISs or purely relays networks.
Moreover, we extend the scope beyond conventional RIS by proposing a channel estimation method and providing a comprehensive performance analysis of beyond-diagonal RIS architectures. In particular, a novel channel estimation protocol is proposed that integrates the general ON/OFF protocol for conventional RIS channel estimation with the unique capabilities of the beyond diagonal RIS interconnections and the least squares (LS) estimator. Complexity analysis shows that our proposed protocol achieves similar complexity to that of conventional diagonal RIS. For performance analysis, comprehensive evaluations are carried out across fully-connected, group-connected, and multisector beyond-diagonal RIS architectures under various fading channel models, aiming to identify the inherent trade-offs among these design configurations. For this, we derive accurate closed-form expressions for key performance metrics, including achievable spectral efficiency, outage probability, symbol error probability (SEP), and diversity order. To further evaluate the practical feasibility of beyond diagonal RIS, we develop a realistic power consumption model and analyze the resulting energy efficiency performance. Results show that fully-connected architecture offers higher performance gains at the cost of lower energy efficiency, whereas the group-connected architecture provides a better trade-off, maintaining spectral efficiency close to that of the fully-connected design while improving energy efficiency.
Next, we compare RIS technology with pinching antennas systems, as an example of flexible antenna architectures, in millimeter-wave (mmWave) bands to assess which architecture provides a superior performance–energy trade-off. The comparison shows that RIS requires massive number of elements to be competitive with pinching antenna systems in terms of spectral efficiency, which severely impact the energy efficiency performance of RIS. On the other hand, pinching antenna systems demand a more complex deployment setup, including mechanisms for linear movement and pinching action. Finally, we outline possible directions for future work, including the exploration of new RIS architectures such as distributed beyond-diagonal RIS designs, as well as the integration of RIS with quantum communication systems for enhanced quantum key distribution (QKD) performance.