IEEE NCS AP-S/MTT-S Chapter

Dr. Costas Sarris: Realistic Propagation Models for RIS-Enabled Communication Channels

Time: Monday, June 24, 2024 at 2:00 pm MDT

Location: University of Alberta – ECERF W2-010

(Refreshments provided)

Prof. Costas Sarris received a Ph.D. in Electrical Engineering and a M.Sc. in Applied and Interdisciplinary Mathematics from the University of Michigan, Ann Arbor, in 2002, and the Diploma in Electrical and Computer Engineering (with distinction) from the National Technical University of Athens (NTUA) in 1997. He joined the University of Toronto in 2002, where he is now a Professor at the Department of Electrical and Computer Engineering. Prof. Sarris was a recipient of the 2021 Premium Award for Best Paper in IET Microwaves, Antennas & Propagation, the IEEE MTT-S Outstanding Young Engineer Award in 2013 and the Early Researcher Award (from the Ontario Ministry for Research and Innovation) in 2007. He is a Distinguished Lecturer of the IEEE Antennas and Propagation Society for 2024-2026. Since 2019, Prof. Sarris has been the Editor-in-Chief of the IEEE Journal on Multiscale and Multiphysics Computational Techniques. He served as Guest Editor of two special issues of the Microwave Magazine on Machine Learning for Microwaves (2021 co-edited with Prof. Q.J. Zhang) and Time-Domain Numerical Methods (2010), an Associate Editor for the IEEE Transactions on Microwave Theory and Techniques (2009-2013) and the IEEE Microwave and Wireless Components Letters (2007-2009). He was the TPC Chair of the 2023 and 2019 MTT-S Numerical Electromagnetics, Multiphysics and Optimization (NEMO) Conference and the 2015 IEEE AP-S International Symposium on Antennas and Propagation and CNC/USNC Joint Meeting in Vancouver, BC; the TPC Vice-Chair of the 2012 IEEE MTT-S International Microwave Symposium, Montreal, QC; the TPC co-Chair for the IEEE AP-S International Symposium on Antennas and Propagation and CNC/USNC Joint Meeting in Toronto, ON, and the Chair of the MTT-S Technical Committee on Field Theory and Computational Electromagnetics (2018-2020). Prof. Sarris received the Faculty Teaching Award from the Faculty of Applied Science and Engineering, University of Toronto in 2021, the Gordon R. Slemon (teaching of design) award in 2007 and four Departmental Teaching Awards (by confidential vote of ECE students, for excellence in undergraduate teaching) in Fall 2021, 2018, 2016 (3rd year Fields and Waves) and Spring 2005 (4th year Radio and Microwave Wireless Systems).

Abstract

Reconfigurable intelligent surfaces (RISs) can redirect incident waves to selected directions in a wireless communication channel, to improve coverage bypassing obstructing objects. This is a promising technology for future wireless networks, particularly those operating at millimeter wave bands.

In practice, several factors affect the performance of an RIS-enabled communication channel. For example, both the transmitter and the RIS radiate waves according to a pattern that includes a main lobe along with sidelobes, leading to enhanced multipath propagation. Moreover, most existing propagation models represent RISs as a collection of independently scattering unit cells, disregarding their mutual coupling that is known to be an important factor in the collective scattering behavior of these surfaces. On the other hand, full-wave methods offer high accuracy, but their computational cost is prohibitive for realistic radio environments.

This presentation introduces a hybrid approach that enables the accurate analysis of RIS-enabled communication channels in rich scattering, realistic environments. Our hybrid method combines the full- wave analysis of the RIS as a diffuse scatterer (including the mutual coupling of unit cells and edge effects), with the computational efficiency of ray-tracing to obtain accurate field predictions in the near and far field region of the RIS at multiple states, accounting for multipath propagation paths towards and from the RIS. We present validation studies based on reference full-wave analysis of relatively small problems and on an extensive indoor measurement campaign.

Finally, we discuss the practical use of our comprehensive propagation model to the site-specific analysis, design, and optimization of RIS structures. We also compare our physics-based approach to RIS channel models that have been presented in the wireless communications literature, thus illustrating the importance of accurately accounting for the physics of radiowave propagation when considering emerging wireless technologies.