IEEE International Symposium on Personal, Indoor and Mobile Radio Communications
13–16 September 2021 // Virtual Conference // By 6G Flagship

Reconfigurable Intelligent Surfaces for Future Wireless Communications


Dr. Alessio Zappone,
University of Cassino and Southern Lazio, Italy

Dr. Alessio Zappone obtained his Ph.D. degree in electrical engineering in 2011 from the University of Cassino and Southern Lazio, Cassino, Italy. His Ph.D. studies were focused on distributed algorithms for energy-efficient resource allocation in wireless networks. After obtaining his Ph.D. Alessio has been with the Technische Universitat Dresden, Germany, managing the project CEMRIN on energy-efficient resource allocation in wireless networks, funded by the German Research Foundation. From 2017 to 2019 he has been the recipient of the H2020 Individual Marie Curie fellowship for experienced researchers BESMART, carried out in the LANEAS group of CentraleSupelec, Paris, France. He is now a tenured professor at the university of Cassino and Southern Lazio, Italy. He was appointed multiple times exemplary reviewer for the IEEE Transactions on Communications and IEEE Transactions on Wireless Communications. Alessio is an IEEE Senior Member, serves as senior area editor for the IEEE Signal Processing Letters and as guest editor for the IEEE Journal on Selected Areas on Communications (Special Issues on Energy-Efficient Techniques for 5G Wireless Communication Systems and on Wireless Networks Empowered by RIS). He is currently the chair of the special interest group REFLECTIONS, activated within the SPCC technical committee and which focuses on RIS for signal processing and communications. He is also the founding vice-chair of the Emerging Technology Initiative on RISs for Smart Radio Environments of the IEEE Communications Society.

Dr. Marco Di Renzo,
CNRS, University Paris-Saclay, France

Dr. Marco Di Renzo received the Ph.D. degree in Electrical and Information Engineering from the University of L’Aquila, Italy, in 2007. Since 2010, he is Associate Professor with Paris-Saclay University – CNRS, CentraleSupelec, Univ. Paris Sud, France. He is a Distinguished Visiting Fellow of the Royal Academy of Engineering (UK), and co-founder of the university spin-off company WEST Aquila s.r.l., Italy. Dr. Di Renzo received the THALES Communications fellowship (2003-2006), University of L’Aquila, Italy; the Dèrogation pour l’Encadrement de These (2010), University of Paris-Sud, France; the 2012 IEEE CAMAD, 2014 IEEE CAMAD, 2014 IEEE ATC, 2015 IEEE ComManTel Best Paper Awards; the 2012 and 2014 IEEE WIRELESS COMMUNICATIONS LETTERS Exemplary Reviewer Certificate; the 2013 IEEE-COMSOC Best Young Researcher Award for Europe, Middle East and Africa; the 2015-2018 CNRS Award for Excellence in Research and in Advising Doctoral Students; the 2017 IEEE-SEE Alain Glavieux Award. He serves as Editor in Chief of the IEEE COMMUNICATIONS LETTERS and Editor of the IEEE TRANSACTIONS ON COMMUNICATIONS. He is an IEEE Fellow and a Distinguished Lecturer of the IEEE Communications and IEEE Vehicular Technology Societies.
Dr. Di Renzo guest-edited the JSAC special issue on Wireless Networks Empowered by RIS and he currently serves as the chair of the special interest group RISE, activated within the wireless technical committee and which focuses on RIS for signal processing and communications. He also serves as founding Liaison Officer of the Emerging Technology Initiative on RISs for Smart Radio Environments of the IEEE Communications Society, on behalf of the IEEE Emerging Technical Committee.

Dr. Shi Jin,
Southeast University, China

Dr. Shi Jin received the M.S. degree from Nanjing University of Posts and Telecommunications, Nanjing, China, in 2003, and the Ph.D. degree in information and communications engineering from the Southeast University, Nanjing, in 2007. From June 2007 to October 2009, he was a Research Fellow with the Adastral Park Research Campus, University College London, London, U.K. He is currently with the faculty of the National Mobile Communications Research Laboratory, Southeast University. His research interests include space time wireless communications, random matrix theory, information theory. He serves as an Associate Editor for the IEEE Transactions on Wireless Communications, IEEE Communications Letters, IET Communications. Dr. Jin and his coauthors have been awarded the 2011 IEEE Communications Society Stephen O. Rice Prize Paper Award in communication theory and a 2010 Young Author Best Paper Award by the IEEE Signal Processing Society. Dr. Jin serves as the founding Officer for Testbeds, Devices and Proof-of-Concepts of the Emerging Technology Initiative on RISs for Smart Radio Environments of the IEEE Communications Society.

Dr. Merouane Debbah,
Huawei France R&D, France

Dr. Debbah obtained his Ph.D. from the Ecole Normale Suprieure Paris-Saclay (France). He worked for Motorola (France) from 1999-2002 and Vienna Research Center for Telecommunications (Austria) until 2003. From 2003 to 2007, he joined the Mobile Communications department of Eurecom (France). Since 2007, he is Full Professor at CentraleSupelec (France). Since 2014, he is Vice-President of the Huawei France R\&D center and director of the Mathematical and Algorithmic Sciences Lab. He is Associate Editor in Chief of the journal Random Matrix: Theory and Applications and was associate and senior area editor for IEEE Transactions on Signal Processing. He obtained the ERC grant MORE and is IEEE Fellow. He received 19 best paper awards, among which the 2007 IEEE GLOBECOM best paper award, 2014 WCNC best paper award, 2015 ICC best paper award, 2015 IEEE Communications Society Leonard G. Abraham Prize, 2015 IEEE Communications Society Fred W. Ellersick Prize, 2016 IEEE Communications Society Best Tutorial paper award, 2018 IEEE Marconi Prize Paper Award. He received the Mario Boella award in 2005, the IEEE Glavieux Prize Award in 2011 and the Qualcomm Innovation Prize Award in 2012. Dr. Debbah serves as the founding Industry Liaison Officer within the Emerging Technology Initiative on RISs for Smart Radio Environments of the IEEE Communications Society.


As 5G networks take their final form, connectivity demands continue to increase exponentially and new services pose more performance constraints. A technological breakthrough with the potential to meet these demands is that of reconfigurable intelligent surfaces. RIS-based communications put forth the idea of treating the communication environment not as a fixed entity, but as an optimization variable. In principle, the possibility of creating more convenient electromagnetic paths is already provided by the use of relay stations. However, relays are based on traditional active antenna technology with transmit amplifiers and complex hardware circuitry, leading to large power consumptions, large size of the devices, and high costs. Instead, RISs are nearly-passive structures with very limited power consumption, size, and deployment costs. RISs are planar structures made of special materials, known as meta-materials, on which elementary electromagnetic reflectors are placed and spaced at sub-wavelength distances. RISs can reflect/refract incoming electromagnetic signals in directions that can be fully customized. RISs can be configured in real-time, adapting to the sudden changes of the network and/or of the traffic demands. RISs can be deployed on the walls of buildings or can be used to coat the environmental objects between the communicating devices, which effectively makes the wireless channel a new variable to be optimized. Thanks to their reduced size and cost, RISs can be equipped with a much larger number of reflectors than the number of antennas in traditional antenna arrays. A tutorial on the principles and latest approaches of RIS will be of great value for both academics and industry practitioners.

This tutorial is endorsed by the Emerging Technology Initiative on RISs for Smart Radio Environments of the IEEE Communications Society, in which A. Zappone is the founding vice-chair, M. Di Renzo, is the founding liason officer on behalf of the IEEE emerging technology committee, S. Jin is the founding officer for testbeds, devices, and Proof-of-concepts, M. Debbah is the founding industry liason officer.

Moreover, this tutorial is also endorsed by the special interest groups REFLECTIONS, chaired by A. Zappone and activated within the SPCC-TC, and RISE, chaired by M. Di Renzo and activated within the WTC.

Structure and content

Introduction. The tutorial starts by discussing 5G standardization activities, the performance that 5G networks will be able to grant, and how this appears inadequate to keep the pace with the exponentially increasing number of connected devices and with therise of many new heterogeneous services. The main challenges thatstand in our way towards meeting the requirements of future networks will be identified, namely the extreme heterogeneity of the tasks to execute, which range from broadband communications, tovery low-latency communications, extreme energy efficiency and high data rates, and localization.  The use of  RIS  to enable this 6G vision will be discussed. Both an academic and industrial perspective will be provided. Moreover, the economical and societal opportunities that overcoming 5G holds will be analyzed. After this first part, the audience will have a proper understanding of the main principles that make the RIS technology possible, of the potential of RISs, and of the challenges and opportunities related to overcoming 5G networks.

Meta-material fundamentals and experimental results. This part of the tutorial will introduce the fundamentals of meta-material technology and, in order to substantiate the gains that RIS can bring to wireless communications, will present experimental results obtained by using the world’s first meta-surface assisted wireless prototype testbed for RIS-based communications, which has been developed at Southeast university by the group of Prof. Shi Jin. The tutorial will explain how packing reflecting elements at sub-wavelength distances enables to obtain a non-homogeneous surface for which the conventional Snell’s laws do  not  hold. Experimental results will show that, despite not having any transmit amplifier, by properly designing the elementary reflecting elements, it is possible to achieve high data-rates. Moreover, by embedding stimuli-responsive materials in the meta-surface, e.g. liquid crystals or magnetic ferrite, which can rapidly vary their physical properties inresponse to external stimuli, it is possible to dynamically program the behavior of the meta-surface in real-time. The tutorial will show how RISs can be used to improve the communication reliability (e.g. by ensuring that the different signal paths add coherently at the receiver), energy efficiency (since RISs can increase the data-rate with an extremely limited energy consumption), and security (since RIS can be used to focus the reflected/refracted energy only towards desired directions).

Modeling and Design of RIS-based wireless networks. This part of the tutorial will address both modeling and design issues of RIS-based wireless networks, presenting the latest research trends in both directions. Specifically, at first the tutorial will introduce equivalent electromagnetic-based and physics-inspired mathematical models of  RIS,  showing  how  they can  be  employed to model RIS-based wireless networks, in order to come to new expressions of the SNR in a RIS-based communication channel. Next, it will be shownhow the unique properties of RISs  are  expected to yield different scaling laws from those currently encountered in wireless networks, e.g., a different received power expression as a function of the distance between transmitters and receivers, or a received SNR as a function of the number of reflecting elements equipped at the RIS. As a result of this discussion, the advantages and limitations of RISs will be discussed in comparison with other more traditional technologies, such as massive MIMO and relaying. In this context, it will be also observed how RISs can be used to perform specific tasks in a much simpler and more energy-efficient way than with available transmission technologies, such as implementing spatial modulation techniques, improving the security and reliability of wireless networks. Also, the  tutorial will elaborate on how RISs can be used for improving the performance of wireless networks, e.g., for communication at high frequency bands, such as the mmWave frequency range.

Then, the tutorial will address the most recent results and techniques for the optimization of RIS-based wireless networks. At first, the new optimization challenges posed by the use of RISs will be identified, and a thorough literature survey about resource allocation for RIS-based wireless networks design will be given. Namely, the fact that the RIS is a (nearly) passive device without neither a dedicated transmit and receive hardware, nor a digital signal processor, results in: 1) more challenging resource allocation problems to solve; 2)more sophisticated channel estimation and feedback protocols, which poses additional constraints on the resource allocation algorithms, and leads to the need of performing overhead-aware resource allocation as well as joint channel estimation and resource allocation, unlike what typically happens for the design of present wireless communication systems. As a first step, the latest techniques for resource allocation in RIS-based wireless networks will be discussed, without explicitly accounting for the channel estimation and feedback phases. Both point-to-point and multi-user MIMO wireless networks will be considered and it will be shown how to handle the more challenging resource allocation problems encountered when designing RIS-based wireless networks. Different performance metrics will be optimized, including the system spectral efficiency, energy efficiency, and their trade-off, with respect to the RIS phase shifts, the number of RIS reflecting elements, the transmit powers, transmit beamforming, and receive filters. Moreover, it will be shown how the previous approaches can be extended to the scenario in which the overhead related to channel estimation and to the computation and configuration of the optimal RIS phase matrix are explicitly accounted for in the resource allocation problem. This leads to a more challenging optimization  problem, which is solved again with respect to the RIS phase shifts, the number of RIS reflecting elements, the transmit powers, transmit beamforming, and receive filters. Also in this case, different performance metrics are optimized including the system spectral efficiency, energy efficiency, and their trade-off. Overhead-aware algorithms for the optimization of the RIS phase shifts, the number of RIS reflecting elements, the transmit powers, beamformers, and receive filters will be presented. Different performance metrics are optimized including the spectral efficiency, energy efficiency, and their trade-off.