Nemanja Stefan PEROVIC
Nemanja Stefan Perović (Member, IEEE) received the B.S. and M.S. degrees from the Department of Electronics, Faculty of Electrical Engineering, Belgrade University, in 2008 and 2009, respectively. For a short time during 2010, he worked as an Engineer of the Emission Technics of the Radio Television of Serbia. In 2011, he started his Ph.D. studies at the Department of Telecommunications, Belgrade University. In 2013, he restarted his Ph.D. studies at Johannes Kepler University (JKU) Linz, where he received the Ph.D. degree in 2018. From 2017 to 2018, he also worked as an RF Transceiver validation-Research and Development Engineer with Danube Mobile Communications Engineering (DMCE), Intel Linz. In the period from 2019 to 2022, he was as a Post-Doctoral Research Fellow with University College Dublin, Ireland. From March 2022, he has been working as a MSCA Research Fellow at Université Paris-Saclay, CNRS, CentraleSupélec. He is currently serving as a Managing Editor of IEEE Communications Letters and a Review Editor of Frontiers in Communications and Networks.
nemanja-stefan.perovic@l2s.centralesupelec.fr
L2S, CentraleSupélec
Bât. Breguet A5.21
3 rue Joliot Curie
91190 Gif-sur-Yvette, France
A newly developed approach for overcoming network limitations in wireless communications consists of turning the wireless environment into a controllable and software-reconfigurable space (i.e., smart radio environment (SRE)). A majority of research efforts has already been devoted to reconfigurable intelligent surfaces (RIS) with passive radiation elements that are capable of modifying the radio waves impinging upon it in programmable way. In spite of promising advantages with respect to the high energy efficiency and the low hardware cost, the utilization of programmable metasurfaces (i.e., RISs) may require additional signal processing and network intelligence. Namely, management and control of radio signals for massive connectivity that allow signals to coexist without causing harmful interference is a very challenging task in conditions of free-space communication (FSC), because radio waves unintentionally occupy the entire space, naturally propagate in all directions and additionally are reflected, refracted and scattered after hitting objects. In opposite to FSCs, another recently emerged concept of smart radio environment is based on the use of trapped surface waves (SW), which glide at the interface of materials and whose propagation is inherently confined to the smart surface. Unique advantages of such surface wave communications (SWCs) are much more favorable pathloss and easier interference management. Moreover, SWCs provide various functionalities of smart radio environment and resemble a transportation network of communications superhighways.
1) EM field attenuation as a function of the surface impedance. The EM field of SWs attenuates as it propagates, but due to the confinement of the fields to the surface, the pathloss of trapped waves is more favorable compared to FSCs. The most effective surface for SWCs is the one with a purely reactive surface impedance. A viable solution to obtain such optimal surface impedance implies the use of dielectric coated conductors. The surface impedance can be adjusted and optimized by layering several different dielectric layers on top of each other. Based on this implementation, the application of surface electromagnetics theory, and generalized sheet transition conditions at the boundary of propagating media, the ER will develop analytical models to characterize the attenuation of the EM field of SWs, analytical expressions for the surface impedance, and the relation between them.
2) EM-compliant models. For application to wireless communications, sufficiently accurate and realistic yet analytically tractable models for SWCs and the integration of SWCs and FSCs are needed. This is a challenge, since, depending on the communication scenario, it may be necessary that a meta-atom acts as a radiating element for FSCs on one frequency, and, at the same time, as a propagation medium for SWCs on another frequency. EM-compliant communication models for these metasurfaces will be introduced, by departing from Maxwell’s equations and by applying effective medium theory. Due to the large number of constituent element (i.e., meta-atoms) of the metasurfaces, it is not possible to develop simple models for each of them. Effective medium theory will be used to derive a set of effective parameters that describe metasurfaces as composite materials as a whole by not focusing on individual elements but averaging (over small surfaces) the response of their multiple constituents.
2) EM-compliant models. For application to wireless communications, sufficiently accurate and realistic yet analytically tractable models for SWCs and the integration of SWCs and FSCs are needed. This is a challenge, since, depending on the communication scenario, it may be necessary that a meta-atom acts as a radiating element for FSCs on one frequency, and, at the same time, as a propagation medium for SWCs on another frequency. EM-compliant communication models for these metasurfaces will be introduced, by departing from Maxwell’s equations and by applying effective medium theory. Due to the large number of constituent element (i.e., meta-atoms) of the metasurfaces, it is not possible to develop simple models for each of them. Effective medium theory will be used to derive a set of effective parameters that describe metasurfaces as composite materials as a whole by not focusing on individual elements but averaging (over small surfaces) the response of their multiple constituents.
3) Physics-based communication theoretical models. For application to wireless communications, it is necessary to have end-to-end communication models that have their foundation on the laws of physics. This is a challenging task in general and it is even more complex for SWCs and integrated FSCs+SWCs because of the proximity of the constituent meta-atoms of the metasurfaces. Since the meta-atoms are spaced at sub-wavelength distances, the mutual coupling among them cannot be ignored. However, there exists no end-to-end communication-theoretic model that is mutual coupling aware. In addition, the amplitude and phase response of each meta-atoms are interrelated. To develop a communication model that accounts for these effects, the ER will employ the induced electromagnetic field method in order to compute the mutual impedances between coupled radiating elements that was recently introduced by Prof. Di Renzo for application to FCSs but is unexplored for application to SWCs.
4) Fundamental performance limits. Conventional communication theory is based on Shannon’s theory, which leads to a mathematical theory of communication. In such an abstraction model, EM- and physics-based aspects of the generation of signals, their propagation, and their interaction with the objects is abstracted for the sake of analytical tractability. This is not possible anymore in SWC-based communication because of the propagation of the radio signals occurs in too close proximity of the surface and also the last communication hop based on FSCs in joint SWC+FSC-based communications occurs in the near-field of the surface. This implies that the communication-theoretic models employed so far are not applicable anymore, since they do not account for these effects. In addition, the surfaces can be employed to modulate and encode information to further increasing the channel capacity. The experienced researcher (ER )will develop a new EM theory of communication based on surface electromagnetics theory and the vector form of Green’s theorems that characterize the scattering of radio waves in the presence of objects. The performance limits of SWCs in large wireless networks will be calculated by using stochastic geometry theory.
5) Signal processing and communication protocols. In order to achieve the ultimate performance limits offered by SWCs, the ER will develop signal processing and communication protocols for integrating SWCs into wireless networks. For example, optimized beamforming, modulation, and encoding/decoding schemes are needed in order to efficiency transmitting information in confined environments. To this end, the ER will capitalize on the concept of metasurfaces-based modulation15, which is an innovative low-complexity family of integrated signal processing methods and communication schemes for encoding information on metasurfaces based on the concept of indexing, which is inherently low-complexity, low-cost, energy-efficient, yet spectral-efficient.
6) Experimental assessment The obtained theoretical models and performance limits will be practically verified by using simulation and testbed platforms, during the secondments. During the secondment in Aalto University, the ER will verify the models for metasurfaces using the ARIADNE and VISORSURF testbeds. The link level experimental assessment for SWCs will be done using the TRIMARAN and SPATIALMODULATION platforms based on reconfigurable antennas, during the secondment in Orange. The system-level experiments and the system-level simulation will be conducted using the 5G-NORMA and NEC PASOLINK platforms, and the REMCOM EM-based software during the secondment in NEC. The developed simulator will be made open-access.
SURFER has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 101030536.
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91190 Gif-sur-Yvette
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