Periodic Reporting for period 1 - SURFER (SUrface waves in smart Radio Frequency EnviRonments)
Période du rapport: 2022-03-01 au 2024-02-29
The radio communication division of the international telecommunication union (ITU-R) has recently drafted new recommendations for the international mobile telecommunication 2030 (IMT-2030) framework, which is referred to as the sixth generation (6G) of telecommunication standards. In the past decade, several advanced wireless technologies, including small cells, millimeter-wave communications, and massive multiple-input multiple-output (MIMO) systems, have been proposed to enhance the network capacity and to enable ubiquitous wireless connectivity. The practical implementation and deployment of these technologies is, however, often limited by the associated prohibitive energy consumption and expensive hardware equipment. As a result, it has become apparent that 6G communication networks need to undergo a fundamental shift of design paradigm, which requires to include aspects of (energy) sustainability, besides those of network capacity and connectivity, at the design stage. This change of design paradigm requires radically new physical layer technologies.
In this context, we are assisting to the upsurge in brand-new technologies for the physical layer, which rely on encoding, processing, and decoding information in the wave domain, i.e. at the electromagnetic level, as opposed to conventional physical layer technologies that rely on digital information processing. The advantages of wave domain information processing include improved computational efficiency, simplified hardware architectures, and reduced energy consumption. This emerging trend has been facilitated by recent results in the field of configurable antennas and, especially, metasurfaces, which are engineered materials capable of processing the electromagnetic waves in the wave domain without the need of analog-to-digital and digital-to-analog conversions.
Examples of emerging technologies include (i) spatial, index, media-based, metasurface modulation, which encode information onto physical characteristics of antennas and metasurfaces; (ii) reconfigurable intelligent surfaces (RISs), which improve the transmission of data by appropriately shaping the propagation of electromagnetic waves at the electromagnetic level, turning radio propagation environments into smart radio propagation environments; (iii) holographic surfaces (HoloSs), which are continuous-aperture hybrid MIMO systems, where the data encoding and decoding is performed in the wave domain; (iv) stacked intelligent surfaces (SIMs), which are multi-layer metasurface-based devices, which resemble deep neural networks, where the data encoding and encoding is realized through signal processing operations in the wave domain; (v) fluid antenna systems; and (vi) surface wave communications (SWC), which are aimed to capitalize on the properties of surface waves (evanescent waves) for realizing efficient wave transformations.
Despite the potential performance gains and applications that these technologies may provide in future wireless networks, the major limiting factor preventing information, communication, and signal processing theorists from realizing their full potential and unveiling their ultimate performance limits lies in understanding the electromagnetic and physical properties and limitations underpinning them. Key open problems include how to appropriately model the physics of signal propagation and the processing of signals performed by these emerging devices in the wave domain. To overcome this status quo, it is necessary to cut across the current and established disciplinary boundaries between information, signal, and electromagnetic theories.
The objective of the SURFER project lies in developing a framework for modeling and optimizing wireless systems that use free-space waves and surface waves in order to enhance the performance of future networks and making them sustainable by design thanks to wave domain processing.
In this context, we are assisting to the upsurge in brand-new technologies for the physical layer, which rely on encoding, processing, and decoding information in the wave domain, i.e. at the electromagnetic level, as opposed to conventional physical layer technologies that rely on digital information processing. The advantages of wave domain information processing include improved computational efficiency, simplified hardware architectures, and reduced energy consumption. This emerging trend has been facilitated by recent results in the field of configurable antennas and, especially, metasurfaces, which are engineered materials capable of processing the electromagnetic waves in the wave domain without the need of analog-to-digital and digital-to-analog conversions.
Examples of emerging technologies include (i) spatial, index, media-based, metasurface modulation, which encode information onto physical characteristics of antennas and metasurfaces; (ii) reconfigurable intelligent surfaces (RISs), which improve the transmission of data by appropriately shaping the propagation of electromagnetic waves at the electromagnetic level, turning radio propagation environments into smart radio propagation environments; (iii) holographic surfaces (HoloSs), which are continuous-aperture hybrid MIMO systems, where the data encoding and decoding is performed in the wave domain; (iv) stacked intelligent surfaces (SIMs), which are multi-layer metasurface-based devices, which resemble deep neural networks, where the data encoding and encoding is realized through signal processing operations in the wave domain; (v) fluid antenna systems; and (vi) surface wave communications (SWC), which are aimed to capitalize on the properties of surface waves (evanescent waves) for realizing efficient wave transformations.
Despite the potential performance gains and applications that these technologies may provide in future wireless networks, the major limiting factor preventing information, communication, and signal processing theorists from realizing their full potential and unveiling their ultimate performance limits lies in understanding the electromagnetic and physical properties and limitations underpinning them. Key open problems include how to appropriately model the physics of signal propagation and the processing of signals performed by these emerging devices in the wave domain. To overcome this status quo, it is necessary to cut across the current and established disciplinary boundaries between information, signal, and electromagnetic theories.
The objective of the SURFER project lies in developing a framework for modeling and optimizing wireless systems that use free-space waves and surface waves in order to enhance the performance of future networks and making them sustainable by design thanks to wave domain processing.
During the execution of the project, major results have been achieved, which are concerned about the understanding of surface wave communications and their implications in communication networks, which include their role to increase the energy efficiency in wireless communication networks to realize efficient reflecting based surfaces, their modeling by utilizing the plane-wave spectrum representation of electromagnetic fields and Floquet theory, as well as their integration with free-space communications, especially with reconfigurable intelligent surfaces. As far as this latter point is concerned multiport network theory has been utilized to develop electromagnetically consistent models and optimization algorithms.
During the execution of the project, four papers were published:
N. S. Perović, L. -N. Tran, M. Di Renzo and M. F. Flanagan, "On the Maximum Achievable Sum-Rate of the RIS-Aided MIMO Broadcast Channel," in IEEE Transactions on Signal Processing, vol. 70, pp. 6316-6331, 2022, doi: 10.1109/TSP.2022.3229945.
A. Mohamed, N. S. Perović and M. Di Renzo, "Intelligent Omni-Surfaces (IOSs) for the MIMO Broadcast Channel," 2022 IEEE 23rd International Workshop on Signal Processing Advances in Wireless Communication (SPAWC), Oulu, Finland, 2022, pp. 1-5, doi: 10.1109/SPAWC51304.2022.9833922.
H. El Hassani, X. Qian, S. Jeong, N. S. Perović, M. Di Renzo, P. Mursia, V. Sciancalepore, X. Costa-Pérez, "Optimization of RIS-Aided MIMO – A Mutually Coupled Loaded Wire Dipole Model," in IEEE Wireless Communications Letters, doi: 10.1109/LWC.2023.3341089.
Nemanja Stefan Perovic, Le-Nam Tran, Marco Di Renzo, Mark F. Flanagan: Optimization of RIS-aided SISO Systems Based on a Mutually Coupled Loaded Wire Dipole Model. CoRR abs/2305.12735 (2023).
During the execution of the project, four papers were published:
N. S. Perović, L. -N. Tran, M. Di Renzo and M. F. Flanagan, "On the Maximum Achievable Sum-Rate of the RIS-Aided MIMO Broadcast Channel," in IEEE Transactions on Signal Processing, vol. 70, pp. 6316-6331, 2022, doi: 10.1109/TSP.2022.3229945.
A. Mohamed, N. S. Perović and M. Di Renzo, "Intelligent Omni-Surfaces (IOSs) for the MIMO Broadcast Channel," 2022 IEEE 23rd International Workshop on Signal Processing Advances in Wireless Communication (SPAWC), Oulu, Finland, 2022, pp. 1-5, doi: 10.1109/SPAWC51304.2022.9833922.
H. El Hassani, X. Qian, S. Jeong, N. S. Perović, M. Di Renzo, P. Mursia, V. Sciancalepore, X. Costa-Pérez, "Optimization of RIS-Aided MIMO – A Mutually Coupled Loaded Wire Dipole Model," in IEEE Wireless Communications Letters, doi: 10.1109/LWC.2023.3341089.
Nemanja Stefan Perovic, Le-Nam Tran, Marco Di Renzo, Mark F. Flanagan: Optimization of RIS-aided SISO Systems Based on a Mutually Coupled Loaded Wire Dipole Model. CoRR abs/2305.12735 (2023).
The work done during the project has significantly progressed the state-of-the-art along two main directions:
(1) It has allowed us to understand the applications of surface waves in communications, with focus on their role to realize efficient metasurfaces in which the power flow can be optimally controlled and directed towards the desired directions by reducing undesired radiated beams. Based on the know-how acquired during the project, appropriate integrated communication models and optimization algorithms are under development based on the global design criterion and Floquet theory.
(2) By using multiport network theory, a general communication model that accounts for the mutual coupling between the radiating elements of metasurfaces has been developed along with a suite of efficient optimization algorithms.
The societal impact of these research works is the development of new physical layer technologies that will be sustainable by design, reducing the network power expenditure, as high energy efficient solutions can be developed by minimizing the number of active elements.
Future research work includes the solution of optimization algorithms based on the know-how acquired in (1) and their integration with the algorithms already developed in (2).
(1) It has allowed us to understand the applications of surface waves in communications, with focus on their role to realize efficient metasurfaces in which the power flow can be optimally controlled and directed towards the desired directions by reducing undesired radiated beams. Based on the know-how acquired during the project, appropriate integrated communication models and optimization algorithms are under development based on the global design criterion and Floquet theory.
(2) By using multiport network theory, a general communication model that accounts for the mutual coupling between the radiating elements of metasurfaces has been developed along with a suite of efficient optimization algorithms.
The societal impact of these research works is the development of new physical layer technologies that will be sustainable by design, reducing the network power expenditure, as high energy efficient solutions can be developed by minimizing the number of active elements.
Future research work includes the solution of optimization algorithms based on the know-how acquired in (1) and their integration with the algorithms already developed in (2).