Talk Title: Degrees of Freedom of the Field and Upper Bounds for the Number of MIMO Independent Channels

Abstract: Massive Multiple Input Multiple Output (M-MIMO) technology has significantly advanced base station antenna design by integrating many transceivers with antenna arrays, improving network capacity and managing complex interference dynamically. Advanced antenna modeling and theory are therefore essential today for the accurate prediction and assessment of system performance of next generation of communication systems. In this talk, we propose a theoretical framework that emphasizes the joint design of system algorithms and antennas using exact electromagnetic (EM) field representations. This approach defines novel parameters for the quantification of antenna array performances, and defines design strategies to maximize the number of independent channels, the average efficiency, and the maximum average gain within a specific cell. By exploring the degrees of freedom (DoF) of the EM field, we establish the physical upper bounds for system performance, providing a comprehensive understanding of antenna potential. The talk details the Embedded Element Patterns (EEPs), their associate Efficiency Correlation Matrix (ECM), Cell Correlation Matrix (CCM), and orthogonal field modes, discussing the practical implications of these concepts for MIMO systems. The findings underscore the significance of sophisticated antenna models in enhancing network capacity, efficiency, and reliability. This research contributes to the optimization of antenna arrays in next-generation mobile networks.

Talk Title: Reflective Intelligent Surfaces: An Interdisciplinary Innovation Platform

Abstract: Reflective Intelligent Surfaces (RIS) represent a transformative innovation at the intersection of electromagnetics and materials science. This talk will explore the evolution and future potential of RIS as a key component of next-generation wireless communication systems. By harnessing reconfigurable and tunable metamaterials, RIS has emerged as a crucial technology to enhance wireless coverage, manipulate the electromagnetic environment, and achieve unprecedented efficiency in signal transmission and reception. The discussion will include an overview of RIS technology, highlighting its applications and challenges, such as the tunable material limitations and the interference issues inherent in current implementations. Additionally, we will review ongoing projects, including the £2M EPSRC-funded ANIMATE initiative, which aims to address these limitations through a cross-disciplinary approach to software-defined materials and metasurfaces. The talk will also address the fundamental limits of RIS, its impact on network coexistence, and the regulatory implications for deployment. A vision for future developments will be presented, focusing on the convergence of RIS with machine learning and automated design tools, to build adaptive, intelligent communication systems capable of self-optimization in real time.

Talk Title: Toward a Physical-Model-Based Universal Framework for Wave Control in Next-Generation Extremely Tunable Microwave Systems

Abstract: The next generation of microwave systems for communications, sensing and wave-based signal processing requires extreme tunability to realize completely different transfer functions with the same system, leading to a massive system parametrization with hundreds or more of tunable elements. Such systems defy conventional design and deployment wisdom, notably because of their high-dimensional design space involving intertwined effects of tunable elements due to mutual coupling. The first step to mastering wave control in an extremely tunable microwave system consists in compactly representing and efficiently navigating this design space. In this talk, I present our recent efforts toward this goal, and some of their ramifications. Specifically, I will discuss how to formulate compact physical models and how to calibrate their parameters to describe a given experimental tunable system, even without knowing the latter’s design details. In the realm of smart radio environments, this corresponds to end-to-end physics-compliant channel estimation, and we show that it is possible purely based on non-coherent detection. Next, I will discuss ambiguities in this parameter estimation problem, and how they can be lifted by additionally constraining the problem. This leads to the concept of the “Virtual Vector Network Analyzer” that leverages tunable elements as “virtual ports” to the system and determines the full augmented scattering matrix (comprising actual and virtual ports) free of any ambiguity, without ever inputting or outputting waves via the “virtual ports”. Finally, I show how the described model formulation and calibration efforts enable conjugate beam-forming toward a user equipment without pilot exchange.

Talk Title: Beyond Diagonal Reconfigurable Intelligent Surfaces: The Next Generation of RIS for Smart Radio Environments

Abstract: Reconfigurable intelligent surface (RIS) is expected to be a key technology in 6G to enhance wireless systems by efficiently and cost-effectively manipulating the propagation environment. In conventional RIS, or RIS 1.0, each RIS element is independently controlled by a tunable load disconnected from the other elements. Thus, RIS 1.0 results in a diagonal phase shift matrix, which limits the passive beamforming flexibility. In this talk, we introduce beyond diagonal RIS (BD-RIS), or RIS 2.0, as a generalization of RIS 1.0 in which the phase shift matrix is not restricted to being diagonal. We explain the modeling of BD-RIS through scattering parameter network analysis, present the recently proposed BD-RIS architectures, and illustrate the benefits of BD-RIS. Finally, we outline the open challenges and future research directions for BD-RIS.

Talk Title: Transmitting and Reflecting RIS for Enhanced Communication and Sensing

Abstract: In this talk we present recent advances on Reconfigurable Intelligent Surfaces operating in transmitting, reflecting or dual mode.  The impact on channel characteristics and their exploitation for enhanced communication coverage, localization accuracy  and sensing are presented with practical proof of concepts and trails.

Talk Title: Communication, Sensing, Localisation using Smart Surfaces

Abstract: Future wireless networks are expected be more than allowing people, mobile devices, and objects to communicate with each other. The sixth generation (6G) of mobile networks are envisioned to include high data rate applications and ultra-massive, connected things. One of the enabling technology for 6G is Reconfigurable Intelligent Surfaces (RIS)  which represent a groundbreaking advancement in wireless communication and smart environments, enabling the dynamic control and manipulation of electromagnetic waves. These surfaces, composed of a large array of sub-wavelength-sized elements, can be programmed to adapt their reflection, refraction, and transmission properties in real time. This talk will explore the fundamental principles behind RIS, various designs strategies and their applications in real life including coverage enhancement, healthcare and localisation.

Talk Title: Light-Based Computation

Abstract: In recent years, we have been exploring how wave interaction with metamaterials can provide a new platform for ultrafast, low-energy optical analog computing.  We have investigated how wave interaction with judiciously designed material platforms can perform mathematical operations such as matrix inversion, vector-matrix multiplication, integral and different equation solving, etc.  We have demonstrated these functionalities in the radio-frequency, microwave, and optical frequency domains.  We have also shown how such material-based, wave-based analog computing machines can provide parallel computation, in which a single structure can perform more than one operation, such as solving two equations or inverting several matrices simultaneously.  We have also demonstrated reconfigurable/programmable wave-based RF systems that can perform optimization.  These light-based computing platforms can benefit AI applications, providing a wave-physics-based approach to AI and machine learning.

In this talk, I will give an overview of our projects and will present the results of some of our ongoing work on metamaterial-based, light-based analog computing.

Talk Title: Towards Channel Stabilisation via Reconfigurable Intelligent Surfaces

Abstract: We introduce the concept of network stabilization through surface-assisted wireless communications. This paradigm represents a form of over-the-air processing of the wireless signals done by injecting artificially controlled scatterers, e.g., reconfigurable intelligent surfaces, within the propagation environment. In general, the onset of signal stability is underpinned by the fundamental concept of channel hardening, which is achieved by harnessing multipath fading propagation and by self-averaging over large receiving (or re-radiation) apertures. Theoretical predictions based on extended random matrix theory are briefly discussed and a laboratory assessment developed for rich fading scenarios. Modern electromagnetic-based communication models including scattering clusters are adopted to study channel hardening bounds in real-life environments. A few applications benefitting from channel stabilization are presented and discussed, which entail interference management, coexistence, and classification in multi-user networks.