For future wireless communications, higher data rate, reliability, and traffic demands will lead to the development of novel communication frameworks that fully exploit the physics of electromagnetic waves. These emerging technologies include holographic MIMO, super-directive antenna array, extremely large antenna arrays, reconfigurable intelligent surfaces, orbital angular momentum (OAM) multiplexing, etc. To explore both potentials and limitations of these technologies, research into electromagnetic and information theory (EIT) is actively underway in both academia and industry. EIT is an interdisciplinary framework integrating electromagnetic wave (EM) theory and information theory (IT) for the analysis of physical systems for the communication, processing, and storage of information. It has been shown that physically large antenna arrays, large intelligent surfaces, RF lens antenna arrays, holographic MIMO, and/or continuous-aperture MIMO can be analyzed more effectively within an EIT framework. Furthermore, it is expected that the physical properties of the OAM, the non-diffraction properties of the Bessel beam, and/or the acceleration properties of the Airy beam will open new opportunities under the EIT framework
In MIMO communications, information about the transmitted signal is conveyed to the receiver through fields and currents on the surface of the receive antenna array. However, this information can only be observed indirectly through the ports of the array. This raises fundamental information-theoretic questions: How much useful information is contained in the fields and currents on the surface of the receiver array? How much of this information is captured by the array ports? Do conventional arrays efficiently extract the information contained in their conducting surfaces? In this paper, we consider these questions in the context of a multiuser MIMO (MU-MIMO) uplink where users are separated by spatial beamforming at the receiver. Our main results can be summarized as follows: To quantify the information contained in the EM fields and currents on the surface of the receiving antenna array, we first introduce a new model, the surface receiver model. We then use this model to derive upper bounds on the spectral efficiency that can be approached with any location of M ports on the surface of the receiving antenna array. We denote this the surface modal bound. Furthermore, we also derive upper bound on the spectral efficiency approached with any number or location of ports on the receiver array. We call it the surface spectral efficiency. Finally, we apply the analytical results to a MU-MIMO uplink with an array of patch antennas at the receiver. The results suggests that the conventional arrays of single and dual-polarized patches fails to capture most of the information contained in the surface currents. The results further suggest ways to modify the number of antenna ports, together with the receiver front-end, to extract the information in the surface currents more efficiently.
Subject to the laws of classical physics -the science that governs the design of todays wireless communication systems -there is no need to match the radiation impedance of a receiver antenna to the impedance of the front-end electronics in order to effect communications. If we dispense with a transmission line and, instead, make the front-end electronics colocated with the antenna, then a high input-impedance preamplifier can measure the open-circuit voltage directly on the antenna port while drawing negligible power. Neither Friis’ concept of noise figure, nor Shannon information theory, nor electronics technology dictates that we must extract power from an antenna. Classical physics appears not to provide a lower bound on the energy that must be extracted from the antenna for every bit of received information.
Ambitions for the next generation of wireless communication include high data rates, low latency, ubiquitous access, ensuring sustainability (in terms of consumption of energy and natural resources), all while maintaining a reasonable level of implementation complexity. Achieving these goals necessitates reforms in cellular networks, specifically in the physical layer and antenna design. The deployment of transmissive metasurfaces at basestations (BSs) presents an appealing solution, enabling beamforming in the radiated wave domain, minimizing the need for energy-hungry RF chains. Among various metasurface-based antenna designs, we propose using Huygens’ metasurface-based antennas (HMAs) at BSs. Huygens’ metasurfaces offer an attractive solution for antennas because, by utilizing Huygens’ equivalence principle, they allow independent control over both the amplitude and phase of the transmitted electromagnetic wave. In this paper, we investigate the fundamental limits of HMAs in wireless networks by integrating electromagnetic theory and information theory within a unified analytical framework. Specifically, we model the unique electromagnetic characteristics of HMAs and incorporate them into an information-theoretic optimization framework to determine their maximum achievable sum rate. By formulating an optimization problem that captures the impact of HMA’s hardware constraints and electromagnetic properties, we quantify the channel capacity of HMA-assisted systems. We then compare the performance of HMAs against phased arrays and other metasurface-based antennas in both rich scattering and realistic 3GPP channels, highlighting their potential in improving spectral and energy efficiency.