Showing papers by "Thomas L. Marzetta published in 2022"
25 Apr 2022
TL;DR: In this article , the beamforming vector of super-directive arrays was derived based on a novel coupling matrix-enabled method, and an approach to obtain the coupling matrix, which is derived by the spherical wave expansion method and active element pattern.
Abstract: In most multiple-input multiple-output (MIMO) communication systems, e.g., Massive MIMO, the antenna spacing is generally no less than half a wavelength. It helps to reduce the mutual coupling and therefore facilitate the system design. The maximum array gain is the number of antennas in this settings. However, when the antenna spacing is made very small, the array gain of a compact array can be proportional to the square of the number of antennas - a value much larger than the traditional array. To achieve this so-called "superdirectivity" however, the calculation of the excitation coefficients (beamforming vector) is known to be a challenging problem. In this paper, we derive the beamforming vector of superdirective arrays based on a novel coupling matrix-enabled method. We also propose an approach to obtain the coupling matrix, which is derived by the spherical wave expansion method and active element pattern. The full-wave electromagnetic simulations are conducted to validate the effectiveness of our proposed method. Simulation results show that when the beamforming vector obtained by our method is applied, the directivity of the designed dipole antenna array has a good agreement with the theoretical values.
6 citations
02 May 2022
TL;DR: This model allows establishing that line-of-sight spatial multiplexing can take place via reflection off an electrically large surface, a situation of high interest for mmWave and terahertz frequencies.
Abstract: We provide a deterministic channel model for a scenario where wireless connectivity is established through a reflection from a planar smooth surface of an infinite extent. The developed model is rigorously built upon the physics of wave propagation, and is as precise as tight are the unboundedness and smoothness assumptions on the surface. This model allows establishing that line-of-sight spatial multiplexing can take place via reflection off an electrically large surface, a situation of high interest for mmWave and terahertz frequencies.
3 citations
04 Dec 2022
TL;DR: In this article , the authors studied the feasibility of using thermal conduction to communicate information and showed that the thermal channel's effective bandwidth is constrained by the total power since a water-filling algorithm determines a cutoff frequency.
Abstract: While the heat equation has been extensively studied, heat conduction has not been studied as a means of communication until recently. Recent literature focusing on covert channels shows the feasibility of using thermal conduction to communicate information. Since heat conduction is modelled by a linear partial differential equation, it can be analyzed as a linear system with an input heat source and output temperature distribution. The magnitude of the thermal channel's frequency response is an exponentially decaying function of frequency. The thermal channel's capacity increases when the total power increases, similar to typical communication based on electromagnetic waves. Uniquely however, the thermal channel's effective bandwidth is constrained by the total power since a water-filling algorithm determines a cutoff frequency. Additionally, the quadratic nature of the heat equation presents a novel quadratic scaling of the channel capacity. Scaling space by a factor of 2 and time by 4 improves the channel capacity by a factor of 4. This implies that scaling space down from centimeter to micrometer domain improves the channel capacity by a factor of 108• The thermal channel presents various novel qualities and a possible exciting application for intra-chip communication.
04 Dec 2022
TL;DR: In this paper , the authors proposed a space-time noise model Rayleigh-Jeans-Clarke (RJC) for MIMO communications in a copper box, which is based on the assumption that every orthogonal normal mode has an independent random amplitude such that the expected energies of the modes are equal and proportional to absolute temperature.
Abstract: A resonant electromagnetic cavity - effectively the interior of a copper box - constitutes a highly favorable propa-gation environment for MIMO communications. A fundamental limitation on wireless communication within the box is thermal noise. Under conditions of thermal equilibrium the Equipartition Theorem of classical statistical mechanics states that every orthogonal normal mode has an independent random amplitude such that the expected energies of the modes are equal and proportional to absolute temperature. Collectively the randomly excited modes constitute a space-time stochastic process, station-ary in time but non-stationary in space because of boundary conditions. As the linear dimensions of the box grow relative to a wavelength the process is asymptotically stationary. At each temporal frequency the wavenumber spectral density is identical to that of the Clarke model - a superposition of random plane waves having no preferred direction of propagation. At a single point in space the spectral density is proportional to the square of temporal frequency - the Rayleigh-Jeans spectrum. We call our space-time noise model Rayleigh-Jeans-Clarke (RJC).
TL;DR: In this article , the authors explore how new advances in information theory can impact future communication systems, including multiple access, including access by a massive number of devices, multi-hop, large antenna arrays, communication security, and timeliness of information.
Abstract: Information theory, starting with Shannon’s groundbreaking work, has fundamentally shaped the way communication systems are designed and operated. Information theoretic principles form the underpinnings of modern communication networks. This issue explores how new advances in information theory can impact future communication systems. Several papers address issues at the heart of next generation wireless and wired networks: Multiple access, including access by a massive number of devices, multi-hop, large antenna arrays, communication security, and timeliness of information. Others consider new applications such as joint communication and sensing, communication for learning and inference, wireless imaging, and new storage mediums such as DNA, thereby providing the information theoretic foundations of modalities beyond human-to-human communications.