Massive MIMO is a Reality -- What is Next? Five Promising Research Directions for Antenna Arrays

Massive MIMO (multiple-input multiple-output) is no longer a "wild" or "promising" concept for future cellular networks - in 2018 it became a reality. Base stations (BSs) with 64 fully digital transceiver chains were commercially deployed in several countries, the key ingredients of Massive MIMO have made it into the 5G standard, the signal processing methods required to achieve unprecedented spectral efficiency have been developed, and the limitation due to pilot contamination has been resolved. Even the development of fully digital Massive MIMO arrays for mmWave frequencies - once viewed prohibitively complicated and costly - is well underway. In a few years, Massive MIMO with fully digital transceivers will be a mainstream feature at both sub-6 GHz and mmWave frequencies. In this paper, we explain how the first chapter of the Massive MIMO research saga has come to an end, while the story has just begun. The coming wide-scale deployment of BSs with massive antenna arrays opens the door to a brand new world where spatial processing capabilities are omnipresent. In addition to mobile broadband services, the antennas can be used for other communication applications, such as low-power machine-type or ultra-reliable communications, as well as non-communication applications such as radar, sensing and positioning. We outline five new Massive MIMO related research directions: Extremely large aperture arrays, Holographic Massive MIMO, Six-dimensional positioning, Large-scale MIMO radar, and Intelligent Massive MIMO.Comment: 20 pages, 9 figures, submitted to Digital Signal Processin

A Tutorial on Environment-Aware Communications via Channel Knowledge Map for 6G

Sixth-generation (6G) mobile communication networks are expected to have dense infrastructures, large-dimensional channels, cost-effective hardware, diversified positioning methods, and enhanced intelligence. Such trends bring both new challenges and opportunities for the practical design of 6G. On one hand, acquiring channel state information (CSI) in real time for all wireless links becomes quite challenging in 6G. On the other hand, there would be numerous data sources in 6G containing high-quality location-tagged channel data, making it possible to better learn the local wireless environment. By exploiting such new opportunities and for tackling the CSI acquisition challenge, there is a promising paradigm shift from the conventional environment-unaware communications to the new environment-aware communications based on the novel approach of channel knowledge map (CKM). This article aims to provide a comprehensive tutorial overview on environment-aware communications enabled by CKM to fully harness its benefits for 6G. First, the basic concept of CKM is presented, and a comparison of CKM with various existing channel inference techniques is discussed. Next, the main techniques for CKM construction are discussed, including both the model-free and model-assisted approaches. Furthermore, a general framework is presented for the utilization of CKM to achieve environment-aware communications, followed by some typical CKM-aided communication scenarios. Finally, important open problems in CKM research are highlighted and potential solutions are discussed to inspire future work

Reconfigurable Intelligent Surfaces: A signal processing perspective with wireless applications

Antenna array technology enables the directional transmission and reception of wireless signals for communication, localization, and sensing purposes. The signal processing algorithms that underpin it began to be developed several decades ago [1], but it was with the deployment of 5G wireless mobile networks that the technology became mainstream [2]. The number of antenna elements in the arrays of 5G base stations (BSs) and user devices can be measured on the order of hundreds and tens, respectively. As networks shift toward using higher-frequency bands, more antennas fit into a given aperture. For communication purposes, the arrays are harnessed to form beams in desired directions to improve the signal-to-noise ratio (SNR) and multiplex data signals in the spatial domain (to one or multiple devices) and to suppress interference by spatial filtering [2]. For localization purposes, these arrays are employed to maintain the SNR when operating across wider bandwidths, for angle-of-arrival estimation, and to separate multiple sources and scatterers [3]. The practical use of these features requires that each antenna array is equipped with well-designed signal processing algorithms

Implementation of improvements of the Wi-Fi network of the RTBF and implementation of a Wi-Fi network for an “intelligent” building

Este Trabajo de Fin de Grado se ha realizado dentro de la Radio Televisión Belga Francófona (RTBF) en Bruselas. El objetivo de este proyecto es el diseño de una red Wi-Fi completamente confiable y de alto rendimiento para una de sus localizaciones. Para empezar, se completaron un estudio teórico y mediciones reales. La comparación entre el estudio teórico y práctico no estaba concluyente por lo que las predicciones teóricas se han modificado para corresponder a la realidad. Finalmente, la RTBF está construyendo un nuevo edificio en 2022 para el cual un estudio predictivo teórico se ha hecho para proporcionar una cantidad de puntos de accesos necesarios para una cobertura completa.This End-of-Grade work have been done inside the Francophone Belgian Radio-Television (RTBF) in Brussels. The goal of this Project is to design a fully reliable and performant Wi-Fi network for one of their localization. To begin with, a theorical study and real-life measurements were completed. The comparasion between the theorical and practical study was not concluding so the theorical predictions have been changed to correspond to reality. Finally, the RTBF is constructing a new building in 2022 for which a theorical predictive study have been done to provide the number of needed access points for a complete coverage.Grado en Ingeniería en Tecnologías de Telecomunicació

Design of a Drone-Flight-Enabled Wireless Isolation Chamber

The next wave of drone applications is moving from repeatable, single-drone activities such as evaluating propagation environments to team-based, multi-drone objectives such as drone-based emergency services. In parallel, testbeds have sought to evaluate emerging concepts such as highly-directional and distributed wireless communications. However, there is a lack of intersection between the two works to characterize the impact of the drone body, antenna placement, swarm topologies, and multi-dimensional connectivity needs that require in-flight experimentation with a surrounding testbed infrastructure. In this work, we design a drone-flight-enabled isolation chamber to capture complex spatial wireless channel relationships that drone links experience as applications scale from single-drone to swarm-level networks within a shared three-dimensional space. Driven by the challenges of outdoor experimentation, we identify the need for a highly-controlled indoor environment where external factors can be mitigated. To do so, we first build an open-source drone platform to provide programmable control with visibility into the internal flight control system and sensors enabling specialized coordination and accurate repeatable positioning within the isolated environment. We then design a wireless data acquisition system and integrate distributed software defined radios (SDRs) in order to inspect multi-dimensional wireless behavior from the surrounding area. Finally, we achieve and demonstrate the value of measurement perspectives from diverse altitudes and spatial locations with the same notion of time

MIMO Systems

In recent years, it was realized that the MIMO communication systems seems to be inevitable in accelerated evolution of high data rates applications due to their potential to dramatically increase the spectral efficiency and simultaneously sending individual information to the corresponding users in wireless systems. This book, intends to provide highlights of the current research topics in the field of MIMO system, to offer a snapshot of the recent advances and major issues faced today by the researchers in the MIMO related areas. The book is written by specialists working in universities and research centers all over the world to cover the fundamental principles and main advanced topics on high data rates wireless communications systems over MIMO channels. Moreover, the book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity