Mobile Radio Channel Measurements for air-to-ground and non-conventional future applications

La tesi si suddivide in quattro parti: due iniziali di tipo compilativo e le altre due sperimentali. Nella prima parte vengono descritti gli UAVs: classificazioni e applicazioni da un punto di vista delle telecomunicazioni e della sicurezza; una seconda parte sempre compilativa, espone invece una panoramica sulle caratteristiche del canale Air-to-Ground e la possibilità di modelling attraverso diversi scenari. La terza parte rappresenta il corpo della tesi, in quanto presenta la descrizione di una campagna di misure condotta in ambiente industriale, fatta con due diversi setup di misure: onde mm e UWB. Dopo la presentazione dello scopo, vengono poi trattati gli esperimenti, descritto l'equipment ed estratte le conclusioni mostrando funzioni come il Power Angle Profile e la Risposta Impulsiva. L'ultimo capitolo tratta infine di una campagna da condurre in ambiente urbano, presentando però solo il piano di misure, in quanto i risultati saranno a breve disponibili

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

Multi-pair massive MIMO relay networks: power scaling laws and user scheduling strategy

This study studies a multi-pair massive multiple-input multiple-output (MIMO) relaying network, where multiple pairs of users are served by a single relay station with a large number of antennas, and the amplify-and-forward protocol and zero-forcing (ZF) beamforming are used at the relay. The authors investigate the ergodic achievable rates for the users and obtain tight approximations in closed form for finite number of antennas. The rate performance and power efficiency are studied based on the analytical results for asymptotic scenarios, and the effect of scaling factors of transmit powers for users and relay are discussed. The closed-form expressions enable us to determine the optimal user scheduling which maximizes the ergodic sum-rate for the selected pairs. A simplified user scheduling algorithm is proposed which greatly reduces the average complexity of the optimal use pair search without any rate loss. Moreover, the complexity reduction for the proposed algorithm increases nonlinearly with the increase of the number of user pairs, which indicates that the simplified scheduling algorithm has notable advantages when the number of users is increased. The tightness for the analytical approximations and the superiority of the proposed algorithm are verified by Monte-Carlo simulation results