Invited Keynote Speakers

Prof. Dominique Schreurs, KU Leuven, Belgium

Title: Analysis of Channel Hardening for SWIPT using Measured Massive MIMO Channels
Abstract: The performance of simultaneous wireless information and power transfer (SWIPT) is often inhibited by high pathloss and multi-path fading. The massive multiple-input-multipleoutput (MIMO) system is seen as an effective technique to overcome the wireless channel distortion. This work analyzes how massive MIMO enables channel hardening and thus influences the optimal SWIPT transmission strategy. This study focuses on the MISO case (i.e., 64-antenna transmitter and a single receiver node) and is done based on a non-linear energy harvesting model and measured channel state nformation (CSI). The results confirm that massive MIMO hardens the channel which makes frequency domain pre-equalization unnecessary for both nonline- of-sight (NLoS) and line-of-sight (LoS) channels. The impact is, as expected, more noticeable in NLoS scenario. We show that the array gain introduced by the 64-antenna transmitter using a 15-tone multi-sine signal, can improve the normalized power conversion efficiency (PCE) by more than 80%, and the channel capacity by more than 2 times, for both NLoS and LoS channels.

Prof. Changzhi Li, Texas Tech University, USA

Title: Portable Microwave Radar Systems for Life Activity Sensing and Human Localization
Abstract:Portable biomedical radar systems with embedded control and signal processing have the potential to improve the quality of service in many healthcare, human-computer interface, and internet of things (IoT) applications. This paper provides an overview of our recent research activities in developing smart microwave radar sensors aided with advanced technologies such as digital/RF beamforming, synthetic aperture radar (SAR), inverse synthetic aperture radar (ISAR), and machine learning. Several radar systems operating in interferometry, Doppler, frequency-modulated continuous-wave (FMCW), and frequency shift keying (FSK) modes at 5.8 GHz, 24 GHz, and 120 GHz will be discussed. Case studies will be presented on bioengineering applications including sleep study, fall detection, human-aware indoor localization, and anomaly detection.

Prof. Dr. Felip Riera-Palou, Technical University of Catalonia,  Spain

Title: Trade-offs in Cell-free Massive MIMO Networks
Abstract: Cell-free Massive MIMO (CF-M-MIMO) networks have recently emerged as one of the most promising architectural solutions to satisfy the requirements of future networks (i.e., beyond 5G, 6G). The CFM- MIMO paradigm advocates for the irregular deployment of a large number of access points (AP) throughout the network coverage area, all connected to a central processing unit (CPU), with the aim of bringing the radio access frontend closer to the users. Indeed, the cell-free topology can be interpreted as a fully distributed implementation of the Massive MIMO (M-MIMO) technology that is currently permeating the rollout of 5G. Interestingly, the large body of theoretical results derived for M-MIMO over the last decade can be recast in the CF-M-MIMO framework yet the distributed nature of the system needs to be carefully factored in. This paper aims at highlighting the different trade-offs affecting various performance metrics in CF-M-MIMO networks, in particular, the influence and consequences of different precoding strategies, power allocation techniques, AP-CPU functional splits and fronthaul designs will be discussed and assessed.

Prof. Giovanni Crupi, University of Messina, Italy

Title: A Comprehensive and Critical Overview of the Kink Effect in S22 for HEMT Technology
Abstract: The purpose of this invited contribution is to give readers comprehensive knowledge, critical understanding, and new insights into the kink effect in the output reflection coefficient (S22) of field-effect transistors (FETs). To accomplish this challenging goal, we report a measurement-based analysis, focusing on the high-electron-mobility transistor (HEMT) technology as a case study. The kink effect is investigated over a wide range of operating conditions, such as bias point, ambient temperature, device size, and semiconductor technology. The origin of the kink effect and its dependency on the operating condition are analyzed by using an equivalent-circuit model. The achieved findings represent a powerful know-how to entitle microwave engineers to take properly the kink effect into account in fabrication, modeling, and design phases.

Prof. Nicola Donato, University of Messina, Italy

Title: Resonant devices and gas sensing: from low frequencies to microwave range.
Abstract:
The research of new typologies of sensors with high performance and low power consumption features is today one of the areas of greatest interest in the market. In particular, low power sensors are mandatory in wireless sensors networks to achieve the right balance between sensing performance and battery lifetime. In such a frame relatively new category of sensors can be represented by resonant devices. Resonant sensors are one of the key issue in many industrial applications, operating in a wide frequency range roughly spanning from kHz to GHz. By considering resonance frequency values from few to hundreds MHz, (Bulk and Surface) acoustic wave sensors are extremely versatile devices that are just beginning to achieve their commercial potential. Acoustic wave sensors are so called because of their detection mechanism, involving mechanical, or acoustic, waves. As the acoustic wave propagates through/on the surface of the material, any changes to the characteristics of the propagation path affect the velocity and/or amplitude of the wave. Changes in velocity can be monitored by measuring either the frequency or phase characteristics of the sensor and they can then be correlated to the corresponding chemical and/or physical quantity being measured.  By increasing the frequency value, microwave resonant sensors are showing interesting properties in terms of fast response, low power consumption, fully compatibility with wireless technologies and room temperature operating value. The two main output parameters of such devices are the resonance frequency value and the quality factor, then their variations when exposed to several gas target concentrations. These devices can be included in conductometric transducers category, with a slightly different mechanism of transduction than traditional ones, because, in this case, change of permittivity of sensitive layer is involved in the transduction process. Therefore, the adsorption of molecules on the surface of the sensing layer and correspondent variation of the permittivity is a phenomenon which operates only in the second order as a conductometric transducer. In particular, the possibility to balance between the sensing material properties and the resonator configuration for design of the sensor make them very versatile for different applications. Microstrip technology, widely employed in the design of microwave resonators and filters, can be successfully used in the development of such sensors. This work exploits the design and characterization of BAW, SAW and microwave resonant gas sensors developed at the University of Messina laboratories by describing several case studies and related application examples.

Prof. Zoran Bojković, University of Belgrade, Serbia

Title: Influences of Weighting Techniques on TOPSIS-based Network Slcce
Abstract: Cell-free Massive MIMO (CF-M-MIMO) networks have recentlyemerged as one of the most promising architectural solutions to satisfy the requirements of future networks (i.e., beyond 5G, 6G). The CFM- MIMO paradigm advocates for the irregular deployment of a large number of access points (AP) throughout the network coverage area, all connected to a central processing unit (CPU), with the aim of bringing the radio access frontend closer to the users. Indeed, the cell-free topology can be interpreted as a fully distributed implementation of the Massive MIMO (M-MIMO) technology that is currently permeating the rollout of 5G. Interestingly, the large body of theoretical results derived for M-MIMO over the last decade can be recast in the CF-M-MIMO framework yet the distributed nature of the system needs to be carefully factored in. This paper aims at highlighting the different trade-offs affecting various performance metrics in CF-M-MIMO networks, in particular, the influence and consequences of different precoding strategies, power allocation techniques, AP-CPU functional splits and fronthaul designs will be discussed and assessed.

Prof. Dejan Drajić, University of Belgrade, Serbia

Title: User Engagement for Large Scale Pilots in the Internet of Things
Abstract: With an expected 50 billion connected devices by 2020, the Internet of Things (IoT) will reshape our environment with great economic opportunities. However, the IoT market evolution will depend directly on the end-user adoption, so it necessary to support the Large Scale Pilots (LSPs) in order to actively engage end-users in the large scale pilot design, deployment and assessment. In this paper we are presenting end-user engagement methodologies, including co-creative workshops, crowdsourcing, Living Labs, and developed online tools and resources for end-user engagement, crowdsourcing and personal data protection.

Prof. Bartomeu Alorda Ladaria, Universitat de les Illes Balears (UIB), Spain

Title: Main regularities and health risks from exposure to non-thermal radiofrequency radiation

Prof. Igor Belyaev, Slovak Academy of Sciences, Slovakia