The Structure and Geometry of Complex Networks: A Hyperbolic Geometrical Perspective
Complex network structures emerge nowadays in almost every natural and artificial aspect of life, e.g., engineering, biology, sociology, economy, politics, etc. Identifying and properly analyzing such structure in naturally emerging processes on one hand, or accurately selecting the appropriate structure for modeling phenomena in human-induced applications on the other, is essential for correctly capturing the observed behavior and obtaining accurate tools for controlling and optimizing applications. The tutorial aspires to provide foundational and more applied knowledge on the structure and essential topological properties of complex social networking structures, providing a solid basis for identifying and utilizing the salient properties of such network structure in diverse
Initially, the tutorial will introduce the audience to the different types of complex networks and their structure. Then more focus will be given on social (hierarchical) structure, by examining the mathematical foundations of the topology (geometry) of emerging social structure in different applications (e.g., social, biological, financial, ecological, computer networks, etc.). These systems can be represented as graphs embedded in an underlying metric space where distances determine the likelihood of interactions and condensate the different intrinsic attributes determining how similar the elements of the system are. The maps (embeddings) can be used for the analysis of the structure in various contexts, e.g., community detection, classification, visualization, prediction and inference. Classical approaches use Euclidean geometry for this task. However, the peculiarities of the architecture of complex networks – in particular the small-world property and high levels of heterogeneity in terms of number of connections per node – make Euclidean embeddings to be inaccurate, unless the dimension is extremely high. This can be alleviated by shifting from Euclidean to Hyperbolic geometry. Indeed, hyperbolic geometry has already build-in the small-world property and node heterogeneity so that complex networks can be embedded with minimal distortion in low dimensional hyperbolic spaces.
The tutorial will present the foundations of these findings providing and then present tangible applications of using hyperbolic embeddings of networks in specific applications including computer networks, social analysis, biological networks and information diffusion, thus creating a solid foundation for researchers and professionals wishing to study and exploit the essential topological properties of social structure in every application it emerges. The ultimate goal will be to provide the audience the necessary mathematical background and an illuminating applications overview, in order to stimulate further initiatives in complex network analysis and optimization.
Name: Dr. Vasileios Karyotis, Member IEEE
Affiliation: Department of Informatics, Ionian University
Dr. Vasileios Karyotis (S’03-GS’07-M’11) is currently an Associate Professor with the Dept. of Informatics at Ionian University, Corfu, Greece. Since 2009 he is a research associate with the NETMODE Lab of NTUA, Greece, and since October 2017 he is an adjunct lecturer with the Hellenic Open University, Greece. He received a Diploma in Electrical & Computer Engineering (ECE) from the National Technical University of Athens (NTUA), Greece, in 2004, an MSc. in Electrical Engineering from the University of Pennsylvania (UPenn), USA, in 2005, and a Ph.D. in ECE from NTUA, Greece, in 2009. His research interests focus on the modeling and analysis of complex networks, with emphasis on resource allocation, malware propagation, and modeling/control of information diffusion. He has co-authored the books “Evolutionary Dynamics of Complex Communications Networks” and “Malware Diffusion Models for Modern Complex Networks: Theory and Applications”. He was awarded a fellowship from the Dept. of ESE of UPenn (2004-2005), and one of two departmental fellowships for exceptional graduate students from the School of ECE of NTUA (2007-2009). He also received a best paper award in ICT 2016. He is a member of the IEEE since 2003 and of the Technical Chamber of Greece since 2004.
Open RAN: The next step in the RAN architecture evolution
Open RAN is currently one of the hottest topics in the area of wireless mobile communications. In this tutorial, an overview of the current 3GPP-based RAN architecture is first provided, covering different deployment options such as D-RAN, C-RAN, and V-RAN. Next, the Open RAN concept is explained, focusing on the O-RAN Alliance standards. The O-RAN presentation covers the architecture, interfaces, software and hardware aspects, and explains how O-RAN is expected to foster competitiveness, as well as innovation through the exploitation of AI/ML solutions. Finally, the tutorial summarizes the current O-RAN deployment status, highlighting also potential O-RAN challenges and threats.
LoRa and LoRaWAN in the Industrial IoT domain
LoRa is a low cost proprietary wireless technology which can achieve long ranges, low power, and remarkable resilience to Doppler effects and cross-technology interference. LoRaWAN is an open standard maintained by the LoRa Alliance which sits on top of LoRa PHY and provides MAC and Link layer services. In this tutorial, we will give an overview of LoRa and LoRaWAN technologies and we will discuss how they fit in the Industrial Internet of Things (IIoT) domain. Their limitations, challenges as well as proposed solutions with regard to the IIoT needs will be explored.
Dr. Dimitrios Zorbas is an Assistant Professor at Nazarbayev University in Kazakhstan. He holds a PhD in Computer Science from the University of Piraeus in Greece. He has worked as post doctoral researcher at Inria Lille – Nord Europe and at University of La Rochelle in France. He was also a researcher at Tyndall National Institute – University College Cork in Ireland after receiving a Marie Curie fellowship. He is author of more than 50 peer-reviewed publications in the area of wireless communications and distributed computing. He has worked in several national as well as FP7 and H2020 projects. He is member of the IEEE.
Recent Developments in Channel Modeling and Challenges in post 5G Communications
Accurate channel characterisation and modeling has been constituting a core priority in wireless communications. This has led to the proposition of several accurate and versatile models that account for the multipath fading, shadowing and composite fading effects in realistic radio communications scenarios. However, 5G communications are based on mm-wave frequencies whereas 6G communications are envisioned to operate in the THz band. Also, optical wireless communications have been largely explored in numerous practical scenarios of interests. In this context, this tutorial presents the latest contributions in channel modeling and highlights the generality of certain models in different frequency bands. Also, the involved challenges and peculiarities in each case will be discussed along with some open research problems for future investigations.
Paschalis C. Sofotasios received the MEng degree from Newcastle University, the MSc degree from the University of Surrey and the PhD degree from the University of Leeds. He has held academic positions at the University of Leeds, University of California at Los Angeles, Tampere University of Technology, Aristotle University of Thessaloniki and the Khalifa University, where he currently serves as an Associate Professor at the Department of Electrical Engineering and Computer Science. His research interests are concerned with physical layer digital and optical wireless communications, with emphasis on wireless communications theory. He is a Senior Member IEEE and has received numerous scholarships and awards including Exemplary Reviewer Awards from the IEEE COMMUNICATIONS LETTERS, in 2012, and the IEEE TRANSACTIONS ON COMMUNICATIONS, in 2015 and 2016. He has served as Associate Editor for IEEE Communications Letters, a TPC Chair for IEEE Globecom 2020 and has been the co-recipient of the Best Paper Award at ICUFN 2013.