Digital Communications and Networks

Objective

The objective of the course is a comprehensive presentation of the analysis and design techniques of wireless and satellite communication links. The course includes two sections. In the first section we attempt a review of fundamental concepts of antenna technology and electromagnetic propagation. An analytic description of propagation aspects in current wireless communication systems is given for the mostly used frequency bands. Propagation mechanisms and prediction models are provided for successful design of fixed wireless access systems. We analyze international standards and recommendations (ITU-R) for the efficient design of wireless links providing the critical metrics and quality parameters. The section closes with the analysis of antenna arrays, the methods used for array signal processing and typical applications of optimum beam formers. The second section deals with the review of Satellite communications networks technology providing the current state of structural blocks of these networks, discussing the multiple access techniques and network topologies used. Typical examples are given for VSAT networks and the design of satellite links.

Course Contents

• Electromagnetic waves and wave polarization. Antennas as radiators and several antenna types. Antenna parameters, radiation patterns, directive gain, power gain, effective aperture, effective length.
• Electromagnetic wave propagation mechanisms: Reflection and refraction, propagation in the troposphere.
• Electromagnetic wave propagation mechanisms: Scattering, diffraction, propagation models. Quality parameters for effective link design.
• Analysis of antenna arrays. Types, topologies, geometry of arrays. Fundamental parameters for antenna array system representation. Narrowband assumption. Basic structures for beamforming.
• Array signal processing. Uniform linear arrays. Visible region, antenna array weighting-feeding. Radiation patterns parameters and beamsteering.
• Statistical antenna array signal processing. Narrowband processing, conventional beam former, null steering beam former. Wiener filters and digital beamforming techniques for optimum beam formers.
• The development of satellite communication networks. Review of services. Geometrical parameters and orbits (GEO, LEO, MEO, HEO). Satellite transponders and basic structures. Antennas on board the satellite.
• Noise in satellite communications (antennas and receivers). Receiver architectures. Non-linearities in satellite high power amplifiers. Quality parameters and performance evaluation criteria for clear sky and under rain conditions.
• Transmission techniques and satellite link design. Design examples for fixed as well as mobile communication systems.
• Multiple access techniques for satellite communication networks (TDMA, FDMA, CDMA). VSAT Networks, topologies and architectures.

Objective

The objective of this course is to familiarize students with the main principles and concepts of mobile applications programming. The focus is on the Android development framework which is used in the great majority of modern smartphone and tablet devices, featuring powerful processing, a touch screen, and a variety of sensors including a GPS unit. Furthermore, the course addresses network programming techniques for the implementation of network applications with the use of Java. The goal of this lab/course is to demystify the Android development framework towards developing modern applications for mobile devices. Working with Android applications, students will gain experience with a modern technology in the fast moving market segment of computationally powerful Internet-enabled smartphones and similar devices.

Course Contents

• Lecture 1: Overview of device and operating system architecture for modern smartphones. Introduction to the Android development platform.
• Lecture 2: Introduction to the Android development framework and tools for mobile application development. Android application model and basic application elements. Android SDK overview. Getting familiar with the Android emulator. Android programming synopsis. Application development using the Android SDK and the Eclipse framework.
• Lecture 3: Creating User Interfaces: Using XML-based layouts (comparison with java powered layouts), basic widgets (labels, check boxes, buttons, input boxes, etc), containers (widget collections), input method framework, drop-down menus, fonts, etc. Layout methods. Handling multiple screen sizes and resolutions.
• Lecture 4: Android application components and component interaction: Android Activities and Android Intents.
• Lecture 5: Using data and databases in Android.
• Lecture 6: Creating map-based activities. The Google Maps Application Programming Interface (API) and the MapView class.
• Lecture 7: Location Based Services.
• Lecture 8: Cases studies – Lab development: Development of Android Applications.
• Lecture 9: Cases studies – Lab development: Development of Android Applications.
• Lecture 10: Cases studies – Lab development: Development of Android Applications.

Objective

The objective of this course is to introduce the students to the practical design, analysis and performance evaluation of wireless communication systems, using the software defined radio (SDR) technology. During the course, the students will have the opportunity to experiment with signals that are used in today’s wireless communication systems, such as LTE and Wi-Fi, by designing the corresponding transmitter and receiver digital processing chains. The signal generation and analysis blocks will be designed using software, whereas the transmission/reception will be realized using SDR hardware (digitizer boards) and general purpose computing platforms (linux-based desktop hosts).

The course consists of three parts. During the first part the students are familiarized with the SDR concept, the use of SDR hardware (Ettus USRP boards) and software management tools, as well as develop a baseline SISO-OFDM (Single-antenna Orthogonal Frequency Division Multiplexing) transceiver. In the second part, the students develop more complex blocks, extending the baseline transceiver in order to support MIMO (multi-antenna) techniques. In the third and final part the students are experimenting with existing open source wireless communication system implementations (e.g. OpenAirInterface), creating and testing an experimental private 4G network.

Course Contents

• Part 1:
  • Introduction to Software Defined Radio (SDR),
    • SDR Architectures (Ideal, Practical etc.,) SDR systems, SDR transceiver components.
    • Introduction to the SDR hardware and management software used in the course
    • SDR technology applications: Cognitive Radios and Dynamic Spectrum Sharing.
  • Signals / Spectrum Analysis and Detection
    • Generation of basic signals (sine, square pulse) and implementation of basic signal processing procedures (filtering with sampling rate conversion
    • Basic principles of detection and estimation theory, statistical signal characterization, maximum likelihood detector/Bayesian, etc.
    • Energy detector, matched filter, filter-bank detector
  • Implementation of a baseline QPSK transceiver using Software
    • Familiarization with software code tools (MATLAB or C++).
    • Development of OFDM modulator and demodulator
    • Pilot and preamble insertion – Synchronization
    • Frequency offset estimation
    • Channel estimation and equalization
    • Over-the-air experimentation using SDR hardware – Performance Evaluation.
• Part 2:
  • Baseline transceiver extension and experimentation with MIMO techniques
    • Implementation of MIMO in SDR hardware.
  • Receiver Diversity Techniques
    • Development of selection diversity
    • Development of Maximum Ratio Combining (MRC).
  • Transmitter Diversity Techniques
    • Space Time Block Coding using the Alamouti method.
• Part 3:
  • Development of a 4G experimental network using existing open source software code (e.g. OpenAirInterface)
  • Familiarization with 4G systems. Experimentation with practical resources allocation methods.

Objective

The course “Network Design and Management” aims at teaching the contemporary methodologies and technologies in the areas of design and management of computer networks. In this context, network design problems are presented and properly formulated, whereas algorithms for their solution are presented, developed and validated using commercial software packages. Furthermore, the fundaments of computer network management, with respect to architectural, functional, information and communication models, are presented, thoroughly discussed and validated. Last but not least, recent advancements and future trends in networks and their management are presented and analyzed. The course is comprised of both theoretical lectures and specialised laboratory and programming exercises and platform demonstrations.

Course Contents

• Introduction: Course/lectures overview. Overview of computer networks, Wireless/Fixed access. Core networks. High level presentation of design, management and optimization problems.
• Advanced network design problems: Advanced design problems in fixed/wireless access networks and core networks. Topology and Resource assignment problems (Routing & Wavelength, Virtual Machines Placement, Spectrum/Power Assignment, Traffic Engineering, Mobile Offloading) in optical networks, 4G/5G Small Cell/HetNets, Radio-over-Fiber Networks and Data Centers. Mathematical modeling (Energy Efficiency, Cost Reduction).
• Methods and algorithms for solving computer network design problems: local search, greedy, (meta-)heuristics, simulated annealing, genetic algorithms, taboo search, neural networks, bio-inspired and learning techniques. Application to and solution of the above design problems. Programming exercises.
• Introduction to network management: Configuration, Fault, Accounting, Performance and Security management functions – (CFAPS). Management layers, (element, network, service, business), manager(s), agents, network management architectures and standards. The internet management model, Simple Network Management Protocol (SNMP) protocol, Management Information Base (MIB), Structure of Management Information (SMI)/Abstract Syntax Notation.1 (ASN.1) languages. The Netconf protocol, YANG information model.
• MIB design, processing and development: Reading and processing of MIB contents. Introduction to well established MIBs (MIB-II, RFC 1213). Focus on system, interfaces, IP and TCP groups. Monitoring and configuration of MIB parameters based on SNMP. Configuration, performance and fault management functions. Application of theory in lab network infrastructure (servers, host PCs, switches etc.) using open source tools, lab exercises and analysis of results.
• Design and development of network management applications: Development of management applications particularly for performance and fault management. Usage of scripts, high level programming languages and open source tools and libraries. Programming and lab exercises, derivation and analysis of results.
• Network monitoring techniques and tools: Packet inspection, Protocol analysis. Traffic monitoring and analysis. Active/Passive monitoring. Network monitoring tools (ping, Traceroute, TCPdump, MRTG, IPFIX/NetFlow, HP Openview, SNMPc, MRTG/PRTG, Nagios, OpenNMS). Event and alarm generation. Event/alarm correlation (Aggregation, Filtering, Masking, Root cause analysis, Τεχνικές Case-, Model-, Rule- Based Reasoning).
• Autonomic Network Management: Mechanisms self-management (self-configuration, self-optimization, self-healing), cognitive management, application of machine learning in network management. Policy-based management. Network governance. The case of 3GPP LTE Self-Organizing Networks (SΟΝ).
• Management of SDN networks: Introduction to Software Defined Networks (SDN). The OpenFlow protocol. Virtual Switches and SDN controllers. Network virtualization and SDN Applications. Network Function Virtualization.
• Management /Programming of SDN: Installation and configuration of SDNs using source tools (Openflow vSwitches, mininet, JAVA/Python based controllers). Lab exercises on networking management/programming and development of networks functions/applications.

Objective

This course aims to study broadband technologies and networks with particular emphasis on the most recent developments and technical advances for the next generation of networks (2030+). In the first part, broadband networks design requirements, capabilities and constraints are analyzed. In the second part, wireline and wireless broadband networks are addressed with specific focus on transceivers, baseband signal processing, physical layer procedures, multiple access, and network architecture aspects. In the third part, future technology trends and innovative design techniques are discussed, such as extreme MIMO, Reconfigurable Intelligent Surfaces, and mmWave and THz communications.

Course Contents

• Broadband communications: requirements and recent developments (ITU, 3GPP, IEEE standards).
• Broadband transmission fundamentals: capacity, spectral efficiency, connectivity, reliability, reconfigurability and intelligence.
• Spectrally efficient broadband access: modulation, coding, multiplexing, space-time processing, spread spectrum, cooperation, coordination and interference management.
• Digital Subscriber Line (ITU-T): baseband processing, network architecture, advanced features, ADSL2, VDSL, multi-user DSL.
• Next generation Ethernet (IEEE 802.3): baseband processing, physical layer techniques, MAC protocols, xGigabit Ethernet, crosstalk, Ethernet in the first mile.
• Optical networks design and architecture (ITU-T): fiber optics basics, Wavelength Division Multiplexing, Optical Transport Network.
• Broadband Local Wireless Access and future WiFi (IEEE 802.11): OFDM, multiuser MIMO, Random Access, Scheduled Access.
• Advanced radio technologies for 4G and 5G (3GPP): cooperative techniques, coordinated muti-point transmission, massive/network MIMO, user-centric architectures.
• Broadband access in future internet and 6G technology trends: ultra dense networks and cell-less architectures.
• Research topics in Broadband Wireless Access: extreme MIMO, Reconfigurable Intelligent Surfaces, mmWave and THz communications.

Bibliography

• W Stallings, “ Wireless Communication Networks and Systems ”, Pearson(2015).
• Rajiv Sivarajan, Kumar N. Ramaswami, “Optical Networks: A Practical Perspective (Morgan Kaufmann Series in Networking)”, Morgan Kaufmann, 2nd edition (2001).
• D. Tse, P. Viswanath, “Fundamentals of Wireless Communication”, Cambridge University Press (2005).
• T. S. Rappaport, “Wireless Communications: Principles and Practice” , Prentice-Hall, (2003).
• Bernhard H. Walke, Stefan Mangold, Lars Berlemann, “IEEE 802 Wireless Systems: Protocols, Multi-Hop Mesh/Relaying, Performance and Spectrum Coexistence”, Wiley (2006).
• A. Alexiou (editor), “5G Wireless Technologies”, IET, 2017.
• E. Bertin, N. Crespi, T. Magedanz, “Shaping Future 6G Networks: Needs, Impacts, and Technologies”, John Wiley & Sons Ltd (2022).

Objective

The objective of the course is the presentation of modern wireless communication networks architecture, technologies and techniques. The area of wireless communications and networks is one of the most dynamic areas in the ICT field. The course covers the wireless channel characteristics, multi-antenna techniques, radio resource planning and management, packet scheduling, mobility management, and novel design techniques of wireless networks. At the end of the course, the students will be able to analyze and evaluate main principles and planning design options for wireless communication networks.

Course Contents

• Categories of wireless communications networks. Coverage, services and performance requirements of wireless networks. Network examples. Duplexing techniques, multiple access techniques and random access. Fundamentals of cellular network design.
• Analytic and empirical propagation channel models for outdoor and indoor environments. Shadowing and lognormal distribution. Calculation of coverage range and percentage.
• Propagation environment, mechanisms and propagation phenomena. Fading, types of fading. Delay dispersion and frequency selectivity. Frequency dispersion and time selectivity. Direction dispersion and space selectivity.
• From SISO to MIMO. Multi-antenna techniques and gains for beyond 3G systems (applications in LTE and LTE-A networks).
• Case study: design of a of a cellular mobile communications system step-by-step (initial planning based on traffic requirements, area, equipment costs, frequency bands, etc.)
• Wireless resource management, handoff management, communication management, mobility management in mobile communication networks. Examples and exercises.
• Packet scheduling principles. Wireless packet scheduling algorithms. Scheduling algorithms in 3G and 4G.
• Mobility management protocols in wireless packet networks. IP mobility management. Examples and mobility management architectures in 3G and 4G.
• TCP protocol principles and problems in wireless networks. TCP protocol adaptation techniques for wireless links. Multipath TCP.
• Cloud computing and software defined networking in next generation wireless networks. Architectures and design options for Cloud Radio Access Network (CloudRAN), Network Function Virtualization (NFV), wireless SDN and Mobile Edge Computing (MEC) in 5G. Laboratory example of SDN network management in wireless networks.

The master thesis project is carried out under the supervision of one of the faculty members and involves – at a first stage – the identification of the research topic/ technological problem to be addressed and the research of literature for existing state-of-the-art. The output of the project, namely the description of the research area, the problem formulation, the solution definition and implementation and the illustration of results and final conclusions and recommendations, is presented in the master thesis.

The master thesis project aims to

• Extend the student’s academic skills, introduce them to a certain research area and potentially motivate them to continue their research work beyond the completion of their Master’s Degree. This may be achieved not only by exploiting particular skills and knowledge acquired from taught courses but also by enhancing their ability to tackle a novel research area and/or problem.
• Expand the student’s professional skills by developing/improving their ability to research, manage/organise information, think creatively, pursue innovation and report adequately the findings of their research.