Hybrid Free-Space Optical and Visible Light Communication Link

V součastnosti bezdrátové optické komunikace (optical wireless communication, OWC) získávají širokou pozornost jako vhodný doplněk ke komunikačním přenosům v rádiovém pásmu. OWC nabízejí několik výhod včetně větší šířky přenosového pásma, neregulovaného frekvenčního pásma či odolnosti vůči elektromagnetickému rušení. Tato práce se zabývá návrhem OWC systémů pro připojení koncových uživatelů. Samotná realizace spojení může být provedena za pomoci různých variant bezdrátových technologií, například pomocí OWC, kombinací různých OWC technologií nebo hybridním rádio-optickým spojem. Za účelem propojení tzv. poslední míle je analyzován optický bezvláknový spoj (free space optics, FSO). Tato práce se dále zabývá analýzou přenosových vlastností celo-optického více skokového spoje s důrazem na vliv atmosférických podmínek. V dnešní době mnoho uživatelů tráví čas ve vnitřních prostorech kanceláří či doma, kde komunikace ve viditelném spektru (visible light communication, VLC) poskytuje lepší přenosové parametry pokrytí než úzce směrové FSO. V rámci této práce byla odvozena a experimentálně ověřena závislost pro bitovou chybovost přesměrovaného (relaying) spoje ve VLC. Pro propojení poskytovatele datavých služeb s koncovým uživatelem může být výhodné zkombinovat více přenosových technologií. Proto je navržen a analyzovám systém pro překonání tzv. problému poslední míle a posledního metru kombinující hybridní FSO a VLC technologie.The field of optical wireless communications (OWC) has recently attracted significant attention as a complementary technology to radio frequency (RF). OWC systems offer several advantages including higher bandwidth, an unregulated spectrum, resistance to electromagnetic interference and a high order of reusability. The thesis focuses on the deployment and analyses of end-user interconnections using the OWC systems. Interconnection can be established by many wireless technologies, for instance, by a single OWC technology, a combination of OWC technologies, or by hybrid OWC/RF links. In order to establish last mile outdoor interconnection, a free-space optical (FSO) has to be investigated. In this thesis, the performance of all-optical multi-hop scenarios is analyzed under atmospheric conditions. However, nowadays, many end users spend much time in indoor environments where visible light communication (VLC) technology can provide better transmission parameters and, significantly, better coverage. An analytical description of bit error rate for relaying VLC schemes is derived and experimentally verified. Nonetheless, for the last mile, interconnection of a provider and end users (joint outdoor and indoor connection) can be advantageous when combining multiple technologies. Therefore, a hybrid FSO/VLC system is proposed and analyzed for the interconnection of the last mile and last meter bottleneck

Telecommunication Systems

This book is based on both industrial and academic research efforts in which a number of recent advancements and rare insights into telecommunication systems are well presented. The volume is organized into four parts: "Telecommunication Protocol, Optimization, and Security Frameworks", "Next-Generation Optical Access Technologies", "Convergence of Wireless-Optical Networks" and "Advanced Relay and Antenna Systems for Smart Networks." Chapters within these parts are self-contained and cross-referenced to facilitate further study

Modelling, Dimensioning and Optimization of 5G Communication Networks, Resources and Services

This reprint aims to collect state-of-the-art research contributions that address challenges in the emerging 5G networks design, dimensioning and optimization. Designing, dimensioning and optimization of communication networks resources and services have been an inseparable part of telecom network development. The latter must convey a large volume of traffic, providing service to traffic streams with highly differentiated requirements in terms of bit-rate and service time, required quality of service and quality of experience parameters. Such a communication infrastructure presents many important challenges, such as the study of necessary multi-layer cooperation, new protocols, performance evaluation of different network parts, low layer network design, network management and security issues, and new technologies in general, which will be discussed in this book

Enabling Technology in Optical Fiber Communications: From Device, System to Networking

This book explores the enabling technology in optical fiber communications. It focuses on the state-of-the-art advances from fundamental theories, devices, and subsystems to networking applications as well as future perspectives of optical fiber communications. The topics cover include integrated photonics, fiber optics, fiber and free-space optical communications, and optical networking

On the Road to 6G: Visions, Requirements, Key Technologies and Testbeds

Fifth generation (5G) mobile communication systems have entered the stage of commercial development, providing users with new services and improved user experiences as well as offering a host of novel opportunities to various industries. However, 5G still faces many challenges. To address these challenges, international industrial, academic, and standards organizations have commenced research on sixth generation (6G) wireless communication systems. A series of white papers and survey papers have been published, which aim to define 6G in terms of requirements, application scenarios, key technologies, etc. Although ITU-R has been working on the 6G vision and it is expected to reach a consensus on what 6G will be by mid-2023, the related global discussions are still wide open and the existing literature has identified numerous open issues. This paper first provides a comprehensive portrayal of the 6G vision, technical requirements, and application scenarios, covering the current common understanding of 6G. Then, a critical appraisal of the 6G network architecture and key technologies is presented. Furthermore, existing testbeds and advanced 6G verification platforms are detailed for the first time. In addition, future research directions and open challenges are identified for stimulating the on-going global debate. Finally, lessons learned to date concerning 6G networks are discussed

TRANSMISSION PERFORMANCE OPTIMIZATION IN FIBER-WIRELESS ACCESS NETWORKS USING MACHINE LEARNING TECHNIQUES

The objective of this dissertation is to enhance the transmission performance in the fiber-wireless access network through mitigating the vital system limitations of both analog radio over fiber (A-RoF) and digital radio over fiber (D-RoF), with machine learning techniques being systematically implemented. The first thrust is improving the spectral efficiency for the optical transmission in the D-RoF to support the delivery of the massive number of bits from digitized radio signals. Advanced digital modulation schemes like PAM8, discrete multi-tone (DMT), and probabilistic shaping are investigated and implemented, while they may introduce severe nonlinear impairments on the low-cost optical intensity-modulation-direct-detection (IMDD) based D-RoF link with a limited dynamic range. An efficient deep neural network (DNN) equalizer/decoder to mitigate the nonlinear degradation is therefore designed and experimentally verified. Besides, we design a neural network based digital predistortion (DPD) to mitigate the nonlinear impairments from the whole link, which can be integrated into a transmitter with more processing resources and power than a receiver in an access network. Another thrust is to proactively mitigate the complex interferences in radio access networks (RANs). The composition of signals from different licensed systems and unlicensed transmitters creates an unprecedently complex interference environment that cannot be solved by conventional pre-defined network planning. In response to the challenges, a proactive interference avoidance scheme using reinforcement learning is proposed and experimentally verified in a mmWave-over-fiber platform. Except for the external sources, the interference may arise internally from a local transmitter as the self-interference (SI) that occupies the same time and frequency block as the signal of interest (SOI). Different from the conventional subtraction-based SI cancellation scheme, we design an efficient dual-inputs DNN (DI-DNN) based canceller which simultaneously cancels the SI and recovers the SOI.Ph.D

Review of Recent Trends

This work was partially supported by the European Regional Development Fund (FEDER), through the Regional Operational Programme of Centre (CENTRO 2020) of the Portugal 2020 framework, through projects SOCA (CENTRO-01-0145-FEDER-000010) and ORCIP (CENTRO-01-0145-FEDER-022141). Fernando P. Guiomar acknowledges a fellowship from “la Caixa” Foundation (ID100010434), code LCF/BQ/PR20/11770015. Houda Harkat acknowledges the financial support of the Programmatic Financing of the CTS R&D Unit (UIDP/00066/2020).MIMO-OFDM is a key technology and a strong candidate for 5G telecommunication systems. In the literature, there is no convenient survey study that rounds up all the necessary points to be investigated concerning such systems. The current deeper review paper inspects and interprets the state of the art and addresses several research axes related to MIMO-OFDM systems. Two topics have received special attention: MIMO waveforms and MIMO-OFDM channel estimation. The existing MIMO hardware and software innovations, in addition to the MIMO-OFDM equalization techniques, are discussed concisely. In the literature, only a few authors have discussed the MIMO channel estimation and modeling problems for a variety of MIMO systems. However, to the best of our knowledge, there has been until now no review paper specifically discussing the recent works concerning channel estimation and the equalization process for MIMO-OFDM systems. Hence, the current work focuses on analyzing the recently used algorithms in the field, which could be a rich reference for researchers. Moreover, some research perspectives are identified.publishersversionpublishe

A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future

A High Altitude Platform Station (HAPS) is a network node that operates in the stratosphere at an of altitude around 20 km and is instrumental for providing communication services. Precipitated by technological innovations in the areas of autonomous avionics, array antennas, solar panel efficiency levels, and battery energy densities, and fueled by flourishing industry ecosystems, the HAPS has emerged as an indispensable component of next-generations of wireless networks. In this article, we provide a vision and framework for the HAPS networks of the future supported by a comprehensive and state-of-the-art literature review. We highlight the unrealized potential of HAPS systems and elaborate on their unique ability to serve metropolitan areas. The latest advancements and promising technologies in the HAPS energy and payload systems are discussed. The integration of the emerging Reconfigurable Smart Surface (RSS) technology in the communications payload of HAPS systems for providing a cost-effective deployment is proposed. A detailed overview of the radio resource management in HAPS systems is presented along with synergistic physical layer techniques, including Faster-Than-Nyquist (FTN) signaling. Numerous aspects of handoff management in HAPS systems are described. The notable contributions of Artificial Intelligence (AI) in HAPS, including machine learning in the design, topology management, handoff, and resource allocation aspects are emphasized. The extensive overview of the literature we provide is crucial for substantiating our vision that depicts the expected deployment opportunities and challenges in the next 10 years (next-generation networks), as well as in the subsequent 10 years (next-next-generation networks).Comment: To appear in IEEE Communications Surveys & Tutorial

A REVIEW STUDY OF EUROPEAN R&D PROJECTS FOR SATELLITE COMMUNICATIONS IN 5G/6G ERA

Κατά τις τελευταίες δεκαετίες τα δορυφορικά συστήματα τηλεπικοινωνιών έχουν προσφέρει μια γκάμα από πολυμεσικές υπηρεσίες όπως δορυφορική τηλεόραση, δορυφορική τηλεφωνία και ευρυζωνική πρόσβαση στο διαδίκτυο. Οι μακροπρόθεσμες τεχνολογικές αναβαθμίσεις σε συνδυασμό με την προσθήκη νέων δορυφορικών συστημάτων γεωστατικής και ελλειπτικής τροχιάς και με την ενσωμάτωση τεχνολογιών πληροφορικής έχουν ωθήσει την αύξηση του μέγιστου εύρους των δορυφόρων στο 1Gbps σε μεμονωμένους δορυφόρους ενώ σε διάταξη αστερισμού μπορούν να ξεπεράσουν το 1 Tbps. Σε συνδυασμό με την μείωση του χρόνου απόκρισης σε ρυθμούς ανταγωνιστικούς με τις χερσαίες υποδομές ανοίγουν νέες ευκαιρίες και νέους ρόλους εντός ενός οικοσυστήματος ετερογενούς δικτύων 5ης γενιάς. Σε αυτήν την διατριβή, αξιολογούμε επιδοτούμενα επιστημονικά προγράμματα έρευνας και ανάπτυξης της Ευρωπαϊκής Επιτροπής Διαστήματος (ESA) και του προγράμματος επιδότησης Horizon 2020 της Ευρωπαϊκής Ένωσης, προκειμένου να εξηγήσουμε τις δυνατότητες των δορυφόρων εντός ενός ετερογενούς δικτύου 5ης γενιάς, αναφέρουμε συγκεκριμένα αυτά που αφορούν την εξέλιξη των δορυφορικών ψηφιακών συστημάτων και την ικανότητα ενσωμάτωσης τους σε τωρινές αλλά και μελλοντικές υποδομές χερσαίων τηλεπικοινωνιακών δικτύων μέσω της εμφάνισης νέων τεχνολογιών στις ηλεκτρονικές και οπτικές επικοινωνίες αέρος μαζί με την εμφάνιση τεχνολογιών πληροφορικής όπως της δικτύωσης βασισμένης στο λογισμικό και της εικονικοποίησης λειτουργιών δικτύου. Αναφερόμαστε στους στόχους του κάθε project ξεχωριστά και κατηγοριοποιημένα στους ακόλουθους τομείς έρευνας: -Συσσωμάτωση των δορυφόρων με τα επίγεια δίκτυα 5ης γενιάς με οργανωμένες μελέτες και στρατηγικές -Ενσωμάτωση των τεχνολογιών δικτύωσης βασισμένης στο λογισμικό και εικονικοποίησης λειτουργιών δικτύου στο δορυφορικών τμήμα των δικτύων 5ης γενιάς -Ο ρόλος των δορυφόρων σε εφαρμογές του διαδικτύου των πραγμάτων σε συνάφεια με τα χερσαία δίκτυα 5ης γενιάς -Ο ρόλος των δορυφόρων στην δίκτυα διανομής πολυμεσικού περιεχομένου & η επιρροή των πρωτοκόλλων διαδικτύου στην ποιότητα υπηρεσίας χρήστη κατά την διάρκεια μιας δορυφορικής σύνδεσης. -Μελλοντικές βελτιώσεις και εφαρμογές στα δορυφορικά συστήματα με έμφαση στα μελλοντικά πρότυπα του φυσικό επιπέδου Στο τέλος διαθέτουμε ένα παράρτημα που αφορά τεχνικές αναλύσεις στην εξέλιξη του φυσικού επιπέδου των δορυφορικών συστημάτων, συνοδευόμενο με την συσχετιζόμενη βιβλιογραφία για περαιτέρω μελέτη.Over the last decades satellite telecommunication systems offer many types of multimedia services like Satellite TV, telephony and broadband internet access. The long-term technological evolutions occurred into state-of-the-art satellite systems altogether with the addition of new high throughput geostatic and non-geostatic systems, individual satellites can now achieve a peak bandwidth of up to Gbps, and with possible extension into satellite constellation systems the total capacity can reach up to Tbps. Supplementary, with systems latency being comparable to terrestrial infrastructures and with integration of several computer science technologies, satellite systems can achieve new & more advanced roles inside a heterogeneous 5G network’s ecosystem. In this thesis, we have studied European Space Agency (ESA’s) and European Union’s (EU) Horizon 2020 Research and Development (R&D) funded projects in order to describe the satellite capabilities within a 5G heterogeneous network, mentioning the impact of the evolution of digital satellite communications and furthermore the integration with the state-of the art & future terrain telecommunication systems by new technologies occurred through the evolution of electronic & free space optical communications alongside with the integration of computer science’s technologies like Software Defined Networking (SDN) and Network Function Virtualization (NFV). In order to describe this evolution we have studied the concepts of each individual project, categorized chronically and individual by its scientific field of research. Our main scientific trends for this thesis are: -Satellite Integration studies & strategies into the 5G terrestrial networks -Integration of SDN and NFV technologies on 5G satellite component -Satellite’s role in the Internet of Things applications over 5G terrestrial networks -Satellite’s role in Content Distribution Networks & internet protocols impact over user’s Quality of Experience (QoE) over a satellite link -The future proposals upon the evolution of Satellite systems by upcoming improvements and corresponding standards Finally, we have created an Annex for technical details upon the evolution of physical layer of the satellite systems with the corresponding bibliography of this thesis for future study