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Digital Theses Archive

 

Tesi etd-08282019-113803

Type of thesis
Dottorato
Author
MESSA, ALESSANDRO
URN
etd-08282019-113803
Title
Optical Wireless: an emerging solution for next-generation communications.
Scientific disciplinary sector
ING-INF/03
Course
INGEGNERIA - Ph.D. Programme in Emerging Digital Technologies (EDT)
Committee
Presidente Prof. CIARAMELLA, ERNESTO
Membro Prof. BOFFI, PIERPAOLO
Membro Dott. SCARADOZZI, DAVID
Tutor COSSU, GIULIO
Membro Prof. CONTESTABILE, GIAMPIERO
Keywords
  • Data Center Network
  • DMT
  • Free Space Optics
  • High Energy Physics
  • LED
  • MIMO
  • Optical Wireless Communication
  • photodiode
  • VCSEL
  • Visible Light Communication
  • WDM
Exam session start date
;
Availability
completa
Abstract
The new millennium that we are facing is characterized by profound technological and social transformations dictated by a disruptive digital revolution. In this scenario, the telecommunications industry plays a pivotal role in providing the infrastructure for increasingly greedy data services. The main objective of the next generation of communication is to reach everyone everywhere by offering broadband transmission channels. For this reason, wireless devices have spread rapidly, becoming an essential component for the society of the future. Typically, the term “wireless” is associated with RF communication systems both for historical and commercial pervasiveness reasons. But, despite the enormous success, this technology comes up against its biggest limit: “The Spectrum Crunch”. A finite natural resource like the RF spectrum is not able to sustain an exponential demand of frequency allocation, in fact, governments around the world and the International Telecommunication Union (ITU) are constantly engaged in finding new solutions.<br>Optical Wireless Communication (OWC) is an emerging solution to these problems. The OWC systems exploit optical radiation as a carrier for signal transmission in free space. The wide spectrum (ranging from Infra-Red (IR) to Ultra-Violet (UV) wavelength) free of licenses, the potential for high transmission capacity and low costs make this technology extremely interesting for the scientific community. In the last decades, the OWC has managed to obtain different spaces in the communications sector, proving to be a complementary technology to RF, especially in those applications where RF communications are disadvantaged (interference, security, propagation difficulties, etc.). Furthermore, the diffusion of solid-state lighting systems has been the main driver for the development of VLC (OWC using the visible spectrum), thanks to the Light Emitting Diode (LED) ability of a faster switching compared with conventional lighting. All these conditions have shifted the interest also outside the academy. In2003 the Visible Light Communication Consortium (VLCC) was founded and in 2014became Visible Light Communication Association (VLCA) [1]. Currently, the OWC is at the verge of maturity, in April 2019 the Institute of Electrical and Electronic Engineers (IEEE) 802.15.7 standard on Short-Range OWC has been published and IEEE802.15.13 is in developing phase.<br>In such a dynamic and complex context full of application scenarios, the author intends to present in this manuscript his personal contributions made during the PhD. Presenting cutting-edge applications for next-generation communications. The thesis is organized as follows:<br><br>Chapter 1 introduces the basics of OWC systems, providing a general overview of the system architectures, analyzing their various opto-electronic components and functional blocks, modeling the transmission channel and the related noise sources. Finally, the main modulation formats used in this manuscript are described.<br><br>Chapter 2 describes the realization and experimental results of an IR optical connection for indoor applications. The proposed Non-directed (Nd-)Line-of-Sight (LOS)OWC system exploits an Orthogonal Frequency-Division Multiplexing (OFDM) modulation technique in combination with an analog equalization in order to achieve a real time 230 Mbit/s transmission.<br><br>Chapter 3 reports all the experimental demonstrations and milestones of our High Throughput OWC systems developed for Data Center applications. The chapter presents three OWC systems with different bit rates (10 Gbit/s, 24 Gbit/s, 40 Gbit/s), analyzing the tolerance to misalignment and highlighting how active alignment is not essential whether there is an adequate mechanical precision.<br><br>Chapter 4 reports the peculiar OWC application for High Energy Physics (HEP). The results obtained quantify for the first time the opto-electronic components tolerance to a high-energy proton beam irradiation and they outline the way for the next design choices.<br><br>Chapter 5 illustrates the work initiated at Vienna University of Technology and finished at Sant’Anna School of Advanced Studies by the author. The carried out research reports, for the first time, a novel VLC WDM system using a single Triple Junction (TJ) photodiode (PD) in combination with a MIMO post-processing.<br><br>Chapter 6 summarizes the author’s contributions in this work and it put the obtained results in perspective with respect to the challenges of the future of next generation communication technologies.
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