82 research outputs found
Advanced Technique and Future Perspective for Next Generation Optical Fiber Communications
Optical fiber communication industry has gained unprecedented opportunities and achieved rapid progress in recent years. However, with the increase of data transmission volume and the enhancement of transmission demand, the optical communication field still needs to be upgraded to better meet the challenges in the future development. Artificial intelligence technology in optical communication and optical network is still in its infancy, but the existing achievements show great application potential. In the future, with the further development of artificial intelligence technology, AI algorithms combining channel characteristics and physical properties will shine in optical communication. This reprint introduces some recent advances in optical fiber communication and optical network, and provides alternative directions for the development of the next generation optical fiber communication technology
POINTING, ACQUISITION, AND TRACKING FOR DIRECTIONAL WIRELESS COMMUNICATIONS NETWORKS
Directional wireless communications networks (DWNs) are expected to
become a workhorse of the military, as they provide great network capacity in hostile
areas where omnidirectional RF systems can put their users in harm's way. These
networks will also be able to adapt to new missions, change topologies, use different
communications technologies, yet still reliably serve all their terminal users. DWNs
also have the potential to greatly expand the capacity of civilian and commercial
wireless communication. The inherently narrow beams present in these types of
systems require a means of steering them, acquiring the links, and tracking to
maintain connectivity. This area of technological challenges encompasses all the
issues of pointing, acquisition, and tracking (PAT).
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The two main technologies for DWNs are Free-Space Optical (FSO) and
millimeter wave RF (mmW). FSO offers tremendous bandwidths, long ranges, and
uses existing fiber-based technologies. However, it suffers from severe turbulence
effects when passing through long (>kms) atmospheric paths, and can be severely
affected by obscuration. MmW systems do not suffer from atmospheric effects
nearly as much, use much more sensitive coherent receivers, and have wider beam
divergences allowing for easier pointing. They do, however, suffer from a lack of
available small-sized power amplifiers, complicated RF infrastructure that must be
steered with a platform, and the requirement that all acquisition and tracking be done
with the data beam, as opposed to FSO which uses a beacon laser for acquisition and
a fast steering mirror for tracking.
This thesis analyzes the many considerations required for designing and
implementing a FSO PAT system, and extends this work to the rapidly expanding
area of mmW DWN systems. Different types of beam acquisition methods are
simulated and tested, and the tradeoffs between various design specifications are
analyzed and simulated to give insight into how to best implement a transceiver
platform.
An experimental test-bed of six FSO platforms is also designed and constructed
to test some of these concepts, along with the implementation of a three-node biconnected
network. Finally, experiments have been conducted to assess the
performance of fixed infrastructure routing hardware when operating with a
physically reconfigurable RF network
A study on mobile ad hoc networks equipped with free-space optical capabilities.
A mobile ad hoc network (MANET) offers a cost-effective solution for communications in areas where infrastructure is unavailable, e.g. emergency response, disaster recovery, and battlefield scenarios. Traditional MANETs operate in the radio frequency (RF) spectrum, where the available bandwidth is facing the challenge of the rapidly increasing demands. Free-space optics (FSO) provides an attractive complement to RF wireless MANETs because of its high bandwidth and interference-free operation. An effort to combine the main advantages of MANET and FSO technologies by equipping the network nodes with hybrid communications capabilities will be presented. Computer models of such a network were created using the network simulator OPNET Modeler. Various indicators of network performance, including packet loss ratio, end-to-end delay, throughput, etc. were obtained through simulation and examined. The analysis will be of significant assistance in the design and implementation of such next-generation MANETs
Modular Optical Wireless Elements
Optical wireless has gained attention in recent years as an e cient and secure way to provide broadband connectivity to mobile platforms, isolated communities, and crowded public events. Companies like NASA, Google, Facebook, and others have demonstrated its potential. However, current optical wireless technology remains mostly heavy, bulky, and expensive, making it impractical for many scenarios and inaccessible to most students/researchers.
This work presents the concept of Modular Optical Wireless Elements (MOWE), a novel system composed of multiple electrically interconnected optical modules (i.e., elements) forming a at or curved terminal that is inexpensive, lightweight, and easy-to-assemble. The technology enables cost-eff ective access to wide eld-of-view optical communication for last-mile broadband connectivity. Smart modules provide recon gurability, as well as local and central processing capabilities. The modules enable innovative short- and medium-range applications for free-space optics (FSO) in indoor communication and navigation, MIMO, and optical sensing, among others. This dissertation introduces the MOWE concept and provides in-depth information about modeling, analysis, hardware, and rmware, along with proof-of-concept examples and demonstrations. The notions of software-de ned optics and cognitive optics are introduced and analyzed in a MOWE context. Several experiments and case studies covering a wide spectrum of applications-from intelligent power control to passive beam steering-are presented in detail. This dissertation also discusses the future of MOWE technology and suggests possible improvements for high performance systems
ADVANCED RADIO ACCESS NETWORK FEATURING FLEXIBLE PER-UE SERVICE PROVISIONING AND COLLABORATIVE MOBILE EDGE COMPUTING
Enriched by numerous technological advances, radio access networks (RANs) in the fifth mobile networks generation (5G)-and-beyond strive to meet the goals of both mobile network operators (MNOs) and end-users. While MNOs seek efficiency, resiliency, reliability and flexibility of their networks, end-users are more concerned with the variety and quality of the provided, state-of-the-art, reasonably priced services. This has resulted in a complex, multi-tier, and heterogeneous RAN architecture that is severely challenged to achieve and maintain a strict reliability requirement of seven-nines (i.e., 99.99999% network up-time) and to meet ultra-reliable, low latency communications (URLLC) requirements with a latency upper bound of 1 ms end-to-end roundtrip time. Based on the flexible function split concept and data-plane programmability, this dissertation makes several key contributions to the body of knowledge on advanced, service-oriented RANs in two key core components. The first core component pertains to improving fronthaul efficiency, resiliency, flexibility, and latency performance with a cross-layer integration of Analog-Option-9 function split in the flexible fronthaul paradigm. Within the folds of that, the novel cross-layer digital-analog integration is experimentally investigated to pave the way for promising analog technologies to find their niche in 5G-and-beyond. The second core component is related to the design of lightweight, fronthaul-positioned multi-access edge computing (MEC) units to host Cooperative-URLLC applications at the edge of the fronthaul. Hence, from the vertical perspective, the dissertation provides solutions to support general URLLC applications and the Cooperative-URLLC variation by shrinking and eliminating latency sources at the Top-of-RAN and Low-RAN segments of advanced RANs.Ph.D
Tecnologias coerentes para redes ópticas flexíveis
Next-generation networks enable a broad range of innovative services with
the best delivery by utilizing very dense wired/wireless networks. However,
the development of future networks will require several breakthroughs in
optical networks such as high-performance optical transceivers to support a
very-high capacity optical network as well as optimization of the network
concept, ensuring a dramatic reduction of the cost per bit.
At the same time, all of the optical network segments (metro, access,
long-haul) need new technology options to support high capacity, spectral
efficiency and data-rate flexibility. Coherent detection offers an opportunity
by providing very high sensitivity and supporting high spectral efficiency.
Coherent technology can still be combined with polarization multiplexing.
Despite the increased cost and complexity, the migration to dual-polarization
coherent transceivers must be considered, as it enables to double the spectral
efficiency. These dual-polarization systems require an additional digital signal
processing (DSP) subsystem for polarization demultiplexing. This work seeks
to provide and characterize cost-effective novel coherent transceivers for
the development of new generation practical, flexible and high capacity
transceivers for optical metro-access and data center interconnects. In this
regard, different polarization demultiplexing (PolDemux) algorithms, as well
as adaptive Stokes will be considered.
Furthermore, low complexity and modulation format-agnostic DSP techniques
based on adaptive Stokes PolDemux for flexible and customizable
optical coherent systems will be proposed. On this subject, the performance
of the adaptive Stokes algorithm in an ultra-dense wavelength division multiplexing
(U-DWDM) system will be experimentally evaluated, in offline
and real-time operations over a hybrid optical-wireless link. In addition, the
efficiency of this PolDemux algorithm in a flexible optical metro link based
on Nyquist pulse shaping U-DWDM system and hybrid optical signals will be
assessed. Moreover, it is of great importance to find a transmission technology
that enables to apply the Stokes PolDemux for long-haul transmission
systems and data center interconnects. In this work, it is also proposed
a solution based on the use of digital multi-subcarrier multiplexing, which
improve the performance of long-haul optical systems, without increasing
substantially, their complexity and cost.As redes de telecomunicações futuras permitirão uma ampla gama de serviços
inovadores e com melhor desempenho. No entanto, o desenvolvimento das
futuras redes implicará vários avanços nas redes de fibra ótica, como transcetores
óticos de alto desempenho capazes de suportar ligações de muito
elevada capacidade, e a otimização da estrutura da rede, permitindo uma
redução drástica do custo por bit transportado.
Simultaneamente, todos os segmentos de rede ótica (metropolitanas, acesso
e longo alcance) necessitam de novas opções tecnológicas para suportar
uma maior capacidade, maior eficiência espetral e flexibilidade. Neste contexto,
a deteção coerente surge como uma oportunidade, fornecendo alta
sensibilidade e elevada eficiência espetral. A tecnologia de deteção coerente
pode ainda ser associada à multiplexação na polarização. Apesar de um
potencial aumento ao nível do custo e da complexidade, a migração para
transcetores coerentes de dupla polarização deve ser ponderada, pois permite
duplicar a eficiência espetral. Esses sistemas de dupla polarização requerem
um subsistema de processamento digital de sinal (DSP) adicional para desmultiplexagem
da polarização. Este trabalho procura fornecer e caracterizar
novos transcetores coerentes de baixo custo para o desenvolvimento de uma
nova geração de transcetores mais práticos, flexíveis e de elevada capacidade,
para interconexões óticas ao nível das futuras redes de acesso e metro.
Assim, serão analisados diferentes algoritmos para a desmultiplexagem da
polarização, incluindo uma abordagem adaptativa baseada no espaço de
Stokes.
Além disso, são propostas técnicas de DSP independentes do formato de
modulação e de baixa complexidade baseadas na desmultiplexagem de Stokes
adaptativa para sistemas óticos coerentes flexíveis. Neste contexto, o desempenho
do algoritmo adaptativo de desmultiplexagem na polarização
baseado no espaço de Stokes é avaliado experimentalmente num sistema
U-DWDM, tanto em análises off-line como em tempo real, considerando um
percurso ótico hibrido que combina um sistema de transmissão suportado
por fibra e outro em espaço livre. Foi ainda analisada a eficiência do algoritmo
de desmultiplexagem na polarização numa rede ótica de acesso flexível
U-DWDM com formatação de pulso do tipo Nyquist. Neste trabalho foi
ainda analisada a aplicação da técnica de desmultiplexagem na polarização
baseada no espaço de Stokes para sistemas de longo alcance. Assim, foi
proposta uma solução de aplicação baseada no uso da multiplexagem digital
de múltiplas sub-portadoras, tendo-se demonstrado uma melhoria na eficiência
do desempenho dos sistemas óticos de longo alcance, sem aumentar
significativamente a respetiva complexidade e custo.Programa Doutoral em Engenharia Eletrotécnic
Advanced DSP Techniques for High-Capacity and Energy-Efficient Optical Fiber Communications
The rapid proliferation of the Internet has been driving communication networks closer and closer to their limits, while available bandwidth is disappearing due to an ever-increasing network load. Over the past decade, optical fiber communication technology has increased per fiber data rate from 10 Tb/s to exceeding 10 Pb/s. The major explosion came after the maturity of coherent detection and advanced digital signal processing (DSP). DSP has played a critical role in accommodating channel impairments mitigation, enabling advanced modulation formats for spectral efficiency transmission and realizing flexible bandwidth. This book aims to explore novel, advanced DSP techniques to enable multi-Tb/s/channel optical transmission to address pressing bandwidth and power-efficiency demands. It provides state-of-the-art advances and future perspectives of DSP as well
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
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