239 research outputs found
An Overview on Application of Machine Learning Techniques in Optical Networks
Today's telecommunication networks have become sources of enormous amounts of
widely heterogeneous data. This information can be retrieved from network
traffic traces, network alarms, signal quality indicators, users' behavioral
data, etc. Advanced mathematical tools are required to extract meaningful
information from these data and take decisions pertaining to the proper
functioning of the networks from the network-generated data. Among these
mathematical tools, Machine Learning (ML) is regarded as one of the most
promising methodological approaches to perform network-data analysis and enable
automated network self-configuration and fault management. The adoption of ML
techniques in the field of optical communication networks is motivated by the
unprecedented growth of network complexity faced by optical networks in the
last few years. Such complexity increase is due to the introduction of a huge
number of adjustable and interdependent system parameters (e.g., routing
configurations, modulation format, symbol rate, coding schemes, etc.) that are
enabled by the usage of coherent transmission/reception technologies, advanced
digital signal processing and compensation of nonlinear effects in optical
fiber propagation. In this paper we provide an overview of the application of
ML to optical communications and networking. We classify and survey relevant
literature dealing with the topic, and we also provide an introductory tutorial
on ML for researchers and practitioners interested in this field. Although a
good number of research papers have recently appeared, the application of ML to
optical networks is still in its infancy: to stimulate further work in this
area, we conclude the paper proposing new possible research directions
A Distributed Asynchronous Transmission Access Strategy for Optical Single-Hop LANs: An Analytical Performance Study
In this paper, we introduce an optical passive network architecture suitable for wavelength division multiplexing local area networks (LANs) which use a separate control wavelength. The data wavelengths are organized into several sets, while the access rights over them are distributedly determined aiming to totally expunge the packets collisions on the wavelengths and at destination. The proposed access algorithm pertains to the asynchronous transmission schemes. Thus, it is simple enough since it does not require any synchronization among the stations, providing high efficiency especially under high data rates (100 Gbps and beyond). The performance is evaluated through exhaustive analysis, whilst closed mathematical formulas provide the performance measures. The comparative study proves that the proposed wavelengths organization into sets strategy along with the access scheme significantly improves the performance. Especially, the throughput improvement is proven to be higher as the number of sets increases, and more than 100% even by organizing the wavelengths into only two sets, for diverse numbers of data wavelengths, data wavelengths sets and data packets size. Finally, the proposed study could be applied to optical passive single-hop LANs such as intra-rack data center networks or local institutional or enterprise networks
How Graph Theory can help Communications Engineering
International audienceWe give an overview of different aspects of graph theory which can be applied in communication engineering, not trying to present immediate results to be applied neither a complete survey of results, but to give a flavor of how graph theory can help this field. We deal in this paper with network topologies, resource competition, state transition diagrams and specific models for optical networks
Directly Phase Modulated Transmitters and Coherent Recivers for Future Passive Optical Networks (PON)
En los Ășltimos años, el trĂĄfico de dato transmitido en las redes Ăłpticas de acceso ha crecido exponencialmente debido a nuevos servicios como pueden ser la computaciĂłn en la nube, el video online, la realidad virtual y aumentada, el internet de las cosas (IoT) y la convergencia entre las redes Ăłpticas y redes inalĂĄmbricas en el paradigma del 5G. Estos nuevos servicios endurecen los requerimientos de las redes Ăłpticas de acceso, como pueden ser unas tasas de datos mĂĄs altas, un mayor alcance y un mayor nĂșmero de usuarios. Para abordar estos requerimientos, esta tesis ha investigado, desarrollado y analizado nuevas tecnologĂas para transmisores y receptores orientadas a los dos tipos de redes Ăłpticas de acceso que la comunidad cientĂfica ha identificado como posibles candidatas. Estos dos tipos de redes Ăłpticas son las redes uDWDM y las redes TWDM como las redes NG-PON2 y sus evoluciones.Las redes uDWDM estĂĄn basadas en la transmisiĂłn de tasas de datos relativamente bajas, por debajo de 2.5 Gbps, que son dedicadas en su totalidad a los usuarios finales. Estas tasas de datos relativamente bajas son multiplexadas en longitud de onda usando intervalos frecuenciales estrechos, del orden de 12.5 GHz o 6.25 GHz. En esta tesis, los transmisores modulados directamente en fase se han propuesto como posibles candidatos para estas redes uDWDM. En concreto, se han propuesto un DFB modulado directamente en fase con una tasa de datos de 1 Gbps; un RSOA bombeado por un VCSEL y modulado directamente en fase con una tasa de datos de 1 Gbps; y un VCSEL modulado directamente en fase con una tasa de datos de 1.25 Gbps y 2.5 Gbps. Estas señales moduladas directamente en fase son recibidas con un receptor heterodino con un Ășnico fotodiodo (PD) para mantener el coste tan bajo como sea posible. La combinaciĂłn de estos transmisores modulados directamente en fase con el receptor heterodino con un Ășnico PD ha sido probada como unos candidatos muy prometedores para las redes Ăłpticas de acceso basadas en redes uDWDM. Estas combinaciones proveen sensibilidades que varĂan entre -39.5 dBm y -52 dBm, que se traducen en balances de potencia que van desde 38.5 dB a 51 dB y por lo tanto en ratios de divisiĂłn o nĂșmero de usuarios de entre 128 y 1024 despuĂ©s de una transmisiĂłn de 50 km a travĂ©s de fibra monomodo estĂĄndar (SSMF).AdemĂĄs, los links de 1 Gbps formados por la modulaciĂłn directa de DFBs o de RSOAs bombeados por VCSELs y el receptor heterodino con un Ășnico PD son usados como enlace de subida en canales bidireccionales. Estos enlaces de subida son combinados con enlaces de bajada basados en Nyquist-DPSK generada con un MZM y recibidos con un receptor heterodino de un Ășnico PD. Como parte de anĂĄlisis de los canales bidireccionales, se ha analizado el estudio de la viabilidad del uso de LOs de bajo coste, como DFBs o VCSELs, en los receptores heterodinos con un Ășnico PD. Estos canales bidireccionales son tambiĂ©n unos candidatos prometedores para las futuras redes uDWDM, ya que en esta tesis se ha probado que pueden proveer enlaces full-duplex de 1 Gbps usando intervalos frecuenciales tan pequeños como 6.25 GHz o 5 GHz. Estos canales bidireccionales tienen balances de potencia que van desde 37 dB a 42 dB y tienen posibles ratios de divisiĂłn de 128 o 256 despuĂ©s de una transmisiĂłn de 50 km a travĂ©s de SSMF.Esta tesis tambiĂ©n ha investigado y desarrollado receptores quasicoherentes para redes NG-PON2 y sus evoluciones. Este tipo de redes estĂĄn basadas en altas tasas de datos, como 10 Gbps para redes NG-PON2 y 25 Gbps para las futuras evoluciones de NG-PON2, en entornos multi longitud de onda donde los usuarios son multiplexados en tiempo y longitud de onda (TWDM). El receptor quasicoherente usa la amplificaciĂłn coherente gracias a la recepciĂłn heterodina y por tanto la sensibilidad del receptor es mejorada en comparaciĂłn con los esquemas de detecciĂłn directa. El receptor quasicoherente es independiente a la polarizaciĂłn, lo cual es una caracterĂstica importante para los receptores coherentes. AdemĂĄs, el receptor quasicoherente permite seleccionar el canal de trabajo sin la necesidad de filtros Ăłpticos y es un receptor independiente de la longitud de onda debido a que el canal de trabajo se puede elegir ajustando la longitud de onda del LO. El receptor quasicoherente de 10 Gbps muestra una sensibilidad -35.2 dBm y por tanto permite un balance de potencias de 35.64 dB y un ratio de divisiĂłn de 128 despuĂ©s de una transmisiĂłn de 40 km a travĂ©s de SSMF.La combinaciĂłn del receptor quasicoherente con un ecualizador FFE/DFE permite combatir la dispersiĂłn cromĂĄtica de la banda C y conseguir un link de 25 Gbps con un alcance de 20 km a travĂ©s de SSMF. El receptor quasicoherente a 25 Gbps con ecualizaciĂłn FFE/DFE muestra una mejor sensibilidad de -30.5 dBm con el llamado ecualizador de altas prestaciones, lo que lleva a un balance de potencias de25 dB. Si se utilizada el llamado ecualizador de baja complejidad, la sensibilidad cae a -27 dBm y el balance de potencias cae a 23 dBm. En ambos casos, el receptor quasicoherente a 25 Gbps con ecualizaciĂłn FFE/DFE permite un ratio de divisiĂłn de 32 despuĂ©s de una transmisiĂłn de 20 km a travĂ©s de SSMF.En conclusiĂłn, esta tesis ha presentado transmisores (DFB, RSOA y VCSEL) modulados directamente en fase combinados con un receptor heterodino con un Ășnico PD como potenciales candidatos para las redes uDWDM. Esta tesis tambiĂ©n ha presentados los receptores quasicoherentes como unos candidatos muy prometedores para las redes NG-PON2 y sus futuras evoluciones.<br /
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
Particle swarm optimization for routing and wavelength assignment in next generation WDM networks.
PhDAll-optical Wave Division Multiplexed (WDM) networking is a promising technology for long-haul backbone and large metropolitan optical networks in order to meet the non-diminishing bandwidth demands of future applications and services. Examples could include archival and recovery of data to/from Storage Area Networks (i.e. for banks), High bandwidth medical imaging (for remote operations), High Definition (HD) digital broadcast and streaming over the Internet, distributed orchestrated computing, and peak-demand short-term connectivity for Access Network providers and wireless network operators for backhaul surges. One desirable feature is fast and automatic provisioning. Connection (lightpath) provisioning in optically switched networks requires both route computation and a single wavelength to be assigned for the lightpath. This is called Routing and Wavelength Assignment (RWA). RWA can be classified as static RWA and dynamic RWA. Static RWA is an NP-hard (non-polynomial time hard) optimisation task. Dynamic RWA is even more challenging as connection requests arrive dynamically, on-the-fly and have random connection holding times. Traditionally, global-optimum mathematical search schemes like integer linear programming and graph colouring are used to find an optimal solution for NP-hard problems. However such schemes become unusable for connection provisioning in a dynamic environment, due to the computational complexity and time required to undertake the search. To perform dynamic provisioning, different heuristic and stochastic techniques are used.
Particle Swarm Optimisation (PSO) is a population-based global optimisation scheme that belongs to the class of evolutionary search algorithms and has successfully been used to solve many NP-hard optimisation problems in both static and dynamic environments. In this thesis, a novel PSO based scheme is proposed to solve the static RWA case, which can achieve optimal/near-optimal solution. In order to reduce the risk of premature convergence of the swarm and to avoid selecting local optima, a search scheme is proposed to solve the static RWA, based on the position of swarmâs global best particle and personal best position of each particle.
To solve dynamic RWA problem, a PSO based scheme is proposed which can provision a connection within a fraction of a second. This feature is crucial to provisioning services like bandwidth on demand connectivity. To improve the convergence speed of the swarm towards an optimal/near-optimal solution, a novel chaotic factor is introduced into the PSO algorithm, i.e. CPSO, which helps the swarm reach a relatively good solution in fewer iterations. Experimental results for PSO/CPSO based dynamic RWA algorithms show that the proposed schemes perform better compared to other evolutionary techniques like genetic algorithms, ant colony optimization. This is both in terms of quality of solution and computation time. The proposed schemes also show significant improvements in blocking probability performance compared to traditional dynamic RWA schemes like SP-FF and SP-MU algorithms
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