84 research outputs found

    Maximally spatial-disjoint lightpaths in optical networks

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    Lightpaths enable end-to-end all-optical transmission between network nodes. For survivable routing, traffic is often carried on a primary lightpath, and rerouted to another disjointed backup lightpath in case of the failure of the primary lightpath. Though both lightpaths can be physically disjointed, they can still fail simultaneously if a disaster affects them simultaneously on the physical plane. Hence, we propose a routing algorithm for provisioning a pair of link-disjoint lightpaths between two network nodes such that the minimum spatial distance between them (while disregarding safe regions) is maximized. Through means of simulation, we show that our algorithm can provide higher survivability against spatial-based simultaneous link failures (due to the maximized spatial distance)

    Route, modulation format, MIMO and spectrum assignment in Flex-Grid/MCF transparent optical core networks

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    In this paper, we target an optimal multiple-input multiple-output digital signal processing (MIMO-DSP) assignment to super-channels affected by intercore crosstalk (ICXT) in multicore fiber (MCF) enabled transparent optical core networks. MIMO-DSP undoes ICXT effects, but can be costly with high core density MCFs. Hence, its implementation in the network must be carefully decided. We address our objective as a joint route, modulation format, MIMO and spectrum assignment (RMMSA) problem, for which integer linear programming formulations are provided to optimally solve it in small network scenarios. Moreover, several heuristic approaches are also proposed to solve large-scale problem instances with good accuracy. Their goal is to minimize both network spectral requirements and the amount of MIMO equalized super-channels, taking a crosstalk-free space division multiplexing (SDM) solution as a reference, for example, based on parallel single mode fibers [i.e., a multifiber (MF) scenario]. For our evaluation, we consider several state-of-the-art MCF prototypes and different network topologies. The obtained results, with the considered MCFs, disclose that in national backbone networks, the desirable percentage of super-channels with MIMO equalization to match the performance of an equivalent crosstalk-free SDM solution ranges from 0% to 36, while in continental-wide networks this range raises from 0% to 56%. In addition, in the case of a nonideal MIMO (with a 3 dB/km of crosstalk compensation), such percentages range from 0% to 28% and from 0% to 45% in national and continental-wide backbone networks, respectively, experimenting a performance gap up to 12% with respect to the MF reference scenario.Peer ReviewedPostprint (author's final draft

    CSCI 2017

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    Producción CientíficaElastic Optical Networks (EON) are seen as an essential technology to implement the backhaul of Future Internet allowing the deployment of emerging paradigms like the Internet of Things (IoT), Tactile Internet, or Industry 4.0. When designing those Elastic Optical Networks (EONs), the Routing and Spectrum Assignment (RSA) problem has to be solved. In this paper, we analyse the effect of using two types of flexibility in a well‑known RSA method. A simulation study will be presented with the main results of this comparison.Ministerio de Economía, Industria y Competitividad (Projects TEC2014-53071-C3-2-P, TEC2015-71932-REDT)Ministerio de Educación, Cultura y Deporte (Proyect BES-2015-074514

    Contributions to network planning and operation of Flex-Grid/SDM optical core networks

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    Premi Extraordinari de Doctorat, promociĂł 2018-2019. Àmbit de les TICThe ever demanding bandwidth requirements for supporting emerging telecom services such as ultra-high-definition video streaming, cloud computing, connected car, virtual/augmented reality, etc., bring to the fore the necessity to upgrade continuously the technology behind transport networks in order to keep pace with this exponential traffic growth. Thus, everything seems to indicate that fixed-grid Wavelength-Division Multiplexed (WDM) networks will be upgraded by adopting a flexible-grid, thus providing finer bandwidth allocation granularities, and therefore, increasing the Grade-of-Service by packing more information in the same spectral band of standard Single-Mode Fibers (SMFs). Nevertheless, unfortunately, the fundamental Shannon’s limit of SMFs is rapidly approaching, and, then, the research efforts to increase the SMFs' capacity will be useless. One solution to overcome this capacity crunch effect is to enable one extra dimension in addition to the frequency one, namely, the spatial dimension, thus deploying S parallel paths in order to multiply, in the best case, by S the capacity of SMF-based networks. However, additionally, it is necessary to decrease the cost and energy per bit in order to provide economically attractive solutions. For this purpose, a smooth upgrade path has to be carried out as new integrated devices and system components are developed for Space Division Multiplexing (SDM). This thesis is concentrated on the planning and operation of the combined flexible WDM and SDM networks (i.e., Flex-Grid/SDM networks) proposing several strategies aimed at optimizing network resources usage with hardware complexity analysis. For this purpose, firstly, network problems are carefully studied and stated, and then, mathematical and/or heuristic algorithms are designed and implemented in an optical network simulator. Specifically, after an introduction to the thesis, chapter 2 presents the background and related work. Next, chapter 3 concentrates on the study of spatially fixed Flex-Grid/SDM networks, i.e., when a rigid number of spatial channels are reserved per allocated traffic demand. In its turn, chapter 4 studies the case of Spectrally-Spatially Flexible Optical Networks (SS-FONs), as the ones providing the upper-bound network capacity. Costs and hardware requirements implied on providing this flexibility are analyzed. Network nodes aimed at reducing the cost of SS-FONs are presented and evaluated in chapter 5. Finally, this thesis ends with the presentation of the main contributions and future research work in chapter 6.La demanda de ancho de banda cada vez mĂĄs exigente para soportar servicios de telecomunicaciĂłn emergentes tales como la transmisiĂłn de video de alta calidad, computaciĂłn en la nube, vehĂ­culo conectado, realidad virtual/aumentada, etc.
, ha puesto de manifiesto la necesidad de actualizar constantemente la tecnologĂ­a detrĂĄs de las redes de transporte Ăłptico con la finalidad de ir a la par de este incremento exponencial del trĂĄfico. De esta manera, todo parece indicar que las redes basadas en la multiplexaciĂłn por division de longitud de onda (Wavelength Division Multiplexing, WDM) de ancho espectral fijo serĂĄn actualizadas adoptando un ancho de banda espectral flexible, que ofrece asignaciones de ancho de banda con granularidad mĂĄs fina acorde a las demandas de trĂĄfico; y por lo tanto, incremanta el Grado de Servicio de la red, ya que se permite acomodar mayor informaciĂłn en la misma banda espectral de las fibras monomodo (Single Mode Fibers, SMFs). Sin embargo, desafortunadamente, el lĂ­mite de Shannon de las fibras monomodo se estĂĄ aproximando cada vez mĂĄs, y cuando esto ocurra las investigaciones para incrementar la capacidad de las fibras monomodo serĂĄn infructuosas. Una posible soluciĂłn para superar este colapso de las fibras monomodo es habilitar la dimensiĂłn espacial a mĂĄs de la frecuencial, desplegando ïżœ caminos paralelos con la finalidad de multiplicar por ïżœ (en el mejor de los casos) la capacidad de las fibras monomodo. No obstante, es necesario disminuir el costo y la energĂ­a por bit con la finalidad de proveer soluciones comerciales atractivas. Para tal propĂłsito debe llevarse a cabo una actualizaciĂłn moderada conforme nuevos dispositivos y componentes integrados son desarrollados para la implementaciĂłn de la tecnologĂ­a basada en la multiplexaciĂłn por divisiĂłn de espacio (Space Division Multiplexing, SDM). Esta tesis se concentra en la planificaciĂłn y operaciĂłn de la combinaciĂłn de las redes WDM flexibles y SDM (es decir, de las redes Flex-Grid/SDM) proponiendo varias estrategias dirigidas a optimizar el uso de los recursos de red junto con el anĂĄlisis de la complejidad del hardware que viene acompañada. Para este fin, primeramente, los problemas de red son cuidadosamente estudiados y descritos. A continuaciĂłn, se han diseñado e implementado algoritmos basados en programaciĂłn lineal entera o heurĂ­sticas en un simulador de redes Ăłpticas. DespuĂ©s de una introducciĂłn inicial, el capĂ­tulo 2 de esta tesis presenta el marco teĂłrico sobre los conceptos tratados y los trabajos publicados anteriormente. A continuaciĂłn, el capĂ­tulo 3 se concentra en el estudio de las redes Flex-Grid/SDM con la dimensiĂłn espacial rĂ­gida; es decir, cuando un nĂșmero fijo de canales espaciales son reservados por cada demanda de trĂĄfico establecida. Por su parte, el capĂ­tulo 4 estudia las redes Flex-Grid/SDM considerando flexibilidad tanto en el dominio espacial como espectral (Spectrally and Spatially Flexible Optical Networks, SS-FONs), las cuales proveerĂ­an la capacidad mĂĄxima de las redes SDM. Adicionalmente, los costos y requerimientos de hardware implicados en la provisiĂłn de esta flexibilidad son analizados. El capĂ­tulo 5 presenta la evaluaciĂłn de nodos orientados a reducir los costos de las SS-FONs. Finalmente, el capĂ­tulo 6 expone las principales contribuciones y las posibles lĂ­neas de trabajo futuroEls requisits incessants d’ample de banda per al suport de nous serveis de telecomunicaciĂł, com poden ser la difusiĂł en directe de vĂ­deo de molt alta definiciĂł, la informĂ tica en el nĂșvol, els cotxes intel·ligents connectats a la xarxa, la realitat virtual/augmentada, etc
, han exigit una millora contĂ­nua de les tecnologĂ­es de les actuals xarxes de transport de dades. Tot sembla indicar que les xarxes de transport ĂČptiques actuals, basades en la tecnologia de multiplexaciĂł per divisiĂł de longitud d’ona (Wavelength Division Multiplexing, WDM) sobre un grid espectral rĂ­gid, hauran de ser reemplaçades per tecnologies ĂČptiques mĂ©s flexibles, amb una granularitat mĂ©s fina a l’hora de suportar noves connexions, incrementat el grau de servei de les xarxes grĂ cies a aprofitament major de l’ample de banda espectral proporcionat per les fibres ĂČptiques monomode (Single Mode Fibers, SMFs). Tanmateix, estem exhaurint ja la capacitat mĂ xima de les fibres ĂČptiques SMF segons ens indica el lĂ­mit fonamental de Shannon. Per tant, qualsevol esforç enfocat a millorar la capacitat d’aquestes xarxes basades en SMFs pot acabar sent infructuĂłs. Una possible soluciĂł per superar aquestes limitacions de capacitat Ă©s explorar la dimensiĂł espacial, a mĂ©s de l’espectral, desplegant camins en paral·lel per tal de multiplicar per , en el millor cas, la capacitat de les SMFs. Tot i aixĂČ, Ă©s necessari reduir el cost i el consum energĂštic per bit transmĂšs, per tal de proporcionar solucions econĂČmicament viables. Amb aquest propĂČsit, pot ser necessĂ ria una migraciĂł progressiva, a mesura que es desenvolupen nous dispositius i components per aquesta nova tecnologia de multiplexaciĂł per divisiĂł espacial (Spatial Division Multiplexing, SDM). La present tesi es centra en la planificaciĂł i operaciĂł de xarxes ĂČptiques de nova generaciĂł que combinin tecnologies de xarxa WDM flexible i SDM (Ă©s a dir, xarxes Flex-Grid/SDM), proposant estratĂšgies per a l’optimitzaciĂł de l’Ășs dels recursos de xarxa i, en definitiva, el seu cost (CapEx). Amb aquest propĂČsit, s’analitzen en primer moment els problemes adreçats. Tot seguit, es dissenyen algorismes per tal de solucionar-los, basats en tĂšcniques de programaciĂł matemĂ tica i heurĂ­stiques, els quals s’implementen i es proven en un simulador de xarxa ĂČptica. DesprĂ©s d’una introducciĂł inicial, el capĂ­tol 2 d’aquesta tesi presenta tots els conceptes tractats i treballs relacionats publicats amb anterioritat. Tot seguit, el capĂ­tol 3 es centra en l’estudi de les xarxes Flex-Grid/SDM fixes en el domini espai, Ă©s a dir, on sempre es reserva un nombre rĂ­gid de canals espacials per qualsevol demanda suportada. El capĂ­tol 4 estudia les xarxes flexibles en els dominis espectrals i espacials (Spectrally-Spatially Flexible Optical Nextworks, SS-FONs), com aquelles que poden proporcionar una capacitat de xarxa mĂ xima. En aquest context, s’analitzen els requeriments en termes de cost i hardware per tal de proporcionar aquesta flexibilitat. Llavors, en el capĂ­tol 6 es presenten opcions de node de xarxa capaces de reduir els costos de les xarxes SS-FONs. Finalment, en el capĂ­tol 7 es repassen totes les contribucions de la tesi, aixĂ­ com posibles lĂ­nies de treball futurAward-winningPostprint (published version

    Resilient Resource Allocation Schemes in Optical Networks

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    Recent studies show that deliberate malicious attacks performed by high-power sig- nals can put large amount of data under risk. We investigate the problem of sur- vivable optical networks resource provisioning scheme against malicious attacks, more specically crosstalk jamming attacks. These types of attacks may cause ser- vice disruption (or possibly service denial). We consider optical networks based on wavelength-division multiplexing (WDM) technology and two types of jamming at- tacks: in-band and out-of-band attacks. We propose an attack-aware routing and wavelength assignments (RWA) scheme to avoid or reduce the damaging effects of potential attacking signals on individual or multiple legitimate lightpaths travers- ing the same optical switches and links. An integer linear programs (ILPs) as well as heuristic approaches were proposed to solve the problem. We consider dynamic traffic where each demand is dened by its start time and a duration. Our results show that the proposed approaches were able to limit the vulnerability of lightpaths to jamming attacks. Recently, large-scale failures caused by natural disasters and/or deliberate at- tacks have left major parts of the networks damaged or disconnected. We also investigate the problem of disaster-aware WDM network resource provisioning in case of disasters. We propose an ILP and efficient heuristic to route the lightpaths in such a way that provides protection against disasters and minimize the network vi resources such as the number of wavelength links used in the network. Our models show that signicant resource savings can be achieved while accommodating users demands. In the last few years, optical networks using Space Division Multiplexing (SDM) has been proposed as a solution to the speed bottleneck anticipated in data center (DC) networks. To our knowledge the new challenges of designing such communica- tion systems have not been addressed yet. We propose an optimal approach to the problem of developing a path-protection scheme to handle communication requests in DC networks using elastic optical networking and space division multiplexing. We have formulated our problem as an ILP. We have also proposed a heuristic that can handle problems of practical size. Our simulations explore important features of our approach

    A heuristic for placement of limited range wavelength converters in all-optical networks

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    Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength converters play an important role in enhancing the fiber utilization and reducing the overall call blocking probability of the network. As the distortion of the optical signal increases with the increase in the range of wavelength conversion in optical wavelength converters, limited range wavelength conversion assumes importance. Placement of wavelength converters is a NP complete problem [K.C. Lee, V.O.K. Li, IEEE J. Lightwave Technol. 11 (1993) 962-970] in an arbitrary mesh network. In this paper, we investigate heuristics for placing limited range wavelength converters in arbitrary mesh wavelength routed optical networks. The objective is to achieve near optimal placement of limited range wavelength converters resulting in reduced blocking probabilities and low distortion of the optical signal. The proposed heuristic is to place limited range wavelength converters at the most congested nodes, nodes which lie on the long lightpaths and nodes where conversion of optical signals is significantly high. We observe that limited range converters at few nodes can provide almost the entire improvement in the blocking probability as the full range wavelength converters placed at all the nodes. Congestion control in the network is brought about by dynamically adjusting the weights of the channels in the link thereby balancing the load and reducing the average delay of the traffic in the entire network. Simulations have been carried out on a 12-node ring network, 14-node NSFNET, 19-node European Optical Network (EON), 28-node US long haul network, hypothetical 30-node INET network and the results agree with the analysis. (C) 2001 Elsevier Science B.V, All rights reserved

    Contributions to network planning and operation of Flex-Grid/SDM optical core networks

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    The ever demanding bandwidth requirements for supporting emerging telecom services such as ultra-high-definition video streaming, cloud computing, connected car, virtual/augmented reality, etc., bring to the fore the necessity to upgrade continuously the technology behind transport networks in order to keep pace with this exponential traffic growth. Thus, everything seems to indicate that fixed-grid Wavelength-Division Multiplexed (WDM) networks will be upgraded by adopting a flexible-grid, thus providing finer bandwidth allocation granularities, and therefore, increasing the Grade-of-Service by packing more information in the same spectral band of standard Single-Mode Fibers (SMFs). Nevertheless, unfortunately, the fundamental Shannon’s limit of SMFs is rapidly approaching, and, then, the research efforts to increase the SMFs' capacity will be useless. One solution to overcome this capacity crunch effect is to enable one extra dimension in addition to the frequency one, namely, the spatial dimension, thus deploying S parallel paths in order to multiply, in the best case, by S the capacity of SMF-based networks. However, additionally, it is necessary to decrease the cost and energy per bit in order to provide economically attractive solutions. For this purpose, a smooth upgrade path has to be carried out as new integrated devices and system components are developed for Space Division Multiplexing (SDM). This thesis is concentrated on the planning and operation of the combined flexible WDM and SDM networks (i.e., Flex-Grid/SDM networks) proposing several strategies aimed at optimizing network resources usage with hardware complexity analysis. For this purpose, firstly, network problems are carefully studied and stated, and then, mathematical and/or heuristic algorithms are designed and implemented in an optical network simulator. Specifically, after an introduction to the thesis, chapter 2 presents the background and related work. Next, chapter 3 concentrates on the study of spatially fixed Flex-Grid/SDM networks, i.e., when a rigid number of spatial channels are reserved per allocated traffic demand. In its turn, chapter 4 studies the case of Spectrally-Spatially Flexible Optical Networks (SS-FONs), as the ones providing the upper-bound network capacity. Costs and hardware requirements implied on providing this flexibility are analyzed. Network nodes aimed at reducing the cost of SS-FONs are presented and evaluated in chapter 5. Finally, this thesis ends with the presentation of the main contributions and future research work in chapter 6.La demanda de ancho de banda cada vez mĂĄs exigente para soportar servicios de telecomunicaciĂłn emergentes tales como la transmisiĂłn de video de alta calidad, computaciĂłn en la nube, vehĂ­culo conectado, realidad virtual/aumentada, etc.
, ha puesto de manifiesto la necesidad de actualizar constantemente la tecnologĂ­a detrĂĄs de las redes de transporte Ăłptico con la finalidad de ir a la par de este incremento exponencial del trĂĄfico. De esta manera, todo parece indicar que las redes basadas en la multiplexaciĂłn por division de longitud de onda (Wavelength Division Multiplexing, WDM) de ancho espectral fijo serĂĄn actualizadas adoptando un ancho de banda espectral flexible, que ofrece asignaciones de ancho de banda con granularidad mĂĄs fina acorde a las demandas de trĂĄfico; y por lo tanto, incremanta el Grado de Servicio de la red, ya que se permite acomodar mayor informaciĂłn en la misma banda espectral de las fibras monomodo (Single Mode Fibers, SMFs). Sin embargo, desafortunadamente, el lĂ­mite de Shannon de las fibras monomodo se estĂĄ aproximando cada vez mĂĄs, y cuando esto ocurra las investigaciones para incrementar la capacidad de las fibras monomodo serĂĄn infructuosas. Una posible soluciĂłn para superar este colapso de las fibras monomodo es habilitar la dimensiĂłn espacial a mĂĄs de la frecuencial, desplegando ïżœ caminos paralelos con la finalidad de multiplicar por ïżœ (en el mejor de los casos) la capacidad de las fibras monomodo. No obstante, es necesario disminuir el costo y la energĂ­a por bit con la finalidad de proveer soluciones comerciales atractivas. Para tal propĂłsito debe llevarse a cabo una actualizaciĂłn moderada conforme nuevos dispositivos y componentes integrados son desarrollados para la implementaciĂłn de la tecnologĂ­a basada en la multiplexaciĂłn por divisiĂłn de espacio (Space Division Multiplexing, SDM). Esta tesis se concentra en la planificaciĂłn y operaciĂłn de la combinaciĂłn de las redes WDM flexibles y SDM (es decir, de las redes Flex-Grid/SDM) proponiendo varias estrategias dirigidas a optimizar el uso de los recursos de red junto con el anĂĄlisis de la complejidad del hardware que viene acompañada. Para este fin, primeramente, los problemas de red son cuidadosamente estudiados y descritos. A continuaciĂłn, se han diseñado e implementado algoritmos basados en programaciĂłn lineal entera o heurĂ­sticas en un simulador de redes Ăłpticas. DespuĂ©s de una introducciĂłn inicial, el capĂ­tulo 2 de esta tesis presenta el marco teĂłrico sobre los conceptos tratados y los trabajos publicados anteriormente. A continuaciĂłn, el capĂ­tulo 3 se concentra en el estudio de las redes Flex-Grid/SDM con la dimensiĂłn espacial rĂ­gida; es decir, cuando un nĂșmero fijo de canales espaciales son reservados por cada demanda de trĂĄfico establecida. Por su parte, el capĂ­tulo 4 estudia las redes Flex-Grid/SDM considerando flexibilidad tanto en el dominio espacial como espectral (Spectrally and Spatially Flexible Optical Networks, SS-FONs), las cuales proveerĂ­an la capacidad mĂĄxima de las redes SDM. Adicionalmente, los costos y requerimientos de hardware implicados en la provisiĂłn de esta flexibilidad son analizados. El capĂ­tulo 5 presenta la evaluaciĂłn de nodos orientados a reducir los costos de las SS-FONs. Finalmente, el capĂ­tulo 6 expone las principales contribuciones y las posibles lĂ­neas de trabajo futuroEls requisits incessants d’ample de banda per al suport de nous serveis de telecomunicaciĂł, com poden ser la difusiĂł en directe de vĂ­deo de molt alta definiciĂł, la informĂ tica en el nĂșvol, els cotxes intel·ligents connectats a la xarxa, la realitat virtual/augmentada, etc
, han exigit una millora contĂ­nua de les tecnologĂ­es de les actuals xarxes de transport de dades. Tot sembla indicar que les xarxes de transport ĂČptiques actuals, basades en la tecnologia de multiplexaciĂł per divisiĂł de longitud d’ona (Wavelength Division Multiplexing, WDM) sobre un grid espectral rĂ­gid, hauran de ser reemplaçades per tecnologies ĂČptiques mĂ©s flexibles, amb una granularitat mĂ©s fina a l’hora de suportar noves connexions, incrementat el grau de servei de les xarxes grĂ cies a aprofitament major de l’ample de banda espectral proporcionat per les fibres ĂČptiques monomode (Single Mode Fibers, SMFs). Tanmateix, estem exhaurint ja la capacitat mĂ xima de les fibres ĂČptiques SMF segons ens indica el lĂ­mit fonamental de Shannon. Per tant, qualsevol esforç enfocat a millorar la capacitat d’aquestes xarxes basades en SMFs pot acabar sent infructuĂłs. Una possible soluciĂł per superar aquestes limitacions de capacitat Ă©s explorar la dimensiĂł espacial, a mĂ©s de l’espectral, desplegant camins en paral·lel per tal de multiplicar per , en el millor cas, la capacitat de les SMFs. Tot i aixĂČ, Ă©s necessari reduir el cost i el consum energĂštic per bit transmĂšs, per tal de proporcionar solucions econĂČmicament viables. Amb aquest propĂČsit, pot ser necessĂ ria una migraciĂł progressiva, a mesura que es desenvolupen nous dispositius i components per aquesta nova tecnologia de multiplexaciĂł per divisiĂł espacial (Spatial Division Multiplexing, SDM). La present tesi es centra en la planificaciĂł i operaciĂł de xarxes ĂČptiques de nova generaciĂł que combinin tecnologies de xarxa WDM flexible i SDM (Ă©s a dir, xarxes Flex-Grid/SDM), proposant estratĂšgies per a l’optimitzaciĂł de l’Ășs dels recursos de xarxa i, en definitiva, el seu cost (CapEx). Amb aquest propĂČsit, s’analitzen en primer moment els problemes adreçats. Tot seguit, es dissenyen algorismes per tal de solucionar-los, basats en tĂšcniques de programaciĂł matemĂ tica i heurĂ­stiques, els quals s’implementen i es proven en un simulador de xarxa ĂČptica. DesprĂ©s d’una introducciĂł inicial, el capĂ­tol 2 d’aquesta tesi presenta tots els conceptes tractats i treballs relacionats publicats amb anterioritat. Tot seguit, el capĂ­tol 3 es centra en l’estudi de les xarxes Flex-Grid/SDM fixes en el domini espai, Ă©s a dir, on sempre es reserva un nombre rĂ­gid de canals espacials per qualsevol demanda suportada. El capĂ­tol 4 estudia les xarxes flexibles en els dominis espectrals i espacials (Spectrally-Spatially Flexible Optical Nextworks, SS-FONs), com aquelles que poden proporcionar una capacitat de xarxa mĂ xima. En aquest context, s’analitzen els requeriments en termes de cost i hardware per tal de proporcionar aquesta flexibilitat. Llavors, en el capĂ­tol 6 es presenten opcions de node de xarxa capaces de reduir els costos de les xarxes SS-FONs. Finalment, en el capĂ­tol 7 es repassen totes les contribucions de la tesi, aixĂ­ com posibles lĂ­nies de treball futu

    Particle swarm optimization for routing and wavelength assignment in next generation WDM networks.

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    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 swarm‘s 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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