La ràpida evolució d’Internet i l’àmplia gamma de noves aplicacions (per exemple, multimèdia, videoconferència, jocs en línia, etc.) ha fomentat canvis revolucionaris en la manera com ens comuniquem. A més, algunes d’aquestes aplicacions demanden grans quantitats de recursos d’ample de banda amb diversos requeriments de qualitat de servei (QoS). El desenvolupament de la multiplexació per divisió de longitud d’ona (WDM) en els anys noranta va fer molt rendible la disponibilitat d’ample de banda. Avui dia, les tecnologies de commutació òptica de circuits són predominants en el nucli de la xarxa, les quals permeten la configuració de canals (lightpaths) a través de la xarxa. No obstant això, la granularitat d’aquests canals ocupa tota la longitud d’ona, el que fa que siguin ineficients per a proveir canals de menor ample de banda (sub-longitud d’ona). Segons la comunitat científica, és necessari augmentar la transparència dels protocols, així com millorar l’aprovisionament d’ample de banda de forma dinàmica. Per tal de fer això realitat, és necessari desenvolupar noves arquitectures. La commutació òptica de ràfegues i de paquets (OBS/OPS), són dues de les tecnologies proposades. Aquesta tesi contribueix amb tres arquitectures de xarxa destinades a millorar el transport de dades sub-longitud d’ona. En primer lloc, aprofundim en la naturalesa sense connexió en OBS. En aquest cas, la xarxa incrementa el seu dinamisme a causa de les transmissions a ràfega. A més, les col·lisions entre ràfegues degraden el rendiment de la xarxa fins i tot a càrregues molt baixes. Per fer front a aquestes col·lisions, es proposa un esquema de resolució de col·lisions pro actiu basat en un algorisme d’encaminament i assignació de longitud d’ona (RWA) que balanceja de forma automàtica i distribuïda la càrrega en la xarxa. En aquest protocol, el RWA i la transmissió de ràfegues es basen en l’explotació i exploració de regles de commutació que incorporen informació sobre contencions i encaminament. Per donar suport a aquesta arquitectura, s’utilitzen dos tipus de paquets de control per a l’encaminament de les ràfegues i l’actualització de les regles de commutació, respectivament. Per analitzar els beneficis del nou algorisme, s’utilitzen quatre topologies de xarxa diferents. Els resultats indiquen que el mètode proposat millora en diferents marges la resta d’algorismes RWA en funció de la topologia i sense penalitzar altres paràmetres com el retard extrem a extrem. La segona contribució proposa una arquitectura híbrida sense i orientada a connexió sobre la base d’un protocol de control d’accés al medi (MAC) per a xarxes OBS (DAOBS). El MAC ofereix dos mètodes d’accés: arbitratge de cua (QA) per a la transmissió de ràfegues sense connexió, i pre-arbitratge (PA) per serveis TDM orientats a connexió. Aquesta arquitectura permet una àmplia gamma d’aplicacions sensibles al retard i al bloqueig. Els resultats avaluats a través de simulacions mostren que en l’accés QA, les ràfegues de més alta prioritat tenen garantides zero pèrdues i latències d’accés molt baixes. Pel que fa a l’accés PA, es reporta que la duplicació de la càrrega TDM augmenta en més d’un ordre la probabilitat de bloqueig, però sense afectar en la mateixa mesura les ràfegues sense connexió. En aquest capítol també es tracten dos dels problemes relacionats amb l’arquitectura DAOBS i el seu funcionament. En primer lloc, es proposa un model matemàtic per aproximar el retard d’accés inferior i superior com a conseqüència de l’accés QA. En segon lloc, es formula matemàticament la generació i optimització de les topologies virtuals que suporten el protocol per a l’escenari amb tràfic estàtic. Finalment, l’última contribució explora els beneficis d’una arquitectura de xarxa òptica per temps compartit (TSON) basada en elements de càlcul de camins (PCE) centralitzats per tal d’evitar col·lisions en la xarxa. Aquesta arquitectura permet garantir l’aprovisionament orientat a connexió de canals sub-longitud d’ona. En aquest capítol proposem i simulem tres arquitectures GMPLS/PCE/TSON. A causa del enfocament centralitzat, el rendiment de la xarxa depèn en gran mesura de l’assignació i aprovisionament de les connexions. Amb aquesta finalitat, es proposen diferents algorismes d’assignació de ranures temporals i es comparen amb les corresponents formulacions de programació lineal (ILP) per al cas estàtic. Per al cas de tràfic dinàmic, proposem i avaluem mitjançant simulació diferents heurístiques. Els resultats mostren els beneficis de proporcionar flexibilitat en els dominis temporal i freqüencial a l’hora d’assignar les ranures temporals. / The rapid evolving Internet and the broad range of new data applications (e.g., multimedia, video-conference, online gaming, etc.) is fostering revolutionary changes in the way we communicate. In addition, some of these applications demand for unprecedented amounts of bandwidth resources with diverse quality of service (QoS). The development of wavelength division multiplexing (WDM) in the 90's made very cost-effective the availability of bandwidth. Nowadays, optical circuit switching technologies are predominant in the core enabling the set up of lightpaths across the network. However, full-wavelength lightpath granularity is too coarse, which results to be inefficient for provisioning sub-wavelength channels. As remarked by the research community, an open issue in optical networking is increasing the protocol transparency as well as provisioning true dynamic bandwidth allocation at the network level. To this end, new architectures are required. Optical burst/packet switching (OBS/OPS) are two such proposed technologies under investigation. This thesis contributes with three network architectures which aim at improving the sub-wavelength data transport from different perspectives. First, we gain insight into the connectionless nature of OBS. Here, the network dynamics are increased due to the short-lived burst transmissions. Moreover, burst contentions degrade the performance even at very low loads. To cope with them, we propose a proactive resolution scheme by means of a distributed auto load-balancing routing and wavelength assignment (RWA) algorithm for wavelength-continuity constraint networks. In this protocol, the RWA and burst forwarding is based on the exploitation and exploration of switching rule concentration values that incorporate contention and forwarding desirability information. To support such architecture, forward and backward control packets are used in the burst forwarding and updating rules, respectively. In order to analyze the benefits of the new algorithm, four different network topologies are used. Results indicate that the proposed method outperforms the rest of tested RWA algorithms at various margins depending on the topology without penalizing other parameters such as end-to-end delay. The second contribution proposes a hybrid connectionless and connection-oriented architecture based on a medium access control (MAC) protocol for OBS networks (DAOBS). The MAC provides two main access mechanisms: queue arbitrated (QA) for connectionless bursts and pre-arbitrated (PA) for TDM connection-oriented services. Such an architecture allows for a broad range of delay-sensitive applications or guaranteed services. Results evaluated through simulations show that in the QA access mode highest priority bursts are guaranteed zero losses and very low access latencies. Regarding the PA mode, we report that doubling the offered TDM traffic load increases in more than one order their connection blocking, slightly affecting the blocking of other connectionless bursts. In this chapter, we also tackle two of the issues related with the DAOBS architecture and its operation. Firstly, we model mathematically the lower and upper approximations of the access delay as a consequence of the connectionless queue arbitrated access. Secondly, we formulate the generation of the virtual light-tree overlay topology for the static traffic case.

Orientador: Mauricio Ferreira Magalhães / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-08T01:20:28Z (GMT). No. of bitstreams: 1 Zuliani_LuizGustavo_M.pdf: 512812 bytes, checksum: cab94937633f70467669b12635e8ccb1 (MD5) Previous issue date: 2006 / Resumo: Redes totalmente ópticas (fotônicas) controladas por GMPLS (Generalized MultiProtocol Label Switching) são a promessa para lidar com o crescente volume de tráfego IP. Os protocolos de sinalização e roteamento GMPLS, principalmente OSPF (Open Shortest Path First) e RSVP (Resource ReSerVation Protocol), trabalham de tal modo que o cálculo da rota para circuitos ópticos não considera a disponibilidade de comprimentos de onda (labels). Esta solução não é ótima em termos do uso de recursos de rede e da probabilidade de bloqueio de novos circuitos. Para aprimorar este quadro, algoritmos RWA (Routing and Wavelength Assignment) mais eficientes poderiam ser usados para calcular a rota e o comprimento de onda simultaneamente. Estes algoritmos RWA necessitam conhecer a topologia óptica de um modo ainda não descrito pelas atuais especificações do protocolo OSPF. Esta dissertação propõe extensões de Engenharia de Tráfego para o protocolo OSPF para permitir que o plano de controle GMPLS se beneficie do uso de algoritmos RWA mais eficientes. Um protótipo foi desenvolvido e instalado em uma rede óptica emulada para verificar a praticabilidade da solução proposta baseado na sobrecarga de tráfego gerado no plano de controle / Abstract: GMPLS-controlled all-optical networks are the promise to handle the increasing volume of IP traffic. The GMPLS routing and signaling protocols, mainly OSPF and RSVP, work in such a way that the route calculation for optical circuits does not take into account the wavelength (label) availability. This is not optimal in terms of network resources usage and blocking probability of new circuits. To deal with this scenario, more efficient RWA algorithms could be used to calculate the route and the wavelength assignment at one time. These RWA engines need to know the optical topology in a way that is not described by current OSPF standards. This dissertation proposes Traffic Engineering extensions to the OSPF protocol to enable the GMPLS control plane to take advantage of the most effective RWA classes. A prototype was developed and deployed in an optical-emulated copper-based network to verify its feasibility based on the bandwidth overhead generated in the control plane / Mestrado / Engenharia de Computação / Mestre em Engenharia Elétrica

In the field of singularly perturbed reaction- or convection-diffusion boundary value problems the research area of a priori error analysis for the finite element method, has already been thoroughly investigated. In particular, for mesh adapted methods and/or various stabilization techniques, works have been done that prove optimal rates of convergence or supercloseness uniformly in the perturbation parameter epsilon. Commonly, however, it is assumed that the exact solution behaves nicely in that it obeys certain regularity assumptions although in general, e.g. due to corner singularities, these regularity requirements are not satisfied. So far, insufficient regularity has been met by assuming compatibility conditions on the data. The present thesis originated from the question: What can be shown if these rather unrealistic additional assumptions are dropped? We are interested in epsilon-uniform a priori estimates for convergence and superconvergence that include some regularity parameter that is adjustable to the smoothness of the exact solution. A major difficulty that occurs when seeking the numerical error decay is that the exact solution is not known. Since we strive for reliable rates of convergence we want to avoid the standard approach of the "double-mesh principle". Our choice is to use reference solutions as a substitute for the exact solution. Numerical experiments are intended to confirm the theoretical results and to bring further insights into the interplay between layers and singularities. To computationally realize the thereby arising demanding practical aspects of the finite element method, a new software is developed that turns out to be particularly suited for the needs of the numerical analyst. Its design, features and implementation is described in detail in the second part of the thesis.

The thesis "Credit risk from Basel II point of view" deals with new capital concept with main focus on the credit risk. The particular emphasis is laid on the chief issue of Basel II concept i.e. internal models. The thesis quite in detail describes the usage of basel parameters - LGD particularly - in various day-to-day business processes of credit institutions. An individual part of the thesis is devoted to credit risk mitigants and their impacts on the amount of capital requirements. The analysis carried out precedent Basel II implementation indicated the launching of Basel II should imply risk weighted assests to credit risk decline. This documents the last chapter.

A crescente demanda por largura de faixa e o aumento exponencial do número de usuários têm exercido enorme pressão sobre as redes de telecomunicações, exigindo constante melhoria de desempenho. A tecnologia fotônica tem sido capaz de atender a boa parte desta demanda, sendo a principal alternativa para transportar quantidades elevadas de tráfego. Por outro lado, tem havido um impressionante avanço tecnológico no setor de comunicação móvel celular, com destaque para os sistemas que utilizam o esquema de reuso de freqüências como principal tecnologia. Diante da demanda elevada, a alternativa usual de expandir os recursos proporcionalmente tem se mostrado inviável por causa do custo elevado. Assim, soluções eficientes para o problema de alocação de recursos e roteamento de tráfego (PARRT) tornaram-se uma necessidade imperiosa no projeto, expansão e gerenciamento de redes de telecomunicações. O PARRT pode ser modelado como um problema de otimização, geralmente não-polinomial, e as abordagens baseadas em algoritmo genético (AG) têm sido empregadas para solucionar esta classe de problemas para os quais as soluções heurísticas não são possíveis ou freqüentemente conduzem a resultados insatisfatórios. Nesta pesquisa, a abordagem escolhida para resolver o PARRT em redes ópticas e de comunicação móvel celular é baseada em AG. Estratégias adicionais foram incorporadas aos algoritmos propostos para aumentar a eficiência do correspondente AG canônico e proporcionar adaptação às mudanças ocorridas no ambiente investigado. A meta principal é a redução da probabilidade de bloqueio de solicitação de conexão. Em redes ópticas, o modelo proposto resolve o roteamento e a alocação de comprimentos de onda, determina a localização esparsa de conversores de comprimento de onda, limita o número de amplificadores em cascata, proporciona agregação dinâmica de tráfego e imparcialidade de capacidade de largura de faixa por meio de controle de admissão de conexão. Restrições de camada física como emissão espontânea amplificada e dispersão por modo de polarização são incluídas nos algoritmos. Em redes de comunicação móvel celular, os modelos propostos resolvem o problema de alocação de canais proporcionando baixos valores de probabilidade de bloqueio de novas chamadas e de handoff. Os algoritmos incluem o efeito simultâneo de três restrições eletromagnéticas: co-canal, canal-adjacente e co-site. Uma rede híbrida óptica e via satélite é também simulada para constatar a versatilidade dos algoritmos em gerenciar de forma integrada redes de naturezas distintas. Resultados numéricos apresentados demonstram a potencialidade dos algoritmos propostos para gerenciar recursos e rotear tráfego em redes de telecomunicações. / The growing demand for bandwidth together with the exponential increase in the numbers of users have exerted huge pressure on the telecommunication networks, requiring constant performance improvement. Photonic technology has been capable of attending a large amount of this demand, which makes it the main alternative in high traffic transport networks. On the other hand, a remarkable technological progress has occurred in the mobile cellular communications field, which employs frequency reuse as its key technology. The usual alternative of expanding the resources proportionally to the traffic demand has proved to be impractical due to the high cost involved. Thus, efficient solutions to traffic routing and resource allocation problem (TRRAP) became an imperative requirement in design, expansion and management of telecommunication networks. The TRRAP is an optimization problem, generally non-polynomial (NP), that can be successfully modeled with genetic algorithm (GA) as opposed to heuristic solutions, since the later is either not applied or frequently lead to unsatisfactory results. In this research, the elected approach to solve the TRRAP in both optical and cellular mobile communication network is based on GA. Complementary strategies were incorporated to the algorithms to increase the efficiency of the corresponding canonical GA. Additionally, the strategies adopted provide robustness to the GA adaptation against the changes in the investigated environment. The main goal of the proposed GA is the reduction of request-connection blocking probability. The proposed approach is capable of handling the following tasks in WDM optical networks: routing and wavelength assignment (RWA) optimization, sparse wavelength converters arrangement, limitation of the number of cascade amplifiers, dynamic traffic grooming, and bandwidth capacity fairness through connection admission control (CAC) procedure. Physical layer constraints such as amplified spontaneous emission (ASE) and polarization mode dispersion (PMD) are also taken into account. Two algorithms are proposed to solve the channel assignment problem (CAP) in cellular mobile communication networks, providing low values of blocking probability for new calls and handoff. The algorithms include the simultaneous effect of three electromagnetic constraints: cochannel, adjacent channel and cosite. A hybrid optical and wireless network is also simulated to evidence the versatility of the proposed algorithm in managing integrated networks from distinct natures. The numerical results presented throughout this work demonstrate the potentiality of the proposed algorithms in managing resources and providing traffic routing in telecommunication networks.

A crescente demanda por largura de faixa e o aumento exponencial do número de usuários têm exercido enorme pressão sobre as redes de telecomunicações, exigindo constante melhoria de desempenho. A tecnologia fotônica tem sido capaz de atender a boa parte desta demanda, sendo a principal alternativa para transportar quantidades elevadas de tráfego. Por outro lado, tem havido um impressionante avanço tecnológico no setor de comunicação móvel celular, com destaque para os sistemas que utilizam o esquema de reuso de freqüências como principal tecnologia. Diante da demanda elevada, a alternativa usual de expandir os recursos proporcionalmente tem se mostrado inviável por causa do custo elevado. Assim, soluções eficientes para o problema de alocação de recursos e roteamento de tráfego (PARRT) tornaram-se uma necessidade imperiosa no projeto, expansão e gerenciamento de redes de telecomunicações. O PARRT pode ser modelado como um problema de otimização, geralmente não-polinomial, e as abordagens baseadas em algoritmo genético (AG) têm sido empregadas para solucionar esta classe de problemas para os quais as soluções heurísticas não são possíveis ou freqüentemente conduzem a resultados insatisfatórios. Nesta pesquisa, a abordagem escolhida para resolver o PARRT em redes ópticas e de comunicação móvel celular é baseada em AG. Estratégias adicionais foram incorporadas aos algoritmos propostos para aumentar a eficiência do correspondente AG canônico e proporcionar adaptação às mudanças ocorridas no ambiente investigado. A meta principal é a redução da probabilidade de bloqueio de solicitação de conexão. Em redes ópticas, o modelo proposto resolve o roteamento e a alocação de comprimentos de onda, determina a localização esparsa de conversores de comprimento de onda, limita o número de amplificadores em cascata, proporciona agregação dinâmica de tráfego e imparcialidade de capacidade de largura de faixa por meio de controle de admissão de conexão. Restrições de camada física como emissão espontânea amplificada e dispersão por modo de polarização são incluídas nos algoritmos. Em redes de comunicação móvel celular, os modelos propostos resolvem o problema de alocação de canais proporcionando baixos valores de probabilidade de bloqueio de novas chamadas e de handoff. Os algoritmos incluem o efeito simultâneo de três restrições eletromagnéticas: co-canal, canal-adjacente e co-site. Uma rede híbrida óptica e via satélite é também simulada para constatar a versatilidade dos algoritmos em gerenciar de forma integrada redes de naturezas distintas. Resultados numéricos apresentados demonstram a potencialidade dos algoritmos propostos para gerenciar recursos e rotear tráfego em redes de telecomunicações. / The growing demand for bandwidth together with the exponential increase in the numbers of users have exerted huge pressure on the telecommunication networks, requiring constant performance improvement. Photonic technology has been capable of attending a large amount of this demand, which makes it the main alternative in high traffic transport networks. On the other hand, a remarkable technological progress has occurred in the mobile cellular communications field, which employs frequency reuse as its key technology. The usual alternative of expanding the resources proportionally to the traffic demand has proved to be impractical due to the high cost involved. Thus, efficient solutions to traffic routing and resource allocation problem (TRRAP) became an imperative requirement in design, expansion and management of telecommunication networks. The TRRAP is an optimization problem, generally non-polynomial (NP), that can be successfully modeled with genetic algorithm (GA) as opposed to heuristic solutions, since the later is either not applied or frequently lead to unsatisfactory results. In this research, the elected approach to solve the TRRAP in both optical and cellular mobile communication network is based on GA. Complementary strategies were incorporated to the algorithms to increase the efficiency of the corresponding canonical GA. Additionally, the strategies adopted provide robustness to the GA adaptation against the changes in the investigated environment. The main goal of the proposed GA is the reduction of request-connection blocking probability. The proposed approach is capable of handling the following tasks in WDM optical networks: routing and wavelength assignment (RWA) optimization, sparse wavelength converters arrangement, limitation of the number of cascade amplifiers, dynamic traffic grooming, and bandwidth capacity fairness through connection admission control (CAC) procedure. Physical layer constraints such as amplified spontaneous emission (ASE) and polarization mode dispersion (PMD) are also taken into account. Two algorithms are proposed to solve the channel assignment problem (CAP) in cellular mobile communication networks, providing low values of blocking probability for new calls and handoff. The algorithms include the simultaneous effect of three electromagnetic constraints: cochannel, adjacent channel and cosite. A hybrid optical and wireless network is also simulated to evidence the versatility of the proposed algorithm in managing integrated networks from distinct natures. The numerical results presented throughout this work demonstrate the potentiality of the proposed algorithms in managing resources and providing traffic routing in telecommunication networks.

Η πρόσφατη τεχνολογική ανάπτυξη των οπτικών ενισχυτών, πολυπλεκτών/αποπλεκτών, οπτικών διακοπτών καθώς και άλλων οπτικών συσκευών μας οδηγεί στο να ελπίζουμε ότι σύντομα στο μέλλον θα υλοποιηθεί ένα πλήρες οπτικό (all optical), WDM (wavelength division multiplexing) δίκτυο που να ικανοποιεί και την ανάγκη για μεγάλα μεγέθη χωρητικότητας. Σε ένα τέτοιο δίκτυο η μετατροπή του οπτικού σήματος σε ηλεκτρονικό και εκ νέου στο οπτικό (ΟΕΟ) δεν θα χρησιμοποιείται στους ενδιάμεσους κόμβους, και αυτό συμβάλει σε οικονομικότερες υλοποιήσεις των οπτικών δικτύων. Σε ένα WDM δρομολογούμενο δίκτυο, τα δεδομένα μεταφέρονται μέσω ενός οπτικού καναλιού, lightpath, στους κόμβους του δικτύου που συνδέονται με οπτικές ίνες. Στις πλείστες των περιπτώσεων, κατά την άφιξη ενός lightpath σε κάποιο κόμβο, εφαρμόζεται σε αυτό οπτικό-ηλεκτρονική μετατροπή και αντίστροφα, ούτως ώστε το σήμα να αναδημιουργηθεί λόγω των απωλειών που υπέστη κατά την μεταφορά, ή ακόμη για να αναλυθεί από ενδιάμεσες ηλεκτρονικές συσκευές. Στα μη πλήρη οπτικά δίκτυα, η μεταφορά των δεδομένων γίνεται από κόμβο σε κόμβο κατά μήκος του δικτύου, ούτως ώστε το οπτικό σήμα να ενισχύεται και να αναγεννάτε μέσω της OEO επεξεργασίας. Παρ’ όλα αυτά, η κάθε ενδιάμεση ανάλυση του θέματος σε ένα τέτοιο δίκτυο προϋποθέτει πολύ μεγάλα κόστη λόγω των πολλών συσκευών που απαιτούνται για τη OEO επεξεργασία. Το γεγονός αυτό μας οδηγεί στα ημί-πλήρη δίκτυα όπου η ενίσχυση και αναγέννηση του θέματος δε γίνεται σε όλους τους ενδιάμεσους κόμβους αλλά σε μερικούς από αυτούς. Ο τελικός στόχος όμως είναι η απαλοιφή της ηλεκτρονικής μετατροπής και αυτό οδηγεί στην υλοποίηση των πλήρως οπτικών δικτύων. Στα πλήρη οπτικά δίκτυα, ένα σήμα που μεταδίδεται παραμένει, για όλο το lightpath, στο οπτικό επίπεδο. Έτσι, το πλήρες οπτικό δίκτυο μπορεί να απαλείψει την ασύμφορη OEO μετατροπή. Η αναζήτηση των κατάλληλων μονοπατιών με τα κατάλληλα μήκη κύματος που θα ικανοποιούσε ένα πλήρες οπτικό δίκτυο το οποίο δρομολογείται από ligthpaths, ονομάζεται Routing and Wavelength Assignment (RWA) και αποτελεί ένα από τα σημαντικότερα ζητήματα για το σωστό σχεδιασμό των οπτικών δικτύων τέτοιου είδους. Το πρόβλημα γίνεται ιδιαίτερα πολύπλοκο όταν στην τελική απόφαση θα πρέπει να συμπεριληφθούν και τα χαρακτηριστικά του φυσικού επιπέδου του δικτύου, όπως εξασθένιση του σήματος, μη γραμμικά φαινόμενα, διασπορά κ.ά, η συμβολή των οποίων στην τελική δρομολόγηση δεν θεωρείται αμελητέα (Impairment Aware Routing and Wavelength Assignment, ΙΑ-RWA). Σε αυτή την εργασία μελετάται το RWA πρόβλημα και προτείνεται ένας μονού στόχου γενετικός αλγόριθμος (Single Objective Genetic Algorithm - SOGA), ο οποίος επιλύει ικανοποιητικά το πρόβλημα θεωρώντας στατική κίνηση. Επιπλέον τονίζεται η σημασία των φυσικών παραμέτρων του προβλήματος και πως αυτές επηρεάζουν την απόδοση του πλήρους οπτικού δικτυου. Στη συνέχεια προτείνεται ένας νέος, πολλαπλών στόχων γενετικός αλγόριθμος (multi objective genetic algorithm – MOGA) ο οποίος βελτιστοποιεί τις λύσεις του προβλήματος ικανοποιητικά λαμβάνοντας ταυτόχρονα υπόψη, με έμμεσο τρόπο, και τις φυσικές παραμέτρους. Επίσης προτείνεται και ένας μονού στόχου γενετικός αλγόριθμος οποίος χρησιμοποιεί ένα εργαλείο αποτίμηση της ποιότητας μετάδοσης (Q-TOOL) σαν μέτρο κατά τη διαδικασία εύρεσης ικανοποιητικής λύσης. Το υπόλοιπο της εργασίας οργανώνεται ως ακολούθως: Στην ενότητα 2 παρουσιάζεται μια σύντομη αναφορά στα WDM δίκτυα καθώς και η περιγραφή του RWA και IA-RWA προβλήματος, ενώ στην ενότητα 3 παρουσιάζεται η πρόταση επίλυσης του RWA προβληματος με τη χρήση γενετικών αλγορίθμων. Ακολουθεί στην ενότητα 4 η πρότασή μας για επίλυση του IA-RWA προβλήματος με τη χρήση Multi-objective διαδικασιών βελτιστοποίησης, καθώς και η βελτιστοποίηση του προβλήματος με τη χρήση του Q-TOOL. Τέλος στην ενότητα 5 συνοψίζουμε την εργασία και παρουσιάζουμε τα συμπεράσματα. / The recent development of optical amplifiers, multiplexers / de-multiplexers, optical switches and other optical devices leads us to hope that soon in future all optical, WDM (wavelength division multiplexing) networks will be implemented which that will satisfy the needs for large capacity. In such networks a viable conversion of the optical -> Electronic and back to optical (OEO) will not be used at intermediate nodes, and this will contribute to efficient and economical implementation. The search for the appropriate paths with the appropriate wavelengths that meet the requirement in all optical networks is called Routing and Wavelength Assignment (RWA) and is one of the most important issues for proper design of such optical networks. The problem becomes particularly complex when the final decision should include the characteristics of the physical layer of the network, such as attenuation of the signal, nonlinear effects, dispersion, etc., whose contribution to the final result is not considered negligible (Impairment Aware Routing and Wavelength Assignment,IA-RWA). This work studies the RWA problem considering static traffic, and proposes a single-objective genetic algorithm (Single Objective Genetic Algorithm - SOGA), which resolves the problem satisfactorily. Furthermore the work stresses the importance of physical parameters of the problem and how these affect the performance of the all optical networks, and proposes a new, multi-objective genetic algorithm (MOGA) which optimizes the solution of IA-RWA problem adequately taking into account indirectly, and the physical impairments that affect the quality of the signal. In addition, a single objective genetic algorithm is proposed that uses a tool to assess the quality of the transmission signal (Q-TOOL), as a benchmark, in the process of optimization of the solution to the IA-RWA problem.

La croissance continue du trafic Internet implique une augmentation de la consommation d'énergie en raison des nombreuses conversions optique à électronique(OEO) requises par les routeurs et les commutateurs. L'utilisation de réseaux transparents pourraient freiner cette croissance incontrôlée, mais le maintien des données dans le domaine optique a deux conséquences néfastes: une accumulation du bruit et des non-linéarités de l'amplification qui dégrade fortement les performances au niveau de la couche physique. et la contrainte de continuité de longueur d'onde (WCC) reflétant la conservation de la longueur d'onde du signal optique dans les réseaux optiques multiplexés en longueur d'onde (WDM) qui dégradent les performances du réseau, notamment sa probabilité de blocage. Les convertisseurs de longueur d'onde (WC) peuvent pallier la contrainte WCC, mais les seuls dispositifs suffisamment matures disponibles dans le commerce sont les WC basés sur OEO (OEO-WC). Cependant, leur coût augmente avec les débits binaires. D'autre part, des convertisseurs de longueur d'onde tout optique (AO-WC) ont été démontrés dans des laboratoires de recherche, avec toutefois une plage de conversion limitée et une dégradation du signal converti.Dans cette thèse, nous concevons la couche de transmission en utilisant deux ensembles de formats de modulation différents avec des plages de débits différentes; et par conséquent différents modèles d'estimation de performance. Au niveau du réseau, nos analyses montrent que la contribution des WC dépend des demandes de trafic servant à l’ordre dans un scénario de planification du réseau; qu'en utilisant des algorithmes fixed-alternate-routing (FAR) ou least-loaded-routing (LLR) et un algorithme d'affectation de longueur d'onde first-fit (FF), les AO-WCs offrent les mêmes améliorations de performances que les OEO-WC. De plus, nous identifions une plage de conversion et une cascadabilité optimale d’AO-WC qui montre que le LLR nécessite un nombre de conversions par canal inférieur au FAR. / The continuous growth of Internet traffic implies an increased power consumption due to the many optical-to-electronic (OEO) conversions required by routers and switches. Transparent networks could curb this uncontrolled growth, but keeping the data in the optical domain has two adverse consequences: physical layer impairments accumulation which strongly degrades the performance due to amplication noise and non-linearities; and the wavelength continuity constraint (WCC) to keep the opticalsignal's wavelength unchanged in wavelength-division-multiplexed (WDM) optical networks which degrades network blocking performance. Wavelength converters (WCs) can alleviate the WCC constraint, but the only commercially available devices are the OEO-based WCs (OEO-WCs), however, their cost increases with bit-rates. On the other hand, all-optical wavelength converters (AO-WCs) have been demonstrated in research laboratories albeit with a limited conversion range and a performance that degrades converted signal's quality.In this thesis, we design the transmission layer using two different modulation formats sets with different bit-rates ranges; and consequently different performance estimation models. At the network level, our analyses show that WCs' contribution depends on traffic demands serving ordering in the online traffic assumption; that using xed-alternate routing (FAR) or least-loaded routing (LLR) algorithms and first-fit (FF) wavelength assignment algorithm, AO-WCs give the same performance enhancement as OEO-WCs. Moreover, we identify an optimum AO-WC conversion range and cascadability which shows that LLR requires lower number of conversions per channel compared to FAR.