46 research outputs found
Allocation des ressources et des solutions pour économiser de l'énergie dans les réseaux optiques d'accès
In this thesis, general overview about PON systems is presented and existing PON mechanisms and classification are investigated. After, a novel dynamic bandwidth allocation algorithm for EPON is introduced. This proposed algorithm is named as “Half Cycling Dynamic Bandwidth Allocation-hcDBA” by the inspiration of its half cycling processing mode. Later, an improvement of hcDBA algorithm with early prediction mechanism is presented. As a result statement of the study, hcDBA algorithm performs better than existing mechanism in terms of packet loss ratio and access delays. Beside, simulation traffic behavior of EPON’s upstream channel has been investigated in order to support the decision of selecting suitable traffic generator in further studies. Energy conversation is one of the hot topics in telecommunication networks. Access networks constitute remarkable portion of the total energy consumption in telecommunication networks. ITU-T and IEEE organizations published recommendation for energy conversation in PONs. While, total energy consumption of ONUs is more than other equipment in fix access network the standards and most of the researches focused on saving energy at ONU side. In this thesis I focused on an energy efficiency method based on energy conversation on OLT side. The proposed method save energy by dynamically moving OLT cards to deep sleep mode according to the incoming and outgoing traffic loadsDans ce travail de thèse, un aperçu général sur les systèmes PON est présenté et sont étudiés les mécanismes et classification PON existants. Après, nous introduisons notre première contribution qui est un algorithme d'allocation dynamique de bande passante pour EPON. Cet algorithme proposé est désigné comme «hcDBA». Par la suite, une amélioration de l'algorithme de hcDBA avec mécanisme de prédiction précoce est présentée. Notre simulation montre bien que notre algorithme hcDBA est performant comparé aux mécanismes existants en termes de taux de perte de paquets et de délai d’accès. Dans notre seconde contribution, nous sommes intéressés au problème de consommation d’énergie qui est un sujet d’actualité dans les réseaux de télécommunication. Les études montrent aujourd’hui que les réseaux d'accès constituent une partie remarquable de la consommation totale d'énergie dans les réseaux de télécommunication. Les organisations ITU-T et IEEE ont publié la recommandation pour la conversation de l'énergie pour les réseaux PONs. Bien que, la consommation totale d'énergie des nœuds ONU est plus importantes que d'autres équipements dans le réseau d'accès fixe, les normes et la plupart des travaux de recherches ont porté sur les économies d'énergie du côté de ONU. Dans cette thèse, nous sommes concentrés sur une méthode d'efficacité énergétique basée sur la conservation de l'énergie du côté de l’OLT. La méthode proposée permet d’économiser de l'énergie en déplaçant dynamiquement des cartes d’OLT en mode de sommeil profond en fonction des charges de trafic entrant et sortan
Space programs summary no. 37-66, volume 3 for the period 1 October - 30 November 1970. Supporting research and advanced development
Research studies on development of Thermoelectric Outer Planet Spacecraft /TOPS/ and lunar exploratio
Design and cost performance of WDM pons for multi-wavelength users
Die rasante Verbreitung des Internet fĂĽhrt zu einem steigenden Bedarf an
höheren Bitraten in Telekommunikationsnetzwerken. Dieser kann derzeit nur
mit optischen Netzwerken erfĂĽllt werden, insbesondere mit der
Wellen¬längen¬multiplex-Technik (WDM). Viele Forschungsergebnisse weisen
darauf hin, dass WDM Passive Optische Netzwerke (PON) die nächste
Generation der optischen Zugangsnetze darstellen. Die
Wellenlängenmultiplex-Technik beruht darauf, dass mehrere optische Kanäle
mit niedrigen Bitraten ĂĽber eine Faser ĂĽbertragen werden und so ein WDM
Signal mit hoher Bitrate erzeugen. Ziel dieser Arbeit ist die
Identifizierung von neuen Architekturen, welche jedem Benutzer und jedem
Dienst mindestens eine Wellenlänge zur Verfügung stellen. Neue Methoden und
Modelle zur Berechnung von ein- und mehrstufigen WDM PONs werden
eingefĂĽhrt. Um alle technologisch realisierbaren ein- und mehrstufigen WDM
PONs zu berechnen und zu analysieren wurde ein Design Tool entwickelt. FĂĽr
einen flächendeckenden kommerziellen Einsatz reicht es nicht aus,
funktionierende Technologien anzubieten, vielmehr müssen ökonomische
Über¬legungen miteinbezogen werden. Diese Arbeit ermöglicht einen Vergleich
unterschiedlicher Architekturen hinsichtlich ihrer Wirtschaftlichkeit und
zielt darauf ab, jene Architekturen zu identifizieren, welche kostenoptimal
sind. Neue kosten¬optimale Netzwerk-Architekturen führen zu einer
schnelleren Marktpenetration und dazu, Fiber-to-the-Home (FTTH) Realität
werden zu lassen.Due to the incomparable popularity of the Internet, the already enormous
and still rocketing bandwidth demand may only be satisfied by optical
networks, particularly by using the Wavelength Division Multiplexing (WDM)
technology. In many research labs, WDM Passive Optical Networks (PON)
access networks are considered as the next generation optical access. To
obtain WDM signals with high bit rates, multiple channels operating at a
lower transmission speed can be supported on a single optical fiber. The
subject of this thesis will be engineering new cutting edge architectures
offering each user and service at least one wavelength. New techniques and
models are introduced to design single and multistage WDM PONs. A design
tool was implemented to analyze all technologically feasible single and
multistage WDM PON architectures. During real deployments, the technology
has worked but the economic factors have proven to be too costly. Thus, it
is important to examine these economic aspects. The objective is to
identify those architectures that minimize costs. Access to these newly
identified network architectures will prompt market introduction as well as
market penetration helping Fiber-to-the-Home (FTTH) to become reality
Economically sustainable public security and emergency network exploiting a broadband communications satellite
The research contributes to work in Rapid Deployment of a National Public Security and Emergency Communications Network using Communication Satellite Broadband. Although studies in Public Security Communication networks have examined the use of communications satellite as an integral part of the Communication Infrastructure, there has not been an in-depth design analysis of an optimized regional broadband-based communication satellite in relation to the envisaged service coverage area, with little or no terrestrial last-mile telecommunications infrastructure for delivery of satellite solutions, applications and services.
As such, the research provides a case study of a Nigerian Public Safety Security Communications Pilot project deployed in regions of the African continent with inadequate terrestrial last mile infrastructure and thus requiring a robust regional Communications Satellite complemented with variants of terrestrial wireless technologies to bridge the digital hiatus as a short and medium term measure apart from other strategic needs.
The research not only addresses the pivotal role of a secured integrated communications Public safety network for security agencies and emergency service organizations with its potential to foster efficient information symmetry amongst their operations including during emergency and crisis management in a timely manner but demonstrates a working model of how analogue spectrum meant for Push-to-Talk (PTT) services can be re-farmed and digitalized as a “dedicated” broadband-based public communications system. The network’s sustainability can be secured by using excess capacity for the strategic commercial telecommunication needs of the state and its citizens. Utilization of scarce spectrum has been deployed for Nigeria’s Cashless policy pilot project for financial and digital inclusion. This effectively drives the universal access goals, without exclusivity, in a continent, which still remains the least wired in the world
ATS F and G /phases B and C/, volume 1 Final report
Design parameters and program objectives of Applications Technology Satellites 7 and
Space programs summary no. 37-45, volume IV FOR the period April 1, 1967 to May 31, 1967. Supporting research and advanced development
Space exploration projects on systems, guidance and control, environmental simulation, space sciences, propulsion, telecommunications, and engineering mechanic
Mechanical systems readiness assessment and performance monitoring study
The problem of mechanical devices which lack the real-time readiness assessment and performance monitoring capability required for future space missions is studied. The results of a test program to establish the feasibility of implementing structure borne acoustics, a nondestructive test technique, are described. The program included the monitoring of operational acoustic signatures of five separate mechanical components, each possessing distinct sound characteristics. Acoustic signatures were established for normal operation of each component. Critical failure modes were then inserted into the test components, and faulted acoustic signatures obtained. Predominant features of the sound signature were related back to operational events occurring within the components both for normal and failure mode operations. All of these steps can be automated. The structure borne acoustics technique lends itself to reducing checkout time, simplifying maintenance procedures, and reducing manual involvement in the checkout, operation, maintenance, and fault diagnosis of mechanical systems