117 research outputs found
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
Dynamic Optical Networks for Data Centres and Media Production
This thesis explores all-optical networks for data centres, with a particular focus on network designs for live media production. A design for an all-optical data centre network is presented, with experimental verification of the feasibility of the network data plane. The design uses fast tunable (< 200 ns) lasers and coherent receivers across a passive optical star coupler core, forming a network capable of reaching over 1000 nodes. Experimental transmission of 25 Gb/s data across the network core, with combined wavelength switching and time division multiplexing (WS-TDM), is demonstrated. Enhancements to laser tuning time via current pre-emphasis are discussed, including experimental demonstration of fast wavelength switching (< 35 ns) of a single laser between all combinations of 96 wavelengths spaced at 50 GHz over a range wider than the optical C-band. Methods of increasing the overall network throughput by using a higher complexity modulation format are also described, along with designs for line codes to enable pulse amplitude modulation across the WS-TDM network core. The construction of an optical star coupler network core is investigated, by evaluating methods of constructing large star couplers from smaller optical coupler components. By using optical circuit switches to rearrange star coupler connectivity, the network can be partitioned, creating independent reserves of bandwidth and resulting in increased overall network throughput. Several topologies for constructing a star from optical couplers are compared, and algorithms for optimum construction methods are presented. All of the designs target strict criteria for the flexible and dynamic creation of multicast groups, which will enable future live media production workflows in data centres. The data throughput performance of the network designs is simulated under synthetic and practical media production traffic scenarios, showing improved throughput when reconfigurable star couplers are used compared to a single large star. An energy consumption evaluation shows reduced network power consumption compared to incumbent and other proposed data centre network technologies
On-board B-ISDN fast packet switching architectures. Phase 1: Study
The broadband integrate services digital network (B-ISDN) is an emerging telecommunications technology that will meet most of the telecommunications networking needs in the mid-1990's to early next century. The satellite-based system is well positioned for providing B-ISDN service with its inherent capabilities of point-to-multipoint and broadcast transmission, virtually unlimited connectivity between any two points within a beam coverage, short deployment time of communications facility, flexible and dynamic reallocation of space segment capacity, and distance insensitive cost. On-board processing satellites, particularly in a multiple spot beam environment, will provide enhanced connectivity, better performance, optimized access and transmission link design, and lower user service cost. The following are described: the user and network aspects of broadband services; the current development status in broadband services; various satellite network architectures including system design issues; and various fast packet switch architectures and their detail designs
Radio Communications
In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modiïŹed our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the ïŹeld of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks
Analyse et optimisation des réseaux avioniques hétérogÚnes
La complexitĂ© des architectures de communication avioniques ne cesse de croĂźtre avec lâaugmentation du nombre des terminaux interconnectĂ©s et lâexpansion de la quantitĂ© des donnĂ©es Ă©changĂ©es. Afin de rĂ©pondre aux besoins Ă©mergents en terme de bande passante, latence et modularitĂ©, lâarchitecture de communication avionique actuelle consiste Ă utiliser le rĂ©seau AFDX (Avionics Full DupleX Switched Ethernet) pour connecter les calculateurs et utiliser des bus dâentrĂ©e/sortie (par exemple le bus CAN (Controller Area Network)) pour connecter les capteurs et les actionneurs. Les rĂ©seaux ainsi formĂ©s sont connectĂ©s en utilisant des Ă©quipements dâinterconnexion spĂ©cifiques, appelĂ©s RDC (Remote Data Concentrators) et standardisĂ© sous la norme ARINC655. Les RDCs sont des passerelles de communication modulaires qui sont reparties dans lâavion afin de gĂ©rer lâhĂ©tĂ©rogĂ©nĂ©itĂ© entre le rĂ©seau cĆur AFDX et les bus dâentrĂ©e/sortie. Certes, les RDCs permettent dâamĂ©liorer la modularitĂ© du systĂšme avionique et de rĂ©duire le coĂ»t de sa maintenance; mais, ces Ă©quipements sont devenus un des dĂ©fis majeurs durant la conception de lâarchitecture avionique afin de garantir les performances requises du systĂšme. Les implĂ©mentations existantes du RDC effectuent souvent une translation direct des trames et nâimplĂ©mentent aucun mĂ©canisme de gestion de ressources. Or, une utilisation efficace des ressources est un besoin important dans le contexte avionique afin de faciliter lâĂ©volution du systĂšme et lâajout de nouvelles fonctions. Ainsi, lâobjectif de cette thĂšse est la conception et la validation dâun RDC optimisĂ© implĂ©mentant des mĂ©canismes de gestion des ressources afin dâamĂ©liorer les performances de lâarchitecture de communication avionique tout en respectant les contraintes temporelles du systĂšme. Afin dâatteindre cet objectif, un RDC pour les architectures rĂ©seaux de type CAN-AFDX est conçu, intĂ©grant les fonctions suivantes: (i) groupement des trames appliquĂ© aux flux montants, i.e., flux gĂ©nĂ©rĂ©s par les capteurs et destinĂ©s Ă lâAFDX, pour minimiser le coĂ»t des communication sur lâAFDX; (ii) la rĂ©gulation des flux descendants, i.e., flux gĂ©nĂ©rĂ©s par des terminaux AFDX et destinĂ©s aux actionneurs, pour rĂ©duire les contentions sur le bus CAN. Par ailleurs, notre RDC permet de connecter plusieurs bus CAN Ă la fois tout en garantissant une isolation entre les flux. Par la suite, afin dâanalyser lâimpact de ce nouveau RDC sur les performances du systĂšme avionique, nous procĂ©dons Ă la modĂ©lisation de lâarchitecture CAN-AFDX, et particuliĂšrement le RDC et ses nouvelles fonctions. Ensuite, nous introduisons une mĂ©thode dâanalyse temporelle pour calculer des bornes maximales sur les dĂ©lais de bout en bout et vĂ©rifier le respect des contraintes temps-rĂ©el. Plusieurs configurations du RDC peuvent rĂ©pondre aux exigences du systĂšme avionique tout en offrant des Ă©conomies de ressources. Nous procĂ©dons donc au paramĂ©trage du RDC afin de minimiser la consommation de bande passante sur lâAFDX tout en respectant les contraintes temporelles. Ce problĂšme dâoptimisation est considĂ©rĂ© comme NP-complet, et lâintroduction des heuristiques adĂ©quates sâest avĂ©rĂ©e nĂ©cessaire afin de trouver la meilleure configuration possible du RDC. Enfin, les performances de ce nouveau RDC sont validĂ©es Ă travers une architecture CAN-AFDX rĂ©aliste, avec plusieurs bus CAN et des centaines de flux Ă©changĂ©s. DiffĂ©rents niveaux dâutilisation des bus CAN ont Ă©tĂ© considĂ©rĂ©s et les rĂ©sultats obtenus ont montrĂ© lâefficacitĂ© de notre RDC Ă amĂ©liorer la gestion des ressources du systĂšme avionique tout en respectant les contraintes temporelles de communication. En particulier, notre RDC offre une rĂ©duction de la bande passante AFDX allant jusquâĂ 40% en comparaison avec le RDC actuellement utilisĂ©. ABSTRACT : The aim of my thesis is to provide a resources-efficient gateway to connect Input/Output (I/O) CAN buses to a backbone network based on AFDX technology, in modern avionics communication architectures. Currently, the Remote Data Concentrator (RDC) is the main standard for gateways in avionics; and the existing implementations do not integrate any resource management mechanism. To handle these limitations, we design an enhanced CAN-AFDX RDC integrating new functions: (i) Frame Packing (FP) allowing to reduce communication overheads with reference to the currently used "1 to 1" frame conversion strategy; (ii) Hierarchical Traffic Shaping (HTS) to reduce contention on the CAN bus. Furthermore, our proposed RDC allows the connection of multiple I/O CAN buses to AFDX while guaranteeing isolation between different criticality levels, using a software partitioning mechanism. To analyze the performance guarantees offered by our proposed RDC, we considered two metrics: the end-to-end latency and the induced AFDX bandwidth consumption. Furthermore, an optimization process was proposed to achieve an optimal configuration of our proposed RDC, i.e., minimizing the bandwidth utilization while meeting the real-time constraints of communication. Finally, the capacity of our proposed RDC to meet the emerging avionics requirements has been validated through a realistic avionics case study
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Operational support systems for satellite communications
The role of satellite communications is changing from providing bandwidth linking network operators interconnections towards providing IP enabled communications to end users. This migration from few high-value routes towards many low-value routes means that integration and automation of processes with terrestrial networks becomes critical in driving down unit costs. Integration and automation is necessary on all planes: user, control and management. In satellite communications, management aspects, underpinned by Operational Support Systems (OSS) have received the least research attention, making this a valuable topic for study. In most areas, OSS for satellite systems are similar to other domains. However there are some notable areas of difference which have been the focus of this research. The eTOM business framework, developed by the TMF, has been used to highlight aspects of OSS unique to satellite. Since satellite capacity represents the highest operational cost of a satellite route, effective management while minimising the overhead traffic is critical. The transmission of IP packets is assumed and the real-time measurement of QoS parameters such as packet delay and loss emerged as the most important differences. A number of approaches to QoS measurement are feasible, however the use of trace packets is most promising especially for high network loads. An experiment compares the results from simulations, mathematical models and from a test network, using Poisson and self-similar traffic flows. The relationship between measurement accuracy and trace packet intensity is explored and the measurement response time to steps in traffic load is estimated. It is discovered that measurement accuracy improves as the queue load increases, in contrast to alternative approaches such as sampling of user packets. The response time to steps depends upon the degree of self-similarity and is generally longer than the times recommended by standards. A pragmatic approach to management of different modes is proposed where the measurement method is changed depending on the load
Analysis and optimiozation of heterogeneous avionics networks
The aim of my thesis is to provide a resources-efficient gateway to connect Input/Output (I/O) CAN buses to a backbone network based on AFDX technology, in modern avionics communication architectures. Currently, the Remote Data Concentrator (RDC) is the main standard for gateways in avionics; and the existing implementations do not integrate any resource management mechanism. To handle these limitations, we design an enhanced CAN-AFDX RDC integrating new functions: (i) Frame Packing (FP) allowing to reduce communication overheads with reference to the currently used "1 to 1" frame conversion strategy; (ii) Hierarchical Traffic Shaping (HTS) to reduce contention on the CAN bus. Furthermore, our proposed RDC allows the connection of multiple I/O CAN buses to AFDX while guaranteeing isolation between different criticality levels, using a software partitioning mechanism. To analyze the performance guarantees offered by our proposed RDC, we considered two metrics: the end-to-end latency and the induced AFDX bandwidth consumption. Furthermore, an optimization process was proposed to achieve an optimal configuration of our proposed RDC, i.e., minimizing the bandwidth utilization while meeting the real-time constraints of communication. Finally, the capacity of our proposed RDC to meet the emerging avionics requirements has been validated through a realistic avionics case study
Improved learning automata applied to routing in multi-service networks
Multi-service communications networks are generally designed, provisioned and configured, based on source-destination user demands expected to occur over a recurring time period. However due to network users' actions being non-deterministic, actual user demands will vary from those expected, potentially causing some network resources to be under- provisioned, with others possibly over-provisioned. As actual user demands vary over the recurring time period from those expected, so the status of the various shared network resources may also vary. This high degree of uncertainty necessitates using adaptive resource allocation mechanisms to share the finite network resources more efficiently so that more of actual user demands may be accommodated onto the network. The overhead for these adaptive resource allocation mechanisms must be low in order to scale for use in large networks carrying many source-destination user demands. This thesis examines the use of stochastic learning automata for the adaptive routing problem (these being adaptive, distributed and simple in implementation and operation) and seeks to improve their weakness of slow convergence whilst maintaining their strength of subsequent near optimal performance. Firstly, current reinforcement algorithms (the part causing the automaton to learn) are examined for applicability, and contrary to the literature the discretised schemes are found in general to be unsuitable. Two algorithms are chosen (one with fast convergence, the other with good subsequent performance) and are improved through automatically adapting the learning rates and automatically switching between the two algorithms. Both novel methods use local entropy of action probabilities for determining convergence state. However when the convergence speed and blocking probability is compared to a bandwidth-based dynamic link-state shortest-path algorithm, the latter is found to be superior. A novel re-application of learning automata to the routing problem is therefore proposed: using link utilisation levels instead of call acceptance or packet delay. Learning automata now return a lower blocking probability than the dynamic shortest-path based scheme under realistic loading levels, but still suffer from a significant number of convergence iterations. Therefore the final improvement is to combine both learning automata and shortest-path concepts to form a hybrid algorithm. The resulting blocking probability of this novel routing algorithm is superior to either algorithm, even when using trend user demands
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