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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

System Framework for a Multi-Band, Multi-Mode Software Defined Radio

Thomas, Willie L., II, Berhanu, Samuel, Richardson, Nathan 10 1900 (has links)
ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / This paper describes a system framework for a multi-band, multi-mode software defined radio (MBMM SDR) being developed for next-generation telemetry applications. The system framework consists of the multi-band front-end (MBFE), the multi-mode digital radio (MMDR), and the configuration and control (C2) sub-systems. The MBFE consists of an L/S/C-band transceiver architecture that provides wideband operation, band selection, and channel tuning. The MMDR consists of the software and firmware components for high-speed digital signal processing for the telemetry waveforms. Finally, the C2 consists of the software and hardware components for system configuration, control and status. The MBFE is implemented as a standalone hardware sub-system, while the MMDR and C2 are integrated into a single hardware subsystem that utilizes state-of-the-art system-on-chip (SoC) technology. Design methodologies, hardware architectures, and system tradeoffs are highlighted to meet next-generation telemetry requirements for improved spectrum efficiency and utilizations. Approved for public release; distribution is unlimited (412TW-PA-14281).
132

An Open Systems Architecture for Telemetry Receivers

Parker, Peter, Nelson, John, Pippitt, Mark 10 1900 (has links)
An open systems architecture (OSA) is one in which all of the interfaces are fully defined, available to the public, and maintained according to a group consensus. One approach to achieve this is to use modular hardware and software and to buy commercial, off-the-shelf and commodity hardware. Benefits of an OSA include providing easy access to the latest technological advances in both hardware and software, enabling net-centric operations, and allowing a flexible design that can easily change as the needs of customers may change. This paper will provide details of an OSA system designed for a telemetry receiver and list the benefits of OSA for the telemetry community.
133

The Process of Implementing a RF Front-End Transceiver for NASA's Space Network

Wilder, Ali, Pannu, Randeep, Haj-Omar, Amr 10 1900 (has links)
Software defined radio (SDR) introduces endless possibilities for future communication technologies. Instead of being limited to a static segment of the radio spectrum, SDR allows RF front-ends to be more flexible by using digital signal processing (DSP) and cognitive techniques to integrate adaptive hardware with dynamic software. We present the design and implementation of an innovative RF front-end transceiver architecture for application into a SDR test-bed platform. System-level requirements were extracted from the Space Network User Guide (SNUG). Initial system characterization demonstrated image leakage due to poor filtering and mixer isolation issues. Hence, the RF front-end design was re-implemented using the Weaver architecture for improved image rejection performance.
134

Netlang : un langage de haut niveau pour les routeurs programmables dans le contexte des réseaux SDN

Boughzala, Bochra 07 1900 (has links) (PDF)
Développer des applications réseaux pour des routeurs programmables basés sur les Network Processors (NPs) implique l'utilisation de langages de bas-niveau et d'outils propriétaires fortement dépendants des architectures matérielles sous-jacentes. Le code source, généralement écrit en langage assembleur, n'est pas facile à écrire et cause des problèmes de maintenance. Les applications résultantes sont également difficiles à déboguer. Dans ce mémoire nous proposons NETLANG, un nouveau langage de programmation de haut-niveau dédié aux NPs. De plus d'être un langage simple et élégant, de réduire les coûts de développement et de la maintenance, et d'améliorer la réutilisation du code, NETLANG a pour objectif essentiel de décrire le comportement des paquets dans un NP. NETLANG est un langage qui permet de développer des applications de traitement de paquets. Il établit deux niveaux. Le premier niveau du langage offre une abstraction et une description du routeur à travers un pipeline de tables OpenFlow et des règles de forwarding ayant l'aptitude d'être modifiées dynamiquement et donc de permettre de changer le comportement du routeur à la volée. La sémantique du langage est inspirée du protocole OpenFlow qui a permis d'exprimer les principales tâches de traitement de paquets telles que le parsing, le lookup et la modification. Le langage est bâti en respectant le modèle des Software Defined Networks (SDNs) qui définit un nouveau plan de séparation entre le control plane et le data plane. Le deuxième niveau de NETLANG est traduit en matériel et permet l'adaptabilité du langage à plusieurs plateformes. Des adaptateurs spécifiques à des plateformes différentes sont intégrés au compilateur de NETLANG et permettent de rendre le langage portable. En effet, nous avons utilisé deux environnements pour l'implémentation de NETLANG ; le NP4 d'EZchip caractérisé par sa structure de TOPs (Task Optimized Processors) en pipeline et le NFP-3240 de Netronome connu pour son parallélisme et l'exploitation du multithreading. La validation de NETLANG s'est basée sur un ensemble d'applications réseau ayant des complexités et des domaines différents. A travers ce mémoire nous avons démontré qu'on est capable d'avoir aujourd'hui un langage pour les routeurs programmables. La sémantique d'OpenFlow, sur laquelle nous avons basé notre langage NETLANG, est suffisante et même pertinente en termes de description de comportement des paquets dans un NP. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : langages à domaine spécifique, réseaux programmables, processeurs de réseau.
135

On Real Time Digital Phase Locked Loop Implementation with Application to Timing Recovery

Kippenberger, Roger Miles January 2006 (has links)
In digital communication systems symbol timing recovery is of fundamental importance. The accuracy in estimation of symbol timing has a direct effect on received data error rates. The primary objective of this thesis is to implement a practical Digital Phase Locked Loop capable of accurate synchronisation of symbols suffering channel corruption typical of modern mobile communications. This thesis describes an all-software implementation of a Digital Phase Locked in a real-time system. A timing error detection (TED) algorithms optimally implemented into a Digital Signal Processor. A real-time transmitter and receiver system is implemented in order to measure performance when the received signal is corrupted by both Additive White Gaussian Noise and Flat Fading. The Timing Error Detection algorithm implemented is a discrete time maximum likelihood one known as FFML1, developed at Canterbury University. FFML1 along with other components of the Digital Phase Locked loop are implemented entirely in software, using Motorola 56321 assembly language.
136

Reducing the Cost of Operating a Datacenter Network

Curtis, Andrew January 2012 (has links)
Datacenters are a significant capital expense for many enterprises. Yet, they are difficult to manage and are hard to design and maintain. The initial design of a datacenter network tends to follow vendor guidelines, but subsequent upgrades and expansions to it are mostly ad hoc, with equipment being upgraded piecemeal after its amortization period runs out and equipment acquisition is tied to budget cycles rather than changes in workload. These networks are also brittle and inflexible. They tend to be manually managed, and cannot perform dynamic traffic engineering. The high-level goal of this dissertation is to reduce the total cost of owning a datacenter by improving its network. To achieve this, we make the following contributions. First, we develop an automated, theoretically well-founded approach to planning cost-effective datacenter upgrades and expansions. Second, we propose a scalable traffic management framework for datacenter networks. Together, we show that these contributions can significantly reduce the cost of operating a datacenter network. To design cost-effective network topologies, especially as the network expands over time, updated equipment must coexist with legacy equipment, which makes the network heterogeneous. However, heterogeneous high-performance network designs are not well understood. Our first step, therefore, is to develop the theory of heterogeneous Clos topologies. Using our theory, we propose an optimization framework, called LEGUP, which designs a heterogeneous Clos network to implement in a new or legacy datacenter. Although effective, LEGUP imposes a certain amount of structure on the network. To deal with situations when this is infeasible, our second contribution is a framework, called REWIRE, which using optimization to design unstructured DCN topologies. Our results indicate that these unstructured topologies have up to 100-500\% more bisection bandwidth than a fat-tree for the same dollar cost. Our third contribution is two frameworks for datacenter network traffic engineering. Because of the multiplicity of end-to-end paths in DCN fabrics, such as Clos networks and the topologies designed by REWIRE, careful traffic engineering is needed to maximize throughput. This requires timely detection of elephant flows---flows that carry large amount of data---and management of those flows. Previously proposed approaches incur high monitoring overheads, consume significant switch resources, or have long detection times. We make two proposals for elephant flow detection. First, in the Mahout framework, we suggest that such flows be detected by observing the end hosts' socket buffers, which provide efficient visibility of flow behavior. Second, in the DevoFlow framework, we add efficient stats-collection mechanisms to network switches. Using simulations and experiments, we show that these frameworks reduce traffic engineering overheads by at least an order of magnitude while still providing near-optimal performance.
137

Digital Radio Encoding and Power Amplifier Design for Multimode and Multiband Wireless Communications

Xia, Jingjing 22 April 2013 (has links)
The evolution of wireless technology has necessitated the support of multiple communication standards by mobile devices. At present, multiple chipsets/radios operating at predefined sets of modulation schemes, frequency bands, bandwidths and output power levels are used to achieve this objective. This leads to higher component counts, increased cost and limits the capacity to cope with future communication standards. In order to tackle different wireless standards using a single chipset, digital circuits have been increasingly deployed in radios and demonstrated re-configurability in different modulation schemes (multimode) and frequency bands (multiband). Despite efforts and progress made in digitizing the entire radio, the power amplifier (PA) is still designed using an conventional approach and has become the bottleneck in digital transmitters, in terms of low average power efficiency, poor compatibility with modern CMOS technology and limited re-configurability. This research addresses these issues from two aspects. The first half of the thesis investigates signal encoding issues between the modulator and PA. We propose, analyze and evaluate a new hybrid amplitude/time signal encoding scheme that significantly improves the coding efficiency and dynamic range of a digitally modulated power amplifier (DMPA) without significantly increasing design complexity. The proposed hybrid amplitude/time encoding scheme combines both the amplitude domain and the time domain to optimally encode information. Experimental results show that hybrid amplitude/time encoding results in a 35% increase in the average coding efficiency with respect to conventional time encoding, and is only 6.7% lower than peak efficiency when applied to a Wireless Local Area Network (WLAN) signal with a peak to average power ratio equal to 9.9 dB. A new DMPA architecture, based on the proposed hybrid encoding, is also proposed. The second half of this thesis presents the design, analysis and implementation of a CMOS PA that is amenable to the proposed hybrid encoding scheme. A multi-way current mode class-D PA architecture has been proposed and realized in 130 nm CMOS technology. The designed PA has satisfied the objectives of wide bandwidth (1.5 GHz - 2.7 GHz at 1 dB output power), and high efficiency (PAE 63%) in addition to demonstrating linear responses using the proposed digital encoding. A complete digital transmitter combining the encoder and the multi-way PA was also investigated. The overall efficiency is 27% modulating 7.3 dB peak to average power ratio QAM signals.
138

Design And Implementation Of Fir Digital Filters With Variable Frequency Characteristics

Piskin, Hatice 01 December 2005 (has links) (PDF)
Variable digital filters (VDF) find many application areas in communication, audio, speech and image processing. This thesis analyzes design and implementation of FIR digital filters with variable frequency characteristics and introduces two design methods. The design and implementation of the proposed methods are realized on Matlab software program. Various filter design examples and comparisons are also outlilned. One of the major application areas of VDFs is software defined radio (SDR). The interpolation problem on sample rate converter (SRC) unit of the SDR is solved by using these filters. Realizations of VDFs on SRC are outlined and described. Simulations on Simulink and a specific hardware are examined.
139

SDEFIX : gerenciando fluxos elefantes em pontos de troca de tráfego baseados em redes defenidas por software / SDEFIX : manage elephant flows in SDN-Based IXP networks

Knob, Luis Augusto Dias January 2016 (has links)
Os Pontos de Troca de Tráfego participam de maneira substancial e crítica no ecossistema da Internet, possibilitando conexões entre múltiplos Sistemas Autônomos (ASes, do inglês Autonomous Systems). O gerenciamento das redes de PTT possui como objetivos primários, o gerenciamento dos chamados fluxos elefante (do inglês, elephant flows). Fluxos elefante tendem a existir em número reduzido, porém correspondem à maioria do tráfego em uma infraestrutura de rede. O gerenciamento dos fluxos elefante envolve uma adequada identificação e quando necessário, um redirecionamento destes fluxos para caminhos mais apropriados, de forma a minimizar os possíveis impactos sobre os outros fluxos ativos na rede. Além disso, o gerenciamento de fluxos elefante tornou-se um importante objeto de discussão em PTTs baseados em redes SDN, principalmente porque estas redes dispõem de controladores que possuem uma visão consistente da rede subjacente, o que permite uma gerência destes fluxos de forma refinada. Nesta dissertação, será proposto, desenvolvido e avaliado um sistema de identificação dos fluxos elefante e seus respectivos caminhos de rede, em conjunto com um sistema de recomendação, que possui o objetivo de sugerir configurações alternativas para os fluxos elefante identificados anteriormente nas redes de PTTs baseadas em SDN. Neste sistema, o operador do PTT pode definir templates que em última instância definem como os caminhos dos fluxos elefante serão modificados para atender objetivos específicos. Por fim, será demonstrado que o sistema proposto pode auxiliar o operador do PTT a identificar, gerenciar e mitigar o impacto dos fluxos elefante da rede do PTT. / Internet Exchange Points (IXPs) play a key role in the current Internet architecture enabling cost-effective connections among multiple autonomous systems (ASes). Management of IXP networks is primarily concerned with the management of the so-called elephant flows. Such flows represent a small portion of the total flows of a IXP network but usually have high impact on the overall traffic. Managing elephant flows involves adequate identification and eventually rerouting of such flows to more appropriate locations to minimize the possible negative impact on the other (mice) flows active in the network. Elephant flow management becomes more important in SDN-based IXPs that require controllers to have a consistent view of the underlying network to allow fine-grained adjustment. In this master thesis, we propose, develop, and evaluate an identification system to identify elephant flows and their respectively paths, as well as a recommendation system to suggest alternative configurations to previously identified elephant flows in an SDN-based IXP network. In this solution, the IXP operator can define templates that ultimately define how elephant flows can be reconfigured to achieve a specific objective. We demonstrate that our system can help IXP operators to identify, handle and mitigate the impact of elephant flows in the IXP network.
140

Employing concepts of the SDN paradigm to support last-mile military tactical edge networks / Empregando conceitos de redes definidas por software para apoio à redes táticas militares de última milha

Zacarias, Iulisloi January 2018 (has links)
Em um futuro próximo, “dispositivos inteligentes” serão massivamente empregados em campos de batalha. Essa já é uma realidade, porém, o número de dispositivos utilizados em campos de batalha tende a aumentar em ordens de magnitude. As redes de comunicação de dados serão essenciais para transmitir os dados que esses dispositivos coletam e transformá-los em informações valiosas utilizadas como suporte à atuação humana. O suporte à tomada de decisão, ou mesmo níveis de autonomia, permitindo que estes dispositivos coordenem outros dispositivos, exigem comunicação contínua. Desafios relacionados à comunicação surgirão devido à dinamicidade do ambiente. A configuração da rede deve refletir decisões superiores automaticamente. A grande escala das redes conectando os altos escalões, tropas, veículos e sensores, aliada à falta de padronização dos dispositivos, tornará a integração destes desafiadora. Em um ambiente tão heterogêneo, muitos protocolos e tecnologias coexistirão. As redes de campo de batalha são um elemento de suma importância nas operações militares modernas e conceito de guerra centrada em rede é uma tendência sem volta e influencia desde os altos escalões até o controle de tropas Embora estudos tenham sido realizados nessa área, a maioria deles aborda redes estratégicas de alto nível e portanto não levam em conta as “redes táticas de última milha” (TEN), que compreendem dispositivos de comunicação com recursos limitados, como sensores ou ainda pequenos veículos aéreos não tripulados. Em uma tentativa de preencher esta lacuna, esse trabalho propõe uma arquitetura que combina conceitos dos paradigmas de redes definidas por software (SDN) juntamente com redes tolerantes à atraso/disrupçoes (DTN), para aplicação em redes táticas de última milha. O uso de SDN em cenários com nodos móveis é avaliado considerando uma aplicação de vigilância que utiliza streaming de vídeo e medidas de Qualidade de Experiência (QoE) de usuário são coletadas. Com base nos resultados obtidos, uma aplicação em conjunto dos conceitos de SDN e DTN é proposta, além disso abordamos a escolha do nodo que atuará como controlador SDN na rede. Os experimentos foram executados utilizando um emulador de redes. Apesar de pesquisas adicionais serem necessárias – considerado requisitos de segurança, por exemplo – os resultados foram promissores e demonstram a aplicabilidade destes conceitos no cenários das TENs. / The future battlefield tends to be populated by a plethora of “intelligent things”. In some ways, this is already a reality, but in future battlefields, the number of deployed things should be orders of magnitude higher. Networked communication is essential to take real advantage of the deployed devices on the battlefield, and to transform the data collected by them into information valuable for the human warfighters. Support for human decision making and even a level of autonomy, allowing devices to coordinate and interact with each other to execute their activities in a collaborative way require continuous communication. Challenges regarding communication will arise from the high dynamics of the environment. The network adaption and management should occur autonomously, and it should reflect upper-level decisions. The large scale of the network connecting high-level echelons, troops on the field, and sensors of many types, beside the lack of communication standards turn the integration of the devices more challenging. In such a heterogeneous environment, many protocols and communication technologies coexist. This way, battlefield networks is an element of paramount importance in modern military operations Additionally, a change of paradigm regarding levels of autonomy and cooperation between humans and machines is in course and the concept of network-centric warfare is a no way back trend. Although new studies have been carried out in this area, most of these concern higher-level strategic networks, with abundant resources. Thus, these studies fail to take into account the “last-mile Tactical Edge Network (TEN) level,” which comprises resource constrained communication devices carried by troopers, sensor nodes deployed on the field or small unmanned aerial vehicles. In an attempt to fill this gap, this work proposes an architecture combining concepts from software-defined networking (SDN) paradigm and the delay-tolerant approach to support applications in the last-mile TEN. First, the use of SDN in dynamic scenarios regarding node positioning is evaluated through a surveillance application using video streaming and Quality of Experience (QoE) measures are captured on the video player. We also explore the election of nodes to act as SDN Controllers in the TEN environment. The experiments use emulator for SDN with support to wireless networks. Further investigation is required, for example, considering security requirements, however the results are promising and demonstrate the applicability of this architecture in the TEN network scenario.

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