• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 495
  • 208
  • 135
  • 93
  • 75
  • 74
  • 47
  • 41
  • 28
  • 18
  • 16
  • 16
  • 15
  • 14
  • 10
  • Tagged with
  • 1371
  • 490
  • 354
  • 353
  • 252
  • 191
  • 167
  • 150
  • 149
  • 116
  • 116
  • 112
  • 101
  • 98
  • 97
  • 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.
501

INTERNET TECHNOLOGY FOR FUTURE SPACE MISSIONS

Rash, James, Hogie, Keith, Casasanta, Ralph 10 1900 (has links)
International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / Ongoing work at National Aeronautics and Space Administration Goddard Space Flight Center (NASA/GSFC), seeks to apply standard Internet applications and protocols to meet the technology challenge of future satellite missions. Internet protocols and technologies are under study as a future means to provide seamless dynamic communication among heterogeneous instruments, spacecraft, ground stations, constellations of spacecraft, and science investigators. The primary objective is to design and demonstrate in the laboratory the automated end-to-end transport of files in a simulated dynamic space environment using off-the-shelf, low-cost, commodity-level standard applications and protocols. The demonstrated functions and capabilities will become increasingly significant in the years to come as both earth and space science missions fly more sensors and the present labor-intensive, mission-specific techniques for processing and routing data become prohibitively. This paper describes how an IP-based communication architecture can support all existing operations concepts and how it will enable some new and complex communication and science concepts. The authors identify specific end-to-end data flows from the instruments to the control centers and scientists, and then describe how each data flow can be supported using standard Internet protocols and applications. The scenarios include normal data downlink and command uplink as well as recovery scenarios for both onboard and ground failures. The scenarios are based on an Earth orbiting spacecraft with downlink data rates from 300 Kbps to 4 Mbps. Included examples are based on designs currently being investigated for potential use by the Global Precipitation Measurement (GPM) mission.
502

下一代網路資訊服務與系統供應商之成功經營模式研究

陳建宏, Chen, Chien Hung Unknown Date (has links)
下一代網路(Next Generation Network,NGN)是因應未來語音、數據、影像等Triple Play之資訊服務對頻寬與網路能力要求日益增加下所提出的一種新網路形態概念。同時,NGN以IP 多媒體子系統(IP Multimedia Subsystem,IMS)為其核心可以降低系統供應商的營運佈建成本。NGN強調的固網行動融合(Fixed Mobile Convergence,FMC)與全IP網路(All IP Network)化以及強化服務品質(Quality of Service,QoS)精神,都使資訊服務與系統供應業者需要思考出一套新的經營模式(Business Model),使其能在NGN上獲利。本研究之主要目的為以NGN的架構與特性為出發,剖析此一網路的數位匯流趨勢與其成功經營模式研究。 本研究採個案研究法(Case Study Method),透過次級資料的蒐集以及與本研究有關之文獻探討的方式,找出未來NGN的經營模式形貌,並透過訪談相關業者來佐證本研究所提出經營模式之合理性。 由於資訊服務產業範圍廣泛,故本研究選定VoIP及IPTV為主要研究對象,期盼能找出一套適合在NGN上獲利的模式。另外針對企業用戶,NGN也能協助企業增加競爭力,在商業情報的取得、溝通成本的降低、資訊管理系統等都能有所貢獻。 / Next Generation Network,NGN, is a new form of internet concept of Triple play informational service integrated voice mail, data and video as the requirements of more wider bandwidth and high internet power increase. Meanwhile, The core of IP Multimedia Subsystem,IMS, NGN targets can lower operational cost to system suppliers. NGN emphasizes the spirit to combine Fixed Mobile Convergence,FMC, all IP network and Enhanced Quality of Service. The spirit makes the suppliers of informational service and system to think a new business model to make profits in NGN. The research of this thesis bases on NGN’s structure and features to analyze the trend of digital convergence in internet and succeeded business model. This essay adopts Case Study Research. By collecting sub data and relative document research figures out future image of NGN business model. Besides, it is interviewed with pertaining businesses to testify the reality of business model offered in this thesis. Owning to the scope of informational service business is unlimited, the thesis is chosen VoIP and IPTV as main targets to find out an appropriate and a profitable business model in this informational field. Furthermore, to business user, NGN can support industries to increase competitive ability and gain useful business information, decrease communicative cost and upgrade the performance of MIS
503

Propriétés fonctionnelles du récepteur à l'inositol 1,4,5 trisphophate

Chaloux, Benoit January 2010 (has links)
Le récepteur à l'inositol 1,4,5-trisphosphate (IP[indice inférieur 3]R) est un canal calcique jouant un rôle prépondérant dans le contrôle du calcium à l'intérieur des cellules non-excitables. Il existe trois sous-types d'IP[indice inférieur 3]R qui sont encodés par des gènes différents. L'objectif de mon travail était d'évaluer la régulation des IP[indice inférieur 3]Rs par différents mécanismes extrinsèque et intrinsèque. Avec une approche in vitro , nous avons montré que l'IP[indice inférieur 3]R-3 est un substrat de la protéine kinase dépendante de l'AMPc (PKA). Avec une approche de"backphosphorylation", nous avons également montré que la PKA phosphoryle de manière endogène l'IP[indice inférieur 3]R-3 dans les cellules RINm5F intactes. Avec des études de liaison, nous avons montré que la PKA augmente l'affinité de l'IP[indice inférieur 3]R-3. La mesure des relâches de Ca[indice supérieur 2+] induites par l'IP[indice inférieur 3] sur des cellules perméabilisées a aussi révélé que la PKA augmente l'affinité apparente de l'IP[indice inférieur 3]R-3. Enfin, dans des cellules RINm5F intactes, la PKA a potentié la relâche de Ca[indice supérieur 2+] induite par le carbachol et le facteur de croissance épidermique, deux agonistes qui activent la phospholipases C par des mécanismes différents. Ces résultats ont révélé une étape de convergence où la voie de signalisation de l'AMPc et la voie de signalisation du Ca[indice supérieur 2+] interagissent pour moduler différentes fonctions au sein d'une seule et même cellule face à des stimuli externes. Les différents domaines des IP[indice inférieur 3]Rs ont des rôles particuliers dans le contrôle fin de l'homéostasie calcique intracellulaire. Nous avons montré qu'un mutant tronqué de l'IP[indice inférieur 3]R-2 (CTR2), qui ne comporte que les 2 derniers domaines transmembranaires et la queue C-terminale, se comporte comme un canal calcique constitutivement actif. Les cellules exprimant le CTR2 ont moins de Ca[indice supérieur 2+] dans leurs réserves intracellulaire [sic], relâchent moins de Ca[indice supérieur 2+] en réponse aux agonistes et montrent une entrée capacitative de Ca[indice supérieur 2+] en conditions basales. Ces résultats suggèrent qu'en absence d'une régulation intrinsèque par sa portion N-terminale, l'IP[indice inférieur 3]R-2 se comporte comme un canal calcique ouvert. L'ensemble de mon travail met en évidence un mécanisme extrinsèque (PKA) et un mécanisme intrinsèque (N-terminal) de régulation de l'activité des IP[indice inférieur 3]Rs.
504

Délivrance de servcies médias ubiquitaires adaptés selon le contexte au sein de réseaux de nouvelles générations / Context-awareness for ubiquitous media service delivery in next generation networks

Arnaud, Julien 17 December 2012 (has links)
Les récentes avancées technologiques permettent désormais la fabrication de terminaux mobiles de plus en plus compacts et dotés de plusieurs interfaces réseaux. Le nouveau modèle de consommation de médias se résume par le concept "Anytime, Anywhere, Any Device" et impose donc de nouvelles exigences en termes de déploiement de services ubiquitaires. Cependant la conception et le developpement de réseaux ubiquitaires et convergents de nouvelles générations soulèvent un certain nombre de défis techniques. Les standards actuels ainsi que les solutions commerciales pourraient être affectés par le manque de considération du contexte utilisateur. Le ressenti de l'utilisateur concernant certains services multimédia tels que la VoIP et l'IPTV dépend fortement des capacités du terminal et des conditions du réseau d'accès. Cela incite les réseaux de nouvelles générations à fournir des services ubiquitaires adaptés à l'environnement de l'utilisateur optimisant par la même occasion ses resources. L'IP Multimedia Subsystem (IMS) est une architecture de nouvelle génération qui centralise l'accès aux services et permet la convergence des réseaux fixe/mobile. Néanmoins, l'évolution de l'IMS est nécessaire sur les points suivants :- l'introduction de la sensibilité au contexte utilisateur et de la PQoS (Perceived QoS) : L'architecture IMS ne prend pas en compte l'environnement de l'utilisateur, ses préférences et ne dispose pas d'un méchanisme de gestion de PQOS. Pour s'assurer de la qualité fournit à l'utilisateur final, des informations sur l'environnement de l'utilisateur ainsi que ses préférences doivent transiter en cœur de réseau afin d'y être analysés. Ce traitement aboutit au lancement du service qui sera adapté et optimisé aux conditions observées. De plus pour le service d'IPTV, les caractéristiques spatio-temporelles de la vidéo influent de manière importante sur la PQoS observée côté utilisateur. L'adaptation des services multimédias en fonction de l'évolution du contexte utilisateur et de la nature de la vidéo diffusée assure une qualité d'expérience à l'utilisateur et optimise par la même occasion l'utilisation des ressources en cœur de réseau.- une solution de mobilité efficace pour les services conversationnels tels que la VoIP : Les dernières publications 3GPP fournissent deux solutions de mobilité: le LTE propose MIP comme solution de mobilité alors que l'IMS définit une mobilité basée sur le protocole applicatif SIP. Ces standards définissent le système de signalisation mais ne s'avancent pas sur la gestion du flux média lors du changement d'interface réseau. La deuxième section introduit une étude comparative détaillée des solutions de mobilité dans les NGNs.Notre première contribution est la spécification de l'architecture globale de notre plateforme IMS sensible au contexte utilisateur réalisée au sein du projet Européen ADAMANTIUM. Nous détaillons tout d'abord le serveur MCMS intelligent placé dans la couche application de l'IMS. Cet élément récolte les informations de qualité de services à différents équipements réseaux et prend la décision d'une action sur l'un de ces équipements. Ensuite nous définissons un profil utilisateur permettant de décrire son environnement et de le diffuser en coeur de réseau. Une étude sur la prédiction de satisfaction utilisateur en fonction des paramètres spatio-temporels de la vidéo a été réalisée afin de connaître le débit idéal pour une PQoS désirée.Notre deuxième contribution est l'introduction d'une solution de mobilité adaptée aux services conversationnels (VoIP) tenant compte du contexte utilisateur. Notre solution s'intègre à l'architecture IMS existante de façon transparente et permet de réduire le temps de latence du handover. Notre solution duplique les paquets de VoIP sur les deux interfaces actives pendant le temps de la transition. Parallèlement, un nouvel algorithme de gestion de mémoire tampon améliore la qualité d'expérience pour le service de VoIP. / The latest advances in technology have already defied Moore’s law. Thanks to research and industry, hand-held devices are composed of high processing embedded systems enabling the consumption of high quality services. Furthermore, recent trends in communication drive users to consume media Anytime, Anywhere on Any Device via multiple wired and wireless network interfaces. This creates new demands for ubiquitous and high quality service provision management. However, defining and developing the next generation of ubiquitous and converged networks raise a number of challenges. Currently, telecommunication standards do not consider context-awareness aspects for network management and service provisioning. The experience felt by the end-user consuming for instance Voice over IP (VoIP) or Internet Protocol TeleVision (IPTV) services varies depending mainly on user preferences, device context and network resources. It is commonly held that Next Generation Network (NGN) should deliver personalized and effective ubiquitous services to the end user’s Mobile Node (MN) while optimizing the network resources at the network operator side. IP Multimedia Subsystem (IMS) is a standardized NGN framework that unifies service access and allows fixed/mobile network convergence. Nevertheless IMS technology still suffers from a number of confining factors that are addressed in this thesis; amongst them are two main issues :The lack of context-awareness and Perceived-QoS (PQoS):-The existing IMS infrastructure does not take into account the environment of the user ,his preferences , and does not provide any PQoS aware management mechanism within its service provisioning control system. In order to ensure that the service satisfies the consumer, this information need to be sent to the core network for analysis. In order to maximize the end-user satisfaction while optimizing network resources, the combination of a user-centric network management and adaptive services according to the user’s environment and network conditions are considered. Moreover, video content dynamics are also considered as they significantly impact on the deduced perceptual quality of IPTV services. -The lack of efficient mobility mechanism for conversational services like VoIP :The latest releases of Third Generation Partnership Project (3GPP) provide two types of mobility solutions. Long-Term Evolution (LTE) uses Mobile IP (MIP) and IMS uses Session Initiation Protocol (SIP) mobility. These standards are focusing on signaling but none of them define how the media should be scheduled in multi-homed devices. The second section introduces a detailed study of existing mobility solutions in NGNs. Our first contribution is the specification of the global context-aware IMS architecture proposed within the European project ADAptative Management of mediA distributioN based on saTisfaction orIented User Modeling (ADAMANTIUM). We introduce the innovative Multimedia Content Management System (MCMS) located in the application layer of IMS. This server combines the collected monitoring information from different network equipments with the data of the user profile and takes adaptation actions if necessary. Then, we introduce the User Profile (UP) management within the User Equipment (UE) describing the end-user’s context and facilitating the diffusion of the end-user environment towards the IMS core network. In order to optimize the network usage, a PQoS prediction mechanism gives the optimal video bit-rate according to the video content dynamics. Our second contribution in this thesis is an efficient mobility solution for VoIP service within IMS using and taking advantage of user context. Our solution uses packet duplication on both active interfaces during handover process. In order to leverage this mechanism, a new jitter buffer algorithm is proposed at MN side to improve the user’s quality of experience. Furthermore, our mobility solution integrates easily to the existing IMS platform.
505

[en] EFFICIENT FEATURES AND INTERPOLATION DOMAINS IN DISTRIBUTED SPEECH RECOGNITION / [pt] ATRIBUTOS E DOMÍNIOS DE INTERPOLAÇÃO EFICIENTES EM RECONHECIMENTO DE VOZ DISTRIBUÍDO

VLADIMIR FABREGAS SURIGUE DE ALENCAR 01 April 2005 (has links)
[pt] Com o crescimento gigantesco da Internet e dos sistemas de comunicações móveis celulares, as aplicações de processamento de voz nessas redes têm despertado grande interesse . Um problema particularmente importante nessa área consiste no reconhecimento de voz em um sistema servidor, baseado nos parâmetros acústicos calculados e quantizados no terminal do usuário (Reconhecimento de Voz Distribuído). Como em geral estes parâmetros não são os mais indicados como atributos de voz para o sistema de reconhecimento remoto, é importante que sejam examinadas diferentes transformações dos parâmetros, que permitam um melhor desempenho do reconhecedor. Esta dissertação trata da extração de atributos de reconhecimento eficientes a partir dos parâmetros dos codificadores utilizados em redes móveis celulares e em redes IP. Além disso, como a taxa dos parâmetros fornecidos ao reconhecedor de voz é normalmente superior àquela com a qual os codificadores geram os parâmetros, é importante analisar o efeito da interpolação dos parâmetros sobre o desempenho do sistema de reconhecimento, bem como o melhor domínio sobre o qual esta interpolação deve ser realizada. Estes são outros tópicos apresentados nesta dissertação. / [en] The huge growth of the Internet and cellular mobile communication systems has stimulated a great interest in the applications of speech processing in these networks. An important problem in this field consists in speech recognition in a server system, based on the acoustic parameters calculated and quantized in the user terminal (Distributed Speech Recognition). Since these parameters are not the most indicated ones for the remote recognition system, it is important to examine different transformations of these parameters, in order to allow a better performance of the recogniser. This dissertation is concerned with the extraction of efficient recognition features from the coder parameters used in cellular mobile networks and IP networks. In addition, as the rate that parameters supplied for the speech recogniser must be usually higher than that generated by the codec, it is important to analyze the effect of the interpolation of the parameters over the performance of the recognition system. Moreover, it is paramount to establish the best domain over which this interpolation must be carried out. These are other topics presented in this dissertation.
506

Uma arquitetura hierárquica baseada em sistema de arquivos para monitoramento de pacotes de rede no sistema operacional GNU/Linux / A hierarchical architecture based on the file system for monitoring network packets on GNU / Linuxoperating system

Leal, Beraldo Costa 14 October 2013 (has links)
Capturar e analisar pacotes de dados que trafegam pelas redes são tarefas essenciais para os administradores de redes. Estas tarefas ajudam na detecção de anomalias nos sistemas e na verificação do estado atual da rede. Existem várias aplicações que desempenham este papel para o sistema operacional GNU/Linux. Estes programas também exportam informações para os usuários e outras aplicações de várias maneiras. Entretanto, não exportam estas informações de forma hierárquica. Esta pesquisa propõe uma arquitetura alternativa aos sistemas atuais. Nossa arquitetura exporta pacotes de dados em uma estrutura hierárquica de arquivos e diretórios. Além disso, por se tratar de uma arquitetura modular, filtros adicionais, desenvolvidos por terceiros, podem ser adicionados ao sistema. A arquitetura proposta acompanha uma implementação de referência: o sistema de arquivos virtuais netsfs (Network Statistics File System), que funciona em espaço de núcleo (kernel space). A arquitetura e o sistema de arquivos netsfs, propostos nesta pesquisa, apresentam um método alternativo para exibir os pacotes de redes. Os resultados mostraram uma aparente melhoria no que diz respeito à vazão da rede. / Capturing and analyzing data packets flowing across networks are essential tasks for network administrators. These tasks help to detect anomalies in the systems and check the current status of a network. There are software applications for the GNU/Linux operating system which perform such tasks. These tools also export their information to users and other applications in different ways. However, current systems do not export this information in a hierarchical manner. This research introduces an alternative architecture to current systems. Our architecture exports data packets in a hierarchical structure of directories and files. Furthermore, since this is a modular architecture, additional third-party filters can be developed and loaded into the system. The proposed architecture comes with a reference implementation: the pseudo file system netsfs (Network Statistics File System), in kernel space. The architecture and the pseudo file system netsfs, developed in this research, introduce an alternative method to display data packets. Results show an apparent improvement regarding network throughput
507

Métodos geofísicos aplicados na avaliação ambiental em uma indústria química na cidade de São Paulo - SP / Geophysical Methods applied in the Environmental Evaluation of a Chemical Industry in the city of São Paulo SP

Marina Minozzo 11 September 2009 (has links)
O uso cada vez maior de derivados de petróleo em processos industriais proporciona a geração de uma diversidade de produtos cada vez mais utilizados pela sociedade atual. As conseqüências negativas do uso e manipulação de hidrocarbonetos é a geração de resíduos e efluentes altamente poluidores. Atualmente, a utilização integrada de técnicas geofísicas podem se constituir em uma ferramenta eficiente na avaliação e caracterização de problemas ambientais. De uma forma geral a utilização da geofísica na caracterização de uma área afetada por substâncias poluentes consiste na detecção e mapeamento da extensão da área afetada e informações sobre a profundidade da zona saturada, direção do fluxo subterrâneo e profundidade do substrato rochoso inalterado. O objetivo principal deste trabalho foi a caracterização geofísica de uma área contaminada por hidrocarbonetos derivados de petróleo, por meio da utilização dos métodos: Eletroresistividade, Polarização Induzida e Eletromagnético Indutivo. Esta caracterização foi realizada através de ensaios de campo e do uso de modelos bidimensionais, tendo como área de estudo uma indústria química localizada no município de São Paulo SP. Esta área foi escolhida com base em estudos precedentes que indicam a ocorrência de contaminação. Os resultados dos modelos de resistividade, cargabilidade e condutividade aparente sugerem a presença de contaminação e seu caminho preferencial, que segue o sentido do fluxo da água subterrânea. Três tipos de anomalias puderam ser individualizadas: a primeira, de baixa resistividade e baixa cargabilidade, que sugerem contaminação mais antiga e a relação com os processos de biodegradação, confirmada através das análises de bactérias; a segunda, de baixa resistividade e alta cargabilidade, geradas pela presença de materiais polarizáveis (metais); e a terceira, as anomalias de alta resistividade e baixa cargabilidade, geradas pela presença do contaminante bruto (sedimento impregnado por tinta), que confirma a contaminação mais recente onde não ocorre processo de biodegradação. / The increasing usage of petroleum derivatives in industrial processes provides a generation of products which are being increasingly used by the contemporary society. The negative consequence from the use and manipulation of hydrocarbons is the generation of residues and highly pollutant effluents. Nowadays, the integrated usage of geophysical techniques can become an efficient tool in the evaluation and characterization of environmental problems. In general, the usage of geophysical in the characterization of an area affected by pollutant substances consists in mapping and detecting the extension of the affected area and inform about the saturated zone deep, the underground flux direction and the deep of the unaltered rocky substrate. The main objective of this research was the geophysical characterization of contaminated area by hydrocarbons derived from petroleum, by the usage of the following methods: Electrical resistivity, Inducted Polarization, and Inductive Electromagnetic. This characterization was carried out through field rehearsals and the usage of two-dimensional models in a chemical industry as study area, placed in the city of São Paulo SP. This area was chosen as the basis in precedent studies which has indicated the event of contamination. The results from the resistivity, chargeability and apparent conductivity models, suggest the presence of contamination and its favorable way, which follows the underground water flux. Three kinds of anomalies could be individualized: first, low resistivity and low chargeability, which suggest older contamination and the relation with the biodegradation processes, confirmed thought the bacterial analysis; second, low resistivity and high chargeability, generated by the presence of polarizable materials (metals); and third, the high resistivity anomalies and low chargeability, generated by the presence of the raw contaminant (paint impregnated sediment), which confirms the most recent pollution where the biodegradation process does not occur.
508

Distribui??o de weibull na emula??o de canal em redes WLAN para avalia??o de VoIP / Weibull distribution in WLAN channel emulation for VoIP evaluation

Bandeira, Alessandra Bussolin 30 October 2007 (has links)
Made available in DSpace on 2016-04-04T18:31:20Z (GMT). No. of bitstreams: 1 Alessandra B Bandeira.pdf: 1200038 bytes, checksum: 316684811248760f05faf3fdda1844f3 (MD5) Previous issue date: 2007-10-30 / This work investigates VoIP (Voice over IP) performance over WLAN (WVoIP) through qualitative and quantitative point of view, considering degradation in indoor environment. The results was obtained through a channel emulator to produce the Weibull distribution. Measurements results with a robot showed that this distribution is adequate to represent WLAN environment instability. The test utilized the CODECs (Coder Decoder) G711 and GSM (Global System for Mobile Communications). The work presents results that indicate the effect of the instability of wireless environment in the VoIP performance. The results indicate a significant variation of voice quality, considering the severity of the phenomena emulated. The behaviors of the CODECs are evaluated considering the different characteristics of bandwidth and robustness. / O trabalho investiga de forma quantitativa e qualitativa o desempenho de VoIP (Voz sobre IP) em uma rede WLAN (Wireless Local ?rea Network), denominado WVoIP, (Wireless VoIP) considerando degrada??o em ambiente indoor. Para atingir esse objetivo foram realizados testes utilizando um emulador de canal capaz de produzir fen?menos de propaga??o com distribui??o de Weibull. Medidas mostram que esta distribui??o ? adequada para avalia??o de instabilidade em redes WLANs. S?o utilizados dois codecs de voz: G711 e GSM (Global System for Mobile Communications). O trabalho apresenta resultados que indicam o efeito dos fen?menos de instabilidade das redes sem fio no desempenho de VoIP, que revelam varia??es significativas na qualidade de voz em fun??o da intensidade dos fen?menos emulados. S?o analisadas as quest?es relativas aos codecs de voz que possuem caracter?sticas de banda e robustez diferentes.
509

Medi??o de Qualidade de voz em Wireless utilizando os codecs G711,G729,G723 e GSM / Measurement of quality of a wireless voice codecs using the G711, G729, G723 and GSM

Almeida, Adenilson Boccato de 18 December 2008 (has links)
Made available in DSpace on 2016-04-04T18:31:26Z (GMT). No. of bitstreams: 1 Adenilson Boccato de Almeida.pdf: 2733171 bytes, checksum: 5b2d37bdad4b16ff26ccb172bbd6fbfc (MD5) Previous issue date: 2008-12-18 / This dissertation examines the quality of the transmission of VoIP (Voice over IP) in wireless LAN (Local Area Network Wireless). To achieve this objective tests were performed on the bench using voice codecs G729, G711, G723 and GSM analyzing characteristics of delay and loss of packets. The paper presents results that indicate the effect of the phenomena of instability of wireless networks in the performance of VoIP. These variations show significant changes in the quality of voice depending on the used environment and the distance between the transmitter and receiver. / Esta disserta??o analisa a qualidade da transmiss?o do VoIP (Voz sobre IP) em rede WLAN (Wireless Local ?rea Network). Para atingir esse objetivo foram realizados testes em bancada utilizando os codecs de voz G729, G711, G723 e GSM analisando suas caracter?sticas de atraso e perda de pacotes. O trabalho apresenta resultados que indicam o efeito dos fen?menos de instabilidade das redes sem fio no desempenho do VoIP. Essas varia??es revelam altera??es significativas na qualidade da voz em fun??o do ambiente utilizado e da dist?ncia entre o emissor e receptor.
510

Proxy IP de baixo custo e m?ltiplos sensores para cidades inteligentes / Proxy IP low cost and multiple sensors to smart cities

Machado, Leandro Filiagi 18 December 2015 (has links)
Made available in DSpace on 2016-04-04T18:31:46Z (GMT). No. of bitstreams: 1 Leandro Filiagi Machado.pdf: 5882687 bytes, checksum: be6f1f6830e339317c23060e0e5453e3 (MD5) Previous issue date: 2015-12-18 / With the advancement of Urban Intelligence and Smart Cities, the importance of remote monitoring and data collection increased. Regarding the monitoring data, the IP Proxy is an important platform for the realization of interconnection between the sensors and the Internet. In recent literature, several gateway architectures for network sensors have been proposed to integrate Wireless Sensor Network (WSN) and Internet. Most WSN gateways implementations retrieve sensor data and display the results to customers via the web. The disadvantage of these solutions is that they use specific protocols to connect the sensors, thereby prohibiting direct interaction between clients and sensor nodes. Optionally, the adoption of sensors for SNMP management has the potential to reduce the complexity of the gateway. For this reason, this paper presents the design and implementation of an open platform and low cost with the use and modification of a non-commercial wireless router with serial connection to communicate with the sensors, which are connected to an Arduino Nano microcontroller. The results showed that applications of the IP Proxy can successfully connect multiple sensors and the Internet, where data can be transmitted all over the world via the Ethernet or WLAN. / Com o avan?o da intelig?ncia Urbana e as Cidades Inteligentes, a import?ncia do monitoramento remoto e coleta de dados aumentou. Em rela??o ao monitoramento de dados, o ProxyIP ? umaplataforma importante para a realiza??oda interconex?o entre os sensores e a Internet. Na literatura recente, v?rias arquiteturas de gateway para sensores de rede t?m sido propostas para integrar Rede de Sensores sem Fio (RSSF) e Internet. A maioria das implementa??es de gateways de RSSF recuperam dados de sensores e exibem os resultados para os clientes via web. A desvantagem dessas solu??es ? que eles usam protocolos espec?ficos para ligar os sensores, proibindo assim a intera??o direta entre clientes e n?s sensores. Como op??o, a ado??o do protocolo SNMP para gerenciamento de sensores tem o potencial para reduzir a complexidade do gateway. Por esta raz?o, este trabalho apresenta a concep??o e implementa??o de uma plataforma aberta e de baixo custo com o uso e modifica??o de um roteador sem fio comercial, com conex?o serial para se comunicar com os sensores, que s?o ligado a um microcontrolador Arduino Nano. Os resultados das aplica??es mostraram que o Proxy IP pode interligar com ?xito multiplos sensores e a Internet, onde os dados podem ser transmitidos em todo o mundo atrav?s da Ethernet ou WLAN.

Page generated in 0.6373 seconds