Atualmente existem inúmeros serviços multimídia que são transportados através da rede IP, dos quais, o tráfego dos serviços de vídeo experimentou um maior crescimento nos últimos anos. O sucesso de aplicações de streaming de vídeo é um dos fatores pelo qual, este tráfego se incrementou. Alguns recentes estudos projetam que este tipo de serviços no ano 2016, alcançará aproximadamente o 55% do tráfego total da Internet. Considerando a importância que os serviços de vídeo alcançarão nos próximos anos, este trabalho foca-se na avaliação da qualidade de experiência (QoE) dos usuários ao utilizar estes serviços. Assim, nesta tese é proposta uma métrica de avaliação de vídeo denominada eVsQM, do inglês enhanced Video streaming Quality Metric, a qual é baseada principalmente no número, duração e localização temporal dos congelamentos de imagens (pausas) durante uma transmissão de vídeo, considerando também o tipo de conteúdo do vídeo transmitido. Esta métrica foi determinada a partir de um modelo matemático que utilizou os resultados de testes subjetivos de avaliação de vídeo, pois, este tipo de testes são os que melhor se aproximam da QoE real do usuário. Cabe destacar, que na realização dos testes subjetivos foi utilizada uma metodologia concordante com o tipo de degradação que o vídeo possui, ou seja, a pausa. No streaming de vídeo novas soluções são criadas com a finalidade de melhorar a QoE do usuário. O DASH, do inglês Dynamic Adaptive Streaming over HTTP, muda a resolução do vídeo transmitido de acordo com as características da rede. Porém, se a rede é muito flutuante existirão muitas variações de resolução e a QoE do usuário será degradada. Neste trabalho é proposto um parâmetro a ser utilizado no algoritmo DASH que funciona como um limiar para controlar a frequência destas comutações de resolução. Este parâmetro é denominado como SDF (do inglês Switching Degradation Factor) e permite que a QoE mantida em níveis aceitáveis, inclusive em situações onde a rede é muito flutuante. Adicionalmente, neste trabalho é proposto um novo modelo de faturamento nos serviços de telecomunicações, que inclua no processo de tarifação um parâmetro relacionado com a QoE, visando ter uma tarifação de serviços de comunicações mais justa do ponto de vista dos usuários. Desta forma, usuários que recebem uma menor qualidade no serviço devem pagar menos em relação aos usuários que recebem uma melhor qualidade do mesmo serviço. / Nowadays, there are several multimedia services, which are carried via IP networks. From these all services; the traffic regarding video applications had the greatest growth in the last years. The success of video streaming applications is one of the major contributors to video traffic growth. Some recent studies project that video services, will reach approximately 55% of the total Internet traffic in 2016. Considering the relevance that video services will achieve in the coming years, this work focuses on the users Quality of Experience (QoE) when using these services. Thus, this thesis proposes an evaluation metric named enhanced Video streaming Quality Metric (eVsQM), which is based primarily on the number, duration and temporal location of the image freezes (pauses) during a video transmission. Also, this metric considers the video content type and was determined from a mathematical model that used as inputs, the video quality assessment results from subjective tests due, these types of test are the most correlated with real users QoE. It is worth noting that to perform these subjective tests was used a methodology consistent with the kind of video degradation (pause). For another hand, new video streaming solutions are created for the purpose of improving the users QoE of the user. Dynamic Adaptive Streaming over HTTP (DASH) changes the video resolution according to the network characteristics. However, if the network is very fluctuant, many video resolution switching events will be performed and users QoE will be degraded. This thesis proposes a parameter to be used in DASH algorithms that works as a threshold to control the resolution switching frequency. This parameter is named Switching Degradation Factor (SDF) and is responsible to maintain the QoE in acceptable levels, inclusive in scenarios in which the network capacity is very fluctuating.

Atualmente existem inúmeros serviços multimídia que são transportados através da rede IP, dos quais, o tráfego dos serviços de vídeo experimentou um maior crescimento nos últimos anos. O sucesso de aplicações de streaming de vídeo é um dos fatores pelo qual, este tráfego se incrementou. Alguns recentes estudos projetam que este tipo de serviços no ano 2016, alcançará aproximadamente o 55% do tráfego total da Internet. Considerando a importância que os serviços de vídeo alcançarão nos próximos anos, este trabalho foca-se na avaliação da qualidade de experiência (QoE) dos usuários ao utilizar estes serviços. Assim, nesta tese é proposta uma métrica de avaliação de vídeo denominada eVsQM, do inglês enhanced Video streaming Quality Metric, a qual é baseada principalmente no número, duração e localização temporal dos congelamentos de imagens (pausas) durante uma transmissão de vídeo, considerando também o tipo de conteúdo do vídeo transmitido. Esta métrica foi determinada a partir de um modelo matemático que utilizou os resultados de testes subjetivos de avaliação de vídeo, pois, este tipo de testes são os que melhor se aproximam da QoE real do usuário. Cabe destacar, que na realização dos testes subjetivos foi utilizada uma metodologia concordante com o tipo de degradação que o vídeo possui, ou seja, a pausa. No streaming de vídeo novas soluções são criadas com a finalidade de melhorar a QoE do usuário. O DASH, do inglês Dynamic Adaptive Streaming over HTTP, muda a resolução do vídeo transmitido de acordo com as características da rede. Porém, se a rede é muito flutuante existirão muitas variações de resolução e a QoE do usuário será degradada. Neste trabalho é proposto um parâmetro a ser utilizado no algoritmo DASH que funciona como um limiar para controlar a frequência destas comutações de resolução. Este parâmetro é denominado como SDF (do inglês Switching Degradation Factor) e permite que a QoE mantida em níveis aceitáveis, inclusive em situações onde a rede é muito flutuante. Adicionalmente, neste trabalho é proposto um novo modelo de faturamento nos serviços de telecomunicações, que inclua no processo de tarifação um parâmetro relacionado com a QoE, visando ter uma tarifação de serviços de comunicações mais justa do ponto de vista dos usuários. Desta forma, usuários que recebem uma menor qualidade no serviço devem pagar menos em relação aos usuários que recebem uma melhor qualidade do mesmo serviço. / Nowadays, there are several multimedia services, which are carried via IP networks. From these all services; the traffic regarding video applications had the greatest growth in the last years. The success of video streaming applications is one of the major contributors to video traffic growth. Some recent studies project that video services, will reach approximately 55% of the total Internet traffic in 2016. Considering the relevance that video services will achieve in the coming years, this work focuses on the users Quality of Experience (QoE) when using these services. Thus, this thesis proposes an evaluation metric named enhanced Video streaming Quality Metric (eVsQM), which is based primarily on the number, duration and temporal location of the image freezes (pauses) during a video transmission. Also, this metric considers the video content type and was determined from a mathematical model that used as inputs, the video quality assessment results from subjective tests due, these types of test are the most correlated with real users QoE. It is worth noting that to perform these subjective tests was used a methodology consistent with the kind of video degradation (pause). For another hand, new video streaming solutions are created for the purpose of improving the users QoE of the user. Dynamic Adaptive Streaming over HTTP (DASH) changes the video resolution according to the network characteristics. However, if the network is very fluctuant, many video resolution switching events will be performed and users QoE will be degraded. This thesis proposes a parameter to be used in DASH algorithms that works as a threshold to control the resolution switching frequency. This parameter is named Switching Degradation Factor (SDF) and is responsible to maintain the QoE in acceptable levels, inclusive in scenarios in which the network capacity is very fluctuating.

Atualmente existe uma grande variedade de serviços de telecomunicações focados na transmissão de voz, vídeo e dados através de redes complexas, embora, em muitos casos, o usuário final não seja atendido com um nível de qualidade aceitável. Neste trabalho, se avalia como o serviço de streaming de vídeo em uma rede com protocolo Internet (IP) pode ser afetado por uma condição adversa da rede, tal como a variação de atraso (jitter). São mostrados os resultados de avaliações objetivas e subjetivas de streaming de vídeo que indicam que a qualidade de vídeo é diretamente afetada por fatores de degradação da rede IP como a variação de atraso de pacotes. Além disso, se verifica que cenas de maior movimento também são mais afetadas pela variação de atraso. Para a realização dos testes, utiliza-se um cenário de emulação de rede isolado, no qual são parametrizadas diferentes condições de rede. Assim, no canal de transmissão são configurados diversos valores de variação de atraso, obtendo-se uma Base de Dados de vídeos com diferentes graus de degradação de qualidade. Estes vídeos são avaliados utilizando métodos subjetivos: Índice por Categorias Absolutas (ACR - Absolute Category Rating) e Índice por Categorias de Degradação (DCR - Degradation Category Rating) e métricas objetivas: Relação Sinal-Ruído de Pico (PSNR - Peak Signal to Noise Ratio), Índice de Similaridade Estrutural (SSIM - Structural Similarity Index) e Medição de Qualidade de Vídeo (VQM - Video Quality Metric). Com a finalidade de mostrar o desempenho das métricas objetivas em relação às subjetivas são empregados os coeficientes de correlação, além do erro de predição e quadrático médio. Adicionalmente, é importante destacar que a partir dos resultados obtidos são estabelecidos intervalos de valores de variação de atraso para os quais a qualidade do vídeo é considerada aceitável ou não para o usuário final. Finalmente, obtém-se uma Base de Dados de vídeos com diferentes graus de degradação da qualidade e que pode ser utilizada em futuras pesquisas. / Nowadays, there is a wide range of telecommunications services focused on the transmission of voice, video and data across complex networks, although, in many cases, the end user is not satisfied with an acceptable quality level. In this work it is assessed how the video streaming service over an IP network can be affected by adverse conditions on the network, such as packet delay variation (jitter). Results from objective and subjective video streaming assessments are shown and indicate that the video quality is directly affected by IP network degradation factors such as packet delay variation. Beyond that, it is also verified that scenes with great movement content are also more sensitive to packet delay variation. For experimental tests, a network emulation totally isolated is considered, for which different network conditions are parameterized. Then, to the transmission channel, different values of packet delay variation are configured and videos are assessed, using subjective metrics: Absolute Category Rating (ACR) and Degradation Category Rating (DCR), and objective metrics: Peak Signal to Noise Ratio (PSNR), Structural Similarity (SSIM) and Video Quality Metric (VQM). In order to show the performance of objective metrics in relation to subjective ones correlation coefficients are employed as well as the prediction error and the mean square error. Finally, it is important to note that, from the results obtained, it can be established a range of delay variation values in which the video quality is acceptable or not at the end user. Additionally, a Video Data Base is obtained with different degrees of quality degradation and which can be used for future researches.

Adaptive resource allocation in wireless communication systems is crucial in order to support the diverse QoS needs of the services and optimize resource utilization. The design of resource allocation schemes should consider the service type for which it is intended. Moreover, due to feedback delay and channel estimation error, the Channel Quality Indicator (CQI) reported to the transmitter may not be a perfect measure of the channel quality and its use for resource allocation may severely degrade the systems performance. In this thesis, we study resource allocation and CQI reporting for wireless networks while taking the aforementioned factors into consideration. First, we consider resource allocation and adaptive modulation in uplink SC-FDMA systems. This is a combinatorial problem whose optimal solution is exponentially complex. We use canonical duality theory to derive a polynomial complexity resource allocation algorithm that provides a nearly optimal solution to the problem. Then, we focus on resource allocation for video streaming in wireless networks with time-varying interference. To this end, by using risk-sensitive control approach, we develop a cross-layer optimization framework that performs power control at the PHY/MAC layer and rate adaptation at the APPLICATION layer jointly and provides fairness among nodes. Finally, by using stochastic control and game theory, we design a robust best-M CQI reporting scheme for multi-carrier and multi-user systems which takes into account the impact of feedback delay and error in CQI computation. Performing resource allocation on the basis of the proposed CQI reporting can significantly improve the system performance.

In this thesis, the problems caused by peer behavior in peer-to-peer (P2P) video streaming is investigated. First, peer behaviors are modeled using two dimensional continuous time markov chains to investigate the reliability of P2P video streaming systems. Then a metric is proposed to evaluate the dynamic behavior and evolution of P2P overlay network. Next, a hybrid geographical location-time and interest based clustering algorithm is proposed to improve the success ratio and reduce the delivery time of required content. Finally, Hybrid Fault Tolerant Video Streaming System (HFTS) over P2P networks has been designed and offered conforming the required Quality of Service (QoS) and Fault Tolerance. The results indicate that the required QoS can be achieved in streaming video applications using the proposed hybrid approach.

Internet Protocol Television (IPTV) has become the application that drives the Internet to a new height. However, challenges still remain in IPTV in-home distribution. The high-quality video streaming in IPTV services demands home networks to deliver video streaming packets with stringent Quality-of-Service (QoS) requirements. Currently, most service providers recommend Ethernet-based broadband home networks for IPTV. However, many existing houses are not wired with Ethernet cables and the rewiring cost is prohibitively expensive. Therefore, wireless solutions are preferred if their performance can meet the requirements. IEEE 802.11 wireless local area networks (WLANs) are pervasively adopted in home networks for their flexibility and affordability. However, through our experiments in the real environment, we found that the conventional single-hop infrastructure mode WLANs have very limited capacity and coverage in a typical in-door environment due to high attenuation and interference. The single-hop wireless networks cannot provide support for high-quality video streaming to the entire house. Multi-hop wireless networks are therefore used to extend the coverage. Contrary to the common believes that adding relay routers in the same wireless channel should reduce the throughput, our experiment, analysis and simulation results show that the multi-hop IEEE 802.11 WLANs can improve both the capacity and coverage in certain scenarios, and sufficiently support high-quality video streaming in a typical house. In this research, we analyzed and evaluated the performance of H.264-based video streaming over multi-hop wireless networks. Our analysis and simulation results reveal a wide spectrum of coverage-capacity tradeoff of multi-hop wireless networks in generic scenarios. More- over, we discuss the methods of how to further improve video streaming performance. This research provides the guidance on how to achieve the optimal balance for a given scenario, which is of great importance when deploying end-to-end IPTV services with QoS guarantee.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xix, 136 p.; also includes graphics (some col.). Includes bibliographical references (p. 129-136). Available online via OhioLINK's ETD Center

<p>The accessibility and flexibility of mobile devices make them an advantageous platform for gaming, but there are hardware limitations that impede the rendering of high-quality graphics. Rendering complex graphics on a mobile device typically results in a delayed image, also known as latency, and is a great discomfort for users of any real-time rendering experience. This study tests the image stream optimization View Bypass within a cloud gaming architecture, surpassing this imposing limitation by processing the high-quality game render on a remote computational server. A two sample for means test is performed to determine significance between two treatments: the control group without the View Bypass algorithm and the experimental group rendering with the View Bypass algorithm. A SSIM index score is calculated comparing the disparity between the remote server image output and the final mobile device image output after optimizations have been performed. This score indicates the overall image structural integrity difference between the two treatments and determines the quality and effectiveness of the tested algorithm.</p>

Vehicular ad-hoc networks (VANETs) are used for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. The IEEE 802.11p/WAVE (Wireless Access in Vehicular Environment) and with WAVE Short Messaging Protocol (WSMP) has been proposed as the standard protocol for designing applications for VANETs. This communication protocol must be thoroughly tested before reliable and efficient applications can be built using its protocols. In this paper, we perform on-road experiments in a variety of scenarios to evaluate the performance of the standard. We use commercial VANET devices with 802.11p/WAVE compliant chipsets for both BSM (basic safety messages) as well as video streaming applications using WSMP as a communication protocol. We show that while the standard performs well for BSM application in lightly loaded conditions, the performance becomes inferior when traffic and other performance metric increases. Furthermore, we also show that the standard is not suitable for video streaming due to the bursty nature of traffic and the bandwidth throttling, which is a major shortcoming for V2X applications.

Subject of this thesis was the issue of effectiveness of wireless networks from the perspective of services. Become acquainted with WiFi network standard IEEE 802.11 with protocols and principles of WiFi networks and services. It should be focused on the quality of service QoS. In teoretical part of this thesis are described problems considering wireless networks, layer model and types of nets used in WiFi. Standard IEEE 802.11 is analysed in details including supplements and used packets. Special attention is paid to the quality of service QoS. Next are discussed the principles and application services as VoIP, videoconferencing, video streaming and others in WiFi network. On the basis of obtained knowledge is designed extensive WiFi network with assured supply of services. For modelling and simulation of wireless network is used software development environment Opnet Modeler. Model of wireless network is used to optimize and analyse this wireless communication network. In thesis are also simulated properties of data which are sensitive to delay. In last part of thesis is created a laboratory work, which contains a submission of task, detailed theory, wiring diagram, instructions for elaboration, guidelines for simulation and example of elaboration of task. Work is about comparison of network with used 802.11b and 802.11e standard, and support of quality of service QoS.