Energy Efficient Multimedia Communications in IEEE 802.11 Networks

During the last decade wireless mobile communications have progressively become part of the people’s daily lives, leading users to expect to be “alwaysbest-connected” to the Internet, regardless of their location or time of day. This is indeed motivated by the fact that wireless access networks are increasingly ubiquitous, through different types of service providers, together with an outburst of thoroughly portable devices, namely laptops, tablets, mobile phones, among others. The “anytime and anywhere” connectivity criterion raises new challenges regarding the devices’ battery lifetime management, as energy becomes the most noteworthy restriction of the end-users’ satisfaction. This wireless access context has also stimulated the development of novel multimedia applications with high network demands, although lacking in energy-aware design. Therefore, the relationship between energy consumption and the quality of the multimedia applications perceived by end-users should be carefully investigated. This dissertation addresses energy-efficient multimedia communications in the IEEE 802.11 standard, which is the most widely used wireless access technology. It advances the literature by proposing a unique empirical assessment methodology and new power-saving algorithms, always bearing in mind the end-users’ feedback and evaluating quality perception. The new EViTEQ framework proposed in this thesis, for measuring video transmission quality and energy consumption simultaneously, in an integrated way, reveals the importance of having an empirical and high-accuracy methodology to assess the trade-off between quality and energy consumption, raised by the new end-users’ requirements. Extensive evaluations conducted with the EViTEQ framework revealed its flexibility and capability to accurately report both video transmission quality and energy consumption, as well as to be employed in rigorous investigations of network interface energy consumption patterns, regardless of the wireless access technology. Following the need to enhance the trade-off between energy consumption and application quality, this thesis proposes the Optimized Power save Algorithm for continuous Media Applications (OPAMA). By using the end-users’ feedback to establish a proper trade-off between energy consumption and application performance, OPAMA aims at enhancing the energy efficiency of end-users’ devices accessing the network through IEEE 802.11. OPAMA performance has been thoroughly analyzed within different scenarios and application types, including a simulation study and a real deployment in an Android testbed. When compared with the most popular standard power-saving mechanisms defined in the IEEE 802.11 standard, the obtained results revealed OPAMA’s capability to enhance energy efficiency, while keeping end-users’ Quality of Experience within the defined bounds. Furthermore, OPAMA was optimized to enable superior energy savings in multiple station environments, resulting in a new proposal called Enhanced Power Saving Mechanism for Multiple station Environments (OPAMA-EPS4ME). The results of this thesis highlight the relevance of having a highly accurate methodology to assess energy consumption and application quality when aiming to optimize the trade-off between energy and quality. Additionally, the obtained results based both on simulation and testbed evaluations, show clear benefits from employing userdriven power-saving techniques, such as OPAMA, instead of IEEE 802.11 standard power-saving approaches.

A SON Enhanced Algorithm for Observed Time Differences Based Geolocation in Real 3G Networks

Conferência - 16th International Symposium on Wireless Personal Multimedia Communications (WPMC)- Jun 24-27, 2013

Improving accuracy for OTD based 3G geolocation in real urban/suburban environments

This paper presents the recent research results about the development of a Observed Time Difference (OTD) based geolocation algorithm based on network trace data, for a real Universal Mobile Telecommunication System (UMTS) Network. The initial results have been published in [1], the current paper focus on increasing the sample convergence rate, and introducing a new filtering approach based on a moving average spatial filter, to increase accuracy. Field tests have been carried out for two radio environments (urban and suburban) in the Lisbon area, Portugal. The new enhancements produced a geopositioning success rate of 47% and 31%, and a median accuracy of 151 m and 337 m, for the urban and suburban environments, respectively. The implemented filter produced a 16% and 20% increase on accuracy, when compared with the geopositioned raw data. The obtained results are rather promising in accuracy and geolocation success rate. OTD positioning smoothed by moving average spatial filtering reveals a strong approach for positioning trace extracted events, vital for boosting Self-Organizing Networks (SON) over a 3G network.

A comunicação online: a página Web como o BIO Empresarial: estratégias de comunicação visual e web design

Dissertação de mestrado em Ciências da Comunicação (área de especialização em Audiovisuais e Multimédia)

Cooperative Transmission and Radio Resources Management for Wireless Networks

Report for the scientific sojourn at the Multimedia Communications Laboratory, University of Texas at Dallas, USA, from September to December 2005. The cooperative transmission has been analyzed taking a broadcast relay channel which assumes a scenario with one source and multiple destinations. Moreover, in order to improve the performance in terms of mutual information, it has been considered that for each destination there is another nearby terminal (called relay) which will help to improve the performance of the destination. This scheme combines different types of channels considered in the information theory, such as the relay channel, broadcast channel and interference channel (if the relays transmit information intended only to its associated destination). In this work, the author has studied the optimal way to encode the signals for the different users, known as capacity region (i.e. related to radio resources management ), of the broadcast relay channel.

Asymptotic capacity of static multiuser channels with an unknown number of users

We examine a multiple-access communication system in which multiuser detection is performed without knowledge of the number of active interferers. Using a statistical-physics approach, we compute the single-user channel capacity and spectral efficiency in the large-system limit.

DVB-T-testilähetyksen lähettäminen Stadian radiolaboratorion laitteistolla

Tämä insinöörityö tehtiin Helsingin ammattikorkeakoululle. Työssä käsitellään DVB-Tstandardiin perustuvan lähetyslaitteiston kokoonpanoa ja testaamista. Työ perustuu standardeihin, opetusmateriaaliin ja käytännön kokemuksiin. Työ suoritettiin käytännön tutkimuksena. Työssä käsitellään DVB-T-standardia, digitaalisissa tv-lähetyksissä käytettävää MPEG-2 standardia ja siihen liittyen MPEG-2-transport streamia: transport streamin koostumusta, multipleksaamista ja psi/si-taulujen rakennetta. Työssä käydään myös läpi digisovittimen rakennetta ja toimintaperiaatetta, ASIrajapintaa, digitaalisen lähetinyksikön rakennetta ja esitellään Stadian Multimedia Communications- laboratoriossa oleva lähetinyksikkö. Työssä esitetään kuinka moduuleista koostuvalla lähetinlaitteistolla on mahdollista lähettää DVB-T-standardin mukaista testilähetystä. Työn lopputuloksena Stadian laboratorion lähetyslaitteistolla kyettiin lähettämään onnistuneesti testimateriaalia, joka vastaanotettiin kaupallisella digisovittimella.

Planejamento de redes de comunicação sem fio para ambiente indoor considerando os efeitos da polarização das antenas: abordagem baseada em medições

Uma das principais aplicações de ondas eletromagnéticas, na atualidade, na área de telecomunicações trata dos enlaces em sistemas móveis sem fio. Sejam estes terrestres (indoor/outdoor) ou via satélites, o projetista do sistema de telecomunicações tem que ser capaz de determinar os sistemas irradiantes, as potências envolvidas, a frequência de operação do sistema, a área de cobertura e os parâmetros de qualidade do serviço. O planejamento das novas redes de comunicações sem fio representa um grande desafio ao incluir serviços cada vez mais avançados com diferentes requisitos de qualidade, suporte a mobilidade, altas taxas de transmissão e capacidades elevadas de tráfego. Os diversos ambientes nos quais essas redes operam, os fenômenos associados produzem diversos efeitos no comportamento do sinal recebido e, consequentemente, uma variação no desempenho do enlace de comunicação entre os pontos de acesso, a rede e os usuários. Por conseguinte, esses efeitos devem ser avaliados corretamente, de tal forma que o dimensionamento da rede atenda aos requisitos de qualidade regulamentados. O presente trabalho objetiva estabelecer uma metodologia para o planejamento de redes de comunicação sem fio para ambientes indoor, considerando os parâmetros de qualidade de serviços e os efeitos da polarização das antenas. Foi proposto um modelo empírico para determinar a área de cobertura desse ambiente a partir de uma abordagem baseada em medições. Como resultado de campanhas de medições, foram identificados os principais parâmetros que interferem nas perdas no enlace de propagação, destacando-se os materiais envolvidos no ambiente bem como os efeitos da polarização das antenas transmissora, entre outros. Tais efeitos, avaliados corretamente, permitirão ao projetista da rede, de uma forma crítica e com base em dados obtidos em campo, definir a melhor configuração de parâmetros e critérios de projeto para a implantação de uma rede móvel de acesso sem fio. As medições para determinação dos parâmetros de cobertura e de qualidade de serviços foram realizadas no prédio do Laboratório de Engenharia Elétrica e de Computação e no prédio de aulas do Instituto de Tecnologia da Universidade Federal do Pará. Nas campanhas de medição foram utilizadas algumas frequências, escolhidas devido à importância dos serviços disponibilizados: 2,4 GHz - redes locais sem fio (WLAN’s); 3,5 GHz - Wimax licenciado; 5,85 GHz - Wimax livre e 10 GHz (a faixa de 9,8 a 10 GHz não está ainda regulamentada, de 10 - 10,15 GHz-radioamador (Resolução Anatel, Nº 452/2006 - D.O.U. de 20.12.2006) ou serviços de comunicações multimídias (SCM) para sistemas em banda larga). Os principais resultados obtidos com o modelo proposto foram avaliados e comparados com os principais modelos da literatura e mostraram que a metodologia adotada para o planejamento de redes de comunicação sem fio em ambientes indoor teve um bom desempenho.

Internet sex among non-gay identifying men who have sex with men

The aim of this study was to examine the role of the Internet in Internal Homonegativity (IH) among Non gay identifying men who have sex with men (NGI-MSM). This study at University of Texas School of Public Health (UTSPH) had a mixed method research design and consisted of men 18 years of age and older who were residents of the US and Canada. The data were collected using an online survey called 'Men's Sexual Health Survey' which was developed in collaboration with Boston University School of Public Health and Denver Public Health. These surveys were administered in English, which took 30-minutes to complete, and were placed on gay oriented websites and chat rooms. 141 participants were presented with the module relating to IH. A Principal Component Analysis with varimax rotation on the nine questions that asked the participants about their feelings about gay men produced three factors of IH identified as (1) public identification as gay; (2) perception of stigma associated with being gay; and (3) social comfort with gay men. The factors significantly correlated with age, grade completed in school, income, openness about being gay and socializing with gay people, meeting partners online, dating on the Internet, attitude toward condom usage, alcohol and drug use before sex and having unprotected sex with Internet partners. These findings point toward the role of the Internet in determining IH and sexual behavior. Despite the risks, the Internet's popularity and outreach in NGI-MSM makes it an effective medium to spread public health programs.^

Online Video as a Tool for Planning Education and Engagement: A Content Analysis of U.S. City Planning Departments’ YouTube Channels

Thesis (Master's)--University of Washington, 2016-06

Multiplexers and demultiplexers based on fibre Bragg gratings and optical circulators for DWDM systems

Two different architectures of multiplexers/demultiplexers based on 4×1 and 1×4 configurations are discussed. These architectures are implemented using apodized fibre Bragg gratings as optical filters and optical circulators. The spectral characteristics of the devices for channel separations of 100 GHz and 50 GHz are analysed and their performance is evaluated. Optical switch and cross-connect configurations are also demonstrated.

Message from MultiCom-2012 workshop chairs

Welcome to the Second International Workshop on Multimedia Communications and Networking held in conjunction with IUCC-2012 during 25 June – 27 June 2012 in Liverpool, UK. MultiCom-2012 is dedicated to address the challenges in the areas of elivering multimedia content using modern communication and networking techniques. The multimedia & networking computing domain emerges from the integration of multimedia content such as audio and video with content distribution technologies. This workshop aims to cover contributions in both design and analysis aspects in the context of multimedia, wired/wireless/heterogeneous networks, and quality evaluation. It also intends to bring together researchers and practitioners from academia and industry to share their latest achievements in this field with others and establish new collaborations for future developments. All papers received are peer reviewed by three members of the Technical Programme Committee. The papers are assessed by their originality, technical quality, presentation and relevance to the theme of the workshop. Based on the criteria set, four papers have been accepted for presentation at the workshop and will appear in the IUCC conference proceedings. We would like to take this opportunity to thank the IUCC-2012 Organizing Committee, the TPC members of MultiCom-2012 and the authors for their s upport, dedicated work and contributions. Finally, we look forward to meeting you at the workshop in Liverpool.