On the Privacy of Encrypted Skype Communications

The privacy of voice over IP (VoIP) systems is achieved by compressing and encrypting the sampled data. This paper investigates in detail the leakage of information from Skype, a widely used VoIP application. In this research, it has been demonstrated by using the dynamic time warping (DTW) algorithm, that sentences can be identified with an accuracy of 60%. The results can be further improved by choosing specific training data. An approach involving the Kalman filter is proposed to extract the kernel of all training signals.

Shadowed Fading in Indoor Off-Body Communications Channels: A Statistical Characterization using the κ – μ / Gamma Composite Fading Model

This paper investigates the characteristics of the shadowed fading observed in off-body communications channels at 5.8 GHz. This is realized with the aid of the $\kappa-\mu$ / gamma composite fading model which assumes that the transmitted signal undergoes $\kappa-\mu$ fading which is subject to \emph{multiplicative} shadowing. Based on this, the total power of the multipath components, including both the dominant and scattered components, is subject to non-negligible variations that follow the gamma distribution. For this model, we present an integral form of the probability density function (PDF) as well as important analytic expressions for the PDF, cumulative distribution function, moments and moment generating function. In the case of indoor off-body communications, the corresponding measurements were carried out in the context of four explicit individual scenarios namely: line of sight (LOS) and non-LOS (NLOS) walking, rotational and random movements. The measurements were repeated within three different indoor environments and considered three different hypothetical body worn node locations. With the aid of these results, the parameters for the $\kappa-\mu$ / gamma composite fading model were estimated and analyzed extensively. Interestingly, for the majority of the indoor environments and movement scenarios, the parameter estimates suggested that dominant signal components existed even when the direct signal path was obscured by the test subject's body. Additionally, it is shown that the $\kappa-\mu$ / gamma composite fading model provides an adequate fit to the fading effects involved in off-body communications channels. Using the Kullback-Leibler divergence, we have also compared our results with another recently proposed shadowed fading model, namely the $\kappa-\mu$ / lognormal LOS shadowed fading model. It was found that the $\kappa-\mu$ / gamma composite fading model provided a better fit for the majority of the scenarios considered in this study.

Switched Diversity Techniques for Indoor Off-body Communications Channels: An Experimental Analysis and Modeling

This paper investigates the potential improvement in signal reliability for indoor off-body communications channels operating at 5.8 GHz using switched diversity techniques. In particular we investigate the performance of switch-and-stay combining (SSC), switch-and-examine combining (SEC) and switch-and-examine combining with post-examining selection (SECps) schemes which utilize multiple spatially separated antennas at the base station. During the measurements a test subject, wearing an antenna on his chest, performed a number of walking movements towards and then away from a uniform linear array. It was found that all of the considered diversity schemes provided a worthwhile signal improvement. However, the performance of the diversity systems varied according to the switching threshold that was adopted. To model the fading envelope observed at the output of each of the combiners, we have applied diversity specific equations developed under the assumption of Nakagami-$m$ fading. As a measure of the goodness-of-fit, the Kullback-Leibler divergence between the empirical and theoretical probability density functions (PDFs) was calculated and found to be close to 0. To assist with the interpretation of the goodness-of-fit achieved in this study, the standard deviation, $\sigma$, of a zero-mean, $\sigma^2$ variance Gaussian PDF used to approximate a zero-mean, unit variance Gaussian PDF is also presented. These were generally quite close to 1 indicating that the theoretical models provided an adequate fit to the measured data.

Cooperative communications in multi-rate IEEE 802.11 networks

Esta tese apresenta um estudo sobre alguns dos protocolos de cooperação MAC para redes sem fios utilizando o sistema IEEE 802.11 multi-débito. É proposto um novo modelo de arquitetura para a categorização e análise da cooperação em redes sem fios, tendo este modelo sido aplicado a protocolos cooperativos existentes para camada MAC. É investigado como as características do meio físico, assim como os requisitos de níveis superiores podem ser aplicados ao processo de cooperação, com vista a melhorar as características de funcionamento da rede de comunicações. Para este propósito são exploradas as métricas mais relevantes para o processo de cooperação. São igualmente estudados os limites impostos pelos protocolos da camada MAC e as limitações práticas impostas por protocolos da família de normas que compõem o IEEE 802.11. Neste trabalho foi criada uma métrica multicamada, que permite considerar os requisitos aplicacionais de performance e o tipo de tráfego, assim como a mobilidade dos dispositivos, no funcionamento dos mecanismos de cooperação. Como forma de validação, e para corretamente avaliar o impacto da métrica, um novo protocolo de cooperação foi desenvolvido e implementado. O seu funcionamento é descrito de forma analítica assim como validado através de a um ambiente de simulação. Os resultados obtidos mostram que a utilização de uma métrica multicamada é uma técnica robusta, fornecendo melhorias consistentes no contexto de redes IEEE 802.11. São igualmente demonstradas várias outras características de funcionamento com impacto para as comunicações. Estes dados fornecem uma visão real e encorajadora para a realização de mais pesquisas para a melhoria da performance dos protocolos cooperativos, assim como a sua utilização num variado número de aplicações futuras. No final do documento são apresentados alguns desafios para a continuação da investigação deste tópico.

Analysis, modeling, design and optimization of future communications systems: from theory to practice

Esta tese descreve uma framework de trabalho assente no paradigma multi-camada para analisar, modelar, projectar e optimizar sistemas de comunicação. Nela se explora uma nova perspectiva acerca da camada física que nasce das relações entre a teoria de informação, estimação, métodos probabilísticos, teoria da comunicação e codificação. Esta framework conduz a métodos de projecto para a próxima geração de sistemas de comunicação de alto débito. Além disso, a tese explora várias técnicas de camada de acesso com base na relação entre atraso e débito para o projeto de redes sem fio tolerantes a atrasos. Alguns resultados fundamentais sobre a interação entre a teoria da informação e teoria da estimação conduzem a propostas de um paradigma alternativo para a análise, projecto e optimização de sistemas de comunicação. Com base em estudos sobre a relação entre a informação recíproca e MMSE, a abordagem descrita na tese permite ultrapassar, de forma inovadora, as dificuldades inerentes à optimização das taxas de transmissão de informação confiáveis em sistemas de comunicação, e permite a exploração da atribuição óptima de potência e estruturas óptimas de pre-codificação para diferentes modelos de canal: com fios, sem fios e ópticos. A tese aborda também o problema do atraso, numa tentativa de responder a questões levantadas pela enorme procura de débitos elevados em sistemas de comunicação. Isso é feito através da proposta de novos modelos para sistemas com codificação de rede (network coding) em camadas acima da sua camada física. Em particular, aborda-se a utilização de sistemas de codificação em rede para canais que variam no tempo e são sensíveis a atrasos. Isso foi demonstrado através da proposta de um novo modelo e esquema adaptativo, cujos algoritmos foram aplicados a sistemas sem fios com desvanecimento (fading) complexo, de que são exemplos os sistemas de comunicação via satélite. A tese aborda ainda o uso de sistemas de codificação de rede em cenários de transferência (handover) exigentes. Isso é feito através da proposta de novos modelos de transmissão WiFi IEEE 801.11 MAC, que são comparados com codificação de rede, e que se demonstram possibilitar transferência sem descontinuidades. Pode assim dizer-se que esta tese, através de trabalho de análise e de propostas suportadas por simulações, defende que na concepção de sistemas de comunicação se devem considerar estratégias de transmissão e codificação que sejam não só próximas da capacidade dos canais, mas também tolerantes a atrasos, e que tais estratégias têm de ser concebidas tendo em vista características do canal e a camada física.

Dependable wireless real-time communications for open environments

Wireless communication technologies have become widely adopted, appearing in heterogeneous applications ranging from tracking victims, responders and equipments in disaster scenarios to machine health monitoring in networked manufacturing systems. Very often, applications demand a strictly bounded timing response, which, in distributed systems, is generally highly dependent on the performance of the underlying communication technology. These systems are said to have real-time timeliness requirements since data communication must be conducted within predefined temporal bounds, whose unfulfillment may compromise the correct behavior of the system and cause economic losses or endanger human lives. The potential adoption of wireless technologies for an increasingly broad range of application scenarios has made the operational requirements more complex and heterogeneous than before for wired technologies. On par with this trend, there is an increasing demand for the provision of cost-effective distributed systems with improved deployment, maintenance and adaptation features. These systems tend to require operational flexibility, which can only be ensured if the underlying communication technology provides both time and event triggered data transmission services while supporting on-line, on-the-fly parameter modification. Generally, wireless enabled applications have deployment requirements that can only be addressed through the use of batteries and/or energy harvesting mechanisms for power supply. These applications usually have stringent autonomy requirements and demand a small form factor, which hinders the use of large batteries. As the communication support may represent a significant part of the energy requirements of a station, the use of power-hungry technologies is not adequate. Hence, in such applications, low-range technologies have been widely adopted. In fact, although low range technologies provide smaller data rates, they spend just a fraction of the energy of their higher-power counterparts. The timeliness requirements of data communications, in general, can be met by ensuring the availability of the medium for any station initiating a transmission. In controlled (close) environments this can be guaranteed, as there is a strict regulation of which stations are installed in the area and for which purpose. Nevertheless, in open environments, this is hard to control because no a priori abstract knowledge is available of which stations and technologies may contend for the medium at any given instant. Hence, the support of wireless real-time communications in unmanaged scenarios is a highly challenging task. Wireless low-power technologies have been the focus of a large research effort, for example, in the Wireless Sensor Network domain. Although bringing extended autonomy to battery powered stations, such technologies are known to be negatively influenced by similar technologies contending for the medium and, especially, by technologies using higher power transmissions over the same frequency bands. A frequency band that is becoming increasingly crowded with competing technologies is the 2.4 GHz Industrial, Scientific and Medical band, encompassing, for example, Bluetooth and ZigBee, two lowpower communication standards which are the base of several real-time protocols. Although these technologies employ mechanisms to improve their coexistence, they are still vulnerable to transmissions from uncoordinated stations with similar technologies or to higher power technologies such as Wi- Fi, which hinders the support of wireless dependable real-time communications in open environments. The Wireless Flexible Time-Triggered Protocol (WFTT) is a master/multi-slave protocol that builds on the flexibility and timeliness provided by the FTT paradigm and on the deterministic medium capture and maintenance provided by the bandjacking technique. This dissertation presents the WFTT protocol and argues that it allows supporting wireless real-time communication services with high dependability requirements in open environments where multiple contention-based technologies may dispute the medium access. Besides, it claims that it is feasible to provide flexible and timely wireless communications at the same time in open environments. The WFTT protocol was inspired on the FTT paradigm, from which higher layer services such as, for example, admission control has been ported. After realizing that bandjacking was an effective technique to ensure the medium access and maintenance in open environments crowded with contention-based communication technologies, it was recognized that the mechanism could be used to devise a wireless medium access protocol that could bring the features offered by the FTT paradigm to the wireless domain. The performance of the WFTT protocol is reported in this dissertation with a description of the implemented devices, the test-bed and a discussion of the obtained results.

Day 1. Free Communications – Psychology (Session 2): The influence of body language and expected competency on gaze behaviour while forming an initial impression of a tennis player.

D1.S3.4(4). BASES Conference 2015 (Burton-on-Trent), 1-2 December. British Association of Sport and Exercise Sciences

Adaptive transceiver - antenna techniques for mobile broadband communications at millimetre - wave frequencies

This paper is concerned with the implementation of a Mobile Broadband System, currently under research in Europe. We present a low-complexity, adaptive transceiver/antenna approach where simple, linear, phased arrays are adjusted under a transmission quality measurement provided by a decision-feedback equalizer. Several simulation results are presented and discussed.

Dis)located Olympic Patriots: Sporting Connections, Administrative Communications and Imperial Ether in Interwar New Zealand

During the interwar period (1919-1939) protagonists of the early New Zealand Olympic Committee [NZOC] worked to renegotiate and improve the country’s international sporting participation and involvement in the International Olympic Committee [IOC]. To this end, NZOC effectively used its locally based administrators and well-placed expatriates in Britain to variously assert the organisation’s nascent autonomy, independence and political power, progress Antipodean athlete’s causes, and, counter any potential doubt about the nation’s peripheral position in imperial sporting dialogues. Adding to the corpus of scholarship on New Zealand’s ties and tribulations with imperial Britain (in and beyond sport) (e.g. Beilharz and Cox 2007; Belich 2001, 2007; Coombes 2006; MacLean 2010; Phillips 1984, 1987; Ryan 2004, 2005, 2007), in this paper I examine how the political actions and strategic location of three key NZOC agents (specifically, administrator Harry Amos and expatriates Arthur Porritt and Jack Lovelock) worked in their own particular ways to assert the position of the organisation within the global Olympic fraternity. I argue that the efforts of Amos, Porritt and Lovelock also concomitantly served to remind Commonwealth sporting colleagues (namely Britain and Australia) that New Zealand could not be characterised as, or relegated to being, a distal, subdued, or subservient colonial sporting partner. Subsequently I contend that NZOC’s development during the interwar period, and particularly the utility of expatriate agents, can be contextualised against historiographical shifts that encourage us to rethink, reimagine, and rework narratives of empire, colonisation, national identity, commonwealth and belonging.

(Dis)located Olympic Patriots: Sporting Connections, Administrative Communications and Imperial Ether in Interwar New Zealand

During the interwar period (1919–1939), protagonists of the early New Zealand Olympic Committee (NZOC) worked to renegotiate and improve the country's international sporting participation and involvement in the International Olympic Committee. To this end, NZOC effectively used its locally based administrators and well-placed expatriates in Britain to variously assert the organization's nascent autonomy, independence and political power, progress Antipodean athlete's causes and counter any potential doubt about the nation's peripheral position in imperial sporting dialogues. Adding to the corpus of scholarship on New Zealand's ties and tribulations with imperial Britain, both in and beyond sport (e.g. Beilharz and Cox, 2007, “Settler Capitalism Revisited,” Thesis Eleven 88: 112–124; Belich, 2001, Paradise Reforged: A History of the New Zealanders from the 1880s to the Year 2000, Auckland: Allen Lane; Belich, 2007, Making Peoples: A History of the New Zealanders from Polynesian Settlement to the End of the Nineteenth Century, Auckland: The Penguin Group; Coombes, 2006, Rethinking Settler Colonialism: History and Memory in Australia, Canada, Aotearoa New Zealand and South Africa, Manchester: Manchester University Press; MacLean, 2010, “New Zealand (Aotearoa),” In Routledge Companion to Sports History, edited by Steve W. Pope and John Nauright, 510–525, London: Routledge; Phillips, 1984, “Rugby, War and the Mythology of the New Zealand Male,” The New Zealand Journal of History 18 (1): 83–103; Phillips, 1987, A Man's Country: The Image of the Pakeha Male, Auckland: Penguin Books; Ryan, 2004, The Making of New Zealand Cricket, 1832–1914, London: Frank Cass; Ryan, 2005, Tackling Rugby Myths: Rugby and New Zealand Society 1854–2004, Dunedin: University of Otago Press; Ryan, 2007, “Sport in 19th-Century Aotearoa/New Zealand: Opportunities and Constraints,” In Sport in Aotearoa/New Zealand Society, edited by Chris Collins and Steve Jackson, 96–111, Auckland: Thomson), I will examine how the political actions and strategic location of three key NZOC agents (specifically, administrator Harry Amos and expatriates Arthur Porritt and Jack Lovelock) worked in their own particular ways to assert the position of the organization within the global Olympic fraternity. I argue that the efforts of Amos, Porritt and Lovelock also concomitantly served to remind Commonwealth sporting colleagues (namely Britain and Australia) that New Zealand could not be characterized as, or relegated to being, a distal, subdued or subservient colonial sporting partner. Subsequently, I contend that NZOC's development during the interwar period, and particularly the utility of expatriate agents, can be contextualized against historiographical shifts that encourage us to rethink, reimagine and rework narratives of empire, colonization, national identity, commonwealth and belonging.

Georg Lukács as a Communications Scholar: Cultural and Digital Labour in the Context of Lukács’ Ontology of Social Being

The task of this work is to apply thoughts from Georg Lukács’ final book, the Ontology of Social Being, for the theoretical analysis of cultural and digital labour. It discusses Lukács’ concepts of work and communication and relates them to the analysis of cultural and digital work. It also analyses his conception of the relation of labour and ideology and points out how we can make use of it for critically understanding social media ideologies. Lukács opposes the dualist separation of the realms of work and ideas. He introduces in this context the notion of teleological positing that allows us to better understand cultural and digital labour as well as associated ideologies, such as the engaging/connecting/sharing-ideology, today. The analysis shows that Lukács’ Ontology is in the age of Facebook, YouTube, and Twitter still a very relevant book, although it has thus far not received the attention that it deserves. This article also introduces the Ontology’s main ideas on work and culture, which is important because large parts of the book have not been translated from the German original into English. Lukács’ notion of teleological positing is crucial for understanding the common features of the economy and culture.

Impact of the financial crisis on cross-border mergers and acquisitions and concentration in the global banking industry

The global banking industry has seen dramatic changes in the past 40 years. Most recently, the financial liberalization of emerging markets and the global financial crisis have significantly impacted the market share of banks worldwide. This article investigates the impact of the 2007–2008 financial crisis on cross-border mergers and acquisitions (M&As) in the banking sector and emphasizes the role of emerging-market banks in the postcrisis consolidation trend. Using M&A data and concentration data over the period 2000–2013, our analysis indicates that the financial crisis had a significant impact on worldwide M&As, especially on the direction of the transactions. Emerging-market banks appear to be major acquirers in the postcrisis period, targeting both neighboring countries and developed economies in Europe. We also observe an increase in bank concentration in developed markets most hit by the financial crisis, especially in the United States and the United Kingdom, whereas bank concentration decreased in emerging markets.

Mobile Banking: fatores determinantes na adesão

Dissertação apresentada à Escola Superior de Comunicação Social para obtenção de grau de mestre em Publicidade e Marketing.