Made available in DSpace on 2014-06-12T16:01:05Z (GMT). No. of bitstreams: 2 arquivo7156_1.pdf: 2405287 bytes, checksum: 63f88801321ea61b8de43e420495d1b8 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / A tecnologia de Voz sobre IP (VoIP) nasceu da necessidade da convergência das redes de telefonia e dados, aproveitando uma infra-estrutura de alcance mundial, a Internet. Esta tecnologia traz como vantagem a redução dos custos telefônicos, além da possibilidade de agregar novos serviços à telefonia. A tecnologia de Voz sobre IP é o resultado da pesquisa em busca de novas soluções tecnológicas, numa área que movimenta milhões em dólares, a área de telecomunicações, podendo se tornar um fenômeno na Internet, assim como os aplicativos de e-mails e mensagens instantâneas. Muitas iniciativas de projetos de VoIP têm surgido nos últimos anos. Dentre essas iniciativas temos o Skype, um aplicativo VoIp de grande sucesso. O Skype é um aplicativo de VoIP que usa a tecnologia peer-to-peer (P2P) híbrida, chamando atenção pela qualidade de transmissão da voz. O Skype é uma empresa de telefonia virtual, oferecendo chamadas telefônicas gratuitas entre computadores no mundo inteiro. Possui, ainda, as soluções SkypeIn e SkypeOut para o acesso a Rede Pública de Telefonia. Outra iniciativa de aplicativos na tecnologia VoIP é o XVoice. O XVoice foi um dos resultados do Grupo de Trabalho GT-P2P da Rede Nacional de Pesquisa (RNP), sendo projetado para avaliar o tráfego de voz na rede da RNP. O levantamento de requisitos para desenvolver o XVoice demandou um estudo aprofundado sobre o Skype e os protocolos e codecs que são utilizados em aplicações de Voz sobre IP. O XVoice é um aplicativo VoIP que usa a tecnologia peer-to-peer pura. Peer-to-peer é um modelo de comunicação no qual cada nó tem as mesmas capacidades e responsabilidades, e ambos podem iniciar uma sessão de comunicação, contrastando com o modelo cliente/servidor. O objetivo deste trabalho é avaliar os aplicativos de VoIP Skype e XVoice, descrevendo a metodologia e ferramentas utilizadas nesta avaliação. Na avaliação realizada neste trabalho, observou-se que os aplicativos Skype e XVoice possuem desempenhos similares, conforme mostrado nos resultados obtidos

The project is a practical and theoretical test of IP telephony with Skype in order to form a base for a comparison between IP-Telephony with Skype and the Public Switched Telephony Network (PSTN). PSTN is the common standard that most of us use for telephony today. The objective for the study is to simplify the choice between PSTN and IP-Telephony for the Swedish private customer user group. The project is supposed to answer the following questions. - How easy is it to start using IP-telephony with Skype? - How is the quality of IP-telephony compared to PSTN? - Are all services provided by PSTN available and accessible using the IP-solution? - How are the usability and the availability of support with IP telephony? - Is IP-telephony a cheaper solution and in that case under which circumstances? Within the project a collection of practical and theoretical tests have been performed to be able to form an opinion on the IP-solution in the following areas, installation, function, quality, usability, costs, accessibility and security. In order to study usability, a test group of ten persons have been used to evaluate the usability of the system. A practical test of the Skype client has been committed through a series of test calls to examine function and quality. Data on accessibility, cost and security of the Skype solution have been examined in relevant literature and on the Internet. The study shows that the Skype solution works as well as PSTN considering function and quality. A certain amount of computer knowledge is required to install and to used the Skype solution, thereby it is not as user friendly as the PSTN. Considering the costs, it is only possible to save money for those who make a large amount of international calls. In other cases the Skype solution is more expensive. Skype themselves are very clear that they do not provide the function of emergency calls. This is considered as a large setback reviewing the possibility of replacing your PSTN telephone with the Skype solution. The conclusion based on the facts and arguments in this report is that the IP-solution is not an alternative for the Swedish private customer user group in general, compared to PSTN. / Arbetet är en praktisk och teoretisk test av IP-telefoni med Skype som ligger till grund för en jämförelse mot telefoni med PSTN (Public Switched Telephone Network) som är den vanliga telefonstandard de flesta av oss använder idag. Syftet med arbetet är att underlätta valet mellan PSTN och IP-telefoni för privatanvändare i Sverige. Arbetet är tänkt att svara på följande frågeställningar. - Hur enkelt är det att komma igång med IP-telefoni via Skype? - Hur är kvalitén på IP-telefonisamtal jämfört med PSTN? - Fungerar alla de tjänster man har med PSTN även med IP-telefoni? - Hur är användbarheten och tillgängligheten till hjälp och support med IP-telefonin? - Är det billigare att ringa med IP-telefoni och i så fall under vilka förutsättningar? I arbetet har en samling praktiska och teoretiska undersökningar genomförts för att kunna bedöma IP-telefonin med Skype inom följande bedömningsområden. Installation, funktion, kvalitet, användbarhet, kostnader, tillgänglighet och säkerhet. Till undersökningen av användbarhet har en testgrupp på 10 personer använts för att utvärdera systemets användbarhet. En praktisk test av Skypeklientens funktion och kvalitet har utförts genom ett antal provringningar. Skypelösningens tillgänglighet, kostnader och säkerhet har studerats i relevant litteratur och genom fakta på Internet. Resultaten av undersökningen visar att Skypelösningen fungerar lika bra som PSTN med avseende på funktion och kvalitet men det krävs en viss datorvana för att installera och använda lösningen vilket har en viss negativ inverkan på användbarheten. Prismässigt lönar det sig bara för de som ringer mycket utomlands, för övriga användare blir det oftast betydligt dyrare än telefoni med PSTN. Skype själva informerar tydligt om att det inte garanterar funktionen för nödsamtal vilket är en stor nackdel om man vill ersätta sin PSTN-telefon med Skypelösningen. På grund av ovanstående argument så är IP-telefoni med Skype för de flesta användare inte ett bra alternativ till PSTN.

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Les activités interactives en ligne connaissent une utilisation grandissante, notamment dans le domaine de l’enseignement des langues. L’amélioration technique des dispositifs permet en effet aujourd’hui des échanges synchrones à distance avec un locuteur natif.Le tuteur inscrit dans une communication via une plateforme synchrone en ligne doit alors coordonner un ensemble complexe d'opérations à des fins d’apprentissage. Différents modes de communication (textuel, visuel, auditif) sont à sa disposition et il les combine dans son discours. Nous analysons, dans le cadre de cours de français à distance via Skype, quels modes sont utilisés par chacun des quatre tuteurs qui composent notre étude. Nous postulons que les modes sont utilisés différemment par chaque tuteur et nous cherchons donc à savoir dans quelle proportion et avec quel « degré d’investissement » (Develotte, Guichon, Vincent, 2011). Nous cherchons également à comprendre quelles conséquences ces choix d’utilisations des modes ont sur la nature de l’interaction. Nous émettons en effet deux hypothèses. Premièrement, nous pensons que le profil initial des tuteurs (compétences individuelles, expériences professionnelles en présentiel ou à distance, habitude de l’environnement informatique) et le contexte des interactions (perturbations extérieures, problèmes techniques, type de tâche, besoin exprimé des apprenants) ont une influence sur la façon dont le tuteur utilise les modes à disposition.Deuxièmement, nous pensons que les choix d’utilisations influencent la nature de l’interaction et la relation entre tuteurs et apprenants. Nous proposons ainsi une grille d’analyse des interactions multimodales en ligne, afin d’apporter des réponses à nos hypothèses de recherche. / Online interactive activities are increasingly used, notably in the field of language teaching. The technical improvements enable synchronous long distance exchanges with a native speaker. The tutor engaged in a communication via a synchronous online platform must coordinate a complex set of operations for learning purposes. He can combine the different communication modes which are at his disposal (textual, visual and aural). We analyze, in the case of French lessons via Skype, which modes are used by each of the four tutors in our study. We postulate that the modes are differently used by each tutor and we seek to know in what proportion and with which “degree of utilization” (Develotte, Guichon, Vincent, 2011). We also try to understand what consequences the choice of the method has on the nature of the interaction. We present two hypotheses. First, we think that the initial profile of the tutors (individual skills, professional experience with face to face or distance teaching, comfort with the computer environment) and the context of the interactions (exterior perturbations, technical problems, type of task, needs expressed by the learners) have an influence on the way the tutor uses the modes. Secondly, we think that the choices influence the nature of the interaction and the relation between tutors and learners. We propose a grid of analysis of the multimodal online interactions in order to sustain our research hypotheses.

This paper discusses the conditional factors indicating market susceptibility toward disruptive innovation. There is a need to separate the different forms of disruptive innovation into segments targeting; technology, product or business model disruption. The concepts are fundamentally different and the literature to date is very one sided toward disruptive technology/product innovation. A shortage of studies on disruptive business model innovation has been discovered. This study therefore presents a framework for evaluating the market susceptibility toward disruptive business model innovation. This paper is a case study looking at two historical cases in the Swedish telecom industry. One case was a highly successful disruptive business model whilst the other has not reached the potential success it could have. The cases are investigated through interviews from persons with strategic positions in the telecom industry during the launch of the business models presented in the cases. This is backed with survey results and statistics from market research conducted by the Swedish post and telecom authority. Conditional factors applied to disruptive technology/product innovations, found in previous studies and theory, are applied to the business model disruption cases. The conditional factors are tested in order to establish to what extent they can be applied on business model disruption. This study also aims to find new conditional factors not covered in previous theory. This study is concluded by presenting 10 conditional factors important for evaluating susceptibility toward disruptive business model innovation. This paper analyses 11 conditional factors from previous theory applied on disruptive technology/product innovation. Out of these, 7 conditional factors can be transferred from disruptive technology/product innovation to disruptive business model innovation theory, whilst 4 conditional factors are dismissed entirely. In addition, 3 conditional factors are added from the empirical findings. The study found that the “change of actors in the value chain” and “high entrance barriers” did not seem to be as important for business model disruption. Market susceptibility in these cases seemed to be more dependent on cost, end customer focus, high margins and scalability. There were however also many conditional factors which have importance both for disruptive business model innovation and disruptive technology/product innovation. These conditional factors concerned the market distribution, the current product, the profitability of the market and the current value chain. Differences between disruptive business model innovation and disruptive technology/product innovation are discovered. The differences are proven crucial when evaluating the market susceptibility toward disruptive innovation. Mainly differences being that business models; are more agile, are not seen as big threats, and seem to be more pull than push oriented. / Den här studien behandlar de faktorer som indikerar en marknads känslighet för disruptiva innovationer. Dessa disruptiva innovationer kan delas upp i tre olika former; produktdisruption, teknologidisruption och affärsmodellsdisruption. Det finns idag en brist på litteratur som behandlar disruption ur ett affärsmodellsperspektiv. Befintlig litteratur för disruptiva innovationer är baserade på fall kring teknologi- och produktdisruptioner. Denna studie presenterar ett ramverk för att utvärdera känsligheten för affärsmodellsdisruption i en viss marknad. I den här artikeln görs en fallstudie kring två historiska händelser då nya affärsmodeller lanserats på den svenska telekommarknaden. En utav dessa var en väldigt framgångsrik affärsmodellsdisruption, medan den andra inte nått samma framgång. Händelserna är undersökta genom intervjuer av personer som hade strategiska positioner inom telekomindustrin under dessa två händelser. Slutsatser som dras är sedan styrkta av enkätresultat och statistik från marknadsundersökningar gjorda av den svenska post- och telestyrelsen. Marknadsfaktorer som är tillämpade på teknologi- och produktdisruptioner från tidigare teori appliceras på dessa affärsmodellshändelser. Faktorerna testas för att se i vilken utsträckning de kan föras över till teori för disruptiv innovation av affärsmodeller. Studien strävar också efter att hitta nya marknadsfaktorer som inte tidigare inkluderats i teorin. Denna artikel avslutas genom att presentera 10 omkringliggande faktorer som är viktiga för att utvärdera känsligheten för disruptiv affärsmodellsinnovation i en marknad. Artikeln utgår från 11 marknadsfaktorer, främst baserade på tidigare teorier om produkt- eller teknologidisruption. 7 av dessa faktorer kan överföras till affärsmodellsdisruption, vilket innebär att 4 faktorer avfärdas i sin helhet. Dessutom visade empirin att ytterligare 3 faktorer var viktiga för affärsmodellsdisruption. Studien fann att ”ändring av aktörer i värdekedjan” samt ”höga inträdesbarriärer” inte verkade vara så viktiga faktorer för affärmodellsdisruption. De marknadsfaktorer som var viktigast för marknadens känslighet för affärsmodellsdisruption var kopplade till kostnads- och slutkundsberoende, höga marginaler och skalbarhet. Det fanns dock flera faktorer som var viktiga för både affärsmodells- och teknologi/produktdisruption. Dessa marknadsfaktorer berörde marknadsfördelningen, den aktuella produkten, lönsamheten, och den aktuella värdekedjan. Skillnader mellan affärsmodellsdisruption och produkt- eller teknologidisruption utreds i denna studie. Skillnaderna visar sig vara viktiga när man undersöker marknadens känslighet för disruptiva innovationer. De stora skillnaderna som upptäcktes var att affärsmodeller är mer agila, är inte sedda som ett lika stort hot, och är mer ”pull”- än ”push”-baserade.

Steganography is a technique which hides secret information. In this work, we will hide a secret information in the packets which are produced during a Skype call. Skype is one of the best known and the most widely used VoIP applications. We will propose, describe and implement a steganography method by which we will send the secret message during the Skype call. For embedding the message into packets and extracting them, we will use steganographic method called matrix encoding. To avoid packet loss, we will increase the robustness of this method by error-correcting and self-synchronising codes. As error-correcting codes, we will use the binary Hamming (7, 4) -codes and for the self-synchronising, we will use T-codes. 1

In future telecommunication systems, we observe an increasing diversity of access networks. The separation of transport services and applications or services leads to multi-network services, i.e., a future service has to work transparently to the underlying network infrastructure. Multi-network services with edge-based intelligence, like P2P file sharing or the Skype VoIP service, impose new traffic control paradigms on the future Internet. Such services adapt the amount of consumed bandwidth to reach different goals. A selfish behavior tries to keep the QoE of a single user above a certain level. Skype, for instance, repeats voice samples depending on the perceived end-to-end loss. From the viewpoint of a single user, the replication of voice data overcomes the degradation caused by packet loss and enables to maintain a certain QoE. The cost for this achievement is a higher amount of consumed bandwidth. However, if the packet loss is caused by congestion in the network, this additionally required bandwidth even worsens the network situation. Altruistic behavior, on the other side, would reduce the bandwidth consumption in such a way that the pressure on the network is released and thus the overall network performance is improved. In this monograph, we analyzed the impact of the overlay, P2P, and QoE paradigms in future Internet applications and the interactions from the observing user behavior. The shift of intelligence toward the edge is accompanied by a change in the emerging user behavior and traffic profile, as well as a change from multi-service networks to multi-networks services. In addition, edge-based intelligence may lead to a higher dynamics in the network topology, since the applications are often controlled by an overlay network, which can rapidly change in size and structure as new nodes can leave or join the overlay network in an entirely distributed manner. As a result, we found that the performance evaluation of such services provides new challenges, since novel key performance factors have to be first identified, like pollution of P2P systems, and appropriate models of the emerging user behavior are required, e.g. taking into account user impatience. As common denominator of the presented studies in this work, we focus on a user-centric view when evaluating the performance of future Internet applications. For a subscriber of a certain application or service, the perceived quality expressed as QoE will be the major criterion of the user's satisfaction with the network and service providers. We selected three different case studies and characterized the application's performance from the end user's point of view. Those are (1) cooperation in mobile P2P file sharing networks, (2) modeling of online TV recording services, and (3) QoE of edge-based VoIP applications. The user-centric approach facilitates the development of new mechanisms to overcome problems arising from the changing user behavior. An example is the proposed CycPriM cooperation strategy, which copes with selfish user behavior in mobile P2P file sharing system. An adequate mechanism has also been shown to be efficient in a heterogeneous B3G network with mobile users conducting vertical handovers between different wireless access technologies. The consideration of the user behavior and the user perceived quality guides to an appropriate modeling of future Internet applications. In the case of the online TV recording service, this enables the comparison between different technical realizations of the system, e.g. using server clusters or P2P technology, to properly dimension the installed network elements and to assess the costs for service providers. Technologies like P2P help to overcome phenomena like flash crowds and improve scalability compared to server clusters, which may get overloaded in such situations. Nevertheless, P2P technology invokes additional challenges and different user behavior to that seen in traditional client/server systems. Beside the willingness to share files and the churn of users, peers may be malicious and offer fake contents to disturb the data dissemination. Finally, the understanding and the quantification of QoE with respect to QoS degradations permits designing sophisticated edge-based applications. To this end, we identified and formulated the IQX hypothesis as an exponential interdependency between QoE and QoS parameters, which we validated for different examples. The appropriate modeling of the emerging user behavior taking into account the user's perceived quality and its interactions with the overlay and P2P paradigm will finally help to design future Internet applications. / Applikationen im heutigen Internet werden immer mehr durch intelligente Endknoten bereitgestellt, deren Kommunikation in logischen, virtuellen Netzwerken, (Overlays) realisiert wird. Die verstärkte Diensterbringung durch solche Overlays, wie zum Beispiel bei Peer-to-Peer Dateitauschbörsen oder Telefonie über das Internet, wird durch einen Paradigmenwechsel von Multi-Service Networks zu Multi-Network Services beschrieben. Während in einem Multi-Service Network verschiedene Dienste innerhalb eines Netzes angeboten werden, beschreibt ein Multi-Network Service die Diensterbringung über verschiedene Netze und Netzzugangstechnologien, wie es im Internet der Fall ist. Dadurch kann die technische Güte des Telekommunikationsdienstes (Quality of Service, QoS) nicht mehr die alleinige Metrik für die Qualität eines Dienstes sein. Stattdessen ist die vom Nutzer erfahrene Dienstgüte (User Perceived Quality of Experience, QoE) zu betrachten. Diese QoE muss entsprechend modelliert werden, um die Performanz von heutigen oder auch zukünftigen Internetapplikationen zu beurteilen. Die Berücksichtigung der QoE beinhaltet unter anderem auch neuartige Verhaltensweisen der Teilnehmer, die ebenfalls modelliert werden müssen. Ein Beispiel ist der Dienstabbruch durch ungeduldige Nutzer beim Herunterladen von Filmen oder bei nicht ausreichender Qualität bei Internet-Telefonie. Durch die Verschiebung der Intelligenz von Applikationen in Richtung Endknoten entstehen neu aufkommende Verhaltensweisen der Teilnehmer und sich ändernde Charakteristika des Netzwerkverkehrs, die sie von klassischen Client-Server-Anwendungen unterscheiden. Beispiele hierfür sind egoistisches oder altruistisches Nutzerverhalten bei der Einbringung von Endnutzer-Ressourcen zur Diensterbringung oder auch bösartiges Nutzerverhalten bei der gezielten Störung eines Dienstes (Pollution). In beiden Fällen sind die zeitdynamischen Verhaltensmuster (Churn, Flash Crowds) zu berücksichtigen. Um die ausgedehnten Overlay. Netze zu planen und zu evaluieren, sind überdies auch neue Leistungsbewertungsmodelle notwendig, damit zum Beispiel die Simulation skaliert oder aber auch zeitdynamische Nutzerverhalten in analytischen Modellen abgebildet wird. Diese Doktorarbeit arbeitet diese Aspekte an drei Anwendungsbeispielen auf: Verteilernetz für Dateiinhalte (Content Distribution Network), Netzwerk-basierte Videorekorder (Online TV Recorder) und Sprachtelefonie über P2P (VoP2P). Die Ergebnisse und Untersuchungen dieser Arbeit gliedern sich entsprechend dieser Anwendungsbeispiele.

Cette thèse présente deux axes de recherche que j'ai menés entre 2004 et 2011. Le premier axe est sur la compréhension sur protocole BitTorrrent. Il recouvre des travaux expérimentaux et de mesures montrant l'efficacité de BitTorrent et expliquant les variations de performances observées dans la littérature et interprétées à tort comme un problème de BitTorrent. Une caractéristique de ces travaux est l'utilisation d'expérimentations à grande échelle (par exemple 10 000 pairs BitTorrent que l'on expérimente dans un environnement contrôlé) et de mesures à grande échelle (par exemple, 148 millions d'adresses IP mesurées sur 3 mois). Le deuxième axe est sur l'étude de la protection de la vie privée sur Internet. Ces travaux montrent que l'on peut surveiller sans infrastructure dédiée (c'est-à-dire d'une seule machine) la quasi-intégralité des utilisateurs de BitTorrent. On montre également qu'en exploitant les communications pair-à-pair dans Skype on peut lier une identité sociale (nom, prénom, adresse email, etc.) à une activité sur Internet (par exemple, une liste de contenus téléchargés avec BitTorrent). On peut également suivre la mobilité des utilisateurs de Skype et on montre que cette mobilité est réelle pour un utilisateur standard. Pour finir, on montre qu'un réseau garantissant l'anonymat, comme Tor, n'offre pas une protection satisfaisante.

Steganography is a technique which hides secret information. In this work, we will hide a secret information in the packets which are produced during a Skype call. Skype is one of the best known and the most widely used VoIP applications. We will propose, describe and implement a steganography method by which we will send the secret message during the Skype call. For embedding the message into packets and extracting them, we will use steganographic method called matrix encoding. To avoid packet loss, we will increase the robustness of this method by error-correcting and self-synchronising codes. As error-correcting codes, we will use the binary Hamming (7, 4) -codes and for the self-synchronising, we will use T-codes. 1

ABSTRAKTMilic Pavlovic, Ljiljana (2012). Skype i hem och skolmiljö. En fallstudie om Skypekommunikation mellan ett barn med Downs syndrom och hans familjemedlemmar. (Skype at home and in school environment. A case study of the communication between a child with Down syndrome and his family members); Skolutveckling och ledarskap; Specialpedagogik; Lärarutbildningen; Malmö HögskolaSyftet med studien är att beskriva, analysera och tolka kommunikation via Skype mellan en elev i träningsskola och hans familjemedlemmar när eleven använder både verbalt språk och tecken som stöd. Det sociokulturella perspektivet är den teoretiska ramen för studien. Eftersom studien handlar om en elev i en konstruerad social situation, videokommunikation via Skype, är fallstudien den motiverade forskningsansatsen. Videoobservation är den centrala metoden i studien eftersom videoobservation lämpar sig bäst för verbal, icke verbal samt alternativ och kompletterande kommunikation (AKK). Semistrukturerade intervjuer är använda som komplettering av videoobservation. Resultatet visar att videokommunikation via Skype har utvecklats till en ny kommunikativ form för eleven i studien. Videokommunikation via Skype har varit en process. Under processen har Eleven lärt sig att använda Skype program och att kommunicera via Skype. Det har skett i interaktion mellan engagerade samtalspartner och studiens deltagare som har stimulerat eleven med utgångspunkt i hans intresse och motivation. Nyckelord: Downs syndrom, funktionsnedsättning, iPad, Skype, specialpedagogik, videokommunikation, videoobservation, träningsskola / ABSTRACT Milic Pavlovic, Ljiljana (2012). Skype at home and in school environment. A case study of the communication between a child with Down syndrome and his family members; School Development and Leadership; Special needs education; Faculty of Education and Society; Malmö UniversityThe purpose of this study is to describe, analyze and interpret the communication via Skype between a student in the special school for pupils with severe learning difficulties and his family members using both spoken language and sign supported speech as complementary.The theoretical framework for the study is a socio-cultural perspective. The study discusses the student in a designed social situation, video communication via Skype. Thus the case study is the basis for the research effort. The main method for the study is video observation being well suited for verbal and nonverbal as well as augmentative and alternative communication (AAC). Semi-structural interviews are used as a complement.The results show that video-communication via Skype has developed into a new communicative form for the student. During the development process the student has learned to use the Skype software and how to communicate through Skype. Interaction between involved parties and the participants of the study had a stimulatory effect on the student appealing to his interests and motivation. Key Words: disabilities, Down syndrome, iPad, severe learning difficulties, Skype, special needs, special school, video communication, video observation