This thesis addresses the question of how a scalable, distributed teamwork environment should be designed and realized. Central design criteria includes that the system should be scalable and robust, allow for easy access and be symmetric. The system should allow for project team members to collaborate even though they are not located at the same physical location. The resulting system presented in this thesis, called the mStar environment have been created to address exactly these questions. mStar is scalable and robust through the usage of standard networks and IP-multicast, it allows for easy access as it is desktop based and finally it is symmetric allowing for easy peer-communication. mStar includes support for desktop conferencing, including mAudio for audio, reuse of the MBone Vic tool for video, mWB for whiteboard, mChat for text based chat and mVote for voting. It also supports distributed synchronized presentations using the WWW and the mWeb application. As all traffic is network and IP-multicast based it allows for easy recording and playback of teamwork sessions using the mMOD application. To allow for easy access to users behind non-multicast capable network segments (primarily modem and ISDN), mTunnel was created. It allows for tunneling and transformation of the traffic. Another member of the mStar environment is Director for remote control of video equipment. mStar also includes support for easy creation of new teamwork tools and applications using the Tunable Multicast Platform - /TMP and the Generic Agent Architecture. The mStar environment can be used and is being used on a daily basis for electronic meetings, distance education and lectures, and daily teamwork. The usage mStar creates group awareness between project members and helps users from not becoming isolated from their department and project team. mStar allows for usage 24 hours a day and have resulted in, among other things, a new usage patterns, which resembles electronic corridors more than specific meetings, where users can and do meet spontaneously to talk about anything they want, but also overhear other interesting and important conversations just as in a physical office corridor. / Godkänd; 1997; 20061004 (ysko)

Public use of the Internet increases as wideband connections become pervasive and applications suitable for media distribution grow popular. Group collaboration applications have attracted interest during recent years. Wireless connectivity and business applications also furthers a need for reliable communication protocols. Multicast is a driving force for new applications involving one-to-many as well as many-to-many user scenarios like lecturing, discussions, and collaborative work. In some applications guaranteed delivery of every packet is not crucial, while in other this is a requirement. Error handling in reliable protocols can present a substantial challenge already in a homogeneous environment. Including a plethora of end-user terminal types with widely varying resources it becomes even more challenging. Protocols and applications must therefore be able to handle receiver and network link heterogeneity. The thesis addresses some of the challenges facing the applications in this field, related to multicast and unicast alike. Although the obstacles each of them must overcome may differ, there are similarities with regards to possible solutions with respect to error handling or resource allocation. Error handling protocols are proactive or reactive. Proactive protocols transmit redundant information along with the original information, enabling the receivers to repair lost packets without feedback to the sender. Reactive protocols rely either on positive or negative feedback from the receivers in order to establish reliability. According to a definition of semantic reliability the reliability concept can be interpreted in terms of application semantics. It is proposed to view reliable multicast as a special case of semantically reliable multicast and to implement a dynamically configurable transport layer with an error-handling rule set that can be configured from the application or even from the sender in- session. It is also proposed to make use of the application's knowledge of specific semantics to improve on the recovery of lost packets, congestion handling, or resource allocation. The thesis also presents a bandwidth-sharing scheme for video in group collaboration using application semantics in the form of user hints. The presence of such events is made available to all senders via message passing between session members. As information relating to a user's interest in another user is conveyed, the sender may increase its use of resources on the expense of other senders. A scheme is proposed and a prototype implementation and experimental results are presented. / <p>Godkänd; 2003; 20060918 (ysko)</p>

This thesis presents a system for real-time large scale distributed music distribution, such as radio on the Internet. The existing technologies do not enable the full potential that broadcast media on the Internet can give, such as a very large number of interactive receivers. A technology that can help achieve potential is IP-multicast, which enables broadcast applications to scale to millions of receivers. However, IP-multicast creates new problems that have to be solved for it to be used on the Internet; some of these problems are addressed in this thesis. The system presented in this thesis, mIR - multicast Interactive Radio, has been used as a prototype to implement and examine different solutions to some of the issues of IP-multicast and real time music distribution. These are problems such as heterogeneity, reliability and security. Heterogeneity and reliability are different aspects of the same problem: that IP-multicast is an unreliable Internet transport mechanism. In this thesis different methods for avoiding these problems are described and evaluated. Security in the context of IP-multicast has many aspects. While the problems of confidentiality and authentication have been extensively examined, there are still a few unresolved problems. One of these problems is traitor tracing: how to know the origin of illegal copies of a media object such as a radio transmission. An application of digital watermarking, fingerprinting, can be used to distinguish between different copies of the same media object, but requires that each copy is individually marked. This contradicts the basic property of multicast that ensures its scalability: that everyone receives exactly the same data. We show how we can combine the different goals of fingerprinting and IP-multicast while still maintaining the scalability features of multicast. / <p>Godkänd; 2001; 20070313 (ysko)</p>

This work is inspired by the autonomic networking paradigm. It investigates the issue of making network resource management mechanisms in the access part of wireless networks self-aware and self-configuring. Open access networks (OAN) have private WLAN cells made available for public use and enable bypassing mobile users to profit from continuous coverage, allowing private and public subscribers to share a common infrastructure. Resources are network parameters, e.g. bandwidth, capacity, that have to be fairly and accurately allocated, distributed, and managed in order to optimize performance and ensure proper and fair operation. Analyzing and exploring existing multimedia session and resource management mechanisms on the wireless part is a crucial step for determining their limitations and shortcomings. A new way of making OANs self-aware is proposed and a self-configuring mechanism which has a competitive advantage in the qualitative sense over already existing mechanisms is designed and developed. The amount of network resources as well as the timing and form of their availability are decisive for enabling service functionality and providing a sufficient quality of service level. Our area of discourse is the "last- mile" part of an 802.11 network; i.e. the part between the access point and the mobile node. In OANs, maintaining and updating rates for different flows used by a single terminal traversing many adjacent APs is a challenge in itself. It is solved by using several key design factors. Monitoring the environment locally and updating the designed information structures leads to network self-awareness. Next, a high-level mechanism that aggregates information from several protocols including CARD (Candidate Access Router Discovery), MIP (Mobile IP), and SIP (Session Initiation Protocol) is defined. It specifies the interactions between the mobile terminal and the access point controller. Then capacity maintenance and rate allocation issues at the two end-points of the last-mile are analyzed. The overhead in OANs required for the launching or reconfiguration of a real-time session can be significantly reduced by a proposed algorithm which performs parameter injection into a multimedia data stream instead of following the classical negotiation path. A solution to change the session characteristics of an application that adapts to varying network conditions was developed, including a QoS solution with SIP and MIP to optimize the session characteristics by taking into account the changed conditions in the network. With this approach, reduced session signaling delay and low jitter values are achieved as implementation results show. The thesis is concluded by considering the general issues: self-aware node architectures, self-configuring resource management. / <p>Godkänd; 2008; 20081112 (ysko)</p>

This thesis proposes and evaluates architectures and algorithms for access network selection in heterogeneous networking environments. The ultimate goal is to select the best access network at any time taking a number of constraints into account including user requirements and network characteristics. The proposed architecture enables global roaming between access networks within an operator's domain, as well as across operators without any changes in the data and control plane of the access networks being required. Also, the proposed architecture includes an algorithm for measuring performance of access networks that can be used on a number of access technologies being wired or wireless. The proposed access network selection algorithm also has an end-to-end perspective giving a network performance indication of user traffic being communicated. The contributions of this thesis include an implementation of a simulation model in OPNET Modeler, a proposal of a metric at the network layer for heterogeneous access networks, an implementation of a real-world prototype, a study of multimedia applications on perceived quality of service, an access network selection algorithm for highly mobile users and vehicular networks, and an extension of the mentioned access network selection algorithm to support cross-layer decision making taking application layer and datalink layer metrics into account. / Godkänd; 2008; 20080910 (ysko)

This licentiate thesis focuses on how to design a robust and flexible environment for net-based learning. The environment is required to be scalable for large groups, robust over lossy networks, flexible to meet different learning scenarios, and support interactivity. The mStar environment presented in this thesis has been developed to meet these requirements. The environment is scalable through the use of IP multicast and a server-less design. Robustness is achieved by separating traffic by loss tolerance, where traffic that accept no loss uses a reliable multicast protocol and traffic that can accept some loss uses repair techniques. To enhance robustness even further, network resource management is suggested. Everything from small group meetings to large lectures is supported, which together with the possibility to use the tools asynchronously gives the flexibility needed. The tools in the environment are fully symmetric, which allows everyone equal access and thus supports full interactivity. Students using the mStar environment is no longer bound by physical distance, since they can easily take part of lectures, seminars and group discussions electronically. They can also be connected via not multicast enabled low bandwidth networks, since they can tunnel concentrated traffic to thir local hosts. The students are also less bound by time, as they can use the mMOD system to access recorded sessions or the WWW to access course information. / Godkänd; 1999; 20070403 (ysko)

How would you react if you looked down on your hands and they had been replaced with someone else’s hands? This is the case for virtual reality applications that incorporate virtual hands, all applications have their own representation of virtual hands but none takes the user’s own hand into account. For this reason, we have created a framework that allows to customize geometric features of existing hand models towards a more personal hand representation. We have designed and conducted an experiment to study sense of ownership of four virtual hand representations. It was found that participants pay attention to size of the hand and the length of the fingers but do not necessarily consider the virtual hands as their own. We believe that a virtual hand that truly creates the impression of one’s own hand may benefit educational, training or rehabilitation virtual reality applications. In order to achieve this, our conclusion is that a certain extent of size, shape and appearance of the user’s hand need to be considered.

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Denna rapport presenterar en jämförelse av beteende kring säkerhetskopiering av personlig data mellan millenniegenerationen och äldre generationer. Studien har en kvantitativ ansats som använde sig av online-enkäter för datainsamling. Studien jämförde vilka attityder och tidigare erfarenheter som påverkar beslutet om att säkerhetskopiera. The Protection Motivation Theory (PMT), korrelationer, hypotesprövning och signifikansanalys har använts för att analysera insamlad data. Resultatet visar att det finns skillnader mellan generationerna i beteende omkring säkerhetskopiering. / A generational issue: Behavior and attitudes regarding personal data backup. This report presents a comparison of the attitudes and behaviour towards backup of private data existing between millennials and the older generations. This is a quantitative study which used online surveys to gather data from the two different groups. The study aims to establish if there is any difference between the groups when it comes to the actual action of backing up private data. Further on it compares what attitudes and earlier experiences affects the decision to backup. The conclusion will be based on the analysis of the gathered data. The Protection Motivation Theory (PMT) will also be used to analyse parts of the data. The results show that there are differences between generations in the behavior regarding whether they perform backups.

Animerad film blir alltmer populär och i takt med detta ökar kraven hos tittarna på verklighetstrogna och relaterbara animerade karaktärer. En stor del av det som gör en animerad karaktär relaterbar är dess ansiktsuttryck och förmåga att uttrycka igenkänningsbara känslor. Därför behandlar denna rapport en studie som undersöker hur väl emotionella ansiktsuttryck i en traditionellt animerad Disney-film uppfattas av åskådare. Studien tar stöd i ett antal teoretiska källor som behandlar ämnen såsom överdrift i animering, digitalisering av tecknande samt emotionell uttrycksfullhet. För att genomföra undersökningen användes en kvantitativ enkät och en kompletterande ingående intervju som datainsamlingsmetoder. Studiens resultat var att hälften av enkätrespondenternas svar, samt två av tio av intervjurespondentens svar, stämde överens med de svar som författaren bestämt var korrekta utifrån filmens kontext. Slutsatsen var därmed att den emotionella uttrycksfullheten inte förmedlas bra, men även att en annan sorts studie krävs för att göra en mer rättvis bedömning av frågan.