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  • 51. Fiedler, Markus
    PERIMETER: Privacy-preserving contract-less, user-centric, seamless roaming for Always Best Connected Future Internet2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    PERIMETER is a new EU FP7 project, whose main objective is to establish a new paradigm of user-centricity for advanced networking. In contrast to network-centric approaches, user-centric strategies could achieve true seamless mobility. Putting the user at the centre rather than the operator enables the user to control his or her identity, preferences and credentials, and so seamless mobility is streamlined, enabling mobile users to be “Always Best Connected” in multiple-access multiple-operator networks of the Future Internet. For this purpose, PERIMETER will develop and implement protocols designed to cope with increased scale, complexity, mobility and requirements for privacy, security, resilience and transparency of the Future Internet. These include appropriate mechanisms for network selection based on Quality of Experience; innovative implementation of “Distributed A3M” protocols for Fast Authentication, Authorisation and Accounting based on privacy-preserving digital identity models. All these mechanisms will be designed to be independent from the underlying networking technology and service provider, so that fast, inter-technology handovers will be possible.

  • 52. Fiedler, Markus
    Quality feedback flows in future networks2009Inngår i: Elektrotechnik & Informationstechnik, ISSN 0932-383X, Vol. 126, nr 7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current rise in community-based content sharing and growing popularity of personalised multimedia transmission is accompanied by user-side quality demands. Internet, on the other hand, still provides merely best-effort service and thus only implicit feedback on critical network conditions through packet loss and delays. In order to satisfy future quality demands, feedback on quality problems needs to become much more explicit than what is the case today. In order to highlight the potential for improvement, this paper first identifies and analyses today’s feedback flows between users, applications, networks and the corresponding service providers. Based on this inventory, a new kind of feedback system employing self-organising overlay technology is introduced and exemplified. This future-proof system, developed within the European series of Networks of Excellence EuroNGI, EuroFGI and EuroNF, provides added feedback value to the above-mentioned stakeholders and furthermore a smooth transition path from current legacy towards future service management solutions.

  • 53. Fiedler, Markus
    Traffic Measurement and Characterization2004Inngår i: COST 279 - Midterm Report: Analysis and Design of Advanced Multiservice Networks Supporting Mobility, Multimedia, and Internetworking / [ed] Committee, COST 279 Management; Menth, M., Roma: ARACNE editrice S.r.l. , 2004, s. 49-73Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    We observe currently a fast evolution of web, multimedia, and especially peer-to-peer applications. This evolution yields a rapidly changing load environment for the transport of data streams subject to severe Quality of Service (QoS) constraints. Considering the needs for traffic planning and QoS assessment in wired and wireless access, as well as backbone networks, issues like load modeling and traffic characterization by thorough statistical techniques have to be addressed as the first basic steps of teletraffic engineering. For this purpose, new and reliable traffic measurement, modeling, and estimation techniques are required to accurately determine the traffic load and the resource usage in wired and wireless networks. The goal of this chapter consists in providing a comprehensive overview on related activities within the COST 279 action. Its structure reflects natural steps of obtaining results: traffic measurement, which concerns rather technical issues related to the collection of traffic and its statistics; traffic characterization, to provide a rather qualitative desciption of traffic behavior; traffic modeling, to provide a rather quantitative description with focus on models and their parameters; and traffic estimation, which is about inference and prediction of traffic volumes based on observations.

  • 54. Fiedler, Markus
    Traffic Measurement, Characterization and Modeling2005Inngår i: Analysis and Design of Advanced Multiservice Networks Supporting Mobility, Multimedia, and Internetworking. COST Action 279 Final Report / [ed] Brazio, J.; Tran-Gia, P.; Akar, N.; Beben, A.; Burakowski, W.; Fiedler, Markus; Karasan, E.; Menth, M.; Olivier, P.; Tutschku, K., Springer , 2005, s. 97-125Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    N/A

  • 55. Fiedler, Markus
    et al.
    Addie, Ron G.
    Verification and application of a second-order scale symmetry for queueing systems1999Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a simple second order scale symmetry is descibed. Because of the application of the central limit theorem to network traffic, which applies whenever the variance of the traffic from individual sources is finite, this scale symmetry is valid asymptotically for a large number of sources independently of the buffer size, the queueing performance parameter under consideration and the source model. Numerical results for on-/off sources show that it gives clear guidance for how system resources must grow in order to cope with increasing traffic, while maintaining or slightly improving queueing performance. Thus, it may be used for dimensioning purposes beyond the reach of sophisticated algorithms. Parallels to equivalent bandwidth approaches are drawn.

  • 56. Fiedler, Markus
    et al.
    Angelin, Lars
    Mobile services: students as need-finders2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a way of identifying new and useful mobile services by letting students act as need-finders and developers of services based on their own needs and ideas. It describes the background and outcomes of a course in mobile services given at Blekinge Institute of Technology (BTH) in spring 2002.

  • 57. Fiedler, Markus
    et al.
    Arlos, Patrik
    Gonsalves, Timothy A.
    Bhardwaj, Anuraag
    Nottehed, Hans
    Time is perception is money: web response times in mobile networks with application to Quality of Experience2011Inngår i: Lecture Notes in Computer Science, Springer , 2011, Vol. 6821, s. 179-190Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The number of mobile operators providing Internet access to end users is growing. However, irrespective of the access network, we observe a distinct sensitivity of user perception to response and download times, in particular for interactive services on the web. In order to facilitate the choice of the right network for a given task, this paper presents a systematic study of web download time and corresponding throughput as a function of the file size. Based on measurement data from three Swedish mobile operators and a particular strategy of choosing file sizes, we find surprisingly simple, yet sufficiently accurate approximations of download times. These approximations are based on simple-to-measure parameters and provide valuable quantitative insights into the acceleration of HTTP/TCP/IP-based data delivery. The paper discusses the emergence of these approximations and related errors. Furthermore, it correlates the findings with Quality of Experience, thus building bridges between performance, user perception and provisioning issues.

  • 58. Fiedler, Markus
    et al.
    Arvidsson, Åke
    A Resource Allocation Law to Satisfy QoS Demands on ATM Burst and Connection Level1999Annet (Annet vitenskapelig)
    Abstract [en]

    In this paper, we show the validity of a quite simple resource allocation law, which is not restricted to one time scale. Besides the fact that this law describes the basic behaviour of resource allocation for sources with variable bit rates, it offers savings of time and memory in practice when systems are to be dimensioned and routing has to be performed, and particularly in dynamic resource allocation with real-time requirements. The law is given as a function of traffc demand and consists of a constant, a linear and a power term. Its coeffcients are in influenced by traffic and system characteristics as well as by QoS requirements and may be determined by a Genetic Algorithm. Many examples show the universal character of this law for sources with variable bit rates.

  • 59. Fiedler, Markus
    et al.
    Arvidsson, Åke
    Required capacity for ATM Virtual Paths for QoS on cell and connection level1999Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We show approximation formulae for required capacities (bit rates) of ATM Virtual Paths that cover allocation on cell and connection level at the same time. Such formulae are valuable for dimensioning and routing purposes, as they allow for fast and precise calculations of required capacities and show the kind of dependency on the traffic demand for given traffic characteristics and Qulity of Service requirements. We discuss how to determine the coefficients of the approximation and its precision for connections with on-/off characteristics (voice, data). Finally, we show the gain that might be obtained if statistical multiplexing of variable bit rate connections is taken into account at the cell level.

  • 60. Fiedler, Markus
    et al.
    Blouin, Francois
    Arlos, Patrik
    18th ITC Specialist Seminar on Quality of Experience2008Rapport (Annet vitenskapelig)
    Abstract [en]

    The notion and topic of Quality of Experience (QoE) keeps attracting the attention of manufacturers, operators and researchers. It links user perception and expectations on one side and technical Quality of Service (QoS) parameters, management, pricing schemes etc. on the other side. Such links are needed in order to balance user satisfaction and economic aspects of service provisioning. However, the notion of QoE as such is not without controversy. Technicians, used to a world of objective and clearly definable parameters, tend to fear the subjective, somehow fuzzy parts associated with end user perception. Vice versa, customer relationship and marketing departments might find themselves uncomfortable with technical parameters which might not reflect the user perception in some tense situations. Nevertheless, appearance and utility of a networked service depend on the underlying technical solutions and their performance. Thus, we face the challenge of bringing it all together, which essentially describes the spirit of the 18th ITC Specialists Seminar on Quality of Experience (ITC-SS 18). ITC Specialist Seminars have a very good reputation in gathering experts and their high-quality contributions around a performance-oriented topic of mutual interest. ITC-SS 18 is intended as a meeting place between experts, researchers, practitioners, vendors and customers. It is devoted to presentations and discussions of QoE concepts, analysis, management approaches etc., both from industry and academia. While many conferences are dominated by academia, one third of the submissions to ITC-SS 18 originated from industry. The contributions have been peer-reviewed by at least three independent reviewers and finally, we selected 18 papers to be presented. Additionally, two keynote speeches reflect one industrial and one academic approach to QoE analysis and implementation. For the ITC, the leading conference for performance modeling and analysis of communication networks & systems, ITC-SS 18 opens a window towards the end user. ITC-SS 18 takes place in Karlskrona on May 29—30, 2008. It is organized by the Dept. of Telecommunication Systems (ATS) within the School of Engineering (TEK) at Blekinge Institute of Technology (BTH) in cooperation with the International Advisory Council (IAC) of ITC.

  • 61. Fiedler, Markus
    et al.
    Carlsson, Patrik
    Nilsson, Arne A.
    Voice and Multi-fractal Data in the Internet2001Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the Internet era there is a need to understand how traditional Public Switched Telephone Network (PSTN) services and the new Internet services can coexist. The best-effort based IP network will have to maintain the level of service that customers from the PSTN world expect. This study contributes to the traffic engineering of such a system by presenting an analytical model for integrating Voice over IP (VoIP) traffic with multi-fractal data traffic. This model is based on the stochastic fluid flow model. Effects on delay and loss performance of adding VoIP traffic to a data link as well as capacity requirements to maintain a certain quality of service are discussed

  • 62.
    Fiedler, Markus
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Chapala, Usha Kiran
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Peteti, Sridhar
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Modeling instantaneous quality of experience using machine learning of model trees2019Inngår i: 2019 11th International Conference on Quality of Multimedia Experience, QoMEX 2019, Institute of Electrical and Electronics Engineers Inc. , 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For service providers and operators, successful root cause analysis is essential for satisfactory service provisioning. However, reasons for sudden trend changes of the instantaneous Quality of Experience (QoE) may not always be immediately visible from underlying service- or network-level monitoring data. Thus, there is the challenge to pinpoint such moments of change in provisioning, and model the impact on instantaneous QoE, as a lead in root cause analysis. This work investigates the potential of Machine Learning (ML) of deriving time-interval-based models for instantaneous QoE ratings, obtained from a set of publicly available rating traces. In particular, the paper demonstrates the capability of the ML algorithm M5P to model trends of instantaneous QoE through model trees, consisting of piecewise linear functions over time. It is shown how and to which extent these functions can be used to estimate moments of change. Furthermore, the model trees support earlier assumptions about exponential shapes of instantaneous QoE over time as reactions to sudden changes of provisioning, such as video freezes. © 2019 IEEE.

  • 63. Fiedler, Markus
    et al.
    Chevul, Stefan
    Isaksson, Lennart
    Lindberg, Peter
    Karlsson, Johan
    Communication requirements of generic services for Intelligent Transport Systems2004Annet (Annet vitenskapelig)
    Abstract [en]

    In order to meet their users’ expectations and to be of efficient help for people using or maintaining Intelligent Transport Systems (ITS), related services need efficient support from the underlying communication systems, which in turn requires profound knowledge of those needs. This paper presents an approach to gather services into generic groups and a framework to classify their needs in terms of availability, performance, security and cost in a generic manner. These needs are consequently seen from the user’s perspective, but formulated in a way such that the matching towards technical parameters as e.g. throughput offered by a communication network can be performed. Upon comparing needs with offers, the feasibility of a certain communication technology for a certain type of service can be determined, which in turn helps to choose the right kind of connectivity in order to yield the desired degree of availability, performance, security and cost. This work is carried out within the VINNOVA-sponsored project PIITSA (Personal Information for Intelligent Transport Systems through Seamless communications and Autonomous decisions) conducted by Aerotech Telub, Blekinge Tekniska Högskola, Statens Provningsanstalt Borås and Vägverket, respectively.

  • 64. Fiedler, Markus
    et al.
    Chevul, Stefan
    Isaksson, Lennart
    Lindberg, Peter
    Karlsson, Johan
    Generic communication requirements of its-related mobile services as basis for seamless communications.2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to meet user expectations and to be of efficient help for people using or implementing Intelligent Transport Systems and Services (ITS), mobile ITS-related services need efficient support from the underlying communication systems, which in turn requires profound knowledge of those needs. As a first step towards an optimal automatic choice of communication technologies in order to provide for seamless communications, this paper groups services into generic groups and presents a framework to classify their needs in terms of availability, performance, security and cost in a generic manner. These needs are consequently seen from the user’s perspective, but formulated in a way such that they can be matched towards known network parameters. Upon comparing needs with offers, the feasibility of a certain communication technology for a certain type of service can be determined both proactively and reactively, which helps to automatically select the right kind of connectivity in order to yield the desired degree of availability, performance, security and cost. We motivate for instance the need for determining and monitoring applicationperceived speeds, a multi-level security models and the one-stop service concept. We also provide an example on how these needs can be matched to offers by different networks.

  • 65. Fiedler, Markus
    et al.
    Chevul, Stefan
    Isaksson, Lennart
    Tutschku, Kurt
    Binzenhöfer, Andreas
    The Throughput Utility Function: Assessing network impact on mobile services2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Based on the need for distributed end-to-end quality management for next-generation mobile Internet services, this paper presents a ready-to-deploy quality assessment concept for the impact of the network on the performance of mobile services. We consider the throughput utility function (TUF) as a special case of the network utility function (NUF). These functions combine the observed network utility at the inlet and the outlet of a mobile network. NUF and TUF capture the damping effect of the network onto user-perceived quality from an end-to-end perspective. As opposed to sometimes hard-to-evaluate QoS parameters such as delay and loss, the NUF is highly intuitive due to its mapping to a simple value between 0 and 100 %, which reflects user perception. We demonstrate the capabilities of the proposed TUF by measurements of application-perceived throughput conducted in a mobile, i.e. GPRS and UMTS network.

  • 66. Fiedler, Markus
    et al.
    Chevul, Stefan
    Radtke, Olaf
    Tutschku, Kurt
    Binzenhöfer, Andreas
    The Network Utility Function: A practicable concept for assessing network impact on distributed services2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Based on the need for distributed end-to-end quality management for next generation Internet services, this paper presents a ready-to-deploy quality assessment concept for the impact of the network on the service performance. The proposed Network Utility Function (NUF) combines the observed network utility at the inlet and the outlet. Thus, it captures the damping effect of the network onto user-perceived quality from an end-to-end perspective. As opposed to incomprehensible QoS parameters such as delay and loss, the NUF is highly intuitive due to its mapping to a simple value between 0 and 1. We demonstrate the capabilities of the proposed concept for a special NUF, the Throughput Utility Function (TUF) by realistic simulation.

  • 67.
    Fiedler, Markus
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    De Moor, Katrien
    Norwegian University of Science and Technology, NOR.
    Ravuri, Hemanth
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Tanneedi, Prithvi
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Chandiri, Mounika
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Users On The Move: On Relationships Between QoE Ratings, Data Volumes and Intentions to Churn2017Inngår i: Proc. 2017 IEEE 42nd Conference on Local Computer Networks Workshops (LCN Workshops): Workshop On User MObility and VEhicular Networks (ON-MOVE), IEEE, 2017, s. 97-102Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For a long time, the risk of customer churn, i.e. to leave an operator, has been used as argument in favor of Quality of Experience (QoE) research. However, the understanding of how churn behavior and QoE are related is still limited. This is problematic, as customer retention and churn prediction have grown in importance in face of ever-growing competition on the telecom market. The work presented in this paper aims to make a contribution in this respect, by exploring the relationships between QoE ratings, data volumes and churn risk through a longitudinal user study. Using an Experience Sampling Method-inspired approach we have been collecting weekly feedback on experienced quality, annoyance and intentions to churn from 22 users for up to eight weeks. Additionally, measurements of weekly used data volumes were collected. We observed churning behavior for 3 out of 22 participants and analyze the rating and data usage profiles of churners against non-churners. Furthermore, we investigate correlations of ratings and volumes, and find that “annoyed churners surf less”. Our findings point out warning signals for potential user churn as well as promising directions for future studies.

  • 68. Fiedler, Markus
    et al.
    Ekelin, Annelie
    Dittrich, Yvonne
    Eriksén, Sara
    E-government as co-construction: Networks, accountability, and working relations of technology production and use2003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The project within which this paper was co-authored focuses on the domain of e-government and is a deliberate attempt by the involved partners to cultivate and expand local and regional spaces for situated innovation, design and development of public services and ICT use in the public sector. Our starting point is e-government understood as co-construction. The project is currently being funded by the Innovative Actions within ERDF, the European Regional Development unding. The partners of the e-overnment arena are public service providers, ICT providers and researchers from a number of different disciplines. In this paper, we focus on communication networks and accountability. Are communication networks enablers or disablers for e-government services, and how can they be held accountable to their users? To what extent might we need to help each other unpack ‘black boxes’ and exchange them for ‘glass boxes’ in communicating with users and across disciplinary boundaries? Using metaphors and models from telecommunications, software engineering, informatics, business administration and human work science, and inspired by the Scandinavian tradition of Participatory Design, we attempt to establish a common basis to explore the evolving technologies and practices in e-government.

  • 69. Fiedler, Markus
    et al.
    Eliasson, Charlott
    Ciszkowski, Tomasz
    Mazurczyk, Wojciech
    Kotulski, Zbigniew
    Parameterisation of a reputation system for VoIP in P2P networks for improved communication quality and security2008Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper, we propose how to parameterize and maintain a reputation system that, based on the current network conditions, supports the selection of the optimal end-to-end communication path for VoIP communication in a P2P context. Each node’s reputation is formed based on three factors: (1) performance reputation (own experience from passive measures of the network conditions); (2) security reputation; and (3) information reputation consisting of recommendations from other nodes. Reputation data is periodically updated from continuous monitoring of path quality and security and also from information exchange between the nodes. When network conditions deteriorate, the reputation system enables switching, if possible, to another available path for furthercommunication. The proposed reputation system is a component of the SecMon system, which is intended especially for VoIP service over P2P networks. SecMon features lightweight QoS parameter monitoring, authentication and data integrity services. The exchange of monitoring information represents a low-bandwidth consumption solution that is transparent to the users and possesses a self-organizing capability. The above-mentioned exchange features are accomplished by utilizing two information hiding techniques: digital audio watermarking and network steganography. These techniques are used to create covert channels that serve as transport channels for lightweight QoS measurement results. Moreover, in this paper, we present results of the simulations that were performed to investigate how the proposed reputation system is performing for a simple twopath case scenario. Additionally, we show how different network conditions like delays and packet losses affect the proposed reputation system and how they are modeled with utility functions. Results of the simulations also illustrate the approaches to thresholds that trigger path changes.

  • 70.
    Fiedler, Markus
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Hackbarth, Klaus
    Hlavacs, Helmut
    Socio-economic issues in Future Generation Internet2008Inngår i: Journal of universal computer science (Online), ISSN 0948-695X, E-ISSN 0948-6968, Vol. 14, nr 5, s. 612-614Artikkel i tidsskrift (Fagfellevurdert)
  • 71. Fiedler, Markus
    et al.
    Hasslinger, Gerhard
    Waiting Time Quantiles for the Gaussian Voice Traffic Model2002Annet (Annet vitenskapelig)
    Abstract [en]

    Traffic models with a rate varying according to a Gaussian distribution are commonly used to evaluate statistical multiplexing in telecommunication systems. The superposition of a large number of homogeneous Markovian On-Off sources asymptotically approaches an Ornstein-Uhlenbeck process (OUP) which represents a Gaussian process with exponential autocorrelation function. The workload analysis for a multiplexer with OUP input leads to a simple and clearly structured dependence of waiting time quantiles on system and quality of service parameters. Semi-Markovian fitting procedures as well as the fluid flow method provide independent analysis ap-proaches at an assured accuracy level. The comparison of the corresponding waiting time quantiles shows the suitability of assuming traffic to be Gaussian already for a moderate number of traffic sources.

  • 72. Fiedler, Markus
    et al.
    Hlavacs, Helmut
    Hackbarth, Klaus
    Arlos, Patrik
    Quality of experience. 1- Metrics and performance evaluation2010Inngår i: Annales des télécommunications, ISSN 0003-4347, E-ISSN 1958-9395, Vol. 65, nr 1-2, s. 1-2Artikkel i tidsskrift (Fagfellevurdert)
  • 73. Fiedler, Markus
    et al.
    Hlavacs, Helmut
    Hackbarth, Klaus
    Arlos, Patrik
    Quality of experience 2: Socio-economic aspects2010Inngår i: Annales des télécommunications, ISSN 0003-4347, E-ISSN 1958-9395, Vol. 65, nr 3-4, s. 1-2Artikkel i tidsskrift (Fagfellevurdert)
  • 74. Fiedler, Markus
    et al.
    Hossfeld, Tobias
    Quality of Experience-related differential equations and provisioning-delivery hysteresis2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Churn of revenue-generating and dissatisfied users has become a major point of concern for service providers and network operators. As services rely on interconnecting networks, service performance and thus user satisfaction depend on network performance. Consequently, it is of utmost importance to understand the relationships between user perception, captured by quantitative Quality of Experience (QoE) parameters, and network performance, described by Quality of Service (QoS) parameters. This paper provides insights into fundamental relationships between QoE and QoS, formulated as partial differential equations describing changes in QoE with respect to specific QoS parameters. A set of illustrating examples from the literature is given. Furthermore, the different impacts of provisioning and degree of success or failure of delivery on QoE are discussed, leading to the QoE provisioning-delivery hysteresis. This hysteresis provides a striking motivation for employing elastic adaptation mechanisms to available resources instead of suffering from uncontrolled data loss.

  • 75. Fiedler, Markus
    et al.
    Hossfeld, Tobias
    Norros, Ilkka
    Rodrigues, Joel
    Pereira, Paulo Rogério
    The Network of Excellence Euro-NF and its Specific Joint Research Projects2011Inngår i: ICaST: ICST's Global Community Magazine (online)Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents the European FP7 Network of Excellence “Euro- NF” (Networks of the Future) and reviews its set of activities. Specific attention is paid to the concept of Specific Joint Research Projects (SJRP), a series of small but focused projects, integrating at least three Euro-NF partners and targeting joint seminal work, publications as well as full-size follow-up projects. Further to the description of the SJRP concept, a set of three selected SJRP from different areas are presented in detail with respect to motivation, goal, contents, results, and impact.

  • 76. Fiedler, Markus
    et al.
    Hossfeld, Tobias
    Tran-Gia, Phuoc
    A generic quantitative relationship between Quality of Experience and Quality of Service2010Inngår i: IEEE Network, ISSN 0890-8044, E-ISSN 1558-156X, Vol. 24, nr 2, s. 36-41Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quality of Experience (QoE) ties together user perception, experience and expectations to application and network performance, typically expressed by Quality of Service (QoS) parameters. Quantitative relationships between QoE and QoS are required in order to be able to build effective QoE control mechanisms onto measurable QoS parameters. On this background, this paper proposes a generic formula in which QoE and QoS parameters are connected through an exponential relationship, called IQX hypothesis. The formula relates changes of QoE with respect to QoS to the current level of QoE, is simple to match, and its limit behaviours are straighforward to interpret. It validates the IQX hypothesis for streaming services, where QoE in terms of Mean Opinion Scores (MOS) is expressed as functions of loss and reordering ratio, the latter of which is caused by jitter. For web surfing as the second application area, matchings provided by the IQX hypothesis are shown to outperform previously published logarithmic functions. We conclude that the IQX hypothesis is a strong candidate to be taken into account when deriving relationships between QoE and QoS parameters.

  • 77. Fiedler, Markus
    et al.
    Isaksson, Lennart
    Chevul, Stefan
    Measurements and analysis of application-perceived throughput via mobile links2011Inngår i: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 5233, s. 37-69Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Application-perceived throughput plays a major role for the performance of networked applications and user experience and thus, for network selection decisions. To support the latter, this tutorial paper investigates the process of user-perceived throughput in GPRS and UMTS systems seen over rather small averaging intervals, based on test traffic mimicking the needs of streaming applications, and analyzes the results with aid of summary statistics. These results reveal a clear influence of the network, seen from variations and autocorrelation of application-perceived throughput mostly on the one-second time scale and indicate that applications have to cope with significant jitter when trying to exploit the nominal throughputs. In GPRS, the promised average throughputs are not reached in downlink direction; instead, significant packet loss occurs. Furthermore, with aid of causality arguments for an equivalent bottleneck, bounds for the extra delay of the first packet sent via mobile links is derived from throughput measurements.

  • 78. Fiedler, Markus
    et al.
    Isaksson, Lennart
    Chevul, Stefan
    Karlsson, Johan
    Lindberg, Peter
    Measurements and analysis of application-perceived throughput via mobile links2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Application-perceived throughput plays a major role for the performance of networked applications and thus for user experience. Especially in mobile environments, throughput is limited, which is a challenge for applications and users. On this background, this tutorial paper investigates the process of user-perceived throughput in GPRS and UMTS systems seen over rather small averaging intervals. It discusses the corresponding active measurements mimicking the needs of streaming applications and analyzes results with aid of summary statistics, histograms and autocorrelation coefficients. These results reveal a clear influence of the network, seen from variations and autocorrelation of application-perceived throughput mostly on the one-second time scale. Such an influence has to be considered when choosing the right kind of network for a specific task. To that aim, the investigated metrics will serve as input to a multi-criteria decision process to determine the proper network for a specific service. The results indicate that, applications have to cope with considerably large jitter when trying to use the nominal throughputs. In GPRS, the promised average throughputs are not even reached in downlink direction; instead, a quite large amount of packet loss occurs. With aid of causality arguments for an equivalent bottleneck, bounds for the extra delay of the first packet sent via mobile links can in fact be derived from throughput measurements.

  • 79. Fiedler, Markus
    et al.
    Krieger, Udo R.
    The impact of varying channel capacity on the quality of advanced data services in PCS networks2000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We develop a unifying framework to perform the end-to-end quality of service (QoS) management of advanced data services in PCS networks. For this purpose, we first describe a generic fluid-flow model with Markov-modulated input flows and variable service rates depending on a Markovian environment for the wireless part of the transport path. Then we indicate how it can be used to evaluate the QoS of the data transport and to what extent the varying capacity of the transport channel influences the latter.

  • 80.
    Fiedler, Markus
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Moller, Sebastian
    Technical University of Berlin, DEU.
    Reichl, Peter
    University of Vienna, AUT.
    Xie, Min
    Telenor Research, NOR.
    A Glance at the Dagstuhl Manifesto 'QoE Vadis?'2018Inngår i: 2018 10th International Conference on Quality of Multimedia Experience, QoMEX 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, artikkel-id 8463374Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This short paper presents the recently published Dagstuhl Manifesto 'QoE Vadis?'. The Manifesto is the result of a set of three Dagstuhl Seminars and one Dagstuhl Perspectives Workshop, aimed at shaping understanding, development and application of the Quality of Experience (QoE) notion and concept. Its task is to convey the current status, promising developments and future projections for different stakeholders. The latter are summarised in a set of eleven recommendations to academia, industry and funding organisations. © 2018 IEEE.

  • 81. Fiedler, Markus
    et al.
    Nottehed, Hans
    Nordström, Patric
    The Smart Mobile Travel Guide Backstage2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper provides an overview of the ICT concepts behind the Smart Mobile Travel Guide “Seekstr”. Seekstr provides user-, situation- and position-dependent information in a seamless manner and thus belongs to a new generation of travel guides. While the mobile user uses a mobile handset as interface, in which points of interest, calendar items etc. are overlaid a map, the personalisation is performed via a web interface. The paper reviews the technological enablers for the service such as the Locago map system and the information exchange IMX. It also presents and discusses response time measurements as part of the evaluation of Quality of Experience (QoE) with Seekstr.

  • 82. Fiedler, Markus
    et al.
    Persson, Mårten
    Bertilsson, Tobias
    Situationsberoende spontan mobil informationstjänst för resenärer2005Annet (Annet vitenskapelig)
    Abstract [sv]

    This contribution describes a service (application) that provides travelers with up-to-date and relevant information while traveling. The service is planned to become part of the demonstration of seamless communications within the VINNOVA-sponsored project PIITSA = Personal Information for Intelligent Transport Systems through Seamless communications and Autonomous decisions. The application will combine streaming and interactive service in order to provide a traveler with spontaneous information regarding current disturbances affecting its travel and proposals of alternative routes, both using seamless communications. The service is designed and implemented by students from the BTH course ETD013 "Mobile Services".

  • 83.
    Fiedler, Markus
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Popescu, Adrian
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Yao, Yong
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    QoE-aware sustainable throughput for energy-efficient video streaming2016Inngår i: Proceedings - 2016 IEEE International Conferences on Big Data and Cloud Computing, BDCloud 2016, Social Computing and Networking, SocialCom 2016 and Sustainable Computing and Communications, SustainCom 2016 / [ed] Cai Z.,Luo G.,Cheng L.,Angryk R.,Li Y.,Bourgeois A.,Song W.,Cao X.,Krishnamachari B., IEEE, 2016, s. 493-500Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work motivates and details the concept of QoE-aware sustainable throughput in the area of video streaming. Sustainable throughput serves as a mean to compare video streaming solutions in terms of Quality of Experience (QoE) and energy efficiency (EE). It builds upon the QoE Provisioning-Delivery Hysteresis (PDH) and denotes the maximal throughput at which QoE deteriorations can be kept below a quantifiable level, which in turn allows to compare the EE of different video streaming solutions on QoE-fair grounds. In this work, we particularly focus on delivery problems stemming from outage-prone links, as they are typical for mobile systems. Well-adapted to the nature of the video-associated data streams and disturbances, a stochastic fluid flow model is used that allows for straightforward calculation of sustainable throughput values. We also discuss the application of the sustainable throughput for comparisons among different streaming solutions and their offered QoE and EE, respectively.

  • 84. Fiedler, Markus
    et al.
    Tran-Gia, Phuoc
    Performance assessment for new internet services2010Inngår i: International Journal of Communication Networks and Distributed Systems, ISSN 1754-3916, E-ISSN 1754-3924, Vol. 4, nr 2, s. 131-132Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Internet has shown to be the major enabler for a large variety of services via a common infrastructure. Since early applications such as remote login, e-mail, file transfer and web browsing, many new applications and services have entered the stage, where overlay networks play an important role. When broadband access technologies reached private users, file sharing became popular. Telecommunication providers have discovered internet technology as a cost-saving alternative to classical telecom technology. 3GPP has standardised the IP multimedia system (IMS), which is nowadays also used in the world of fixed access networks to handle the coexistence of voice, TV and internet (so-called Triple Play) on access links. New application domains such as e-health, e-government, e-tourism, etc., have emerged. Many new services use other services, forming composite services or service supply chains based on internet. So, the ‘anything-over-IP-over-anything’ principle has become a reality. This emergence of new applications raises challenges. The internet has never been designed for fulfilling all imaginable application’s needs, nor to maximise user’s quality of experience (QoE). During the years, the basic best-effort paradigm has been enhanced by network-level quality of service (QoS) measures. Still, internet packet delivery cannot be guaranteed. Applications try to adapt themselves to these volatile conditions, e.g., by modifying the intensity of the data flows or adding some kind of redundancy to be used for error correction, which fits the internet principle of end-to-end control. However, in order to reach the right interplay between applications and services and the internet infrastructure, a good understanding of the characteristics of both is mandatory. On this background, this special issue focuses on performance assessment of contemporary, new and emerging applications and services using the internet.

  • 85. Fiedler, Markus
    et al.
    Tutschku, Kurt
    Application of the stochastic fluid flow model for bottleneck identification and classification2003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Network performance management is facing the challenge of provisioning advanced services with stringent delay and throughput requirements. For this reason, shortage of network capacity implying delay or loss, so-called bottlenecks, have to be identified and to be classified. The latter tasks imply the need for tractable analytical performance models. We identify the stochastic fluid flow model, which is based on bit rates and its statistics, as a possible candidate of being capable of describing qualitative behaviour of bottlenecks. In this work, we show how total and individual bit rate statistics at the output of a bottleneck are calculated via the stochastic fluid flow model. From this, we deduce some general behaviours and classification criteria for bottlenecks.

  • 86. Fiedler, Markus
    et al.
    Tutschku, Kurt
    Carlsson, Patrik
    Nilsson, Arne A.
    Identification of performance degradation in IP networks using throughput statistics2003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To be able to satisfy their users, interactive applications like video conferences require a certain Quality-of-Service from heterogeneous networks. This paper proposes the use of throughput histograms as Quality-of-Service indicator. These histograms are built from local, unsynchronized, passive measurements of packet streams from the viewpoint of an application. They can easily be exchanged between sender and receiver, and their comparison provides information about severity and type of a potential bottleneck. We demonstrate the usefulness of these indicators for evaluating the transport quality perceived by a video conferencing application and its users in the presence of a bottleneck.

  • 87. Fiedler, Markus
    et al.
    Voos, Holger
    New results on the numerical stability of the stochastic fluid flow model analysis2000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The stochastic fluid flow model (SFF) is one of the leading models in performance evaluation for tele- and datacommunication systems, especially in fast packet-switching networks and ATM. However, the numerical analysis of the SFF is widely considered to be unstable. In this paper, some investigations and results are presented concerning the numerical stability of the SFF analysis also for large systems with finite buffer. We identify the main source of the numerical problems and give hints how to circumvent them. The usefulness of different solution methods are compared and the most robust methods for systems with large numbers of sources and large buffer sizes are identifed.

  • 88.
    Fiedler, Markus
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Wac, Katarzyna
    Bults, Richard
    Arlos, Patrik
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Estimating performance of mobile services from comparative output-input analysis of end-to-end throughput2013Inngår i: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 12, nr 9, s. 1761-1773Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mobile devices with ever-increasing functionality and the ubiquitous availability of wireless communication networks are driving forces behind innovative mobile applications enriching our daily life. One of the performance measures for a successful application deployment is the ability to support application-data flows by heterogeneous networks within certain delay boundaries. However, the quantitative impact of this measure is unknown and practically infeasible to determine at real-time due to the mobile device resource constraints. We research practical methods for measurement-based performance evaluation of heterogeneous data communication networks that support mobile application-data flows. We apply the lightweight Comparative Output-Input Analysis (COIA) method estimating an additional delay based on an observation interval of interest (e.g., one second) induced on the flow. An additional delay is the amount of delay that exceeds non-avoidable, minimal end-to-end delay caused by the networks propagation, serialization and transmission. We propose five COIA methods to estimate additional delay and we validate their accuracy with measurements obtained from the existing healthcare and multimedia streaming applications. Despite their simplicity, our methods prove to be accurate in relation to an observation interval of interest, and robust under a variety of network conditions. The methods offer novel insights into application-data delays with regards to the performance of heterogeneous data communication networks.

  • 89.
    Fiedler, Markus
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Zepernick, Hans-Juergen
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Kelkkanen, Viktor
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik.
    Network-induced temporal disturbances in virtual reality applications2019Inngår i: 2019 11th International Conference on Quality of Multimedia Experience, QoMEX 2019, Institute of Electrical and Electronics Engineers Inc. , 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Virtual Reality (VR) applications put high demands on software and hardware in order to enable an immersive experience for the user and avoid causing simulator sickness. As soon as networks become part of the Motion-To-Photon (MTP) path between rendering and display, there is a risk for extraordinary delays that may impair Quality of Experience (QoE). This short paper provides an overview of latency measurements and models that are applicable to the MTP path, complemented by demands on user and network levels. It specifically reports on freeze duration measurements using a commercial TPCAST wireless VR solution, and identifies a corresponding stochastic model of the freeze length distribution, which may serve as disturbance model for VR QoE studies. © 2019 IEEE.

  • 90.
    Fiedler, Markus
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Arlos, Patrik
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    QoE-based Cross-Layer Design of Mobile Video Systems: Challenges and Concepts2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This conceptual paper focuses on revealing challenges and offering concepts associated with the incorporation of the Quality of Experience (QoE) paradigm into the design of mobile video systems. The corresponding design framework combines application, middleware and networking layer in a unique cross-layer approach, in which all layers shall jointly analyse the quality of the video and its delivery in face of volatile conditions. Particular ingredients of the framework are efficient video processing, advanced realtime scheduling, and reduced-reference metrics on application and network layer.

  • 91.
    Fotrousi, Farnaz
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Fricker, Samuel
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Fiedler, Markus
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Quality Requirements Elicitation based on Inquiry of Quality-Impact Relationships2014Inngår i: Proceedings of International Requirements Engineering, IEEE , 2014, s. 303-312Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Quality requirements, an important class of non functional requirements, are inherently difficult to elicit. Particularly challenging is the definition of good-enough quality. The problem cannot be avoided though, because hitting the right quality level is critical. Too little quality leads to churn for the software product. Excessive quality generates unnecessary cost and drains the resources of the operating platform. To address this problem, we propose to elicit the specific relationships between software quality levels and their impacts for given quality attributes and stakeholders. An understanding of each such relationship can then be used to specify the right level of quality by deciding about acceptable impacts. The quality-impact relationships can be used to design and dimension a software system appropriately and, in a second step, to develop service level agreements that allow re-use of the obtained knowledge of good-enough quality. This paper describes an approach to elicit such quality-impact relationships and to use them for specifying quality requirements. The approach has been applied with user representatives in requirements workshops and used for determining Quality of Service (QoS) requirements based the involved users’ Quality of Experience (QoE). The paper describes the approach in detail and reports early experiences from applying the approach. Index Terms-Requirement elicitation, quality attributes, non-functional requirements, quality of experience (QoE), quality of service (QoS).

  • 92.
    Fotrousi, Farnaz
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik. Blekinge Inst Technol, SE-37179 Karlskrona, Sweden.;Univ Appl Sci & Arts Northwestern Switzerland FHN, Sch Engn, CH-5210 Windisch, Switzerland..
    Fricker, Samuel
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik. Blekinge Inst Technol, SE-37179 Karlskrona, Sweden.;Univ Appl Sci & Arts Northwestern Switzerland FHN, Sch Engn, CH-5210 Windisch, Switzerland..
    Fiedler, Markus
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för teknik och estetik. Blekinge Inst Technol, SE-37179 Karlskrona, Sweden..
    The effect of requests for user feedback on Quality of Experience2018Inngår i: Software quality journal, ISSN 0963-9314, E-ISSN 1573-1367, Vol. 26, nr 2, s. 385-415Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Companies are interested in knowing how users experience and perceive their products. Quality of Experience (QoE) is a measurement that is used to assess the degree of delight or annoyance in experiencing a software product. To assess QoE, we have used a feedback tool integrated into a software product to ask users about their QoE ratings and to obtain information about their rationales for good or bad QoEs. It is known that requests for feedback may disturb users; however, little is known about the subjective reasoning behind this disturbance or about whether this disturbance negatively affects the QoE of the software product for which the feedback is sought. In this paper, we present a mixed qualitative-quantitative study with 35 subjects that explore the relationship between feedback requests and QoE. The subjects experienced a requirement-modeling mobile product, which was integrated with a feedback tool. During and at the end of the experience, we collected the users' perceptions of the product and the feedback requests. Based on the users' rational for being disturbed by the feedback requests, such as "early feedback," "interruptive requests," "frequent requests," and "apparently inappropriate content," we modeled feedback requests. The model defines feedback requests using a set of five-tuple variables: "task," "timing" of the task for issuing the feedback requests, user's "expertise-phase" with the product, the "frequency" of feedback requests about the task, and the "content" of the feedback request. Configuration of these parameters might drive the participants' perceived disturbances. We also found that the disturbances generated by triggering user feedback requests have negligible impacts on the QoE of software products. These results imply that software product vendors may trust users' feedback even when the feedback requests disturb the users.

  • 93.
    Fotrousi, Farnaz
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Fricker, Samuel
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Fiedler, Markus
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Le-Gall, Frank
    KPIs for software ecosystems: A systematic mapping study2014Inngår i: Software Business: Towards Continuous Value Delivery, Springer, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To create value with a software ecosystem (SECO), a platform owner has to ensure that the SECO is healthy and sustainable. Key Performance Indicators (KPI) are used to assess whether and how well such objectives are met and what the platform owner can do to improve. This paper gives an overview of existing research on KPI-based SECO assessment using a systematic mapping of research publications. The study identified 34 relevant publications for which KPI research and KPI practice were extracted and mapped. It describes the strengths and gaps of the research published so far, and describes what KPI are measured, analyzed, and used for decision-making from the researcher's point of view. For the researcher, the maps thus capture stateof- knowledge and can be used to plan further research. For practitioners, the generated map points to studies that describe how to use KPI for managing of a SECO.

  • 94. Gustafsson, Kristian
    et al.
    Fiedler, Markus
    E-Government: services, needs and user satisfaction2004Annet (Annet vitenskapelig)
    Abstract [en]

    Within the e-government process, needs are identified and people try to come up with ideas for the public sector that will increase the effectiveness as well as lead to cost savings. Consequently, many new electronic services are being developed. As a result, Quality of Service (QoS) becomes an even more critical issue in the domain of electronic services. This paper starts by a general discussion of e-government and its services in general. Thereafter it explains different QoS factors that have been identified within the field of electronic services. The identification has been carried out by studying several researchers’ work and by experience from e-government projects. The result shows that service design, security aspects, network performance issues, as well as the users’ perspective, such as user requirements, are all factors of the QoS model. A new electronic service that does not take these factors into consideration might fail and therefore be rejected by its intended users.

  • 95. Hasslinger, Gerhard
    et al.
    Fiedler, Markus
    Analysis of deterministic servers with Ornstein-Uhlenbeck input process for voice traffic multiplexing2001Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Traffic models with a rate varying according to a Gaussian distribution are commonly used to evaluate statistical multiplexing in telecommunication systems. The Ornstein-Uhlenbeck process (OUP) is a Markovian and Gaussian process closely related to a first order autoregressive process (AR(1)). The superposition of voice or other homogeneous traffic sources asymptotically approaches an OUP in continuous time or an AR(1) in discrete time models, respectively. Performance results for a multiplexer with OUP input (OUP/D/1) are obtained based on functions of a single system parameter, We use fluid flow analysis and an approach for discrete time semi-Markovian systems to analyze the OUP/D/1 queueing system. A comparison of waiting time quantiles for input from a limited number of voice sources with the OUP/D/1 results indicates rather small deviations already for a moderate number of sources.

  • 96. Hasslinger, Gerhard
    et al.
    Fiedler, Markus
    Why buffers in switching systems do not essentially improve QoS: An analytical case study for aggregated On-off traffic2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Traffic models with a rate varying according to a Gaussian distribution are commonly used to evaluate statistical multi-plexing in telecommunication systems. The superposition of a sufficient large number of homogeneous Markovian On-Off sources asymptotically approaches an Ornstein-Uhlenbeck process (OUP) which represents a Gaussian process with ex-ponential autocorrelation function. We derive a simple expression for the bandwidth demand under QoS constraints which is close to numerical OUP/D/1 analysis results over the entire parameter region with relevance to applications. In com-parison, results of the fluid flow method for fixed aggregation level are used to verify the OUP/D/1 asymptotics and to estimate its accuracy depending on the number of aggregated flows. Moreover, the OUP/D/1 asymptotics provides a useful check of the accuracy of bounds and approximations proposed in the literature in order to improve the effective bandwidth principle. Based on analytical evaluation, the efficiency of buffers for voice traffic is finally shown to be very limited, i.e. no more than 2% of bandwidth can be saved owing to buffers with regard to real time constraints and a predefined loss probability as QoS demands for voice.

  • 97. Hasslinger, Gerhard
    et al.
    Hartleb, Franz
    Fiedler, Markus
    The relevance of the bufferless analysis for traffic management in telecommunication networks2000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study the analysis of switches or routers in a network to determine sufficient link capacities that can guarantee small loss probabilities as a main quality of service requirement. The bufferless case is considered, motivated by far simpler analysis as compared to queueing models but also by the proven inefficiency of buffering to achieve low cell or packet loss rates in the presence of real-time constraints and/or long range dependencies in the development of the traffic load, whereas statistical multiplexing can provide quality of service at reasonable bandwidth utilization even without buffering.

  • 98. Hossfeld, Tobias
    et al.
    Biedermann, Sebastian
    Schatz, Raimund
    Platzer, Alexander
    Egger, Sebastian
    Fiedler, Markus
    The memory effect and its implications on Web QoE modeling2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Quality of Experience (QoE) has gained enormous attention during the recent years. So far, most of the existing QoE research has focused on audio and video streaming applications, although HTTP traffic carries the majority of traffic in the residential broadband Internet. However, existing QoE models for this domain do not consider temporal dynamics or historical experiences of the user's satisfaction while consuming a certain service. This psychological influence factor of past experience is referred to as the memory effect. The first contribution of this paper is the identification of the memory effect as a key influence factor for Web QoE modeling based on subjective user studies. As second contribution, three different QoE models are proposed which consider the implications of the memory effect and imply the required extensions of the basic models. The proposed Web QoE models are described with a) support vector machines, b) iterative exponential regressions, and c) two-dimensional hidden Markov models.

  • 99. Hossfeld, Tobias
    et al.
    Binzenhöfer, Andreas
    Fiedler, Markus
    Tutschku, Kurt
    Measurement and Analysis of Skype VoIP Traffic in 3G UMTS Systems2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Voice-over-IP (VoIP) telephony becomes more and more popular in the wired Internet because of easy-to-use applications with high sound quality like Skype. UMTS operators promise to offer large data rates which should also make VoIP possible in a mobile environment. However, the success of those application strongly depends on the user perceived voice quality. In this paper, we therefore analyze the achievable and the actual quality of IP-based telephony calls using Skype. This is done performing measurements in both a real UMTS network and a test environment. The latter is used to emulate rate control mechanisms and changing system conditions of UMTS networks. The results show whether Skype over UMTS is able to keep pace with existing mobile telephony systems and how it reacts to different network characteristics. The investigated performance measures comprise the Perceptual Evaluation of Speech Quality (PESQ) to evaluate the voice quality, the packet loss, the inter-packet delay, and the throughput to capture networkbased factors. In this context, the concept of the Network Utility Function (NUF) is applied to describe the impact of the network on the voice quality as perceived by the end-user.

  • 100. Hossfeld, Tobias
    et al.
    Egger, Sebastian
    Schatz, Raimund
    Fiedler, Markus
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Masuch, Kathrin
    Lorentzen, Charlott
    Initial delay vs. interruptions: Between the devil and the deep blue sea2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    End user quality perception in the context of Internet applications is often characterized by waiting times before service consumption as well as interruptions during service consumption. In particular in case of bad network conditions, network and service providers have to trade off between these two impairment types, i.e. between the devil and the deep blue sea. In this paper we investigate this tradeoff in order to guide the design and development of Internet applications and network management approaches. The contribution of this paper is twofold. Firstly, we quantify the impact of initial delays on the user perceived Quality of Experience (QoE) for different application scenarios by means of subjective laboratory and crowdsourcing studies. We show that QoE for a given waiting time strongly depends on the concrete application at hand but that rating diversity remains fairly application-invariant. Secondly, using the example of YouTube video streaming we compare the influence of initial delays and interruptions (stallings) during watching. Our results demonstrate that users are extremely sensitive to interruptions and that services should be designed accordingly e.g. by increasing initial delay for prebuffering to overcome lack of resources.

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