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Supervisor: Seufert, M.: Estimating QoE of Web Browsing in the Network, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de Title: Estimating QoE of Web Browsing in the Network Abstract: This work is focused on Quality of Experience (QoE) of web browsing, i.e., the subjectively perceived goodness of the web browsing performance. First, known impact factors and metrics of web browsing (such as page load time, above the fold time, SpeedIndex) have to be tested and additional impact factors have to be identified. Afterwards, these impact factors have to be estimated from web browsing traffic, which is typically encrpyted. A measurement framework will be set up and crowdsourcing studies will be conducted to generate ground truth data. Different monitoring methods will be applied (such as model-based or machine-learning-based monitoring) and their performance for estimating the QoE of web browsing will be evaluated. Titel: Abschätzen der subjektiven Dienstgüte von Webbrowsing im Netzwerk Inhalt: Diese Arbeit beschäftigt sich mit der QoE von Webbrowsing, d.h., der subjektiven Güte des Webbrosing-Dienstes. Zuerst müssen bekannte Einflussfaktoren und Metriken (z.B. Seitenladezeit, "Über dem Knick"-Zeit, SpeedIndex) getestet werden und zusätzliche Einflussfaktoren identifiziert werden. Danach müssen diese Einflussfaktoren aus dem (typischerweise verschlüsselten) Webbrowsing-Netzwerkverkehr abgeschätzt werden. Ein Messframework wird aufgesetzt und Crowdsourcing-Studien werden durchgeführt um eine Datengrundlage zu erstellen. Verschiedene Monitoringansätze werden angewendet (z.B. modell- oder Machine-Learning-basiertes Monitoring) und ihre Leistungsfähigkeit beim Abschätzen der subjektiven Dienstgüte von Webbrowsing wird ausgewertet.
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Schlör, D., Zehe, A., Kobs, K., Veseli, B., Westermeier, F., Brübach, L., Roth, D., Latoschik, M.E., Hotho, A.: Improving Sentiment Analysis with Biofeedback Data. Proceedings of the Workshop on peOple in laNguage, vIsiOn and the miNd (ONION) (2020).
Humans frequently are able to read and interpret emotions of others by directly taking verbal and non-verbal signals in human-to-human communication into account or to infer or even experience emotions from mediated stories. For computers, however, emotion recognition is a complex problem: Thoughts and feelings are the roots of many behavioural responses and they are deeply entangled with neurophysiological changes within humans. As such, emotions are very subjective, often are expressed in a subtle manner, and are highly depending on context. For example, machine learning approaches for text-based sentiment analysis often rely on incorporating sentiment lexicons or language models to capture the contextual meaning. This paper explores if and how we further can enhance sentiment analysis using biofeedback of humans which are experiencing emotions while reading texts. Specifically, we record the heart rate and brain waves of readers that are presented with short texts which have been annotated with the emotions they induce. We use these physiological signals to improve the performance of a lexicon-based sentiment classifier. We find that the combination of several biosignals can improve the ability of a text-based classifier to detect the presence of a sentiment in a text on a per-sentence level.
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Wamser, F., Alay, Ö., Metzger, F., Valentin, S.: IJNM Special Issue - Editorial - QoE-centric Analysis and Management of Communication Networks. International Journal of Network Management. Special Issue: QoE-centric Analysis and Management of Communication Networks, (2020).
The heterogeneity and variability of Internet applications has increased considerably in recent years. Applications such as video streaming are responsible for a large part of data traffic on the Internet. Internet telephony and video conferencing systems have become part of our daily lives. At the same time, the Internet of Things is striving to exceed previous expectations regarding the number of devices. Furthermore, the proliferation of video games, virtual reality applications, and 360° video applications is increasing. All this leads to specific but different requirements from applications to frameworks, service platforms, and networks. For each service, users desire special service criteria, such as smooth interactivity, fast downloads, high availability, or extensive content. Such requirements can usually be summarized under the term Quality of Experience, i.e., the overall satisfaction of a user with the system cur- rently in use. In the age of big data and dynamic networks, Quality of Experience is still looking for its place, and good solutions are in high demand. This Special Issue addresses the latest advances and challenges in analysis, design, modeling, measurement, and performance evaluation of Quality of Experience and Quality of Experience-oriented metrics and management.
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Bucher, K., Oberdörfer, S., Grafe, S., Latoschik, M.E.: Von Medienbeiträgen und Applikationen - ein interdisziplinäres Konzept zum Lehren und Lernen mit Augmented und Virtual Reality für die Hochschullehre. In: Knaus, T. und Merz, O. (hrsg.) Schnittstellen und Interfaces - Digitaler Wandel in Bildungseinrichtungen. S. 225-238. kopaed, Munich, Germany (2020).
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Supervisor: Geissler, S.: Simulating IoT Interpolation Mechanisms to Improve Application Layer Information Quality, (2020).
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Hoßfeld, T., Wunderer, S., Beyer, A., Hall, A., Schwind, A., Gassner, C., Guillemin, F., Wamser, F., Wascinski, K., Hirth, M., Seufert, M., Casas, P., Tran-Gia, P., Robitza, W., Wascinski, W., Ben Houidi, Z.: White Paper on Crowdsourced Network and QoE Measurements – Definitions, Use Cases and Challenges. Würzburg (2020).
The goal of the white paper at hand is as follows. The definitions of the terms build a framework for discussions around the hype topic ‘crowdsourcing’. This serves as a basis for differentiation and a consistent view from different perspectives on crowdsourced network measurements, with the goal to provide a commonly accepted definition in the community. The focus is on the context of mobile and fixed network operators, but also on measurements of different layers (network, application, user layer). In addition, the white paper shows the value of crowdsourcing for selected use cases, e.g., to improve QoE or regulatory issues. Finally, the major challenges and issues for researchers and practitioners are highlighted. This white paper is the outcome of the Würzburg seminar on “Crowdsourced Network and QoE Measurements” which took place from 25-26 September 2019 in Würzburg, Germany. International experts were invited from industry and academia. They are well known in their communities, having different backgrounds in crowdsourcing, mobile networks, network measurements, network performance, Quality of Service (QoS), and Quality of Experience (QoE). The discussions in the seminar focused on how crowdsourcing will support vendors, operators, and regulators to determine the Quality of Experience in new 5G networks that enable various new applications and network architectures. As a result of the discussions, the need for a white paper manifested, with the goal of providing a scientific discussion of the terms “crowdsourced network measurements” and “crowdsourced QoE measurements”, describing relevant use cases for such crowdsourced data, and its underlying challenges. During the seminar, those main topics were identified, intensively discussed in break-out groups, and brought back into the plenum several times. The outcome of the seminar is this white paper at hand which is – to our knowledge – the first one covering the topic of crowdsourced network and QoE measurements.
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Supervisor: Geissler, S.: Simulation of a Full IoT Infrastructure, (2020).
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Supervisor: Borchert, K.: Analysis and Correlation of objective and subjective Performance Data of an Enterprise Application, (2020).
Contact: kathrin.borchert@informatik.uni-wuerzburg.de
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Wißmann, N., Mišiak, M., Fuhrmann, A., Latoschik, M.E.: Accelerated Stereo Rendering with Hybrid Reprojection-Based Rasterization and Adaptive Ray-Tracing. Proceedings of the 27th IEEE Virtual Reality conference (IEEE VR '20) (2020).
Humans frequently are able to read and interpret emotions of others by directly taking verbal and non-verbal signals in human-to-human communication into account or to infer or even experience emotions from mediated stories. For computers, however, emotion recognition is a complex problem: Thoughts and feelings are the roots of many behavioural responses and they are deeply entangled with neurophysiological changes within humans. As such, emotions are very subjective, often are expressed in a subtle manner, and are highly depending on context. For example, machine learning approaches for text-based sentiment analysis often rely on incorporating sentiment lexicons or language models to capture the contextual meaning. This paper explores if and how we further can enhance sentiment analysis using biofeedback of humans which are experiencing emotions while reading texts. Specifically, we record the heart rate and brain waves of readers that are presented with short texts which have been annotated with the emotions they induce. We use these physiological signals to improve the performance of a lexicon-based sentiment classifier. We find that the combination of several biosignals can improve the ability of a text-based classifier to detect the presence of a sentiment in a text on a per-sentence level.
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Hoßfeld, T., Heegaard, P.E., Varela, M., Skorin-Kapov, L., Fiedler, M.: From QoS Distributions to QoE Distributions: a System's Perspective. 4th International Workshop on Quality of Experience Management (QoE Management 2020), featured by IEEE Conference on Network Softwarization (IEEE NetSoft 2020). , Ghent, Belgium (2020).
In the context of QoE management, network and service providers commonly rely on models that map system QoS conditions (e.g., system response time, packet loss, etc.) to estimated end user QoE values. Observable QoS conditions in the system may be assumed to follow a certain distribution, meaning that different end users will experience different conditions. On the other hand, drawing from the results of subjective user studies, we know that user diversity leads to distributions of user scores for any given test conditions (in this case referring to the QoS parameters of interest). Our previous studies have shown that to correctly derive various QoE metrics (e.g., Mean Opinion Score (MOS), quantiles, probability of users rating 'good or better', etc.) in a system under given conditions, there is a need to consider rating distributions obtained from user studies, which are often times not available. In the paper we extend these findings to show how to approximate user rating distributions given a QoS-to-MOS mapping function and second order statistics. Such a user rating distribution may then be combined with a QoS distribution observed in a system to finally derive corresponding distributions of QoE scores. Scripts are provided for the approximating a QoE distribution with a Beta distribution for given MOS and SOS parameter at https://github.com/hossfeld/approx-qoe-distribution.
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Seufert, M., Kargl, J., Schauer, J., Nüchter, A., Hoßfeld, T.: Different Points of View: Impact of 3D Point Cloud Reduction on QoE of Rendered Images. 12th International Conference on Quality of Multimedia Experience (QoMEX). , Athlone, Ireland (2020).
Modern photogrammetric methods as well as laser measurement systems make it easy to collect large 3D point clouds that sample objects or environments. As the recorded point clouds can be used to render computer-generated images and models, they are of particular interest in the domains of geographical and architectural engineering, as well for computer graphics (e.g., games or virtual reality). However, point clouds have a huge storage demand, thus, point clouds shall be reduced by removing some of the points. This will inevitably also reduce the Quality of Experience (QoE) of media, which is rendered from the reduced point clouds. In this work, the impact of two different reduction methods on the QoE of rendered images is investigated from two point of views, i.e., based on ratings from both naive crowdworkers as well as point cloud experts.
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Hirth, M., Borchert, K., de Moor, K., Borst, V., Hoßfeld, T.: Personal Task Design Preferences of Crowdworkers. 12th International Conference on Quality of Multimedia Experience (QoMEX). , Athlone, Ireland (2020).
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Oberdörfer, S., Heidrich, D., Latoschik, M.E.: Think Twice: The Influence of Immersion on Decision Making during Gambling in Virtual Reality. Proceedings of the 27th IEEE Virtual Reality conference (VR '20). S. 483-492. IEEE, Atlanta, USA (2020).
Immersive Virtual Reality (VR) is increasingly being explored as an alternative medium for gambling games to attract players. Typically, gambling games try to impair a player’s decision making, usually for the disadvantage of the players’ financial outcome. An impaired decision making results in the inability to differentiate between advantageous and disadvantageous options. We investigated if and how immersion impacts decision making using a VR-based realization of the Iowa Gambling Task (IGT) to pinpoint potential risks and effects of gambling in VR. During the IGT, subjects are challenged to draw cards from four different decks of which two are advantageous. The selections made serve as a measure of a participant’s decision making during the task. In a novel user study, we compared the effects of immersion on decision making between a low-immersive desktop-3D-based IGT realization and a high immersive VR version. Our results revealed significantly more disadvantageous decisions when playing the immersive VR version. This indicates an impair- ing effect of immersion on simulated real life decision making and provides empirical evidence for a high risk potential of gambling games targeting immersive VR.
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Borchert, K., Seufert, M., Hildebrand, K., Hoßfeld, T.: QoE Assessment of Enterprise Applications based on Self-motivated Ratings. 12th International Conference on Quality of Multimedia Experience (QoMEX). , Athlone, Ireland (2020).
In most companies, enterprise applications, such as office products or databases, are heavily used by employees during work hours. Impairments and performance issues not only slow down business processes, but might also increase the frustration of the workforce. While Quality of Experience (QoE) has been widely studied for personal multimedia applications, such as video streaming, its application to the business usage domain is still in its infancy. Due to several reasons, e.g., the high complexity of IT infrastructure, classical QoE studies can hardly be transferred to business applications. These studies are often independent from the context of usage and actively poll ratings from their participants. This work contrasts the commonly used "pull" method for collecting user ratings with a self-motivated "push" approach. This approach is inspired by complaint systems, in which users can directly report problems with a technical system as soon as they notice them. Therefore, performance assessments of a business application from employees of a cooperating company are collected with both rating systems during a time span of 1.5 years. Besides the analysis of the interaction of users with the "push" system, differences between the two methods are discussed. Further, QoE models for the monitored business application are derived based on the self-motivated "push" ratings.
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Gray, N.: Evaluation of Offloading Firewall Rules with P4, (2020).
Contact: nicholas.gray@informatik.uni-wuerzburg.de Firewalls are classical network middle boxes, which are physically implemented within the data path. Following this design pattern causes the network to become inflexible and harder to scale as additional hardware devices have to be deployed whenever the limits of the current configuration are reached, resulting in a high maintenance and requisition cost. Network Function Virtualization (NFV) is a novel paradigm aiming to mitigate these drawbacks by shifting the function of hardware middle boxes to software programs run on Commodity of the Shelf servers. While increasing the network flexibility, it also imposes additional delays on the data path as the complete networking and software stack has to be traversed for each packet. P4 allows the execution and packet matching process on inexpensive, programmable networking cards at line rate. Goal of the thesis is the implementation and evaluation of a distributed stateful firewall based on P4.
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Byrka, J., Lewandowski, M., Spoerhase, J.: Approximating Node-Weighted k-MST on Planar Graphs. Theory of Computing Systems. (2020).
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Wehner, N., Seufert, M., Wassermann, S., Casas, P., Hoßfeld, T.: Machine Learning-based Real-time Estimation of Quality of Experience from Encrypted Video Streaming Traffic. , 1st KuVS Workshop on Machine Learning for Networking, Munich, Germany (2020).
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Oyanagi, A., Narumi, T., Lugrin, J.-L., Ando, H., Ohmura, R.: Reducing the Fear of Height by Inducing Proteus Effect of a Dragon Avatar. Journal of the Virtual Reality Society of Japan (2020).
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Hoßfeld, T., Wunderer, S.: White Paper on Crowdsourced Network and QoE Measurements - Definitions, Use Cases and Challenges. University of Würzburg, Chair of Communication Networks (2020).
The goal of the white paper at hand is as follows. The definitions of the terms build a framework for discussions around the hype topic ‘crowdsourcing’. This serves as a basis for differentiation and a consistent view from different perspectives on crowdsourced network measurements, with the goal to provide a commonly accepted definition in the community. The focus is on the context of mobile and fixed network operators, but also on measurements of different layers (network, application, user layer). In addition, the white paper shows the value of crowdsourcing for selected use cases, e.g., to improve QoE or regulatory issues. Finally, the major challenges and issues for researchers and practitioners are highlighted. This white paper is the outcome of the Würzburg seminar on “Crowdsourced Network and QoE Measurements” which took place from 25-26 September 2019 in Würzburg, Germany. International experts were invited from industry and academia. They are well known in their communities, having different backgrounds in crowdsourcing, mobile networks, network measurements, network performance, Quality of Service (QoS), and Quality of Experience (QoE). The discussions in the seminar focused on how crowdsourcing will support vendors, operators, and regulators to determine the Quality of Experience in new 5G networks that enable various new applications and network architectures. As a result of the discussions, the need for a white paper manifested, with the goal of providing a scientific discussion of the terms “crowdsourced network measurements” and “crowdsourced QoE measurements”, describing relevant use cases for such crowdsourced data, and its underlying challenges. During the seminar, those main topics were identified, intensively discussed in break-out groups, and brought back into the plenum several times. The outcome of the seminar is this white paper at hand which is – to our knowledge – the first one covering the topic of crowdsourced network and QoE measurements.
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Moldovan, C., Loh, F., Seufert, M., Hoßfeld, T.: Optimizing HAS for 360-Degree Videos. 5th IEEE/IFIP International Workshop on Analytics for Network and Service Management (AnNet). , Budapest, Hungary (2020).
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Loh, F.: Analysis of the Live Streaming Behavior of Twitch, (2020).
In der Arbeit soll das Streamingverhalten von Twitch gemessen werden und dabei vor allem auf das Verhalten bei schwankender Bandbreite eingegangen werden.
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Loh, F.: Measurement Driven Investigation of the Twitch.tv Streaming Behavior, (2020).
The goal is to create a live streaming dataset with twitch measurements on application and network layer. The goal is to measure different videos and bandwidth limitations. At the end, initial evaluations should be made to describe the streaming behavior.
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Loh, F., Wamser, F., Moldovan, C., Zeidler, B., Tsilimantos, D., Valentin, S., Hoßfeld, T.: Is the Uplink Enough? Estimating Video Stalls from Encrypted Network Traffic. 32th IEEE/IFIP Network Operations and Management Symposium. , Budapest, Hungary (2020).
Today’s traffic projections speak of almost 58 % video traffic across the Internet. Nearly all video traffic is encrypted, accounting for more than 50 % encrypted traffic worldwide. To analyze video traffic today, or even estimate its quality in the network, a deep look into the traffic characteristics has to be done. But then, important quality metrics from the traffic behavior can be derived. Based on extensive measurements we show in this work how to measure and estimate video stalls for mobile adaptive streaming. The underlying dataset includes more than 900 hours of video footage from the native YouTube app, measured over 18 different videos in 56 network scenarios in two cities in Europe. We outline a possible approach to estimate the video playback buffer size based on uplink video chunk requests in real-time to break down the video stalls. This work is intended as a tool for network operators to receive further knowledge of the characteristics of video streaming traffic to quantify the most important QoE degradation factors of one of the most important applications today.
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Mal, D.: The Impact of Social Interactions on an Embodied Individual’s Self-perception in Virtual Environments. Proceedings of the 27th IEEE Virtual Reality (VR) conference. IEEE, Atlanta, USA (2020).
In shared immersive virtual reality, users can interact with other participants and experience them as being present in the environment. Thereby different aspects of the respective interaction partners can have an impact on the perceived quality of the communication and possibly also the self-perception of an embodied user. This paper describes various factors the author aims to investigate during his doctoral studies. As the research area of embodied social interactions is broad, relevant factors and concrete research questions have been identified to investigate how social contact with one or multiple other persons may affect one’s self-perception, behavior and her or his relationship with the others while being embodied in a virtual environment.
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Janiak, L.: Potential Traffic Savings by Leveraging Proximity of Communication Groups in Mobile Messaging Applications, (2020).
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Supervisor: Wehner, N.: Fingerprinting Websites in Encrypted Network Traffic, (2020).
Contact/Kontakt: nikolas.wehner@informatik.uni-wuerzburg.de Due to the encryption of network traffic and the introduction of DNS over HTTPS, the task of identifying websites based on the corresponding network traffic got difficult. Nonetheless, ISPs want to know which kind of traffic passes their networks in order to optimize the QoE of their customers. The goal of this work is to create a model which is able to reliably predict the called websites during a session. Therefore, reasonable features have to be extracted from the data and afterwards they have to be ingested into selected Machine Learning algorithms.
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Münster, S., Niebling, F., Bruschke, J., Barthel, K., Friedrichs, K., Kröber, C., Maiwald, F.: Urban History Research and Discovery in the Age of Digital Repositories. A Report About Users and Requirements. In: Kremers, H. (hrsg.) Digital Cultural Heritage. S. 63--84. Springer International Publishing, Cham (2020).
The research group on four-dimensional research and communication of urban history (HistStadt4D) investigates and develops methods and technologies to transfer extensive repositories of historical photographs and their contextual information into a three-dimensional spatial model, with an additional temporal component. This will make content accessible to researchers and the public, via a 4D browser as well as a location-dependent augmented reality representation. Against this background, this article highlights users and requirements of both scholarly and touristic usage of digital information about urban history, in particular historical photographs.
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Gray, N.: Evaluation of the Impact of Network Topologies and Applications on Synchronization Strategies of Distributed SDN Controllers, (2020).
Software-defined Networking (SDN) separates the data from the control plane and outsources the latter to a logically centralized instance called the controller. This enables a common view of the network topology and provides a central entity for network configurations. The controller is often distributed to impose no single point of failure and to balance the load efficiently among the physical controller instances. To maintain a consistent view of the network, synchronization between the individual controller instances is required. Controller implementations can be categorized by their utilized synchronization strategy and largely fall in one of two categories, namely horizontal or hierarchical. Goal of this thesis is to evaluate the impact of the network topology and running controller applications on the performance of the controller when using different synchronization mechanisms. As access to large SDN test beds is limited the investigations will be done by simulations within the OMNeT++ framework.
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Supervisor: Grigorjew, A.: Consolidation of Resources and Demands in VNF Chain Placement Problems (BA), (2020).
Contact: Alexej Grigorjew <alexej.grigorjew@informatik.uni-wuerzburg.de> Placing Virtual Network Functions in network graphs is an NP-hard problem. Solving large problem instances is often unfeasible due to limited computational resources and time. For many use cases, the problem input is not required in all detail, but can be aggregated into a smaller abstraction. In this work, an algorithm should be implemented that generates such smaller representations of graphs and VNF demands. Further, its performance shall be evaluated by applying (existing) solvers on the results and comparing both runtime and quality of their placements with the original graph.
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Ripka, G., Tiede, J., Grafe, S., Latoschik, M.E.: Teaching and Learning Processes in Immersive VR – Comparing Expectations of Preservice Teachers and Teacher Educators. Society for Information Technology & Teacher Education (SITE) International Conference (2020).
The usage of VR in higher education is not uncommon anymore. However, concepts are mainly still focusing on technical rather than pedagogical aspects of VR in the classroom. The exploration of the expectations of teacher educators as well as of preservice teachers appears indispensable (1) to achieve a sound understanding of requirements, (2) to identify potential design spaces, and finally (3) to create and to derive suitable pedagogical approaches for VR in initial teacher education. This paper presents results of guideline-based qualitative interviews comparing the expectations of teacher educators and of preservice teachers regarding teaching and learning in immersive virtual learning environments. The results showed that preservice teachers and teacher educators expect VR to enrich classes through interactive engagement in situations that would otherwise be too costly or dangerous. Regarding the design, teacher educators put the emphasis on functionality. Student teachers emphasized that they do not want to miss social interactions with their peers. Furthermore, both groups stated preferred modes of collaboration and interaction taking into account the characteristics of a virtual learning surrounding such as being able to use diverse learning spaces for group work. Interviewees agreed on two vital factors for effective learning and teaching processes: flexibility and the possibility of customization considering technical properties that are to deal with. Apart from this, preservice teachers emphasized strongly their worries about data usage and the ethics regarding using avatars and agents for representation.
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Dworschak, N.-D.: Evaluating Temporal Impairments in Music Streaming, (2020).
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Supervisor: Schwind, A.: Predicting QoE of Music Streaming, (2020).
Contact: anika.schwind@informatik.uni-wuerzburg.de
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Supervisor: Loh, F.: Use Case Study of the Transmission Behavior of an Application Using LoRaWAN, (2020).
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Supervisor: Loh, F.: Studying the Scalability of LoRaWAN with Omnet++, (2020).
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Supervisor: Loh, F.: Analyzing the Streaming Behavior of the Amazon Echo Show, (2020).
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Supervisor: Loh, F.: A Simulative Approach to Study the Coverage of LoRaWAN in Würzburg, (2020).
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Byrka, J., Lewandowski, M., Meesum, S.M., Spoerhase, J., Uniyal, S.: PTAS for Steiner Tree on Map Graphs. Proc. 14th Latin American Theoretical Informatics Symposium (LATIN'20) (2020).
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Kaufmann, M., Kratochvil, J., Lipp, F., Montecchiani, F., Raftopoulou, C., Valtr, P.: The Stub Resolution of 1-Planar Graphs. In: Rahman, M.S., Sadakane, K., und Sung, W.-K. (hrsg.) WALCOM: Algorithms and Computation. S. 170--182. Springer (2020).
The resolution of a drawing plays a crucial role when defining criteria for its quality. In the past, grid resolution, edge-length resolution, angular resolution and crossing resolution have been investigated. In this paper, we investigate the stub resolution, a recently introduced criterion for nonplanar drawings. A crossed edge is divided into parts, called stubs, which should not be too short for the sake of readability. Thus, the stub resolution of a drawing is defined as the minimum ratio between the length of a stub and the length of the entire edge, over all the edges of the drawing. We consider 1-planar graphs and we explore scenarios in which near optimal stub resolution, i.e. arbitrarily close to \\($\$\)\backslashfrac\1\\2\\\($\$\), can be obtained in drawings with zero, one, or two bends per edge, as well as further resolution criteria, such as angular and crossing resolution. In particular, our main contributions are as follows: (i) Every 1-planar graph with independent crossing edges has a straight-line drawing with near optimal stub resolution; (ii) Every 1-planar graph has a 1-bend drawing with near optimal stub resolution.
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Halloway, M.: Evaluating the QoE of Music Streaming Applications, (2020).
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Supervisor: Schwind, A.: Investigating the QoE of Mobile Messaging, (2020).
Contact: anika.schwind@informatik.uni-wuerzburg.de
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Korger, A., Baumeister, J.: Case-Based Generation of Regulatory Documents and their Semantic Relatedness. Proceedings of the Future of Information and Communications Conference (FICC) 2020. Springer, San Francisco. (2020).
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Supervisor: Seufert, M.: Transfer Learning Approaches for QoE Monitoring of Encrypted Video Streaming Traffic, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de Title: Transfer Learning Approaches for QoE Monitoring of Encrypted Video Streaming Traffic Abstract: This work is focused on Quality of Experience (QoE) monitoring of encrypted video streaming traffic. Here, machine learning based methods are used to estimate QoE metrics based on features, which are extracted from the encrypted traffic. While these machine learning models achieve very good performance for a specific training data set, they typically show a worse performance when applied to different data sets. Thus, in this thesis, transfer learning approaches shall be tested and/or developed, which allow the existing models to generalize also over heterogeneous data sets. The performance of the transfer learning approaches shall be evaluated and a methodology for generalizing machine learning based QoE monitoring models shall be developed. Titel: Transferlernverfahren bei der QoE Messung auf verschlüsseltem Videostreamingverkehr Inhalt: Diese Arbeit beschäftigt sich mit der QoE Messung auf verschlüsseltem Videostreamingverkehr. Hierbei werden Methoden des maschinellen Lernens (ML) eingesetzt um QoE-Metriken zu schätzen basierend auf Features, die aus dem verschlüsselten Verkehr extrahiert werden. Während diese ML-Modelle sehr gute Leistung für spezifische Datensätze zeigen, haben sie typischerweise eine schlechtere Leistung wenn sie auf andere Datensätze angewandt werden. Deshalb sollen in dieser Arbeit Transferlernverfahren getestet und/oder entwickelt werden, die es erlauben, dass die existierenden Modelle auch für heterogene Datensätze verallgemeinert werden können. Die Leistung der Transferlernansätze soll bewertet werden und eine Methodik für die Generalisierung von ML-Modellen für QoE Messungen soll entwickelt werden.
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Supervisor: Schwind, A.: Crowdsourced Network Measurements: Evaluation and Applicability for 5G, (2020).
Contact: anika.schwind@informatik.uni-wuerzburg.de
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Mertinat, N.: Impact of Content Selection on Crowdsourced QoE Studies of HTTP Adaptive Streaming on Mobile Devices, (2020).
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Supervisor: Seufert, M.: Evaluation of the Impact of Cross-Traffic on TCP and QUIC Video Streaming, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de Title: Evaluation of the Impact of Cross-Traffic on TCP and QUIC Video Streaming Abstract: The goal of this work is to prepare, conduct, and evaluate a measurements study, which investigates the impact of cross-traffic on TCP and QUIC video streaming. For that, an existing measurement framework can be reused. Moreover, impact factors with respect to the configuration of the transport protocols shall be identified and investigated in detail during this work. Titel: Auswertung des Einflusses von Störverkehr auf TCP- und QUIC-basiertes Videostreaming Inhalt: Das Ziel dieser Arbeit ist es eine Messstudie vorzubereiten, durchzuführen und auszuwerten bei der der Einfluss von Störverkehr auf TCP- und QUIC-basiertes Videostreaming untersucht wird. Dazu kann auf ein existierendes Messframework aufgesetzt werden. Im Verlauf der Arbeit sollen außerdem Einflussfaktoren bei der Konfiguration der Transportprotokolle identifiziert werden und genauer untersucht werden.
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Supervisor: Seufert, M.: Identifying User Behavior from Encrypted Video Streaming Traffic, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de Title: Identifying User Behavior from Encrypted Video Streaming Traffic Abstract: In this work, existing PC- and app-based measurement frameworks have to be modified to conduct video streaming measurements with emulated user interactions. Application and network layer streaming information shall be extracted and analyzed to identify the emulated user interactions from the encrypted streaming traffic. Titel: Indentifizierung von Nutzerverhalten aus verschlüsseltem Videostreaming-Netzwerkverkehr Inhalt: In dieser Arbeit sollen existierende PC- und App-basierte Messframeworks modifiziert werden, um Messungen von Videostreaming durchzuführen und Nutzerinteraktionen zu emulieren. Streaminginformationen sollen auf Applikations- und Netzwerkschicht extrahiert werden, um die emulierten Nutzerinteraktionen aus dem verschlüsselten Videostreaming-Netzwerkverkehr zu identifizieren.
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Supervisor: Seufert, M.: Characterization of Browsing Sessions, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de Title: Characterization of Browsing Sessions Abstract: The goal of this work is to characterize browsing sessions, which consist of visits to multiple web pages. In particular, the navigation timing between page visists shall be modelled. Titel: Charakterisierung von Browsingsessions Inhalt: Das Ziel dieser Arbeit ist die Charakterisierung von Browsingsessions, die üblicherweise aus Besuchen von mehreren Seiten bestehen. Insbesondere sollen dabei zeitliche Aspekte der Navigation modelliert werden.
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Supervisor: Seufert, M.: Algorithms Towards Proactive QoE-aware Traffic Management, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de Title: Algorithms Towards Proactive QoE-aware Traffic Management Abstract: QoE-aware traffic management aims at improving the packet transmission and handling in the network in order to maximize the Quality of Experience (QoE) of Internet services. While most of today's approaches follow a reactive design, i.e., they change the traffic management only after a QoE degradation are detected or imminent, the focus of this work is to advance towards a more proactive design. This means algorithms shall be developed to improve the traffic management, such that it can be adjusted to changing network and service characteristics before QoE degradations can be noticed by the end users. In the thesis, also the performance of the algorithms shall be evaluated. Titel: Algorithmen für proaktives QoE-bewusstes Verkehrsmanagement Inhalt: QoE-bewusstes Verkehrsmanagement zielt darauf die Übertragung und den Umgang mit Paketen im Netzwerk zu verbessern, um damit die subjektive Dienstgüte (QoE) von Internetdiensten zu verbessern. Während die meisten der heutigen Ansätze eher ein reaktives Design haben, d.h., sie ändern das Verkehrsmanagement erst wenn eine Verschlechterung der QoE wahrgenommen wurde oder unmittelbar bevorsteht, liegt der Fokus dieser Arbeit darauf eine proaktiveres Design voranzubringen. Das bedeutet, dass Algorithmen entworfen werden sollen, um das Verkehrsmanagement zu verbessern, so dass es auf sich ändernde Netzwerk- und Dienstcharakteristika adaptiert werden kann bevor Verschlechterungen der QoE vom Endnutzer wahrgenommen werden können. In der Arbeit soll auch die Leistung der Algorithmen bewertet werden.
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Gall, D., Latoschik, M.E.: Visual angle modulates affective responses to audiovisual stimuli. Computers in Human Behavior. 109, 106346 (2020).
What we see influences our emotions. Technology often mediates the visual content we perceive. Visual angle is an essential parameter of how we see such content. It operationalizes visible properties of human-computer interfaces. However, we know little about the content-independent effect of visual angle on emotional responses to audiovisual stimuli. We show that visual angle alone affects emotional responses to audiovisual features, independent of object perception. We conducted a 2 x 2 x 3 factorial repeated-measures experiment with 143 undergraduate students. We simultaneously presented monochrome rectangles with pure tones and assessed valence, arousal, and dominance. In the high visual angle condition, arousal increased, valence and dominance decreased, and lightness modulated arousal. In the low visual angle condition, pitch modulated arousal, and lightness affected valence. Visual angle weights the affective relevance of perception modalities independent of spatial representations. Visual angle serves as an early-stage perceptual feature for organizing emotional responses. Control of this presentation layer allows for provoking or avoiding emotional response where intended.
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Roth, D., Westermeier, F., Brübach, L., Feigl, T., Schell, C., Latoschik, M.E.: Brain 2 Communicate: EEG-based Affect Recognition to Augment Virtual Social Interactions. Mensch und Computer 2019 - Workshopband. Gesellschaft für Informatik e.V., Bonn (2019).
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Seufert, M., Schatz, R., Wehner, N., Gardlo, B., Casas, P.: Is QUIC becoming the New TCP? On the Potential Impact of a New Protocol on Networked Multimedia QoE. 11th International Conference on Quality of Multimedia Experience (QoMEX). , Berlin, Germany (2019).
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Obremski, D., Lugrin, J.-L., Schaper, P., Lugrin, B.: Non-Native Speaker Generation and Perception for Mixed-Cultural Settings. ACM International Conference on Intelligent Virtual Agents 2019. (2019).
This paper presents an experiment evaluating the effects of virtual agents' language proficiency on whether they are perceived as a native speakers or not. Our first results indicate that beyond 10% word order mistakes and 25% infinitive mistakes, virtual agents are perceived as non-native speakers, even though their appearance and non-verbal behaviour were not altered. We believe these thresholds constitute interesting guidelines possibly simplifying the design of non-native speaker simulations.
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Tönsing, L.: Untersuchung des Einflusses der Anleitungs- und Bearbeitungssprache auf die Ergebnisqualität von Crowdsourcing-Aufgaben, (2019).
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Nogatz, F., Seipel, D., Abreu, S.: Definite Clause Grammars with Parse Trees: Extension for Prolog. Proceedings of 8th Symposium on Languages, Applications, Technologies (SLATE). S. 7:1-7:14 (2019).
Definite Clause Grammars (DCGs) are a convenient way to specify possibly non-context-free grammars for natural and formal languages. They can be used to progressively build a parse tree as grammar rules are applied by providing an extra argument in the DCG rule’s head. In the simplest way, this is a structure that contains the name of the used nonterminal. This extension of a DCG has been proposed for natural language processing in the past and can be done automatically in Prolog using term expansion. We extend this approach by a meta-nonterminal to specify optional and sequences of nonterminals, as these structures are common in grammars for formal, domain-specific languages. We specify a term expansion that represents these sequences as lists while preserving the grammar’s ability to be used both for parsing and serialising, i.e. to create a parse tree by a given source code and vice-versa. We show that this mechanism can be used to lift grammars specified in extended Backus–Naur form (EBNF) to generate parse trees. As a case study, we present a parser for the Prolog programming language itself based only on the grammars given in the ISO Prolog standard which produces corresponding parse trees.
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Metzger, F., Hoßfeld, T., Bauer, A., Kounev, S., Heegaard, P.E.: Modeling of Aggregated IoT Traffic and Its Application to an IoT Cloud. Proceedings of the IEEE. 107, 679-694 (2019).
As the Internet of Things (IoT) continues to gain traction in telecommunication networks, a very large number of devices are expected to be connected and used in the near future. In order to appropriately plan and dimension the network, as well as the back-end cloud systems and the resulting signaling load, traffic models are employed. These models are designed to accurately capture and predict the properties of IoT traffic in a concise manner. To achieve this, Poisson process approximations, based on the Palm–Khintchine theorem, have often been used in the past. Due to the scale (and the difference in scales in various IoT networks) of the modeled systems, the fidelity of this approximation is crucial, as, in practice, it is very challenging to accurately measure or simulate large-scale IoT deployments. The main goal of this paper is to understand the level of accuracy of the Poisson approximation model. To this end, we first survey both common IoT network properties and network scales as well as traffic types. Second, we explain and discuss the Palm–Khintiche theorem, how it is applied to the problem, and which inaccuracies can occur when using it. Based on this, we derive guidelines as to when a Poisson process can be assumed for aggregated periodic IoT traffic. Finally, we evaluate our approach in the context of an IoT cloud scaler use case.
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Mizrachi, E., Schwartz, R., Spoerhase, J., Uniyal, S.: A Tight Approximation for Submodular Maximization with Mixed Packing and Covering Constraints. Proc. 46th International Colloquium on Automata, Languages and Programming (ICALP'19) (2019).
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Seufert, M., Wehner, N., Casas, P.: A Fair Share for All: TCP-inspired Adaptation Logic for QoE Fairness among Heterogeneous HTTP Adaptive Video Streaming Clients. IEEE Transactions on Network and Service Management. 16, 475-488 (2019).
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Kryven, M., Ravsky, A., Wolff, A.: Drawing Graphs on Few Circles and Few Spheres. Journal of Graph Algorithms & Applications. 23, 371--391 (2019).
Given a drawing of a graph, its emphvisual complexity is defined as the number of geometrical entities in the drawing, for example, the number of segments in a straight-line drawing or the number of arcs in a circular-arc drawing (in 2D). Recently, Chaplick et al. [GD 2016] introduced a different measure for the visual complexity, the emphaffine cover number, which is the minimum number of lines (or planes) that together cover a crossing-free straight-line drawing of a graph G in 2D (3D). In this paper, we introduce the emphspherical cover number, which is the minimum number of circles (or spheres) that together cover a crossing-free circular-arc drawing in 2D (or 3D). It turns out that spherical covers are sometimes significantly smaller than affine covers. For complete, complete bipartite, and platonic graphs, we analyze their spherical cover numbers and compare them to their affine cover numbers as well as their segment and arc numbers. We also link the spherical cover number to other graph parameters such as treewidth and linear arboricity.
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Maggi, L., Leguay, J., Seufert, M., Casas, P.: Online Detection of Stalling and Scrubbing in Adaptive Video Streaming. 17th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt). , Avignon, France (2019).
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Ott, S.: Design and Performance Evaluation of NMS-aware SDN Controle Plane Mechanisms, (2019).
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Seufert, M., Casas, P., Wehner, N., Li, G., Kuang, L.: Features that Matter: Feature Selection for On-line Stalling Prediction in Encrypted Video Streaming. 2nd International Workshop on Network Intelligence (NI). , Paris, France (2019).
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Münster, S., Messemer, H., Große, P., Kuroczyński, P., Niebling, F.: Das Wissen in der 3D-Rekonstruktion. In: Sahle, P. (hrsg.) DHd 2019 Digital Humanities: multimedial & multimodal. Konferenzabstracts, Frankfurt am Main. S. 63-65 (2019).
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Popp, C.: Measurement and Analysis of QoE Influencing Factors for WebRTC, (2019).
Web Real-Time-Communication (WebRTC) beinhaltet eine Reihe neuartiger Tech- nologien und Standards zur qualitativ hochwertigen Audio-, Video- und Datenüber- tragung zwischen Web-Nutzern und Nutzergruppen. Alles wird under der Prämisse der Echtzeitkommunikation übertragen, so dass Interaktivität ermöglicht wird, also der Dialog und Wechselbeziehung zwischen Nutzern für alle drei Arten der Übertra- gung in WebRTC. So erlaubt WebRTC hiermit das Chatten, Telefonieren, Video- Telefonieren, Screensharing, Webinars und Video-Games im Browser unabhängig von der zugrunde liegenden Hardwareplattform, sei es mit Hilfe von Web- oder mobilen Anwendungen ohne dass zusätzliche Plugins erforderlich sind. Hierfür ver- wendet WebRTC eine Kommunikationsarchitektur die Datenübertragung auf zwei Wegen ermöglicht. Eine Möglichkeit ist die Verwendung eines zentralen Servers, der vom Dienstanbieter bereitgestellt werden muss. Daten an andere Clients in der Session werden über den Server an die entsprechenden Empfänger weitergeleitet (RELAY). Die zweite Möglichkeit ist die direkte Kommunikation der Clients unter- einander (P2P). Da es aufgrund der Verwendung von Network Address Translation (NAT) und Firewalls in der Regel unmöglich ist, direkt Daten an Clients in anderen Netzwerken zu schicken, verwendet WebRTC Interactive Connectivity Establish- ment (ICE), um direkte Kommunikation zu ermöglichen. WebRTC wird vom World Wide Web Consorcium (W3C) und von der Internet Engineering Task Force (IETF) entwickelt und standardisiert. Seit der initialen Veröffentlichung im Jahr 2011 wird WebRTC von einer Vielzahl bekannter Dienste zur Bereitstellung von Echtzeitkom- munikation verwendet. Zu diesen Diensten zählen u.a. Google Hangouts, Facebook Messenger und Citrix GoToMeeting. Diese Arbeit diskutiert Einflussfaktoren auf System und Netzwerkebene, welche die Quality of Experience (QoE) im Kontext von WebRTC beeinflussen. Basierend auf der Analyse bestehender Literatur zu den Themenbereichen Echtzeitkommu- nikation und QoE wurde eine Reihe an Parametern, welche die Nutzererfahrung beeinflussen, identifiziert. Mithilfe dieser Parameter wurden drei Metafaktoren Syn- chronität, Stabilität und Qualität definiert, welche für die QoE relevant sind. Diese werden mittels Key Performance Indikatoren (KPI) näher bestimmt. Jeder KPI be- trachtet einen spezifischen Aspekt des Metafaktors, zu welchem er gehört. Um das Verhalten der Metafaktoren zu untersuchen, wurde ein Mess-Framework implemen- tiert. Dieses ermöglicht automatische und replizierbare Messungen von WebRTC- Anwendungen im Browser. Im Rahmen dieser Messungen ist es möglich, das wie- dergegebene Video, die Dauer einzelner Messungen, die Anzahl an Teilnehmern, so- wie die Sendebandbreite zu definieren. Während der Messungen werden automatisch Messdaten gesammelt. Im Anschluss werden die Daten aller Teilnehmer automatisch auf einem Kontroll-PC gesammelt und für die Weiterverarbeitung organisiert. Das Framework steht öffentlich zum herunterladen bereit. Mithilfe des Mess-Frameworks wurden mehrere Messreihen mit zwei und drei Teilnehmern durchgeführt, um QoE Einflussfaktoren für WebRTC zu analysieren und näher zu bestimmen. Während der Messreihen wurde die Bandbreite zwischen 250 kbit/s and 50 Mbit/s variiert. Die allgemeine Evaluation der Messdaten zeigt, dass bei der Analyse der Einfluss- faktoren von Nutzerzufriedenheit und QoE zwischen den verschiedenen möglichen Kommunikationsmodi unterschieden werden muss. Falls an einer Session nur zwei Teilnehmer teilnehmen, wird im Laufe der Session von RELAY zu P2P-Kommuni- kation gewechselt. Gibt es hingegen drei Teilnehmer, wird während der gesamten Session mittels RELAY kommuniziert. Dies trifft für die implementierte ICE- und WebRTC-Serverinfrastruktur mit jitsi-Server und Chrome-Browser beim Client zu. Hiermit wird die Datenmenge, welche von einem einzelnen Client gesendet werden muss, reduziert. Vergleicht man die RELAY und die P2P-Phase von einer Messung mit zwei Teilnehmern, ist auffällig, dass die RELAY-Phase unabhängig von der Netz- werkbandbreite eine konstant hohe Stabilität der erfassten Parameter aufweist. Die P2P-Phase hingegen benötigt eine gewisse Mindestbandbreite, um diese Stabilität zu erreichen. In der P2P-Phase ist die maximal erreichbare Videobitrate allerdings höher, was die Nutzerzufriedenheit laut QoE-Studien beeinflussen kann. Messungen mit drei Teilnehmern weisen ein Verhalten vergleichbar mit der RELAY Phase von Messungen mit zwei Teilnehmern auf. Im Bezug auf den Metafaktor Synchronität ist auffällig, dass für alle Phasen und sowohl mit zwei, als auch mit drei Teilnehmern, eine Mindestbandbreite von 500 kbit/s notwendig ist, um eine gute Bewertung der Synchronität zu erreichen. Eine Ausnahme hiervon bildet die Audio/Video-Synchronisation. Diese erfordert im Fall von zwei Teilnehmern eine Mindestbandbreite von 2.0 Mbit/s. Nehmen drei Cli- ents an der Messung teil, sind die erreichten Werte für die Audio/Video-Synchronität durchgängig schlechter als für zwei Clients. Der zweite Metafaktor ist Stabilität. Für diesen gibt es größere Unterschiede be- zogen auf das Verhalten von RELAY und P2P-Phase. Während der RELAY-Phase werden durchgängig hohe Werte für die verschiedenen KPIs berechnet. Die berech- neten Werte ändern sich zeitweise, allerdings sind sie dennoch konstant höher als die Werte der P2P-Phase. Bezogen auf den KPI Auflösung, liegt der Haupgrund für die schlechte Bewertung der P2P-Phase in der Art und Weise, wie die Videoauflösung an die verfügbare Bandbreite angepasst wird. Im Fall des zweiten KPIs, welcher die Videoauflösung betrachtet, zeigt die P2P-Phase ein Verhalten ähnlich zum ersten Metaparameter. Geringe Bandbreiten führen zu schlechten Werten. Mit steigender Bandbreite verbessern sich diese und bleiben nach dem Erreichen des Maximums konstant. Aufgrund des beschriebenen Verhaltens wird die Stabilität der RELAY- Phase konstant besser bewertet als die der P2P-Phase. Messungen mit zwei Teil- nehmern zeigen ein Verhalten ähnlich der RELAY-Phase von Messungen mit zwei Teilnehmern. Qualität ist der dritter Metafaktor. Unabhängig von der konfigurierten Bandbrei- te erreicht die P2P-Phase hier immer bessere Bewertungen als die RELAY-Phase, was auch im angegeben Modell in der Arbeit durch Zahlen bestätigt wird. Zwi- schen der Bewertung von Audio- und Videodaten gibt es signifikante Unterschiede. Aufgrund technischer Einschränkungen unterstützt das Messframework keine Wie- dergabe von Audio. Das führt dazu, dass automatisch eine regelmäßige Abfolge von Pieptönen wiedergegeben wird. Wir vermuten, dass dies dazu führt, dass der Audio Adaptionsmechanismus von WebRTC nicht funktioniert. Aufgrund dieser Annahme betrachten wir die Audioqualität als konstanten Faktor. Der zweite KPI, welcher die Qualität betrifft, behandelt die Videoqualität. Sofern die verfügbare Bandbrei- te größer als 2.0 Mbit/s ist, erreicht die P2P-Phase konstant bessere Werte als die RELAY-Phase. Andernfalls sind die Werte der beiden Phasen vergleichbar. Hohe Bandbreiten zeigen eine Limitierung der RELAY-Phase bezüglich der Videobitrate. Wir vermuten, dass es sich hierbei um Limitierungen handelt, welche vom Betreiber des Dienstes eingerichtet wurden. Die Messungen mit drei Teilnehmern zeigen ein ähnliches Verhalten wie die RELAY Phase, allerdings sind die maximal erreichten Bitraten pro Video geringer. Zuletzt definieren wir eine simple Abschätzungsfunktion QoE simple für die QoE von WebRTC aufgrund unserer bisherigen Analyse für die Infrastruktur unseres Frameworks. Diese ist definiert als der Durchschnitt der Metafaktoren. Die berech- neten Werte für QoE simple zeigen, dass die RELAY-Phase für geringe Bandbreiten geringfügig bessere Werte erreicht. Im Fall höherer Bandbreiten ergibt sich ein Vor- teil zugunsten der P2P-Phase. Das Modell erlaubt WebRTC-Anbietern und Provi- dern die Abschätzung der QoE über eine simple Messung von Einflussfaktoren. Die subjektive Validierung des Modells wird in einer nächsten Arbeit angegangen. Alle Metafakotoren wurden aufgrund des bisherigen Stands der Technik in der Literatur ausgewählt und eingebunden.
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Prantl, T.: Machine Learning for Synthetically Generated, Adaptive Streaming Data, (2019).
Ziel dieser Arbeit war es, die Einsatzmöglichkeiten maschinellen Lernens im Bereich des adaptiven Videostreamings zu analysieren und entsprechende Grundlagen zu schaffen. Insbesondere zielt die Arbeit darauf ab, im großen Stil Streaming-Daten synthetisch zu generieren, die als Eingabe für maschinelles Lernen verwendet werden können. Zu diesem Zweck beginnt die Ausarbeitung damit, Grundlagen und Verfah- ren zu erklären, sowie eine Auswahl aus verwandten Arbeiten zu treffen, um daraus wertvolle Ideen abzuleiten. Einer der wichtigsten Begriffe in diesem Zusammenhang war die Definition und Abstraktion des adaptiven Video-Streamings. Hierbei wurden verschiedene Streaming-Adapationsalgorithmen modelliert und neu implementiert, die die Bitrate für die Filmsegemente, die sogenannten Chunks, bestimmen. Ähnlich wichtig war der Begriff der Quality of Experience, die im weiteren Verlauf der Ar- beit als Bewertungsmethode für das Streaming-Erlebnis beim Benutzer diente. Es wurde zu Beginn ein Überblick über die verschiedenen bekannten Verfahren aus der Literatur gegeben. Anschließend wurden die technischen Details, die möglichen Eingabeparameter und die Auswirkungen der verschiedenen Bewertungsverfahren diskutiert. Die Arbeit nutzt lediglich vorhandene QoE-Modelle aus der Literatur. Die Erstellung und Validierung von neuen QoE-Modellen ist nicht Gegenstand der aktuellen Arbeit. Im Hinblick auf verwandte Arbeiten wurden Arbeiten von Orsolic et al. und Mao et al. herangezogen. Als Ergebnis daraus wurden, mit Blick auf das geplante Vor- haben, folgende Ziele aufgstellt: einen umfangreichen Datensatz mit dem Verhalten verschiedener Adaptionsalgorithmen in stark flukturierenden Netzwerken zu generie- ren, geeignete Kombinationen von Algorithmen zu testen und einen globalen Ansatz zur Optimierung von Video-Streaming-Vorgängen mit Hilfe von Ensemble-Learning zu finden. Das erste Ziel war folglich, einen entsprechend großen inhomogenen Streaming- Datensatz für zukünftige Forschungsarbeiten bereitzustellen. Ein möglicher Ansatz bestand darin, dies mit Hilfe von synthetisch generierten Daten zu realisieren. Dazu wurde die synthetische Erzeugung von Streaming-Daten untersucht, um eine Metho- de zur schnellen Herstellung von Streaming-Daten zu erhalten. Zu diesem Zweck wur- de eine Simulation entwickelt, die das Verhalten der Adaptionsalgorithmen BBA0, FESTIVE und PANDA für ein bestimmtes Video in einem bestimmten Netzwerk, mittels eines generalisierten Modelles, berechnet. Um die Genauigkeit dieser Simu- lation zu überprüfen, wurden für jeden Algorithmus drei Streaming-Prozesse real durchgeführt und in der Simulation nachgestellt. Der Vergleich des simulierten und realen Streaming-Prozesses zeigte eine gute Übereinstimmung zwischen Simulati- on und Realität und außerdem, dass ein Adaptionsverfahren umso besser simuliert werden kann, je mehr es die zeitliche Entwicklung der Parameter berücksichtigt. Mit dem Begriff Quality of Experience (QoE) wurde eine Möglichkeit zur Bewertung der simulierten Streamingvorgänge genutzt und anschließend wurden gängige QoE-Verfahren vorgestellt, aus denen eine begründete Auswahl getroffen wurde. Um mit der Simulation möglichst viele Streaming-Daten zu erzeugen, wurde eine Toolchain für deren automatisierte Generierung vorgestellt. Die Toolchain umfasst dabei die automatische Herstellung und Konvertierung von Videos, deren Simulation durch alle vorgegebenen Netzwerke mittels der drei eingeführten Adaptionsverfah- ren sowie die Bewertung des simulierten Streamingvorganges mit Hilfe von sieben vorgegebenen unterschiedlichen QoE-Modellen. Mit dieser Toolchain wurden fast 3 Millionen Streamingprozesse generiert, die auf die einzelnen Verfahren verteilt sind. Neben der Simulation der herkömmlichen Verfahren wurde eine neue Simulati- onsmethode trainiert, welche die herkömmlichen Vorgehensweisen der Algorithmen BBA0, FESTIVE und PANDA kombiniert. Das neue Verfahren fand heraus, dass man im Schnitt die gleiche durchschnittliche QoE erhält wie das beste herkömmliche Verfahren, wenn man immer nur die zwei höchsten Bitraten wählt. Aus diesem Ver- halten ließ sich schlussfolgern, dass die Analyse der verwendeten QoE-Modelle und deren möglichst optimale Ausprägung auf dem verwendeten Datensatz essentiell für maschinelles Lernen in diesem Bereich ist. Aus diesem Grund empfiehlt diese Arbeit, dass bevor weitere maschinelle Lernver- fahren auf adaptive Streaming-Daten angewendet werden, zuerst die exsistierenden QoE-Modelle und deren Verhalten genauer untersucht werden sollten. Für diese Un- tersuchungen stellt die im Rahmen dieser Arbeit entwickelte Toolchain ein wertvolles Hilfsmittel dar, da sie die schnelle Generierung von Streaming-Daten und deren Be- wertung anhand von sieben verschiedenen QoE-Modellen ermöglicht.
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Borchert, K., Schwind, A., Hirth, M., Hoßfeld, T.: In Vivo or in Vitro? Influence of the Study Design on Crowdsourced Video QoE. 11th International Conference on Quality of Multimedia Experience (QoMEX) (2019).
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Smietanka, O.: Comparison of LPWAN IoT Device Communication Techniques LoRa and NB-IoT, (2019).
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Dewitz, L., Münster, S., Niebling, F.: Usability-Testing für Softwarewerkzeuge in den Digital Humanities am Beispiel von Bildrepositorien. DHd 2019 Digital Humanities: multimedial & multimodal. Konferenzabstracts, Frankfurt am Main. 52-55 (2019).
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Maiwald, F., Henze, F., Bruschke, J., Niebling, F.: GEO-INFORMATION TECHNOLOGIES FOR A MULTIMODAL ACCESS ON HISTORICAL PHOTOGRAPHS AND MAPS FOR RESEARCH AND COMMUNICATION IN URBAN HISTORY. ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. XLII-2/W11, 763--769 (2019).
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Nogatz, F., Kübert, J., Seipel, D., Abreu, S.: Alexa, How Can I Reason with Prolog? Proceedings of 8th Symposium on Languages, Applications, Technologies (SLATE). S. 17:1-17:9 (2019).
As with Amazon’s Echo and its conversational agent Alexa, smart voice-controlled devices become ever more present in daily life, and many different applications can be integrated into this platform. In this paper, we present a framework that eases the development of skills in Prolog. As Prolog has a long history in natural language processing, we may integrate well-established techniques, such as reasoning about knowledge with Attempto Controlled English, instead of depending on example phrases and pre-defined slots.
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Moldovan, C., Wamser, F., Hoßfeld, T.: Energy-Efficient Adaptation Logic for HTTP Streaming in Mobile Networks. 2019 International Conference on Networked Systems (NetSys) (2019).
The requirements for video streaming have changed drastically during the past years. In today's Internet, high definition resolutions are considered default for videos, even in mobile settings, and with 4G penetration reaching 90 percent in the US, this no longer poses a big problem. However, while mobile bandwidth has increased, the battery life time of mobile devices has not increased significantly. Furthermore, current data plans are still not large enough to regularly stream movies during the commute. Users still resort to downloading media before travel. In this paper we propose a new HTTP adaptive streaming algorithm that delivers videos in high quality while avoiding stalling events, schedules the download of video segments so that a energy conserving idle state is often reached and keeps the buffer low at points in the video where many viewers abandon the video to save data. While most adaptive streaming algorithms optimize quality and stalling, this is the first attempt to use an adaptive streaming algorithm to reduce energy consumption. Since video streaming providers mostly care about the Quality of Experience when watching videos, energy efficiency is left to the device manufacturers. Therefore, both parties have little incentive to cooperate in this regard. But on the Internet of tomorrow, where most videos are watched on mobile devices, energy efficiency and the Quality of Experience must go hand in hand.
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Seufert, M.: Quality of Experience and Access Network Traffic Management of HTTP Adaptive Video Streaming. , International Conference on Networked Systems (NetSys), KuVS Dissertation Award 2018, Munich, Germany (2019).
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Lange, S., Linguaglossa, L., Geißler, S., Rossi, D., Zinner, T.: Discrete-Time Modeling of NFV Accelerators that Exploit Batched Processing. IEEE Conference on Computer Communications (Infocom) (2019).
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Schwarzmann, S., Breitbach, P., Zinner, T.: Computing QoE-relevant Adaptive Video Streaming Metrics using Discrete-Time Analysis. Third International Workshop on Quality of Experience Management 2019 (2019).
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Alissa, A., Bentalab, A., Zinner, T., Ghita, B., Mkwawa, I.-H.: BBGDASH: A Max-Min Bounded Bitrate Guidance for SDN Enabled Adaptive Video Streaming. 22nd Conference on Innovation in Clouds, Internet and Networks and Workshops (ICIN (2019).
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Enghardt, T., Zinner, T., Feldmann, A.: Web Performance Pitfalls. Passive and Active Measurement Conference (PAM) (2019).
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Hildebrand, K.: Towards a Source Traffic Model for Instant Messaging using WhatsApp, (2019).
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Kurak, T.: Subjektive Nutzerstudie zur Untersuchung des Einflusses von persönlicher Bekanntheit und Popularität eines Videos auf die QoE, (2019).
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Seufert, M., Casas, P., Wehner, N., Li, G., Kuang, L.: Stream-based Machine Learning for Real-time QoE Analysis of Encrypted Video Streaming Traffic. 3rd International Workshop on Quality of Experience Management (QoE-Management). , Paris, France (2019).
As stalling is the worst Quality of Experience (QoE) degradation of HTTP adaptive video streaming (HAS), this work presents a stream-based machine learning approach, ViCrypt, which analyzes stalling of YouTube streaming sessions in real-time from encrypted network traffic. The video streaming session is subdivided into a stream of short time slots of 1 s length, while considering two additional macro windows each for the current streaming trend and the whole ongoing streaming session. Constant memory features are extracted from the encrypted network traffic in these three windows in a stream-based fashion, and fed into a random forest model, which predicts whether the current time slot contains stalling or not. The presented system can predict stalling with a very high accuracy and the finest granularity to date (1 s), and thus, can be used in networks for real-time QoE analysis from encrypted YouTube video streaming traffic. The independent predictions for each consecutive slot of a streaming session can further be aggregated to obtain stalling estimations for the whole session. Thereby, the proposed method allows to quantify the initial delay, as well as the overall number of stalling events and the stalling ratio, i.e., the ratio of total stalling time and total playback time.
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Steinhaeusser, S.C., Riedmann, A., Haller, M., Oberdörfer, S., Bucher, K., Latoschik, M.E.: Fancy Fruits - An Augmented Reality Application for Special Needs Education. Proceedings of the 11th International Conference on Virtual Worlds and Games for Serious Applications (VS Games 2019). S. 1-4. IEEE (2019).
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Hoßfeld, T., Atzori, L., Heegaard, P.E., Skorin-Kapov, L., Varela, M.: The Interplay between QoE, User Behavior and System Blocking in QoE Management. 22nd Conference on Innovation in Clouds, Internet and Networks and Workshops (ICIN) (2019).
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Seufert, M., Wassermann, S., Casas, P.: Considering User Behavior in the Quality of Experience Cycle: Towards Proactive QoE-aware Traffic Management. IEEE Communications Letters. 23, 1145-1148 (2019).
The concept of Quality of Experience (QoE) of Internet services is widely recognized by service providers and network operators. They strive to deliver the best experience to their customers in order to increase revenues and avoid churn. Therefore, QoE is increasingly considered as an integral part of the reactive traffic management cycle of network operators. Additionally, QoE also constitutes a cycle of its own, which includes the user behavior and the service requirements. This work describes this QoE cycle, which is not widely taken into account yet, discusses the interactions of the two cycles, and derives implications towards an improved and proactive QoE-aware traffic management. A showcase on how network operators can obtain hints on the change of network requirements from detecting user behavior in encrypted video traffic is also presented in this paper.
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Aschenbrenner, D., Leutert, F., Cencen, A., Verlinden, J., Schilling, K., Latoschik, M.E., Lukosch, S.: Comparing Human Factors for Augmented Reality supported Single and Cooperative Repair Operations of Industrial Robots. Frontiers in Robotics and AI. 6, 37 (2019).
In order to support the decision-making process of industry on how to implement Augmented Reality (AR) in production, this article wants to provide guidance through a set of comparative user studies. The results are obtained from the feedback of 160 participants who performed the same repair task on a switch cabinet of an industrial robot. The studies compare several AR instruction applications on different display devices (head-mounted display, handheld tablet PC and projection-based spatial AR) with baseline conditions (paper instructions and phone support), both in a single-user and a collaborative setting. Next to insights on the performance of the individual device types for the single mode operation, the study is able to show significant indications on AR techniques are being especially helpful in a collaborative setting.
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Morell, M.: Traffic Measurement Study for Real-Time Video Streaming with a Remote Controllable Drone, (2019).
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Wolz, M.: Hit Detection with Asymmetric Latency in UE4 Authoritative Multiplayer Games, (2019).
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Ewald, M.: Observing Changes in Machine Learning Behavior from Input Latency in Games, (2019).
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Stulier, N.: Viability of VNF Offloading in P4, (2019).
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Rosenberger, A.: Using In-Band Network Telemetry for Automatic QoS Optimization in SDNs, (2019).
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Grigorjew, A., Metzger, F., Hoßfeld, T., Specht, J.: A Simulation of Asynchronous Traffic Shapers in Switched Ethernet Networks. Workshop for Advanced Communication Networks for Industrial Applications (2019).
As the requirements of real-time networking in- crease, the IEEE Time-Sensitive Networking (TSN) task group is working on new standards for high bandwidth and low latency Ethernet switching. In particular, the upcoming P802.1Qcr standard features Asynchronous Traffic Shaping (ATS), which is a promising approach for real-time networks with high dynamics and critical safety requirements. Additionally, parallel concepts such as frame preemption can be used to reduce delays even further. This work presents a discrete event simulation framework that can analyze the performance of these concepts. It implements frame preemption and multiple shaping algorithms, while recording latency and queue utilization statistics at the switches. In addition, an evaluation of a linear topology with four switches is performed under high link utilization, which demonstrates the benefit of the above mechanisms compared to regular Ethernet switching.
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Haberzettl, L.: QoS Assessments of Spotify’s Mobile Application for Audio Streaming, (2019).
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Firman, O., Kindermann, P., Ravsky, A., Wolff, A., Zink, J.: Computing Optimal Tangles Faster. In: Löffler, M. (hrsg.) Proc. 35th European Workshop on Computational Geometry (EuroCG'19). S. 61:1--7 (2019).
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Sanderson, P.M., Brecknell, B., Leong, S.Y., Klueber, S., Wolf, E., Hickling, A., Tang, T.-L., Bell, E., Li, S.Y.W., Loeb, R.G.: Monitoring vital signs with time-compressed speech. Journal of Experimental Psychology: Applied. (2019).
Spearcons—time-compressed speech phrases—may be an effective way of communicating vital signs to clinicians without disturbing patients and their families. Four experiments tested the effectiveness of spearcons for conveying oxygen saturation (SpO2) and heart rate (HR) of one or more patients. Experiment 1 demonstrated that spearcons were more effective than earcons (abstract auditory motifs) at conveying clinical ranges. Experiment 2 demonstrated that casual listeners could not learn to decipher the spearcons whereas listeners told the exact vocabulary could. Experiment 3 demonstrated that participants could interpret sequences of sounds representing multiple patients better with spearcons than with pitch-based earcons, especially when tones replaced the spearcons for normal patients. Experiment 4 compared multiple-patient monitoring of two vital signs with either spearcons, a visual display showing SpO2 and HR in the same temporal sequence as the spearcons, or a visual display showing multiple patient levels simultaneously. All displays conveyed which patients were abnormal with high accuracy. Visual displays better conveyed the vital sign levels for each patient, but cannot be used eyes-free. All displays showed accuracy decrements with working memory load. Spearcons may be viable for single and multiple patient monitoring. Further research should test spearcons with more vital signs, during multitasking, and longitudinally.
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Wassermann, S., Seufert, M., Casas, P., Li, G., Kuang, L.: I See What you See: Real Time Prediction of Video Quality from Encrypted Streaming Traffic. 4th Workshop on QoE-based Analysis and Management of Data Communication Networks (Internet-QoE). , Los Cabos, Mexico (2019).
We address the problem of real-time QoE monitoring of HAS, from the ISP perspective, focusing in particular on videoresolution analysis. Given the wide adoption of end-to-end encryption, we resort to machine-learning models to predict different video resolution levels in a fine-grained scale, ranging from 144p to 1080p resolution, using as input only packet-level data. The proposed measurement system performs predictions in real time, during the course of an ongoing video-streaming session, with a time granularity as small as one second. We consider the particular case of YouTube video streaming. Empirical evaluations on a large and heterogeneous corpus of YouTube measurements demonstrate that the proposed system can predict video resolution with very high accuracy, and in real time. Different from state of the art, the prediction task is not bound to coarse-grained video quality classes and does not require chunk-detection approaches for feature extraction.
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Wassermann, S., Seufert, M., Casas, P., Li, G., Kuang, L.: ViCrypt: Real-time, Fine-grained Prediction of Video Quality from Encrypted Streaming Traffic, (2019).
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Wunderlich, S., Ring, M., Landes, D., Hotho, A.: Comparison of System Call Representations for Intrusion Detection. In: Martínez-Álvarez, F., Lora, A.T., Muñoz, J.A.S., Quintián, H., und Corchado, E. (hrsg.) CISIS-ICEUTE. S. 14-24. Springer (2019).
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Niebling, F., Haas, M., Blessing, A.´: Integration of Services for Software Development in DH: A Case Study of Image Classification using Convolutional Neural Networks. In: Draude, C., Lange, M., und Sick, B. (hrsg.) INFORMATIK 2019: 50 Jahre Gesellschaft für Informatik – Informatik für Gesellschaft (Workshop-Beiträge). S. 163-168. Gesellschaft für Informatik e.V., Bonn (2019).
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Glémarec, Y., Bosser, A.-G., Lugrin, J.-L., Chollet, M., Buche, C., Landeck, M., Latoschik, M.E.: A Scalability Benchmark for a Virtual Audience Perception Model in Virtual Reality. Proceedings of the 25th ACM Conference on Virtual Reality Software and Technology (2019).
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Lugrin, J.-L., Unruh, F., Landeck, M., Lamour, Y., Latoschik, M.E., Vogeley, K., Wittmann, M.: Experiencing Waiting Time in Virtual Reality. Proceedings of the 25th ACM Conference on Virtual Reality Software and Technology (2019).
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Wassermann, S., Wehner, N., Casas, P.: Machine Learning Models for YouTube QoE and User Engagement Prediction in Smartphones. ACM SIGMETRICS Performance Evaluation Review. 46, 155-158 (2019).
Measuring and monitoring YouTube Quality of Experience is a challenging task, especially when dealing with cellular networks and smartphone users. Using a large-scale database of crowdsourced YouTube-QoE measurements in smartphones, we conceive multiple machine-learning models to infer different YouTube-QoE-relevant metrics and userbehavior- related metrics from network-level measurements, without requiring root access to the smartphone, video-player embedding, or any other reverse-engineering-like approaches. The dataset includes measurements from more than 360 users worldwide, spanning over the last five years. Our preliminary results suggest that QoE-based monitoring of YouTube mobile can be realized through machine learning models with high accuracy, relying only on network-related features and without accessing any higher-layer metric to perform the estimations.
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Dewitz, L., Kröber, C., Messemer, H., Maiwald, F., Münster, S., Bruschke, J., Niebling, F.: HISTORICAL PHOTOS AND VISUALIZATIONS: POTENTIAL FOR RESEARCH. ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. XLII-2/W15, 405--412 (2019).
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Okamoto, Y., Ravsky, A., Wolff, A.: Variants of the Segment Number of a Graph. In: Archambault, D. und Tóth, C.D. (hrsg.) Proc. 27th Int. Symp. Graph Drawing & Network Vis. (GD'19). Springer-Verlag (2019).
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Koopmann, T., Dallmann, A., Hettinger, L., Niebler, T., Hotho, A.: On the Right Track! Analysing and Predicting Navigation Success in Wikipedia. In: Atzenbeck, C., Rubart, J., und Millard, D.E. (hrsg.) Proceedings of the 30th ACM Conference on Hypertext and Social Media. S. 143--152. ACM, Hof, Germany (2019).
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Biedl, T., Felsner, S., Meijer, H., Wolff, A.: Line and Plane Cover Numbers Revisited. In: Archambault, D. und Tóth, C.D. (hrsg.) Proc. 27th Int. Symp. Graph Drawing & Network Vis. (GD'19). Springer-Verlag (2019).
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Geissler, S., Herrnleben, S., Bauer, R., Grigorjew, A., Jarschel, M., Zinner, T.: The Power of Composition: Abstracting a Multi-Device SDN Data Path Through a Single API. IEEE Transactions on Network and Service Management. (2019).
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Kindermann, P., Mchedlidze, T., Schneck, T., Symvonis, A.: Drawing Planar Graphs with Few Segments on a Polynomial Grid. In: Archambault, D. und Tóth, C.D. (hrsg.) Proceedings of the 27th International Symposium on Graph Drawing and Network Visualization (GD'19). Springer-Verlag (2019).
The visual complexity of a graph drawing can be measured by the number of geometric objects used for the representation of its elements. In this paper, we study planar graph drawings where edges are represented by few segments. In such a drawing, one segment may represent multiple edges forming a path. Drawings of planar graphs with few segments were intensively studied in the past years. However, the area requirements were only considered for limited subclasses of planar graphs. In this paper, we show that trees have drawings with 3n/4-1 segments and n^2 area, improving the previous result of O(n^3.58). We also show that 3-connected planar graphs and biconnected outerplanar graphs have a drawing with 8n/3-O(1) and 3n/2-O(1) segments, respectively, and O(n^3) area.
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Kindermann, P., Kobourov, S., Löffler, M., Nöllenburg, M., Schulz, A., Vogtenhuber, B.: Lombardi Drawings of Knots and Links. Journal of Computational Geometry. (2019).
Knot and link diagrams are projections of one or more 3-dimensional simple closed curves into \($R^2$\), such that no more than two points project to the same point in \($R^2$\). These diagrams are drawings of 4-regular plane multigraphs. Knots are typically smooth curves in \($R^3$\), so their projections should be smooth curves in \($R^2$\) with good continuity and large crossing angles: exactly the properties of Lombardi graph drawings (defined by circular-arc edges and perfect angular resolution). We show that several knots do not allow Lombardi drawings. On the other hand, we identify a large class of 4-regular plane multigraphs that do have Lombardi drawings. We then study two relaxations of Lombardi drawings and show that every knot admits a plane 2-Lombardi drawing (where edges are composed of two circular arcs). Further, every knot is emphnear-Lombardi, that is, it can be drawn as Lombardi drawing when relaxing the angular resolution requirement by an arbitrary small angular offset \($\eps$\), while maintaining a \($180^\circ$\) angle between opposite edges.
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Firman, O., Kindermann, P., Ravsky, A., Wolff, A., Zink, J.: Computing Height-Optimal Tangles Faster. In: Archambault, D. und Tóth, C.D. (hrsg.) Proceedings of the 27th International Symposium on Graph Drawing and Network Visualization (GD'19). Springer-Verlag (2019).
We study the following combinatorial problem. Given a set of n y-monotone wires, a tangle determines the order of the wires on a number of horizontal layers such that the orders of the wires on any two consecutive layers differ only in swaps of neighboring wires. Given a multiset L of swaps (that is, unordered pairs of numbers between 1 and n) and an initial order of the wires, a tangle realizes L if each pair of wires changes its order exactly as many times as specified by L. The aim is to find a tangle that realizes L using the smallest number of layers. We show that this problem is NP-hard, and we give an algorithm that computes an optimal tangle for n wires and a given list L of swaps in O((2|L|/n^2+1)^(n^2/2)phi^n n) time, where phi~1.618 is the golden ratio. We can treat lists where every swap occurs at most once in O(n! phi^n) time. We implemented the algorithm for the general case and compared it to an existing algorithm.
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Firman, O., Kindermann, P., Ravsky, A., Wolff, A., Zink, J.: Computing Optimal Tangles Faster. In: Cheng, S.-W. (hrsg.) Proceedings of the 12th Annual Meeting of the Asian Association for Algorithms and Computation (AAAC'19). Seoul (2019).
We study the following combinatorial problem. Given a set of n y-monotone wires, a tangle determines the order of the wires on a number of horizontal layers such that the orders of the wires on any two consecutive layers differ only in swaps of neighboring wires. Given a multiset L of swaps (that is, unordered pairs of numbers between 1 and n) and an initial order of the wires, a tangle realizes L if each pair of wires changes its order exactly as many times as specified by L. The aim is to find a tangle that realizes L using the smallest number of layers. We show that this problem is NP-hard, and we give an algorithm that computes an optimal tangle for n wires and a given list L of swaps in O((2|L|/n^2+1)^(n^2/2)phi^n n) time, where phi~1.618 is the golden ratio. We can treat lists where every swap occurs at most once in O(n! phi^n) time. We implemented the algorithm for the general case and compared it to an existing algorithm.
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Chaplick, S., van Dijk, T.C., Kryven, M., Park, J.-W., Ravsky, A., Wolff, A.: Bundled Crossings Revisited. In: Archambault, D. und Tóth, C.D. (hrsg.) Proc. 27th Int. Symp. Graph Drawing & Network Vis. (GD'19). Springer-Verlag (2019).
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Lugrin, J.-L., Juchno, A., Schaper, P., Landeck, M., Latoschik, M.E.: Drone-Steering: A Novel VR Traveling Technique. In: of the 25th ACM Conference on Virtual Reality Software, P. und Technology, (hrsg.) Proceedings of the 25th ACM Conference on Virtual Reality Software and Technology (2019).
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Roth, D., Bente, G., Kullmann, P., Mal, D., Purps, C.F., Vogeley, K., Latoschik, M.E.: Technologies for Social Augmentations in User-Embodied Virtual Reality. 25th ACM Symposium on Virtual Reality Software and Technology (VRST). S. 1-12 (2019).
Technologies for Virtual, Mixed, and Augmented Reality (VR, MR, and AR) allow to artificially augment social interactions and thus to go beyond what is possible in real life. Motivations for the use of social augmentations are manifold, for example, to synthesize behavior when sensory input is missing, to provide additional affordances in shared environments, or to support inclusion and training of individuals with social communication disorders. We review and categorize augmentation approaches and propose a software architecture based on four data layers. Three components further handle the status analysis, the modification, and the blending of behaviors. We present a prototype (injectX) that supports behavior tracking (body motion, eye gaze, and facial expressions from the lower face), status analysis, decision-making, augmentation, and behavior blending in immersive interactions. Along with a critical reflection, we consider further technical and ethical aspects.
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Wolf, E., Heinrich, R., Michalek, A., Schraudt, D., Hohm, A., Hein, R., Grundgeiger, T., Happel, O.: Rapid Preparation of Eye Tracking Data For Debriefing In Medical Training: A Feasibility Study. Proceedings of the Human Factors and Ergonomics Society Annual Meeting. 63, 733--737 (2019).
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Hettinger, L., Zehe, A., Dallmann, A., Hotho, A.: EClaiRE: Context Matters! – Comparing Word Embeddings for Relation Classification. In: David, K., Geihs, K., Lange, M., und Stumme, G. (hrsg.) INFORMATIK 2019: 50 Jahre Gesellschaft für Informatik – Informatik für Gesellschaft. S. 191-204. Gesellschaft für Informatik e.V., Bonn (2019).
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Wankerl, S., Götz, G., Hotho, A.: Solving Mathematical Exercises: Prediction of Students’ Success. In: Jäschke, R. und Weidlich, M. (hrsg.) LWDA. S. 190-194. CEUR-WS.org (2019).
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Firman, O., Kindermann, P., Ravsky, A., Wolff, A., Zink, J.: Computing Optimal-Height Tangles Faster. In: Archambault, D. und Tóth, C.D. (hrsg.) Proc. 27th Int. Symp. Graph Drawing & Network Vis. (GD'19). Springer-Verlag (2019).
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Eckstein, B., Niebling, F., Lugrin, B.: Reflected Reality: A Mixed Reality Knowledge Representation for Context-aware Systems. 11th International Conference on Virtual Worlds and Games for Serious Applications (VS-Games). S. 1-4. IEEE (2019).
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Supervisor: Wehner, N.: Comparison of Web QoE Algorithms on Different Devices, (2019).
Contact/Kontakt: nikolas.wehner@informatik.uni-wuerzburg.de Impairments in the Web QoE, e.g., low page load times, can lead to annoyed users which in the end can result in revenue losses for companies. In literature, several algorithm exist for predicting the Web QoE, e.g. Speed Index, Above the Fold, etc. Based on data from a measurement study, these algorithms shall be evaluated and compared in this work. In particular, a comparison of the metrics among the devices (Smartphone, Tablet, Desktop PC), which were used to generate the measurement data, is of interest.
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Schwind, A., Haberzettl, L., Wamser, F., Hoßfeld, T.: QoE Analysis of Spotify Audio Streaming and App Browsing. 4th Internet-QoE Workshop: QoE-based Analysis and Management of Data Communication Networks (Internet-QoE'19) (2019).
Spotify is the most-listened audio streaming provider in 2019 with 217 million active users per month. Providers are therefore interested in the quality and functionality of Spotify in order to provide their users with the best possible streaming quality. While video streaming services such as Netflix and their streaming approach have been extensively explored in previous research, audio streaming services like Spotify and their corresponding behavior at certain network conditions have not been considered in detail yet. In this paper, we perform a QoE analysis under various network conditions and examine the app browsing performance of the audio streaming platform Spotify using its native Android mobile application. We have developed a measurement tool that emulates a user listening to audio through Spotify. While streaming, application and network layer parameters are captured that have a high correlation to the user’s QoE. The paper shows a baseline scenario including the streaming of a single song as well as playlist streaming behavior. Next, the effect of interruptions on the streaming behavior is evaluated and finally, the influence of network impairments on QoE key performance indicators such as initial delay is shown.
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Niebling, F.: Visualizing Orientations of Large Numbers of Photographs. Proceedings of the 1st Workshop on Structuring and Understanding of Multimedia heritAge Contents. S. 1--2. ACM, Nice, France (2019).
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Zehe, A., Hettinger, L., Ernst, S., Hauptmann, C., Hotho, A.: Team Xenophilius Lovegood at SemEval-2019 Task 4: Hyperpartisanship Classification using Convolutional Neural Networks. Proceedings of The 13th International Workshop on Semantic Evaluation. Association for Computational Linguistics (2019).
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Ring, M., Wunderlich, S., Scheuring, D., Landes, D., Hotho, A.: A Survey of Network-based Intrusion Detection Data Sets. Computers & Security. 86, 147-167 (2019).
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Lammers, S., Bente, G., Tepest, R., Jording, M., Roth, D., Vogeley, K.: Introducing ACASS: An Annotated Character Animation Stimulus Set for Controlled (e)Motion Perception Studies. Frontiers in Robotics and AI. 6, 94 (2019).
Others' movements inform us about their current activities as well as their intentions and emotions. Research on the distinct mechanisms underlying action recognition and emotion inferences has been limited due to a lack of suitable comparative stimulus material. Problematic confounds can derive from low-level physical features (e.g., luminance), as well as from higher-level psychological features (e.g., stimulus difficulty). Here we present a standardized stimulus dataset, which allows to address both action and emotion recognition with identical stimuli. The stimulus set consists of 792 computer animations with a neutral avatar based on full body motion capture protocols. Motion capture was performed on 22 human volunteers, instructed to perform six everyday activities (mopping, sweeping, painting with a roller, painting with a brush, wiping, sanding) in three different moods (angry, happy, sad). Five-second clips of each motion protocol were rendered into AVI-files using two virtual camera perspectives for each clip. In contrast to video stimuli, the computer animations allowed to standardize the physical appearance of the avatar and to control lighting and coloring conditions, thus reducing the stimulus variation to mere movement. To control for low level optical features of the stimuli, we developed and applied a set of MATLAB routines extracting basic physical features of the stimuli, including average background-foreground proportion and frame-by-frame pixel change dynamics. This information was used to identify outliers and to homogenize the stimuli across action and emotion categories. This led to a smaller stimulus subset (n = 83 animations within the 792 clip database) which only contained two different actions (mopping, sweeping) and two different moods (angry, happy). To further homogenize this stimulus subset with regard to psychological criteria we conducted an online observer study (N = 112 participants) to assess the recognition rates for actions and moods, which led to a final sub-selection of 32 clips (eight per category) within the database. The ACASS database and its subsets provide unique opportunities for research applications in social psychology, social neuroscience, and applied clinical studies on communication disorders. All 792 AVI-files, selected subsets, MATLAB code, annotations, and motion capture data (FBX-files) are available online.
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Chaplick, S., Kindermann, P., Löffler, A., Thiele, F., Wolff, A., Zaft, A., Zink, J.: Stick Graphs with Length Constraints. In: Archambault, D. und Tóth, C.D. (hrsg.) Proceedings of the 27th International Symposium on Graph Drawing and Network Visualization (GD'19). Springer-Verlag (2019).
Stick graphs are intersection graphs of horizontal and vertical line segments that all touch a line of slope -1 and lie above this line. De Luca et al. [GD’18] considered the recognition problem of stick graphs when no order is given (STICK), when the order of either one of the two sets is given (STICK_A), and when the order of both sets is given (STICK_AB). They showed how to solve STICK_AB efficiently. In this paper, we improve the running time of their algorithm, and we solve STICK_A efficiently. Further, we consider variants of these problems where the lengths of the sticks are given as input. We show that these variants of STICK, STICK_A , and STICK_AB are all NP-complete. On the positive side, we give an efficient solution for STICK_AB with fixed stick lengths if there are no isolated vertices.
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Biedl, T., Biniaz, A., Irvine, V., Jain, K., Kindermann, P., Lubiw, A.: Maximum Matchings and Minimum Blocking Sets in \($\Theta_6$\)-Graphs. In: Sau, I. und Thilikos, D.M. (hrsg.) Proceedings of the 45th International Workshop on Graph-Theoretic Concepts in Computer Science (WG'19). S. 258--270. Springer-Verlag (2019).
Theta_6-graphs are important geometric graphs that have many applications. They are equivalent to Delaunay graphs where empty equilateral triangles with a horizontal edge take the place of empty circles. We investigate lower bounds on the size of maximum matchings in these graphs. The best known lower bound is (n-1)/3, where n is the number of vertices of the graph. Babu et al. (2014) conjectured that any Theta_6-graph has a perfect matching (as is true for standard Delaunay graphs). Although this conjecture remains open, we improve the lower bound to (3n-8)/7. We also relate the size of maximum matchings in Theta_6-graphs to the minimum size of a blocking set. Every edge of a Theta_6-graph on a point set P corresponds to an empty triangle that contains the endpoints of the edge but no other point of P. A blocking set has at least one point in each such triangle. We prove that the size of a maximum matching is at least b(n)/2 where b(n) is the minimum, over all Theta_6-graphs with n vertices, of the minimum size of a blocking set. In the other direction, lower bounds on matchings allow us to show that b(n) >= 3n/4 - 2.
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Chimani, M., Kindermann, P., Montecchiani, F., Valtr, P.: Crossing Numbers of Beyond-Planar Graphs. In: Archambault, D. und Tóth, C.D. (hrsg.) Proceedings of the 27th International Symposium on Graph Drawing and Network Visualization (GD'19). Springer-Verlag (2019).
We study lower bounds on the minimum number of crossings for 1-planar, quasi-planar, and fan-planar graphs. We prove that there are n-vertex 1-planar (quasi-planar, fan-planar) graphs such that any 1-planar (quasi-planar, fan-planar) drawing has Omega(n) crossings, while O(1) crossings suffice in a crossing-minimal drawing with no restrictions on local edge crossing patterns.
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Biedl, T., Kindermann, P.: Finding Tutte Paths in Linear Time. In: Baier, C., Chatzigiannakis, I., Flocchini, P., und Leonardi, S. (hrsg.) Proceedings of the 46th International Colloquium on Automata, Languages, and Programming (ICALP'19). S. 23:1--23:14. Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik (2019).
It is well-known that every planar graph has a Tutte path, i.e., a path P such that any component of G-P has at most three attachment points on P. However, it was only recently shown that such Tutte paths can be found in polynomial time. In this paper, we give a new proof that 3-connected planar graphs have Tutte paths, which leads to a linear-time algorithm to find Tutte paths. Furthermore, our Tutte path has special properties: it visits all exterior vertices, all components of G-P have exactly three attachment points, and we can assign distinct representatives to them that are interior vertices. Finally, our running time bound is slightly stronger; we can bound it in terms of the degrees of the faces that are incident to P. This allows us to find some applications of Tutte paths (such as binary spanning trees and 2-walks) in linear time as well.
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Firman, O., Kindermann, P., Ravsky, A., Wolff, A., Zink, J.: Computing Optimal Tangles Faster. In: Löffler, M. (hrsg.) Proceedings of the 35th European Workshop on Computational Geometry (EuroCG'19). Utrecht (2019).
We study the following combinatorial problem. Given a set of n y-monotone wires, a tangle determines the order of the wires on a number of horizontal layers such that the orders of the wires on any two consecutive layers differ only in swaps of neighboring wires. Given a multiset L of swaps (that is, unordered pairs of numbers between 1 and n) and an initial order of the wires, a tangle realizes L if each pair of wires changes its order exactly as many times as specified by L. The aim is to find a tangle that realizes L using the smallest number of layers. We show that this problem is NP-hard, and we give an algorithm that computes an optimal tangle for n wires and a given list L of swaps in O((2|L|/n^2+1)^(n^2/2)phi^n n) time, where phi~1.618 is the golden ratio. We can treat lists where every swap occurs at most once in O(n! phi^n) time. We implemented the algorithm for the general case and compared it to an existing algorithm.
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Angelini, P., Bekos, M., Didimo, W., Grilli, L., Kindermann, P., Mchedlidze, T., Prutkin, R., Symvonis, A., Tappini, A.: Greedy Rectilinear Drawings. Theoretical Computer Science. (2019).
A drawing of a graph is greedy if for each ordered pair of vertices \($u$\) and \($v$\), there is a path from \($u$\) to \($v$\) such that the Euclidean distance to \($v$\) decreases monotonically at every vertex of the path. The existence of greedy drawings has been widely studied under different topological and geometric constraints, such as planarity, face convexity, and drawing succinctness. We introduce greedy rectilinear drawings, in which each edge is either a horizontal or a vertical segment. These drawings have several properties that improve human readability and support network routing. We address the problem of testing whether a planar rectilinear representation, i.e., a plane graph with specified vertex angles, admits vertex coordinates that define a greedy drawing. We provide a characterization, a linear-time testing algorithm, and a full generative scheme for universal greedy rectilinear representations, i.e., those for which every drawing is greedy. For general greedy rectilinear representations, we give a combinatorial characterization and, based on it, a polynomial-time testing and drawing algorithm for a meaningful subset of instances.
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Biedl, T., Biniaz, A., Irvine, V., Jain, K., Kindermann, P., Lubiw, A.: Maximum Matchings and Minimum Blocking Sets in \($\Theta_6$\)-Graphs. In: Löffler, M. (hrsg.) Proceedings of the 35th European Workshop on Computational Geometry (EuroCG'19). Utrecht (2019).
Theta_6-graphs are important geometric graphs that have many applications. They are equivalent to Delaunay graphs where empty equilateral triangles with a horizontal edge take the place of empty circles. We investigate lower bounds on the size of maximum matchings in these graphs. The best known lower bound is (n-1)/3, where n is the number of vertices of the graph. Babu et al. (2014) conjectured that any Theta_6-graph has a perfect matching (as is true for standard Delaunay graphs). Although this conjecture remains open, we improve the lower bound to (3n-8)/7. We also relate the size of maximum matchings in Theta_6-graphs to the minimum size of a blocking set. Every edge of a Theta_6-graph on a point set P corresponds to an empty triangle that contains the endpoints of the edge but no other point of P. A blocking set has at least one point in each such triangle. We prove that the size of a maximum matching is at least b(n)/2 where b(n) is the minimum, over all Theta_6-graphs with n vertices, of the minimum size of a blocking set. In the other direction, lower bounds on matchings allow us to show that b(n) >= 3n/4 - 2.
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Kindermann, P., Mchedlidze, T., Rutter, I.: Graph Drawing Contest Report. In: Archambault, D. und Tóth, C.D. (hrsg.) Proceedings of the 27th International Symposium on Graph Drawing and Network Visualization (GD'19). Springer-Verlag (2019).
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Geißler, S., Lange, S., Wamser, F., Zinner, T., Hoßfeld, T.: KOMon - Kernel-based Online Monitoring of VNF Packet Processing Times. 2019 International Conference on Networked Systems (NetSys), Best Paper Award (2019).
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Klueber, S., Wolf, E., Grundgeiger, T., Brecknell, B., Mohamed, I., Sanderson, P.M.: Head-Worn Displays and Spearcons: Supporting Multiple Patient Monitoring. Applied Ergonomics. 78, 86-96 (2019).
In hospitals, clinicians often need to monitor several patients while performing other tasks. However, visual displays that show patientsu0027 vital signs are in fixed locations and auditory alarms intended to alert clinicians may be missed. Information such as spearcons (time-compressed speech earcons) that ‘travels’ with the clinician and is delivered by earpiece and/or head-worn displays (HWDs), might overcome these problems. In this study, non-clinicians monitored five simulated patients in three 10-min scenarios while performing a demanding tracking task. Monitoring accuracy was better for participants using spearcons and a HWD (88.7%) or a HWD alone (86.2%) than for participants using spearcons alone (74.1%). Participants using the spearcons and HWD (37.7%) performed the tracking task no differently from participants using spearcons alone (37.1%) but participants using the HWD alone performed worse overall (33.1%). The combination of both displays may be a suitable solution for monitoring multiple patients.
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Wassermann, S., Seufert, M., Casas, P., Li, G., Kuang, L.: Let me Decrypt your Beauty: Real-time Prediction of Video Resolution and Bitrate for Encrypted Video Streaming, (2019).
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Evans, W., Rzka.zewski, P., Saeedi, N., Shin, C.-S., Wolff, A.: Representing Graphs and Hypergraphs by Touching Polygons in 3D. In: Archambault, D. und Tóth, C.D. (hrsg.) Proc. 27th Int. Symp. Graph Drawing & Network Vis. (GD'19). Springer-Verlag (2019).
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Rosenberger, A.: Konstruktion eines RIOT-LoRaWAN-Sensorknotens, (2019).
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Stulier, N.: Statistische Evaluation der APM in DOTA 2, (2019).
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Hirth, M., Steurer, F., Borchert, K., Dubiner, D.: Task Scheduling on Crowdsourcing Platforms for Enabling Completion Time SLAs. 31st International Teletraffic Congress (ITC). , Budapest, Hungary (2019).
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Striepe, H., Donnermann, M., Lein, M., Lugrin, B.: Modeling and Evaluating Emotion, Contextual Head Movement and Voices for a Social Robot Storyteller. International Journal of Social Robotics. (2019).
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Geiger, A., Bente, G., Lammers, S., Tepest, R., Roth, D., Bzdok, D., Vogeley, K.: Distinct functional roles of the mirror neuron system and the mentalizing system. NeuroImage. 202, 116102 (2019).
Movements can inform us about what people are doing and also about how they feel. This phenomenologically evident distinction has been suggested to correspond functionally with differential neural correlates denoted as mirror neuron system (MNS) and mentalizing system (MENT). To separate out the roles of the underlying systems we presented identical stimuli under different task demands: character animations showing everyday activities (mopping, sweeping) performed in different moods (angry, happy). Thirty-two participants were undergoing functional magnetic resonance imaging (fMRI) while asked to identify either the performed movement or the displayed mood. Univariate GLM analysis revealed the expected activation of either in MNS or MENT depending on the task. A complementary multivariate pattern-learning analysis based on the “social brain atlas” confirmed the expected recruitment of both systems. In conclusion, both approaches converge onto clearly distinct functional roles of both social neural networks in a novel dynamic social perception paradigm.
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Janiak, T.: Investigating the Influence of Listener Attentiveness on the QoE of Music Streaming, (2019).
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Korger, A., Baumeister, J.: Case-Based Retrieval and Adaptation of Regulatory Documents and their Context. Proceedings of LWDA - Lernen. Wissen. Daten. Analysen 2019. S. 292-303. , Humboldt-Universität zu Berlin (2019).
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Chaplick, S., Förster, H., Kryven, M., Wolff, A.: On Arrangements of Orthogonal Circles. In: Archambault, D. und Tóth, C.D. (hrsg.) Proc. 27th Int. Symp. Graph Drawing & Network Vis. (GD'19). Springer-Verlag (2019).
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Janiak, L.: Analysis of Geographic Data in R, (2019).
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Chaplick, S., van Dijk, T.C., Kryven, M., Park, J.-W., Ravsky, A., Wolff, A.: Bundled Crossings Revisited. In: Löffler, M. (hrsg.) Proc. 35th European Workshop on Computational Geometry (EuroCG'19). S. 57:1--7 (2019).
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Chaplick, S., Kindermann, P., Löffler, A., Thiele, F., Wolff, A., Zaft, A., Zink, J.: Stick Graphs with Length Constraints. In: Archambault, D. und Tóth, C.D. (hrsg.) Proc. 27th Int. Symp. Graph Drawing & Network Vis. (GD'19). Springer-Verlag (2019).
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Chaplick, S., Lipp, F., Wolff, A., Zink, J.: Compact Drawings of 1-Planar Graphs with Right-Angle Crossings and Few Bends. Computational Geometry: Theory and Applications. 84, 50--68 (2019).
We study the following classes of beyond-planar graphs: 1-planar, IC-planar, and NIC-planar graphs. These are the graphs that admit a 1-planar, IC-planar, and NIC-planar drawing, respectively. A drawing of a graph is emph1-planar if every edge is crossed at most once. A 1-planar drawing is emphIC-planar if no two pairs of crossing edges share a vertex. A 1-planar drawing is emphNIC-planar if no two pairs of crossing edges share two vertices. We study the relations of these beyond-planar graph classes (\emphbeyond-planar graphs is a collective term for the primary attempts to generalize the planar graphs) to emphright-angle crossing (\emphRAC) graphs that admit compact drawings on the grid with few bends. We present four drawing algorithms that preserve the given embeddings. First, we show that every \($n$\)-vertex NIC-planar graph admits a NIC-planar RAC drawing with at most one bend per edge on a grid of size \($O(n) times O(n)$\). Then, we show that every \($n$\)-vertex 1-planar graph admits a 1-planar RAC drawing with at most two bends per edge on a grid of size \($O(n^3) times O(n^3)$\). Finally, we make two known algorithms embedding-preserving; for drawing 1-planar RAC graphs with at most one bend per edge and for drawing IC-planar RAC graphs straight-line.
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Leidinger, F.: Studing the Initial Delay of the YouTube Mobile App with TensorFlow, (2019).
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Simonovski, F.: Studying the Video Segmentation for different Streaming Platforms, (2019).
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Loh, F., Vomhoff, V., Wamser, F., Metzger, F., Hoßfeld, T.: Traffic Measurement Study on Video Streaming with the Amazon Echo Show. 4th Internet-QoE Workshop: QoE-based Analysis and Management of Data Communication Networks (2019).
The Amazon Echo Show is one of the most widely used smart speakers with the ability to stream video. Due to its popularity, the traffc profiles of such devices are of interest to network operators and providers. This work presents a measurement study of the Amazon Echo Show in terms of network traffc and streaming behavior. More than 470 hours of streaming data are collected and analyzed at network layer. Based on this, streaming quality is derived at application layer. The study quantifies the traffc and shows that streaming with the Amazon Echo Show is comparable to streaming with a native web browser, but in a more conservative way.
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Loh, F., Wamser, F., Moldovan, C., Zeidler, B., Hoßfeld, T., Tsilimantos, D., Valentin, S.: From click to playback: a dataset to study the response time of mobile YouTube. Proceedings of the 10th ACM Multimedia Systems Conference. S. 267-272 (2019).
Responding fluently to user requests is important to keep them immersed. In this paper, we are presenting an extensive dataset to study the response time of YouTube's mobile video streaming service on Android. We illustrate the application of our dataset by studying YouTube's initial delay for a subset of 9 videos in 75 network scenarios. We find that in 41% of the cases, YouTube exceeds the attention span of a typical user, while deep immersion is only reached in 15% of the cases. Our factor analysis implies that the allocation of the initial CDN node is the critical link in this delay chain. Since our dataset includes a large variety of factors, we are describing setup, methodology, and data structure in detail. Our dataset and measurement tools are publicly available.
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Vomhoff, V.: Reliability of Crowdsourced Measurements, (2019).
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Raffeck, S.: Energiemessungen für LoRaWAN/IoT-Geräte, (2019).
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Chaplick, S., Lipp, F., Wolff, A., Zink, J.: Compact drawings of 1-planar graphs with right-angle crossings and few bends. Comput. Geom. 84, 50-68 (2019).
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Biskup, F.: IoT-Datenanalyse im Smart City-Kontext, (2019).
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Moldovan, C.: Contributions to TF "Managing Web & Cloud QoE". , 13th Qualinet General Meeting, Berlin, Germany (2019).
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Moldovan, C.: User Behavior and Engagement of a Mobile Video Streaming User from Crowdsourced Measurements, (2019).
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Wamser, F., Tran-Gia, P., Geißler, S., Hoßfeld, T.: Modeling of Traffic Flows in Internet of Things Using Renewal Approximation. International Conference on Optimization and Decision Science (ODS2019) (2019).
This paper proposes a versatile approach to model aggregated traffic flows in the Internet of Things (IoT) using renewal approximation. The modeled traffic originates from a large number of sources or devices consisting of a set of sensors mixed with classical elastic random traffic modeled as Poisson arrival process. The work shows the exact derivation in the simple case for periodic sensors. It shows further results in the mixed case with periodic sensors and a background process. The renewal approximation allows to derive the required number of sensors such that the aggregated traffic can be approximated as Poisson process.
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Moldovan, C., Wamser, F., Hoßfeld, T.: User Behavior and Engagement of a Mobile Video Streaming User from Crowdsourced Measurements. 2019 Eleventh International Conference on Quality of Multimedia Experience (QoMEX) (2019).
Mobile video streaming has gained a lot of popularity in recent year with the introduction of large data plans for mobile phones. While users in non-mobile scenarios have become accustomed to high quality and few stalling events, this is not the case in mobile environments. People are more likely to tolerate stalling since they know high throughput coverage cannot always be guaranteed. Their behavior and their engagement are drastically different when watching videos on mobile devices. In this paper, we characterize mobile phone users who use a video streaming application. We present a data set of over 6,000 video views from a crowdsourced video measurement study. We investigate user activity and engagement during video streaming and how such metrics are correlated with each other. This is the first study that goes beyond user engagement and investigates the direct behavior of mobile video users outside the lab which is an important step towards mobile QoE management.
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Schaper, P., Grundgeiger, T.: Commission Errors with Forced Response Lag. Quarterly Journal of Experimental Psychology. 72, 2380-2392 (2019).
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Reynolds, R.M., Novotny, E., Lee, J., Roth, D., Bente, G.: Ambiguous Bodies: The Role of Displayed Arousal in Emotion [Mis]Perception. Journal of Nonverbal Behavior. (2019).
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Moldovan, C.: Energy-Efficient Adaptation Logic for HTTP Streaming in Mobile Networks. , 2019 International Conference on Networked Systems (NetSys), Garching, Germany (2019).
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Roth, D., Stauffert, J.-P., Latoschik, M.E.: Avatar Embodiment, Behavior Replication, and Kinematics in Virtual Reality. In: Sherman, W.R. (hrsg.) VR Developer Gems. S. 321-348. Springer US (2019).
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Roth, D., Bloch, C., Schmitt, J., Frischlich, L., Latoschik, M.E., Bente, G.: Perceived Authenticity, Empathy, and Pro-social Intentions Evoked Through Avatar-mediated Self-disclosures. Proceedings of Mensch Und Computer 2019. S. 21--30. ACM, New York, NY, USA (2019).
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Ring, M., Schlör, D., Landes, D., Hotho, A.: Flow-based network traffic generation using Generative Adversarial Networks. Computers & Security. 82, 156 - 172 (2019).
Flow-based data sets are necessary for evaluating network-based intrusion detection systems (NIDS). In this work, we propose a novel methodology for generating realistic flow-based network traffic. Our approach is based on Generative Adversarial Networks (GANs) which achieve good results for image generation. A major challenge lies in the fact that GANs can only process continuous attributes. However, flow-based data inevitably contain categorical attributes such as IP addresses or port numbers. Therefore, we propose three different preprocessing approaches for flow-based data in order to transform them into continuous values. Further, we present a new method for evaluating the generated flow-based network traffic which uses domain knowledge to define quality tests. We use the three approaches for generating flow-based network traffic based on the CIDDS-001 data set. Experiments indicate that two of the three approaches are able to generate high quality data.
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Roth, D., von Mammen, S., Keil, J., Schildknecht, M., Latoschik, M.E.: Approaching Difficult Terrain with Sensitivity: A Virtual Reality Game on the Five Stages of Grief. Gehalten auf der (2019).
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Eckstein, B., Krapp, E., Elsässer, A., Lugrin, B.: Smart substitutional reality: Integrating the smart home into virtual reality. Entertainment Computing. 31, 100306 (2019).
Recent advances in VR technology allow users to consume immersive content within their own living room. Substitutional Reality (SR) promises to enhance this experience by integrating the physical environment into the simulation. We propose a novel approach, called Smart Substitutional Reality (SSR), that extends the passive haptics of SR with the interactive functionality of a smart home environment. SSR is meant to serve as a foundation for serious games. In this paper, we describe the concept of SSR alongside the implementation of a prototype in our smart lab. We designed multiple virtual environments with a varying degree of mismatch compared to the real world, and added selected objects to induce additional haptic and thermal stimuli to increase immersion. In two user studies we investigate their impact on spatial presence and intrinsic motivation which are especially important for serious games. Results suggest that spatial presence is maintained with higher mismatch, and increased by inducing additional stimuli. Intrinsic motivation is increased in both cases.
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Wassermann, S., Casas, P., Seufert, M., Wamser, F.: On the Analysis of YouTube QoE in Cellular Networks through in-Smartphone Measurements. 12th IFIP Wireless and Mobile Networking Conference (WMNC). , Paris, France (2019).
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Seufert, M.: Research Activities Report for "Managing Web & Cloud QoE TF". , 13th Qualinet General Meeting, Berlin, Germany (2019).
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Seufert, M.: Fundamental Advantages of Considering Quality of Experience Distributions over Mean Opinion Scores. , 11th International Conference on Quality of Multimedia Experience (QoMEX), Berlin, Germany (2019).
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Seufert, M.: Is QUIC becoming the New TCP? On the Potential Impact of a New Protocol on Networked Multimedia QoE. , 11th International Conference on Quality of Multimedia Experience (QoMEX), Berlin, Germany (2019).
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Geißler, S., Prantl, T., Lange, S., Wamser, F., Hoßfeld, T.: Discrete-Time Analysis of the Blockchain Distributed Ledger Technology. 31st International Teletraffic Congress (ITC). , Budapest, Hungary (2019).
Blockchain and distributed ledger technologies have become more and more popular and widespread during recent years. After the initial hype about the technology and many cryptocurrency related use cases, the technology slowly starts to make its way into other domains like food tracking and document management. In order to further contribute to the search of what this technology can be used for, more detailed performance evaluations are required in order to investigate key performance indicators and general limits of the technology. To this end, we develop a discrete-time queueing model that allows a detailed evaluation of the characteristics of a blockchain system, such as the transaction waiting time distribution. Furthermore, we validate the model by comparing the results to values obtained from measurements in a closed lab environment based on the Ethereum blockchain.
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von Mammen, S., Müller, A., Latoschik, M.E., Botsch, M., Brukamp, K., Schröder, C., Wacker, M.: VIA VR: A Technology Platform for Virtual Adventures for Healthcare and Well-Being. VS-Games. S. 1-2 (2019).
To harness the potential of virtual reality (VR) in the healthcare sector, the expenditures for users such as clinics, doctors or health insurances, have to be reduced – a requirement the technology platform VIA VR (an acronym from “virtual reality adventures” and VR) promises to fulfill by combining several key technologies to allow specialists from the healthcare sector to create high-impact VR adventures without the need for a background in programming or the design of virtual worlds. This paper fleshes out the concept of VIA VR, its technological pillars and the planned R&D agenda.
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Kalmbach, P., Hock, D., Lipp, F., Kellerer, W., Blenk, A.: NOracle: Who is communicating with whom in my network? SIGCOMM Posters and Demos. S. 48-50. ACM (2019).
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Linguaglossa, L., Lange, S., Pontarelli, S., Retvari, G., Rossi, D., Zinner, T., Bificulo, R., Jarschel, M., Bianchi, G.: Survey of Performance Acceleration Techniques for Network Function Virtualization. Proceedings of the IEEE. (2019).
The ongoing network softwarization trend holds the promise to revolutionize network infrastructures by making them more flexible, reconfigurable, portable, and more adaptive than ever. Still, the migration from hard-coded/hardwired network functions towards their software-programmable counterparts comes along with the need for tailored optimizations and acceleration techniques, so as to avoid, or at least mitigate, the throughput/latency performance degradation with respect to fixed function network elements. The contribution of this article is twofold. First, we provide a comprehensive overview of the host-based Network Function Virtualization (NFV) ecosystem, covering a broad range of techniques, from low level hardware acceleration and bump-in-the-wire offloading approaches, to high-level software acceleration solutions, including the virtualization technique itself. Second, we derive guidelines regarding the design, development, and operation of NFV-based deployments that meet the flexibility and scalability requirements of modern communication networks.
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Kern, F., Winter, C., Gall, D., Käthner, I., Pauli, P., Latoschik, M.E.: Immersive Virtual Reality and Gamification Within Procedurally Generated Environments to Increase Motivation During Gait Rehabilitation. 2019 IEEE Conference on Virtual Reality and 3D User Interfaces (VR). S. 500-509 (2019).
Virtual Reality (VR) technology offers promising opportunities to improve traditional treadmill-based rehabilitation programs. We present an immersive VR rehabilitation system that includes a head-mounted display and motion sensors. The application is designed to promote the experience of relatedness, autonomy, and competence. The application uses procedural content generation to generate diverse landscapes. We evaluated the effect of the immersive rehabilitation system on motivation and affect. We conducted a repeated measures study with 36 healthy participants to compare the immersive program to a traditional rehabilitation program. Participants reported significant greater enjoyment, felt more competent and experienced higher decision freedom and meaningfulness in the immersive VR gait training compared to the traditional training. They experienced significantly lower physical demand, simulator sickness, and state anxiety, and felt less pressured while still perceiving a higher personal performance. We derive three design implications for future applications in gait rehabilitation: Immersive VR provides a promising augmentation for gait rehabilitation. Gamification features provide a design guideline for content creation in gait rehabilitation. Relatedness and autonomy provide critical content features in gait rehabilitation.
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Skwarek, V., Reher, J., Geißler, S., Zinner, T.: Automation und Digitalisierung - Potenzial und Einsatz von Blockchain- und Distributed-Ledger-Technologien in der Automatisierungstechnik, (2019).
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Metter, C.: Resilience, Availability, and Serviceability Evaluation in Software-defined Networks, (2019).
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Oberdörfer, S., Latoschik, M.E.: Knowledge Encoding in Game Mechanics: Transfer-Oriented Knowledge Learning in Desktop-3D and VR. International Journal of Computer Games Technology. 2019, (2019).
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Loh, F.: Machine Learning Approach to Classify Video Stalls at Network Layer, (2019).
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Lugrin, J.-L., Latoschik, M.E., Glémarec, Y., Bosser, A.-G., Chollet, M., Lugrin, B.: Towards Narrative-Driven Atmosphere for Virtual Classroom. Extended Abstracts of the 2019 CHI Conference on Human Factors in Computing Systems. S. 1-6 (2019).
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Lugrin, J.-L., Landeck, M., Latoschik, M.E.: Simulated Reference Frame Effects on Steering, Jumping and Sliding. Proceedings of the 26th IEEE Virtual Reality (VR) conference. S. 1062-1063 (2019).
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Hertweck, S., Weber, D., Alwanni, H., Unruh, F., Fischbach, M., Latoschik, M.E., Ball, T.: Brain Activity in Virtual Reality: Assessing Signal Quality of High-Resolution EEG While Using Head-Mounted Displays. Proceedings of the 26th IEEE Conference on Virtual Reality and 3D User Interfaces (VR). S. 970-971. IEEE (2019).
Biometric measures such as the electroencephalogram (EEG) promise to become viable alternatives to subjective questionnaire ratings for the evaluation of psychophysical effects associated with Virtual Reality (VR) systems, as they provide objective and continuous measurements without breaking the exposure. The extent to which the EEG signal can be disturbed by the presence of VR sys- tems, however, has been barely investigated. This study outlines how to evaluate the compatibility of a given EEG-VR setup on the example of two commercial head-mounted displays (HMDs), the Oculus Rift and the HTC Vive Pro. We use a novel experimental protocol to compare the spectral composition between conditions with and without an HMD present during an eyes-open vs. eyes-closed task. We found general artifacts at the line hum of 50 Hz, and additional HMD refresh rate artifacts (90 Hz) for the Oculus rift exclusively. Frequency components typically most interesting to non-invasive EEG research and applications (<50 Hz), however, remained largely unaffected. We observed similar topographies of visually-induced modulation of alpha band power for both HMD conditions in all subjects. Hence, the study introduces a necessary validation test for HMDs in combination with EEG and further promotes EEG as a potential biometric measurement method for psychophysical effects in VR systems.
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Oberdörfer, S., Heidrich, D., Latoschik, M.E.: Usability of Gamified Knowledge Learning in VR and Desktop-3D. Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems. S. 1-13 (2019).
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Schwind, A., Janiak, L., Moldovan, C., Wamser, F., Hoßfeld, T.: Peeking under the Hood – How the Measurement Setup Influences the Video Streaming Behavior. The 3rd International Workshop on Quality of Experience Management (QoE-Management 2019). , Paris, France (2019).
Global Internet video traffic will dramatically increase in the next years. With this rapid growth, interest in the application behavior of video streaming services and the resulting user experience rises. In particular, there is a need to understand the influence of system parameters on the streaming performance. Thus, several monitoring approaches have been developed which allow conducting automated measurements on a large-scale, for example, lightweight approaches for measurements running in the mobile networks or setups using a virtual frame buffer for servers without a display running in virtualized cloud environments. In some cases, the measurement hardware can totally be controlled, in other cases, there is no knowledge about parallel running services. In this paper, we answer the question whether and how much the measurement setup (e.g., virtualization, headless browsers, load on machines) influences the video streaming behavior. Therefore, we compare eight management setups with the ground truth (an end user watching a video on the own device) by evaluating the key performance indicators on application layer during video streaming, i.e. initial video playout delays and stalling. Our results reveal important insights: some of the common measurement setups heavily influence the measurements and must be avoided to collect reliable results.
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Heidrich, D., Oberdörfer, S., Latoschik, M.E.: The Effects of Immersion on Harm-Inducing Factors in Virtual Slot Machines. Proceedings of the 26th IEEE Virtual Reality (VR) conference. S. 793-801. IEEE (2019).
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Hamzeheinejad, N.: VR Simulation as a Motivator in Gait Rehabilitation. Proceedings of the 26th IEEE Virtual Reality (VR) conference. IEEE (2019).
Gait rehabilitation is a necessary process for patients suffering from post-stroke motor impairments. The patients are required to perform repetitive practices using a robot-assisted gait device. Repeated exercises can become extremely frustrating and the patients lose their motivation over time. In my PhD research, I focus on Virtual Reality (VR) as a medium to improve gait rehabilitation in terms of enjoyment, motivation, efficiency, and effectiveness. The objective is to systematically investigate different factors, such as the presence of a trainer, interactivity, gamification, and storytelling in a two-step process. First, by evaluating the applicability of different factors for the clinical use with healthy subjects. Second, by evaluating the effectiveness of the VR simulation with patients with gait deficits, especially stroke patients in collaboration with a [country] clinic.
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Hamzeheinejad, N., Roth, D., Götz, D., Weilbach, F., Latoschik, M.E.: Physiological Effectivity and User Experience of Immersive Gait Rehabilitation. The First IEEE VR Workshop on Applied VR for Enhanced Healthcare (AVEH). S. 1421-1429. IEEE (2019).
Gait impairments from neurological injuries require repeated and exhaustive physical exercises for rehabilitation. Prolonged physical training in clinical environments can easily become frustrating and de-motivating for various reasons which in turn risks to decrease efficiency during the healing process. This paper introduces an immersive VR system for gait rehabilitation which targets user experience and increase of motivation while evoking comparable physiological responses needed for successful training effects. The system provides a virtual environment consisting of open fields, forest, mountains, waterfalls, animals, and a beach for inspiring strolls and is able to include a virtual trainer as a companion during the walks. We evaluated the ecological validity of the system with healthy subjects before performing the clinical trial. We assessed the systemu0027s target qualities with a longitudinal study with 45 healthy participants in three consecutive days in comparison to a baseline non-VR condition. The system was able to evoke similar physiological responses. The workload was increased for the VR condition but the system also elicited a higher enjoyment and motivation which was the main goal. The latter benefits slightly decreased over time (as did workload) while they were still higher than in the non-VR condition. The virtual trainer did not show to be beneficial, the corresponding implications are discussed. Overall, the approach shows promising results which renders the system a viable alternative for the given use case while it motivates interesting direction for future work.
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Baumeister, J.: Experience-based Quality Assessment of Distributed Knowledge Graphs. WM 2019 - 10te Konferenz Professionelles Wissensmanagement (2019).
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Seufert, M.: QUICker or not? - an Empirical Analysis of QUIC vs TCP for Video Streaming QoE Provisioning. , 3rd International Workshop on Quality of Experience Management (QoE-Management), Paris, France (2019).
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Korger, A., Baumeister, J.: Textual Case-based Adaptation using Semantic Relatedness - A Case Study in the Domain of Security Documents. WM2019 - 10te Konferenz Professionelles Wissensmanagement (2019).
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Latoschik, M.E., Kern, F., Stauffert, J.-P., Bartl, A., Botsch, M., Lugrin, J.-L.: Not Alone Here?! Scalability and User Experience of Embodied Ambient Crowds in Distributed Social Virtual Reality. IEEE Transactions on Visualization and Computer Graphics (TVCG). 25, 2134-2144 (2019).
This article investigates performance and user experience in Social Virtual Reality (SVR) targeting distributed, embodied, and immersive, face-to-face encounters. We demonstrate the close relationship between scalability, reproduction accuracy, and the resulting performance characteristics, as well as the impact of these characteristics on users co-located with larger groups of embodied virtual others. System scalability provides a variable number of co-located avatars and AI-controlled agents with a variety of different appearances, including realistic-looking virtual humans generated from photogrammetry scans. The article reports on how to meet the requirements of embodied SVR with todayu0027s technical off-the-shelf solutions and what to expect regarding features, performance, and potential limitations. Special care has been taken to achieve low latencies and sufficient frame rates necessary for reliable communication of embodied social signals. We propose a hybrid evaluation approach which coherently relates results from technical benchmarks to subjective ratings and which confirms required performance characteristics for the target scenario of larger distributed groups. A user-study reveals positive effects of an increasing number of co-located social companions on the quality of experience of virtual worlds, i.e., on presence, possibility of interaction, and co-presence. It also shows that variety in avatar/agent appearance might increase eeriness but might also stimulate an increased interest of participants about the environment.
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Schwind, A., Midoglu, C., Alay, Ö., Griwodz, C., Wamser, F.: Dissecting the performance of YouTube video streaming in mobile networks. International Journal of Network Management. (2019).
Video streaming applications constitute a significant portion of the Internet traffic today, with mobile accounting for more than half of the online video views. The high share of video in the current Internet traffic mix has prompted many studies that examine video streaming through measurements. However, streaming performance depends on many different factors at different layers of the TCP/IP stack. For example, browser selection at the application layer or the choice of protocol in transport layer can have significant impact on the video performance. Furthermore, video performance heavily depends on the underlying network conditions (eg, network and link layers). For mobile networks, the conditions vary significantly, since each operator has a different deployment strategy and configuration. In this paper, we focus on YouTube and carry out a comprehensive study investigating the influence of different factors on streaming performance. Leveraging the Measuring Mobile Broadband Networks in Europe (MONROE) test bed that enables experimentation with 13 different network configurations in four countries, we collect more than 1800 measurement samples in operational mobile networks. With this campaign, our goal is to quantify the impact of parameters from different layers on YouTube's streaming quality of experience (QoE). More specifically, we analyze the role of the browser (eg, Firefox and Chrome), the impact of transport protocol (eg, TCP or QUIC), the influence of network bandwidth, and signal coverage on streaming QoE. Our analysis reveals that all these parameters need to be taken into account jointly for network management practices, in order to ensure a high end‐user experience.
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Seufert, M., Schatz, R., Wehner, N., Casas, P.: QUICker or not? - an Empirical Analysis of QUIC vs TCP for Video Streaming QoE Provisioning. 3rd International Workshop on Quality of Experience Management (QoE-Management). , Paris, France (2019).
The introduction of the QUIC (Quick UDP Internet Connections) transport protocol by Google aimed to improve the Quality of Experience (QoE) with web services compared to the prevailing Transport Control Protocol (TCP). Nowadays, QUIC has become the default protocol to communicate between the Google Chrome browser and Google servers and accounts for an increasing share of the Internet traffic. This work investigates whether the promised QoE benefits of QUIC are indeed noticeable for end users or not. A measurement study was conducted for YouTube video streaming in two mobile and two fixed access networks, in which a defined set of videos was streamed back-to-back with QUIC and TCP in randomized order. QoE factors of video streaming (such as initial delay, the visual quality of the video, and stalling) were compared statistically to find significant differences between the streaming over QUIC and the streaming over TCP. Surprisingly, no evidence for any QoE improvement of QUIC over TCP in the context of YouTube streaming could be found.
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Göritz, A., Borchert, K., Hirth, M.: Using Attention Testing to Select Crowdsourced Workers and Research Participants. Social Science Computer Review. (2019).
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Baumeister, J., Sehne, V., Wienrich, C.: A Systematic View on Speech Assistants for Service Technicians. Proceedings of LWDA - Lernen. Wissen. Daten. Analysen 2019. S. 195-206. , Humboldt-Universität zu Berlin (2019).
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Winter, C., Kern, F., Käthner, I., Gall, D., Latoschik, M.E., Pauli, P.: Virtuelle Realität als Ergänzung des Laufbandtrainings zur Rehabilitation von Gangstörungen bei Patienten mit Schlaganfall und Multipler Sklerose. (2019).
Die Technik der virtuellen Realität (VR) bietet neue Behandlungsmöglichkeiten in der Rehabilitation neurologischer Erkrankungen. Vorherige Studien haben gezeigt, dass ein VR-basiertes Laufbandtraining bei Patienten mit Gangstörungen nicht nur den physischen, sondern auch den psychischen Therapieerfolg steigert und damit eine sinnvolle Ergänzung zum herkömmlichen Gangtraining darstellt. In der vorliegenden Studie wurde untersucht, welche Auswirkungen die immersive Darbietung einer virtuellen Umgebung (über ein Head-Mounted-Display, HMD) gegenüber der semi-immersiven Darbietung der VR (über einen Flachbildmonitor) und dem herkömmlichen Laufbandtraining ohne VR hat. Dazu durchliefen zunächst 36 gesunde Probanden und anschließend 14 MS- bzw. Schlaganfallpatienten mit Gangstörungen jeweils die drei verschiedenen Laufbandbedingungen (immersiv, semi-immersiv und ohne VR). Die eingesetzte virtuelle Umgebung enthielt Gamification-Elemente zur Motivationssteigerung und wurde auf Grundlage der Selbstbestimmungstheorie nach Ryan und Deci implementiert. Die Studie mit gesunden Probanden diente dazu, die Gebrauchstauglichkeit (Usability) zu prüfen und technische Defizite aufzudecken. In einer Proof-of-Concept-Studie mit 14 MS- und Schlaganfallpatienten wurde anschließend anhand der Anwendung getestet, ob Patienten mit einem VR-gestützten Laufbandtraining im Rahmen der Behandlung ihrer Gangstörungen (EDSS < 6) ihre Lauffähigkeiten verbessern können. Primäres Outcome Maß war in beiden Studien die durchschnittliche Laufgeschwindigkeit innerhalb der einzelnen Bedingungen. Mittels standardisierter Fragebögen wurden zusätzlich Motivation, Benutzerfreundlichkeit, Präsenzerleben (Igroup Presence Questionnaire) und Nebenwirkungen des VR-Systems (Simulator Sickness Questionnaire) untersucht. Außerdem wurde die Präferenz der Studienteilnehmer in Bezug auf die drei Bedingungen erfragt. Sowohl in der Studie mit gesunden Teilnehmern als auch in der Patientenstudie zeigte sich bei der HMD-Bedingung eine signifikant höhere durchschnittliche Laufgeschwindigkeit als beim Laufbandtraining ohne VR. Das Präsenzerleben war in beiden Studien in der HMD-Bedingung signifikant höher als in der Monitor-Bedingung. Darüber hinaus sind keine Nebenwirkungen durch die virtuelle Welt im Sinne einer Simulator Sickness aufgetreten. Die Studienteilnehmer hatten keine relevanten VR-bedingten Haltungsschwierigkeiten oder Probleme in Bezug auf das visuelle Display. Während die Motivation bei den gesunden Probanden nach dem HMD-Durchgang im Vergleich zu den anderen beiden Bedingungen höher ausfiel, wurden in der Patientenstudie keine signifikanten Unterschiede detektiert. Dennoch gaben die Patienten an, die virtuelle Welt in der HMD-Bedingung als motivierender empfunden zu haben als in der Monitor-Bedingung. Unter allen drei Bedingungen wurde das HMD-Laufbandtraining von 71 % (n = 14) der Patienten und 89 % (n = 36) der gesunden Versuchsteilnehmer präferiert. Ebenfalls 71 % der Patienten könnten sich vorstellen, das HMD-Laufbandtraining in Zukunft häufiger zu nutzen.
