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Beyer, S., Chimani, M., Spoerhase, J.: A Simple Primal-Dual Approximation Algorithm for 2-Edge-Connected Spanning Subgraphs. Proc. 26th International Computing and Combinatorics Conference (COCOON'20) (2020).
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Wassermann, S., Casas, P., Seufert, M., Wehner, N., Schüler, J., Hoßfeld, T.: How Good is your Mobile (Web) Surfing? SpeedIndex Inference from Encrypted Traffic, (2020).
We address the problem ofWeb QoE monitoring, in particular Speed Index (SI), from the Internet Service Provider (ISP) perspective, relying on in-network, passive measurements. Given the wide adoption of end-to-end encryption, we resort to machine-learning models to infer the SI of individual web-page loading sessions, using as input only packet-level data. Our study targets the analysis of SI in mobile devices, including smartphones and tablets. To the best of our knowledge, this is the first paper addressing the inference of SI from encrypted network traffic in mobile devices.
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Kobs, K., Zehe, A., Bernstetter, A., Chibane, J., Pfister, J., Tritscher, J., Hotho, A.: Emote-Controlled: Obtaining Implicit Viewer Feedback through Emote based Sentiment Analysis on Comments of Popular Twitch.tv Channels. ACM Transactions on Social Computing. 3, 1--34 (2020).
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Supervisor: Seufert, M.: Data Augmentation for Machine Learning on Network Traffic, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de ### Title: Data Augmentation for Machine Learning on Network Traffic (Deutsche Beschreibung weiter unten) Abstract: Machine learning models need huge amounts of data for the training of models to succeed. One approach to increasing the amount of training data is to take already available data and alter them slightly without changing the label of the data. This so called “data augmentation” is especially popular for image data. For example, an existing image of a bird can be slightly rotated or resized to create a new training example (alteration of available data), which has the same label (bird). In this thesis, similar methods for data augmentation of network traffic shall be developed and implemented. ### Titel: Datenvermehrung für maschinelles Lernen auf Netzverkehr Inhalt: Maschinelles Lernen benötigt sehr große Datenmenge, damit Modelle erfolgreich trainiert werden können. Ein Ansatz um die Menge an Trainingsdaten zu erhöhen ist es, bereits verfügbare Daten zu nehmen und sie leicht zu modifizieren ohne das Label, d.h., die Klasse der Daten, zu verändern. Diese sogenannte Datenvermehrung oder „Data Augmentation“ ist besonders bei Bilddaten beliebt. Zum Beispiel kann ein existierendes Bild eines Vogels leicht gedreht oder skaliert werden, um ein neues Trainingsbeispiel zu erhalten (Veränderung von existierenden Daten), das die selbe Klasse (Vogel) besitzt. In dieser Arbeit sollen ähnliche Methoden für die Datenvermehrung von Netzverkehr entwickelt und implementiert werden.
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von der Pütten, A.M.R., Lugrin, B., Steinhaeusser, S.C., Klass, L.: Context Matters! Identifying Social Context Factors and Assessing Their Relevance for a Socially Assistive Robot. Companion of the 2020 International Conference on Human-Robot Interaction. S. 409-411. ACM (2020).
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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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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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Wieser, V.: Measurement Box for Bandwidth Traces under Mobility, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de ### Title: Measurement Box for Bandwidth Traces under Mobility (Deutsche Beschreibung weiter unten) Abstract: In this thesis, a portable measurement box shall be developed to create bandwidth traces in wireless networks (mobile networks and WiFi). For this, an appropriate bandwidth measurement methodology has to be selected and implemented. The implemented measurement approach must be validated. Afterwards, different measurements shall be conducted under mobility, i.e., during movement of the measurement box. These movements may include walking, cycling, or driving in car, bus, tram, etc. The influence of different movements on the available bandwidth shall be evaluated. ### Titel: Messapparatur für Bandbreitenaufzeichnungen unter Mobilität Inhalt: In dieser Arbeit soll eine tragbare Messapparatur entwickelt werden mit der man die Bandbreite in kabellosen Netzen (Mobilfunk oder WLAN) aufzeichnen kann. Dafür muss ein geeignete Methodik für die Bandbreitenmessung ausgewählt und implementiert werden. Der implementierte Messansatz muss validiert werden. Danach sollen verschiedene Messungen unter Mobilität durchgeführt werden, d.h. während der Messapparat bewegt wird. Diese Bewegungen können Laufen, Rad fahren oder fahren in einem Auto, Bus, Straßenbahn etc. umfassen. Der Einfluss verschiedener Bewegungen auf die verfügbare Bandbreite soll ausgewertet werden.
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Supervisor: Seufert, M.: QoE Study for Session-based Web Browsing, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de ### Title: QoE Study for Session-based Web Browsing (Deutsche Beschreibung weiter unten) Abstract: Quality of Experience (QoE) is an important concept in communication network research, which describes the subjective experience and/or satisfaction with a networked service. For example, for web browsing, it is well known that the QoE is negatively affected when the page load time of a website increases. While the QoE of browsing individual pages has already been studied in the past, it is not clear how the QoE is formed when considering a whole browsing session. In this thesis, a web-based QoE study for session-based QoE of web browsing shall be designed, implemented and conducted. The results of the QoE study shall be evaluated to investigated the formation of session-based QoE. ### Titel: QoE-Studie für sessionbasiertes Webbrowsing Inhalt: Quality of Experience (QoE) ist ein wichtiges Konzept in der Forschung an Kommunikationsnetzen, das die subjektive Empfindung und/oder Zufriedenheit mit einem Netzwerkdienst beschreibt. Für Webbrowsing, zum Beispiel, ist bekannt, dass die QoE negativ beeinflusst wird, wenn die Seitenladezeit einer Webseite steigt. Während die QoE beim Browsen von individuellen Seiten in der Vergangenheit schon untersucht wurde, ist es noch nicht klar, wie sich die QoE verhält, wenn man eine ganze Browsing-Session betrachtet. In dieser Arbeit soll eine webbasierte QoE-Studie für sessionbasiertes Webbrowsing entworfen, implementiert und durchgeführt werden. Die Ergebnisse der QoE-Studie sollen ausgewertet werden, um die Bildung von sessionbasierter QoE zu untersuchen.
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Kunz, F., Hirth, M., Schweitzer, T., Linz, C., Goetz, B., Stellzig-Eisenhauer, A., Borchert, K., Böhm, H.: Subjective perception of craniofacial growth asymmetries in patients with deformational plagiocephaly. Springer Clinical Oral Investigations. 24, https://doi.org/10.1007/s00784-020-03417-y (2020).
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Oberdörfer, S., Elsässer, A., Schraudt, D., Grafe, S., Latoschik, M.E.: Horst – The Teaching Frog: Learning the Anatomy of a Frog Using Tangible AR. Proceedings of the 2020 Mensch und Computer Conference (MuC '20). 303-307 (2020).
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Ziebell, P., Stümpfig, J., Eidel, M., Kleih, S.C., Kübler, A., Latoschik, M.E., Halder, S.: Stimulus modality influences session-to-session transfer of training effects in auditory and tactile streaming-based P300 brain–computer interfaces. Scientific Reports. 10, 11873-- (2020).
Despite recent successes, patients suffering from locked-in syndrome (LIS) still struggle to communicate using vision-independent brain–computer interfaces (BCIs). In this study, we compared auditory and tactile BCIs, regarding training effects and cross-stimulus-modality transfer effects, when switching between stimulus modalities. We utilized a streaming-based P300 BCI, which was developed as a low workload approach to prevent potential BCI-inefficiency. We randomly assigned 20 healthy participants to two groups. The participants received three sessions of training either using an auditory BCI or using a tactile BCI. In an additional fourth session, BCI versions were switched to explore possible cross-stimulus-modality transfer effects. Both BCI versions could be operated successfully in the first session by the majority of the participants, with the tactile BCI being experienced as more intuitive. Significant training effects were found mostly in the auditory BCI group and strong evidence for a cross-stimulus-modality transfer occurred for the auditory training group that switched to the tactile version but not vice versa. All participants were able to control at least one BCI version, suggesting that the investigated paradigms are generally feasible and merit further research into their applicability with LIS end-users. Individual preferences regarding stimulus modality should be considered.
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Supervisor: Loh, F.: Demand Study and Performance Evaluation of Future Smart City Networks, (2020).
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Supervisor: Loh, F.: Solving the Collision Problem with Aggregation? A Measurement Driven LoRaWAN Study., (2020).
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Stauffert, J.-P., Niebling, F., Latoschik, M.E.: Simultaneous Run-Time Measurement of Motion-to-Photon Latency and Latency Jitter. 2020 IEEE Conference on Virtual Reality and 3D User Interfaces (VR). S. 636--644. IEEE (2020).
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Supervisor: Metzger, F.: Vehicular and Wireless Traffic Simulation and Optimization under Urban Mobility, (2020).
Modern cities have complex interactions of vehicular, pedestrian and wireless networks. Any communal wireless network should strive to fullfil these demands. Your task would be to create a model of the city of Würzburg in SUMO (Simulation of Urban MObility) and OMNeT++ in order to evaluate Würzburg's (wireless) traffic demands and subsequently optimize them.
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Chaplick, S., Fleszar, K., Lipp, F., Ravsky, A., Verbitsky, O., Wolff, A.: Drawing Graphs on Few Lines and Few Planes. Journal of Computational Geometry. 11, 433--475 (2020).
We investigate the problem of drawing graphs in 2D and 3D such that their edges (or only their vertices) can be covered by few lines or planes. We insist on straight-line edges and crossing-free drawings. This problem has many relations to other challenging graph-drawing problems such as small-area or small-volume drawings, layered or track drawings, and drawing graphs with low visual complexity. While some facts about our problem are implicit in previous work, this is the first treatment of the problem in its full generality. Our contribution is as follows. par We show lower and upper bounds for the numbers of lines and planes needed for covering drawings of graphs in certain graph classes. In some cases our bounds are asymptotically tight; in some cases we are able to determine exact values. par We relate our parameters to standard combinatorial characteristics of graphs (such as the chromatic number, treewidth, or arboricity) and to parameters that have been studied in graph drawing (such as the track number or the number of segments appearing in a drawing). par We pay special attention to planar graphs. For example, we show that there are qplanar graphs that can be drawn in 3-space on asymptotically fewer lines than in the plane.
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Wolf, E., Döllinger, N., Mal, D., Wienrich, C., Botsch, M., Latoschik, M.E.: Body Weight Perception of Females using Photorealistic Avatars in Virtual and Augmented Reality. 2020 IEEE International Symposium on Mixed and Augmented Reality (ISMAR) (2020).
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Supervisor: Metzger, F.: Design and Evaluation of a Cloud Gaming Crowdsourcing Study, (2020).
The second wave of cloud gaming services is currently gaining traction. But we are still not sure of the subjective experience of games streamed over these services when compared to them running locally. Your task in this work would be to design the methodology for a crowdsourcing QoE assessment for cloud gaming, execute it and subsequently evaluate its results.
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Wehner, N., Mertinat, N., Seufert, M., Hoßfeld, T.: Studying the Impact of the Content Selection Method on the Video QoE on Mobile Devices, (2020).
When conducting video QoE studies, participants are usually asked to rate the QoE of prepared test videos. However, participants are given no choice to select content, which they like or in which they are interested. This may cause annoyance or frustration when conducting the QoE study, which eventually might affect the QoE results of the study. The consequent question is whether the content liking has a direct impact on the submitted ratings by the participants and whether the freedom of choosing the video content in QoE studies results in better ratings. To investigate this research question, MCA, an existing framework for crowdsourced video testing, is extended and used in a pilot field study. MCA runs on mobile devices and allows users to watch the tested conditions of a QoE study within video content of their interest. The results of a QoE study with individual and dynamic content selection are compared to a QoE study with pre-selected contents. Moreover, this work includes a comparison to a previous QoE study for validation. As the previous study was conducted on desktop PCs, the MCA study further allows to identify differences in the stalling perception between studies on desktop PCs and mobile devices.
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Supervisor: Wehner, N.: QoE Study for Compatible Video and Web Browsing QoE Models, (2020).
Contact: nikolas.wehner@uni-wuerzburg.de Abstract: Video streaming and web browsing are the dominant applications in the Internet today. Quality of Experience (QoE) is a concept introduced to describe the delight or frustration with a networked service. For both video streaming and web browsing, several QoE models have been proposed in literature. However, one persisting problem is the incompatiblity of these QoE models. As a consequence, modelling QoE for sessions including both video and web is an impossible task. Goal of this work is to design, implement, and conduct a QoE study which investigates both video streaming and web browsing within a session. The obtained results of the QoE study are then evaluated in order to propose compatible QoE models.
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Niebling, F., Bruschke, J., Messemer, H., Wacker, M., von Mammen, S.: Analyzing Spatial Distribution of Photographs in Cultural Heritage Applications. In: Liarokapis, F., Voulodimos, A., Doulamis, N., und Doulamis, A. (hrsg.) Visual Computing for Cultural Heritage. S. 391-408. Springer, Cham (2020).
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Supervisor: Wamser, F.: Blockchain in communication networks, (2020).
Das Ziel der Arbeit ist der Entwurf einer Methodik für die Ressourcenvergabe mittels Distributed Ledger-Verfahren (DLV) (Blockchain) im Netzwerk- und Anwendungsumfeld von Internetdiensten. Ein Beispiel für eine solche Ressourcenvergabe ergibt sich für aktuelle Webdienste wie Netflix. Netflix stellt seinen Dienst aus zahlreichen Einzelkomponenten zusammen: beispielsweise dem Videoplayer und den Videoinhalten. Diese Elemente liegen und werden in verschiedenen Clouds ausgeführt. Netflix muss sich Ressourcen bei verschiedenen Anbietern "zusammenkaufen". Solch ein zusammengestellter Dienst braucht einen Verteilungsalgorithmus, der Komponenten auf Clouds zuordnet. Die Idee in der Arbeit ist zu prüfen in wie fern man Blockchain hierfür nutzen kann, um Ressourcen zu buchen. Aufgaben in der Arbeit wären Konzepte und Ideen abzuleiten, die für die Ressourcenvergabe mittels Blockchain nötig sind. Eine weitere Aufgabe ist eine Literaturrecherche im Umfeld Blockchain.
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Evans, W., Gethner, E., Spalding-Jamieson, J., Wolff, A.: Angle Covers: Algorithms and Complexity. In: Rahman, S., Sadakane, K., und Sung, W.-K. (hrsg.) Proc. 14th Int. Workshop Algorithms Comput. (WALCOM'20). S. 94--106. Springer-Verlag (2020).
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Supervisor: Wamser, F.: Bewertung und Analyse von 5G-Mobilfunk: Large-scale Monitoring-Lösungen und -Konzepte zur Bestimmung der Leistung von 5G, (2020).
Derzeit gibt es sogenannte Datenprovider (siehe zB www.tutela.com), die über Mobile Apps Leistungsmessungen von 5G-Mobilfunknetzen machen. In dieser Arbeit sollen diverse Monitoring-Lösungen und -Konzepte, die im großen Umfang die Leistung von 5G bestimmen können (zB über Mobile Apps), untersucht werden. Bei Interesse und für weitere Details bitte melden! Florian Wamser
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Wamser, F.: Bewertung und Analyse von 5G-Mobilfunk: Grundlagen zu Crowdsourcing-basierten 5G-Mobilfunkmessungen, (2020).
In der Arbeit sollen Grundlagen zu Crowdsourcing-basierten 5G-Mobilfunkmessungen erarbeitet werden. Crowdsourcing-basierten 5G-Mobilfunkmessungen sind Messungen, die mit Mobilfunk-Apps oder Internet-Webseiten mit Hilfe eine Masse von Leuten erhoben werden. Diese Messungen sind oft nicht verlässlich und haben je nach Person und Geräte unterschiedliche Qualität.
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Supervisor: Wamser, F.: Aufbau eines Blockchain-Testbeds, (2020).
Im Praktikum soll ein Blockchain-Testbed aufgebaut werden. Wichtig ist, dass der Anwendungsfall Ressourcenvergabe in Cloud-Systemen berücksichtigt wird. Hierbei sollen mittels Blockchain Ressourcen gekauft und an Nutzer vergeben werden können. Das Testbed soll verschiedene Orte der Nutzer, die die Blockchain verwenden, abbilden. Hierzu müssen Latenzen zwischen Nutzern emuliert werden.
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Wehner, N., Seufert, M., Egger-Lampl, S., Gardlo, B., Casas, P., Schatz, R.: Scoring High: Analysis and Prediction of Viewer Behavior and Engagement in the Context of 2018 FIFA WC Live Streaming. Proceedings of the 28th ACM International Conference on Multimedia (MM). , Seattle, WA, USA (2020).
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Hofmann, J.: Deep Reinforcement Learning for Configuration of Time-Sensitive-Networking, (2020).
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Seufert, M.: 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 (virtual) (2020).
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Stauffert, J.-P., Niebling, F., Lugrin, J.-L., Latoschik, M.E.: Guided Sine Fitting for Latency Estimation in Virtual Reality. 2020 IEEE Conference on Virtual Reality and 3D User Interfaces Abstracts and Workshops (VRW). S. 707--708. IEEE (2020).
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Spangenberger, M.: HTTP Adaptive Video Streaming with Real-Time Encoding and Continuous Quality Levels, (2020).
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Supervisor: Metzger, F.: Profiling the E2E Delays of Streamed Video Games with the Camera Method, (2020).
Determining the E2E lag of actions in video games is not trivial since there is no built-in way to grasp the full lag, including that contributed by the input and output. A standardized method is to record both input and output with a high framerate camera and count the frames from a visible input event to the result on screen. Your job is to perform these measurements for different actions in a series of games, and examine the overhead game streaming generates for them. Note: It might currently not be possible to perform these experiments, as they rely on a physical testbench.
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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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Supervisor: Wehner, N.: Real-Time Machine Learning Pipeline for Web QoE Monitoring, (2020).
Contact: nikolas.wehner@uni-wuerzburg.de Abstract: Web browsing is the ubiquitous application in the Internet today and Internet Service Providers or Content Service Providers strive to guarantee a high service experience for their customers in the Web and thus avoid churning and revenue losses. This service experience can be described with Quality of Experience (QoE), a concept introduced to describe the delight or frustration with a networked service. In the context of Web QoE, the delight or frustration is approximated using known metrics like Speed Index or Above-The-Fold to approximate the real QoE. However, in encrypted networks it is not any longer possible to directly access these metrics and they have to be derived from the network traffic using machine learning instead. In order to permanently guarantee a high QoE, a service provider has to perform QoE monitoring and subsequently QoE management when there is a need for improvement. In this work, an on-line ML pipeline for Web QoE monitoring shall be designed and implemented. It should be able to randomly browse to a website, capture the network traffic and the corresponding required ground truth metrics, extract features from the network traffic in real-time, and finally estimate the QoE based on these features and the deployed ML model. It is not expected that a ML model is developed, but only that an existing one is only deployed. Finally, a study is performed and evaluated with the goal to show the validity of the pipeline. As another optional final step, the whole process could be illustrated in a dashboard, for example with streamlit (https://www.streamlit.io/).
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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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Lindner, S., Latoschik, M.-E., Rittner, H.: Virtual Reality als Baustein in der Behandlung akuter und chronischer Schmerzen. AINS-Anästhesiologietextperiodcentered Intensivmedizintextperiodcentered Notfallmedizintextperiodcentered Schmerztherapie. 55, 549--561 (2020).
Schmerzbehandlung zählt zu den täglichen Routinen klinischer Anästhesisten. Im Rahmen eines wohlüberlegten Einsatzes von Schmerzmedikamenten sind Alternativen zur medikamentösen Schmerztherapie notwendig. Virtual Reality (VR) konnte sich in den letzten Jahren durch immer kostengünstigere und bessere Technologien als realistische Ergänzung etablieren. Möglichkeiten der VR sowie Indikationen und Kontraindikationen werden aufgezeigt.
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Korger, A., Baumeister, J.: Construction of a Corpus for the Evaluation of Textual Case-based Reasoning Architectures. LWDA 2020 -- Lernen, Wissen, Daten, Analysen (2020).
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Landeck, M., Unruh, F., Lugrin, J.-L., Latoschik, M.E.: Metachron: A framework for time perception research in VR. Proceedings of the 26th ACM Conference on Virtual Reality Software and Technology (2020).
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Donnermann, M., Schaper, P., Lugrin, B.: Integrating a Social Robot in Higher Education – A Field Study. 29th IEEE International Symposium on Robot and Human Interactive Communication. S. 573-579 (2020).
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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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Ganal, E., Bartl, A., Westermeier, F., Roth, D., Latoschik, M.E.: Developing a Study Design on the Effects of Different Motion Tracking Approaches on the User Embodiment in Virtual Reality. In: Hansen, C., Nürnberger, A., und Preim, B. (hrsg.) Mensch und Computer 2020. Gesellschaft für Informatik e.V. (2020).
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Carolin, W., Eisenmann, M., Latoschik, M.E., Grafe, S.: CoTeach – Connected Teacher Education. In: Schwaiger, M. (hrsg.) Boosting Virtual Reality in Learning. E.N.T.E.R. (2020).
CoTeach develops and evaluates innovative teaching and learning contexts for student teachers and scholars. One work package couples the potential of VR with principles of intercultural learning to create tangible experiences with pedagogically responsible value
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Casas, P., Ben Houidi, Z., Wassermann, S., Huet, A., Seufert, M., Wehner, N., Schüler, J., Cai, S.-M., Shi, H., Xu, J., Hoßfeld, T., Rossi, D.: Are you on Mobile or Desktop? On the Impact of End-User Device on Web QoE Inference from Encrypted Traffic. 16th International Conference on Network and Service Management (CNSM). , Izmir, Turkey (2020).
Web browsing is one of the key applications of the Internet, if not the most important one. We address the problem of Web Quality of Experience (QoE) monitoring from the ISP perspective, relying on in-network, passive measurements. As a proxy to Web QoE, we focus on the analysis of the well-known SpeedIndex (SI) metric. Given the lack of app-level data visibility introduced by the wide adoption of end-to-end encryption, we resort to machine-learning models to infer the SI and the QoE level of individual web page loading sessions, using as input only packet- and flow-level data. Our study targets the impact of different end-user device types (e.g., smartphone, desktop, tablet) on the performance of such models. Empirical evaluations on a large, multi-device, heterogeneous corpus of Web QoE measurements for top popular websites demonstrate that the proposed solution can infer the SI as well as estimate QoE ranges with high accuracy, using either packet-level or flow-level measurements. In addition, we show that the device type adds a strong bias in the feasibility of these Web QoE models, putting into question the applicability of previously conceived approaches on single-device measurements. To improve the state of affairs, we conceive cross-device generalizable models operating at both packet and flow levels, offering a feasible solution for Web QoE monitoring in operational, multi-device networks. To the best of our knowledge, this is the first study tackling the analysis of Web QoE from encrypted network traffic in multi-device scenarios.
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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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Hoßfeld, T., Heegaard, P.E., Skorin-Kapov, L., Varela, M.: Deriving QoE in systems: from fundamental relationships to a QoE‑based Service‑level Quality Index. Springer Quality and User Experience. 5, https://rdcu.be/b483m (2020).
With Quality of Experience (QoE) research having made significant advances over the years, service and network providers aim at user-centric evaluation of the services provided in their system. The question arises how to derive QoE in systems. In the context of subjective user studies conducted to derive relationships between influence factors and QoE, user diversity leads to varying distributions of user rating scores for different test conditions. Such models are commonly exploited by providers to derive various QoE metrics in their system, such as expected QoE, or the percentage of users rating above a certain threshold. The question then becomes how to combine (a) user rating distributions obtained from subjective studies, and (b) system parameter distributions, so as to obtain the actual observed QoE distribution in the system? Moreover, how can various QoE metrics of interest in the system be derived? We prove fundamental relationships for the derivation of QoE in systems, thus providing an important link between the QoE community and the systems community. In our numerical examples, we focus mainly on QoE metrics. We furthermore provide a more generalized view on quantifying the quality of systems by defining a QoE-based Service-level Quality Index. This index exploits the fact that quality can be seen as a proxy measure for utility. Following the assumption that not all user sessions should be weighted equally, we aim to provide a generic framework that can be utilized to quantify the overall utility of a service delivered by a system.
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Glémarec, Y., Lugrin, J.-L., Bosser, A.-G., Cagniat, P., Buche, C., Latoschik, M.E.: Pushing Out the Classroom Walls: A Scalability Benchmark for a Virtual Audience Behaviour Model in Virtual Reality. (2020).
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Seufert, M., Wehner, N., Wieser, V., Casas, P., Capdehourat, G.: Mind the (QoE) Gap: On the Incompatibility of Web and Video QoE Models in the Wild. 16th International Conference on Network and Service Management (CNSM). , Izmir, Turkey (2020).
Education Service Providers (ESPs) have a paramount role in the digitization of education, providing reliable devices for students and teachers and high quality Internet access at schools. Education Service Providers (ESPs) have a paramount role in the digitization of education, providing reliable devices for students and teachers and high quality Internet access at schools. In this paper, a large-scale, passive, in-device Quality of Experience (QoE) monitoring system is presented, which was deployed into a nationwide network of education-purpose devices. Four months' worth of continuous measurements were conducted by an ESP, covering more than 800 education centers and about 4000 devices, used both in schools and at home. When analyzing the QoE of web sessions in school networks, we identify a fundamental issue with the compatibility of web browsing and video QoE models, which inhibits the successful application of QoE-aware network management for multiple services.
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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.: 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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Davidson, P., Düking, P., Zinner, C., Sperlich, B., Hotho, A.: Smartwatch-Derived Data and Machine Learning Algorithms Estimate Classes of Ratings of Perceived Exertion in Runners: A Pilot Study. Sensors. (2020).
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Schlör, D., Ring, M., Hotho, A.: iNALU: Improved Neural Arithmetic Logic Unit. Frontiers in Artificial Intelligence. 3, 71 (2020).
Neural networks have to capture mathematical relationships in order to learn various tasks. They approximate these relations implicitly and therefore often do not generalize well. The recently proposed Neural Arithmetic Logic Unit (NALU) is a novel neural architecture which is able to explicitly represent the mathematical relationships by the units of the network to learn operations such as summation, subtraction or multiplication. Although NALUs have been shown to perform well on various downstream tasks, an in-depth analysis reveals practical shortcomings by design, such as the inability to multiply or divide negative input values or training stability issues for deeper networks. We address these issues and propose an improved model architecture. We evaluate our model empirically in various settings from learning basic arithmetic operations to more complex functions. Our experiments indicate that our model solves stability issues and outperforms the original NALU model in means of arithmetic precision and convergence.
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Fischer, E., Zoller, D., Dallmann, A., Hotho, A.: Integrating Keywords into BERT4Rec for Sequential Recommendation. KI 2020: Advances in Artificial Intelligence (2020).
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Supervisor: Seufert, A.: Evaluating the Influence of the Measurement Design on Mobile Video Streaming Behavior, (2020).
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Münster, S., Maiwald, F., Lehmann, C., Lazariv, T., Hofmann, M., Niebling, F.: An Automated Pipeline for a Browser-Based, City-Scale Mobile 4D VR Application Based on Historical Images. Proceedings of the 2nd Workshop on Structuring and Understanding of Multimedia HeritAge Contents. S. 33–40. Association for Computing Machinery, Seattle, WA, USA (2020).
The process for automatically creating 3D city models from contemporary photographs and visualizing them on mobile devices is now well established, but historical 4D city models are more challenging. The fourth dimension here is time. This article describes an automated VR pipeline based on historical photographs and resulting in an interactive browser-based device-rendered 4D visualization and information system for mobile devices. Since the pipeline shown is currently still under development, initial results for stages of the process will be shown and assessed for accuracy and usability.
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Wehner, N., Seufert, M., Schüler, J., Wassermann, S., Casas, P., Hoßfeld, T.: Improving Web QoE Monitoring for Encrypted Network Traffic through Time Series Modeling. ACM SIGMETRICS Performance Evaluation Review. (2020).
This paper addresses the problem of Quality of Experience (QoE) monitoring for web browsing. In particular, the inference of common Web QoE metrics such as Speed Index (SI) is investigated. Based on a large dataset collected with open web-measurement platforms on different device-types, a unique feature set is designed and used to estimate the RUMSI -- an efficient approximation to SI, with machine-learning based regression and classification approaches. Results indicate that it is possible to estimate the RUMSI accurately, and that in particular, recurrent neural networks are highly suitable for the task, as they capture the network dynamics more precisely.
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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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Wehner, N.: Inferring Web QoE with Machine Learning from Encrypted Network Traffic. , 2nd KuVS Workshop on Machine Learning for Networking, Würzburg, Germany (2020).
In this work, the problem of Quality of Experience (QoE) monitoring of web browsing is addressed. In particular, the inference of common Web QoE metrics like RUMSI with machine learning is investigated. Based on a large dataset collected with WebPageTest on three different devices, a unique feature set is used to approximate Web QoE metrics with regression and classification approaches. This work highlights work in progress.
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Wehner, N.: Scoring High: Analysis and Prediction of Viewer Behavior and Engagement in the Context of 2018 FIFA WC Live Streaming. , Proceedings of the 28th ACM International Conference on Multimedia (MM), Seattle, WA, USA (2020).
Large-scale events pose severe challenges to live video streaming service providers, who need to cope with high, peaking viewer numbers and the resulting fluctuating resource demands, keeping high levels of Quality of Experience (QoE) to avoid end-user frustration and churn. In this paper, we analyze a unique dataset consisting of more than a million 2018 FIFA World Cup mobile live streaming sessions, collected at a large national public broadcaster. Different from previous work, we analyze QoE and user engagement as well as their interaction, in dependency to specific soccer match events, which have the potential to trigger flash crowds during a match. Flash crowds are a particular challenge to video service providers, since they cause sudden load peaks and consequently, the likelihood of quality problems. We further exploit the data to model viewer engagement over the course of a soccer match, and show that client counts follow very similar patterns of change across all matches. We believe that the analysis as well as the resulting models are valuable sources of insight for service providers, equipping them with tools for customer-centric resource and capacity management.
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Wehner, N., Seufert, M., Schüler, J., Wassermann, S., Casas, P., Hoßfeld, T.: Improving Web QoE Monitoring for Encrypted Network Traffic through Time Series Modeling. WAIN - Workshop on AI in Networks and Distributed Systems. , Milan, Italy (2020).
This paper addresses the problem of Quality of Experience (QoE) monitoring for web browsing. In particular, the inference of common Web QoE metrics such as Speed Index (SI) is investigated. Based on a large dataset collected with open web-measurement platforms on different device-types, a unique feature set is designed and used to estimate the RUMSI -- an efficient approximation to SI, with machine-learning based regression and classification approaches. Results indicate that it is possible to estimate the RUMSI accurately, and that in particular, recurrent neural networks are highly suitable for the task, as they capture the network dynamics more precisely.
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Schüler, J.: QoE Montitoring of HTTP Adaptive Video Streaming on 100Gbps-P4-Switches, (2020).
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Roth, D., Latoschik, M.E.: Construction of the Virtual Embodiment Questionnaire (VEQ). IEEE Transactions on Visualization and Computer Graphics. 1-1 (2020).
User embodiment is important for many virtual reality (VR) applications, for example, in the context of social interaction, therapy, training, or entertainment. However, there is no data-driven and validated instrument to empirically measure the perceptual aspects of embodiment, necessary to reliably evaluate this important phenomenon. To provide a method to assess components of virtual embodiment in a reliable and consistent fashion, we constructed a Virtual Embodiment Questionnaire (VEQ). We reviewed previous literature to identify applicable constructs and questionnaire items, and performed a confirmatory factor analysis (CFA) on the data from three experiments (N = 196). The analysis confirmed three factors: (1) ownership of a virtual body, (2) agency over a virtual body, and (3) the perceived change in the body schema. A fourth study (N = 22) was conducted to confirm the reliability and validity of the scale, by investigating the impacts of latency and latency jitter present in the simulation. We present the proposed scale and study results and discuss resulting implications.
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Aliev, E.: Evaluation of the Impact of Cross-Traffic on TCP and QUIC Video Streaming and Web Browsing, (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: Wamser, F.: Analyse von Video Streaming-Konzepten, (2020).
In dieser Arbeit sollen aktuelle Streaming-Lösungen auf verschiedene Leistungscharakterisierungen und Einstellungen hin geprüft werden. Es sollen Streaming-Platformen gemessen und analysiert werden. Weitere Details auf Anfrage. Bitte direkt bei mir melden! Florian
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Gall, D., Preßler, J., Hurtienne, J., Latoschik, M.E.: Self-organizing knowledge management might improve the quality of person-centered dementia care: A qualitative study. International Journal of Medical Informatics. 139, 104132 (2020).
Background: In institutional dementia care, person-centered care improves care processes and the quality of life of residents. However, communication gaps impede the implementation of person-centered care in favor of routinized care. Objective: We evaluated whether self-organizing knowledge management reduces communication gaps and improves the quality of person-centered dementia care. Method: We implemented a self-organizing knowledge management system. Eight significant others of residents with severe dementia and six professional caregivers used a mobile application for six months. We conducted qualitative interviews and focus groups afterward. Main findings: Participants reported that the system increased the quality of person-centered care, reduced communication gaps, increased the task satisfaction of caregivers and the wellbeing of significant others. Conclusions: Based on our findings, we develop the following hypotheses: Self-organizing knowledge management might provide a promising tool to improve the quality of person-centered care. It might reduce communication barriers that impede person-centered care. It might allow transferring content-maintaining tasks from caregivers to significant others. Such distribution of tasks, in turn, might be beneficial for both parties. Furthermore, shared knowledge about situational features might guide person-centered interventions.
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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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Raffeck, S.: Towards Modeling Energy Performance of LoRaWAN Transmissions: A Verification of Theoretical Predictions, (2020).
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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).
Stereoscopic rendering is a prominent feature of virtual reality ap- plications to generate depth cues and to provide depth perception in the virtual world. However, straight-forward stereo rendering methods usually are expensive since they render the scene from two eye-points which in general doubles the frame times. This is particularly problematic since virtual reality sets high requirements for real-time capabilities and image resolution. Hence, this paper presents a hybrid rendering system that combines classic rasteriza- tion and real-time ray-tracing to accelerate stereoscopic rendering. The system reprojects the pre-rendered left half of the stereo image pair into the right perspective using a forward grid warping technique and identifies resulting reprojection errors, which are then efficiently resolved by adaptive real-time ray-tracing. A final analysis shows that the system achieves a significant performance gain, has a neg- ligible quality impact, and is suitable even for higher rendering resolutions.
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Janiak, L.: Potential Traffic Savings by Leveraging Proximity of Communication Groups in Mobile Messaging Applications, (2020).
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Dworschak, N.-D.: Evaluating Temporal Impairments in Music Streaming, (2020).
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Supervisor: Metzger, F.: Measuring the Effectiveness of Latency Mitigation Methods with a Prototype Video Game, (2020).
Video games with a competitive multiplayer modes must deal with the troubles of high and varying end-to-end lag. They can employ varying methods to manage, mitigate or conceal this lag and equalize it between different clients. But the closed source nature of video games makes examining the effectiveness of these mechanisms hard. Your job is to implement a simple video game prototype from scratch that uses an authoritative client-server multiplayer approach and implements such lag mitigation mechanisms. With this prototype we want to get a better understanding of the effectiveness of these lag concealment measures.
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Supervisor: Metzger, F.: Examining the Netcode of Old, Open-sourced Video Games, (2020).
Video games have a long history of often competitive multiplayer modes, supported by various network implementations in their engines. The source code of many of these games has been open sourced over the years, opening their netcode up for examination. Your job is to extract the netcode from some of these games and compare them to each other. We want to find out, how the employed mechanisms have changed over time and how well they would fare in today's environment.
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Supervisor: Wamser, F.: Blockchain in cloud and communication networks, (2020).
Das Ziel der Masterarbeit ist der Entwurf einer Methodik für die Ressourcenvergabe mittels Distributed Ledger-Verfahren (DLV) (Blockchain) im Netzwerk- und Anwendungsumfeld von Internetdiensten. Ein Beispiel für eine solche Ressourcenvergabe ergibt sich für aktuelle Webdienste wie Netflix. Netflix stellt seinen Dienst aus zahlreichen Einzelkomponenten zusammen: beispielsweise dem Videoplayer und den Videoinhalten. Diese Elemente liegen und werden in verschiedenen Clouds ausgeführt. Netflix muss sich Ressourcen bei verschiedenen Anbietern "zusammenkaufen". Solch ein zusammengestellter Dienst braucht einen Verteilungsalgorithmus, der Komponenten auf Clouds zuordnet. Die Idee in der Arbeit ist zu prüfen in wie fern man Blockchain hierfür nutzen kann, um Ressourcen zu buchen. Aufgaben in der Arbeit wären der Aufbau eines experiementellen Blockchain-Testbeds.
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Supervisor: Metzger, F.: Designing a Realistic Virtual AQM Testbench, (2020).
Many new queue management techniques and supporting technologies are currently being developed, standardized and rolled out. CoDel, Cake, PIE, DualPI just to name a few. Your job is to develop a portable virtual environment that allows for realistic tests and comparisons of these methods with automated test suits.
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Supervisor: Grigorjew, A.: Configuring Stream Aggregates with Timed Gates for Predictable Latency in Dynamic Networks, (2020).
Time Synchronization and Timed Gates provide a popular mechanism for extremely low deterministic latency in Time-Sensitive Networking. Achieving the lowest latencies possible requires complex per-stream configuration and network-wide knowledge. This type of preparation is not possible in dynamic networks with varying traffic requirements and changing traffic patterns. This work is focused on the preparation of aggregate schedules that prepare time slots for a specific amount of traffic beforehand, which can be dynamically used by streams during the operation of the network. The challenges include the modeling of dynamic network requirements and, based on that, an optimal configuration of the number and length of transmission windows for each priority of this aggregate scheduling model.
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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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Supervisor: Grigorjew, A.: Configuring Stream Aggregates with Asynchronous Traffic Shaping for Lower Latency, (2020).
In Time-Sensitive Networking, Asynchronous Traffic Shaping (ATS) provides a per-stream shaping mechanism that lowers the worst case per-hop latency impact of interfering traffic. However, due to the per-stream reshaping of traffic at every hop, serialization benefits on high-bandwidth links cannot be utilized. Aggregating multiple streams into a single shaper state reduces their bursty impact and can possibly provide better latency guarantees. This thesis is designed around the idea of aggregate configuration, i.e., when do the benefits justify the extra configuration, and how does aggregate shaping influence the subsequent hops on the streams' paths.
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Supervisor: Seufert, A.: QoE Estimation of Music Streaming in the Network, (2020).
Streaming made a lasting effect on the way our society consumes media in the last decade. While due to streaming the way we listen to music and podcasts has changed drastically, there are very few studies about its Quality of Experience (QoE) and how to predict the QoE under different network conditions. From subjective studies, we know that, for example, undesirable stops of the stream (stalling events) have a significant impact on QoE. This work focus on the estimation of the occurrence of such impact factors and thus, the QoE of the stream. The prediction is based on music streaming network traffic, which is typically encrypted. To collect data, a measurement framework will be set up and crowdsourcing studies will be conducted. Different monitoring methods will be applied (such as model-based or machine-learning-based monitoring) and their performance for estimating the QoE of music streaming will be evaluated. Contact: anika.seufert@informatik.uni-wuerzburg.de
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Davidson, P., Steininger, M., Lautenschlager, F., Kobs, K., Krause, A., Hotho, A.: Anomaly Detection in Beehives using Deep Recurrent Autoencoders. Proceedings of the 9th International Conference on Sensor Networks (SENSORNETS 2020). S. 142-149. SCITEPRESS – Science and Technology Publications, Lda. (2020).
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Supervisor: Geissler, S.: Classification of IoT Signaling Incidents, (2020).
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Wehner, N., Mertinat, N., Seufert, M., Hoßfeld, T.: Studying the Impact of the Content Selection Method on the Video QoE on Mobile Devices. 12th International Conference on Quality of Multimedia Experience (QoMEX). , Athlone, Ireland (2020).
When conducting video QoE studies, participants are usually asked to rate the QoE of prepared test videos. However, participants are given no choice to select content, which they like or in which they are interested. This may cause annoyance or frustration when conducting the QoE study, which eventually might affect the QoE results of the study. The consequent question is whether the content liking has a direct impact on the submitted ratings by the participants and whether the freedom of choosing the video content in QoE studies results in better ratings. To investigate this research question, MCA, an existing framework for crowdsourced video testing, is extended and used in a pilot field study. MCA runs on mobile devices and allows users to watch the tested conditions of a QoE study within video content of their interest. The results of a QoE study with individual and dynamic content selection are compared to a QoE study with pre-selected contents. Moreover, this work includes a comparison to a previous QoE study for validation. As the previous study was conducted on desktop PCs, the MCA study further allows to identify differences in the stalling perception between studies on desktop PCs and mobile devices.
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Supervisor: Loh, F.: Studying the Live Streaming Behavior of Mobile Twitch.tv and YouTube, (2020).
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Supervisor: Wehner, N.: Deep Learning for QoE Estimation, (2020).
Contact/Kontakt: nikolas.wehner@uni-wuerzburg.de Auch als Praktikum verfügbar.
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Supervisor: Wehner, N.: Implementation of a Low Latency QoE Fair HAS Logic, (2020).
Contact: nikolas.wehner@uni-wuerzburg.de Abstract: Nowadays, basically all videos are streamed via HTTP Adaptive Streaming (HAS). An important concept in terms of HAS is the Quality of Experience (QoE), which describes how users perceive video streaming. QoE fairness extends the concept of QoE by comparing the QoE of mutliple clients in a shared network. An important component influencing the QoE and consequently the QoE fairness is the HAS adaptation logic, which is responsible for downloading the segments with the goal to obtain the best possible video quality without causing stalling, i.e., playback interruption due to buffer underrun. The goal of this work is to implement an adaptation logic, currently implemented in a simulation, into a real video player and evaluating the QoE and QoE fairness of the adaptation logic when confronted with low-latency situations in real scenarios.
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Schwind, A., Moldovan, C., Janiak, T., Dworschak, N.-D., Hoßfeld, T.: Don’t Stop the Music: Crowdsourced QoE Assessment of Music Streaming with Stalling. 12th International Conference on Quality of Multimedia Experience (QoMEX). , Athlone, Ireland (2020).
Streaming made a lasting effect on the way our society consumes media in the last decade. While due to streaming the way we listen to music and podcasts has changed drastically, there are very few studies about its Quality of Experience (QoE) and possible influence factors. From video QoE studies, we know that, for example, undesirable stops of the stream (stalling events) have a significant impact on QoE. However, the way in which music and video streaming is consumed differs significantly, as music is often played in the background, and thus, the influence of stalling could be significantly different. Thus, this work evaluates the impact of stalling on music streaming QoE. Therefore, we conduct two crowdsourced user studies: In the first study, users have to rate four songs with different stalling patterns and evaluate the degree of impairments. Afterwards, we compare the ratings to the results of a lab study and show that they are highly correlated, and that crowdsourcing is a suitable way of measuring music streaming QoE. In addition, we conduct a second crowdsourcing study to investigate the influence of the user's attentiveness on QoE. Here, participants have to listen to one song with two stalling events, while one half of them had to transcribe a handwritten text with music playing in the background. The attentiveness shows no influence on the perceived streaming quality, but it shows a significant influence on the perceived quality degradation due to stalling events. Furthermore, considerably more stalling events were missed for workers who focused on the transcription. These results are an important step towards establishing new methods for investigating QoE in multimedia.
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Spoerhase, J., Storandt, S., Zink, J.: Simplification of Polyline Bundles. Proc. 17th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT'20) (2020).
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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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Mal, D.: [DC] The Impact of Social Interactions on an Embodied Individual’s Self-perception in Virtual Environments. 2020 IEEE Conference on Virtual Reality and 3D User Interfaces Abstracts and Workshops (VRW). S. 545-546. IEEE, Atlanta, GA, USA, 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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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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Peng, D., Wolff, A., Haunert, J.-H.: Finding Optimal Sequences for Area Aggregation---A\($^\star$\) vs. Integer Linear Programming. ACM Transactions on Spatial Algorithms and Systems. 7, (2020).
To provide users with maps of different scales and to allow them to zoom in and out without losing context, automatic methods for map generalization are needed. We approach this problem for land-cover maps. Given two land-cover maps at two different scales, we want to find a sequence of small incremental changes that gradually transforms one map into the other. We assume that the two input maps consist of polygons, each of which belongs to a given land-cover type. Every polygon on the smaller-scale map is the union of a set of adjacent polygons on the larger-scale map. par In each step of the computed sequence, the smallest area is merged with one of its neighbors. We do not select that neighbor according to a prescribed rule but compute the whole sequence of pairwise merges at once, based on global optimization. We have proved that this problem is NP-hard. We formalize this optimization problem as that of finding a shortest path in a (very large) graph. We present the A\($^\star$\) algorithm and integer linear programming to solve this optimization problem. To avoid long computing times, we allow the two methods to return non-optimal results. In addition, we present a greedy algorithm as a benchmark. We tested the three methods with a dataset of the official German topographic database ATKIS. Our main result is that A\($^\star$\) finds optimal aggregation sequences for more instances than the other two methods within a given time frame.
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Plesker, F.: Simulation of a 5G Network Infrastructure, (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., 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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Firman, O., Felsner, S., Kindermann, P., Ravsky, A., Wolff, A., Zink, J.: The Complexity of Finding Tangles. In: Chaplick, S., Kindermann, P., und Wolff, A. (hrsg.) Proc. 36th European Workshop on Computational Geometry (EuroCG'20). S. 67:1--8 (2020).
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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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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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Byrka, J., Lewandowski, M., Spoerhase, J.: Approximating Node-Weighted k-MST on Planar Graphs. Theory of Computing Systems. (2020).
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Hildebrand, K.: Impact of Rendering Times on the Perceived Loading Speed of Web Pages, (2020).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de Title: Impact of Rendering Times on the Perceived Loading Speed of Web Pages Abstract: The most dominant QoE (Quality of Experience, i.e., subjectively perceived quality) influence factor of web browsing is the page load time. However, pages do not load in a single event, but different parts of the web page are displayed at different rendering times. In this work, a study shall be conducted to investigate the impact of rendering times on the perceived loading speed of web pages. The results of the study shall be evaluated to derive recommendations for networking as well as rendering aspects of web browsing. Titel: Einfluss von Anzeigezeiten auf die wahrgenomme Ladegeschwindigkeit von Webseiten Inhalt: Der wichtigste Einflussfaktor auf die QoE (Quality of Experience, d.h. subjektiv empfundene Dienstgüte) beim Webbrowsing ist die Seitenladezeit. Jedoch laden Webseiten nicht auf einmal, sondern verschiedene Teile der Seite werden zu unterschiedlichen Zeitpunkten angezeigt. In dieser Arbeit soll eine Studie durchgeführt werden, mit der der Einfluss dieser Anzeigezeiten auf die wahrgenommene Ladegeschwindigkeit untersucht werden kann. Die Ergebnisse der Studie sollen ausgewehrtet werden, um Empfehlungen für Netzwerk- und Renderingaspekte beim Webbrowsen abzuleiten.
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Wehner, N.: 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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Supervisor: Seufert, A.: Crowdsourced Network Measurements: Evaluation and Applicability for 5G, (2020).
Contact: anika.seufert@informatik.uni-wuerzburg.de
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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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Supervisor: 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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Supervisor: 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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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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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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Kargl, J.: Analysis of QoE Aspects of 3D Point Cloud Reduction, (2020).
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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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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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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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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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Chaplick, S., Kindermann, P., Löffler, A., Thiele, F., Wolff, A., Zaft, A., Zink, J.: Stick Graphs with and without Length Constraints. Journal of Graph Algorithms & Applications. 25 pages (2020).
Stick graphs are intersection graphs of horizontal and vertical line seg- ments 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. par 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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Arseneva, E., Kleist, L., Klemz, B., Löffler, M., Schulz, A., Vogtenhuber, B., Wolff, A.: Representing Graphs by Polygons with Edge Contacts in 3D. In: Chaplick, S., Kindermann, P., und Wolff, A. (hrsg.) Proc. 36th European Workshop on Computational Geometry (EuroCG'20). S. 53:1--8 (2020).
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Walter, J., Zink, J., Baumeister, J., Wolff, A.: Layered Drawing of Undirected Graphs with Generalized Port Constraints. In: Auber, D. und Valtr, P. (hrsg.) Proc. 28th Int. Symp. Graph Drawing & Network Vis. (GD'20). Springer-Verlag (2020).
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Chaplick, S., Förster, H., Kryven, M., Wolff, A.: Drawing Graphs with Circular Arcs and Right-Angle Crossings. In: Albers, S. (hrsg.) Proc. 17th Scand. Symp. and Workshops on Algorithm Theory (SWAT'20). S. 21:1--21:14. Schloss Dagstuhl~-- Leibniz-Zentrum für Informatik (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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Chaplick, S., van Dijk, T.C., Kryven, M., Park, J.-W., Ravsky, A., Wolff, A.: Bundled Crossings Revisited. Journal of Graph Algorithms & Applications. 35 pages (2020).
An effective way to reduce clutter in a graph drawing that has (many) crossings is to group edges that travel in parallel into bundles. Each edge can participate in many such bundles. Any crossing in this bundled graph occurs between two bundles, i.e., as a bundled crossing. We consider the problem of bundled crossing minimization: A graph is given and the goal is to find a bundled drawing with at most \($k$\) bundled crossings. We show that the problem is NP-hard when we require a simple drawing. Our main result is an FPT algorithm (in \($k$\)) for simple circular layouts where vertices must be placed on a circle and edges must be drawn inside the circle. These results make use of the connection between bundled crossings and graph genus. We also consider bundling crossings in a given drawing, in particular for storyline visualizations.
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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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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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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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Berani, S.: Fingerprinting Websites in Encrypted Network Traffic, (2020).
Contact/Kontakt: nikolas.wehner@informatik.uni-wuerzburg.de Auch als Praktikum verfügbar. 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 afterward they have to be ingested into selected Machine Learning algorithms.
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Fehler, H.: Comparison of Web QoE Algorithms on Different Devices, (2020).
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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Furdek, M., Natalino, C., Lipp, F., Hock, D., Di Giglio, A., Schiano, M.: Machine Learning for Optical Network Security Monitoring: A Practical Perspective. Journal of Lightwave Technology. 38, 2860--2871 (2020).
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Halloway, M.: Evaluating the QoE of Music Streaming Applications, (2020).
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Supervisor: Seufert, A.: Investigating the QoE of Mobile Instant Messaging, (2020).
WhatsApp is one of the most popular mobile instant messaging (MIM) applications. Due to MIM applications, the way we communicate has changed drastically. Nevertheless, there are very few studies about its Quality of Experience (QoE) and possible influence factors. Thus, the goal of this work is to evaluate the QoE MIM apps. Therefore, a web MIM application will be designed to simulate different possible influence factors on the QoE (e.g., image load times). Afterwards, a subjective user study will be conducted and QoE ratings on the simulated degradation will be collected and evaluated. Contact: anika.seufert@informatik.uni-wuerzburg.de
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Walter, J., Zink, J., Baumeister, J., Wolff, A.: Layered Drawing of Undirected Graphs with Generalized Port Constraints. 28th International Symposium on Graph Drawing and Network Visualization (GD 2020) (2020).
The aim of this research is a practical method to draw cable plans of complex machines. Such plans consist of electronic components and cables connecting specific ports of the components. Since the machines are configured for each client individually, cable plans need to be drawn automatically. The drawings must be well readable so that technicians can use them to debug the machines. In order to model plug sockets, we introduce port groups; within a group, ports can change their position (which we use to improve the aesthetics of the layout), but together the ports of a group must form a contiguous block. We approach the problem of drawing such cable plans by extending the well-known Sugiyama framework such that it incorporates ports and port groups. Since the framework assumes directed graphs, we propose several ways to orient the edges of the given undirected graph. We compare these methods experimentally, both on real-world data and synthetic data that carefully simulates real-world data. We measure the aesthetics of the resulting drawings by counting bends and crossings. Using these metrics, we compare our approach to Kieler [JVLC 2014], a library for drawing graphs in the presence of port constraints.
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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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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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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: 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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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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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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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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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.
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Lugrin, J.-L., Kern, F., Kleinbeck, C., Roth, D., Daxery, C., Feiglz, T., Mutschlery, C., Latoschik, M.E.: A Framework for Location-Based VR Applications. Proceedings of the GI VR/AR - Workshop (2019).
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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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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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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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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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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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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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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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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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Simonovski, F.: Studying the Video Segmentation for different Streaming Platforms, (2019).
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Gray, N., Grigorjew, A., Hoßfeld, T., Shukla, A., Zinner, T.: Gray, Nicholas, et al. "Highlighting the Gap Between Expected and Actual Behavior in P4-enabled Networks. IFIP/IEEE Symposium on Integrated Network and Service Management (IM) (2019).
Modern networks increasingly rely on Software-defined Networking (SDN) and Network Function Virtualization (NFV) to augment their flexibility in high load scenarios. To further enhance the performance, a part of the functionality is often offloaded to forwarding devices, which are used as hardware accelerators and are configured by high level programming languages such as P4. However, hardware vendors use sophisticated technologies to implement these standards, which need to be understood by the programmer to avoid unintended behavior. In this demonstration we highlight the severe consequences of only relying on the network programming language when ignoring the device-specific limitations. We show this by the example of a Denial of Service attack against a P4-enabled SmartNIC. Finally, we discuss possible mitigations to this attack and stress the importance of an overall understanding of the entire system.
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Orsolic, I., Skorin-Kapov, L., Hoßfeld, T.: To Share or Not to Share? How Exploitation of Context Data Can Improve In-Network QoE Monitoring of Encrypted YouTube Streams. 2019 Eleventh International Conference on Quality of Multimedia Experience (QoMEX) (QoMEX 2019) (2019).
With the widespread use of encryption in Over the Top (OTT) traffic, Internet Service Providers (ISPs) for the most part lack insights into application performance, as well as into Quality of Experience (QoE) perceived by end users. Addressing challenges related to encryption, ISPs are looking into machine learning based solutions that can detect application performance solely from statistical properties of the traffic. On the other hand, OTT service providers are not willing to share service performance and content-related information with ISPs. While related work on OTT-ISP collaboration scenarios has addressed architectural aspects, business models, and to a certain extent incentives for sharing data, the focus of this paper is on the exchanged data itself. We investigate to what extent the performance of in-network machine learning based QoE estimation models for HTTP adaptive video streaming could be improved with the availability of certain context data provided by OTT providers. We motivate OTT-ISP collaboration through more accurate in-network QoE monitoring and potential improvement of user experience, which is of interest to both sides.
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Hirth, M., Borchert, K., Allendorf, F., Metzger, F., Hoßfeld, T.: Crowd-based Study of Gameplay Impairments and Player Performance in DOTA 2. 4th Internet-QoE Workshop: QoE-based Analysis and Management of Data Communication Networks (Internet-QoE'19). , Los Cabos, Mexico (2019).
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Oberdörfer, S., Latoschik, M.E.: Predicting Learning Effects of Computer Games Using the Gamified Knowledge Encoding Model. Entertainment Computing. 32, 100315 (2019).
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Roth, D., Brübach, L., Westermeier, F., Schell, C., Feigl, T., Latoschik, M.E.: A Social Interaction Interface Supporting Affective Augmentation Based on Neuronal Data. Symposium on Spatial User Interaction (SUI '19), October 19--20, 2019, New Orleans, LA, USA (2019).
In this demonstration we present a prototype for an avatar-mediated social interaction interface that supports the replication of head- and eye movement in distributed virtual environments. In addition to the retargeting of these natural behaviors, the system is capable of augmenting the interaction based on the visual presentation of affective states. We derive those states using neuronal data captured by electroencephalographic (EEG) sensing in combination with a machine learning driven classification of emotional states.
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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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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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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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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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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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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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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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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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Leidinger, F.: Studing the Initial Delay of the YouTube Mobile App with TensorFlow, (2019).
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Schmitt, J., Lugrin, J.-L., Carolin, and W., Latoschik, M.E.: Investigating Gesture-based Commands for First-Person Shooter Games in Virtual Reality. Proceedings of User-embodied Interaction in Virtual Reality, Mensch und Computer 2019 (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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Biskup, F.: IoT-Datenanalyse im Smart City-Kontext, (2019).
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Borchert, K., Hirth, M., Stellzig-Eisenhauer, A., Kunz, F.: Crowd-based Assessment of Deformational Cranial Asymmetries. International Workshop on Crowd-Powered e-Services (CROPS). , Trondheim, Norway (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). S. 409--415. Springer-Verlag (2019).
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Nogatz, F., Körner, P., Krings, S.: Prolog Coding Guidelines: Status and Tool Support. Technical Communications of the 35th International Conference on Logic Programming (ICLP) (2019).
The importance of coding guidelines is generally accepted throughout developers of every programming language. Naturally, Prolog makes no exception. However, establishing coding guidelines is fraught with obstacles: Finding common ground on kind and selection of rules is matter of debate; once found, adhering to or enforcing rules is complicated as well, not least because of Prolog’s flexible syntax without keywords. In this paper, we evaluate the status of coding guidelines in the Prolog community and discuss to what extent they can be automatically verified. We implemented a linter for Prolog and applied it to several packages to get a hold on the current state of the community.
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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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Haberzettl, L.: QoS Assessments of Spotify’s Mobile Application for Audio Streaming, (2019).
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Löffler, D., Tscharn, R., Schaper, P., Hollenbach, M., Mocke, V.: Tight Times: Semantics and Distractibility of Pneumatic Compression Feedback for Wearable Devices. Proceedings of Mensch und Computer 2019. ACM (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). S. 18--32. Springer-Verlag (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). S. 216--229. Springer-Verlag (2019).
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Wolff, A., Arseneva, E., de Mesmay, A., Kleist, L., Klemz, B., Löffler, M., Schulz, A., Vogtenhuber, B.: Representing Graphs by Polygons with Edge Contacts in 3D, https://drops.dagstuhl.de/opus/volltexte/2019/11773, (2019).
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Schulz, A., Wolff, A.: Survey on Graph and Hypergraph Drawing, (2019).
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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 Debriefung in Medical Training: A Feasibility Study. Proceedings of the Human Factors and Ergonomics Society Annual Meeting. S. 733-737 (2019).
Simulation-based medical training is an increasingly used method to improve the technical and non-technical performance of clinical staff. An essential part of training is the debriefing of the participants, often using audio, video, or even eye tracking recordings. We conducted a practice-oriented feasibility study to test an eye tracking data preparation procedure, which automatically provided information about the gaze distribution on areas of interest such as the vital sign monitor or the patient simulator. We acquired eye tracking data during three simulation scenarios and provided gaze distribution data for debriefing within 30 minutes. Additionally, we qualitatively evaluated the usefulness of the generated eye tracking data for debriefings. Participating students and debriefers were mostly positive about the data provided; however, future research should improve the technical side of the procedure and investigate best practices regarding how to present and use the data in debriefings.
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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). S. 63--77. Springer-Verlag (2019).
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Haunert, J.-H., Akitaya, H., Cornelsen, S., Kindermann, P., Mchedlidze, T., Nöllenburg, M., Okamoto, Y., Wolff, A.: Clustering Colored Points in the Plane, http://drops.dagstuhl.de/opus/volltexte/2019/11380/, (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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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). S. 430--443. Springer-Verlag (2019).
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Fabrikant, S.I., Miksch, S., Wolff, A. hrsg: Visual Analytics for Sets over Time and Space. Schloss Dagstuhl~-- Leibniz-Zentrum für Informatik (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.
