Nogatz, F., Kübert, J., Seipel, D., Abreu, S.: Alexa, how can I reason with Prolog?Proceedings of 8th Symposium on Languages, Applications, Technologies (SLATE) (2019).
Seufert, M., Wehner, N., Casas, P.: A Fair Share for All: TCP-inspired Adaptation Logic for QoE Fairness among Heterogeneous HTTP Adaptive Video Streaming Clients.IEEE Transactions on Network and Service Management.PP, (2019).
Kurak, T.: Einfluss von persönlicher Bekanntheit und Popularität eines Videos auf die QoE, (2019).
Maggi, L., Leguay, J., Seufert, M., Casas, P.: Online Detection of Stalling and Scrubbing in Adaptive Video Streaming.17th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt). , Avignon, France (2019).
Haberzettl, L.: QoS Assessments of Spotify’s Mobile Application for Audio Streaming, (2019).
Dewitz, L., Münster, S., Niebling, F.: Usability-Testing für Softwarewerkzeuge in den Digital Humanities am Beispiel von Bildrepositorien.DHd 2019 Digital Humanities: multimedial & multimodal. Konferenzabstracts, Frankfurt am Main.52-55 (2019).
Smietanka, O.: Comparison of LPWAN IoT Device Communication Techniques LoRa and NB-IoT, (2019).
Borchert, K., Schwind, A., Hirth, M., Hoßfeld, T.: In Vivo or in Vitro? Influence of the Study Design on Crowdsourced Video QoE.11th International Conference on Quality of Multimedia Experience (QoMEX) (2019).
Prantl, T.: Machine Learning for Synthetically Generated, Adaptive Streaming Data, (2019).
Ziel dieser Arbeit war es, die Einsatzmöglichkeiten maschinellen Lernens im Bereich des adaptiven Videostreamings zu analysieren und entsprechende Grundlagen zu schaffen. Insbesondere zielt die Arbeit darauf ab, im großen Stil Streaming-Daten synthetisch zu generieren, die als Eingabe für maschinelles Lernen verwendet werden können. Zu diesem Zweck beginnt die Ausarbeitung damit, Grundlagen und Verfah- ren zu erklären, sowie eine Auswahl aus verwandten Arbeiten zu treffen, um daraus wertvolle Ideen abzuleiten. Einer der wichtigsten Begriffe in diesem Zusammenhang war die Definition und Abstraktion des adaptiven Video-Streamings. Hierbei wurden verschiedene Streaming-Adapationsalgorithmen modelliert und neu implementiert, die die Bitrate für die Filmsegemente, die sogenannten Chunks, bestimmen. Ähnlich wichtig war der Begriff der Quality of Experience, die im weiteren Verlauf der Ar- beit als Bewertungsmethode für das Streaming-Erlebnis beim Benutzer diente. Es wurde zu Beginn ein Überblick über die verschiedenen bekannten Verfahren aus der Literatur gegeben. Anschließend wurden die technischen Details, die möglichen Eingabeparameter und die Auswirkungen der verschiedenen Bewertungsverfahren diskutiert. Die Arbeit nutzt lediglich vorhandene QoE-Modelle aus der Literatur. Die Erstellung und Validierung von neuen QoE-Modellen ist nicht Gegenstand der aktuellen Arbeit. Im Hinblick auf verwandte Arbeiten wurden Arbeiten von Orsolic et al. und Mao et al. herangezogen. Als Ergebnis daraus wurden, mit Blick auf das geplante Vor- haben, folgende Ziele aufgstellt: einen umfangreichen Datensatz mit dem Verhalten verschiedener Adaptionsalgorithmen in stark flukturierenden Netzwerken zu generie- ren, geeignete Kombinationen von Algorithmen zu testen und einen globalen Ansatz zur Optimierung von Video-Streaming-Vorgängen mit Hilfe von Ensemble-Learning zu finden. Das erste Ziel war folglich, einen entsprechend großen inhomogenen Streaming- Datensatz für zukünftige Forschungsarbeiten bereitzustellen. Ein möglicher Ansatz bestand darin, dies mit Hilfe von synthetisch generierten Daten zu realisieren. Dazu wurde die synthetische Erzeugung von Streaming-Daten untersucht, um eine Metho- de zur schnellen Herstellung von Streaming-Daten zu erhalten. Zu diesem Zweck wur- de eine Simulation entwickelt, die das Verhalten der Adaptionsalgorithmen BBA0, FESTIVE und PANDA für ein bestimmtes Video in einem bestimmten Netzwerk, mittels eines generalisierten Modelles, berechnet. Um die Genauigkeit dieser Simu- lation zu überprüfen, wurden für jeden Algorithmus drei Streaming-Prozesse real durchgeführt und in der Simulation nachgestellt. Der Vergleich des simulierten und realen Streaming-Prozesses zeigte eine gute Übereinstimmung zwischen Simulati- on und Realität und außerdem, dass ein Adaptionsverfahren umso besser simuliert werden kann, je mehr es die zeitliche Entwicklung der Parameter berücksichtigt. Mit dem Begriff Quality of Experience (QoE) wurde eine Möglichkeit zur Bewertung der simulierten Streamingvorgänge genutzt und anschließend wurden gängige QoE-Verfahren vorgestellt, aus denen eine begründete Auswahl getroffen wurde. Um mit der Simulation möglichst viele Streaming-Daten zu erzeugen, wurde eine Toolchain für deren automatisierte Generierung vorgestellt. Die Toolchain umfasst dabei die automatische Herstellung und Konvertierung von Videos, deren Simulation durch alle vorgegebenen Netzwerke mittels der drei eingeführten Adaptionsverfah- ren sowie die Bewertung des simulierten Streamingvorganges mit Hilfe von sieben vorgegebenen unterschiedlichen QoE-Modellen. Mit dieser Toolchain wurden fast 3 Millionen Streamingprozesse generiert, die auf die einzelnen Verfahren verteilt sind. Neben der Simulation der herkömmlichen Verfahren wurde eine neue Simulati- onsmethode trainiert, welche die herkömmlichen Vorgehensweisen der Algorithmen BBA0, FESTIVE und PANDA kombiniert. Das neue Verfahren fand heraus, dass man im Schnitt die gleiche durchschnittliche QoE erhält wie das beste herkömmliche Verfahren, wenn man immer nur die zwei höchsten Bitraten wählt. Aus diesem Ver- halten ließ sich schlussfolgern, dass die Analyse der verwendeten QoE-Modelle und deren möglichst optimale Ausprägung auf dem verwendeten Datensatz essentiell für maschinelles Lernen in diesem Bereich ist. Aus diesem Grund empfiehlt diese Arbeit, dass bevor weitere maschinelle Lernver- fahren auf adaptive Streaming-Daten angewendet werden, zuerst die exsistierenden QoE-Modelle und deren Verhalten genauer untersucht werden sollten. Für diese Un- tersuchungen stellt die im Rahmen dieser Arbeit entwickelte Toolchain ein wertvolles Hilfsmittel dar, da sie die schnelle Generierung von Streaming-Daten und deren Be- wertung anhand von sieben verschiedenen QoE-Modellen ermöglicht.
Popp, C.: Measurement and Analysis of QoE Influencing Factors for WebRTC, (2019).
Web Real-Time-Communication (WebRTC) beinhaltet eine Reihe neuartiger Tech- nologien und Standards zur qualitativ hochwertigen Audio-, Video- und Datenüber- tragung zwischen Web-Nutzern und Nutzergruppen. Alles wird under der Prämisse der Echtzeitkommunikation übertragen, so dass Interaktivität ermöglicht wird, also der Dialog und Wechselbeziehung zwischen Nutzern für alle drei Arten der Übertra- gung in WebRTC. So erlaubt WebRTC hiermit das Chatten, Telefonieren, Video- Telefonieren, Screensharing, Webinars und Video-Games im Browser unabhängig von der zugrunde liegenden Hardwareplattform, sei es mit Hilfe von Web- oder mobilen Anwendungen ohne dass zusätzliche Plugins erforderlich sind. Hierfür ver- wendet WebRTC eine Kommunikationsarchitektur die Datenübertragung auf zwei Wegen ermöglicht. Eine Möglichkeit ist die Verwendung eines zentralen Servers, der vom Dienstanbieter bereitgestellt werden muss. Daten an andere Clients in der Session werden über den Server an die entsprechenden Empfänger weitergeleitet (RELAY). Die zweite Möglichkeit ist die direkte Kommunikation der Clients unter- einander (P2P). Da es aufgrund der Verwendung von Network Address Translation (NAT) und Firewalls in der Regel unmöglich ist, direkt Daten an Clients in anderen Netzwerken zu schicken, verwendet WebRTC Interactive Connectivity Establish- ment (ICE), um direkte Kommunikation zu ermöglichen. WebRTC wird vom World Wide Web Consorcium (W3C) und von der Internet Engineering Task Force (IETF) entwickelt und standardisiert. Seit der initialen Veröffentlichung im Jahr 2011 wird WebRTC von einer Vielzahl bekannter Dienste zur Bereitstellung von Echtzeitkom- munikation verwendet. Zu diesen Diensten zählen u.a. Google Hangouts, Facebook Messenger und Citrix GoToMeeting. Diese Arbeit diskutiert Einflussfaktoren auf System und Netzwerkebene, welche die Quality of Experience (QoE) im Kontext von WebRTC beeinflussen. Basierend auf der Analyse bestehender Literatur zu den Themenbereichen Echtzeitkommu- nikation und QoE wurde eine Reihe an Parametern, welche die Nutzererfahrung beeinflussen, identifiziert. Mithilfe dieser Parameter wurden drei Metafaktoren Syn- chronität, Stabilität und Qualität definiert, welche für die QoE relevant sind. Diese werden mittels Key Performance Indikatoren (KPI) näher bestimmt. Jeder KPI be- trachtet einen spezifischen Aspekt des Metafaktors, zu welchem er gehört. Um das Verhalten der Metafaktoren zu untersuchen, wurde ein Mess-Framework implemen- tiert. Dieses ermöglicht automatische und replizierbare Messungen von WebRTC- Anwendungen im Browser. Im Rahmen dieser Messungen ist es möglich, das wie- dergegebene Video, die Dauer einzelner Messungen, die Anzahl an Teilnehmern, so- wie die Sendebandbreite zu definieren. Während der Messungen werden automatisch Messdaten gesammelt. Im Anschluss werden die Daten aller Teilnehmer automatisch auf einem Kontroll-PC gesammelt und für die Weiterverarbeitung organisiert. Das Framework steht öffentlich zum herunterladen bereit. Mithilfe des Mess-Frameworks wurden mehrere Messreihen mit zwei und drei Teilnehmern durchgeführt, um QoE Einflussfaktoren für WebRTC zu analysieren und näher zu bestimmen. Während der Messreihen wurde die Bandbreite zwischen 250 kbit/s and 50 Mbit/s variiert. Die allgemeine Evaluation der Messdaten zeigt, dass bei der Analyse der Einfluss- faktoren von Nutzerzufriedenheit und QoE zwischen den verschiedenen möglichen Kommunikationsmodi unterschieden werden muss. Falls an einer Session nur zwei Teilnehmer teilnehmen, wird im Laufe der Session von RELAY zu P2P-Kommuni- kation gewechselt. Gibt es hingegen drei Teilnehmer, wird während der gesamten Session mittels RELAY kommuniziert. Dies trifft für die implementierte ICE- und WebRTC-Serverinfrastruktur mit jitsi-Server und Chrome-Browser beim Client zu. Hiermit wird die Datenmenge, welche von einem einzelnen Client gesendet werden muss, reduziert. Vergleicht man die RELAY und die P2P-Phase von einer Messung mit zwei Teilnehmern, ist auffällig, dass die RELAY-Phase unabhängig von der Netz- werkbandbreite eine konstant hohe Stabilität der erfassten Parameter aufweist. Die P2P-Phase hingegen benötigt eine gewisse Mindestbandbreite, um diese Stabilität zu erreichen. In der P2P-Phase ist die maximal erreichbare Videobitrate allerdings höher, was die Nutzerzufriedenheit laut QoE-Studien beeinflussen kann. Messungen mit drei Teilnehmern weisen ein Verhalten vergleichbar mit der RELAY Phase von Messungen mit zwei Teilnehmern auf. Im Bezug auf den Metafaktor Synchronität ist auffällig, dass für alle Phasen und sowohl mit zwei, als auch mit drei Teilnehmern, eine Mindestbandbreite von 500 kbit/s notwendig ist, um eine gute Bewertung der Synchronität zu erreichen. Eine Ausnahme hiervon bildet die Audio/Video-Synchronisation. Diese erfordert im Fall von zwei Teilnehmern eine Mindestbandbreite von 2.0 Mbit/s. Nehmen drei Cli- ents an der Messung teil, sind die erreichten Werte für die Audio/Video-Synchronität durchgängig schlechter als für zwei Clients. Der zweite Metafaktor ist Stabilität. Für diesen gibt es größere Unterschiede be- zogen auf das Verhalten von RELAY und P2P-Phase. Während der RELAY-Phase werden durchgängig hohe Werte für die verschiedenen KPIs berechnet. Die berech- neten Werte ändern sich zeitweise, allerdings sind sie dennoch konstant höher als die Werte der P2P-Phase. Bezogen auf den KPI Auflösung, liegt der Haupgrund für die schlechte Bewertung der P2P-Phase in der Art und Weise, wie die Videoauflösung an die verfügbare Bandbreite angepasst wird. Im Fall des zweiten KPIs, welcher die Videoauflösung betrachtet, zeigt die P2P-Phase ein Verhalten ähnlich zum ersten Metaparameter. Geringe Bandbreiten führen zu schlechten Werten. Mit steigender Bandbreite verbessern sich diese und bleiben nach dem Erreichen des Maximums konstant. Aufgrund des beschriebenen Verhaltens wird die Stabilität der RELAY- Phase konstant besser bewertet als die der P2P-Phase. Messungen mit zwei Teil- nehmern zeigen ein Verhalten ähnlich der RELAY-Phase von Messungen mit zwei Teilnehmern. Qualität ist der dritter Metafaktor. Unabhängig von der konfigurierten Bandbrei- te erreicht die P2P-Phase hier immer bessere Bewertungen als die RELAY-Phase, was auch im angegeben Modell in der Arbeit durch Zahlen bestätigt wird. Zwi- schen der Bewertung von Audio- und Videodaten gibt es signifikante Unterschiede. Aufgrund technischer Einschränkungen unterstützt das Messframework keine Wie- dergabe von Audio. Das führt dazu, dass automatisch eine regelmäßige Abfolge von Pieptönen wiedergegeben wird. Wir vermuten, dass dies dazu führt, dass der Audio Adaptionsmechanismus von WebRTC nicht funktioniert. Aufgrund dieser Annahme betrachten wir die Audioqualität als konstanten Faktor. Der zweite KPI, welcher die Qualität betrifft, behandelt die Videoqualität. Sofern die verfügbare Bandbrei- te größer als 2.0 Mbit/s ist, erreicht die P2P-Phase konstant bessere Werte als die RELAY-Phase. Andernfalls sind die Werte der beiden Phasen vergleichbar. Hohe Bandbreiten zeigen eine Limitierung der RELAY-Phase bezüglich der Videobitrate. Wir vermuten, dass es sich hierbei um Limitierungen handelt, welche vom Betreiber des Dienstes eingerichtet wurden. Die Messungen mit drei Teilnehmern zeigen ein ähnliches Verhalten wie die RELAY Phase, allerdings sind die maximal erreichten Bitraten pro Video geringer. Zuletzt definieren wir eine simple Abschätzungsfunktion QoE simple für die QoE von WebRTC aufgrund unserer bisherigen Analyse für die Infrastruktur unseres Frameworks. Diese ist definiert als der Durchschnitt der Metafaktoren. Die berech- neten Werte für QoE simple zeigen, dass die RELAY-Phase für geringe Bandbreiten geringfügig bessere Werte erreicht. Im Fall höherer Bandbreiten ergibt sich ein Vor- teil zugunsten der P2P-Phase. Das Modell erlaubt WebRTC-Anbietern und Provi- dern die Abschätzung der QoE über eine simple Messung von Einflussfaktoren. Die subjektive Validierung des Modells wird in einer nächsten Arbeit angegangen. Alle Metafakotoren wurden aufgrund des bisherigen Stands der Technik in der Literatur ausgewählt und eingebunden.
Münster, S., Messemer, H., Große, P., Kuroczyński, P., Niebling, F.: Das Wissen in der 3D-Rekonstruktion. In: Sahle, P. (hrsg.) DHd 2019 Digital Humanities: multimedial & multimodal. Konferenzabstracts, Frankfurt am Main. S. 63-65 (2019).
Seufert, M., Casas, P., Wehner, N., Li, G., Kuang, L.: Features that Matter: Feature Selection for On-line Stalling Prediction in Encrypted Video Streaming.2nd International Workshop on Network Intelligence (NI). , Paris, France (2019).
Seufert, M., Schatz, R., Wehner, N., Gardlo, B., Casas, P.: Is QUIC becoming the New TCP? On the Potential Impact of a New Protocol on Networked Multimedia QoE.11th International Conference on Quality of Multimedia Experience (QoMEX). , Berlin, Germany (2019).
Metzger, F., Hoßfeld, T., Bauer, A., Kounev, S., Heegaard, P.E.: Modeling of Aggregated IoT Traffic and Its Application to an IoT Cloud.Proceedings of the IEEE.107,679-694 (2019).
As the Internet of Things (IoT) continues to gain traction in telecommunication networks, a very large number of devices are expected to be connected and used in the near future. In order to appropriately plan and dimension the network, as well as the back-end cloud systems and the resulting signaling load, traffic models are employed. These models are designed to accurately capture and predict the properties of IoT traffic in a concise manner. To achieve this, Poisson process approximations, based on the Palm–Khintchine theorem, have often been used in the past. Due to the scale (and the difference in scales in various IoT networks) of the modeled systems, the fidelity of this approximation is crucial, as, in practice, it is very challenging to accurately measure or simulate large-scale IoT deployments. The main goal of this paper is to understand the level of accuracy of the Poisson approximation model. To this end, we first survey both common IoT network properties and network scales as well as traffic types. Second, we explain and discuss the Palm–Khintiche theorem, how it is applied to the problem, and which inaccuracies can occur when using it. Based on this, we derive guidelines as to when a Poisson process can be assumed for aggregated periodic IoT traffic. Finally, we evaluate our approach in the context of an IoT cloud scaler use case.
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).
Supervisor: Seufert, M.: Transfer Learning Approaches for QoE Monitoring of Encrypted Video Streaming Traffic, (2019).
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.
Seufert, M., Casas, P., Wehner, N., Li, G., Kuang, L.: Stream-based Machine Learning for Real-time QoE Analysis of Encrypted Video Streaming Traffic.3rd International Workshop on Quality of Experience Management (QoE-Management). , Paris, France (2019).
As stalling is the worst Quality of Experience (QoE) degradation of HTTP adaptive video streaming (HAS), this work presents a stream-based machine learning approach, ViCrypt, which analyzes stalling of YouTube streaming sessions in real-time from encrypted network traffic. The video streaming session is subdivided into a stream of short time slots of 1 s length, while considering two additional macro windows each for the current streaming trend and the whole ongoing streaming session. Constant memory features are extracted from the encrypted network traffic in these three windows in a stream-based fashion, and fed into a random forest model, which predicts whether the current time slot contains stalling or not. The presented system can predict stalling with a very high accuracy and the finest granularity to date (1 s), and thus, can be used in networks for real-time QoE analysis from encrypted YouTube video streaming traffic. The independent predictions for each consecutive slot of a streaming session can further be aggregated to obtain stalling estimations for the whole session. Thereby, the proposed method allows to quantify the initial delay, as well as the overall number of stalling events and the stalling ratio, i.e., the ratio of total stalling time and total playback time.
Nogatz, F., Seipel, D., Abreu, S.: Definite Clause Grammars with Parse Trees: Extension for Prolog.Proceedings of 8th Symposium on Languages, Applications, Technologies (SLATE) (2019).
Seufert, M., Wassermann, S., Casas, P.: Considering User Behavior in the Quality of Experience Cycle: Towards Proactive QoE-aware Traffic Management.IEEE Communications Letters.PP, (2019).
The concept of Quality of Experience (QoE) of Internet services is widely recognized by service providers and network operators. They strive to deliver the best experience to their customers in order to increase revenues and avoid churn. Therefore, QoE is increasingly considered as an integral part of the reactive traffic management cycle of network operators. Additionally, QoE also constitutes a cycle of its own, which includes the user behavior and the service requirements. This work describes this QoE cycle, which is not widely taken into account yet, discusses the interactions of the two cycles, and derives implications towards an improved and proactive QoE-aware traffic management. A showcase on how network operators can obtain hints on the change of network requirements from detecting user behavior in encrypted video traffic is also presented in this paper.
Tönsing, L.: Untesuchung des Einflusses der Anleitungs- und Bearbeitungssprache auf die Ergebnisqualität von Crowdsourcing-Aufgaben, (2019).
Obremski, D., Lugrin, J.-L., Schaper, P., Lugrin, B.: Non-Native Speaker Generation and Perception for Mixed-Cultural Settings.ACM International Conference on Intelligent Virtual Agents 2019. (2019).
This paper presents an experiment evaluating the effects of virtual agents' language proficiency on whether they are perceived as a native speakers or not. Our first results indicate that beyond 10% word order mistakes and 25% infinitive mistakes, virtual agents are perceived as non-native speakers, even though their appearance and non-verbal behaviour were not altered. We believe these thresholds constitute interesting guidelines possibly simplifying the design of non-native speaker simulations.
Maiwald, F., Henze, F., Bruschke, J., Niebling, F.: GEO-INFORMATION TECHNOLOGIES FOR A MULTIMODAL ACCESS ON HISTORICAL PHOTOGRAPHS AND MAPS FOR RESEARCH AND COMMUNICATION IN URBAN HISTORY.ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences.XLII-2/W11,763--769 (2019).
Moldovan, C., Wamser, F., Hoßfeld, T.: Energy-Efficient Adaptation Logic for HTTP Streaming in Mobile Networks.2019 International Conference on Networked Systems (NetSys) (2019).
The requirements for video streaming have changed drastically during the past years. In today's Internet, high definition resolutions are considered default for videos, even in mobile settings, and with 4G penetration reaching 90 percent in the US, this no longer poses a big problem. However, while mobile bandwidth has increased, the battery life time of mobile devices has not increased significantly. Furthermore, current data plans are still not large enough to regularly stream movies during the commute. Users still resort to downloading media before travel. In this paper we propose a new HTTP adaptive streaming algorithm that delivers videos in high quality while avoiding stalling events, schedules the download of video segments so that a energy conserving idle state is often reached and keeps the buffer low at points in the video where many viewers abandon the video to save data. While most adaptive streaming algorithms optimize quality and stalling, this is the first attempt to use an adaptive streaming algorithm to reduce energy consumption. Since video streaming providers mostly care about the Quality of Experience when watching videos, energy efficiency is left to the device manufacturers. Therefore, both parties have little incentive to cooperate in this regard. But on the Internet of tomorrow, where most videos are watched on mobile devices, energy efficiency and the Quality of Experience must go hand in hand.
Mizrachi, E., Schwartz, R., Spoerhase, J., Uniyal, S.: A Tight Approximation for Submodular Maximization with Mixed Packing and Covering Constraints.Proc. 46th International Colloquium on Automata, Languages and Programming (ICALP'19) (2019).
Seufert, M.: Quality of Experience and Access Network Traffic Management of HTTP Adaptive Video Streaming., International Conference on Networked Systems (NetSys), KuVS Dissertation Award 2018, Munich, Germany (2019).
Supervisor: Seufert, M.: Estimating QoE of Web Browsing in the Network, (2019).
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.
Supervisor: Seufert, M.: Algorithms Towards Proactive QoE-aware Traffic Management, (2019).
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.
Supervisor: Seufert, M.: Characterization of Browsing Sessions, (2019).
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.
Seufert, M.: QUICker or not? - an Empirical Analysis of QUIC vs TCP for Video Streaming QoE Provisioning., 3rd International Workshop on Quality of Experience Management (QoE-Management), Paris, France (2019).
Supervisor: Seufert, M.: Impact of Content Selection on Crowdsourced QoE Studies of HTTP Adaptive Streaming on Mobile Devices, (2019).
Contact/Kontakt: michael.seufert@uni-wuerzburg.de Title: Impact of Content Selection on Crowdsourced QoE Studies of HTTP Adaptive Streaming on Mobile Devices Abstract: The goal of this work is to conduct a crowdsourcing study on the Quality of Experience (QoE) of HTTP adaptive video streaming. In the study, users shall stream videos with the app CroQoE, which already exists as a prototype, and assess the QoE. It shall be investigated if there is an impact on the ratings if users can select the videos, which they stream during the study. Titel: Einfluss von Videoauswahl auf Crowdsourcing-basierte Studien zur subjektiven Dienstgüte von adaptivem HTTP Videostreaming auf mobilen Endgeräten Inhalt: Das Ziel dieser Arbeit ist es eine Crowdsourcing-basierte Studie zur subjektiven Dienstgüte bei Videostreaming durchzuführen. In der Studie sollen die Nutzer mittels einer bereits als Prototyp existierenden App CroQoE Videos streamen und die subjektive Dienstgüte bewerten. Dabei soll herausgefunden werden, ob es einen Einfluss auf die Bewertungen hat, wenn die Nutzer die Videos, die sie während der Studie streamen, selbst wählen können.
Supervisor: Seufert, M.: Identifying User Behavior from Encrypted Video Streaming Traffic, (2019).
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.
Klueber, S., Wolf, E., Grundgeiger, T., Brecknell, B., Mohamed, I., Sanderson, P.M.: Head-Worn Displays and Spearcons: Supporting Multiple Patient Monitoring.Applied Ergonomics.78,86-96 (2019).
In hospitals, clinicians often need to monitor several patients while performing other tasks. However, visual displays that show patientsu0027 vital signs are in fixed locations and auditory alarms intended to alert clinicians may be missed. Information such as spearcons (time-compressed speech earcons) that ‘travels’ with the clinician and is delivered by earpiece and/or head-worn displays (HWDs), might overcome these problems. In this study, non-clinicians monitored five simulated patients in three 10-min scenarios while performing a demanding tracking task. Monitoring accuracy was better for participants using spearcons and a HWD (88.7%) or a HWD alone (86.2%) than for participants using spearcons alone (74.1%). Participants using the spearcons and HWD (37.7%) performed the tracking task no differently from participants using spearcons alone (37.1%) but participants using the HWD alone performed worse overall (33.1%). The combination of both displays may be a suitable solution for monitoring multiple patients.
Hamzeheinejad, N.: VR Simulation as a Motivator in Gait Rehabilitation.Proceedings of the 26th IEEE Virtual Reality (VR) conference. IEEE (2019).
Gait rehabilitation is a necessary process for patients suffering from post-stroke motor impairments. The patients are required to perform repetitive practices using a robot-assisted gait device. Repeated exercises can become extremely frustrating and the patients lose their motivation over time. In my PhD research, I focus on Virtual Reality (VR) as a medium to improve gait rehabilitation in terms of enjoyment, motivation, efficiency, and effectiveness. The objective is to systematically investigate different factors, such as the presence of a trainer, interactivity, gamification, and storytelling in a two-step process. First, by evaluating the applicability of different factors for the clinical use with healthy subjects. Second, by evaluating the effectiveness of the VR simulation with patients with gait deficits, especially stroke patients in collaboration with a [country] clinic.
Kern, F., Winter, C., Gall, D., Käthner, I., Pauli, P., Latoschik, M.E.: Immersive Virtual Reality and Gamification Within Procedurally Generated Environments to Increase Motivation During Gait Rehabilitation.2019 IEEE Conference on Virtual Reality and 3D User Interfaces (VR) (2019).
Virtual Reality (VR) technology offers promising opportunities to improve traditional treadmill-based rehabilitation programs. We present an immersive VR rehabilitation system that includes a head-mounted display and motion sensors. The application is designed to promote the experience of relatedness, autonomy, and competence. The application uses procedural content generation to generate diverse landscapes. We evaluated the effect of the immersive rehabilitation system on motivation and affect. We conducted a repeated measures study with 36 healthy participants to compare the immersive program to a traditional rehabilitation program. Participants reported significant greater enjoyment, felt more competent and experienced higher decision freedom and meaningfulness in the immersive VR gait training compared to the traditional training. They experienced significantly lower physical demand, simulator sickness, and state anxiety, and felt less pressured while still perceiving a higher personal performance. We derive three design implications for future applications in gait rehabilitation: Immersive VR provides a promising augmentation for gait rehabilitation. Gamification features provide a design guideline for content creation in gait rehabilitation. Relatedness and autonomy provide critical content features in gait rehabilitation.
Hertweck, S., Weber, D., Alwanni, H., Unruh, F., Fischbach, M., Latoschik, M.E., Ball, T.: Brain Activity in Virtual Reality: Assessing Signal Quality of High-Resolution EEG While Using Head-Mounted Displays.Proceedings of the 26th IEEE Virtual Reality (VR) conference. IEEE (2019).
Seufert, M., Schatz, R., Wehner, N., Casas, P.: QUICker or not? - an Empirical Analysis of QUIC vs TCP for Video Streaming QoE Provisioning.3rd International Workshop on Quality of Experience Management (QoE-Management). , Paris, France (2019).
The introduction of the QUIC (Quick UDP Internet Connections) transport protocol by Google aimed to improve the Quality of Experience (QoE) with web services compared to the prevailing Transport Control Protocol (TCP). Nowadays, QUIC has become the default protocol to communicate between the Google Chrome browser and Google servers and accounts for an increasing share of the Internet traffic. This work investigates whether the promised QoE benefits of QUIC are indeed noticeable for end users or not. A measurement study was conducted for YouTube video streaming in two mobile and two fixed access networks, in which a defined set of videos was streamed back-to-back with QUIC and TCP in randomized order. QoE factors of video streaming (such as initial delay, the visual quality of the video, and stalling) were compared statistically to find significant differences between the streaming over QUIC and the streaming over TCP. Surprisingly, no evidence for any QoE improvement of QUIC over TCP in the context of YouTube streaming could be found.
Skwarek, V., Reher, J., Geissler, S., Zinner, T.: Automation und Digitalisierung - Potenzial und Einsatz von Blockchain- und Distributed-Ledger-Technologien in der Automatisierungstechnik, (2019).
Schaper, P., Grundgeiger, T.: Author accepted manuscript: Commission Errors with Forced Response Lag.Quarterly Journal of Experimental Psychology. (2019).
Supervisor: Moldovan, C.: Analyze des Verhaltens und der Zuschauerbindung von Twitch Nutzern, (2019).
Metter, C.: Resilience, Availability, and Serviceability Evaluation in Software-defined Networks, (2019).
Oberdörfer, S., Latoschik, M.E.: Knowledge Encoding in Game Mechanics: Transfer-Oriented Knowledge Learning in Desktop-3D and VR.International Journal of Computer Games Technology.2019, (2019).
Supervisor: Moldovan, C.: Implementation of an Adaptation Algorithm for 360-Degree Videos, (2019).
Supervisor: Moldovan, C.: Applied Optimization of Virtual Reality Videos, (2019).
Loh, F.: Studying the Video Segmentation of different Streaming Platforms, (2019).
In der Arbeit soll sich angeschaut werden, wie auf verschiedenen Streamingplatformen (YouTube, Dailymotion, Vimeo, ..) Videos in Segmente und Frames aufgeteilt sind.
Loh, F.: Machine Learning Approach to Classify Video Stalls at Network Layer, (2019).
Loh, F.: Characterization of the Streaming Behavior of the Amazon Echo Show, (2019).
In der Arbeit soll das Streamingverhalten des Geräts bei verschiedenen (sich dynamisch ändernden) Bandbreiteneinstellungen untersucht werden.
Lugrin, J.-L., Latoschik, M.E., Glémarec, Y., Bosser, A.-G., Chollet, M.: Towards Narrative-Driven Atmosphere for Virtual Classroom.Proceedings of the 38th ACM CHI conference (Late Breaking Work Track) (2019).
Lugrin, J.-L., Landeck, M., Latoschik, M.E.: Simulated Reference Frame Effects on Steering, Jumping and Sliding.Proceedings of the 26th IEEE Virtual Reality (VR) conference (2019).
Oberdörfer, S., Heidrich, D., Latoschik, M.E.: Usability of Gamified Knowledge Learning in VR and Desktop-3D.Proceedings of CHI 2019. S. 175 ff. (2019).
Hamzeheinejad, N., Roth, D., Götz, D., Weilbach, F., Latoschik, M.E.: Physiological Effectivity and User Experience of Immersive Gait Rehabilitation.The First IEEE VR Workshop on Applied VR for Enhanced Healthcare (AVEH). IEEE (2019).
Gait impairments from neurological injuries require repeated and exhaustive physical exercises for rehabilitation. Prolonged physical training in clinical environments can easily become frustrating and de-motivating for various reasons which in turn risks to decrease efficiency during the healing process. This paper introduces an immersive VR system for gait rehabilitation which targets user experience and increase of motivation while evoking comparable physiological responses needed for successful training effects. The system provides a virtual environment consisting of open fields, forest, mountains, waterfalls, animals, and a beach for inspiring strolls and is able to include a virtual trainer as a companion during the walks. We evaluated the ecological validity of the system with healthy subjects before performing the clinical trial. We assessed the systemu0027s target qualities with a longitudinal study with 45 healthy participants in three consecutive days in comparison to a baseline non-VR condition. The system was able to evoke similar physiological responses. The workload was increased for the VR condition but the system also elicited a higher enjoyment and motivation which was the main goal. The latter benefits slightly decreased over time (as did workload) while they were still higher than in the non-VR condition. The virtual trainer did not show to be beneficial, the corresponding implications are discussed. Overall, the approach shows promising results which renders the system a viable alternative for the given use case while it motivates interesting direction for future work.
Ott, S.: Design and Performance Evaluation of NMS-aware SDN Controle Plane Mechanisms, (2019).
Linguaglossa, L., Lange, S., Pontarelli, S., Retvari, G., Rossi, D., Zinner, T., Bificulo, R., Jarschel, M., Bianchi, G.: Survey of Performance Acceleration Techniques for Network Function Virtualization.Proceedings of the IEEE. (2019).
The ongoing network softwarization trend holds the promise to revolutionize network infrastructures by making them more flexible, reconfigurable, portable, and more adaptive than ever. Still, the migration from hard-coded/hardwired network functions towards their software-programmable counterparts comes along with the need for tailored optimizations and acceleration techniques, so as to avoid, or at least mitigate, the throughput/latency performance degradation with respect to fixed function network elements. The contribution of this article is twofold. First, we provide a comprehensive overview of the host-based Network Function Virtualization (NFV) ecosystem, covering a broad range of techniques, from low level hardware acceleration and bump-in-the-wire offloading approaches, to high-level software acceleration solutions, including the virtualization technique itself. Second, we derive guidelines regarding the design, development, and operation of NFV-based deployments that meet the flexibility and scalability requirements of modern communication networks.
Enghardt, T., Zinner, T., Feldmann, A.: Web Performance Pitfalls.Passive and Active Measurement Conference (PAM) (2019).
Alissa, A., Bentalab, A., Zinner, T., Ghita, B., Mkwawa, I.-H.: BBGDASH: A Max-Min Bounded Bitrate Guidance for SDN Enabled Adaptive Video Streaming.22nd Conference on Innovation in Clouds, Internet and Networks and Workshops (ICIN (2019).
Schwarzmann, S., Breitbach, P., Zinner, T.: Computing QoE-relevant Adaptive Video Streaming Metrics using Discrete-Time Analysis.Third International Workshop on Quality of Experience Management 2019 (2019).
Lange, S., Linguaglossa, L., Geissler, S., Rossi, D., Zinner, T.: Discrete-Time Modeling of NFV Accelerators that Exploit Batched Processing.IEEE Conference on Computer Communications (Infocom) (2019).
Geissler, S., Lange, S., Wamser, F., Zinner, T., Hoßfeld, T.: KOMon - Kernel-based Online Monitoring of VNF Packet Processing Times.2019 International Conference on Networked Systems (NetSys), Best Paper Award (2019).
Sanderson, P.M., Brecknell, B., Leong, S.Y., Klueber, S., Wolf, E., Hickling, A., Tang, T.-L., Bell, E., Li, S.Y.W., Loeb, R.G.: Monitoring vital signs with time-compressed speech.Journal of Experimental Psychology: Applied. (2019).
Spearcons—time-compressed speech phrases—may be an effective way of communicating vital signs to clinicians without disturbing patients and their families. Four experiments tested the effectiveness of spearcons for conveying oxygen saturation (SpO2) and heart rate (HR) of one or more patients. Experiment 1 demonstrated that spearcons were more effective than earcons (abstract auditory motifs) at conveying clinical ranges. Experiment 2 demonstrated that casual listeners could not learn to decipher the spearcons whereas listeners told the exact vocabulary could. Experiment 3 demonstrated that participants could interpret sequences of sounds representing multiple patients better with spearcons than with pitch-based earcons, especially when tones replaced the spearcons for normal patients. Experiment 4 compared multiple-patient monitoring of two vital signs with either spearcons, a visual display showing SpO2 and HR in the same temporal sequence as the spearcons, or a visual display showing multiple patient levels simultaneously. All displays conveyed which patients were abnormal with high accuracy. Visual displays better conveyed the vital sign levels for each patient, but cannot be used eyes-free. All displays showed accuracy decrements with working memory load. Spearcons may be viable for single and multiple patient monitoring. Further research should test spearcons with more vital signs, during multitasking, and longitudinally.
Schwind, A., Midoglu, C., Alay, Ö., Griwodz, C., Wamser, F.: Dissecting the performance of YouTube video streaming in mobile networks.International Journal of Network Management. (2019).
Video streaming applications constitute a significant portion of the Internet traffic today, with mobile accounting for more than half of the online video views. The high share of video in the current Internet traffic mix has prompted many studies that examine video streaming through measurements. However, streaming performance depends on many different factors at different layers of the TCP/IP stack. For example, browser selection at the application layer or the choice of protocol in transport layer can have significant impact on the video performance. Furthermore, video performance heavily depends on the underlying network conditions (eg, network and link layers). For mobile networks, the conditions vary significantly, since each operator has a different deployment strategy and configuration. In this paper, we focus on YouTube and carry out a comprehensive study investigating the influence of different factors on streaming performance. Leveraging the Measuring Mobile Broadband Networks in Europe (MONROE) test bed that enables experimentation with 13 different network configurations in four countries, we collect more than 1800 measurement samples in operational mobile networks. With this campaign, our goal is to quantify the impact of parameters from different layers on YouTube's streaming quality of experience (QoE). More specifically, we analyze the role of the browser (eg, Firefox and Chrome), the impact of transport protocol (eg, TCP or QUIC), the influence of network bandwidth, and signal coverage on streaming QoE. Our analysis reveals that all these parameters need to be taken into account jointly for network management practices, in order to ensure a high end‐user experience.
Heidrich, D., Oberdörfer, S., Latoschik, M.E.: The Effects of Immersion on Harm-Inducing Factors in Virtual Slot Machines.Proceedings of the 26th IEEE Virtual Reality (VR) conference. IEEE (2019).
Latoschik, M.E., Kern, F., Stauffert, J.-P., Bartl, A., Botsch, M., Lugrin, J.-L.: Not Alone Here?! Scalability and User Experience of Embodied Ambient Crowds in Distributed Social Virtual Reality.IEEE Transactions on Visualization and Computer Graphics (TVCG).25,2134-2144 (2019).
This article investigates performance and user experience in Social Virtual Reality (SVR) targeting distributed, embodied, and immersive, face-to-face encounters. We demonstrate the close relationship between scalability, reproduction accuracy, and the resulting performance characteristics, as well as the impact of these characteristics on users co-located with larger groups of embodied virtual others. System scalability provides a variable number of co-located avatars and AI-controlled agents with a variety of different appearances, including realistic-looking virtual humans generated from photogrammetry scans. The article reports on how to meet the requirements of embodied SVR with todayu0027s technical off-the-shelf solutions and what to expect regarding features, performance, and potential limitations. Special care has been taken to achieve low latencies and sufficient frame rates necessary for reliable communication of embodied social signals. We propose a hybrid evaluation approach which coherently relates results from technical benchmarks to subjective ratings and which confirms required performance characteristics for the target scenario of larger distributed groups. A user-study reveals positive effects of an increasing number of co-located social companions on the quality of experience of virtual worlds, i.e., on presence, possibility of interaction, and co-presence. It also shows that variety in avatar/agent appearance might increase eeriness but might also stimulate an increased interest of participants about the environment.
Korger, A., Baumeister, J.: Textual Case-based Adaptation using Semantic Relatedness - A Case Study in the Domain of Security Documents.WM2019 - 10te Konferenz Professionelles Wissensmanagement (2019).
Baumeister, J.: Experience-based Quality Assessment of Distributed Knowledge Graphs.WM 2019 - 10te Konferenz Professionelles Wissensmanagement (2019).
Schwind, A., Janiak, L., Moldovan, C., Wamser, F., Hoßfeld, T.: Peeking under the Hood – How the Measurement Setup Influences the Video Streaming Behavior.The 3rd International Workshop on Quality of Experience Management (QoE-Management 2019). , Paris, France (2019).
Global Internet video traffic will dramatically increase in the next years. With this rapid growth, interest in the application behavior of video streaming services and the resulting user experience rises. In particular, there is a need to understand the influence of system parameters on the streaming performance. Thus, several monitoring approaches have been developed which allow conducting automated measurements on a large-scale, for example, lightweight approaches for measurements running in the mobile networks or setups using a virtual frame buffer for servers without a display running in virtualized cloud environments. In some cases, the measurement hardware can totally be controlled, in other cases, there is no knowledge about parallel running services. In this paper, we answer the question whether and how much the measurement setup (e.g., virtualization, headless browsers, load on machines) influences the video streaming behavior. Therefore, we compare eight management setups with the ground truth (an end user watching a video on the own device) by evaluating the key performance indicators on application layer during video streaming, i.e. initial video playout delays and stalling. Our results reveal important insights: some of the common measurement setups heavily influence the measurements and must be avoided to collect reliable results.
Supervisor: Seufert, M.: Evaluation of the Impact of Cross-Traffic on TCP and QUIC Video Streaming, (2019).
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.
Hettinger, L., Dallmann, A., Zehe, A., Niebler, T., Hotho, A.: ClaiRE at SemEval-2018 Task 7: Classification of Relations using Embeddings.Proceedings of International Workshop on Semantic Evaluation (SemEval-2018). , New Orleans, LA, USA (2018).
Dinh-Xuan, L., Popp, C., Burger, V., Wamser, F., Hoßfeld, T.: Impact of VNF Placements on QoE Monitoring in the Cloud.International Journal of Network Management. (2018).
Supervisor: Grigorjew, A.: Consolidation of Resources and Demands in VNF Chain Placement Problems (BA), (2018).
Contact: Alexej Grigorjew <alexej.grigorjew@informatik.uni-wuerzburg.de> Placing Virtual Network Functions in network graphs is an NP-hard problem. Solving large problem instances is often unfeasible due to limited computational resources and time. For many use cases, the problem input is not required in all detail, but can be aggregated into a smaller abstraction. In this work, an algorithm should be implemented that generates such smaller representations of graphs and VNF demands. Further, its performance shall be evaluated by applying (existing) solvers on the results and comparing both runtime and quality of their placements with the original graph.
Schöch, C., Schlör, D., Zehe, A., Gebhard, H., Becker, M., Hotho, A.: Burrows’ Zeta: Exploring and Evaluating Variants and Parameters.DH. S. 274-277 (2018).
Knapp, T.: Performance Evaluation of DASH Streaming with Real Time Encoding and Continuous Quality Levels, (2018).
Das Thema dieser Arbeit war die Bewertung von DASH Streaming unter Verwendung von Echtzeitkodierung. Zu diesem Zweck wurden vier verschiedene Codecs untersucht. Die spezifischen Parameter der Codecs wurden durch den Effekt klassifiziert, den sie auf die Metriken in Bezug auf die Leistung, die Komprimierung und die Qualität haben. Der Einfluss der signifikanten Parameter auf jede der drei Metriken wurde erforscht. Als Ergebnis wurde die Messung durch eine multi-dimensionale Funktion interpoliert. Nach der Codec Bewertung wurde ein aktuelles Video-Streaming Modell für Echtzeitkodierung erweitert. Folglich wurde ein Auswahlalgorithmus spezifiziert, der durch den Client verwendet wird, um die Kodierungsparameter zu wählen. Durch Anwendung der zuvor bestimmten Codec Funktionen auf das erweiterte Modell können mehrere Szenarien, wie zum Beispiel der Einuss variierender Bandbreite oder die Zeitanforderungsverteilungen mit Fokus auf die Qualitätseigenschaften gegeben durch das Modell, analysiert werden. Die Resultate zeigen die Anpassungsfähigkeit des neuen Modells hin zu veränderter Netzwerkumgebung und bewirken effektiv eine Vermeidung von Videounterbrechungen. Bisher scheint sich die Wahrscheinlichkeitsdichtefunktion des Pufferlevels in Abhängigkeit der Modellparameter in einzelnen Situationen zyklisch zu verändern. Das Modell kann mit jeder der vier untersuchten Codecs kombiniert werden. Den- noch zeigte der Codec H.264 eine geringfügig bessere Ausführung als die Anderen. Unter Verwendung von H.264 als Codec, hat sich das erweiterte Modell gegenüber des Referenzmodells durchgesetzt, da es gute Qualitätswerte unter Komprimierungs- und Performanz-Einschränkungen einhalten konnte. Dies war für das Referenzmodell unmöglich. Diese Arbeit soll Leser dazu ermutigen in Zukunft weitere Untersuchungen in Bezug auf Echtzeitkodierung durchzuführen. Auf technischer Seite können mehr Tests ausgeführt werden, um die Verwendbarkeit des Modells zu überprüfen. Alternativ kann das Modell weiter verbessert und neue Algorithmen erprobt werden.
Steurer, F.: Design and Simulative Evaluation of Data-Driven Scheduling Algorithms for Crowdsourcing Tasks, (2018).
Borst, V.: Experimental Evaluation of the Interface Design of Crowdsourcing Tasks, (2018).
Seufert, M., Schwind, A., Waigand, M., Hoßfeld, T.: Potential Traffic Savings by Leveraging Proximity of Communication Groups in Mobile Messaging.14th International Conference on Network and Service Management (CNSM). , Rome, Italy (2018).
Communication groups in mobile messaging applications (MMAs) multiply the data transmissions, because every message has to be delivered to all members of the communication group. Thereby, they put a high load on mobile networks. As the number of recipients is still comparably small, the dataintensive user-generated content cannot be handled efficiently in large content delivery networks. However, small communication groups, such as groups of friends or teams, might often be in close proximity, which can be leveraged to locally deliver messages by applying edge caching or device-to-device (D2D) communication. In this work, a simulation study is conducted to investigate these potential traffic savings in the mobile network. It is based on a realistic communication model of the MMA WhatsApp and utilizes different models for human mobility. The user mobility and MMA communication are simulated for a single day in a small city to obtain the ratio of messages, which could be potentially transmitted locally when utilizing edge caching and D2D communication.
Metter, C., Burger, V., Hu, Z., Pei, K., Wamser, F.: Evaluation of the Detection Capabilities of the ONOS SDN Controller.7th IEEE International Conference on Communications and Electronics (IEEE ICCE 2018). S. 96 - 101. , Hue, Vietnam (2018).
The process of monitoring the network, especially for larger ones, is very complex and contains many pitfalls. For instance the balance between granularity of information and their performance impact on the network. With the help of SDN this challenge can become easier, as it offers new methods, mechanisms and opportunities. One of the current most important Open Source controllers is the ONOS SDN controller. According to its developers it is a production ready controller that offers high availability due to its logically centralized and physically distributed architecture. But, as our investigations show, it is unable to cope with hazardous network conditions such as sporadic or recurring packet loss. It either does not detect packet loss or only detects it after long time periods, failing all common network availability targets.
Schütz, A., Fertig, T., Weber, K., Vu, H., Hirth, M., Tran-Gia, T.: Vertrauen ist gut, Blockchain ist besser - Einsatzmöglichkeiten von Blockchain für Vertrauensprobleme im Crowdsourcing.HMD Praxis der Wirtschaftsinformatik. (2018).
Beim Crowdsourcing schreiben Unternehmen auf speziellen Marktplätzen Arbeiten aus, wo sie von einer großen Anzahl von anonymen Arbeitern bearbeitet werden können. Im Gegensatz zu traditionellen Arbeitsverhältnissen geht beim Crowdsourcing der Arbeitnehmer in Vorleistung. Der Auftraggeber entscheidet anhand der übermittelten Bearbeitung, ob der Arbeitnehmer entlohnt wird oder nicht. Vertrauen zwischen beiden Parteien ist daher ein entscheidender Erfolgsfaktor für Crowdsourcing. Dieser Beitrag beschreibt die Vertrauensprobleme im Crowdsourcing und stellt ein Konzept für ein neuartiges Reputationssystem für Crowdsourcing-Plattformen vor. Das Konzept soll helfen, das Vertrauen im Crowdsourcing zu erhöhen. Umgesetzt wird dieses Konzept mittels Smart Contracts auf der Ethereum Blockchain im Projekt CrowdPrecision. Die Profile von Auftraggeber und Arbeitnehmer werden mit einem Reputationsscore verknüpft, der transparent und fälschungssicher in der Blockchain gespeichert wird. Die einzelnen Aufträge werden über Smart Contracts abgebildet, die eine automatisierte Entlohnung und Bewertung unter Einhaltung der vereinbarten Bedingungen garantieren.
Gensler, T.: Concept an Implementation of QoE Measurements for Audio Streaming in Spotify, (2018).
Wehner, N., Wassermann, S., Casas, P., Seufert, M., Wamser, F.: Beauty is in the Eye of the Smartphone Holder - A Data Driven Analysis of YouTube Mobile QoE.14th International Conference on Network and Service Management (CNSM). , Rome, Italy (2018).
Measuring the Quality of Experience (QoE) undergone by cellular network users has become paramount for cellular ISPs. Given its overwhelming dominance and ever-growing popularity, this paper focuses on the analysis of QoE for YouTube in mobile networks. Using a large-scale dataset of crowdsourced YouTube QoE measurements collected in smartphones with YoMoApp, we analyze the evolution of multiple relevant QoE-related metrics over time for YouTube mobile users. The dataset includes measurements from more than 360 users worldwide, spanning over the last five years. Our data-driven analysis shows a systematic performance and QoE improvement of YouTube in mobile devices over time, accompanied by an improvement of cellular network performance and by an optimization of the YouTube streaming behavior for smartphones.
Seufert, M., Wehner, N., Casas, P., Wamser, F.: A Fair Share for All: Novel Adaptation Logic for QoE Fairness of HTTP Adaptive Video Streaming.14th International Conference on Network and Service Management (CNSM), Best Paper Award. , Rome, Italy (2018).
This paper presents a novel adaptation logic for HTTP adaptive streaming (HAS), which achieves not only a high Quality of Experience (QoE) but also high QoE fairness among independent and heterogeneous clients. The algorithm forces video clients to adapt the requested quality level based on the current network conditions and their individual bit rate requirements, such that the overall quality levels selected by all currently active streaming clients are fairly distributed, i.e., they do not diverge too much. The design of the algorithm is inspired by the well-known Transmission Control Protocol (TCP) congestion control, and drives heterogeneous clients to independently converge on similar quality levels without the need for communicating with each other and/or with a centralized controller in the network. By defining quality levels with equal visual quality, and preparing video representations accordingly, the quality level fairness is extended to QoE fairness. In this work, the design of the algorithm is described and a simulative performance evaluation is conducted to compare the QoE and QoE fairness of the proposed algorithm with other HAS adaptation logics.
Lugrin, B., Eckstein, B., Bergmann, K., Heindl, C.: Adapted Foreigner-directed Communication towards Virtual Agents.International Conference on Intelligent Virtual Agents. S. 59-64. ACM (2018).
People tend to adapt to their conversation partners. In mixed-cultural settings, with a native and a non-native speaker, adaptation can manifest itself in the usage of simplified language or increased usage of non-verbal scaffolding to foster understanding. In this contribution, we address the question whether the phenomenon of AFC (adapted, foreigner-directed communication) is also shown towards a virtual agent. We therefore implemented a demonstrator with a local and a foreign agent that interact with human users in a direction giving scenario. A user study revealed that participants behaved differently towards the two agents and adapted both, their verbal and their non-verbal behaviour. We are thus confident, that our demonstrator is well suited to systematically study AFC.
Dinh-Xuan, L.: Quality of Experience Assessment of Cloud Applications and Performance Evaluation of VNF-Based QoE Monitoring, (2018).
Eckstein, B., Krapp, E., Lugrin, B.: Towards Serious Games and Applications in Smart Substitutional Reality.2018 10th International Conference on Virtual Worlds and Games for Serious Applications (VS-Games). S. 25-32 (2018).
Substitutional Reality (SR), the integration of the physical environment into Virtual Reality (VR), is a novel approach to facilitate and intensify the use of home-based VR systems. We propose to extend the passive haptics of SR with the interactive functionality of a smart home environment. This concept of smart SR is meant as a foundation for serious games and applications. In this paper, we describe the concept behind smart SR as well as the prototype in our lab environment. We created multiple virtual environments with a varying degree of mismatch regarding the real world. We present a user study where we examined the influence of these environments on the perceived sense of presence and motivation of users. Our findings showed that presence was high in all conditions while motivation increased with the level of mismatch. This provides us with a promising basis for further research.
Moldovan, C., Skorin-Kapov, L., Heegaard, P.E., Hoßfeld, T.: Optimal Fairness and Quality in Video Streaming With Multiple Users.30th International Teletraffic Congress (ITC 30). S. 6. , Vienna, Austria (2018).
With the majority of video distribution services relying on the HTTP adaptive streaming paradigm, a great deal of research is geared towards developing algorithms and solutions for improving user perceived quality while making efficient use of available resources. Our goal is to provide the means for benchmarking such solutions in the context of multiple users accessing Video on Demand content while sharing a bottleneck link. For that purpose, we propose a quadratic problem formulation to compute the theoretical optimum in terms of adaptation strategies and corresponding segment downloads across multiple users under given bandwidth constraints. By aiming to maximize both service quality and fairness, we quantify and compare the impact of different fairness objectives (bandwidth fairness, pattern fairness, and session fairness) on resulting quality and achieved QoE fairness. Based on conducted simulations and parameter studies, our results demonstrate the benefits of optimizing for session fairness as compared to other approaches.
Weber, K.: Machine Learning for Classification of Streaming Data, (2018).
Laut Vorhersagen [1] soll mobiles Video Streaming im Jahr 2021 etwa dreiviertel des gesamten Internetverkehrs ausmachen. Schon in der heutigen Zeit nimmt es bereits einen großen Teil ein. Dies führt dazu, dass Netzwerkprovider herausfinden müssen, wie sie mit der Masse an Verkehr umgehen sollen, um gleichzeitig ihre Kunden zufrieden stellen zu können. Eine Metrik, um die Nutzerzufriedenheit festzustellen, ist Quality of Experience (QoE). Mit Hilfe von QoE-Management können Provider anhand des Datenverkehrs die Zufriedenheit der Kunden beeinflussen und trotzdem die Kosteneffizienz zu wahren. Ein wichtiger Teil vom QoE-Management ist das QoE-Monitoring. Da allerdings der Netzwerkverkehr verschlüsselt ist und deshalb deep packet inspection nicht mehr verwendet werden kann, muss auf statistische Analysen zurück gegriffen werden. Das Ziel der Arbeit ist es, wichtige QoE-Einflussfaktoren für Mobile Video Stream- ing, speziell am Beispiel YouTube, zu finden mit Hilfe von Machine Learning (ML). Um die Daten zu sammeln, wurde ein Versuchsaufbau bestehend aus einer Linux- Maschine und einem Smartphone benutzt, wobei der PC als Router für das Smartphone zum Internet diente. Auf dem Smartphone lief die originale YouTube-App, welche auch im Google Play Store erhältlich ist, sowie eine Wrapper-App für das Monitoring. Diese kann autonom die YouTube-App starten und Videos abspielen. Während ein Video läuft werden Netzwerk- und Anwendungsinformationen gesam- melt und auf dem Gerät in einer separaten Datei gespeichert. Mit diesen Daten konnten drei verschiedene Datensätze gemessen werden, wobei zwei zur QoE-Vorhersage für initial delay und der dritte Datensatz zur QoE-Vorhersage for stalling events verwendet wurden. Der erste Datensatz bestand aus drei ver- schiedenen Videos und 1070 Instanzen, der zweite Datensatz aus 18 Videos und 1400 Instanzen und der letzte Datensatz aus 930 Instanzen sowie drei Videos. Des Weiteren wurden die Videos mit verschiedenen Bandbreitenbegrenzungen abgespielt, welche von 0.5 Mbits/s bis 5 Mbits/s reichten. Um die Datensätze mit ML klas- sifizieren zu können, mussten die Instanzen zuvor in vordefinierte Klassen anhand ihres initial delay oder ihrer Anzahl an stallings aufgeteilt werden. Versuche mit dem ersten Datensatz zeigten, dass QoE-Schätzungen mit drei Videos nicht aussagekräftig genug sind. Anhand der Ergebnisse mit dem zweiten Datensatz konnten aber folgende wichtige Einflussparameter festgestellt werden: der gesamte Durchsatz von Up- und Downlink, sowie der Durchsatz in den ersten 20 Sekunden. Einflussreiche Parameter sind außerdem der Durchsatz der ersten fünf Segmente, welche nicht leer sind, und deren Größe. Im Anschluss daran wurden weitere QoE-Vorhersagen mit verschiedenen Klassen- aufteilungen gemacht. Es stellte sich heraus, dass die Genauigkeit der Vorhersagen mit steigender Klassenzahl stark nachlässt. Des Weiteren wurden Schätzungen mit Klassenaufteilungen aus anderen QoE-Studien auf unsere Datensätze angewendet, welche allerdings keine weiteren Erkenntnisse lieferten. Zum Schluss wurden QoE-Schätzungen mit dem dritten Datensatz für stalling gemacht und die daraus folgenden Ergebnisse mit den Resultaten der QoE-Vorhersagen mit dem zweiten Datensatz verglichen. Die Faktoren, welche zuvor bei den QoE- Schätzungen für initial delay als wichtige QoE-Einflussfaktoren galten, erwiesen sich bei den QoE-Schätzungen für stalling als nicht einflussreich. Weitere QoE- Vorhersagen zeigten, dass die Anzahl an Qualitätsänderungen während des Videos, sowie die mittlere Ankuftszeit und die kumulative Verteilung der Ankunftszeit der Uplink Requests, großen Einfluss auf die QoE haben.
Baumeister, J., Reuss, P. hrsg: Proceedings of the Workshop: 'Knowledge and Experience Management' (German SIG meeting, FGWM). (2018).
Volodina, E., Aziz, A., Rathgeb, E., Hoßfeld, T.: Application of Visual Analysis to Detect and Analyze Patterns in VoIP Attack Traffic.17th IEEE International Conference On Trust, Security And Privacy In Computing And Communications/12th IEEE International Conference On Big Data Science And Engineering (TrustCom/BigDataSE) (2018).
Hamzeheinejad, N., Straka, S., Gall, D., Weilbach, F., Latoschik, M.E.: Immersive Robot-Assisted Virtual Reality Therapy for Neurologically-Caused Gait Impairments.Proceedings of the 25th IEEE Virtual Reality (VR) conference. (2018).
This paper presents an immersive Virtual Reality (VR) therapy system for gait rehabilitation after neurological impairments, e.g., caused by accidents or strokes: The system targets increase of patientsu0027 motivation to perform the repeated exercise by providing stimulating virtual exercise environments with the final goal to increase therapy efficiency and effectiveness. Instead of simply working out on immobile stationary devices, the system allows them to walk through and explore a stimulating virtual world. Patients are immersed in the virtual environments using a Head-Mounted Display (HMD). Walking patterns are captured by motion sensors attached to the patientsu0027 feet to synchronize locomotion speed between the real and the virtual world. A user-centered design process evaluated usability, user experience, and feasibility to confirm the overall goals of the system before any sensitive clinical trials with impaired patients can start. Overall, the results demonstrated an encouraging user experience and acceptance while it did not induce any unwanted side-effects, e.g., nausea or cyber-sickness.
Scherer, K.P., Rieder, C., Germann, M., Baumeister, J., Plehn, S.: Knowledge-Based Decision Support with Self-Learning Methods.The Twelfth International Conference on Advanced Engineering Computing and Applications in Sciences (ADVCOMP) (2018).
Seipel, D., Nogatz, F., Abreu, S.: Domain-specific languages in Prolog for declarative expert knowledge in rules and ontologies.Computer Languages, Systems & Structures.51C,102-117 (2018).
Declarative if–then rules have proven very useful in many applications of expert systems. They can be managed in deductive databases and evaluated using the well-known forward-chaining approach. For domain-experts, however, the syntax of rules becomes complicated quickly, and already many different knowledge representation formalisms exist. Expert knowledge is often acquired in story form using interviews. In this paper, we discuss its representation by defining domain-specific languages (DSLs) for declarative expert rules. They can be embedded in Prolog systems in internal DSLs using term expansion and as external DSLs using definite clause grammars and quasi-quotations – for more sophisticated syntaxes. Based on the declarative rules and the integration with the Prolog-based deductive database system DDBase, multiple rules acquired in practical case studies can be combined, compared, graphically analysed by domain-experts, and evaluated, resulting in an extensible system for expert knowledge. As a result, the actual modeling DSL becomes executable; the declarative forward-chaining evaluation of deductive databases can be understood by the domain experts. Our DSL for rules can be further improved by integrating ontologies and rule annotations.
Hoßfeld, T., Varela, M., Heegaard, P.E., Skorin-Kapov, L.: QoE Analysis of the Setup of Different Internet Services for FIFO Server Systems.Proceedings of the 19th International Conference on Measurement, Modelling and Evaluation of Computing Systems (MMB). , Erlangen, Germany (2018).
Surminski, S., Moldovan, C., Hoßfeld, T.: Practical QoE Evaluation of Adaptive Video Streaming.Proceedings of the 19th International Conference on Measurement, Modelling and Evaluation of Computing Systems (MMB). , Erlangen, Germany (2018).
Hoßfeld, T., Metzger, F., Heegaard, P.E.: Traffic Modeling for Aggregated Periodic IoT Data.Proceedings of the 21st Conference on Innovation in Clouds, Internet and Networks (ICIN). , Paris, France (2018).
Skorin-Kapov, L., Varela, M., Hoßfeld, T., Chen, K.-T.: A Survey of Emerging Concepts and Challenges for QoE Management of Multimedia Services.ACM Transactions on Multimedia Computing, Communications and Applications. (2018).
Lagerspetz, E., Flores, H., Mäkitalo, N., Hui, P., Nurmi, P., Tarkoma, S., Passarella, A., Ott, J., Reichl, P., Conti, M., Fiedler, M., Singh, J., Strufe, T., Hoßfeld, T.: Pervasive Communities in the Internet of People.Proceedings of the 1st International Workshop on Context-Awareness for Multi-Device Pervasive and Mobile Computing (PerCrowd). , Athens, Greece (2018).
Hoßfeld, T., Skorin-Kapov, L., Heegaard, P.E., Varela, M.: A new QoE fairness index for QoE management.Quality and User Experience. (2018).
Münster, S., Friedrichs, K., Niebling, F., Seidel-Grzesińska, A. hrsg: Digital Research and Education in Architectural Heritage.Springer International Publishing (2018).
Supervisor: Borchert, K.: Analysis and Correlation of objective and subjective Performance Data of an Enterprise Application, (2018).
Contact: kathrin.borchert@informatik.uni-wuerzburg.de
Roth, D., Kleinbeck, C., Feigl, T., Mutschler, C., Latoschik, M.E.: Beyond Replication: Augmenting Social Behaviors in Multi-User Virtual Realities.Proceedings of the 25th IEEE Virtual Reality (VR) conference. S. 215-222 (2018).
This paper presents a novel approach for the augmentation of social behaviors in virtual reality (VR). We designed three visual transformations for behavioral phenomena crucial to everyday social interactions: eye contact, joint attention, and grouping. To evaluate the approach, we let users interact socially in a virtual museum using a large-scale multi-user tracking environment. Using a between-subject design (N = 125) we formed groups of five participants. Participants were represented as simplified avatars and experienced the virtual museum simultaneously, either with or without the augmentations. Our results indicate that our approach can significantly increase social presence in multi-user environments and that the augmented experience appears more thought-provoking. Furthermore, the augmentations seem also to affect the actual behavior of participants with regard to more eye contact and more focus on avatars/objects in the scene. We interpret these findings as first indicators for the potential of social augmentations to impact social perception and behavior in VR.
Byrka, J., Pensyl, T., Rybicki, B., Spoerhase, J., Srinivasan, A., Trinh, K.: An Improved Approximation Algorithm for Knapsack Median Using Sparsification.Algorithmica.80,1093--1114 (2018).
Zimmerer, C., Fischbach, M., Latoschik, M.E.: Space Tentacles - Integrating Multimodal Input into a VR Adventure Game.Proceedings of the 25th IEEE Virtual Reality (VR) conference. IEEE (2018).
Multimodal interfaces for Virtual Reality (VR), e.g., based on speech and gesture input/output (I/O), often exhibit complex system architectures. Tight couplings between the required I/O processing stages and the underlying scene representation and the simulator system’s flow-of-control tend to result in high development and maintainability costs. This paper presents a maintainable solution for realizing such interfaces by means of a cherry-picking approach. A reusable multimodal I/O processing platform is combined with the simulation and rendering capabilities of the Unity game engine, allowing to exploit the game engine’s superior API usability and tool support. The approach is illustrated based on the development of a multimodal VR adventure game called Space Tentacles.
Seufert, M., Zeidler, B., Wamser, F., Karagkioules, T., Tsilimantos, D., Loh, F., Tran-Gia, P., Valentin, S.: A Wrapper for Automatic Measurements with YouTube’s Native Android App. (2018).
YouTube is one of the most popular and demanding services in the Internet today. Thereby, a large portion of this traffic is generated by YouTube’s mobile app. While past studies have shown how to monitor browser-based streaming on desktop PCs (e.g., YoMo) or mobile devices (e.g., YoMoApp), streaming in the native app has not been monitored yet. This paper presents an automated framework for monitoring the streaming in YouTube’s native app for Android. The concept is based on a wrapper application and the Android Debug Bridge (adb), and can be also extended to automatic measurements with other apps. For YouTube, it allows to collect application-layer streaming data, such as current playtime, buffered playtime, video encoding, and quality switches. These data can be complemented with network measurements on the mobile access link to obtain a holistic view on mobile YouTube streaming on Android devices. In addition to describing the software design and testbed setup, this paper discusses an experimental measurement. This study analyzes the streaming in the native YouTube app and compares it to the streaming from the mobile YouTube website via YoMoApp.
Burger, V., Zinner, T., Dinh-Xuan, L., Wamser, F., Tran-Gia, P.: A Generic Approach to Video Buffer Modeling using Discrete-Time Analysis.ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM). (2018).
Nguyen-Ngoc, A., Lange, S., Geissler, S., Zinner, T., Tran-Gia, P.: Estimating the Flow Rule Installation Time of SDN Switches when Facing Control Plane Delay.19th International GI/ITG Conference on “Measurement, Modelling and Evaluation of Computing Systems”. , Erlangen (2018).
The software defined networking (SDN) paradigm has numerous benefits for network operators, including cost aspects, flexibility, and programmability. In the centralized SDN architecture, the controller can order the installation of flow rules in the switches it manages via FlowMod messages. Since the processing time of these messages has a direct impact on the reaction time of the network, it is a key performance indicator for switches and quantifying it in a reliable manner is required for ensuring state consistency between the control and the data plane. Furthermore, real world deployments not only consist of different data plane hardware, but may feature varying control plane delays. Hence, in this work, we investigate the impact of such a delay on the FlowMod processing time of OpenFlow switches. Firstly, we identify a significant heterogeneity between data plane hardware in terms of processing times as well as the underlying TCP-level behavior. Secondly, we show that despite this heterogeneity, combining switch specific information with delay measurements at the controller can be used to reliably infer FlowMod processing times. We confirm our results with measurements in a dedicated testbed that is comprised of three different hardware switches, three different SDN controllers, and several high precision measurement devices.
Lugrin, J.-L., Oberdorfer, S., Latoschik, M.E., Wittmann, A., Seufert, C., Grafe, S.: VR-Assisted vs Video-Assisted Teacher Training.Proceedings of the 25th IEEE Virtual Reality (VR) conference (2018).
Lugrin, J.-L., Ertl, M., Krop, P., Klüpfel, R., Stierstorfer, S., Weisz, B., Rück, M., Schmitt, J., Schmidt, N., Latoschik, M.E.: Any ”Body” There? - Avatar Visibility Effects in a Virtual Reality Game.2018 IEEE Conference on Virtual Reality and 3D User Interfaces (VR). S. 17-24. IEEE (2018).
Bloch, C., Roth, D., Vogeley, K.: Seeing It Your Way: Spatial Perspective Taking as a Mechanism for Interpersonal Understanding.Presentation on the 68th Annual Conference of the International Communication Association (ICA), May 24-28, Prague, Czech Republic. (2018).
Niebling, F., Münster, S., Bruschke, J., Maiwald, F., Friedrichs, K.: Stadtgeschichtliche Forschung anhand räumlich- und zeitlich verorteter Photographien. In: Burghardt, M. und Müller-Birn, C. (hrsg.) INF-DH-2018. Gesellschaft für Informatik e.V., Bonn (2018).
Niebling, F., Maiwald, F., Münster, S., Bruschke, J., Henze, F.: Accessing Urban History using Spatial Historical Photographs.2018 Digital Heritage. IEEE (2018).
Schatz, R., Schwarzmann, S., Zinner, T., Dobrijevic, O., Liotou, E., Pocta, P., Baraković, S., Baraković Husić, J., Skorin-Kapov, L.: QoE Management for Future Networks.Autonomous Control for a Reliable Internet of Services: Methods, Models, Approaches, Techniques, Algorithms and Tools. Springer (2018).
This chapter discusses prospects of QoE management for future networks and applications. After motivating QoE management, it first provides an introduction to the concept by discussing its origins, key terms and giving an overview of the most relevant existing theoretical frameworks. Then, recent research on promising technical approaches to QoE- driven management that operate across different layers of the networking stack is discussed. Finally, the chapter provides conclusions and an outlook on the future of QoE management with a focus on those key enablers (including cooperation, business models and key technologies) that are essential for ultimately turning QoE-aware network and application management into reality.
Seufert, M.: Quality of Experience and Access Network Traffic Management of HTTP Adaptive Video Streaming., IEEE/IFIP Network Operations and Management Symposium (NOMS), Best Dissertation Award, Taipei, Taiwan (2018).
Zimmerer, C., Fischbach, M., Latoschik, M.E.: Semantic Fusion for Natural Multimodal Interfaces using Concurrent Augmented Transition Networks.Multimodal Technologies and Interaction.2,81 (2018).
Semantic fusion is a central requirement of many multimodal interfaces. Procedural methods like finite-state transducers and augmented transition networks have proven to be beneficial to implement semantic fusion. They are compliant with rapid development cycles that are common for the development of user interfaces, in contrast to machine-learning approaches that require time-costly training and optimization. We identify seven fundamental requirements for the implementation of semantic fusion: Action derivation, continuous feedback, context-sensitivity, temporal relation support, access to the interaction context, as well as the support of chronologically unsorted and probabilistic input. A subsequent analysis reveals, however, that there is currently no solution for fulfilling the latter two requirements. As the main contribution of this article, we thus present the Concurrent Cursor concept to compensate these shortcomings. In addition, we showcase a reference implementation, the Concurrent Augmented Transition Network (cATN), that validates the concept’s feasibility in a series of proof of concept demonstrations as well as through a comparative benchmark. The cATN fulfills all identified requirements and fills the lack amongst previous solutions. It supports the rapid prototyping of multimodal interfaces by means of five concrete traits: Its declarative nature, the recursiveness of the underlying transition network, the network abstraction constructs of its description language, the utilized semantic queries, and an abstraction layer for lexical information. Our reference implementation was and is used in various student projects, theses, as well as master-level courses. It is openly available and showcases that non-experts can effectively implement multimodal interfaces, even for non-trivial applications in mixed and virtual reality.
Hildebrand, K.: Towards a Source Traffic Model for Instant Messaging using WhatsApp, (2018).
Seufert, M.: Research Activities Report for "Crowdsourcing TF"., 12th Qualinet General Meeting, Pula, Italy (2018).
Supervisor: Schwind, A.: Potential Traffic Savings by Leveraging Proximity of Communication Groups in Mobile Messaging, (2018).
Contact: anika.schwind@informatik.uni-wuerzburg.de
Geissler, S., Lange, S., Wamser, F., Hoßfeld, T.: Deriving YouTube Playout Phases from Encrypted Packet Level Traffic, (2018).
From the point of view of telecommunication providers, video streaming is one of the most demanding applications in today's Internet. Over 73% of the total global network traffic has been attributed to video streaming applications in 2016. In this work, we provide a first step towards a better understanding of the packet level behavior of video streaming traffic to enable more efficient traffic engineering in the future. We perform a measurement study with the popular video streaming platform YouTube and show that the different playout phases of a video streaming session can not only be observed by evaluating application layer metrics, but also from raw and encrypted packet level traces.
Wienrich, C., Weidner, C.K., Schatto, C., Obremski, D., Israel, J.H.: A Virtual Nose as a Rest-Frame - The Impact on Simulator Sickness and Game Experience.2018 10th International Conference on Virtual Worlds and Games for Serious Applications (VS-Games). S. 1-8 (2018).
This paper presents an experiment measuring the impact of a virtual nose on simulator sickness and game experience in a virtual reality game presented on an Oculus Rift DK 2. Furthermore, the presented study investigated in the significance of the rest-frameu0027s salience, for it to reduce simulator sickness. The results of our study indicated that the usage of a virtual nose reduces simulator sickness while it does not affect the game experience. Further results showed no significant impact of the rest-frameu0027s salience, neither on simulator sickness nor on the game experience. In sum, the outcome of the study supports the thesis that a rest-frame in form of a virtual nose can be used in virtual reality applications to reduce simulator sickness.
Schaper, P., Grundgeiger, T.: Commission Errors – Determined to do the wrong thing?5th International Conference on Prospective Memory (2018).
Lüttke, S., Schwind, A., Seufert, M., Wolf, M., Meurers, D., Balle, S.: What’s Up? Ein Frühwarnsystem für Kinder und Jugendliche mit Depression basierend auf der Analyse ihrer WhatsApp-Kommunikation. Eine Pilotstudie., (2018).
Ring, M., Schlör, D., Landes, D., Hotho, A.: Flow-based Network Traffic Generation using Generative Adversarial Networks.CoRR.abs/1810.07795, (2018).
Flow-based data sets are necessary for evaluating network-based intrusion de- tection systems (NIDS). In this work, we propose a novel methodology for gener- ating 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 at- tributes. 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 gener- ated 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.
Wehner, N., Seufert, M., Wamser, F., Casas, P.: YouTube QoE Monitoring with YoMoApp: a Mobile App for Crowdsourced YouTube QoE Analysis, (2018).
Seufert, M., Wehner, N., Casas, P.: App for Dynamic Crowdsourced QoE Studies of HTTP Adaptive Streaming on Mobile Devices, (2018).
Zach, O., Slanina, M., Seufert, M.: Investigating the Impact of Advertisement Banners and Clips on Video QoE.3rd Workshop on QoE-based Analysis and Management of Data Communication Networks (Internet-QoE). , Vienna, Austria (2018).
Although Quality of Experience (QoE) of Internet services can be affected by context influence factors, their actual impact is not widely investigated yet. In the context of online video services, web portals often display advertisement banners or clips to monetize their service. However, these advertisements can distract or annoy the users, which might degrade the QoE of the actual video service. In this work, two crowdsourcing studies were conducted to investigate the impact of advertisement banners and clips on video QoE. Therefore, both theoretical opinions on in-service advertisements and subjective quality ratings are evaluated. The findings confirm that advertisements are negatively perceived by users during service consumption, but a generally negative impact on video QoE cannot be supported, as the interplay of advertisement and the QoE of video services is rather complex.
Seufert, M., Wehner, N., Casas, P.: Studying the Impact of HAS QoE Factors on the Standardized QoE Model P.1203.3rd Workshop on QoE-based Analysis and Management of Data Communication Networks (Internet-QoE). , Vienna, Austria (2018).
P.1203 is a recent standardized model for assessing the Quality of Experience (QoE) of HTTP Adaptive Video Streaming (HAS). However, its complex definition does not allow for a straightforward identification of the underlying assumptions. To overcome this issue, this work investigates the impact of the well-known QoE factors of HAS, namely, initial delay, stalling, and adaptation, on the output QoE score of the model. Therefore, parameter studies are conducted using a reference implementation of P.1203, and the model response to variations of the input QoE factors are compared to results of previous QoE studies in order to get a deeper understanding of the standardized model and its inherent weighting of the QoE factors of HAS.
Horst-Schaper, G., Schaper, P.: [POSTER] Verletzungen mit infektiösem Material Ein Überblick über die Unfallmeldungen bei einem Maximalversorger in den Jahren 2001 bis 2017.32. Freiburger Symposium Arbeitsmedizin im Gesundheitsdienst (2018).
Metzger, F., Heger, R.: Exploring the Transmission Behaviour of Overwatch: The Source of Lag.30th International Teletraffic Congress (ITC 30) (2018).
This paper explores the full chain of lag contribution factors in a specific online multiplayer game, namely Overwatch: From creating input events over the network and back to displaying the results on the local screen. Together result in the dreaded end-to-end lag. which has a direct impact on the subjective quality one experiences when playing video games. In its investigation, this paper reveals surprising effects in the game's networking behavior that are omitted when colloquially talking about, e.g. a 60 Hz update rate, but must be considered nonetheless. These insights, gained from examining network traces of Overwatch matches that were played on a realistic, resource constrained PC, can then be used to refine end-to-end lag simulation models and reach a better understanding of all responsible components.
Liotou, E., Hoßfeld, T., Moldovan, C., Metzger, F., Tsolkas, D., Passas, N.: The Value of Context-Awareness in Bandwidth-Challenging HTTP Adaptive Streaming Scenarios. In: Ganchev, I., van der Mei, R.D., und van den Berg, H. (hrsg.) Autonomous Control for a Reliable Internet of Services: Methods, Models, Approaches, Techniques, Algorithms, and Tools. Springer International Publishing (2018).
Video streaming has become an indispensable technology in people’s lives, while its usage keeps constantly increasing. The variability, instability and unpredictability of network conditions pose one of the biggest challenges to video streaming. In this chapter, we analyze HTTP Adaptive Streaming, a technology that relieves these issues by adapting the video reproduction to the current network conditions. Particularly, we study how context awareness can be combined with the adaptive streaming logic to design a proactive client-based video streaming strategy. Our results show that such a context-aware strategy manages to successfully mitigate stallings in light of network connectivity problems, such as an outage. Moreover, we analyze the performance of this strategy by comparing it to the optimal case, as well as by considering situations where the awareness of the context lacks reliability.
Metzger, F., Hoßfeld, T., Skorin-Kapov, L., Liotou, E., Pocta, P., Melvin, H., Siris, V., Zgank, A., Jarschel, M.: Context Monitoring for Improved System Performance and QoE. In: Ganchev, I., van der Mei, R.D., und van den Berg, H. (hrsg.) Autonomous Control for a Reliable Internet of Services: Methods, Models, Approaches, Techniques, Algorithms, and Tools. Springer International Publishing (2018).
Whereas some application domains show a certain consensus on the role of system factors, human factors, and context factors, QoE management of multimedia systems and services is still faced with the challenge of identifying the key QoE influence factors. In this chapter, we focus on the potential of enhancing QoE management mechanisms by exploiting valuable context information. To get a good grip on the basics we first discuss a general framework for context monitoring and define context information, including technical, usage, social, economic, temporal, and physical factors. We then iterate the opportunities and challenges in involving context in QoE monitoring solutions, as context may be, e.g., hard to ascertain or very situational. The benefits of including context in QoE monitoring and management are demonstrated through use cases involving video flash crowds as well as online and cloud gaming. Finally, we discuss potential technical realizations of context-aware QoE monitoring and management derived based on the SDN paradigm.
Iffländer, L., Geissler, S., Walter, J., Beierlieb, L., Kounev, S.: Addressing Shortcomings of Existing DDoS Protection Software Using Software-Defined Networking.9th Symposium on Software Performance 2018 (SSP'18). , Hildesheim, Germany (2018).
DDoS attacks are becoming increasingly frequent and violent. A typical type of attack is the TCP SYN flood, inhibiting a server from opening new TCP connections. Current countermeasures to this attack introduce inefficiencies by either reducing computing resources on the service host or creating new network bottlenecks. In this work, we present a novel approach to mitigate TCP SYN flood attacks using software-defined networking. We perform an initial evaluation of a proof-of-concept implementation that exhibits performance measures close to existing countermeasures while circumventing their inefficiencies.
Ring, M., Landes, D., Hotho, A.: Detection of slow port scans in flow-based network traffic.PLOS ONE.13,1-18 (2018).
Frequently, port scans are early indicators of more serious attacks. Unfortunately, the detection of slow port scans in company networks is challenging due to the massive amount of network data. This paper proposes an innovative approach for preprocessing flow-based data which is specifically tailored to the detection of slow port scans. The preprocessing chain generates new objects based on flow-based data aggregated over time windows while taking domain knowledge as well as additional knowledge about the network structure into account. The computed objects are used as input for the further analysis. Based on these objects, we propose two different approaches for detection of slow port scans. One approach is unsupervised and uses sequential hypothesis testing whereas the other approach is supervised and uses classification algorithms. We compare both approaches with existing port scan detection algorithms on the flow-based CIDDS-001 data set. Experiments indicate that the proposed approaches achieve better detection rates and exhibit less false alarms than similar algorithms.
Lange, S.: Optimization of Controller Placement and Information Flow in Softwarized Networks, (2018).
Zehe, A., Schlör, D., Henny-Krahmer, U., Becker, M., Hotho, A.: A White-Box Model for Detecting Author Nationality by Linguistic Differences in Spanish Novels.DH. ADHO (2018).
Steurer, F.: Optimization of Scheduling Mechanisms for Crowdsourcing Tasks Considering Time-dependent System Parameters, (2018).
Nguyen-Ngoc, A.: On Performance Assessment of Control Mechanisms and Virtual Components in SDN-based Networks, (2018).
Janowski, K., Ritschel, H., Lugrin, B., Andru0027e, E.: Sozial interagierende Roboter in der Pflege. In: Bendel, O. (hrsg.) Pflegeroboter. S. 63-87. Springer Fachmedien Wiesbaden, Wiesbaden (2018).
In naher Zukunft werden Roboter immer häufiger in den Lebensbereichen von Alltagsnutzerinnen und -nutzern anzutreffen sein. Sehr deutlich wird dies am Beispiel von Haushalts- und Pflegerobotern, denen im Hinblick auf eine alternde Gesellschaft verstärkt die Rolle des Mitbewohners und Weggefährten zukommen wird. Damit einher geht der Wunsch, die Mensch-Roboter-Kommunikation menschzentrierter zu gestalten. Es geht nicht mehr lediglich um die effiziente Durchführung von Aufgaben, sondern auch darum, für den Menschen ein angenehmes Interaktionserlebnis zu schaffen und ein Vertrauensverhältnis zu dem Roboter herzustellen. Der nachfolgende Artikel diskutiert den aktuellen Stand in Forschung und Entwicklung im Bereich sozial interagierender Roboter, die über multimodale soziale Hinweisreize mit pflegebedürftigen Menschen kommunizieren.
Seufert, M., Tran-Gia, P.: Quality of Experience and Access Network Traffic Management of HTTP Adaptive Video Streaming.IEEE/IFIP Network Operations and Management Symposium (NOMS), Best Dissertation Award. , Taipei, Taiwan (2018).
The thesis focuses on Quality of Experience (QoE) of HTTP adaptive video streaming (HAS) and traffic management in access networks to improve the QoE of HAS. First, the QoE impact of adaptation parameters and time on layer was investigated with subjective crowdsourcing studies. The results were used to compute a QoE-optimal adaptation strategy for given video and network conditions. This allows video service providers to develop and benchmark improved adaptation logics for HAS. Furthermore, the thesis investigated concepts to monitor video QoE on application and network layer, which can be used by network providers in the QoE-aware traffic management cycle. Moreover, an analytic and simulative performance evaluation of QoE-aware traffic management on a bottleneck link was conducted. Finally, the thesis investigated socially-aware traffic management for HAS via Wi-Fi offloading of mobile HAS flows. A model for the distribution of public Wi-Fi hotspots and a platform for socially-aware traffic management on private home routers was presented. A simulative performance evaluation investigated the impact of Wi-Fi offloading on the QoE and energy consumption of mobile HAS.
Lautenschlager, F., Becker, M., Steininger, M., Hotho, A.: EveryAware Gears: A Tool to visualize and analyze all types of Citizen Science Data. In: Burghardt, D., Chen, S., Andrienko, G., Andrienko, N., Purves, R., und Diehl, A. (hrsg.) Proceedings of VGI Geovisual Analytics Workshop, colocated with BDVA 2018. KOPS (2018).
Flittner, M., Bauer, R., Rizk, A., Geissler, S., Zinner, T., Zitterbart, M.: Taming the complexity of artifact reproducibility.Proceedings of the Reproducibility Workshop (2018).
Reproducing research results, as it is required for peer review, can be a time-consuming and difficult task. In this work, we propose three approaches to improve the way of how research results can be substantiated and discuss their applicability. Our proposals are based on a brief study on evaluation methods (for SDN research) and insights from a comprehensive discussion on reproducibility.
Bruschke, J., Maiwald, F., Münster, S., Niebling, F.: Browsing and Experiencing Repositories of Spatially Oriented Historic Photographic Images.Studies in Digital Heritage.2,138-149 (2018).
Popp, C.: Analysis of WebRTC Video Communications in a Cloud Testbed Setup, (2018).
Karagkioules, T., Tsilimantos, D., Valentin, S., Wamser, F., Zeidler, B., Seufert, M., Loh, F., Tran-Gia, P.: A Public Dataset for YouTube’s Mobile Streaming Client.Network Traffic Measurement and Analysis Conference (TMA). , Vienna, Austria (2018).
Gölz, J.: Evaluation of the Movement Synchronization of Unreal Engine 4, (2018).
The Quality of Service and associated Quality of Experience that networked games provide to a user are susceptible to many influences. Network conditions are a known factor, when it comes to evaluating the synchronization of clients that partake in the same game, as well as the server. Compared to prior work, that either only focused on a small parameter space or used theoretical approaches that did not factor in the effects different game and engine settings can have, this was the target of this thesis. By implementing a fully automated testbed, utilizing an Unreal Engine 4 game prototype, a multitude of different parameter sets could be tested and evaluated. This was done by observing character locations and replicated movement information, and printing them to log files. Instead of querying humans for perceived QoE, spatial and temporal differences between replicated characters and their movement was measured. When evaluating these measurements, insights regarding parameter dependencies and critical measurement influences were gained. This for example includes the necessity of an advanced, unified character movement model to improve evaluation potential.
Jannidis, F., Konle, L., Zehe, A., Hotho, A., Krug, M.: Analysing Direct Speech in German Novels.DHd 2018 (2018).
Becker, M., Lautenschlager, F., Hotho, A.: Air Trails -- Urban Air Quality Campaign Exploration Patterns. (2018).
Seufert, M.: A Fair Share for All: Novel Adaptation Logic for QoE Fairness of HTTP Adaptive Video Streaming., 14th International Conference on Network and Service Management (CNSM), Best Paper Award, Rome, Italy (2018).
Schöch, C., Calvo, J., Zehe, A., Hotho, A.: Burrows Zeta: Varianten und Evaluation.DHd 2018 (2018).
Seufert, M.: Studying the Impact of HAS QoE Factors on the Standardized QoE Model P.1203., 3rd Workshop on QoE-based Analysis and Management of Data Communication Networks (Internet-QoE), Vienna, Austria (2018).
Bergmann, K., Rull, M. del M.C., Lugrin, B.: A Pilot Study on Adaptive Gesture Use in Interaction with Non-native Listeners.Proceedings of the 4th International Workshop on Multimodal Analyses Enabling Artificial Agents in Human-Machine Interaction. S. 26-32. ACM (2018).
Given that human speakers adapt their communicative behavior towards non-native listeners -- a phenomenon known as foreigner talk or teacher talk -- the communicative behavior of an interactive, intelligent virtual agent (IIVA) should also to be adaptive towards the needs of non-native listeners. To investigate the question whether it makes sense to distinguish diferent degrees of language proficiency in non-native addressees when designing communicative behavior skills for IIVAs in mixed-cultural settings, we present first results from a pilot study that is meant to prepare a comprehensive corpus collection. Native speakers of German were asked to explain given German terms to non-native speakers of either low or intermediate language proficiency in German. Results showed significant differences in gesture frequency and also in the types and size of gestures being used, depending on the language proficiency of the non-native listener.
Seufert, M.: A Wrapper for Automatic Measurements with YouTube’s Native Android App., Network Traffic Measurement and Analysis Conference (TMA), Vienna, Austria (2018).
Hoßfeld, T., Metzger, F., Rossi, D.: Speed Index: Relating the Industrial Standard for User Perceived Web Performance to Web QoE.Proceedings of the 10th International Conference on Quality of Multimedia Experience (QoMEX 2018). , Sardinia, Italy (2018).
Schwarzmann, S., Blenk, A., Dobrijevic, O., Jarschel, M., Hotho, A., Zinner, T., Wamser, F.: Big-Data Helps SDN to Improve Application Specific Quality of Service.Big Data and Software Defined Networks. IET (2018).
This chapter first provides an outline of the current results in the domains of: (a) quality-of-service (QoS) / quality-of-experience (QoE) control and management (CaM) for real-time multimedia services that is supported by software-defined networking (SDN), and (b) big data analytics and methods that are used for QoS/QoE CaM. Then, three specific use case scenarios with respect to video streaming services are presented, so as to illustrate the expected benefits of incorporating big data analytics into SDN-based CaM for the purposes of improving or optimizing QoS/QoE. In the end, we describe our vision and a high-level view of an SDN-based architecture for QoS/QoE CaM that is enriched with big data analytics' functional blocks and summarize corresponding challenges.
Kibanov, M., Becker, M., Müller, J., Atzmueller, M., Hotho, A., Stumme, G.: Adaptive kNN Using Expected Accuracy for Classification of Geo-Spatial Data.Proc. 33rd ACM Symposium On Applied Computing. ACM Press, New York, NY, USA (2018).
Korger, A., Baumeister, J.: The SECCO Ontology for the Retrieval and Generation of Security Concepts.ICCBR 2018 - 26th International Conference on Case-Based Reasoning. Springer, Stockholm, Sweden (2018).
Borchert, K., Lange, S., Zinner, T., Hirth, M.: Identification of Delay Thresholds Representing the Perceived Quality of Enterprise Applications.The 2nd International Workshop on Quality of Experience Management. , Sardinia, Italy (2018).
Metter, C., Burger, V., Hu, Z., Pei, K., Wamser, F.: Towards an Active Probing Extension for the ONOS SDN Controller.2018 28th International Telecommunication Networks and Applications Conference (ITNAC) (ITNAC 2018). S. 8. , Sydney, Australia (2018).
Network monitoring is a complex task and is always a trade-off between granularity of information and the performance impact of the monitoring itself on the network. SDN controllers, such as the ONOS SDN controller make this challenge easier as they can supply centralized information over the whole network. In our previous work we mathematically analyzed the built-in detection mechanism of ONOS and revealed a lack of detection performance and the vulnerability of this process to jitter. These results were also verified by measurements. In this paper we present an Active Probing extension for the ONOS SDN controller that overcomes these shortcomings by emitting probing packets that are transmitted through the network. Statistics over a history of those packets allow for the detection of packet loss. The evaluation by the means of measurements proves the benefits in terms of detection performance and controller load of this application. Furthermore, our extension is able to detect jitter being present in the network and to automatically adapt the probing process to these conditions.
Niebling, F., Bruschke, J., Latoschik, M.E.: Browsing Spatial Photography for Dissemination of Cultural Heritage Research Results using Augmented Models. In: Sablatnig, R. und Wimmer, M. (hrsg.) Eurographics Workshop on Graphics and Cultural Heritage. The Eurographics Association (2018).
Bruschke, J., Niebling, F., Wacker, M.: Visualization of Orientations of Spatial Historical Photographs. In: Sablatnig, R. und Wimmer, M. (hrsg.) Eurographics Workshop on Graphics and Cultural Heritage. The Eurographics Association (2018).
Bocerov, M.: Videokompressionsverfahren und ihre Eignung für Adaptives Videostreaming, (2018).
Chan, T.M., van Dijk, T.C., Fleszar, K., Spoerhase, J., Wolff, A.: Stabbing Rectangles by Line Segments -- How Decomposition Reduces the Shallow-Cell Complexity.Proc. 29th International Symposium on Algorithms and Computation (ISAAC'18) (2018).
Baumeister, J.: Evaluation of Configuration Knowledge in Industrial Manufacturing.Lernen. Wissen. Daten. Analysen. (LWDA 2018). , Mannheim (2018).
Roth, D., Wienrich, C.: Effects of Media Immersiveness on the Perception of Virtual Characters. In: Dörner, R., Grimm, P., und Geiger, C. (hrsg.) Proceedings of the 15th Workshop on Virtual and Augmented Reality of the GI Special Interest Group VR/AR (2018).
Virtual characters are widely used in digital media and entertainment, and become more frequent in Virtual Reality (VR) applications. Multiple previous works assessed the perception of virtual characters. Yet, a comparison of the effects of non-immersive and immersive settings on character perception and affect recognition has not been presented. Therefore, we conducted a mixed-design study, that assessed the perception of virtual characters in a desktop setting compared to an immersive VR setting. The piloting findings revealed that although typical evaluation dimensions such as humanness or eeriness did not differ significantly, socially related judgments such as sympathy, attractiveness, and trust showed significant differences between the media. We conclude that these dimensions need further assessments, and suggest that pretesting may be done best in the target media.
Schwarzmann, S., Zinner, T., Sieber, C., Geissler, S.: Evaluation of the Benefits of Variable Segment Durations for Adaptive Streaming.The 2nd International Workshop on Quality of Experience Management. , Sardinia, Italy (2018).
HTTP Adaptive Streaming (HAS) is the de-facto standard for video delivery over the Internet. It enables the dynamic adaptation of video quality by splitting the video clip into small segments and providing multiple quality levels per segment. Current HAS streaming services typically utilize segments of equal durations. However, this leads to video encoding overhead as segments have to start with I-frames, independently of the encoded video content. In this paper we evaluate the prospects of variable segment durations, where video segments are aligned to the video characteristics. We evaluate the reduction of the encoding overhead and investigate its impact on the stalling probability using a theoretical model. It turns out that the variable approach outperforms the fixed approach in 86% of the evaluated cases with respect to video stalls.
Roth, D., Kullmann, P., Bente, G., Gall, D., Latoschik, M.E.: Effects of Hybrid and Synthetic Social Gaze in Avatar-Mediated Interactions.Adjunct Proceedings of the 17th IEEE International Symposium on Mixed and Augmented Reality (ISMAR). IEEE, ACM (2018).
Human gaze is a crucial element in social interactions and therefore an important topic for social Augmented, Mixed, and Virtual Reality (AR,MR,VR) applications. In this paper we systematically compare four modes of gaze transmission: (1) natural gaze, (2) hybrid gaze, which combines natural gaze transmission with a social gaze model, (3) synthesized gaze, which combines a random gaze transmission with a social gaze model, and (4) purely random gaze. Investigating dyadic interactions, results show a linear trend for the perception of virtual rapport, trust, and interpersonal attraction, suggesting that these measures increase with higher naturalness and social adequateness of the transmission mode. We further investigated the perception of realism as well as the resulting gaze behavior of the avatars and the human participants. We discuss these results and their implications.
Oberdörfer, S., Fischbach, M., Latoschik, M.E.: Effects of VE Transition Techniques on Presence, IVBO, Efficiency, and Naturalness.Proceedings of the 6th Symposium on Spatial User Interaction. ACM (2018).
Roth, D., Mal, D., Purps, C.F., Kullmann, P., Latoschik, M.E.: Injecting Nonverbal Mimicry with Hybrid Avatar-Agent Technologies: A Naïve Approach.Proceedings of the 6th ACM Symposium on Spatial User Interaction (SUI). ACM (2018).
Humans communicate to a large degree through nonverbal behavior. Nonverbal mimicry, i.e., the imitation of another’s behavior can positively affect the social interactions. In virtual environments, user behavior can be replicated to avatars, and agent behaviors can be artificially constructed. By combining both, hybrid avatar-agent technologies aim at actively mediating virtual communication to foster interpersonal understanding and rapport.We present a naïve prototype, the “Mimicry Injector”, that injects artificial mimicry in real-time virtual interactions. In an evaluation study, two participants were embodied in a Virtual Reality (VR) simulation, and had to perform a negotiation task. Their virtual characters either a) replicated only the original behavior or b) displayed the original behavior plus induced mimicry. We found that most participants did not detect the modification. However, the modification did not have a significant impact on the perception of the communication.
Maiwald, F., Schneider, D., Henze, F., Münster, S., Niebling, F.: FEATURE MATCHING OF HISTORICAL IMAGES BASED ON GEOMETRY OF QUADRILATERALS.International Archives of the Photogrammetry, Remote Sensing & Spatial Information Sciences.42, (2018).
Bruschke, J., Niebling, F.: Räumliches Durchsuchen von Repositorien historischer Fotografien. In: Dachselt, R. und Weber, G. (hrsg.) Mensch und Computer 2018 - Workshopband. Gesellschaft für Informatik e.V., Bonn (2018).
Rapp, D., Niebling, F., Latoschik, M.E.: The impact of Pokemon Go and why it’s not about Augmented Reality – Results from a Qualitative Survey. In: Worlds, 10th I.E.E.E.I.C. on V. und for Serious Applications (VS-Games), (hrsg.) Proceedings of the 10th IEEE International Conference on Virtual Worlds for Serious Applications (VS-Games). IEEE (2018).
Lugrin, B., Bergmann, K., Dippold, J.: Social Robots as a Means of Integration? An Explorative Acceptance Study considering Gender and Non-verbal Behaviour.Proceedings of the International Conference on Intelligent Robots and Systems. S. 2026-2032. IEEE (2018).
Niebling, F., Latoschik, M.E.: Browsing Spatial Photography using Augmented Models.Proceedings of the 17th IEEE International Symposium on Mixed and Augmented Reality (ISMAR). IEEE, ACM (2018).
Fischbach, M., Brandt, M., Zimmerer, C., Lugrin, J.-L., Latoschik, M.E., Lugrin, B.: Follow the White Robot - A Role-Playing Game with a Robot Game Master.Proceedings of the 17th Conference on Autonomous Agents and MultiAgent Systems. ACM, Stockholm, Sweden (2018).
We describe a social robot acting as a game master in an interactive tabletop role-playing game. The Robot Game Master (RGM) takes on the role of different characters, which the human players meet during the adventure, as well as of the narrator. The demonstration presents a novel software and hardware platform that allows the robot to (1) proactively lead through the storyline and to (2) react to changes in the ongoing game in real-time, while (3) fostering playersu0027 collaborations.
Loh, F., Karagkioules, T., Seufert, M., Zeidler, B., Tsilimantos, D., Tran-Gia, P., Valentin, S., Wamser, F.: A Wrapper for Automated Measurements with YouTube’s Native App, (2018).
This demo introduces a wrapper used for automated measurements of mobile video streaming in the Android YouTube app. The difference to traditional measurement techniques is that the measurement is done with the native YouTube app as it is provided in the Google Play Store. In addition to bandwidth or packet loss detection, the QoE of the video stream can be measured and quantified. For this, the amount of quality changes, the current playtime, the buffer level, and statistics like video and audio format are captured. Thus, detailed relationships between network parameters and streaming behavior based on many factors can be detected within the native app available in the Play Store.
Lugrin, B., Bartl, A., Striepe, H., Lax, J., Toriizuka, T.: Do I act familiar? Investigating the Similarity-Attraction Principle on Culture-specific Communicative behaviour for Social Robots.Proceedings of the International Conference on Intelligent Robots and Systems. S. 2033-2039. IEEE (2018).
Culture, amongst other individual and social factors, plays a crucial role in human-human interactions. If robots should become a part of our society, they should be able to act in culture-specific manners as well. In this paper, we showcase the implementation of a cultural dichotomy, namely individualism vs. collectivism, in a social robotsu0027 conversation. Presenting these conversations to human observers from Germany and Japan, we investigate whether the implemented differences are recognized as such, and whether stereotypical culture-specific behaviours that correspond to the observersu0027 cultural background is preferred. Results suggest that the manipulations in behaviour had the intended effect, but are not reflected in personal preferences.
Oberdörfer, S., Latoschik, M.E.: Effective Orbital Mechanics Knowledge Training Using Game Mechanics. In: IEEE, (hrsg.) Proceedings of the 10th International Conference on Virtual Worlds and Games for Serious Applications (VS Games 2018). IEEE (2018).
Navarro Bullock, B., Hotho, A., Stumme, G.: Accessing Information with Tags: Search and Ranking. In: Brusilovsky, P. und He, D. (hrsg.) Social Information Access: Systems and Technologies. S. 310--343. Springer International Publishing, Cham (2018).
With the growth of the Social Web, a variety of new web-based services arose and changed the way users interact with the internet and consume information. One central phenomenon was and is tagging which allows to manage, organize and access information in social systems. Tagging helps to manage all kinds of resources, making their access much easier. The first type of social tagging systems were social bookmarking systems, i.e., platforms for storing and sharing bookmarks on the web rather than just in the browser. Meanwhile, (hash-)tagging is central in many other Social Media systems such as social networking sites and micro-blogging platforms. To allow for efficient information access, special algorithms have been developed to guide the user, to search for information and to rank the content based on tagging information contributed by the users.
Casas, P., Seufert, M., Wehner, N., Schwind, A., Wamser, F.: Enhancing Machine Learning based QoE Prediction by Ensemble Models.3rd Workshop on QoE-based Analysis and Management of Data Communication Networks (Internet-QoE). , Vienna, Austria (2018).
The number of smartphones connected to wireless networks and the volume of wireless network traffic generated by such devices have dramatically increased in the last few years, making it more challenging to tackle wireless network monitoring applications. The high-dimensionality of network data provided by current smartphone devices opens the door to the massive application of machine learning approaches to improve different wireless networking applications. In this paper we study the specific problem of Quality of Experience (QoE) prediction for popular smartphone apps, using machine learning models and in-smartphone measurements. We evaluate and compare different models for the analysis of smartphone generated data, including single models as well as machine learning ensembles such as bagging, boosting and stacking. Results suggest that, while decision-tree based models are the most accurate single models to predict QoE, ensemble learning models, and in particular stacking ones, are capable to significantly increase accuracy prediction and overall classification performance.
Schwarzmann, S., Blenk, A., Dobrijevic, O., Jarschel, M., Hotho, A., Zinner, T., Wamser, F.: Big-Data Helps SDN to Improve Application Specific Quality of Service.Big Data and Software Defined Networks. IET (2018).
This chapter first provides an outline of the current results in the domains of: (a) quality-of-service (QoS) / quality-of-experience (QoE) control and management (CaM) for real-time multimedia services that is supported by software-defined networking (SDN), and (b) big data analytics and methods that are used for QoS/QoE CaM. Then, three specific use case scenarios with respect to video streaming services are presented, so as to illustrate the expected benefits of incorporating big data analytics into SDN-based CaM for the purposes of improving or optimizing QoS/QoE. In the end, we describe our vision and a high-level view of an SDN-based architecture for QoS/QoE CaM that is enriched with big data analytics' functional blocks and summarize corresponding challenges.
Lugrin, J.-L., Kern, F., Schmidt, R., Kleinbeck, C., Roth, D., Daxer, C., Feigl, T., Mutschler, C., Latoschik, M.E.: A Location-Based VR Museum. In: IEEE, (hrsg.) Proceedings of the 10th IEEE International Conference on Virtual Worlds for Serious Applications (VS-Games). IEEE (2018).
Dinh-Xuan, L., Seufert, M., Wamser, F., Vassilakis, C., Zafeiropoulos, A., Tran-Gia, P.: Performance Evaluation of Service Functions Chain Placement Algorithms in Edge Cloud.30th International Teletraffic Congress (ITC30). , Vienna, Austria (2018).
The emergence of Network Function Virtualization (NFV) paradigm has become a potential solution dealing with the rapid growth of the global Internet traffic in the last decades. There, network appliances are transformed into Virtual Network Functions (VNF) running on a standard server. This promises to significantly reduce overall cost and energy consumption. Additionally, hardware-based network function chain is replaced by a chain of the VNFs, called Service Function Chain (SFC). The expected benefit of SFC is the reduction in the complexity when deploying heterogeneous network services. However, the considerable drawback of SFC is the distribution of the VNFs over different hosts. An inefficient placement of VNFs can induce a high latency within the chain and wasted server resources. In this work, we propose four placement algorithms that aim to efficiently place the SFC in servers with regard to minimizing service response time and resource utilization. Herein, heuristic approaches are evaluated against optimal solutions for the placement problems, which are formulated by using Integer Linear Programming. We evaluate and compare these placement strategies in a simulator. Our result shows that the optimized solutions produce lowest service response time and least server utilization in all types of simulated SFCs. On the other hand, the heuristic algorithms are also able to come close to the optimum by simple placing rules.
Wamser, F., Lombardo, C., Vassilakis, C., Dinh-Xuan, L., Lago, P., Bruschi, R., Tran-Gia, P.: Orchestration and Monitoring in Fog Computing for Personal Edge Cloud Service Support.2018 IEEE International Symposium on Local and Metropolitan Area Networks (LANMAN) (2018).
Oberdörfer, S., Latoschik, M.E.: Effectivity of Affine Transformation Knowledge Training Using Game Mechanics. In: IEEE, (hrsg.) Proceedings of the 10th International Conference on Virtual Worlds and Games for Serious Applications (VS Games 2018). IEEE (2018).
Nogatz, F., Kalkus, J., Seipel, D.: Web-based Visualisation for Definite Clause Grammars using Prolog Meta-Interpreters: System Description.Proceedings of the 20th International Symposium on Principles and Practice of Declarative Programming (2018).
Definite Clause Grammars (DCGs) are a convenient way to describe lists in Prolog. They are a common mean to specify grammars for natural language processing and to parse formal languages. Despite its long history, tools dedicated to the development and debugging of DCGs are rare. In this paper, we present an interactive, web-based tool to visualise the execution of a DCG. To collect the required information from SWI-Prolog, we discuss several techniques, including meta-interpreters, trace interceptors, and term expansions.
Lugrin, J.-L., Charles, F., Habel, M., Dudaczy, H., Oberdörfer, S., Matthews, J., Porteous, J., Wittmann, A., Seufert, C., Grafe, S., Latoschik, M.E.: Benchmark Framework for Virtual Students’ Behaviours. In: of the 17th International Conference on Autonomous Agents, P. und 2018), M.S. (A.A.M.A.S. (hrsg.) Proceedings of the 17th Conference on Autonomous Agents and MultiAgent Systems. S. 2236–2238. ACM (2018).
Schwind, A., Wamser, F., Gensler, T., Seufert, M., Casas, P., Tran-Gia, P.: Streaming Characteristics of Spotify Sessions.The 2nd International Workshop on Quality of Experience Management. , Sardinia, Italy (2018).
Internet Service Providers need a thorough understanding of a service to maximize the Quality of Experience (QoE) of their customers by network management. Instead of quantifying the user satisfaction with long and cost-intensive subjective user studies, the QoE can often be estimated with the help of dedicated measurements of application and network parameters. We designed a QoE measurement tool for the popular audio streaming service Spotify that runs inside a Docker software container. The container is able to run headlessly as active measurement probe and emulates a user who is streaming audio files via Spotify. While streaming, network and application parameters are collected that have a high correlation to the user's QoE. The results of the measurements are used to characterize audio streaming in Spotify on application and network layer, and to evaluate important QoE factors.
Lugrin, J.-L., Dudaczy, H., Latoschik, M.E.: Low-Frequency Stress Elicitation for VR Training. In: Worlds, 10th I.E.E.E.I.C. on V. und for Serious Applications (VS-Games), (hrsg.) Proceedings of the 10th IEEE International Conference on Virtual Worlds for Serious Applications (VS-Games). IEEE (2018).
Nogatz, F., Frühwirth, T., Seipel, D.: CHR.js: A CHR Implementation in JavaScript.Rules and Reasoning. S. 131-146. Springer (2018).
Constraint Handling Rules (CHR) is usually compiled to logic programming languages. While there are implementations for imperative programming languages such as C and Java, its most popular host language remains Prolog. In this paper, we present CHR.js, a CHR system implemented in JavaScript, that is suitable for both the server-side and interactive client-side web applications. CHR.js provides (i) an interpreter, which is based on the asynchronous execution model of JavaScript, and (ii) an ahead-of-time compiler, resulting in synchronous constraint solvers with better performances. Because of the great popularity of JavaScript, CHR.js is the first CHR system that runs on almost all and even mobile devices, without the need for an additional runtime environment. As an example application we present the CHR.js Playground, an offline-capable web-interface which allows the interactive exploration of CHRs in every modern browser.
Chaplick, S., De, M., Ravsky, A., Spoerhase, J.: Approximation Schemes for Geometric Coverage Problems.Proc. 26th Annual European Symposium on Algorithms (ESA'18). S. 17:1--17:15 (2018).
Pfeifer, A., Lugrin, B.: Female Robots as Role-models? - the Influence of Robot Gender and Learning Materials on Learning Success.Int. Conf. on Artificial Intelligence in Education (AIED 2018). S. 276-280. Springer (2018).
Wollek, A.: Validierung eines generischen HAS-Modells für unterschiedliche Heuristiken., (2018).
Seufert, M., Zeidler, B., Wamser, F., Karagkioules, T., Tsilimantos, D., Loh, F., Tran-Gia, P., Valentin, S.: A Wrapper for Automatic Measurements with YouTube's Native Android App.Network Traffic Measurement and Analysis Conference (TMA). , Vienna, Austria (2018).
YouTube is one of the most popular and demanding services in the Internet today. Thereby, a large portion of this traffic is generated by YouTube's mobile app. While past studies have shown how to monitor browser-based streaming on desktop PCs (e.g., YoMo) or mobile devices (e.g., YoMoApp), streaming in the native app has not been monitored yet. This paper presents an automated framework for monitoring the streaming in YouTube's native app for Android. The concept is based on a wrapper application and the Android Debug Bridge (adb), and can be also extended to automatic measurements with other apps. For YouTube, it allows to collect application-layer streaming data, such as current playtime, buffered playtime, video encoding, and quality switches. These data can be complemented with network measurements on the mobile access link to obtain a holistic view on mobile YouTube streaming on Android devices. In addition to describing the software design and testbed setup, this paper discusses an experimental measurement. This study analyzes the streaming in the native YouTube app and compares it to the streaming from the mobile YouTube website via YoMoApp.
Poignée, F.: Influence of Tension on QoE in Video Streaming, (2018).
Oberdörfer, S., Latoschik, M.E.: Gamified Knowledge Encoding: Knowledge Training Using Game Mechanics. In: IEEE, (hrsg.) Proceedings of the 10th International Conference on Virtual Worlds and Games for Serious Applications (VS Games 2018). IEEE (2018).
Ziegler, P., Roth, D., Knote, A., Kreuzer, M., von Mammen, S.: Simulator Sick but still Immersed: A Comparison of Head-Object Collision Handling and their Impact on Fun, Immersion, and Simulator Sickness. (2018).
We compared three techniques for handling head-object collisions in room-scale virtual reality (VR). We developed a game whose mechanics induce such collisions which we either addressed (1) not at all, (2) by fading the screen information to black, or (3) by restricting translation, i.e. correcting the virtual offset in such a way that no penetration occurred. We measured these conditions’ impact on simulator sickness, fun, and immersion perception. We found that the translation-restricted method yielded the greatest immersion value but also contributed the most to simulator sickness.
Supervisor: Lange, S.: Simulative Performance Comparison of an SDN Architecture with External Information Sources, (2018).
Software Defined Networking (SDN) marks a paradigm shift towards an externalized and logically centralized network control plane. Due to the open interfaces of the SDN controller, it is possible to take into account different external information such as measurements regarding link delays and bandwidths from sources like Network Management Systems (NMS). This information can arrive at the controller in different levels of granularity (per-flow, per-port, ...) and at different time scales (once per minute, once per second, event-based, ...). The aim of this thesis consists of evaluating the trade-offs between different information exchange mechanisms with respect to performance gains and the overhead that results from exchanging and processing the external information.
Fleszar, K., Mnich, M., Spoerhase, J.: New Algorithms for Maximum Disjoint Paths Based on Tree-Likeness.Mathematical Programming.171,433--461 (2018).
Roth, D., Schmitt, J., Bloch, C., Frischlich, L., Latoschik, M.E., Bente, G.: Empathy for Avatars: The Influence of Perceived Authenticity on Empathy and Behavioral Intentions.Presentation on the 68th Annual Conference of the International Communication Association (ICA), May 24-28 2018, Prague, Czech Republic (2018).
Yang, J., van der Valk, C., Hoßfeld, T., Redi, J., Bozzon, A.: How do crowdworker communities and microtask markets influenceeach other? A data-driven study on Amazon Mechanical Turk.Université de Fribourg (2018).
Roth, D., Latoschik, M.E., Bloch, C., Bente, G.: When Some Things are Missing: The Quality of Interpersonal Communication in Social Virtual Reality. (2018).
Grigorjew, A., Lange, S., Zinner, T., Tran-Gia, P.: Performance Benchmarking of Network Function Chain Placement Algorithms.19th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems (MMB) (2018).
Janiak, L.: Impact of the measurement design on application behavior of video streaming, (2018).
Hirth, M., Lange, S., Seufert, M., Tran-Gia, P.: Performance Evaluation of Mobile Crowdsensing for Event Detection.Proceedings of the 5th International Workshop on Crowd Assisted Sensing, Pervasive Systems and Communications. , Athens, Greece (2018).
Crowdsensing offers a cost effective way to collect large amounts of sensor data. However, in contrast to fixed sensor deployments, the spatial distribution of the sensors can hardly be influence, as the sensors are carried by participants of the crowdsensing system. This in turn raises the question about the performance of such systems with respect to the detection probability and detection time of spatial events. In order to address this question, we analyze the performance of such a crowdsensing system by means of simulation. We use the traffic infrastructure of a small size city in Germany and simulate the inhabitants’ movement patterns with the well established SUMO mobility generator. Our results show that even if only a small share of inhabitants participates in crowdsensing, events, which have locations that are correlated with the population density, can be easily and quickly detected using such a system. On the contrary, events whose locations are uniformly randomly distributed are much harder to detect using a crowdsensing approach.
Stubenrauch, F.: On the Practicability of SDN in a University Network, (2018).
Contact: Alexej Grigorjew <alexej.grigorjew@informatik.uni-wuerzburg.de> The work should provide an overview of criteria that enable and encourage the use of modern concepts (such as NFV and SDN) in less agile networks with few operators and versatile traffic patterns. It should identify key influence factors that imply success and feasibility of the deployment of modern devices. In addition, a select choice of use cases shall be investigated by implementing them with modern utilities, and evaluated thereby to gain further insights.
Waltemate, T., Gall, D., Roth, D., Botsch, M., Latoschik, M.E.: The Impact of Avatar Personalization and Immersion on Virtual Body Ownership, Presence, and Emotional Response.IEEE Transactions on Visualization and Computer Graphics (TVCG).24,1643-1652 (2018).
This article reports the impact of the degree of personalization and individualization of usersu0027 avatars as well as the impact of the degree of immersion on typical psychophysical factors in embodied Virtual Environments. We investigated if and how virtual body ownership (including agency), presence, and emotional response are influenced depending on the specific look of usersu0027 avatars, which varied between (1) a generic hand-modeled version, (2) a generic scanned version, and (3) an individualized scanned version. The latter two were created using a state-of-the-art photogrammetry method providing a fast 3D-scan and post-process workflow. Users encountered their avatars in a virtual mirror metaphor using two VR setups that provided a varying degree of immersion, (a) a large screen surround projection (CAVE) and (b) a head-mounted display (HMD). We found several significant as well as a number of notable effects. First, personalized avatars significantly increase body ownership, presence, and dominance compared to their generic counterparts, even if the latter were generated by the same photogrammetry process and hence could be valued as equal in terms of the degree of realism and graphical quality. Second, the degree of immersion significantly increases the body ownership, agency, as well as the feeling of presence. These results substantiate the value of personalized avatars resembling usersu0027 real-world appearances as well as the value of the deployed scanning process to generate avatars for VR-setups where the effect strength might be substantial, e.g., in social Virtual Reality (VR) or in medical VR-based therapies relying on embodied interfaces. Additionally, our results also strengthen the value of fully immersive setups which, today, are accessibly for a variety of applications due to the widely available consumer HMDs.
Gray, N.: Evaluation of Offloading Firewall Rules with P4, (2018).
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.
Katzmareck, M.: Identifying Relationship Pattern within WhatsApp, (2018).
Supervisor: Grigorjew, A.: Performance and Parameter Evaluation of P4 Devices (Prakt.), (2018).
Contact: Alexej Grigorjew <alexej.grigorjew@informatik.uni-wuerzburg.de> P4 is a simple programming language for switching devices that allows free configuration of protocols, matching fields, actions, and control flow in compatible hardware and software implementations. This leads to a wide range of different configurations and different realizations of their behavior by different vendors, coupled with tight performance requirements in the data plane. In this work, the influence of various parameters on the performance of P4 implementations shall be measured. In particular, a software implementation and a Netronome P4 hardware NIC shall be compared and evaluated with regard to their program's impact on measures such as throughput and processing delay.
van Dijk, T.C., Lipp, F., Markfelder, P., Wolff, A.: Computing Storyline Visualizations with Few Block Crossings. In: Frati, F. und Ma, K.-L. (hrsg.) Proc. 25th Int. Sympos. Graph Drawing Network Vis. (GD'17). S. 365--378. Springer-Verlag (2018).
Nalepa, G.J., Baumeister, J.: Synergies between Knowledge Engineering and Software Engineering.Springer (2018).
Stauffert, J.-P., Niebling, F., Latoschik, M.E.: Effects of Latency Jitter on Simulator Sickness in a Search Task.25th IEEE Conference on Virtual Reality and 3D User Interfaces (IEEE VR). S. 121-127 (2018).
Low latency is a fundamental requirement for Virtual Reality (VR) systems to reduce the potential risks of cybersickness and to increase effectiveness, efficiency and user experience. In contrast to the effects of uniform latency degradation, the influence of latency jitter on user experience in VR is not well researched, although todayu0027s consumer VR systems are vulnerable in this respect. In this work we report on the impact of latency jitter on cybersickness in HMD-based VR environments. Test subjects are given a search task in Virtual Reality, provoking both head rotation and translation. One group experienced artificially added latency jitter in the tracking data of their head-mounted display. The introduced jitter pattern was a replication of a real-world latency behavior extracted and analyzed from an existing example VR-system. The effects of the introduced latency jitter were measured based on self-reports simulator sickness questionnaire (SSQ) and by taking physiological measurements. We found a significant increase in self-reported simulator sickness. We therefore argue that measure and control of latency based on average values taken at a few time intervals is not enough to assure a required timeliness behavior but that latency jitter needs to be considered when designing experiences for Virtual Reality.
Gall, D., Latoschik, M.E.: The Effect of Haptic Prediction Accuracy on Presence.Proceedings of the 25th IEEE Virtual Reality (VR) conference (2018).
This paper reports on the effect of visually-anchored prediction accuracy of haptic information on the perceived presence of virtual environments. We designed an experiment which explicitly prevented confounding factors potentially introduced by virtual body ownership and/or agency. The experimental design consisted of two main conditions defining congruent vs incongruent visual and haptic cues. Presence was measured during as well as after exposure. A distance estimation task solely based on motor action and the visually-anchored spatial model of the environment was executed to control for perceptual binding. 56 healthy volunteers were randomly assigned to one of two groups in a single-blind mixed-group design study. The study revealed increased presence for high prediction accuracy and decreased presence for low prediction accuracy, while perceptual binding still occurred. The observed effect sizes were in the medium range. The results indicate a significant correlation between prediction accuracy of haptic information and the perceived realness and presence of a virtual environment which gives rise to a discussion about models for dissociative symptom derealisation.
Lange, S., Reinhart, L., Zinner, T., Hock, D., Gray, N., Tran-Gia, P.: Integrating Network Management Information into the SDN Control Plane.IEEE/IFIP Network Operations and Management Symposium (NOMS) (2018).
With software defined networking (SDN), operators benefit from a higher flexibility, cost efficiency, as well as programmability of their networks. Since modern networks are comprised of a multitude of heterogeneous devices and also include non-SDN legacy devices, network management systems (NMSs) are often used in order to monitor and configure the network. Although both, the SDN controller and the NMS, have a centralized view of the network, they operate at different time scales and deal with information at different levels of granularity. In this work, we investigate the impact on the network performance when an NMS regularly provides information to an SDN controller. To this end, we design, implement, and compare three interaction mechanisms based on the ONOS controller. These represent different trade-offs regarding the complexity of the resulting system and its performance. In addition to the default ONOS controller, we develop two extended versions. One performs hash-based load balancing on equal cost paths while the other utilizes external NMS information via ONOS's intent and annotation framework to optimize control plane decisions. In addition to evaluations that show a significant performance improvement when using the optimized controllers, we present a parameter study that highlights the performance impact of network characteristics like the flow interarrival time, the flow duration, and the number of active flows.
Niebling, F., Maiwald, F., Barthel, K., Latoschik, M.E.: 4D Augmented City Models, Photogrammetric Creation and Dissemination. In: Münster, S., Friedrichs, K., Niebling, F., und Seidel-Grzesiu0027nska, A. (hrsg.) Digital Research and Education in Architectural Heritage. S. 196--212. Springer International Publishing, Cham (2018).
The availability of digital image repositories of historical photographs offers new possibilities to historians in their research. In addition to representing a large collection of data records themselves, image archives allow for new methods of research, from large-scale statistical analysis, to algorithmic generation of knowledge, such as historical 3D models, directly from these sources. In this paper, we explore methods to work with digital image libraries, from the creation of 3D or in extension time-annotated 4D models, to the eventual dissemination of research findings in teaching/learning scenarios. We review pedagogical approaches to reach different learning objectives, as well as methods that allow for the inclusion of historic city models employing Augmented Reality in mobile learning environments.
Gray, N.: Evaluation of the Impact of Network Topologies and Applications on Synchronization Strategies of Distributed SDN Controllers, (2018).
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.
van Dijk, T.C., Lipp, F., Markfelder, P., Wolff, A.: Computing Storylines with Few Block Crossings. In: Frati, F. und Ma, K.-L. (hrsg.) Proc. 25th Int. Symp. Graph Drawing & Network Vis. (GD'17). S. 365--378. Springer-Verlag (2018).
Gray, N., Lange, S., Zinner, T., Pfaff, B., Hock, D.: Evaluation of a Distributed Control Plane for Managing Heterogeneous SDN-enabled and Legacy Networks.7th International Conference on Communications and Electronics (ICCE). , Hue, Vietnam (2018).
With the increasing number of devices, protocols and applications, today’s networks are becoming more and more complex. Hence, Software-defined Networking (SDN) tries to ad- dress this issue by separating the data from the control plane and by providing centralized interfaces for network configuration. As legacy devices cannot be replaced instantly due to high costs, both network segments have to be operated in coexistence with defined joints at their edges. To ensure a smooth operation, both controlling instances of these segments are required to exchange information. In this work, we design and implement a data model for storing the information needed to keep the controller and a Network Management System (NMS) synchronized, which are responsible for configuring the SDN-enabled network and the legacy devices respectively. For this, we implement and evaluate a total of three different synchronization strategies by the example of an SDN-based Bring Your Own Device (BYOD) use case. Index Terms—SDN, NMS, Management, Integration, Hetero- geneous Networks, Distributed Control Plane.
Hefter, J.: Analyzing the Streaming Behaviour of a Popular Video-On-Demand Service, (2018).
Sommer, M.: Implementation of a Fuzzing Framework for SDN Security Analysis, (2018).
Schwind, A., Seufert, M.: WhatsAnalyzer: a Tool for Collecting and Analyzing WhatsApp Mobile Messaging Communication Data, (2018).
WhatsAnalyzer is a web-based service, which collects and analyzes chat histories of the mobile messaging application WhatsApp. Thereby, it leverages the e-mail export feature of WhatsApp to obtain the chat histories, which cannot be accessed otherwise due to encrypted storage on the mobile device and end-to-end encrypted transmission over the Internet. Thus, the major asset of the service is that real communication data can be collected without the bias introduced by observing or surveying participants. The collected communication data can be analyzed and provides valuable insights into the communication in WhatsApp and the resulting network traffic. To incentivize users to send chat histories, the privacy of users is respected by anonymizing all communication data. Moreover, some analyses of each chat history can be accessed on a web page by the sender of the chats.
Aschenbrenner, D., Rojkov, M., Leutert, F., Verlinden, J., Lukosch, S., Latoschik, M.E., Schilling, K.: Comparing Different Augmented Reality Support Applications for Cooperative Repair of an Industrial Robot.Proceedings of the International Symposium on Mixed and Augmented Reality (ISMAR) (2018).
Digitization and the growing capabilities of data networks enable companies to perform tasks via remote support, which previously required service personnel to travel. But which mixed reality method leads to better results regarding human factors, grounding and per- formance criteria? This paper reports on a collaborative user study, in which a local worker is guided by a remote expert with the help of different augmented reality methods, specifically see-through HMD, spatial projection, and video-mixing tablet. The performed task is an controller exchange in a switch cabinet of an industrial robot, a task rather typical for failure detection within the field. Our study was conducted in collaboration with a technician school of which 50 technician apprentices participated in our study. Our results show clear advantages of using augmented reality (AR) versus traditional conditions (audio, video, screenshot) to enable remote support. It further gives significant indications for using a projection based AR method.
Byrka, J., Lewandowski, M., Spoerhase, J.: Approximating Node-Weighted k-MST on Planar Graphs.Proc. 16th Workshop on Approximation and Online Algorithms (WAOA'18) (2018).
Loh, F., Wamser, F., Hoßfeld, T., Tran-Gia, P.: Quality of Service Assessment of Live Video Streaming with a Remote-Controlled Drone.IEEE Conference on Network Softwarization. , Montreal, Canada (2018).
Today's networks require a deep understanding of applications to optimize networks, efficiently design networks, and meet traffic demands, application heterogeneity, and application requirements. Current application areas include live video streaming and real-time applications, such as those that are named in 5G use cases with automation, disaster recovery, gaming, and Industry 4.0. In this work, we examine an application scenario with live video streaming and parallel real-time requirements in the uplink for disaster recovery. We study the quality of service (QoS) features of a remote-controlled drone. The drone is controlled via a tablet or smartphone while the video from the camera is transmitted from the drone to the user. There are high demands in both the uplink and downlink direction. The contribution of the work is the measurement of the QoS and application parameters for this scenario and the definition of influencing parameters for the application-layer.
Supervisor: Loh, F.: Evaluation of the Video Call Behavior Using Amazon Echo Show, (2018).
Borchert, K., Hirth, M., Kummer, M., Laitenberger, U., Slivko, O., Viet, S.: Unemployment and Online Labor, (2018).
Nguyen-Ngoc, A., Raffeck, S., Lange, S., Geissler, S., Zinner, T., Tran-Gia, P.: Benchmarking the ONOS Controller with OFCProbe.7th International Conference on Communications and Electronics (ICCE). , Hue, Vietnam (2018).
The increased popularity of Software Defined Networking (SDN) drives the development and research of all involved components. In particular, state-of-the-art SDN controllers are a central part of the resulting network architecture and have a large impact on the performance of the entire network. Hence, it is necessary to quantify various performance indicators of the SDN controller in order to assess its feasibility in the context of different network characteristics such as topology and network size w.r.t. the number of nodes and links. To this end, we extend the open-source controller benchmarking tool OFCProbe with several novel modules that are capable of recording relevant performance metrics and demonstrate their use in the context of benchmarking the ONOS controller. Furthermore, we investigate the impact of different types of topology characteristics on the performance of the controller. In this work, we focus on several performance indicators for SDN controllers. First, the time that the ONOS controller needs to discover the network topology and update its internal representation of the topology. Second, we investigate the duration of the installation of flow rules that are used for reactive path provisioning. Finally, we measure the response time of the controller when dealing with asynchronous messages.
Das, A., Fleszar, K., Kobourov, S., Spoerhase, J., Veeramoni, S., Wolff, A.: Approximating the Generalized Minimum Manhattan Network Problem.Algorithmica.80,1170--1190 (2018).
Chimani, M., Felsner, S., Kobourov, S., Ueckerdt, T., Valtr, P., Wolff, A.: On the Maximum Crossing Number.Journal of Graph Algorithms & Applications.22,67--87 (2018).
Research about crossings is typically about minimization. In this paper, we consider emphmaximizing the number of crossings over all possible ways to draw a given graph in the plane. Alpert et al. [Electron. J. Combin., 2009] conjectured that any graph has a emphconvex straight-line drawing, that is, a drawing with vertices in convex position, that maximizes the number of edge crossings. We disprove this conjecture by constructing a planar graph on twelve vertices that admits a non-convex drawing with more crossings than any convex drawing. Bald et al. [Proc. COCOON, 2016] showed that it is NP-hard to compute the maximum number of crossings of a geometric graph and that the weighted geometric case is NP-hard to approximate. We strengthen these results by showing hardness of approximation even for the unweighted geometric case. We also prove that the unweighted topological case is NP-hard.
Nogatz, F., Kalkus, J.: Declarative XML Schema Validation with SWI-Prolog. In: Seipel, D., Hanus, M., und Abreu, S. (hrsg.) Declarative Programming and Knowledge Management. S. 187-197 (2018).
XML Schema is a well-established mechanism to define the structure and constrain the content of an XML document. While this approach taken by itself is declarative, currently available tools for XML validation are not. In this paper we introduce an implementation of an XSD validator in SWI-Prolog, made publicly available as the package library(xsd). Our approach is based on flattening the XSD and XML documents into Prolog facts. The top-down validation makes great use of Prolog's backtracking and unification capabilities. To ensure the compliance to the XSD standard and to support the test-driven development, we have created a test framework based on the Test Anything Protocol and SWI-Prolog's quasi-quotations.
Roth, D., Mal, D., Polyschev, I., Wiedemann, M., Klöffel, C., Purps, C., To, J., Latoschik, M.E.: Extended Abstract: Artificial Nonverbal Mimicry in Immersive Embodied Social Interactions: Meet the Mimicry Injector.Presentation on the 68th Annual Conference of the International Communication Association (ICA), May 24-28 2018, Prague, Czech Republic. (2018).
Byrka, J., Sornat, K., Spoerhase, J.: Constant-Factor Approximation for Ordered k-Median.Proc. 50th Annual ACM Symposium on the Theory of Computing (STOC'18). S. 620--631 (2018).
Baker, R., Cao, N., Hu, Y., Kaufmann, M., Kobourov, S., Mchedlidze, T., Pupyrev, S., Wolff, A.: Set Visualization Using the Metro Map Metaphor. In: Hu, Y., Micallef, L., Nöllenburg, M., und Rodgers, P. (hrsg.) Scalable Set Visualizations (Dagstuhl Seminar 17332). S. 1--22. Schloss Dagstuhl~-- Leibniz-Zentrum für Informatik (2018).
Chaplick, S., Chimani, M., Cornelsen, S., Da Lozzo, G., Nöllenburg, M., Patrignani, M., Tollis, I.G., Wolff, A.: Planar L-Drawings of Directed Graphs. In: Frati, F. und Ma, K.-L. (hrsg.) Proc. 25th Int. Symp. Graph Drawing & Network Vis. (GD'17). S. 465--478. Springer-Verlag (2018).
Chaplick, S., Kryven, M., Liotta, G., Löffler, A., Wolff, A.: Beyond Outerplanarity. In: Frati, F. und Ma, K.-L. (hrsg.) Proc. 25th Int. Symp. Graph Drawing & Network Vis. (GD'17). S. 546--559. Springer-Verlag (2018).
Kryven, M., Ravsky, A., Wolff, A.: Drawing Graphs on Few Circles and Few Spheres. In: Frati, F. und Ma, K.-L. (hrsg.) Proc. 25th Int. Symp. Graph Drawing & Network Vis. (GD'17). Springer-Verlag (2018).
Kryven, M., Ravsky, A., Wolff, A.: Drawing Graphs on Few Circles and Few Spheres. In: Panda, B.S. und Goswami, P.P. (hrsg.) Proc. 4th Conf. Algorithms & Discrete Appl. Math. (CALDAM'18). S. 164--178. Springer-Verlag (2018).
Wehner, N., Wassermann, S., Casas, P., Seufert, M., Wamser, F.: Beauty is in the Eye of the Smartphone Holder - A Data Driven Analysis of YouTube Mobile QoE, (2018).
Waigand, M.: Towards Traffic Management for Mobile Group-based Communication in WhatsApp, (2017).
Niebling, F.: Spatial Interaction for the Post-Processing of 3D CFD Datasets. In: Kozlikova, B., Schreck, T., und Wischgoll, T. (hrsg.) EuroVis 2017 - Short Papers. The Eurographics Association (2017).
Seufert, M.: Unsupervised QoE Field Study for Mobile YouTube Video Streaming with YoMoApp., 9th International Conference on Quality of Multimedia Experience (QoMEX), Erfurt, Germany (2017).
Beutel, A.: Integration of SDN Performance Monitoring in existing Network Management Software, (2017).
Furth, S., Baumeister, J.: Constructing Technical Knowledge Organizations from Document Structures. In: Frasincar, F., Ittoo, A., Nguyen, L.M., und Métais, E. (hrsg.) Natural Language Processing and Information Systems: 22nd International Conference on Applications of Natural Language to Information Systems, NLDB 2017, Liège, Belgium, June 21-23, 2017, Proceedings. S. 210--213. Springer International Publishing, Cham (2017).
Furth, S., Schirm, M., Belli, V., Baumeister, J.: TEKNO: Preparing Legacy Technical Documents for Semantic Information Systems. In: Frasincar, F., Ittoo, A., Nguyen, L.M., und Métais, E. (hrsg.) Natural Language Processing and Information Systems: 22nd International Conference on Applications of Natural Language to Information Systems, NLDB 2017, Liège, Belgium, June 21-23, 2017, Proceedings. S. 429--434. Springer International Publishing, Cham (2017).
Kamneng Kwam, B.: Performance Evaluation of Placement Algorithms for Service Chains, (2017).
Scherer, K.P., Knöll, D., Baumeister, J., Furth, S.: Knowledge Acquisition by Selflearning Methods with Structured Clinical Data.IJAS: International Conference on Arts and Sciences. , Montreal (2017).
van Dijk, T.C., Fink, M., Fischer, N., Lipp, F., Markfelder, P., Ravsky, A., Suri, S., Wolff, A.: Block Crossings in Storyline Visualizations.Journal of Graph Algorithms & Applications.21,873--913 (2017).
Storyline visualizations help visualize encounters of the characters in a story over time. Each character is represented by an x-monotone curve that goes from left to right visualizing progression of time. A meeting is represented by having the characters that participate in the meeting run close together for some time. In order to keep the visual complexity low, rather than just minimizing pairwise crossings of curves, we propose to count block crossings, that is, pairs of intersecting bundles of lines. In a block crossing, two blocks of parallel lines intersect each other, which is less distracting than the same number of individual crossings being spread over the drawing. In this paper, we show that minimizing the number of block crossings is NP-hard, even if all meetings are of size 2. For this special case, we present a greedy heuristic, which we evaluate experimentally. We show that the general case is fixed-parameter tractable. Our main results is a constant-factor approximation algorithm for meetings of bounded size. The algorithm is based on (approximately) solving a hyperedge deletion problem on hypergraphs that may be of independent interest.
Seufert, M.: Research Activities Report for "Crowdsourcing TF" and "Managing Web & Cloud QoE TF"., 11th Qualinet General Meeting, Erfurt, Germany (2017).
Seufert, M., Lange, S., Meixner, M.: Automated Decision Making based on Pareto Frontiers in the Context of Service Placement in Networks.29th International Teletraffic Congress (ITC). , Genoa, Italy (2017).
Virtualization paradigms like cloud computing, software defined networking (SDN), and network functions virtualization (NFV) provide advantages with respect to aspects like flexibility, costs, and scalability. However, management and orchestration of the resulting networks also introduce new challenges. The placement of services, such as virtual machines~(VMs), virtualized network functions~(VNFs), or SDN controllers, is a multi-objective optimization task that confronts operators with a multitude of possible solutions that are incomparable among each other. The goal of this work is to investigate mechanisms that enable automated decision making between such multi-dimensional solutions. To this end, we investigate techniques from the domain of multi-attribute decision making that aggregate the performance of placements to a single numeric score. A comparison between resulting rankings of placements shows that many techniques produce similar results. Hence, placements that achieve good rankings according to many approaches might be viable candidates in the context of automated decision making. In order to illustrate the functionality of the different scoring mechanisms, we perform a case study on a single network graph and a fixed number of objectives and service instances. Additionally, we present aggregated results from broad evaluations on the Internet Topology Zoo and a larger number of objectives as well as varying numbers of service instances. These allow making more reliable statements about the mechanisms' performance and agreement.
Singer, P., Helic, D., Hotho, A., Strohmaier, M.: A Bayesian Method for Comparing Hypotheses About Human Trails.ACM Trans. Web.11,14:1--14:29 (2017).
When users interact with the Web today, they leave sequential digital trails on a massive scale. Examples of such human trails include Web navigation, sequences of online restaurant reviews, or online music play lists. Understanding the factors that drive the production of these trails can be useful, for example, for improving underlying network structures, predicting user clicks, or enhancing recommendations. In this work, we present a method called HypTrails for comparing a set of hypotheses about human trails on the Web, where hypotheses represent beliefs about transitions between states. Our method utilizes Markov chain models with Bayesian inference. The main idea is to incorporate hypotheses as informative Dirichlet priors and to calculate the evidence of the data under them. For eliciting Dirichlet priors from hypotheses, we present an adaption of the so-called (trial) roulette method, and to compare the relative plausibility of hypotheses, we employ Bayes factors. We demonstrate the general mechanics and applicability of HypTrails by performing experiments with (i) synthetic trails for which we control the mechanisms that have produced them and (ii) empirical trails stemming from different domains including Web site navigation, business reviews, and online music played. Our work expands the repertoire of methods available for studying human trails.
Chaplick, S., Fleszar, K., Lipp, F., Ravsky, A., Verbitsky, O., Wolff, A.: The Complexity of Drawing Graphs on Few Lines and Few Planes. In: Ellen, F., Kolokolova, A., und Sack, J.-R. (hrsg.) Proc. Algorithms Data Struct. Symp. (WADS'17). S. 265--276. Springer-Verlag (2017).
It is well known that any graph admits a crossing-free straight-line drawing in \\($\$\)backslashmathbb R ^3\\($\$\) and that any planar graph admits the same even in \\($\$\)backslashmathbb R ^2\\($\$\) . For a graph G and \\($\$\)d backslashin \backslash\2,3\backslash\\\($\$\) , let \\($\$\)backslashrho ^1\_d(G)\\($\$\) denote the minimum number of lines in \\($\$\)backslashmathbb R ^d\\($\$\) that together can cover all edges of a drawing of G. For \\($\$\)d=2\\($\$\) , G must be planar. We investigate the complexity of computing these parameters and obtain the following hardness and algorithmic results.
Becker, M., Lemmerich, F., Singer, P., Strohmaier, M., Hotho, A.: MixedTrails: Bayesian hypothesis comparison on heterogeneous sequential data.Data Mining and Knowledge Discovery. (2017).
Sequential traces of user data are frequently observed online and offline, e.g., as sequences of visited websites or as sequences of locations captured by GPS. However, understanding factors explaining the production of sequence data is a challenging task, especially since the data generation is often not homogeneous. For example, navigation behavior might change in different phases of browsing a website or movement behavior may vary between groups of users. In this work, we tackle this task and propose MixedTrails , a Bayesian approach for comparing the plausibility of hypotheses regarding the generative processes of heterogeneous sequence data. Each hypothesis is derived from existing literature, theory, or intuition and represents a belief about transition probabilities between a set of states that can vary between groups of observed transitions. For example, when trying to understand human movement in a city and given some data, a hypothesis assuming tourists to be more likely to move towards points of interests than locals can be shown to be more plausible than a hypothesis assuming the opposite. Our approach incorporates such hypotheses as Bayesian priors in a generative mixed transition Markov chain model, and compares their plausibility utilizing Bayes factors. We discuss analytical and approximate inference methods for calculating the marginal likelihoods for Bayes factors, give guidance on interpreting the results, and illustrate our approach with several experiments on synthetic and empirical data from Wikipedia and Flickr. Thus, this work enables a novel kind of analysis for studying sequential data in many application areas.
Loh, F., Burger, V., Wamser, F., Tran-Gia, P., Schembra, G., Rametta, C.: Performance Evaluation of Video Streaming Service Chains in Softwarized 5G Networks with Task Graph Reduction.29th International Teletraffic Congress (ITC) (2017).
Burger, V.: Performance Evaluation and Optimization of Content Delivery Networks, (2017).
Pfaffenberger, F.: Evaluation of Network Monitoring Approaches in Cloud Environments - Experiment and Testbed Design, (2017).
Seufert, M.: Unperturbed Video Streaming QoE Under Web Page Related Context Factors., 9th International Conference on Quality of Multimedia Experience (QoMEX), Erfurt, Germany (2017).
Stulier, N.: Evaluation of Cranial Deformations Using Crowdsourcing, (2017).
Seufert, M.: Concept and Implementation of Video QoE Measurements in a Mobile Broadband Testbed., IEEE/IFIP Workshop on Mobile Network Measurement (MNM’17), Dublin, Ireland (2017).
Seipel, D., Nogatz, F., Abreu, S.: Prolog for Expert Knowledge Using Domain-Specific and Controlled Natural Languages.Proceedings of 8th Language & Technology Conference: Human Language Technologies as a Challenge for Computer Science and Linguistics (LTC). S. 138-140 (2017).
For representing knowledge in intelligent systems in a declarative and natural way, two major approaches have been used in the past: (1) domain–specific languages (DSLs), and (2) controlled natural languages (CNLs). Early DSLs were defined by technical and abstract syntaxes, e.g., for EBNF and regular expressions. More recently, there is a trend in defining DSLs based on natural language, e.g., for the standard relational query language SQL. On the other hand, CNLs stem from computer linguistics, driven by the idea of representing knowledge as a subset of natural languages. Both approaches have proven very useful in many applications. In this paper, we discuss the two approaches for knowledge representation, namely using DSLs and CNLs. Prolog has a long history in both worlds: with the help of user–defined operators, term expansions, and definite clause grammars, it has proven to be very suitable for defining new DSLs with a natural language flavour.
Hirth, M., Jacques, J., Rodgers, P., Scekic, O., Wybrow, M.: Crowdsourcing Technology to Support Academic Research. In: D., A., H., P., und T., H. (hrsg.) Evaluation in the Crowd. Crowdsourcing and Human-Centered Experiments. Springer (2017).
Egger-Lampl, S., Redi, J., Hoßfeld, T., Hirth, M., Möller, S., Naderi, B., Keimel, C., Saupe, D.: Crowdsourcing Quality of Experience Experiments. In: D., A., H., P., und T., H. (hrsg.) Evaluation in the Crowd. Crowdsourcing and Human-Centered Experiments. Springer (2017).
Ring, M., Wunderlich, S., Grüdl, D., Landes, D., Hotho, A.: Creation of Flow-Based Data Sets for Intrusion Detection.Journal of Information Warfare.16,41-54 (2017).
Publicly available labelled data sets are necessary for evaluating anomaly-based Intrusion Detection Systems (IDS). However, existing data sets are often not up-to-date or not yet published because of privacy concerns. This paper identifies requirements for good data sets and proposes an approach for their generation. The key idea is to use a test environment and emulate realistic user behaviour with parameterised scripts on the clients. Comprehensive logging mechanisms provide additional information which may be used for a better understanding of the inner dynamics of an IDS. Finally, the proposed approach is used to generate the flow-based CIDDS-002 data set.
Ring, M., Wunderlich, S., Grüdl, D., Landes, D., Hotho, A.: Flow-based benchmark data sets for intrusion detection.Proceedings of the 16th European Conference on Cyber Warfare and Security. S. 361--369 (2017).
Lemmerich, F., Singer, P., Becker, M., Espin-Noboa, L., Dimitrov, D., Helic, D., Hotho, A., Strohmaier, M.: Comparing Hypotheses About Sequential Data: A Bayesian Approach and Its Applications. In: Altun, Y., Das, K., Mielikäinen, T., Malerba, D., Stefanowski, J., Read, J., vZitnik, M., Ceci, M., und Dvzeroski, S. (hrsg.) Machine Learning and Knowledge Discovery in Databases. S. 354--357. Springer International Publishing, Cham (2017).
Sequential data can be found in many settings, e.g., as sequences of visited websites or as location sequences of travellers. To improve the understanding of the underlying mechanisms that generate such sequences, the HypTrails approach provides for a novel data analysis method. Based on first-order Markov chain models and Bayesian hypothesis testing, it allows for comparing a set of hypotheses, i.e., beliefs about transitions between states, with respect to their plausibility considering observed data. HypTrails has been successfully employed to study phenomena in the online and the offline world. In this talk, we want to give an introduction to HypTrails and showcase selected real-world applications on urban mobility and reading behavior on Wikipedia.
Ring, M., Landes, D., Dallmann, A., Hotho, A.: IP2Vec: Learning Similarities Between IP Addresses.2017 IEEE International Conference on Data Mining Workshops (ICDMW).657-666 (2017).
Barbic, J., Du0027Cruz, M., Latoschik, M.E., Slater, M., Bourdot, P. hrsg: Virtual Reality and Augmented Reality, Proceedings of the 14th EuroVR International Conference, EuroVR 2017.Springer (2017).
This book constitutes the refereed proceedings of the 14th International Conference on Virtual Reality and Augmented Reality, EuroVR 2017, held in Laval, France, in December 2017. The 10 full papers and 2 short papers presented were carefully reviewed and selected from 36 submissions. The papers are organized in four topical sections: interaction models and user studies, visual and haptic real-time rendering, perception and cognition, and rehabilitation and safety.
Tüchert, A.: Influence of loading delays on the perceived quality of web-based enterprise portals, (2017).
Oberdörfer, S., Heidrich, D., Latoschik, M.E.: Interactive Gamified Virtual Reality Training of Affine Transformation. In: Ullrich, C. und Wessner, M. (hrsg.) Proceedings of DeLFI and GMW Workshops 2017 (2017).
Seipel, D., Hanus, M., Abreu, S. hrsg: Declare 2017 – Conference on Declarative Programming.Institut für Informatik (2017).
This technical report contains the papers presented at the Conference on Declarative Programming Declare 2017, in Würzburg, Germany, from September 19th to 22th, 2017. The joint conference consisted of the 21st International Conference on Applications of Declarative Programming and Knowledge Management INAP 2017, the 31st Workshop on Logic Programming WLP 2017, and the 25th Workshop on Functional and (Constraint) Logic Programming WFLP 2017. Declarative programming is an advanced paradigm for modeling and solving complex problems. This method has attracted increased attention over the last decades, e.g., in the domains of data and knowledge engineering, databases, artificial intelligence, natural language processing, modeling and processing combinatorial problems, and for establishing knowledge-based systems for the web. The conference Declare 2017 aims to promote the cross-fertilizing exchange of ideas and experiences among researches and students from the different communities interested in the foundations, applications, and combinations of high-level, declarative programming and related areas. It was be accompanied by a one-week summer school on Advanced Concepts for Databases and Logic Programming for students and PhD students.
Lugrin, B., Frommel, J., André, E.: Combining a Data-driven and a Theory-based Approach to Generate Culture-dependent Behaviours for Virtual Characters. In: Faucher, C. (hrsg.) Advances in Culturally-Aware Intelligent Systems and in Cross-Cultural Psychological Studies. Springer (2017).
Smietanka, O.: Detecting People Flows with Distributed Loudness Sensors, (2017).
Lange, S., Grigorjew, A., Zinner, T., Tran-Gia, P., Jarschel, M.: A Multi-Objective Heuristic for the Optimization of Virtual Network Function Chain Placement.29th International Teletraffic Congress (ITC) (2017).
Bauer, A.: Impact of Game Mods on Game Sales and Player Behavior, (2017).
Bente, G., Roth, D., Al-Issa, A.: Beyond Stereotypes: Using VR-based Methods in Nonverbal Communication Research. (2017).
The contribution aims to demonstrate the value of computational methods from Virtual Reality (VR) for the study of nonverbal communication and person perception. Focusing on gender and cultural differences in “nonverbal rapport” we will show how motion capture technology and character animation can help overcome stereotype influence and judgment biases in observation studies and at the same time provide deeper insights into the behavioral dynamics of nonverbal communication. Specific algorithms and software tools for continuous impression ratings, parameter extraction from dyadic movement protocols and integrated analysis of impressions and behavioral data will be introduced. Future prospects for other areas of nonverbal communication research will be outlined.
Borchert, K., Hirth, M., Schnitzer, S., Rensing, C.: Impact of Task Recommendation Systems in Crowdsourcing Platforms.Workshop on Responsible Recommendation at RecSys 2017. , Como, Italy (2017).
Tschammler, F.: Relationship between Context and QoE for Video Streaming, (2017).
Rosenberger, A.: Evaluation of the Stability of BGP Routes Based on RTT Measurements, (2017).
Flaig, N.: Simulative Performance Comparison of Adaptation Logics for HTTP Adaptive Streaming, (2017).
Schaper, P., Grundgeiger, T.: Commission errors in delay-execute prospective memory tasks.Quarterly Journal of Experimental Psychology.70,1423--1438 (2017).
Stauffert, J.-P., Niebling, F., Latoschik, M.E.: A Latency and Latency Jitter Simulation Framework with OSVR.10th Workshop on Software Engineering and Architectures for Realtime Interactive Systems (SEARIS), IEEE Computer Society, (2017) (2017).
Latency is a pressing problem in Virtual Reality (VR) applications. Low latencies are required for VR to reduce perceptual artifacts and cyber sickness. Latency jitter, i.e. variance in the pattern of latency, prevent coping mechanisms as users canu0027t adapt. Low latency is a fundamental timeliness requirement to reduce the potential risks of cyber sickness and to increase effectiveness, efficiency, and user experience of Virtual Reality Systems. The effects of uniform latency degradation based on mean or worst-case values are well researched. In contrast, the effects of latency jitter, the distribution pattern of latency changes over time has largely been ignored so far, although todayu0027s consumer VR systems are extremely vulnerable in this respect. In this paper, we propose to create a model of latency and latency jitter with empirical distributions as well as a method of using those models to inject latency. The process of creating a latency model is demonstrated with an example of gathering and converting latency samples from an example application. We show how to simulate latency and motivate to use it in middleware to allow for less intrusive latency effect evaluations.
Schaper, P., Grundgeiger, T.: The effect of different distractions on remembering delayed intentions.Memory.26,154-170 (2017).
Loreto, V., Haklay, M., Hotho, A., Servedio, V.C.P., Stumme, G., Theunis, J., Tria, F. hrsg: Participatory sensing, opinions and collective awareness.Springer (2017).
Hoßfeld, T., Fiedler, M., Gustafsson, J.: Betas: Deriving Quantiles from MOS-QoS Relations of IQX Models for QoE Management.IFIP/IEEE International Workshop on Quality of Experience Management (QoE-Management). , Lisbon, Portugal (2017).
Seufert, M., Moldovan, C., Burger, V., Hoßfeld, T.: Applicability and Limitations of a Simple WiFi Hotspot Model for Cities.13th International Conference on Network and Service Management (CNSM). , Tokio, Japan (2017).
Offloading mobile Internet data via WiFi has emerged as an omnipresent trend. WiFi networks are already widely deployed by many private and public institutions (e.g., libraries, cafes, restaurants) but also by commercial services to provide alternative Internet access for their customers and to mitigate the load on mobile networks. Moreover, smart cities start to install WiFi infrastructure for current and future civic services, e.g., based on sensor networks or the Internet of Things. A simple model for the distribution of WiFi hotspots in an urban environment is presented. The hotspot locations are modeled with a uniform distribution of the angle and an exponential distribution of the distance, which is truncated to the city limits. We compare the characteristics of this model in detail to the real distributions. Moreover, we show the applicability and the limitations of this model, and the results suggest that the model can be used in scenarios, which do not require an accurate spatial collocation of the hotspots, such as offloading potential, coverage, or signal strength.
Martin, D., Carpendale, S., Gupta, N., Hoßfeld, T., Naderi, B., Redi, J., Siahaan, E., Wechsung, I.: Understanding The Crowd: Ethical and Practical Matters in the Academic Use of Crowdsourcing. In: Archambault, D., Hoßfeld, T., und Purchase, H.C. (hrsg.) Evaluation in the Crowd: Crowdsourcing and Human-Centred Experiments. Springer (2017).
Sträßer, M.: SDN-based Elephant Detection, (2017).
ZOOM is an SDN based approach for elephant detection in SDN enabled networks. The idea is to split the IP address space into sections that are iteratively refined until only the largest flows remain. These are then returned as elephant flows. A proof-of-concept implementation and basic evaluation has already been performed in the paper emphZOOM: Lightweight SDN-based Elephant Detection.
Schwind, A.: Concept and Implementation of QoE Measurements in a Mobile Broadband Testbed, (2017).
Meixner, M.: Methods for Assessment of Multi-objective Optimization Algorithms with Application in the Context of SDN, (2017).
Hoßfeld, T., Heegaard, P.E., Skorin-Kapov, L., Varela, M.: No Silver Bullet: QoE Metrics, QoE Fairness, and User Diversity in the Context of QoE Management.9th International Conference on Quality of Multimedia Experience (QoMEX 2017). , Erfurt, Germany (2017).
Lareida, A., Hoßfeld, T., Stiller, B.: The BitTorrent Peer Collector Problem.IFIP/IEEE International Symposium on Integrated Network Management. , Lisbon, Portugal (2017).
Popp, C.: Study on the Accuracy of Video Monitoring VNF in High Mobility Environments, (2017).
Fischbach, M., Wiebusch, D., Latoschik, M.E.: Semantic Entity-Component State Management Techniques to Enhance Software Quality for Multimodal VR-Systems.IEEE Transactions on Visualization and Computer Graphics (TVCG).23,1342-1351 (2017).
Modularity, modifiability, reusability, and API usability are important qualities that determine the maintainability of complex software architectures typical for Virtual, Augmented, and Mixed Reality (VR, AR, MR) applications. These architectures address various input-, output-, and processing aspects, which are usually implemented by dedicated software modules. Collectively, these modules have to maintain the real-time simulation of a coherent application state. This requirement, however, implicates multiple semantic as well as temporal state representation- and access interdependencies between modules, exacerbating maintainable solutions. This paper presents five semantics-based software techniques for state management that extend the well-established entity-component system (ECS) pattern, foster modularity and enhance overall maintainability. A walk-through of typical implementation aspects of multimodal (speech and gesture) interfaces is used to highlight the techniquesu0027 benefits, providing a typical example for demanding software architectures in VR, AR and MR. Finally, central implementation details are compared against prominent alternatives.
Peng, D., Wolff, A., Haunert, J.-H.: Using the A\($^\star$\) Algorithm to Find Optimal Sequences for Area Aggregation. In: Peterson, M.P. (hrsg.) Proc. 28th Int. Cartogr. Conf. (ICC'17) -- Advances in Cartogr. & GIScience. S. 389--404. Springer-Verlag (2017).
Haunert, J.-H., Wolff, A.: Beyond Maximum Independent Set: An Extended Integer Programming Formulation for Point Labeling.International Journal of Geo-Information.6,article 342, 20 pages (2017).
Map labeling is a classical problem of cartography that has frequently been approached by combinatorial optimization. Given a set of features in a map and for each feature a set of label candidates, a common problem is to select an independent set of labels (that is, a labeling without label--label intersections) that contains as many labels as possible and at most one label for each feature. To obtain solutions of high cartographic quality, the labels can be weighted and one can maximize the total weight (rather than the number) of the selected labels. We argue, however, that when maximizing the weight of the labeling, the influences of labels on other labels are insufficiently addressed. Furthermore, in a maximum-weight labeling, the labels tend to be densely packed and thus the map background can be occluded too much. We propose extensions of an existing model to overcome these limitations. Since even without our extensions the problem is NP-hard, we cannot hope for an efficient exact algorithm for the problem. Therefore, we present a formalization of our model as an integer linear program (ILP). This allows us to compute optimal solutions in reasonable time, which we demonstrate both for randomly generated point sets and an existing data set of cities. Moreover, a relaxation of our ILP allows for a simple and efficient heuristic, which yielded near-optimal solutions for our instances.
Horst-Schaper, G., Kumar, D.S., Schaper, P.: [POSTER] Patientenübergriffe - ein Thema für Betriebsärzte im Krankenhaus?!.57th Wissenschaftliche Jahrestagung der Deutschen Gesellschaft für Arbeitsmedizin und Umweltmedizin e.V. (2017).
Seufert, M.: Performance Evaluation of Mobile Crowdsensing., ITG FA 5.2 Workshop on Smart Cities, Lübeck, Germany (2017).
This talk intends to give an overview on Quality of Experience (QoE) monitoring for mobile video streaming, which is an important part of the QoE traffic management cycle. First, the talk recaps the concept of Quality of Experience of HTTP Adaptive Streaming (HAS), which is the current state-of-the-art video streaming technology. Afterwards, different approaches to QoE monitoring are introduced and discussed. Thereby, the talk provides details how the impact of QoE factors, in particular, the quality adaptation of HAS, can be assessed with crowdsourced subjective studies. Moreover, an example is given how to monitor network- and application-layer QoE factors and subjective feedback of end users with a smartphone video streaming app. Finally, the talk wants to stimulate discussions on open research questions of HAS and beyond.
Iffländer, L., Wamser, F., Metter, C., Tran-Gia, P., Kounev, S.: Performance Assessment of Cloud Migrations from Network and Application Point of View.Proceedings of 9th EAI International Conference on Mobile Networks and Management (MONAMI 2017). , Melbourne, Australia (2017).
Seufert, M.: EdgeNetworkCloudSim: Placement of Service Chains in Edge Clouds Using NetworkCloudSim., 1st IEEE International Workshop on Network Programmability - From the Data Center to the Ground (NetFoG), Bologna, Italy (2017).
Kamneng Kwam, B.: Static Placement of Services on Edge Servers, (2017).
Abd El Hai, S.: Measuring the Applicability of the Analytic Model for SDN Controller Traffic and Switch Table Occupancy, (2017).
In the paper 'Analytic Model for SDN Controller Traffic and Switch Table Occupancy' a model has been created and later been verified by simulation. The next step is to test the applicability of the model by measurements. The task is to create a testbed and methods to accomplish this. <christopher.metter@informatik.uni-wuerzburg.de>
Zinner, T., Geissler, S., Helmschrott, F., Spinsante, S., Braeken, A.: An AAL-Oriented Measurement-based Evaluation of Different HTTP-based Data Transport Protocols.International Workshop on Protocols, Applications and Platforms for Enhanced Living Environments (2017).
A key requirement for Active and Assisted Living (AAL) environments is the exchange of data between different communication endpoints to support wide range of services and applications. Used communication protocols need to support the bidirectional flow of information and have to be optimized with regard to security or latency constraints. To address these issues, RESTful approaches have recently gained much attention from the community. In this context, different application layer transport protocols can be used to realize the required data exchange. Besides HTTP/1.1, developed and standardized in the 1990s, new protocols like HTTP/2 and the QUIC transfer protocol my be suitable candidates. The impact of the different protocols on the overall performance for web and AAL services is still an open research question. This paper narrows this gap by conducting a measurement-based comparison of the three described protocols with regard to their performance in terms of web page loading times for Google web services.
Nguyen-Ngoc, A., Lange, S., Zinner, T., Seufert, M., Tran-Gia, P., Aerts, N., Hock, D.: Performance Evaluation of Selective Flow Monitoring in the ONOS Controller.4th International Workshop on Management of SDN and NFV Systems (ManSDN/NFV). , Tokio, Japan (2017).
One of the benefits when network operators adopt the Software Defined Networking (SDN) paradigm is the ability to monitor the traffic in the network without an additional network management system. Usually, SDN controllers utilize OpenFlow statistics messages in order to regularly gather information about all flows in the network. However, using the same polling interval for all flows does not take into account the heterogeneity of real world traffic and thus results in an imbalance between monitoring accuracy and control plane overhead. In particular, frequent querying results in a high resource consumption at the controller. This work proposes a Selective Flow Monitoring (SFM) mechanism that allows administrators to classify flows according to their individual requirements in terms of monitoring frequency, e.g., less frequent polling of elephant flows and frequent polling of QoS sensitive VoIP connections. We compare the performance of the SFM mechanism with the default monitoring scheme in a testbed featuring the Open Network Operating System (ONOS) controller. In this context, the CPU utilization of the controller is used as performance indicator. After identifying relevant influence factors like the number of flows and switches in the network, we investigate the viability of the approaches in different scenarios. Finally, we provide guidelines regarding their choice.
Surminski, S., Moldovan, C., Hoßfeld, T.: Saving Bandwidth by Limiting the Buffer Size in HTTP Adaptive Streaming.MMBnet 2017 Proceedings of the 9th GI/ITG Workshop. , Hamburg, Germany (2017).
Video streaming is one of the most bandwidth-intensive applications on the Internet. In HTTP adaptive video streaming the video quality is selected according to the available bandwidth. To compensate bandwidth fluctuations, players use a buffer in order to ensure a smooth video output. On one hand, if the buffer runs empty, the video playback stops, which users experience as negative. On the other hand, if the user aborts video playback, the video in the buffer was unnecessarily transmitted, hence this bandwidth was wasted. In this paper, we present a study in which we investigate the behavior of two video players and different buffer configurations in real-world bandwidth scenarios. Thereby, we focus on the dimensioning of the buffer size and the tradeoff between wasted bandwidth and the playback quality
Pfaff, B., Scherer, J., Hock, D., Gray, N., Zinner, T., Tran-Gia, P., Durner, R., Kellerer, W., Lorenz, C.: SDN/NFV-enabled Security Architecture for Fine-grained Policy Enforcement and Threat Mitigation for Enterprise Networks, (2017).
Network Functions Visualization (NFV) replaces physical middleboxes with software instances running network functions in cloud environments. To support this new paradigm, it is necessary to port the code basis from highly specialized hardware devices to virtual machines running on COTS hardware. In order to fully exploit the inherent capabilities of cloud environments it is further necessary to redesign the software to support a large amount of distributed, cooperating function instances instead of single, isolated and monolithic instances. This development can be observed for network functions like stateful firewalling. Until now, available software firewalls lack support for active/active operation in clustered environments, which hinders horizontal scalability. This is due to the fact that the required synchronization of connection states among the cluster's instances is an impediment that still has to be resolved. Therefore, this work investigates different synchronization strategies and mechanisms, which allow to share connection states among the cluster to maintain scalability and high-availability.
Schaper, P., Grundgeiger, T.: I should have stopped – Investigating the role of response suppression in commission errors.Beiträge zur 59.Tagung experimentell arbeitender Psychologen (2017).
Bekos, M.A., van Dijk, T.C., Fink, M., Kindermann, P., Kobourov, S., Pupyrev, S., Spoerhase, J., Wolff, A.: Improved Approximation Algorithms for Box Contact Representations.Algorithmica.77,902--920 (2017).
We study the following geometric representation problem: Given a graph whose vertices correspond to axis-aligned rectangles with fixed dimensions, arrange the rectangles without overlaps in the plane such that two rectangles touch if the graph contains an edge between them. This problem is called Contact Representation of Word Networks (Crown) since it formalizes the geometric problem behind drawing word clouds in which semantically related words are close to each other. Crown is known to be NP-hard, and there are approximation algorithms for certain graph classes for the optimization version, Max-Crown, in which realizing each desired adjacency yields a certain profit. We present the first \($O(1)$\)-approximation algorithm for the general case, when the input is a complete weighted graph, and for the bipartite case. Since the subgraph of realized adjacencies is necessarily planar, we also consider several planar graph classes (namely stars, trees, outerplanar, and planar graphs), improving upon the known results. For some graph classes, we also describe improvements in the unweighted case, where each adjacency yields the same profit. Finally, we show that the problem is APX-complete on bipartite graphs of bounded maximum degree.
Burger, V., Seufert, M., Zinner, T., Tran-Gia, P.: An Approximation of the Backhaul Bandwidth Aggregation Potential Using a Partial Sharing Scheme.15th IFIP/IEEE International Symposium on Integrated Network Management (IM). , Lisbon, Portugal (2017).
To cope with the increasing demands of mobile devices and the limited capacity of cellular networks, mobile connections are offloaded to WiFi. The access capacity is further increased by aggregating backhaul bandwidth of WiFi access links. To analyze the performance of aggregated access links we develop a model for two and more cooperating systems sharing capacities using an offloading scheme. The state probabilities of the different cooperating systems in the analytic model are determined by a fixed point iterative procedure. By investigating an inner and outer composite system we are able to analyze the system in imbalanced load conditions where the system reaches its full potential utilizing spare bandwidth. To evaluate the robustness of the system against users that try to exploit the system, the bandwidth received by prioritized users is quantified.
Roth, D., Latoschik, M.E., Bente, G.: Hello from the Other Side Behavioral Realism and Social Augmentation in Shared Virtual Environments.Presentation at the 3rd Virtual Social Interaction Workshop, Bielefeld University, Bielefeld (2017).
Lammers, S., Geiger, A., Roth, D., Sevdalis, V., Bente, G., Vogeley, K.: Understanding "What" or Understanding "How": Mirroring or Mentalizing Other Personu0027s Actions. A New Approach to Neuroimaging of the Social Brain.Poster presented at the 2. Scientific Symposium of the B.Sc./M.Sc. Neuroscience, University of Cologne, Germany (2017).
The mirror neuron system (MNS) and the mentalizing system (MENT) are both important in social interaction [1]. Previous studies in the field of social cognitive neuroscience mainly investigated MNS and MENT separately [2]. The stimuli used in these studies were always substantially different (videos of human motion for MNS vs. verbal or written stories for MENT). To provide the systematic study of both systems we designed video-stimuli, which (together with two specific forced-choice questions) differentially activate both systems. The usage of virtual characters for the investigation of nonverbal behavior has been proven to be eco- logically valid [3]. Our design will allow to discriminate more precisely between the two systems and help get a better understanding of the underlying neural basis. Furthermore it may provide new insights into the neurobiology of psychopathological conditions including autism spectrum disorder (ASD).
Moldovan, C., Hagn, K., Sieber, C., Kellerer, W., Hoßfeld, T.: Keep Calm and Don’t Switch: About the Relationship Between Switches and Quality in HAS.29th International Teletraffic Congress (ITC 29). S. 6. , Genoa, Italy (2017).
Video streaming has established itself as the main method to consume multimedia content on the Internet. The most widespread technique is HTTP Adaptive Streaming which is used by large video service platforms such as YouTube and Netflix. In order to guarantee a high QoE, different adaptation strategies have been developed that lead to different video playout patterns. While some strategies may be more aggressive than others and often adapt the video quality, it is not clear which strategy is the best. In this paper, we want to identify the trade-off between the av- erage video quality and switches in the quality during playout. We do this with a user-centric view and try to optimize the adaptation depending on the user preference with a quadratic program. This work allows us to put existing and future video adaptation algorithms in perspective with respect to user preferences. Our results show that the video quality can already be increased greatly by allowing few switches while more switches lead to diminishing gains. This is a novel discovery that is important for user-centric QoE-management which is of high interest for ISPs and video service providers.
Wiebusch, D., Zimmerer, C., Latoschik, M.E.: Cherry-Picking RIS Functionality -- Integration of Game and VR Engine Sub-Systems based on Entities and Events.10th Workshop on Software Engineering and Architectures for Realtime Interactive Systems (SEARIS). IEEE Computer Society (2017).
Modern game engines provide a variety of high-end features and sub-systems which have made them increasingly interesting for AR/VR research. Here, it often is necessary to combine features from different sources. This paper presents an approach based on entity-event state decoupling and exchange. The approach targets the combination of sub-systems from different sources which simulate functionally coherent aspects of the virtual objects like physics, graphics, AI, or developer services like state editing. The approach decouples specific internal representations using a semantic description layer for identifiers, data types, and potential relations between them. We illustrate the main concepts using examples from the combination of the Unreal Engine 4, the Unity engine, and own research software and illustrate performance related aspects as a guideline for the choice of an appropriate transport layer.
Schaper, P., Grundgeiger, T.: The role of cognitive load and suppression in commission errors.Conference of the European Society for Cognitive Psychology (2017).
Dallmann, A., Grimm, A., Pölitz, C., Zoller, D., Hotho, A.: Improving Session Recommendation with Recurrent Neural Networks by Exploiting Dwell Time, http://arxiv.org/abs/1706.10231, (2017).
Recently, Recurrent Neural Networks (RNNs) have been applied to the task of session-based recommendation. These approaches use RNNs to predict the next item in a user session based on the previ- ously visited items. While some approaches consider additional item properties, we argue that item dwell time can be used as an implicit measure of user interest to improve session-based item recommen- dations. We propose an extension to existing RNN approaches that captures user dwell time in addition to the visited items and show that recommendation performance can be improved. Additionally, we investigate the usefulness of a single validation split for model selection in the case of minor improvements and find that in our case the best model is not selected and a fold-like study with different validation sets is necessary to ensure the selection of the best model.
Ring, M., Wunderlich, S., Grüdl, D., Landes, D., Hotho, A.: A Toolset for Intrusion and Insider Threat Detection. In: Palomares Carrascosa, I., Kalutarage, H.K., und Huang, Y. (hrsg.) Data Analytics and Decision Support for Cybersecurity: Trends, Methodologies and Applications. S. 3--31. Springer International Publishing, Cham (2017).
Company data are a valuable asset and must be protected against unauthorized access and manipulation. In this contribution, we report on our ongoing work that aims to support IT security experts with identifying novel or obfuscated attacks in company networks, irrespective of their origin inside or outside the company network. A new toolset for anomaly based network intrusion detection is proposed. This toolset uses flow-based data which can be easily retrieved by central network components. We study the challenges of analysing flow-based data streams using data mining algorithms and build an appropriate approach step by step. In contrast to previous work, we collect flow-based data for each host over a certain time window, include the knowledge of domain experts and analyse the data from three different views. We argue that incorporating expert knowledge and previous flows allow us to create more meaningful attributes for subsequent analysis methods. This way, we try to detect novel attacks while simultaneously limiting the number of false positives.
Zach, O., Seufert, M., Hirth, M., Slanina, M., Tran-Gia, P.: On Use of Crowdsourcing for H.264/AVC and H.265/HEVC Video Quality Evaluation.Radioelektronika. , Brno, Czech Republic (2017).
Crowdsourcing has become a popular method in the field of video quality evaluation. Gathering the opinion of the users using crowdsourcing is quick and relatively cheap but such a study has to be designed very carefully in order to give relevant results. So far, the majority of the QoE studies using crowdsourcing has been focusing on the performance of H.264/AVC algorithm in different situations (such as encoder settings, stalling effects, etc). Modern video coding methods, however, are only rarely tested using the crowdsourcing approach. We designed a study comparing the performance of both H.264/AVC and H.265/HEVC standards in the crowdsourcing environment. We deal with the possibilities of delivering and presenting the HEVC encoded content to the participants of the crowdsourcing study and potential challenges. Finally, the study was performed using Microworkers platform and gathered results are then compared with three different objective video quality metrics.
Roth, D., Lugrin, J.-L., von Mammen, S., Latoschik, M.E.: Controllers & Inputs: Masters of Puppets. In: Banks, J. (hrsg.) Digital Formations. S. 281-290. Peter Lang (2017).
Avatar, Assembled is a curated volume that unpacks videogame and virtual world avatars—not as a monolithic phenomenon (as they are usually framed) but as sociotechnical assemblages, pieced together from social (human-like) features like voice and gesture to technical (machine-like) features like graphics and glitches. Each chapter accounts for the empirical, theoretical, technical, and popular understandings of these avatar “compo- nents”—60 in total—altogether offering a nuanced explication of avatars-as-assemblages as they matter in contemporary soci- ety and in individual experience. The volume is a “crossover” piece in that, while it delves into complex ideas, it is written in a way that will be accessible and interesting to students, researchers, designers, and practitioners alike.
Striepe, H., Lugrin, B.: There Once Was a Robot Storyteller: Measuring the Effects of Emotion and Non-verbal Behaviour.9th Int. Conf. on Social Robotics (ICSR 2017). Springer International Publishing (2017).
Social Robots bear great potential to tell stories to human listeners. Through their embodiment and ability to display non-verbal and emotional behaviour, additional modalities can be used to transport the user into the story compared to traditional media such as books or audio books. Based on theoretical knowledge about the design of social robot storytellers and the analysis of human storytellers, we designed the behaviour of an emotional social robot storyteller and compared it to a neutral version of the robotic storyteller and the voice of a human story- teller represented by an audio book. Results suggest that the emotional robot is able to transport the participants equally well as the traditional audio book, while the neutral robot performed worse. We therefore claim, that emotional behaviour in the domain of robotic storytelling should be carefully designed to support the story rather then preventing a good transportation.
Schwind, A., Seufert, M., Alay, Ö., Casas, P., Tran-Gia, P., Wamser, F.: Concept and Implementation of Video QoE Measurements in a Mobile Broadband Testbed.IEEE/IFIP Workshop on Mobile Network Measurement (MNM’17). , Dublin, Ireland (2017).
The MONROE testbed enables the objective performance assessment of MBB networks from the end-user perspective, using highly distributed measurements from fixed and mobile nodes. To quantify the performance of MBB networks for popular Internet services from a user-centric perspective, dedicated tools are needed. In this paper we extend the MONROE testbed to the Quality of Experience (QoE) domain, presenting the design and implementation of a QoE-capable measurement tool for YouTube video streaming. The measurement concept is based on emulating a virtual end-user device requesting video streams, which are then monitored at the network and application layers, on the basis of QoE-relevant features. The initial measurements conducted in the MONROE testbed and reported in this paper demonstrate the applicability of the implemented measurement concept.
Shweiki, R.: Determination of Traffic Patterns by a Remote Controllable Drone, (2017).
Durch die steigende Anzahl an Endgeräten im Netzwerk und den damit verbundenen Anstieg an Datenverkehr ist es für den Provider wichtig, die erzeugte Menge an Datenverkehr genau zu kennen. Dies stellt sich durch viele neue Geräte mit neuen Verkehrsmustern jedoch als schwierig heraus, weshalb detaillierte Verkehrsmodelle für jedes Gerät erstellt werden müssen. Auf der anderen Seite profitiert auch der Nutzer von der genauen Verkehrsanalyse. Störungen in von ihm genutzen Services werden schneller erkannt und behoben. In der hier vorgestellten Arbeit soll diese Verkehrsanalyse anhand einer vom Nutzer ferngesteuerten Drohne durchgeführt werden: Ziel der Arbeit ist es mit Hilfe einer am Lehrstuhl vorhandenen Drohne Datenverkehrsmessungen durchzuführen und zu evaluieren. Es soll herausgefunden werden, wie sich die Distanz zum Nutzer oder Hindernisse zwischen dem Nutzer und der Drohne auf den Datendurchsatz beispielsweise bei einer WiFi oder Bluetooth Verbindung auswirkt. Abschließend sollen die gewonnenen Ergebnisse mit Hilfe von vorhandenen Verkehrsmustern verglichen werden und Gemeinsamkeiten sowie Unterschiede herausgefunden und analysiert werden.
Schwarzmann, S., Zinner, T., Dobrijevic, O.: Quantitative Comparison of Application-Network Interaction: A Case Study of Adaptive Video Streaming.Springer Quality and User Experience. (2017).
Managing quality of experience (QoE) is now widely accepted as a critical objective for multimedia applications and the supporting communication systems. In general, QoE management encompasses: (i) monitoring of the key influence factors and QoE indicators, and (ii) deciding on the appropriate control actions as specified by the management goal. Many multimedia applications, e.g. video streaming and audio conferencing, are able to adjust their operational parameters so as to react to variations in the network performance. However, such an adaptation feature is mostly based on a local client view of the network conditions, which may lead to an unfair allocation of network resources among heterogeneous clients and, thus, an unfair QoE distribution. In order to tackle this issue, there is the call for a cooperation between the applications and the underlying network, which includes application-network interaction (App-Net) in terms of: (1) exchanging information on the monitored QoE indicators, and (2) coordinating the QoE control actions. Various App-Net mechanisms focusing on specific use cases and applications have been proposed to date. This paper gives an overview of App-Net mechanisms and proposes a generic App-Net model that provides the means to realize a coordinated QoE-centric management. Based on the App-Net model, we develop an evaluation methodology to compare three App-Net mechanisms for managing QoE of HTTP adaptive streaming (HAS) against a baseline HAS service. The aim of this quantitative comparison is to explore the trade-offs between QoE gains and the complexity of App-Net implementation, with respect to the number of monitoring and control messages, achieved video quality, and QoE fairness among heterogeneous clients. Our ultimate goal is to set up reproducible experiments that facilitate a holistic evaluation of different App-Net mechanisms.
Gray, N., Zinner, T., Tran-Gia, P.: Enhancing SDN Security by Device Fingerprinting, (2017).
Software-defined Networking (SDN) provides an increased flexibility and cost savings by separating the data from the control plane. Despite these benefits, this separation also results in a greater attack surface as new devices and protocols are deployed. OpenFlow is one of these protocols and enables the communication between the switch and the controller. Ideally this connection takes place over an encrypted TLS channel, but as this feature is marked optional, it is not supported by all devices. This allows an attacker to eavesdrop and alter the communication, hence resulting in a comprised network. In this work, we demonstrate a new approach for authentication based on device fingerprinting to enhance the security in scenarios, where cryptographic mechanisms are unavailable.
Zinner, T.: QoE-Aware Service And Network Management for Video Streaming., NewNet@Paris Lab, Telecom ParisTech, France (http://perso.telecom-paristech.fr/~drossi/index.php?n=Main.Seminar#KEY20170920) (2017).
Wehner, N.: Unsupervised QoE Field Study for Mobile YouTube Video Streaming with YoMoApp, (2017).
Borchert, K., Hirth, M., Zinner, T., Göritz, A.: Collecting Subjective Ratings in Enterprise Environments.9th International Conference on Quality of Multimedia Experience (QoMEX). , Erfurt, Germany (2017).
Roth, D., Waldow, K., Latoschik, M.E., Fuhrmann, A., Bente, G.: Socially Immersive Avatar-Based Communication.Proceedings of the 24th IEEE Virtual Reality (VR) Conference, Los Angeles, CA, 2017. S. 259-260 (2017).
In this paper, we present SIAM-C, an avatar-mediated communication platform to study socially immersive interaction in virtual environments. The proposed system is capable of tracking, transmitting, representing body motion, facial expressions, and voice via virtual avatars and inherits the transmission of human behaviors that are available in real-life social interactions. Users are immersed using active stereoscopic rendering projected onto a life-size projection plane, utilizing the concept of “fish tank” virtual reality (VR). Our prototype connects two separate rooms and allows for socially immersive avatar-mediated communication in VR.
Knapp, T.: Extending the Monitoring Features of ONOS, (2017).
The SDN controller ONOS lacks certain network monitoring capabilities. The task is to develop an ONOS application which utilizes the interfaces provided by ONOS and enableds the active measurement of a predefined set of network metrics.
Bott, L.: Implementing Backup Paths and Recovery Strategies in an SDN controlled by ONOS, (2017).
As the migration towards SDN is in progress, the satisfaction of carrier-grade requirements (fast failure detection, fast reaction, high availability throughout the year) becomes more and more important. The SDN controller ONOS already provides promising mechanisms and tools, but lacks certain capabilities. The task of the project is to enhance ONOS capabilities by implementing the provisioning of backup paths and recovery strategies. <christopher.metter@informatik.uni-wuerzburg.de>
Hoffmann, M., Jarschel, M., Pries, R., Schneider, P., Jukan, A., Bziuk, W., Gebert, S., Zinner, T., Tran-Gia, P.: SDN and NFV as Enabler for the Distributed Network Cloud.Mobile Networks and Applications. (2017).
Chaplick, S., Fleszar, K., Lipp, F., Ravsky, A., Verbitsky, O., Wolff, A.: The Complexity of Drawing Graphs on Few Lines and Few Planes. In: Ellen, F., Kolokolova, A., und Sack, J.-R. (hrsg.) Proc. Algorithms Data Struct. Symp. (WADS'17). S. 265--276. Springer-Verlag (2017).
Pfaff, B.: Evaluation of a Distributed Control Plane for Managing Heterogeneous SDN and Legacy Networks, (2017).
Sommer, M.: Implementation of an OpenFlow Fuzzing Framework, (2017).
Bruckdorfer, T., Cornelsen, S., Gutwenger, C., Kaufmann, M., Montecchiani, F., Nöllenburg, M., Wolff, A.: Progress on Partial Edge Drawings.Journal of Graph Algorithms & Applications.21,757--786 (2017).
Recently, a new way of avoiding crossings in straight-line drawings of non-planar graphs has been introduced. The idea of partial edge drawings (PED) is to drop the middle part of edges and rely on the remaining edge parts called stubs. We focus on symmetric partial edge drawings (SPEDs) that require the two stubs of an edge to be of equal length. In this way, the stub at the other endpoint of an edge assures the viewer of the edge's existence. We also consider an additional homogeneity constraint that forces the stub lengths to be a given fraction �� of the edge lengths (��-SHPED). Given length and direction of a stub, this model helps to infer the position of the opposite stub. par We show that, for a fixed stub--edge length ratio ��, not all graphs have a ��-SHPED. Specifically, we show that \($K_165$\) does not have a 1/4-SHPED, while bandwidth-\($k$\) graphs always have a \($\Theta(1/\sqrtk)$\)-SHPED. We also give bounds for complete bipartite graphs. Further, we consider the problem MAXSPED where the task is to compute the SPED of maximum total stub length that a given straight-line drawing contains. We present an efficient solution for 2-planar drawings and a 2-approximation algorithm for the dual problem of minimizing the total amount of erased ink.
Wamser, F., Höfner, S., Seufert, M., Tran-Gia, P.: Server and Content Selection for MPEG DASH Video Streaming with Client Information.ACM SIGCOMM Workshop on QoE-based Analysis and Management of Data Communication Networks (Internet-QoE). , Los Angeles, CA, USA (2017).
In HTTP adaptive streaming (HAS), such as MPEG DASH, the video is split into chunks and is available in different quality levels. If the video chunks are stored or cached on different servers to deal with the high load in the network and the Quality of Experience (QoE) requirements of the users, the problem of content selection arises. In this paper, we evaluate client-side algorithms for dynamically selecting an appropriate content server during DASH video streaming. We present three algorithms with which the DASH client itself can determine the most appropriate server based on client-specific metrics, like actual latency or bandwidth to the content servers. We evaluate and discuss the proposed algorithms with respect to the resulting DASH streaming behavior in terms of buffer levels and quality level selection.
Gray, N., Lorenz, C., Müssig, A., Gebert, S., Zinner, T., Tran-Gia, P.: A Priori State Synchronization for Fast Failover of Stateful Firewall VNFs.Workshop on Software-Defined Networking and Network Function Virtualization for Flexible Network Management (SDNFlex 2017). , Göttingen, Germany (2017).
Network Functions Virtualization (NFV) replaces physical middleboxes with software instances running network functions in cloud environments. To support this new paradigm, it is necessary to port the code basis from highly specialized hardware devices to virtual machines running on COTS hard- ware. In order to fully exploit the inherent capabilities of cloud environments it is further necessary to redesign the software to support a large amount of distributed, cooperating function instances instead of single, isolated and monolithic instances. This development can be observed for network functions like stateful firewalling. Until now, available software firewalls lack support for active/active operation in clustered environments, which hinders horizontal scalability. This is due to the fact that the required synchronization of connection states among the cluster’s instances is an impediment that still has to be resolved. Therefore, this work investigates different synchronization strategies and mechanisms, which allow to share connection states among the cluster to maintain scalability and high-availability
Bruschke, J., Niebling, F., Maiwald, F., Friedrichs, K., Wacker, M., Latoschik, M.E.: Towards Browsing Repositories of Spatially Oriented Historic Photographic Images in 3D Web Environments.Proceedings of Web3D ’17, Brisbane, QLD, Australia (2017).
Archives and museums store vast collections of historical images of urban areas and make them publicly available through online platforms. Many of these images, often containing historic buildings and landscapes, can be oriented spatially using automatic methods such as structure from motion (SfM). Providing spatially and temporally oriented images of urban architecture, in combination with advanced searching and 2D/3D exploration techniques, offers new potentials in supporting historians in their research. We are developing a 3D web environment usable to historians to spatially search online media repositories containing historic photographic images. We combine 3D models of historic buildings with spatially oriented images, replacing text-based searching through meta-data with spatial and temporal browsing with respect to given focus points in historic city models.
Gebert, S.: Architectures for Softwarized Networks and their Performance Evaluation, (2017).
Sperlich, B., Becker, M., Hotho, A., Wallmann-Sperlich, B., Sareban, M., Winkert, K., Steinacker, J.M., Treff, G.: Sedentary Behavior among National Elite Rowers during Off-Training—A Pilot Study.Frontiers in Physiology.8,655 (2017).
The aim of this pilot study was to analyze the off-training physical activity (PA) profile in national elite German U23 rowers during 31 days of their preparation period. The hours spent in each PA category (i.e. sedentary: <1.5 MET; light physical activity: 1.5–3 MET; moderate physical activity: 3–6 MET and vigorous intense physical activity: >6 MET) were calculated for every valid day (i.e. > 480 min of wear time). The off-training PA during 21 weekdays and 10 weekend days of the final 11-wk preparation period was assessed by a wrist-worn multisensory device (Microsoft Band II (MSBII)). A total of 11 rowers provided valid data (i.e. > 480 min/day) for 11.6 week days and 4.8 weekend days during the 31 days observation period. The average sedentary time was 11.63±1.25 hours per day during the week and 12.49±1.10 hours per day on the weekend, with a tendency to be higher on the weekend compared to weekdays (p = 0.06; d = 0.73). The average time in light, moderate and vigorous PA during the weekdays was 1.27±1.15, 0.76±0.37, 0.51±0.44 hours per day and 0.67±0.43, 0.59±0.37, 0.53±0.32 hours per weekend day. Light physical activity was higher during weekdays compared to the weekend (p = 0.04; d = 0.69) Based on our pilot study of eleven national elite rowers we conclude that rowers display a considerable sedentary off-training behavior of more than 11.5 hours/day.
Pfaff, B., Lorenz, C., Durner, R., Zinner, T.: SDN/NFV-enabled Security Architecture for Enterprise Networks., Infosim® Global Webinar Day (https://www.infosim.net/resources/webinars/sdn-nfv-enabled-security-architecture-for-enterprise-networks-global-webinar-day-september-28th-2017/) (2017).
Tönsing, L.: Semi-automated Generation of Image Annotations using Crowdsourcing and Tools for automated Translation, (2017).
Borchert, K.: Unemployment and Online Labor., Workshop on Flexible Work in the Digital Age, ZEW Mannheim, Germany (2017).
Roth, D., Lugrin, J.-L., Latoschik, M.E., Huber, S.: Alpha IVBO - Construction of a Scale to Measure the Illusion of Virtual Body Ownership.Proceedings of the 2017 CHI Conference Extended Abstracts on Human Factors in Computing Systems. S. 2875-2883 (2017).
In this paper, we present a scale construction and its initial test as a step towards a standardized measure of the illusion of virtual body ownership (IVBO) in virtual simulations. The IVBO describes the effect of users partly or fully perceiving a virtual body as their own. We analyzed components for a scale we call u0027Alpha IVBOu0027 by using data from a fake mirror scenario study. Users saw their movements mapped in real-time to a virtual avatar rendered on 3D display placed in front of them. The principal component analysis of our sample data resulted in three factors: u0027acceptanceu0027, u0027controlu0027 and u0027changeu0027.
Moldovan, C., Burger, V., Metzger, F., Surminski, S., Hoßfeld, T.: Viability of Wi-Fi Caches in an Era of HTTPS Prevalence.IEEE ICC'17: Bridging People, Communities, and Cultures. , Paris, France (2017).
Caches are often employed to better manage the ever-growing amount of global Internet traffic. Particularly, reverse proxies are often used to free up congested peering links and reduce inter-domain traffic. In addition, caches place content close to the edge, leading to lower latency which can be beneficial for many applications. In an effort to bring content even closer to end devices, home routers and public access points are now in the spotlight as a novel location for caches. Compared to CDNs, a Wi-Fi router only offers scarce storage and processing capabilities, putting an increased emphasis on resource management. In addition, a large share of traffic is transmitted through secured connections preventing the use of forward caches and other middle boxes. This paper strives to analyze how effective caching can be in public Wi-Fi routers. For this purpose, we conducted a field study with caches at public Wi-Fi hotspots in a field study. In addition, we present a queueing model for caches that we use to perform a mean-value analysis. We compare results from both methods in a performance analysis. Our results provide insights into difficulties of caching systems that are caused by an increase in the ratio of secured connections in the Internet.
Borchert, K., Hirth, M., Zinner, T., Göritz, A.: Designing a Survey Tool for Monitoring Enterprise QoE.ACM SIGCOMM Workshop on QoE-based Analysis and Management of Data Communication Networks (Internet-QoE). , Los Angeles, CA, USA (2017).
Enterprise applications like SAP are part of the day-to-day work of a large number of employees. Similar to many modern applications, enterprise applications are often implemented in a distributed fashion and consequently suffer from network degradations resulting in impairments like increased loading delays. While the influence of these impairments on the perceived quality of users is well researched for consumer applications and network services, the impact of these impairments in a business environment is still unclear. To address this gap we develop a non-intrusive software tool for continuously collecting subjective ratings on the performance of an enterprise application from a large crowd of employees. Based on the feedback from a company and results from two initial field studies we discuss the specific challenges when assessing the perceived quality of employees during regular working hours and point our further research directions.
Seufert, M., Wehner, N., Wamser, F., Casas, P., D'Alconzo, A., Tran-Gia, P.: Unsupervised QoE Field Study for Mobile YouTube Video Streaming with YoMoApp.9th International Conference on Quality of Multimedia Experience (QoMEX). , Erfurt, Germany (2017).
YoMoApp (YouTube Monitoring App) is an Android app to monitor mobile YouTube video streaming on both application- and network-layer. Additionally, it allows to collect subjective Quality of Experience (QoE) feedback of end users. During the development of the app, the stable versions of YoMoApp were already available in the Google Play Store, and the app was downloaded, installed, and used on many devices to monitor streaming sessions. As the app was not advertised in special campaigns or used for dedicated QoE studies, the monitored streaming sessions of this period compose the data set of a large unsupervised field study. The collected data set is evaluated to characterize current mobile YouTube streaming on both application and network layers. Furthermore, the problems and methodology to obtain QoE results from such unsupervised field study are discussed together with the actual QoE results. Correlations between QoE factors are investigated, and the QoE of clusters of similar streaming sessions is analyzed.
Zinner, T., Geissler, S., Lange, S., Gebert, S., Seufert, M., Tran-Gia, P.: A Discrete-Time Model for Optimizing the Processing Time of Virtualized Network Functions.Computer Networks.125,4-14 (2017).
The softwarization of networks promises cost savings and better scalability of network functions by moving functionality from specialized devices into commercial off-the-shelf hardware. Generalized computing hardware offers many degrees of adjustment and tuning, which can affect performance and resource utilization. One of these adjustments are interrupt moderation techniques implemented by modern network interface cards and operating systems. Using these, an administrator can optimize either for low latencies or low CPU overhead for processing of network traffic. In this work, an analytical model that allows the computation of relevant performance metrics like packet processing time and packet loss for generic virtualized network functions running on commodity hardware is presented. Based on this model, impact factors like average packet interarrival time, interarrival time distribution, and duration of the interrupt aggregation interval are studied. Furthermore, we significantly improve the computational tractability of this discrete-time model by proving and leveraging a property regarding its limit behavior. We also demonstrate that using this property does not affect the accuracy of the model in the context of realistic parameter combinations. Finally, the improved runtime for numerical evaluations allows administrators to dynamically adapt their interrupt mitigation settings to changing network conditions by recalculating optimal parameters.
Cofano, G., De Cicco, L., Zinner, T., Nguyen-Ngoc, A., Tran-Gia, P., Mascolo, S.: Design and Performance Evaluation of Network-assisted Control Strategies for HTTP Adaptive Streaming.ACM Transactions on Multimedia Computing, Communications, and Applications. (2017).
Casas, P., D'Alconzo, A., Wamser, F., Seufert, M., Gardlo, B., Schwind, A., Tran-Gia, P., Schatz, R.: Predicting QoE in Cellular Networks using Machine Learning and in-Smartphone Measurements.9th International Conference on Quality of Multimedia Experience (QoMEX). , Erfurt, Germany (2017).
Monitoring the Quality of Experience (QoE) undergone by cellular network customers has become paramount for cellular ISPs, who need to ensure high quality levels to limit customer churn due to quality dissatisfaction. This paper tackles the problem of QoE monitoring, assessment and prediction in cellular networks, relying on end-user device (i.e., smartphone) QoS passive traffic measurements and QoE crowdsourced feedback. We conceive different QoE assessment models based on supervised machine learning techniques, which are capable to predict the QoE experienced by the end user of popular smartphone apps (e.g., YouTube and Facebook), using as input the passive in-device measurements. Using a rich QoE dataset derived from field trials in operational cellular networks, we benchmark the performance of multiple machine learning based predictors, and construct a decision-tree based model which is capable to predict the per-user overall experience and service acceptability with a success rate of 91% and 98% respectively. To the best of our knowledge, this is the first paper using end-user, in-device passive measurements and machine learning models to predict the QoE of smartphone users in operational cellular networks.
Seufert, M., Zach, O., Slanina, M., Tran-Gia, P.: Unperturbed Video Streaming QoE Under Web Page Related Context Factors.9th International Conference on Quality of Multimedia Experience (QoMEX). , Erfurt, Germany (2017).
Quality of Experience (QoE) of Internet services is affected by human, system, and context influence factors. While most QoE studies so far are focused on system factors only, this work will assess the impact of context factors of video streaming on QoE. As video streaming is mostly consumed from web pages, such as video portals, the investigated test conditions are applied to the web page, which embeds the video player. Therefore, the study of context factors is implicitly conducted within a crowdsourced QoE study. The test conditions considered different page load times, poster image qualities, and displayed advertisements on the web page, which are typical context factors when consuming a video streaming service. The results of the study show that the modification of the context factors on the streaming web page leaves the users' QoE rating unperturbed, which suggests that the investigated context factors have a negligible impact on video streaming QoE, or that the rating task of the subjective QoE study superimposed the context factors.
Wehner, N.: Simulative Evaluation of the QoE Fairness of HAS Adaptation Logics, (2017).
Seufert, M., Kamneng Kwam, B., Wamser, F., Tran-Gia, P.: EdgeNetworkCloudSim: Placement of Service Chains in Edge Clouds Using NetworkCloudSim.1st IEEE International Workshop on Network Programmability - From the Data Center to the Ground (NetFoG). , Bologna, Italy (2017).
Edge cloud computing is a trending paradigm, which extends cloud computing by additionally utilizing computing resources at the network edge, e.g., at mobile base stations. Especially personalized services can be instantiated or migrated close to end users, which improves the latency and supports user mobility. However, the placement of the service chains is crucial for the performance of the services and the energy consumption of the edge cloud platform, and appropriate algorithms have to be designed. To support the simulative performance evaluation of such algorithms, EdgeNetworkCloudSim was developed. It is an extension of NetworkCloudSim, and allows to simulate and evaluate the orchestration and consolidation of service chains in an edge network cloud.
Ott, M.: Extraction of SDN Device Fingerprints for Enhancing the Network Security, (2017).
Niebler, T., Hahn, L., Hotho, A.: Learning Word Embeddings from Tagging Data: A methodological comparison.Proceedings of the LWDA (2017).
Latoschik, M.E., Weilbach, F., Hamzeheinejad, N., Gall, D.: VRGait: An Immersive Virtual Reality System for Gait-Specific Neurorehabilitation and Therapy.European Congress of NeuroRehabilitation 2017: ECNR2017. , Lausanne (2017).
