05 Fakultät Informatik, Elektrotechnik und Informationstechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6

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Institute: search.filters.UBSInstitut.Institut für Parallele und Verteilte SystemeSubject: search.filters.subject.004Start date: 2023End date: 2023Publication Type: search.filters.UBSTyp.Abschlussarbeit (Master)

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Now showing 1 - 10 of 22
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    Ordering transactions on distributed persistent objects
    (2023) König, Simon
    Resilient and consistent data storage is critical for applications and services across all industries. As such, various persistent storage layers, such as database storage systems, have been developed. These either require complex data translations, commonly tackled through Object-Relational Mapping (ORM), or force the application to use data types specifically developed for persistent storage (e. g., Intel PMDK). Persistent objects describe a novel storage system that is able to persist and transactionally modify application-defined objects. With persistent objects, applications transactionally execute arbitrary functions on their existing data objects. However, they only allow local transactional modifications on individual objects, as there are no consistency guarantees across sequences of transactions. In this work, we present a novel distributed transaction coordination algorithm called Two-Phase Ordering (2PO) that provides isolation between concurrently executing clients. The algorithm uses application-specific knowledge, which becomes available through the use of application-native objects in the local persistent storage layer. Moreover, the distributed transaction execution order of 2PO depends entirely on the user’s desired semantics. Thus, the system accomodates both linearizable consistency as well as arbitrary interleavings of non-transactional interactions at the same time. By proving the consistency guarantees of 2PO in the general case, we show that our work is applicable to traditional transactional storage systems (e. g., databases) as well. Our evaluations show that 2PO supports linearizability as well as highly available transaction consistency models, such as Monotonic Atomic View (MAV), both with high commit rates (above 97 % under high contention), all while scaling linearly with the number of nodes.
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    Roaming with deterministic real-time guarantees in wireless Time-Sensitive Networking
    (2023) Haug, Lucas
    As Cyber-Physical Systems (CPSs) become increasingly popular in various domains such as Industrial Internet of Things (IIoT) and autonomous vehicles, the demand for deterministic real-time communication with a high reliability and bounded network delay and delay variance (jitter) has grown. In CPSs with networked sensors and actuators, these deterministic real-time bounds are often crucial in order to provide safety guarantees. Major standardization organizations like the Institute of Electrical and Electronics Engineers (IEEE) have acknowledged the necessity for deterministic networks, resulting in a set of standards known as Time-Sensitive Networking (TSN), which enable deterministic communication in wired Ethernet networks. Many CPSs, however, necessitate mobility and therefore rely on wirelessly connected devices, such as a worker wearing an exoskeleton in order to carry heavy loads. To this end, the TSN standards will also be part of the upcoming Wi-Fi 7 standard (IEEE 802.11be). Although the increased flexibility offered by the mobility of devices in these scenarios is advantageous, it presents new challenges, such as controlling access to the shared wireless transmission medium and managing handovers such that deterministic real-time guarantees are maintained. In this work, we investigate these challenges and provide novel approaches to improve the reliability, delay and jitter in wireless TSN. We first modify an already existing Integer Linear Program (ILP) to generate schedules for the Time-Aware Shaping (TAS) in a wireless network environment. The necessity for this arises because the wireless transmission medium utilizes a shared access method, whereas existing approaches are limited to point-to-point Ethernet connections. Furthermore, we provide a novel seamless handover approach for wireless TSN utilizing two wireless interfaces in a single device and extend it with a proactive handover approach in order to allow for smoother handovers with a greater reliability. In order to analyze our approaches, we extend the INET framework of the OMNeT++ simulator with an implementation of our approaches. Our evaluation shows that delay and jitter are mainly influenced by the random back-off algorithm of the channel access procedure in Wi-Fi indicating research topics for future work. Moreover, we were able to significantly improve the reliability for wireless TSN by employing our proactive handover approach in the simulation.
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    Algorithms for calculating robust schedules for time sensitive networking (TSN)
    (2023) Nieß, Adriaan
    With the 802.1Qbv standard, the time-sensitive networking (TSN) task group has specified a TDMA-based scheduling method based on Ethernet, that allows to ensure real-time guarantees for time-critical data streams. A major challenge here is the computation of the cyclic schedules required for the switch configurations in the network. There exist already a number of different approaches to calculate these schedules. However, most of them focus on supporting a high number of streams and optimize target functions such as the Makespan. This leads to schedules that are particularly fragile against errors in the system model. To close this gap, we have developed a scheduler based on simple temporal networks (STNs) that maximizes the intervals allocated for the transmission of data packets in order to ensure a very high degree of robustness against unforeseen delay or cross-traffic. In a simulation it could be shown that the calculated schedules could still guarantee a loss-free data transmission under compliance with all deadlines if the actual per-hop network delay deviated from the assumed delay by a factor of up to 7. Furthermore, an even larger error did not immediately lead to a breakdown, but to a gradual degradation. This makes the scheduling method presented here as well as the underlying algorithms particularly interesting for applications that come with a high degree of uncertainty in the system model, such as wireless communications or heterogeneous networks.
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    Entwurf und Implementierung eines Stream-basierten, dynamischen und fairen Scheduling-Verfahrens für WiFi-Netzwerkverkehr
    (2023) Herrmann, Jona
    Heutzutage sind Wireless Local Area Network (WLAN)-Netzwerke, basierend auf dem IEEE~802.11 Standard, für mobile Endgeräte besonders wichtig, da diese nur so Zugang zum Internet bekommen können. Dementsprechend gibt es solche Netzwerke fast überall wie beispielsweise in öffentlichen Verkehrsmitteln, in Hotels oder auch bei der Arbeit. Doch die Qualität und Geschwindigkeit einer Verbindung kann dabei stark variieren. Um dies zu verbessern, wird zuerst eine Analyse dieser Netzwerke vorgenommen, um die Stelle des Bottlenecks zu identifizieren. Dabei konnte gezeigt werden, dass der Bottleneck an zwei Stellen vorliegen könnte. Das wäre einmal der Uplink zum Internet und andererseits der entsprechende Downlink, wobei sich der Bottleneck am Downlink letztendlich beim Internet-Provider befindet. Mit einem neu entwickelten Stream-basierten, dynamischen und fairen Scheduling-Verfahren soll die Qualität und Geschwindigkeit im WLAN-Netzwerk verbessert werden. Dafür wird eine neue Art von Fairness definiert, sodass die Pakete von Endgeräten mit einem geringen Datenverbrauch eine höhere Priorität erhalten. Dadurch bekommen letztendlich Endgeräte, welche gutmütig sind, eine bessere Antwortzeit als diese, die eine große Datenmenge übertragen. Zum Schluss wird die Linux-Implementierung des Scheduling-Verfahrens noch unter verschiedenen Metriken evaluiert. Dabei konnte gezeigt werden, dass die gewünschte Art von Fairness damit realisiert werden kann. Dies wurde sowohl unter Laborbedingungen als auch mit realen Anwendungen des Internets erfolgreich evaluiert. Außerdem wurde durch Messungen gezeigt, dass es im Punkt Performanz keinen signifikanten Unterschied zu dem Standard Scheduling-Verfahren in Linux gibt.
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    Development of an Euler-Lagrangian framework for point-particle tracking to enable efficient multiscale simulations of complex flows
    (2023) Kschidock, Helena
    In this work, we implement, test, and validate an Euler-Lagrangian point-particle tracking framework for the commercial aerodynamics and aeroacoustics simulation tool ultraFluidX, which is based on the Lattice Boltzmann Method and optimized for GPUs. Our framework successfully simulates one-way and two-way coupled particle-laden flows based on drag forces and gravitation. Trilinear interpolation is used for determining the fluid's macroscopic properties at the particle position. Object and domain boundary conditions are implemented using a planar surface approximation. The whole particle framework is run within three dedicated GPU kernels, and data is only copied back to the CPU upon output. We show validation for the velocity interpolation, gravitational acceleration, back-coupling forces and boundary conditions, and test runtimes and memory requirements. We also propose the next steps required to make the particle framework ready for use in engineering applications.
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    Anonymisierung von Daten : von der Literatur zum Automobilbereich
    (2023) Herkommer, Jan
    Die Datenanonymisierung im Automobilbereich gewinnt immer mehr an Bedeutung. Jedoch gibt es kaum Literatur und Ansätze, die sich mit der Anonymisierung von Automobildaten beschäftigen. In dieser Arbeit werden deshalb mit Hilfe einer strukturierten Literaturrecherche die aktuell verbreitetsten Verfahren und Anwendungsbereiche erörtert und die wichtigsten Erkenntnisse der Recherche zusammengefasst. So werden bei den analysierten Paper der Anwendungsbereich, die Methodik sowie der zu anonymisierende Datentyp ermittelt. DesWeiteren werden die Metriken zum Vergleich von unterschiedlichen Ansätzen betrachtet. Mit Hilfe dieser Erkenntnisse wird im Anschluss auf die Anonymisierung von Fahrzeugdaten anhand verschiedener Anwendungsfälle eingegangen und Herausforderungen und Lösungsansätze skizziert. Zuletzt wird beispielhaft ein Ansatz zur Anonymisierung von Routen implementiert, um mit Hilfe eines GPS-Sensors aufgezeichnete Fahrzeugrouten zu anonymisieren. Dabei werden zusätzliche Probleme wie der Umgang mit Messungenauigkeiten und Messfehlern sowie die tatsächlichen Auswirkungen von reduzierter Datennutzbarkeit verdeutlicht.
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    Application integration and team collaboration for process optimization in intralogistics
    (2023) Bektas, Sabri
    This work focuses on the potential benefits of integrating software applications and promoting team collaboration to enhance intralogistic processes at Robert Bosch GmbH in Feuerbach. The current study is a synthesis of a comprehensive review of pertinent literature and the practical application of an architectural framework. This research addresses the gap in literature, which lacks comprehensive guidelines for choosing software architecture approaches aligned with non-functional requirements. The objectives are to determine the necessary functionalities for an integrated solution, evaluate existing solutions and technical models, design a target architecture and provide practical guidelines for implementation. The key research question revolves around how already existing solutions can be integrated to enhance intralogistics processes. To achieve these objectives, a comprehensive literature review is conducted to identify suitable software architecture approaches. The study evaluates various methodologies, considering non-functional requirements, culminating in an architecture ranking matrix. Additionally, interviews with project teams and analysis of user stories guide architectural decisions. The research emphasizes the microservices architecture as the selected approach for seamless integration. The message of this research is that the microservices architecture offers a scalable, modular, and efficient solution for optimizing intralogistic processes. By integrating existing software solutions and fostering effective teamwork, organizations can achieve enhanced sustainability and customer experience. This research contributes valuable insights and practical recommendations for leveraging existing solutions to develop comprehensive and efficient intralogistics application systems. The proposed architecture serves as a template and guideline for the Virtual Development Team at Robert Bosch GmbH, facilitating the realization of an optimized and sustainable target system for intralogistics. The research emphasizes the microservices architecture as the selected approach for seamless integration.
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    Investigation of multistability-affected period-incrementing and period-adding structures in a model of a power converter with symmetry
    (2023) Weik, Fabian
    Although the established theory of non-linear dynamical systems is effective at describing physical systems and phenomena, the theory has been developed with a focus on smooth systems, limiting its applicability in certain areas. This limitation becomes apparent when modeling piecewise-smooth systems such as electrical systems that contain at least one switching element or mechanical systems with collisions. This thesis deals with a model of a DC/AC power converter that is piecewise-smooth, discontinuous, and has a certain symmetry. The definition of this model is exceptionally complex, and the model exhibits an unusual period-incrementing structure that is affected by multistability. This thesis identifies the characteristics of the model that lead to this unusual bifurcation structure by constructing an archetypal model that exhibits the same bifurcation behavior. It follows a description of the dynamics of the archetypal model and an explanation of the bifurcation structure using the description of the dynamics. Additionally, this thesis demonstrates that the proposed archetypal model can exhibit behavior leading to bifurcation structures that are related to period-adding structures. The resulting bifurcation structures behave unexpectedly, and this behavior is explained by leveraging the symmetry present in both the archetypal and the original model. Using the symmetry present, the mathematical rules governing the resulting bifurcation structures are derived from the rules governing classical period-adding structures.
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    Automated data validation in model-driven IoT applications
    (2023) Müller, Christian
    Building large IoT applications using a model-driven approach, has become an important methodology for building such applications. A tool intended to help with this process is the IoT Application Modelling tool developed at the University of Stuttgart. However, this tool is lacking validation capabilities. To implement validation in a (semi) automated manner, this work proposes an approach to assist the modeller with the task of selecting the best suited outlier detection method for a context model. based on existing or accumulated data. To achieve this a semi-automated wizard, integrated into the IoT Application Modelling Tool is proposed. Furthermore, concepts on how the resulting outlier detection can be deployed on the IoT infrastructure are discussed. The provided value and the usability of the tool are evaluated using a survey on a small set of researchers and IT professionals. The result of this survey have shown, that the proposed approach does partially automate and simplify the process of choosing an machine-learning based outlier detection method.
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    Live adaptation of privacy-enhancing technologies in connected vehicles' data pipelines
    (2023) Zhu, Xinxin
    Connected vehicles are able to acquire and share enormous amount of information with various onboard sensors and network communication. The information sharing can cause privacy concerns. The uniqueness of these concerns lies in the mobility of connected vehicles, which encounter different situations regularly. Different situations may have different requirements on the intensity of privacy protection. Thus, a situational policy for privacy protection should be applied. To enable a connected vehicle to carry out the situational policy correctly and effectively, we propose “Adaptive Privacy in Flow”, a framework that utilizes stream processing technology to adapt the privacy-enhancing technologies within a connected vehicle’s data pipeline through continuous evaluation of the environments. Our framework provides a solution of applying the situational privacy policy accordingly to the sensor data. It reacts to situational changes automatically, without restart or user intervention. Besides, it allows simultaneous and individual dynamic privacy protection for different third-party applications. Moreover, it is capable of handling the diversity of the data types in connected vehicles, from simple scalar value to complex data type like the images, ensuring a comprehensive privacy protection.