| 1. |
- Yanggratoke, Rerngvit, 1983-
(författare)
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Data-driven Performance Prediction and Resource Allocation for Cloud Services
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cloud services, which provide online entertainment, enterprise resource management, tax filing, etc., are becoming essential for consumers, businesses, and governments. The key functionalities of such services are provided by backend systems in data centers. This thesis focuses on three fundamental problems related to management of backend systems. We address these problems using data-driven approaches: triggering dynamic allocation by changes in the environment, obtaining configuration parameters from measurements, and learning from observations. The first problem relates to resource allocation for large clouds with potentially hundreds of thousands of machines and services. We developed and evaluated a generic gossip protocol for distributed resource allocation. Extensive simulation studies suggest that the quality of the allocation is independent of the system size for the management objectives considered.The second problem focuses on performance modeling of a distributed key-value store, and we study specifically the Spotify backend for streaming music. We developed analytical models for system capacity under different data allocation policies and for response time distribution. We evaluated the models by comparing model predictions with measurements from our lab testbed and from the Spotify operational environment. We found the prediction error to be below 12% for all investigated scenarios.The third problem relates to real-time prediction of service metrics, which we address through statistical learning. Service metrics are learned from observing device and network statistics. We performed experiments on a server cluster running video streaming and key-value store services. We showed that feature set reduction significantly improves the prediction accuracy, while simultaneously reducing model computation time. Finally, we designed and implemented a real-time analytics engine, which produces model predictions through online learning.
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| 2. |
- Zhang, Kewei
(författare)
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Secure GNSS-based Positioning and Timing : Distance-Decreasing attacks, fault detection and exclusion, and attack detection with the help of opportunistic signals
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With trillions of devices connected in large scale systems in a wired or wireless manner, positioning and synchronization become vital. Global Navigation Satellite System (GNSS) is the first choice to provide global coverage for positioning and synchronization services. From small mobile devices to aircraft, from intelligent transportation systems to cellular networks, and from cargo tracking to smart grids, GNSS plays an important role, thus, requiring high reliability and security protection. However, as GNSS signals propagate from satellites to receivers at distance of around 20 000 km, the signal power arriving at the receivers is very low, making the signals easily jammed or overpowered. Another vulnerability stems from that civilian GNSS signals and their specifications are publicly open, so that anyone can craft own signals to spoof GNSS receivers: an adversary forges own GNSS signals and broadcasts them to the victim receiver, to mislead the victim into believing that it is at an adversary desired location or follows a false trajectory, or adjusts its clock to a time dictated by the adversary. Another type of attack is replaying GNSS signals: an adversary transmits a pre-recorded GNSS signal stream to the victim receiver, so that the receiver calculates an erroneous position and time. Recent incidents reported in press show that the GNSS functionalities in a certain area, e.g., Black Sea, have been affected by cyberattacks composed of the above-mentioned attack types. This thesis, thus, studies GNSS vulnerabilities and proposes detection and mitigation methods for GNSS attacks, notably spoofing and replay attacks. We analyze the effectiveness of one important and powerful replay attack, the so-called Distance-decreasing (DD) attacks that were previously investigated for wireless communication systems, on GNSS signals. DD attacks are physical layer attacks, targeting time-of-flight ranging protocols, to shorten the perceived as measured distance between the transmitter and receiver. The attacker first transmits an adversary-chosen data bit to the victim receiver before the signal arrives at the attacker; upon receipt of the GNSS signal, the attacker estimates the data bit based on the early fraction of the bit period, and then switches to transmitting the estimate to the victim receiver. Consequently, the DD signal arrives at the victim receiver earlier than the genuine GNSS signals would have, which in effect shortens the pseudorange measurement between the sender (satellite) and the victim receiver, consequently, affecting the calculated position and time of the receiver. We study how the DD attacks affect the bit error rate (BER) of the received signals at the victim, and analyze its effectiveness, that is, the ability to shorten pseudorange measurements, on different GNSS signals. Several approaches are considered for the attacker to mount a DD attack with high probability of success (without being detected) against a victim receiver, for cryptographically unprotected and protected signals. We analyze the tracking output of the DD signals at the victim receiver and propose a Goodness of Fit (GoF) test and a Generalized Likelihood Ratio Test (GLRT) to detect the attacks. The evaluation of the two tests shows that they are effective, with the result being perhaps more interesting when considering DD attacks against Galileo signals that can be cryptographically protected. Moreover, this thesis investigates the feasibility of validating the authenticity of the GNSS signals with the help of opportunistic signals, which is information readily available in modern communication environments, e.g., 3G, 4G and WiFi. We analyze the time synchronization accuracy of different technologies, e.g., Network Time Protocol (NTP), WiFi and local oscillator, as the basis for detecting a discrepancy with the GNSS-obtained time. Two detection approaches are proposed and one testbench is designed for the evaluation. A synthesized spoofing attack is used to verify the effectiveness of the approaches. Beyond attack detection, we develop algorithms to detect and exclude faulty signals, namely the Clustering-based Solution Separation Algorithm (CSSA) and the Fast Multiple Fault Detection and Exclusion (FM-FDE). They both utilize the redundant available satellites, more than the minimum a GNSS receiver needs for position and time offset calculation. CSSA adopts data clustering to group subsets of positions calculated with different subsets of available satellites. Basically, these positions, calculated with subsets not containing any faulty satellites, should be close to each other, i.e., in a dense area; otherwise they should be scattered. FM-FDE is a more efficient algorithm that uses distances between positions, calculated with fixed-size subsets, as test statistics to detect and exclude faulty satellite signals. As the results show, FM-FDE runs faster than CSSA and other solution-separation fault detection and exclusion algorithms while remaining equally effective.
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| 3. |
- Khan, Muhammad Sikandar Lal, 1988-
(författare)
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Presence through actions : theories, concepts, and implementations
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During face-to-face meetings, humans use multimodal information, including verbal information, visual information, body language, facial expressions, and other non-verbal gestures. In contrast, during computer-mediated-communication (CMC), humans rely either on mono-modal information such as text-only, voice-only, or video-only or on bi-modal information by using audiovisual modalities such as video teleconferencing. Psychologically, the difference between the two lies in the level of the subjective experience of presence, where people perceive a reduced feeling of presence in the case of CMC. Despite the current advancements in CMC, it is still far from face-to-face communication, especially in terms of the experience of presence.This thesis aims to introduce new concepts, theories, and technologies for presence design where the core is actions for creating presence. Thus, the contribution of the thesis can be divided into a technical contribution and a knowledge contribution. Technically, this thesis details novel technologies for improving presence experience during mediated communication (video teleconferencing). The proposed technologies include action robots (including a telepresence mechatronic robot (TEBoT) and a face robot), embodied control techniques (head orientation modeling and virtual reality headset based collaboration), and face reconstruction/retrieval algorithms. The introduced technologies enable action possibilities and embodied interactions that improve the presence experience between the distantly located participants. The novel setups were put into real experimental scenarios, and the well-known social, spatial, and gaze related problems were analyzed.The developed technologies and the results of the experiments led to the knowledge contribution of this thesis. In terms of knowledge contribution, this thesis presents a more general theoretical conceptual framework for mediated communication technologies. This conceptual framework can guide telepresence researchers toward the development of appropriate technologies for mediated communication applications. Furthermore, this thesis also presents a novel strong concept – presence through actions - that brings in philosophical understandings for developing presence- related technologies. The strong concept - presence through actions is an intermediate-level knowledge that proposes a new way of creating and developing future 'presence artifacts'. Presence- through actions is an action-oriented phenomenological approach to presence that differs from traditional immersive presence approaches that are based (implicitly) on rationalist, internalist views.
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| 4. |
- Bengtsson, Lars, 1963
(författare)
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Embedded Measurement Systems
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The subject of Embedded Measurement Systems (EMS) is the merging of embedded systems and electrical measurement systems. This indicates that EMSs are hardware-software systems dedicated to measuring one or a few physical quantities. Applications are numerous; EMSs measure the temperature in refrigerators, freezers, irons, ovens and automobile combustion engines, they sense vibrations in tilt alarms and game consoles, they measure airflow in engines and ventilation systems, they measure shock impact in crash detectors and are used as shock and temperature loggers for transport goods, they measure air pressure in airplane cabins, humidity in air-conditioned environments, they measure liquid levels in fuel tanks, they detect smoke in fire alarms, they measure the viscosity of lubricant oil in engines, they measure the rotation speed of spinning wheels (in any engine), they measure torque in engines and are used as heart rate and ECG detectors in medicine etc. The commercial demand for ever cheaper products and worldwide environmental legislations force vendors to continuously look for more cost-efficient and less power-consuming solutions for their embedded measurement systems. This thesis is concerned most of all with the implementation of cost-efficient/low-power measurement systems in embedded controllers. This includes some novel ideas in voltage, time and resistance measurements with embedded controllers and it will demonstrate how these quantities, analog in nature, can be measured accurately and precisely by inherently digital embedded controllers.
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| 5. |
- Jiang, Yuning, 1993-
(författare)
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Vulnerability Analysis for Critical Infrastructures
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rapid advances in information and communication technology enable a shift from diverse systems empowered mainly by either hardware or software to cyber-physical systems (CPSs) that are driving Critical infrastructures (CIs), such as energy and manufacturing systems. However, alongside the expected enhancements in efficiency and reliability, the induced connectivity exposes these CIs to cyberattacks exemplified by Stuxnet and WannaCry ransomware cyber incidents. Therefore, the need to improve cybersecurity expectations of CIs through vulnerability assessments cannot be overstated. Yet, CI cybersecurity has intrinsic challenges due to the convergence of information technology (IT) and operational technology (OT) as well as the crosslayer dependencies that are inherent to CPS based CIs. Different IT and OT security terminologies also lead to ambiguities induced by knowledge gaps in CI cybersecurity. Moreover, current vulnerability-assessment processes in CIs are mostly subjective and human-centered. The imprecise nature of manual vulnerability assessment operations and the massive volume of data cause an unbearable burden for security analysts. Latest advances in machine-learning (ML) based cybersecurity solutions promise to shift such burden onto digital alternatives. Nevertheless, the heterogeneity, diversity and information gaps in existing vulnerability data repositories hamper accurate assessments anticipated by these ML-based approaches. Therefore, a comprehensive approach is envisioned in this thesis to unleash the power of ML advances while still involving human operators in assessing cybersecurity vulnerabilities within deployed CI networks.Specifically, this thesis proposes data-driven cybersecurity indicators to bridge vulnerability management gaps induced by ad-hoc and subjective auditing processes as well as to increase the level of automation in vulnerability analysis. The proposed methodology follows design science research principles to support the development and validation of scientifically-sound artifacts. More specifically, the proposed data-driven cybersecurity architecture orchestrates a range of modules that include: (i) a vulnerability data model that captures a variety of publicly accessible cybersecurity-related data sources; (ii) an ensemble-based ML pipeline method that self-adjusts to the best learning models for given cybersecurity tasks; and (iii) a knowledge taxonomy and its instantiated power grid and manufacturing models that capture CI common semantics of cyberphysical functional dependencies across CI networks in critical societal domains. This research contributes data-driven vulnerability analysis approaches that bridge the knowledge gaps among different security functions, such as vulnerability management through related reports analysis. This thesis also correlates vulnerability analysis findings to coordinate mitigation responses in complex CIs. More specifically, the vulnerability data model expands the vulnerability knowledge scope and curates meaningful contexts for vulnerability analysis processes. The proposed ML methods fill information gaps in vulnerability repositories using curated data while further streamlining vulnerability assessment processes. Moreover, the CI security taxonomy provides disciplined and coherent support to specify and group semanticallyrelated components and coordination mechanisms in order to harness the notorious complexity of CI networks such as those prevalent in power grids and manufacturing infrastructures. These approaches learn through interactive processes to proactively detect and analyze vulnerabilities while facilitating actionable insights for security actors to make informed decisions.
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| 6. |
- Krook, Jonas, 1986
(författare)
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Formal Methods and Safety for Automated Vehicles: Modeling, Abstractions, and Synthesis of Tactical Planners
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One goal of developing automated road vehicles is to completely free people from driving tasks. Automated vehicles with no human driver must handle all traffic situations that human drivers are expected to handle, possibly more. Though human drivers cause a lot of traffic accidents, they still have a very low accident and failure rate that automated vehicles must match. Tactical planners are responsible for making discrete decisions for the coming seconds or minutes. As with all subsystems in an automated vehicle, these planners need to be supported with a credible and convincing argument of their correctness. The planners interact with other road users in a feedback loop, so their correctness depends on their behavior in relation to other drivers and road users over time. One way to ascertain their correctness is to test the vehicles in real traffic. But to be sufficiently certain that a tactical planner is safe, it has to be tested on 255 million miles with no accidents. Formal methods can, in contrast to testing, mathematically prove that given requirements are fulfilled. Hence, these methods are a promising alternative for making credible arguments for tactical planners’ correctness. The topic of this thesis is the use of formal methods in the automotive industry to design safe tactical planners. What is interesting is both how automotive systems can be modeled in formal frameworks, and how formal methods can be used practically within the automotive development process. The main findings of this thesis are that it is viable to formally express desired properties of tactical planners, and to use formal methods to prove their correctness. However, the difficulty to anticipate and inspect the interaction of several desired properties is found to be an obstacle. Model Checking, Reactive Synthesis, and Supervisory Control Theory have been used in the design and development process of tactical planners, and these methods have their benefits, depending on the application. To be feasible and useful, these methods need to operate on both a high and a low level of abstraction, and this thesis contributes an automatic abstraction method that bridges this divide. It is also found that artifacts from formal methods tools may be used to convincingly argue that a realization of a tactical planner is safe, and that such an argument puts formal requirements on the vehicle’s other subsystems and its surroundings.
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| 7. |
- Rico, Sergio
(författare)
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Building Stronger Bridges: Strategies for Improving Communication and Collaboration Between Industry and Academia in Software Engineering
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The software engineering community has expressed growing concern regarding the need for more connections between research and practice. Despite the large amount of knowledge researchers generate, its impact on real-world practice is uncertain. Meanwhile, practitioners in industry often struggle to access and utilize relevant research outcomes that could inform and enhance their work. Collaboration between industry and academia is seen as a potential solution to bridge this gap, ensuring that research remains relevant and applicable in real-world contexts.Objective: This research aims to explore challenges in communication and collaboration between industry and to design, evaluate, and implement strategies that foster this collaboration. Methodology: The design science paradigm inspires this research, as we aim to obtain knowledge about industry-academia communication and collaboration by studying challenges and solutions in context. The thesis includes case studies; some are exploratory, while others focus on evaluating specific strategies.Results: In terms of problem understanding, we identified challenges that impact communication and collaboration, such as different expectations, perspectives, and ways of working. Furthermore, we pinpointed factors facilitating communication, including long-term projects, research relevance, and practitioners' involvement.Regarding how to improve communication and collaboration, we investigated two strategies. The first strategy involves using the SERP-taxonomy approach in a project on software vulnerability management in IoT systems. The second strategy involves the proposal of interactive rapid reviews, conducted in close collaboration with practitioners. We share the lessons from conducting two reviews (one in testing machine learning systems and the other in software component selection). The benefits of conducting interactive rapid reviews include mutual understanding, the development of networks, and increased motivation for further studies.Conclusion: The thesis emphasizes the importance of industry-academia collaboration as a key aspect in closing gaps between research and practice. The strategies discussed provide tools to understand industry-academia partnerships better and support future collaborations.
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| 8. |
- Lavassani, Mehrzad
(författare)
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Evolving Industrial Networks : Data-Driven Network Traffic Modelling and Monitoring
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The concept of Industrial IoT encompasses the joint applicability of operation and information technologies to expand the efficiency expectation of automation to green and flexible processes with innovative products and services. Future industrial networks need to accommodate, manage and guarantee the performance of converged traffic from different technologies. The network infrastructures are transforming to enable data availability for advanced applications and enhance flexibility. Nonetheless, the pace of IT–OT networks development has been slow despite their considered benefits in optimising performance and enhancing information flows. The hindering factors vary from general challenges in performance management of the diverse traffic for greenfield configuration to the lack of outlines for evolving from brownfield installations without interrupting the operation of ongoing processes. One tangible gap is the lack of insight into the brownfield installation in operation. This dissertation explores the possible evolutionary steps from brownfield installations to future industrial networks.The goal is to ensure the uninterrupted performance of brownfield installations on the path of evolving to the envisioned smart factories. It addresses the gap between the state of the art and state of practice, and the technical prerequisites of the integrated traffic classes for the development of an IIoT monitoring mechanism. A novel lightweight learning algorithm at the sensor level for an IIoT compliance monitoring system, together with a case study of traffic collected from a brownfield installation, provides the baseline of comparative analysis between the common assumptions and the state of practice. The identified gaps and challenges to address them directs the research for proposing a two-step aggregated traffic modelling by introducing new measurement method and performance indicator parameters for capturing the communication dynamics. Lastly, the sensor-level learning algorithm is refined with the knowledge gained from practice and research contributions to propose an in-band telemetry mechanism for monitoring aggregated network traffic.
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| 9. |
- Muddala, Suryanarayana Murthy, 1984-
(författare)
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Free View Rendering for 3D Video : Edge-Aided Rendering and Depth-Based Image Inpainting
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Three Dimensional Video (3DV) has become increasingly popular with the success of 3D cinema. Moreover, emerging display technology offers an immersive experience to the viewer without the necessity of any visual aids such as 3D glasses. 3DV applications, Three Dimensional Television (3DTV) and Free Viewpoint Television (FTV) are auspicious technologies for living room environments by providing immersive experience and look around facilities. In order to provide such an experience, these technologies require a number of camera views captured from different viewpoints. However, the capture and transmission of the required number of views is not a feasible solution, and thus view rendering is employed as an efficient solution to produce the necessary number of views. Depth-image-based rendering (DIBR) is a commonly used rendering method. Although DIBR is a simple approach that can produce the desired number of views, inherent artifacts are major issues in the view rendering. Despite much effort to tackle the rendering artifacts over the years, rendered views still contain visible artifacts.This dissertation addresses three problems in order to improve 3DV quality: 1) How to improve the rendered view quality using a direct approach without dealing each artifact specifically. 2) How to handle disocclusions (a.k.a. holes) in the rendered views in a visually plausible manner using inpainting. 3) How to reduce spatial inconsistencies in the rendered view. The first problem is tackled by an edge-aided rendering method that uses a direct approach with one-dimensional interpolation, which is applicable when the virtual camera distance is small. The second problem is addressed by using a depth-based inpainting method in the virtual view, which reconstructs the missing texture with background data at the disocclusions. The third problem is undertaken by a rendering method that firstly inpaint occlusions as a layered depth image (LDI) in the original view, and then renders a spatially consistent virtual view.Objective assessments of proposed methods show improvements over the state-of-the-art rendering methods. Visual inspection shows slight improvements for intermediate views rendered from multiview videos-plus-depth, and the proposed methods outperforms other view rendering methods in the case of rendering from single view video-plus-depth. Results confirm that the proposed methods are capable of reducing rendering artifacts and producing spatially consistent virtual views.In conclusion, the view rendering methods proposed in this dissertation can support the production of high quality virtual views based on a limited number of input views. When used to create a multi-scopic presentation, the outcome of this dissertation can benefit 3DV technologies to improve the immersive experience.
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| 10. |
- Vosoogh, Abbas, 1984
(författare)
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Compact RF Integration and Packaging Solutions Based on Metasurfaces for Millimeter-Wave Applications
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The millimeter-wave frequency range has got a lot of attention over the past few years because it contains unused frequency spectrum resources that are suitable for delivering Gbit/s end-user access in areas with high user density. Due to the limited output power that the current RF active components can deliver in millimeter-wave frequencies, antennas with the features of low profile, high gain, high efficiency and low cost are needed to compensate free space path loss and increase the communication distance for the emerging high data rate wireless systems. Moreover, it is desired to have a compact system by integration of the antenna with passive and active components at high frequencies. In order to move towards millimeter-wave frequencies we need to face significant hardware challenges, such as active and passive components integration, packaging problems, and cost-effective manufacturing techniques. The gap waveguide technology shows interesting characteristics as a new waveguide structure. The main goal of this thesis is to demonstrate the advantages of gap waveguide technology as an alternative to the traditional guiding structures to overcome the problem of good electrical contact due to mechanical assembly with low loss. This thesis mainly focuses on high-gain planar array antenna design, integration with passive and active components, and packaging based on gap waveguide technology. We introduce several low-profile multilayer corporate-fed slot array antennas with high gain, high efficiency and wide impedance bandwidth operating at the millimeter-wave frequency band. A system demonstration consisting of two compact integrated antenna-diplexer and Tx/Rx MMICs for Frequency-division duplex (FDD) low latency wireless backhaul links at E-band is presented to show the advantages of gap waveguide technology in building a complete radio front-end. Moreover, the use of several new manufacturing methods, such as die-sink Electric Discharge Machining (EDM), direct metal 3-D printing, and micro-molding are evaluated to fabricate gap waveguide components in a more effective way. Furthermore, a novel air-filled transmission line, so-called multi-layer waveguide (MLW), that exhibits great advantages such as low-cost, simple fabrication, and low loss, even for frequencies beyond 100 GHz, is presented for the first time. To constitute an MLW structure, a rectangular waveguide transmission line is formed by stacking several thin metal layers without any electrical and galvanic contact requirement among the layers. The proposed concept could become a suitable approach to design millimeter-wave high-performance passive waveguide components, and to be used in active and passive components integration ensuring mass production at the same time.
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