Fak. 4 Elektrotechnik und Informatik

1266 Items

Recent Submissions
A Response to the United Nations CITES Blockchain Challenge: Incremental and Integrative PoA-based Permit Exchange

Busse, Anselm ; Eberhardt, Jacob ; Frost, Sebastian ; Kim, Dong-Ha ; Weilbier, Thore ; Renner, Lukas ; Roth, Matthias ; Tai, Stefan (2019)

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) negotiated and administered by the United Nations Environment Programme (UNEP) regulates the international trade of endangered species and derived products through a permit-based system. Currently, the permit process is paper-based and hence highly prone to manipulations and errors. Being aware of blockc...

Exploring Deployment Strategies for the Tor Network

Döpmann, Christoph ; Rust, Sebastian ; Tschorsch, Florian (2018)

In response to upcoming performance and security challenges of anonymity networks like Tor, it will be of crucial importance to be able to develop and deploy performance improvements and state-of-the-art countermeasures. In this paper, we therefore explore different deployment strategies and review their applicability, impact, and risks to the Tor network. In a simulation-based evaluation, whic...

Towards a Concurrent and Distributed Route Selection for Payment Channel Networks

Rohrer, Elias ; Laß, Jann-Frederik ; Tschorsch, Florian (2017)

Payment channel networks use off-chain transactions to provide virtually arbitrary transaction rates. In this paper, we provide a new perspective on payment channels and consider them as a flow network. We propose an extended push-relabel algorithm to find payment flows in a payment channel network. Our algorithm enables a distributed and concurrent execution without violating capacity constrai...

Webchain: Verifiable Citations and References for the World Wide Web

Rohrer, Elias ; Heidel, Steffen ; Tschorsch, Florian (2018)

Readers’ capability to consider and assess sources is imperative. Digital preservation efforts, however, mostly neglected citation provenance, which is a necessity for transparent source verification. We therefore present Webchain, a new system enabling verifiable citations and references on the World Wide Web. Its architecture combines a distributed ledger with secure timestamping to ensure hi...

CircuitStart: A Slow Start For Multi-Hop Anonymity Systems

Döpmann, Christoph ; Tschorsch, Florian (2018)

In order to improve the performance of anonymity networks like Tor, custom transport protocols have been proposed to efficiently deal with the multi-hop nature of such overlay networks. In this work, we tackle the issue of quickly, but safely, ramping up the congestion window during the initial phase of a circuit's lifetime. We propose a tailored startup mechanism called CircuitStart that trans...

P2KMV: A Privacy-preserving Counting Sketch for Efficient and Accurate Set Intersection Cardinality Estimations

Sparka, Hagen ; Tschorsch, Florian ; Scheuermann, Björn (2018-05-01)

In this paper, we propose P2KMV, a novel privacy-preserving counting sketch, based on the k minimum values algorithm. With P2KMV, we offer a versatile privacy-enhanced technology for obtaining statistics, following the principle of data minimization, and aiming for the sweet spot between privacy, accuracy, and computational efficiency. As our main contribution, we develop methods to perform set...

Exploring Deployment Strategies for the Tor Network [Extended Version]

Döpmann, Christoph ; Rust, Sebastian ; Tschorsch, Florian (2018-07-07)

In response to upcoming performance and security challenges of anonymity networks like Tor, it will be of crucial importance to be able to develop and deploy performance improvements and state-of-the-art countermeasures. In this paper, we therefore explore different deployment strategies and review their applicability to the Tor network. In particular, we consider flag day, dual stack, translat...

Crowdsourcing as a guardian of transparency, privacy, and anti-discrimination in a personalized web

Iordanou, Kostas (2019)

The main focus of this thesis is the evaluation of crowdsourcing techniques to measure personalization on the Web. Overall, I apply my methodology in four different aspects on the Web. (1) First, I investigate price discrimination and how personal data can influence online pricing. (2) Then, I turn my attention on targeted web advertisements and investigate how targeted ads can be detected in r...

Innovative Wickeltechnologien für Statorspulen zur Erhöhung des Füllfaktors und Reduzierung der Beanspruchungen im Wickelprozess

Zerbe, Johannes (2019)

In der vorliegenden Arbeit werden mehrere Verfahren zur Herstellung von Statorwicklungen und zur Analyse dieser Prozesse entwickelt und untersucht. Das Nadelwickeln mit unterstützenden Wickelkappen als Modifikation des konventionellen Nadelwickelns ermöglicht höhere Füllfaktoren durch einen veränderten Verfahrweg der Wickelnadel, unterstützt durch speziell angepasste Wickelköpfe. Auf Basis expe...

GaAs-based components for photonic integrated circuits

Arar, Bassem (2019)

Semiconductor lasers based on GaAs/AlGaAs double heterostructures have recently received increasing interest for atomic spectroscopy applications. For example GaAs/AlGaAs double heterostructure laser radiation at the wavelengths of 780 nm and 1064 nm is used for rubidium spectroscopy, and for molecular iodine spectroscopy (at 532 nm using frequency-doubling techniques), respectively. Optical sy...

Efficient data delivery in 5G mobile communication networks

Li, Yilin (2019)

Die ständig zunehmende Verbreitung intelligenter Geräten, die Einführung neuer benutzerorientierter unternehmenskritischer Anwendungen, sowie ein exponentieller Anstieg der Nachfrage und Nutzung mobiler Daten, belasten die bestehenden Mobilfunknetze erheblich. Tatsächlich muss der Mobilfunk der fünften Generation (5G) ein Paradigmenwechsel sein, der sehr hohe Trägerfrequenzen mit großen Bandbre...

A 216–256 GHz fully differential frequency multiplier-by-8 chain with 0 dBm output power

Eissa, Mohamed Hussein ; Malignaggi, Andrea ; Ko, Minsu ; Schmalz, Klaus ; Borngräber, Johannes ; Ulusoy, Ahmet Cagri ; Kissinger, Dietmar (2018-03-05)

This work presents a fully differential wideband and low power 240 GHz multiplier-by-8 chain, manufactured in IHP's 130 nm SiGe:C BiCMOS technology with fT/fmax = 300/500 GHz. A single ended 30 GHz input signal is multiplied by 8 using Gilbert cell-based quadrupler and doubler, and then amplified with a wideband differential 3-stage cascode amplifier. To achieve wide bandwidth and optimize for ...

A Lightweight Multilevel Markup Language for Connecting Software Requirements and Simulations

Pudlitz, Florian ; Vogelsang, Andreas ; Brokhausen, Florian (2019-03-08)

[Context] Simulation is a powerful tool to validate specified requirements especially for complex systems that constantly monitor and react to characteristics of their environment. The simulators for such systems are complex themselves as they simulate multiple actors with multiple interacting functions in a number of different scenarios. To validate requirements in such simulations, the requir...

New TCO for use as transparent front contact in chalcopyrite thin film solar cells

Erfurt, Darja (2019)

In this thesis the applicability of high-mobility indium oxide based transparent conductive oxides (TCOs) as front contact in Cu(In,Ga)(S,Se)2 (CIGS) solar cells and modules was investigated. The unique trade-off between optical and electrical properties promises improved short circuit current densities compared to conventional CIGS device configurations, in particular in CIGS modules. By dopin...

Octave bandwidth S- and C-band GaN-HEMT power amplifiers for future 5G communication

Rautschke, Felix ; May, Stefan ; Drews, Sebastian ; Maaßen, Daniel ; Böck, Georg (2018-06-21)

In this contribution, a design methodology for octave-bandwidth power amplifiers (PA) for 5G communication systems using surface mount dual-flat-no-lead packaged gallium-nitride high-electron-mobility transistor devices is presented. Systematic source- and load-pull simulations have been used to find the optimum impedances across 75% fractional bandwidth for S- (1.9–4.2 GHz) and C-band (3.8–8.4...

Distributed and sparse signal processing

Limmer, Steffen (2019)

The 21st century will be remembered for the ubiquity of data. Data analysis has become an indispensable tool for finding patterns in high-dimensional datasets, and the steep increase in computational power allows us to execute ever more sophisticated algorithms. However, it is not foreseeable that the rise of computational resources alone will evade the curse of dimensionality attached to probl...

GPU power modeling and architectural enhancements for GPU energy efficiency

Lucas, Jan (2019)

Graphics Processing Units (GPUs) can now be found in nearly every PC and smartphone. Initially designed for 3D graphics, they evolved into general purpose accelerators, able to outperform CPUs on many tasks. The architecture of GPUs is optimized for massively parallel applications. This reduces the required control logic but also results in lower performance in applications with irregular contr...

Development and characterisation of a diode laser based tunable high-power MOPA system

Tawfieq, Mahmoud (2019)

The aim of this work is to develop and characterize widely tunable high power diode lasers emitting at 976 nm, to serve in non-linear frequency conversion applications. In particular, to serve as pump sources in infrared upconversion detection systems. This is realized by a master oscillator power amplifier (MOPA) configuration, where the MO provides the wavelength stabilization and tuning, whi...

EffFeu Project: Towards Mission-Guided Application of Drones in Safety and Security Environments

Hrabia, Christopher-Eyk ; Hessler, Axel ; Xu, Yuan ; Seibert, Jacob ; Brehmer, Jan ; Albayrak, Sahin (2019-02-25)

The number of unmanned aerial system (UAS) applications for supporting rescue forces is growing in recent years. Nevertheless, the analysis of sensed information and control of unmanned aerial vehicle (UAV) creates an enormous psychological and emotional load for the involved humans especially in critical and hectic situations. The introduced research project EffFeu (Efficient Operation of Unma...

Strategies and Best Practices for Model-based Systems Engineering Adoption in Embedded Systems Industry

Amorim, Tiago ; Vogelsang, Andreas ; Pudlitz, Florian ; Gersing, Peter ; Philipps, Jan (2019)

[Context] Model-based Systems Engineering (MBSE) advocates the integrated use of models throughout all development phases of a system development life-cycle. It is also often suggested as a solution to cope with the challenges of engineering complex systems. However, MBSE adoption is no trivial task and companies, especially large ones, struggle to achieve it in a timely and effective way. [Goa...