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See detailExploiting orthogonality in DVB-S2X through time pre-compensation
Andrenacci, Stefano UL; Chatzinotas, Symeon UL; Vanelli-Coralli, Alessandro et al

in Proceedings of 2016 8th Advanced Satellite Multimedia Systems Conference and the 14th Signal Processing for Space Communications Workshop (2016)

The superframing option of the recent DVB-S2X standard specifies, for the so-called SF-Pilot fields, the use of the orthogonal set of Walsh-Hadamard (WH) sequences. In order to exploit this orthogonality ... [more ▼]

The superframing option of the recent DVB-S2X standard specifies, for the so-called SF-Pilot fields, the use of the orthogonal set of Walsh-Hadamard (WH) sequences. In order to exploit this orthogonality, waveforms coming from different beams to the k-th User Terminal (UT) should be quasi perfectly aligned in time. While in the downlink part of a terrestrial system this is quite straightforward, in satellite system, having a satellite as a relay, this is not the case, especially when large baudrates are considered in the transmission. A procedure to compensate for timing misalignment amongst waveforms is here presented and the advantages are quantified through numerical simulations.In particular, Channel State Information (CSI) estimation errors, which are fundamental for precoding techniques, are evaluated. While the focus of the work is on systems which enable precoding techniques, the procedure can be applied in each scenario which uses the superframing structure of DVB-S2X in an interference limited scenario. [less ▲]

Detailed reference viewed: 100 (6 UL)
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See detailExploiting polarization for spectrum awareness in cognitive satellite communications
Sharma, S. K.; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Exploiting polarization for spectrum awareness in cognitive satellite communications (2014)

The continuously increasing demand of spectrum and current static spectrum allocation policies are rendering the available radio spectrum scarce. To address the problem of spectrum scarcity in the ... [more ▼]

The continuously increasing demand of spectrum and current static spectrum allocation policies are rendering the available radio spectrum scarce. To address the problem of spectrum scarcity in the satellite paradigm, cognitive satellite communications has been considered as a promising technique. In addition to the existing spectrum sharing dimensions such as frequency, time, and space, polarization can be exploited as an additional degree of freedom in order to explore the spectral gaps in the underutilized licensed spectrum. In this context, this chapter firstly provides an overview of the existing works in polarization-based spectrum sharing. Secondly, it presents the theoretical analysis of energy detection technique for dual polarized Additive White Gaussian Noise and Rayleigh fading channels considering the spectral coexistence scenarios of dual and hybrid satellite systems. Thirdly, it provides the comparison of different combining techniques in terms of the sensing performance. Finally, it provides interesting future research directions in this domain. © 2015 by IGI Global. All rights reserved. [less ▲]

Detailed reference viewed: 141 (0 UL)
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See detailExploiting Polarization for Spectrum Awareness in Cognitive Satellite Communications
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Software-Defined and Cognitive Radio Technologies for Dynamic Spectrum Access and Management (2015)

The continuously increasing demand of spectrum and current static spectrum allocation policies are rendering the available radio spectrum scarce. To address the problem of spectrum scarcity in the ... [more ▼]

The continuously increasing demand of spectrum and current static spectrum allocation policies are rendering the available radio spectrum scarce. To address the problem of spectrum scarcity in the satellite paradigm, cognitive Satellite Communications (SatComs) has been considered as a promising technique. In addition to the existing spectrum sharing dimensions such as frequency, time and space, polarization domain can be exploited as an additional degree of freedom in order to explore the spectral gaps in the under-utilized licensed spectrum. In this context, this chapter firstly provides an overview of the existing works in polarization-based spectrum sharing. Secondly, it presents the theoretical analysis of Energy Detection technique for dual polarized Additive White Gaussian Noise (AWGN) and Rayleigh fading channels considering the spectral coexistence scenarios of dual and hybrid satellite systems. Thirdly, it provides the comparison of different combining techniques in terms of the sensing performance in the considered dual polarized channels with the help of theoretical analysis and numerical results. Finally, it provides interesting future research directions in this domain. [less ▲]

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See detailExploiting Polarization for Spectrum Sensing in Cognitive SatComs
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of 7th International Conference on Cognitive Radio Oriented Wireless Networks (2012, June)

Exploring new techniques for spectrum sensing (SS), which can detect the weak primary signals instantly, has been an important research challenge. In this paper, the problem of enhancing SS efficiency in ... [more ▼]

Exploring new techniques for spectrum sensing (SS), which can detect the weak primary signals instantly, has been an important research challenge. In this paper, the problem of enhancing SS efficiency in cognitive SatComs has been considered. The analysis of different combining techniques has been carried out for SS using dual polarized antenna. Furthermore, polarization states of received signals are exploited and based on obtained polarization states, Optimum Polarization Based Combining (OPBC) technique has been used for carrying out SS in the satellite terminal. The sensing performance of OPBC technique has been compared to selection combining (SC), equal gain combining (EGC) and maximum ratio combining (MRC) techniques. The simulation results show that OPBC technique achieves a great improvement in sensing efficiency over other considered techniques at the expense of complexity in a dual polarized AWGN channel. [less ▲]

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See detailExploiting Quantized Channel Norm Feedback Through Conditional Statistics in Arbitrarily Correlated MIMO Systems
Björnson, Emil; Hammarwall, David; Ottersten, Björn UL

in IEEE Transactions on Signal Processing (2009), 57(10), 4027-4041

In the design of narrowband multi-antenna systems, a limiting factor is the amount of channel state information (CSI) available at the transmitter. This is especially evident in multi-user systems, where ... [more ▼]

In the design of narrowband multi-antenna systems, a limiting factor is the amount of channel state information (CSI) available at the transmitter. This is especially evident in multi-user systems, where the spatial user separability determines the multiplexing gain, but it is also important for transmission-rate adaptation in single-user systems. To limit the feedback load, the unknown and multi-dimensional channel needs to be represented by a limited number of bits. When combined with long-term channel statistics, the norm of the channel matrix has been shown to provide substantial CSI that permits efficient user selection, linear precoder design, and rate adaptation. Herein, we consider quantized feedback of the squared Frobenius norm in a Rayleigh fading environment with arbitrary spatial correlation. The conditional channel statistics are characterized and their moments are derived for both identical, distinct, and sets of repeated eigenvalues. These results are applied for minimum mean square error (MMSE) estimation of signal and interference powers in single- and multi-user systems, for the purpose of reliable rate adaptation and resource allocation. The problem of efficient feedback quantization is discussed and an entropy-maximizing framework is developed where the post-user-selection distribution can be taken into account in the design of the quantization levels. The analytic results of this paper are directly applicable in many widely used communication techniques, such as space-time block codes, linear precoding, space division multiple access (SDMA), and scheduling. [less ▲]

Detailed reference viewed: 133 (0 UL)
See detailExploiting Resource Heterogeneity in DTN
Sandulescu, Gabriel UL; Schaffer, Peter UL; Nadjm-Tehrani, Simin UL

in Wireless Communications & Mobile Computing (2012), 13(3), 230-243

Detailed reference viewed: 53 (2 UL)
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See detailExploiting the Hard-wired Vulnerabilities of Newscast via Connectivity-splitting Attack
Muszynski, Jakub UL; Varrette, Sébastien UL; Jimenez Laredo, Juan Luis UL et al

in Proc. of the IEEE Intl. Conf. on Network and System Security (NSS 2014) (2014, October)

Newscast is a model for information dissemination and mem- bership management in large-scale, agent-based distributed systems. It deploys a simple, peer-to-peer data exchange protocol. The Newscast pro ... [more ▼]

Newscast is a model for information dissemination and mem- bership management in large-scale, agent-based distributed systems. It deploys a simple, peer-to-peer data exchange protocol. The Newscast pro- tocol forms an overlay network and keeps it connected by means of an epidemic algorithm, thus featuring a complex, spatially structured, and dynamically changing environment. It has recently become very popu- lar due to its inherent resilience to node volatility as it exhibits strong self-healing properties. In this paper, we analyze the robustness of the Newscast model when executed in a distributed environment subjected to malicious acts. More precisely, we evaluate the resilience of Newscast against cheating faults and demonstrate that even a few naive cheaters are able to defeat the protocol by breaking the network connectivity. Concrete experiments are performed using a framework that implements both the protocol and the cheating model considered in this work. [less ▲]

Detailed reference viewed: 120 (11 UL)
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See detailExploiting the Potential of Process Data in Complex Problem Solving Assessment
Greiff, Samuel UL; Müller, Jonas UL

Scientific Conference (2014, March)

Detailed reference viewed: 55 (3 UL)
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See detailExploiting Transistor-Level Reconfiguration to Optimize Combinational Circuits on the Example of a Conditional Sum Adder
Raitza, Michael; Kumar, Akash; Volp, Marcus UL et al

Scientific Conference (2017, March)

Silicon nanowire reconfigurable field effect transistors (SiNW RFETs) abolish the physical separation of n-type and p-type transistors by taking up both roles in a configurable way within a doping-free ... [more ▼]

Silicon nanowire reconfigurable field effect transistors (SiNW RFETs) abolish the physical separation of n-type and p-type transistors by taking up both roles in a configurable way within a doping-free technology. However, the potential of transistor-level reconfigurability has not been demonstrated in larger circuits, so far. In this paper, we present first steps to a new compact and efficient design of combinational circuits by employing transistor-level reconfiguration. We contribute new basic gates realized with silicon nanowires, such as 2/3-XOR and MUX gates. Exemplifying our approach with 4-bit, 8-bit and 16-bit conditional carry adders, we were able to reduce the number of transistors to almost one half. With our current case study we show that SiNW technology can reduce the required chip area by 16 %, despite larger size of the individual transistor, and improve circuit speed by 26 %. [less ▲]

Detailed reference viewed: 247 (10 UL)
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See detailExploration du territoire et déambulation de la mémoire. Constructions d’identités dans l’œuvre d’Anne-Lise Grobéty
Barthelmebs-Raguin, Hélène UL

in CRIN : Cahiers de Recherches des Instituts Néerlandais de Langue et Littérature Françaises (2016)

Detailed reference viewed: 24 (0 UL)
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See detailExploration of Different School Value-Added Models in a Highly Heterogeneous Educational Context
Levy, Jessica UL; Brunner, Martin; Keller, Ulrich UL et al

Scientific Conference (2019, April)

Detailed reference viewed: 88 (14 UL)
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See detailAn explorative interview study on crisis situations in engineering product development
Münzberg, Christopher; Gericke, Kilian UL; Oehmen, Josef et al

in Marjanovic, Dorian (Ed.) Proceedings of the International Design Conference - DESIGN'16 (2016)

This paper presents the result of an interview study with 15 experts on crises in industrial product development practice. The paper focusses on two research questions. 1. How can crises in product ... [more ▼]

This paper presents the result of an interview study with 15 experts on crises in industrial product development practice. The paper focusses on two research questions. 1. How can crises in product development be characterised? 2. What are success factors for effective crisis solving in product development? The paper contributes 9 context factors to discern crises from regular development situations, 56 success factors for crisis resolution, and describes three example crises. [less ▲]

Detailed reference viewed: 69 (2 UL)
See detailExploratorische Faktorenanalyse
Krolak-Schwerdt, Sabine UL; Spinath, Frank

in Holling, H.; B.Schmitz (Eds.) Handbuch Statistik, Methoden und Evaluation (Handbuch der Psychologie, Bd. 13) (2010)

Detailed reference viewed: 43 (1 UL)
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See detailExploratory Case Studies
Streb, Christoph Klaus UL

in Mills, A.J.; Durepos, G; Wiebe, E (Eds.) Encyclopedia of Case Study Research (2010)

Detailed reference viewed: 642 (0 UL)
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See detailAn exploratory study of the discovery and selection of design methods in practice
Gericke, Kilian UL; Kramer, Julia; Roschuni, Celeste

in Journal of Mechanical Design (2016), 138

This work seeks to understand how design practitioners discover, select, and adapt design methods and methodologies. Design methods and methodologies are mainly used for educational purposes and are not ... [more ▼]

This work seeks to understand how design practitioners discover, select, and adapt design methods and methodologies. Design methods and methodologies are mainly used for educational purposes and are not formally transferred into design practice and industry. This prevents design practitioners from accessing the rich body of research and knowledge posed by academia. Various web platforms and textbooks allow users to discover or search for design methods, but little support is provided to assess whether or not a method is appropriate for the context or the task at hand. In this exploratory study, interviews were conducted with practicing engineers and designers. Interview responses were coded and analyzed in an effort to understand the patterns in searching, selecting, assessing and exchanging experiences with peers in professional practice. This analysis showed that interviewees would like to search for design methods based on their desired outcomes. Additionally, interviewees considered their personal contacts to be the most valuable source of new methods. These insights show that web-based communities of practice may be a potential link between academia and industry, but existing web repositories and communities require further development in order to better meet the needs of the design practitioner community. [less ▲]

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See detailAn exploratory study on the use of new design methods in design consultancies
Filippi, Anna; Suarez Madrigal, Antonio; Eisenbart, Boris et al

in Proceedings of the International Design Conference - DESIGN 2018 (2018, May)

This paper explores the uptake of design methods in design consultancies. Our results show that new methods are primarily used in the initial phases of the design process for specific problems. The main ... [more ▼]

This paper explores the uptake of design methods in design consultancies. Our results show that new methods are primarily used in the initial phases of the design process for specific problems. The main motive for doing so is to enhance creativity and understanding of the user. Many participants modify methods to fit specific needs or develop own methods. These findings highlight the need to improve the link between industry and academia in order to increase method awareness and use. Potential ways to improve this include better descriptions of methods and the be­nefits provided. [less ▲]

Detailed reference viewed: 109 (0 UL)
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See detailExplorer la ville polycentrique avec un modèle multi-agents
Lemoy, Rémi UL; Raux, Charles; Jensen, Pablo

in Hégron, G.; Prévost, T. (Eds.) La modélisation de la ville : de la représentation au projet (2012)

Detailed reference viewed: 28 (0 UL)