Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Peer Reviewed
See detailSwitzerland and the Netherlands in the 18th Century. The Republican Discourse of Public Virtues
Tröhler, Daniel UL

in De achttiende eeuw : Documentatieblad van de Werkgroep Achttiende Eeuw (2006), 37(1), 90-104

Detailed reference viewed: 43 (0 UL)
Peer Reviewed
See detailSword, Shield and Cloud: Toward a European System of Public-Private Orders for Electronic Evidence in Criminal Matters?
Ligeti, Katalin UL; Robinson, Gavin UL

in Mitsilegas, Valsamis; Vavoula, Niovi (Eds.) Surveillance and Privacy in the Digital Age: European, Transatlantic and Global Perspectives (in press)

Detailed reference viewed: 74 (2 UL)
See detailSWR 1000 integral and full scale tests of the passive safety systems
Leyer, Stephan UL; Wich, M.; Schafer, H.

in International Conference on Advances in Nuclear Power Plants, ICAPP 2008 (2008), 1

The SWR 1000 is an innovative boiling water reactor concept with passive safety systems. In order to verify the functionality of the passive components required for the transient and accident management ... [more ▼]

The SWR 1000 is an innovative boiling water reactor concept with passive safety systems. In order to verify the functionality of the passive components required for the transient and accident management, the test facility INKA (Integral-Versuchstand Karlstein) is build up in Karlstein (Germany). The INKA test facility is designed to test the full scaled Emergency and Containment Cooling Condenser under steady state conditions as well as to simulate different postulated SWR 1000 transients and Loss of Coolant Accidents in a down scaled setup. The goal of the experiments is to obtain the power characteristics of the components and to demonstrate the ability of the passive safety systems to transfer the plant into a safe and stable state in case of a transient or LOCA. In this paper the INKA test facility setup including the tested components and the vessels, simulating the SWR 1000 containment will be described. [less ▲]

Detailed reference viewed: 55 (0 UL)
See detailSWR 1000. Integral and full-scale testing of the passive safety systems
Leyer, Stephan UL; Wich, Michael; Schaefer, Heinrich

in Annual meeting on nuclear technology 2008. Proceedings (2008)

Detailed reference viewed: 31 (0 UL)
Full Text
Peer Reviewed
See detailSylvie Germain, éblouie par la peinture
Roelens, Nathalie UL

in Cahiers de recherche des instituts néerlandais de langue et de littérature française (2011), 56

Detailed reference viewed: 64 (2 UL)
Full Text
Peer Reviewed
See detailSymbiont transmission entails the risk of parasite infection
Salem, Hassan; Onchuru, Thomas; Bauer, Eugen UL et al

in Biology Letters (2015)

Detailed reference viewed: 136 (1 UL)
Full Text
Peer Reviewed
See detailSymbiose aus Stahl und Stein
Schäfer, Markus UL; Radermacher, Christoph; Braun, Matthias et al

in Stahlbau (2016), Stahlbau 85(Heft 10), 659-669

The real estate project KONS encountered a two and a half year process of demolition of an existing building and construction of a new building complex in a central, urban location of Luxembourg City ... [more ▼]

The real estate project KONS encountered a two and a half year process of demolition of an existing building and construction of a new building complex in a central, urban location of Luxembourg City opposite of the main railway station. Thereby the ambitious specifications of the investor as well as the requirements of the local authorities could be met only through a comprehensive and intelligent planning process. The complex interrelation between logistics and construction management processes, detailing and overall economic assessment found the solution of steel-composite design highly performant and efficient in every aspect. [less ▲]

Detailed reference viewed: 50 (12 UL)
Full Text
See detailSymbiose aus Stahl und Stein - innovative Lösungen
Schäfer, Markus UL; Braun, Matthias; Radermacher, Christoph et al

in Revue Technique Luxembourgeoise (2016), 04/2016

Detailed reference viewed: 37 (2 UL)
Full Text
Peer Reviewed
See detailSymbiose von Kryptographie und digitalen Wasserzeichen: effizienter Schutz des Urheberrechtes digitaler Medien
Kutter, Martin; Leprévost, Franck UL

in Tagungsband des 6. Deutschen IT-Sicherheitskongresses des BSI (1999)

Detailed reference viewed: 48 (0 UL)
Full Text
Peer Reviewed
See detailSymbol Based Precoding in the Downlink of Cognitive MISO Channel
Alodeh, Maha UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of CROWNCOM 2015 (2015, April)

This paper proposes symbol level precoding in the downlink of a MISO cognitive system. The new scheme tries to jointly utilize the data and channel information to design a precoding that minimizes the ... [more ▼]

This paper proposes symbol level precoding in the downlink of a MISO cognitive system. The new scheme tries to jointly utilize the data and channel information to design a precoding that minimizes the transmit power at a cognitive base station (CBS); without violating the interference temperature constraint imposed by the primary system. In this framework, the data information is handled at symbol level which enables the characterization the intra-user interference among the cog- nitive users as an additional source of useful energy that should be ex- ploited. A relation between the constructive multiuser transmissions and physical-layer multicast system is established. Extensive simulations are performed to validate the proposed technique and compare it with con- ventional techniques [less ▲]

Detailed reference viewed: 210 (14 UL)
See detailSymbol calculus and applications I
Poncin, Norbert UL

Presentation (2004)

Detailed reference viewed: 39 (1 UL)
See detailSymbol calculus and applications II
Poncin, Norbert UL

Presentation (2004)

Detailed reference viewed: 33 (0 UL)
Full Text
See detailSYMBOL LEVEL PRECODING TECHNIQUES FOR HARDWARE AND POWER EFFICIENT WIRELESS TRANSCEIVERS
Domouchtsidis, Stavros UL

Doctoral thesis (2020)

Large-scale antennas are crucial for next generation wireless communication systems as they improve spectral efficiency, reliability and coverage compared to the traditional ones that are employing ... [more ▼]

Large-scale antennas are crucial for next generation wireless communication systems as they improve spectral efficiency, reliability and coverage compared to the traditional ones that are employing antenna arrays of few elements. However, the large number of antenna elements leads to a big increase in power consumption of conventional fully digital transceivers due to the one Radio Frequency (RF) chain / per antenna element requirement. The RF chains include a number of different components among which are the Digital-to-Analog Converters (DACs)/Analog-to-Digital Converters (ADCs) that their power consumption increases exponential with the resolution they support. Motivated by this, in this thesis, a number of different architectures are proposed with the view to reduce the power consumption and the hardware complexity of the transceiver. In order to optimize the transmission of data through them, corresponding symbol level precoding (SLP) techniques were developed for the proposed architectures. SLP is a technique that mitigates multi-user interference (MUI) by designing the transmitted signals using the Channel State Information and the information-bearing symbols. The cases of both frequency flat and frequency selective channels were considered. First, three different power efficient transmitter designs for transmission over frequency flat channels and their respective SLP schemes are considered. The considered systems tackle the high hardware complexity and power consumption of existing SLP techniques by reducing or completely eliminating fully digital RF chains. The precoding design is formulated as a constrained least squares problem and efficient algorithmic solutions are developed via the Coordinate Descent method. Next, the case of frequency selective channels is considered. To this end, Constant Envelope precoding in a Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing system (CE MIMO-OFDM) is considered. In CE MIMO-OFDM the transmitted signals for each antenna are designed to have constant amplitude regardless of the channel realization and the information symbols that must be conveyed to the users. This facilitates the use of power-efficient components, such as phase shifters and non-linear power amplifiers. The precoding problem is firstly formulated as a least-squares problem with a unit-modulus constraint and solved using an algorithm based on the coordinate descent (CCD) optimization framework and then, after reformulating the problem into an unconstrained non-linear least squares problem, a more computationally efficient solution using the Gauss-Newton algorithm is presented. Then, CE MIMO-OFDM is considered for a system with low resolution DACs. The precoding design problem is formulated as a mixed discrete- continuous least-squares optimization one which is NP-hard. An efficient low complexity solution is developed based also on the CCD optimization framework. Finally, a precoding scheme is presented for OFDM transmission in MIMO systems based on one-bit DACs and ADCs at the transmitter’s and the receiver’s end, respectively, as a way to reduce the total power consumption. The objective of the precoding design is to mitigate the effects of one-bit quantization and the problem is formulated and then is split into two NP hard least squares optimization problems. Algorithmic solutions are developed for the solution of the latter problems, based on the CCD framework. [less ▲]

Detailed reference viewed: 53 (8 UL)
Full Text
See detailA Symbol of History
Danescu, Elena UL

E-print/Working paper (2019)

As the fifth sovereign of the national dynasty since 1890, Grand Duke Jean was a head of state who perfectly embodied the ideals of service to his country and commitment to European integration.

Detailed reference viewed: 28 (1 UL)
See detailSymbol vs Block Level Precoding in Multi-beam Satellite Systems
Kayhan, Farbod UL; Haqiqatnejad, Alireza UL; Grotz, Joel et al

in Symbol vs Block Level Precoding in Multi-beam Satellite Systems (2018)

Precoding techniques for multi-beam satellite systems have received a considerable attention in recent years as a tool to mitigate the interference among the beams, and hence increasing the throughput ... [more ▼]

Precoding techniques for multi-beam satellite systems have received a considerable attention in recent years as a tool to mitigate the interference among the beams, and hence increasing the throughput. Our goal is to compare two main categories of precoding schemes, namely, the conventional linear block level precoding and the symbol level precoding. Focusing on power minimization problem with signal to interference plus noise ratio (SINR) constraints, symbol level precoding (SLP) has significant gains with respect to the zero forcing (ZF). However, the lower transmit power is achieved with a price: A higher computational complexity. Therefore, several sub-optimal SLP techniques have been proposed in the literature to overcome the complexity. While ZF has the lowest complexity among the techniques chosen in this paper, it is not an optimal linear block level precoder as far as power minimization is concerned. Therefore, in order to have a more complete picture, one needs also to consider optimal block level precoders. Our results indicate that in order to have a fair comparison, one needs to consider two different scenarios, namely, low and high SINR threshold regimes. While for low SINRs the optimal linear block level precoding scheme may provide a good solution with reasonable complexity, for high SINR threshold, the SLP techniques become more attractive. Our results also indicate that the performance of SLP highly depends on the chosen constellation space, and therefore a final conclusion can be achieved only after appropriately optimizing the constellation set. [less ▲]

Detailed reference viewed: 114 (24 UL)
Full Text
Peer Reviewed
See detailSymbol-level and Multicast Precoding for Multiuser Multiantenna Downlink: A State-of-the-art, Classification and Challenges
Alodeh, Maha; Spano, Danilo UL; Kalantari, Ashkan et al

in IEEE Communications Surveys and Tutorials (2018)

Precoding has been conventionally considered as an effective means of mitigating or exploiting the interference in the multiantenna downlink channel, where multiple users are simultaneously served with ... [more ▼]

Precoding has been conventionally considered as an effective means of mitigating or exploiting the interference in the multiantenna downlink channel, where multiple users are simultaneously served with independent information over the same channel resources. The early works in this area were focused on transmitting an individual information stream to each user by constructing weighted linear combinations of symbol blocks (codewords). However, more recent works have moved beyond this traditional view by: i) transmitting distinct data streams to groups of users and ii) applying precoding on a symbol-per-symbol basis. In this context, the current survey presents a unified view and classification of precoding techniques with respect to two main axes: i) the switching rate of the precoding weights, leading to the classes of block-level and symbol-level precoding, ii) the number of users that each stream is addressed to, hence unicast, multicast, and broadcast precoding. Furthermore, the classified techniques are compared through representative numerical results to demonstrate their relative performance and uncover fundamental insights. Finally, a list of open theoretical problems and practical challenges are presented to inspire further research in this area. [less ▲]

Detailed reference viewed: 191 (22 UL)
Full Text
Peer Reviewed
See detailSymbol-Level Multiuser MISO Precoding for Multi-level Adaptive Modulation
Alodeh, Maha UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in IEEE Transactions on Wireless Communications (2017)

Symbol-level precoding is a new paradigm for multiuser multiple-antenna downlink systems which aims at creating constructive interference among the transmitted data streams. This can be enabled by ... [more ▼]

Symbol-level precoding is a new paradigm for multiuser multiple-antenna downlink systems which aims at creating constructive interference among the transmitted data streams. This can be enabled by designing the precoded signal of the multiantenna transmitter on a symbol level, taking into account both channel state information and data symbols. Previous literature has studied this paradigm for Mary phase shift keying (MPSK) modulations by addressing various performance metrics, such as power minimization and maximization of the minimum rate. In this paper, we extend this to generic multi-level modulations i.e. Mary quadrature amplitude modulation (MQAM) by establishing connection to PHY layer multicasting with phase constraints. Furthermore, we address adaptive modulation schemes which are crucial in enabling the throughput scaling of symbol-level precoded systems. In this direction, we design signal processing algorithms for minimizing the required power under per-user signal to interference noise ratio (SINR) or goodput constraints. Extensive numerical results show that the proposed algorithm provides considerable power and energy efficiency gains, while adapting the employed modulation scheme to match the requested data rate. [less ▲]

Detailed reference viewed: 198 (16 UL)
Full Text
Peer Reviewed
See detailSymbol-Level Precoding Design Based on Distance Preserving Constructive Interference Regions
Haqiqatnejad, Alireza UL; Kayhan, Farbod UL; Ottersten, Björn UL

in IEEE Transactions on Signal Processing (2018), 66(22), 5817-5832

In this paper, we investigate the symbol-level precoding (SLP) design problem in the downlink of a multiuser multiple-input single-output (MISO) channel. We consider generic two-dimensional constellations ... [more ▼]

In this paper, we investigate the symbol-level precoding (SLP) design problem in the downlink of a multiuser multiple-input single-output (MISO) channel. We consider generic two-dimensional constellations with any shape and size, and confine ourselves to one of the main categories of constructive interference regions (CIR), namely, distance preserving CIR (DPCIR). We provide a comprehensive study of DPCIRs and derive several properties for these regions. Using these properties, we first show that any signal in a given DPCIR has a norm greater than or equal to the norm of the corresponding constellation point if and only if the convex hull of the constellation contains the origin. It is followed by proving that the power of the noise-free received signal in a DPCIR is a monotonic strictly increasing function of two parameters relating to the infinite Voronoi edges. Using the convex description of DPCIRs and their characteristics, we formulate two design problems, namely, the SLP power minimization with signal-to-interference-plus-noise ratio (SINR) constraints, and the SLP SINR balancing problem under max-min fairness criterion. The SLP power minimization based on DPCIRs can straightforwardly be written as a quadratic programming (QP). We derive a simplified reformulation of this problem which is less computationally complex. The SLP max-min SINR, however, is non-convex in its original form, and hence difficult to tackle. We propose alternative optimization approaches, including semidefinite programming (SDP) formulation and block coordinate descent (BCD) optimization. We discuss and evaluate the loss due to the proposed alternative methods through extensive simulation results. [less ▲]

Detailed reference viewed: 155 (31 UL)
Full Text
Peer Reviewed
See detailSymbol-Level Precoding Design for Max-Min SINR in Multiuser MISO Broadcast Channels
Haqiqatnejad, Alireza UL; Kayhan, Farbod UL; Ottersten, Björn UL

in International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Kalamata 25-28 June 2018 (2018, August 27)

In this paper, we address the symbol level precoding (SLP) design problem under max-min SINR criterion in the downlink of multiuser multiple-input single-output (MISO) channels. First, we show that the ... [more ▼]

In this paper, we address the symbol level precoding (SLP) design problem under max-min SINR criterion in the downlink of multiuser multiple-input single-output (MISO) channels. First, we show that the distance preserving constructive interference regions (DPCIR) are always polyhedral angles (shifted pointed cones) for any given constellation point with unbounded decision region. Then we prove that any signal in a given unbounded DPCIR has a norm larger than the norm of the corresponding vertex if and only if the convex hull of the constellation contains the origin. Using these properties, we show that the power of the noiseless received signal lying on an unbounded DPCIR is an strictly increasing function of two parameters. This allows us to reformulate the originally non-convex SLP max-min SINR as a convex optimization problem. We discuss the loss due to our proposed convex reformulation and provide some simulation results. [less ▲]

Detailed reference viewed: 114 (21 UL)