University of Paderborn

About: University of Paderborn is a education organization based out in Paderborn, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Computer science & Context (language use). The organization has 6684 authors who have published 16929 publications receiving 323154 citations.

Board Size, Board Composition, and Firm Performance: Empirical Evidence from Germany

Abstract: We analyze the effects of supervisory board size and composition on the valuation and performance of all German firms listed in the DAX, MDAX and SDAX over the period 1998-2007 (n=294 companies with 2,382 firm-year-observations). Controlling for a large number of other (potential) determinants of firm performance we estimate the joint as well as the separate influence of board size, union representatives, works council representatives, independent worker representatives, bank representatives and former managing board members on firm performance. Contrary to most available studies we are unable to find a consistent effect of either board size or board composition on firm valuation and performance.

Improved analytical modeling of conductive losses in gapped high-frequency inductors

Abstract: An improved method to predict conductive losses in gapped high frequency inductors is presented and used for parametrization of an equivalent small signal circuit model. The method is based on the superposition of power losses resulting from the well known one-dimensional field calculation and losses due to eddy currents caused by the fringing field of airgaps determined from new analytical 2D-field calculations. Losses due to reactive currents in the windings caused by the self capacitance are also considered An accuracy improvement of at least 50% percent compared to the known methods is proved by measurements.

Performance analysis of dynamic OFDMA systems with inband signaling

Abstract: Within the last decade, the orthogonal frequency- division multiplexing (OFDM) transmission scheme has become part of several standards for wireless systems. Today, OFDM is even a candidate for fourth-generation wireless systems. It is well known that dynamic OFDMA systems potentially increase the spectral efficiency. They exploit diversity effects in time, space, and frequency by assigning system resources periodically to terminals. Informing the terminals about new assignments creates a signaling overhead. Up to now, this overhead has not been taken into account in studies on dynamic orthogonal frequency-division multiplexing access (OFDMA) systems. Yet this is crucial for a realistic notion of the performance achieved by dynamic approaches. In this paper, we close this gap. We introduce two forms of representing the signaling information and discuss how these affect system performance. The study of the signaling impact on the performance is conducted for an exemplary dynamic approach. We find that the throughput behavior of dynamic OFDMA systems is significantly influenced by the signaling overhead. In many situations, neglecting the overhead leads to wrong performance conclusions. Also, the performance difference between dynamic and static schemes is now much more sensible to the specific parameter set of the transmission scenario (e.g., frame length, subcarrier number, etc.). This leads to the proposal of access points which should adapt certain system parameters in order to provide optimal performance.

Mobility in wireless networks

Abstract: This article surveys mobility patterns and mobility models for wirelss networks. Mobility patterns are classified into the following types: pedestrians, vehicles, aerial, dynamic medium, robot, and outer space motion. We present the characteristics of each and shortly mention the specific problems. We shortly present the specifics of cellular networks, mobile ad hoc networks, and sensor networks regarding mobility. Then, we present the most important mobility models from the literature. At last we give a brief discussion about the state of research regarding mobility in wireless networks.