Vienna University of Technology

About: Vienna University of Technology is a education organization based out in Vienna, Austria. It is known for research contribution in the topics: Laser & Cloud computing. The organization has 16723 authors who have published 49341 publications receiving 1302168 citations.

GPT2: Empirical slant delay model for radio space geodetic techniques.

Abstract: Up to now, state-of-the-art empirical slant delay modeling for processing observations from radio space geodetic techniques has been provided by a combination of two empirical models. These are GPT (Global Pressure and Temperature) and GMF (Global Mapping Function), both operating on the basis of long-term averages of surface values from numerical weather models. Weaknesses in GPT/GMF, specifically their limited spatial and temporal variability, are largely eradicated by a new, combined model GPT2, which provides pressure, temperature, lapse rate, water vapor pressure, and mapping function coefficients at any site, resting upon a global 5° grid of mean values, annual, and semi-annual variations in all parameters. Built on ERA-Interim data, GPT2 brings forth improved empirical slant delays for geophysical studies. Compared to GPT/GMF, GPT2 yields a 40% reduction of annual and semi-annual amplitude differences in station heights with respect to a solution based on instantaneous local pressure values and the Vienna mapping functions 1, as shown with a series of global VLBI (Very Long Baseline Interferometry) solutions.

Nonorthogonal pulseshapes for multicarrier communications in doubly dispersive channels

Abstract: A new approach to multicarrier digital communication over time-varying, frequency selective fading channels is presented. We propose a transmission signal set whose basic structure is similar to standard orthogonal frequency division multiple access (OFDM)-setups, i.e., a system of functions generated by time and frequency-shifted versions of a pulse-like prototype function known as a Weyl-Heisenberg (WH) system. Unlike previous OFDM studies, however, which are restricted to the case of orthonormal pulses, we consider nonorthogonal pulses that are adapted to realistically available a priori knowledge of the channel. Perfect transmultiplexing in the case of an ideal channel is incorporated as a mathematical side-constraint. We derive the expected intersymbol/interchannel interference of such a nonorthogonal FDM (NOFDM) system under the assumption of a wide-sense stationary uncorrelated scattering (WSSUS) channel. Based on this result, we compare OFDM and NOFDM schemes with regard to robustness against delay/Doppler spread.

First steps towards handheld augmented reality

Abstract: In this paper we describe the first stand-alone AugmentedReality (AR) system with self-tracking running on anunmodified personal digital assistant (PDA) with acommercial camera. The project exploits the readyavailability of consumer devices with a minimal need forinfrastructure. The application provides the user with athree-dimensional augmented view of the environment.Our system achieves good overlay registration accuracyby using a popular marker-based tracking toolkit(ARToolKit), which runs directly on the PDA. Weintroduce an optional client/server architecture that isbased on wireless networking and is able to dynamicallyand transparently offload the tracking task in order toprovide better performance in select areas. Thehardware/software framework is modular and can beeasily combined with many elements of an existing ARframework. As a demonstration of the effectiveness, wepresent a 3D navigation application that guides a userthrough an unknown building to a chosen location.