1,721,007 research outputs found
Ray Tracing Simulation of the Radio Channel Time and Angle-Dispersion in Large Indoor Environments
No full textIn the present work a 3D Ray Tracing model is
used to predict the wideband characteristics of the radio
channel in a large indoor environment. A detailed analysis is
carried out to show not only the wideband prediction accuracy
potential of ray tracing, but also how the potential can be
reached. In particular the description of the environment,
which should include the surrounding buildings, and other
computation parameters have a significant impact on the
reliability of the simulation results
RAY TRACING PATH LOSS PREDICTION IN URBAN ENVIRONMENT @ 26, 28 AND 38 GHZ
No full textA ray tracing prediction tool with advanced implementations such as diffuse scattering and vegetation attenuation, is validated vs. mm-Wave frequencies measurements in urban environment at 26GHz and 38GHz. This is one of the first investigations at these frequencies in outdoor scenario. Simulations are compared with measurements in terms of path loss in two different urban scenarios. Results show that the contribution from non-specular components in non-line-of-sight conditions is determinant to achieve a good prediction accuracy at these frequencies and that the excess loss due to vegetation cannot be neglected. To sum up, the prediction accuracy is good and simulations are generally able to track the measurements behavior
E.M. Characterization of Common Construction Materials Using the Fabry-Pérot resonance method
No full textSeveral frequency bands above 6 GHz are being proposed for next generation wireless systems, and the electromagnetic characteristics of many common construction materials at these frequencies still need to be determined. The knowledge of such characteristics is particularly relevant, especially in relation to the increasing use of deterministic propagation models for radio-channel characterization in 5G and beyond systems. In this study, an assessment of the method based on Fabry-Pérot resonance for the evaluation of the complex permittivity of construction materials is presented. The method is shown to be effective in several cases using a relatively simple VNA-based measurement setup and procedure. We also present a comparison between VNA results and measurements performed with a spectrum compact analyzer. The aim is to show that it is possible to perform evaluation of electromagnetic characteristics of materials with a portable, handy and easy-to-use kit, leading to carry out on-site evaluation, without the necessity to acquire a sample of the material and to perform ad-hoc measurements in anechoic room
Studying the Multi-Dispersive Characteristics of the Radio Channel - a Story of Collaboration and Friendship with Pertti Vainikainen
No full textThis paper summarizes the research work on the study and deterministic modelling of multi-dispersive urban radio propagation, we had the great privilege to carry out in collaboration with Professor Pertti Vainikainen. The story of the collaboration is depicted in the introduction, while the major achievements of the work are shortly described in the following sections
Ray-Launching Narrowband Analysis of UAV-to-Ground Propagation in Urban Environment
No full textUnmanned Aerial Vehicles (UAV) enabled communications are emerging as a promising solution for the next-generation wireless systems, e.g. to extend coverage and capacity of 5G mobile radio networks. In this paper the narrowband properties of air-to-ground propagation in UAV-aided communication systems are investigated by means of fast ray launching simulations carried out in a dense urban reference environment
Ray tracing propagation modeling for future small-cell and indoor applications: a review of current techniques
Full text linkApplied for the first time to mobile radio propagation modeling at the beginning of the nineties, ray tracing is now living a second youth. It is probably the best model to assist in the design and planning of future short range, mm-wave wireless systems, where the more limited propagation environment with respect to UHF frequencies, allows to overcome traditional high-CPU time limitations while the higher operating frequency makes ray-optics approximations less drastic and allows to achieve an unprecedented level of accuracy. An overview of ray tracing propagation modeling is given in this paper, with a special attention to future prospects and applications. In particular, frontiers of ray-based propagation modeling such as extension to diffuse scattering, multidimensional channel characterization, MIMO capacity assessments and future applications such as real-time ray tracing are addressed in the paper with reference to the work recently carried out at the University of Bologna
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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