1,721,011 research outputs found
Characterization of the indoor-to-outdoor wireless channel in air-to-ground communication systems
Full text linkWireless communication between User Terminals (UTs) inside a building and an outdoor base station mounted onboard an unmanned aerial vehicle (UAV) is receiving a higher interest in emergency management scenarios and where users require on demand high throughput services. In such applications, a fundamental aspect is the thorough characterization of the propagation environment through parameters such as the UTUAV distance and the number of walls and floors crossed. In this paper, we characterize the indoor-to-outdoor wireless channel by using a commercial ray-tracing software. The reference scenario is a four-floor building. The UTs are uniformly distributed within each floor and two UAV positions are considered nearby the building. As a main contribution, we present numerical results in terms of path loss against the UT-UAV distance. The dependence of the path loss on the number of floors between the UT and the UAV is highlighted as well. Finally, the ray-tracing results are compared with those predicted by a few available propagation models
Performance of Free Space Optical links: a Case Study for Pakistan
No full textA case study for 5G/6G network free space optical (FSO) links affected by fog is reported. Twenty years of visibility data for some major cities of Pakistan were acquired from the Pakistan Meteorological Department. The visibility data consists of three daily measurements collected at 05:00, 08:00, and 17:00 Pakistan standard time (PKT). The data are used to calculate the availability of a 1550 nm FSO link, for each city. Results highlight large differences among the six locations, due to the different climatic conditions. Lahore has the worst performance: in that case, an FSO backhaul link shorter than 150 m would achieve an availability of 99.5%. Whereas, Peshawar has the best performance for the said availability
Predicting Rain Attenuation at D Band for 6G Backhaul Link Design: a Frequency Scaling Approach
No full textA frequency scaling (FS) model is presented for the prediction of rain-induced attenuation affecting a short terrestrial link operating at D band, to be potentially used as backhaul link in future sixth generation (6G) networks. The methodology, which aims at estimating rain attenuation at a target higher frequency from measurements collected at a lower band, requires as input local time series of the rain rate and defines a scaling ratio as a function of the specific attenuations at the two frequencies. Data from a long-term propagation study, conducted in collaboration between Politecnico di Milano and the Huawei Microwave Centre in Milan, are employed to assess the accuracy of the proposed model in scaling rain attenuation from E band (83 GHz) to D band (156 GHz). Results indicate high prediction accuracy. This corroborates the use of the proposed FS model as a tool to fill the current lack of tropospheric impairment data at carrier frequencies not currently licensed but to be potentially employed in the near future in 6G networks
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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