1,720,957 research outputs found
Network Simulations for Non-Terrestrial Networks: Overcoming Deployment Challenges and Advancing System Optimization
No full textNon-Terrestrial Networks (NTNs) including satellites, Unmanned Aerial Vehicles (UAVs), and High Altitude Platforms (HAPS), are increasingly seen as essential for extending coverage and enhancing reliability in modern communication systems, particularly in the context of the growing demand driven by IoT and V2X applications. However, their deployment faces significant technical challenges, such as path loss, atmospheric conditions, and Doppler effects. To address these issues, standardization bodies and academic researchers are actively investigating novel architectures to optimize NTN communications. However, the high costs associated with satellite launches, infrastructure deployment, and large-scale testing make physical experimentation infeasible in most cases. Moreover, real-world tests lack the flexibility to assess a wide range of configurations under controlled conditions. To address these limitations, network simulations have become an essential tool for evaluating NTN performance, testing new protocols, and optimizing system parameters before deployment. This paper presents a novel NS3-based simulation tool that integrates advanced energy and channel models from 3GPP TR 38.811, accounting for diverse environmental settings (dense urban, suburban, rural) and atmospheric effects to ensure accurate SNR computations. The simulator also features a sophisticated mobility model for representing satellite constellations and ground user mobility, including pedestrians, vehicles, and airplanes. A case study is presented, demonstrating the simulator’s application in the development and performance evaluation of an energy-aware satellite handover strategy. This work highlights the critical role of simulation tools in advancing NTN technologies and supporting the development of next-generation communication
standards
Evaluating Performance in Satellite Communication Networks: An NS3-Based Simulation Study
No full textNext-generation communication technologies aim to meet the evolving demands of users, emphasizing seamless access to high-quality services regardless of location or time constraints. However, conventional ground-based networks face limitations in providing Internet connectivity to users on several moving platforms, such as airplanes, ships, and trains, as well as in remote areas where building an extensive terrestrial infrastructure is economically unfeasible. To address these challenges, researchers and standardization organizations, such as the ITU, ETSI, ESA, and 3GPP, are exploring the integration of satellites into communication systems. Satellites are appealing thanks to their unique capabilities in delivering reliable connectivity across diverse geographical regions, independent of environmental factors and events, such as climate or natural disasters. However, a thorough investigation and verification is essential to deal with several aspects and allow testing the developed solutions in controlled environment before integrating them into operational systems. Accurate simulation tools play a crucial role in modeling propagation environments and network dynamics to ensure effective deployment and optimization of satellite communication networks. This paper presents a Network Simulator 3 (NS3)-based simulation tool that encompasses several key functionalities to ensure an accurate modeling of communications in Satellite-Terrestrial Integrated Networks (STIN). Among the offered functionalities, the simulator includes a mo-bility model based on the NORAD Simplified General Perturbations 4 (SGP4) mathematical model to simulate Low Earth Orbit (LEO) satellite movements, mobility models tailored for ground users (pedestrian, vehicles, train, and airplanes), and channel models, based on the 3GPP's Technical Report (TR) 38.811, representing different environments (dense urban, urban, sub-urban, and rural) including atmospheric absorption and clutter effects to provide accurate estimations of signal propagation and Signal-to-Noise Ratio (SNR) calculations. This paper also presents a comprehensive study evaluating the performance in different network settings with a focus on satellite-to-ground SNR and maximum link capacity calculations across Ka- and S-bands, showcasing the effectiveness of using NS3 as a simulation platform to assess performance in LEO satellite networks. By integrating factors such as node positioning, channel modeling, and environmental influences, we offer valuable insights into the design and optimization of satellite communication systems for diverse deployment scenarios, aiming to narrow the gap between simulation and real-world deployment and paving the path for more efficient and resilient satellite communication networks in the future
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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