Em telecomunicações é utilizada uma grande variedade de modelos de propagação para prever a intensidade do sinal de recepção num enlace de rádio. Os resultados dos modelos empíricos e dos modelos baseados em simplificações do problema eletromagnético apresentam, em geral, grande discrepância entre si, na análise do fenômeno de propagação. Por exemplo, o modelo de dois raios, que prevê atenuação de enlace com variação de 40 dB/década, na região de campo distante da antena de transmissão, quando colocada a uma certa altura da superfície de um solo condutor perfeito. Já o modelo empírico de Okumura-Hata exibe, para as mesmas condições geométricas, mas para solo de condutividade finita, uma variação da atenuação de enlace de 30 dB/década. Neste trabalho propõe-se uma calibração do modelo de dois raios para aumentar sua aderência aos resultados obtidos por Okumura-Hata num cenário real na faixa de frequências de 450MHz a 1900MHz para comprimentos de enlace entre 1 km e 20 km. Os resultados obtidos com o modelo proposto são comparados com os obtidos através de outros modelos apresentando boa aderência verificada através de uma comparação numérica particularmente com o modelo Okumura-Hata. / In telecommunications, there is a large variety of propagation models in order to predict the intensity of the receiving signal in a communication link. The empirical models and the models based on simplifications of the electromagnetic problem with theoretically obtained results show, in general, a significant disagreement, for the same propagation phenomenon. For example two-ray model predicts a path-loss of 40 dB/decade in the far-field region of a transmission antenna deployed at a certain height of the surface of a perfect conducting soil. On the other hand, the Okumura-Hata empirical model shows, for the same geometrical conditions, bur for a real soil, a path-loss of 30 dB/decade. This work proposes a calibration of the Two-Ray model for better adherence to the results obtained by Okumura-Hata in a real scenario for the frequency range 450MHz to 1900MHz and for a radio link length of 1 km to 20 km. The results obtained with the proposed model are compared with other model results showing good adherence through numeric comparison, in particular with the Okumura - Hata model.

Em telecomunicações é utilizada uma grande variedade de modelos de propagação para prever a intensidade do sinal de recepção num enlace de rádio. Os resultados dos modelos empíricos e dos modelos baseados em simplificações do problema eletromagnético apresentam, em geral, grande discrepância entre si, na análise do fenômeno de propagação. Por exemplo, o modelo de dois raios, que prevê atenuação de enlace com variação de 40 dB/década, na região de campo distante da antena de transmissão, quando colocada a uma certa altura da superfície de um solo condutor perfeito. Já o modelo empírico de Okumura-Hata exibe, para as mesmas condições geométricas, mas para solo de condutividade finita, uma variação da atenuação de enlace de 30 dB/década. Neste trabalho propõe-se uma calibração do modelo de dois raios para aumentar sua aderência aos resultados obtidos por Okumura-Hata num cenário real na faixa de frequências de 450MHz a 1900MHz para comprimentos de enlace entre 1 km e 20 km. Os resultados obtidos com o modelo proposto são comparados com os obtidos através de outros modelos apresentando boa aderência verificada através de uma comparação numérica particularmente com o modelo Okumura-Hata. / In telecommunications, there is a large variety of propagation models in order to predict the intensity of the receiving signal in a communication link. The empirical models and the models based on simplifications of the electromagnetic problem with theoretically obtained results show, in general, a significant disagreement, for the same propagation phenomenon. For example two-ray model predicts a path-loss of 40 dB/decade in the far-field region of a transmission antenna deployed at a certain height of the surface of a perfect conducting soil. On the other hand, the Okumura-Hata empirical model shows, for the same geometrical conditions, bur for a real soil, a path-loss of 30 dB/decade. This work proposes a calibration of the Two-Ray model for better adherence to the results obtained by Okumura-Hata in a real scenario for the frequency range 450MHz to 1900MHz and for a radio link length of 1 km to 20 km. The results obtained with the proposed model are compared with other model results showing good adherence through numeric comparison, in particular with the Okumura - Hata model.

Στην εργασία αυτή γίνεται μια αναφορά αρχικά στα GSM δίκτυα κινητής τηλεφωνίας (χαρακτηριστικά-λειτουργίες). Στη συνέχεια περιγράφεται ο τρόπος υπολογισμού της κυτταρικής ακτίνας με βάση τα μοντέλα Okumura-Hata και Ikegami. Τέλος αναφέρονται παραδείγματα υπολογισμού της ακτίνας των κυττάρων αλλά και διαστασιοποίησης των καναλιών σε αυτά ώστε να εξυπηρετείται συγκεκριμένη τηλεπικοινωνιακή κίνηση. / The purpose of this project is to examine the major steps in cell planning process such as cell coverage, frequency planning and calculations of traffic and channel needs for the given areas.

<p>This Master thesis deals with wave propagation and starts with wave propagation basics. It briefly presents the theory for the diffraction over terrain obstacles and describes two different path loss models, the Hata model and a FFT-based model. The significance of this paper is that it gives the simulation results for the models mentioned above and presents a comparison between the results obtained from an empirical formula and the FFT-model. The comparison shows that the approach based on Fast Fourier Transform is good enough for prediction of the path loss and that it is a time efficient method.</p>

This Master thesis deals with wave propagation and starts with wave propagation basics. It briefly presents the theory for the diffraction over terrain obstacles and describes two different path loss models, the Hata model and a FFT-based model. The significance of this paper is that it gives the simulation results for the models mentioned above and presents a comparison between the results obtained from an empirical formula and the FFT-model. The comparison shows that the approach based on Fast Fourier Transform is good enough for prediction of the path loss and that it is a time efficient method.

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This thesis work examines how people accomplish annotation tasks (i.e., labelling data based on content) while working with an artificial intelligence (AI) system. When people and AI systems work together to accomplish a task, this is referred to as human-AI teaming. This study reports on the results of an interview and observation study of 15 volunteers from the Washington DC area as the volunteers annotated Twitter messages (tweets) about the COVID-19 pandemic. During the interviews, researchers observed the volunteers as they annotated tweets, noting any needs, frustrations, or confusion that the volunteers expressed about the task itself or when working with the AI. This research provides the following contributions: 1) an examination of annotation work in a human-AI teaming context; 2) the HATA (human-AI teaming annotation) framework with five key factors that affect the way people annotate while working with AI systems--background, task interpretation, training, fatigue, and the annotation system; 3) a set of questions that will help guide users of the HATA framework as they create or assess their own human-AI annotation teams; 4) design recommendations that will give future researchers, designers, and developers guidance for how to create a better environment for annotators to work with AI; and 5) HATA framework implications when it is put into practice.

Böckerna som har valts att analyseras är Falafelflickorna (Christina, Wahldén, 2018) och Hata Gustavsberg (Agnes Lindström, 2017) utifrån genusperspektivet. Uppsatsens syfte är att undersöka om det sker normbrott i de valda barnböckerna. Teorin tar upp allmän fakta om genusperspektiv samt presenterar Nikolajevas (2017, s. 193) tabell. Metoden utgår från en kvalitativ och kvantitativ metod under uppsatsens gång. Resultatet visar på att barnlitteraturen i båda böckerna är normbrytande. En tabell med ”manliga” och ”kvinnliga” egenskaper används vid studien, där resultatet visar på att det finns fler ”manliga” än ”kvinnliga” egenskaper i böckerna (Nikolajeva, 2017, s. 193).

Large scale path loss modeling plays a fundamental role in designing both fixed and mobile radio systems. Predicting the radio coverage area of a system is not done in a standard manner. Wireless systems are expensive systems. Therefore, before setting up a system one has to choose a proper method depending on the channel environment, frequency band and the desired radio coverage range. Path loss prediction plays a crucial role in link budget analysis and in the cell coverage prediction of mobile radio systems. Especially in urban areas, increasing numbers of subscribers brings forth the need for more base stations and channels. To obtain high efficiency from the frequency reuse concept in modern cellular systems one has to eliminate the interference at the cell boundaries. Determining the cell size properly is done by using an accurate path loss prediction method. Starting from the radio propagation phenomena and basic path loss models this thesis aims at describing various accurate path loss prediction methods used both in rural and urban environments. The Walfisch-Bertoni and Hata models, which are both used for UHF propagation in urban areas, were chosen for a detailed comparison. The comparison shows that the Walfisch-Bertoni model, which involves more parameters, agrees with the Hata model for the overall path loss.

<p>Large scale path loss modeling plays a fundamental role in designing both fixed and mobile radio systems. Predicting the radio coverage area of a system is not done in a standard manner. Wireless systems are expensive systems. Therefore, before setting up a system one has to choose a proper method depending on the channel environment, frequency band and the desired radio coverage range. Path loss prediction plays a crucial role in link budget analysis and in the cell coverage prediction of mobile radio systems. Especially in urban areas, increasing numbers of subscribers brings forth the need for more base stations and channels. To obtain high efficiency from the frequency reuse concept in modern cellular systems one has to eliminate the interference at the cell boundaries. Determining the cell size properly is done by using an accurate path loss prediction method. Starting from the radio propagation phenomena and basic path loss models this thesis aims at describing various accurate path loss prediction methods used both in rural and urban environments. The Walfisch-Bertoni and Hata models, which are both used for UHF propagation in urban areas, were chosen for a detailed comparison. The comparison shows that the Walfisch-Bertoni model, which involves more parameters, agrees with the Hata model for the overall path loss.</p>