1,720,992 research outputs found
Performance evaluation of in-building DAS for high data rate wireless transmission
No full textIn wireless systems, providing high data rate services is a major challenge, particularly for mobile terminals (MTs) in multi-floor buildings. The system performance is impaired by path loss, and co-channel interference due to the need to reuse the limited available spectrum. One way to achieve high data rates and better signal quality in this environment is by getting the transmitter and the receiver closer to each other through the use of distributed antenna systems (DASs). DAS reduces the overall transmit power (and hence co-channel interference) and achieves better link reliability by exploiting spatial diversity of multiple antennas. Currently, DASs are designed primarily to provide good coverage in outdoor environments. However, high quality indoor reception and high data rates may not be guaranteed if the system is not deployed within the building. Indoor environments can be very complex, and an insight into the design, and a thorough understanding of the performance of DASs inside the building is required. In this thesis, the performance of an in-building DAS employing frequency reuse is examined, where remote antenna units (RAUs) are deployed on each floor throughout the building and connected to a central unit (CU) where received signals are processea. The impact of co-channel interference on system performance is investigated by using a propagation channel model derived from multi-floor in-building path loss values retrieved from measurement results. System performance is investigated in terms of location-specific spectral efficiency and bit error rate (BER) which are analysed for a range of potential MT locations and various in-building propagation characteristics. The potential benefits of location based antenna selection and deployment options are also investigated. Co-channel interference cancellation where CUs cooperate through joint signal pro- cessing in order to reduce the impact of co-channel interference is considered. Results obtained suggest that the proposed scheme can facilitate better use of the available radio spectrum, and provide high data rates for indoor MTs.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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
Performance evaluation of in-building DAS for high data rate wireless transmission
Full text linkIn wireless systems, providing high data rate services is a major challenge, particularly for mobile terminals (MTs) in multi-floor buildings. The system performance is impaired by path loss, and co-channel interference due to the need to reuse the limited available spectrum. One way to achieve high data rates and better signal quality in this environment is by getting the transmitter and the receiver closer to each other through the use of distributed antenna systems (DASs). DAS reduces the overall transmit power (and hence co-channel interference) and achieves better link reliability by exploiting spatial diversity of multiple antennas. Currently, DASs are designed primarily to provide good coverage in outdoor environments. However, high quality indoor reception and high data rates may not be guaranteed if the system is not deployed within the building. Indoor environments can be very complex, and an insight into the design, and a thorough understanding of the performance of DASs inside the building is required. In this thesis, the performance of an in-building DAS employing frequency reuse is examined, where remote antenna units (RAUs) are deployed on each floor throughout the building and connected to a central unit (CU) where received signals are processea. The impact of co-channel interference on system performance is investigated by using a propagation channel model derived from multi-floor in-building path loss values retrieved from measurement results. System performance is investigated in terms of location-specific spectral efficiency and bit error rate (BER) which are analysed for a range of potential MT locations and various in-building propagation characteristics. The potential benefits of location based antenna selection and deployment options are also investigated. Co-channel interference cancellation where CUs cooperate through joint signal pro- cessing in order to reduce the impact of co-channel interference is considered. Results obtained suggest that the proposed scheme can facilitate better use of the available radio spectrum, and provide high data rates for indoor MTs
Performance Analysis of Small Cell and Distributed Antenna Systems for Indoor Mobile Communications
Full text linkFifth generation (5G) mobile communication systems aim to provide high data rate wireless transmissions and ubiquitous coverage to users but achieving this objective remains a challenge particularly in regions with high user density, such as urban/metropolitan areas and within buildings. To support users in indoor environments, indoor wireless communication systems are required, but frequency spectrum allocations are limited and requires reuse of the limited spectrum. Frequency reuse causes co-channel interference, which is detrimental to the performance and capacity of
indoor systems. In order to design efficient and reliable indoor systems, a thorough understanding of co-channel interference within buildings is vital. This paper presents a comparative study of the performance of indoor deployed small cell base station (SBS) and indoor distributed antenna systems (DAS) in an isolated multi-storey building. Each floor of the building is equipped with either an indoor SBS or an indoor DAS where geographically distributed remote radio heads (RRHs) are connected to a central unit (CU), and frequency reuse
is employed among floors. Signal propagation characteristics within multi-storey buildings and the impact of inter floor interference on system performance is analysed and compared for both systems. The effect of different reuse distances, pathloss exponents, penetration loss and co-channel interference on achievable rate is analysed over a wide range of potential mobile equipment (ME) locations
A Novel FIG-LSTM Ensemble Machine Learning Technique for Currency Exchange Rate Forecasting
Full text linkAccurately predicting currency exchange rate behaviour remains a major challenge for all stakeholders (e.g. traders, investment firms, banks, etc.) in the foreign exchange (forex) market. Developing machine learning models that offer more accurate and potentially more reliable predictions is identified as a critical objective for the forex market. To address this issue, this paper proposes an ensemble machine learning model that integrates fuzzy information granule (FIG) with long short-term memory (LSTM) in a gated recurrent unit (GRU) to achieve a better forex forecasting performance. The proposed model uses open, high, low, close (OHLC) data and relevant technical indicators such as moving average, bollinger bands, %b, bandwidth, moving average convergence divergence (MACD), relative strength index (RSI), and average true range (ATR) as inputs. The outputs of the combined FIG and LSTM models are passed into a trained GRU model to make the final forex prediction. To evaluate the predictive performance of the proposed model, experiments are conducted using one-day candles of three of the most traded currency pairs, EUR/USD, USD/GBP and USD/CAD from 01 August 2019 to 31 December 2023 data set. The proposed model shows better forecasting performance in terms of root mean squared error (RMSE), mean absolute percentage error (MAPE), mean absolute error (MAE), and coefficient of determination (R2) values when compared with conventional LSTM, FIG and GRU prediction models. The proposed FIG-LSTM model also outperforms a state-of-the-art GRU-LSTM hybrid prediction model
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