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Distributed Markov-based Primary User Protection Framework for Cognitive Radio
No full text近年來，由於無線技術的進步，在日常生活中有越來越多的無線設備和基地台架設，像是無線都會網路、無線區域網路、以及無線個人網路。這些無線網路系統必須佔用部分頻段，隨著越來越多無線標準的提出、運作，可用的無線頻譜也就越來越珍貴。
然而研究顯示出頻帶的使用情形極度不平衡。針對這樣的問題，在1999年提出了感知無線電，感知無線電是一種有智慧的通訊系統，
它可以察覺周遭環境變化，並從中學習，進而調整內部參數設定，做出最佳決定。
這篇論文基於感知無線電的理論，提出一種在無線網路(802.11)架構下，保證優先使用者資料傳輸的機制，這個機制保證優先使用者和感知無線電使用者共存的情形下，感知無線電使用者的資料傳輸將會被限制以達到保證優先使用者的傳送資料不會受到感知無線電使用者的影響。我們使用馬可夫模型分析了在優先使用者傳輸未達到飽和狀態
以及感知無線電使用者傳輸已達飽和狀態下，優先使用者的資料傳送量與感知無線電使用者的傳送參數的關連性，藉由這個關連性，我們可以找出最佳的傳輸參數設定以保障優先使用者的資料傳輸。
我們透過網路模擬器的實驗來驗證我們提出的模型，此外，我們也利用模樣測試來證明我們提出的演算法表現良好。In recent years, with wireless technologies advanced, there are more and more wireless devices and base stations deployment. These wireless systems must occupy some frequency bands. As a result, with more and more wireless standards released and implemented frequency spectrum is getting treasurable. Although frequency spectrum exhibits scarcity, research shows that spectrum is inefficiently and unbalanced utilized. The idea of cognitive radio was proposed in 1999 by Joseph Mitola to efficiently utilized the unused frequency spectrum and increase overall utilization. It is defined as an intelligent wireless system that is aware of it surrounding environment and learns from it to adapt its internal parameters in realtime.
Based on the concept of cognitive radio, we propose "Markov-based Primary User Protection" in 802.11 environment. This scheme addresses the coexistence of primary users and cognitive radio users and guarantees the transmission of primary users will not be affected by cognitive radio users. At the same time, cognitive radio users can maximize their traffic to efficiently utilized the available channel resources. We first analyze the non-saturation Markov model of primary user as well as saturation Markov model of cognitive radio user. Combining two models together, we find out the relationship between current load of primary users and the optimal transmission parameter setting that can guarantee the usage of primary users.
We validate our model by comparing the calculation yielded by the model and the results of simulation. In addition, we also verify our proposed algorithm behaves well through simulations.Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
中文摘要. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Table of Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Cognitive Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Research Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Our Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Ongoing Research on CR . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Channel Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Distributed Markov-based Primary User Protection Framework . . . . . . 9
3.1 Channel Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2.1 Spectrum Information Collection . . . . . . . . . . . . . . . . 11
3.2.2 Markov-based Analytical Model . . . . . . . . . . . . . . . . . 13
3.2.3 Dynamic Adaption . . . . . . . . . . . . . . . . . . . . . . . . 26
4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1 Model Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.2 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.1 Performance Metrics . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.2 Simulation Settings . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.3 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . 33
5 Conclusion and Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 39
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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