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Modeling and Comparison of Video Coding Techniques for Video Streaming in Wireless Mesh Networks: A Network Optimization Perspective
No full text本論文主旨在研究並分析視訊編碼技術於無線網狀網路之最佳化問題。目前許多相關研究主要在追求無線網狀網路上最大的流量來最佳化視訊品質，然而對於視訊串流的品質來說，追求最大的流量並非一定是最好的。在最佳化視訊串流的品質時，也需要考慮不同的視訊編碼技術特性。在本論文中，我們首先分析了不同網路模型變因對於最佳化視訊品質的影響。我們藉由考慮了MPEG-4、FGS以及MDC三種不同視訊編碼技術的位元率-失真函數，建構一個視訊串流品質在無線網狀網路之最佳化數學模型並進行效能比較。從結果中我們發現雖然MDC有較差的編碼效率，但是當網路鏈結的容量變小時，MDC會有比MPEG-4與FGS更好的視訊品質。其次，我們考慮了最短路徑延遲、最少路徑跳躍次數以及最短路徑距離三種不同的路由層機制，來討論他們在使用不同編碼技術時，與視訊品質最佳化路由在選擇路徑與對視訊品質影響的差異。由此延伸模型的結果，我們發現最短路徑延遲路由是三種路由層機制當中表現最好的，特別是當選用MDC作為編碼技術的情況下，效能與視訊品質最佳化路由相差不到0.2 dB。最後，我們進一步考慮了傳輸功率控制與傳輸速率調整兩種媒體控制層機制，在使用不同編碼技術時對最佳化視訊品質的影響。我們發現在考慮了媒體控制層的機制後，FGS視訊品質提升之程度是三者中最好的，而MDC由於其解碼的獨立性，在不同網路環境下有較穩定的視訊品質。模擬結果顯示，在尋求視訊品質最佳化的目標下，在選擇不同視訊編碼技術時，需要考慮路由層以及媒體控制層機制所造成的影響。The objective of this thesis is to analyze and optimize video performance using different coding techniques over wireless mesh networks. Most work focuses on achieving the highest throughput for performance optimization in mesh networks. However, this goal is not always the best for video streaming, and the characteristics of video coding techniques need to be considered. In this thesis, we first investigate the impact of network factors on optimal video quality. We build an optimization framework for video streaming in mesh networks by considering rate-distortion optimization of different coding techniques. The optimization problem can be formulated as a mixed integer nonlinear programming, and we evaluate the performance of different coding techniques, including MPEG-4, Fine Granularity Scalability (FGS), and Multiple Description Coding (MDC) in the proposed framework. We find that although MDC has poor coding efficiency, it performs better than MPEG-4 and FGS when the link capacity is small. We next extend the proposed framework to incorporate the impact of routing layer mechanisms, including minimum delay routing, minimum hop routing, and minimum distance routing. We discuss their difference from the optimal routing, and find that minimum delay routing performs best, especially when MDC is used. Finally, we extend the framework to incorporate the impact of MAC layer mechanisms, including transmission power control and rate adaptation. We find that among the different coding techniques, FGS improves most when using MAC layer mechanisms. MDC has stable performance for different network conditions due to the independency of multiple descriptions. We conclude that the optimal choice of video coding techniques should consider the routing and MAC layer mechanisms in mesh networks.ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . iiIST OF TABLES . . . . . . . . . . . . . . . . . . . . . viIST OF FIGURES . . . . . . . . . . . . . . . . . . . . viiHAPTER 1 INTRODUCTION . . . . . . . . . . . . . . . . . 1HAPTER 2 BACKGROUND . . . . . . . . . . . . . . . . . . 5.1 Video Technology Fundamental . . . . . . . . . . . . 5.1.1 Video Coding . . . . . . . . . . . . . . . . . . . 5.1.2 MPEG-4 Simple Profile . . . . . . . . . . . . . . 6.1.3 Fine Granularity Scalability . . . . . . . . . . . 9.1.4 Multiple Description Coding . . . . . . . . . . . 11.2 Related Works . . . . . . . . . . . . . . . . . . . 14.2.1 Testbed Experiment . . . . . . . . . . . . . . . 14.2.2 Routing Protocols Modification . . . . . . . . . 15.2.3 Optimization Approach . . . . . . . . . . . . . . 15.3 Optimization Approaches . . . . . . . . . . . . . . 17.3.1 Introduction of MINLP . . . . . . . . . . . . . . 17.3.2 Sequential Quadratic Programming . . . . . . . . 18.3.3 Branch-and-bound . . . . . . . . . . . . . . . . 18.3.4 Optimization Example . . . . . . . . . . . . . . 19.4 Motivation . . . . . . . . . . . . . . . . . . . . 22HAPTER 3 AN OPTIMIZATION FRAMEWORK FOR VIDEO STREAMING OVER WMNS . . . . . . . . . . . . . . . . . . . . . . . 24.1 Video Distortion Model . . . . . . . . . . . . . . 24.1.1 Video Quality Evaluation Tool . . . . . . . . . . 24.1.2 Rate-Distortion Theory . . . . . . . . . . . . . 25.1.3 MPEG-4 Coding Model . . . . . . . . . . . . . . . 26.1.4 Fine Granularity Scalability Video Coding Model . 27.1.5 Multiple Description Coding Model . . . . . . . . 29.2 Network Model . . . . . . . . . . . . . . . . . . . 31.2.1 Packet Loss Rate . . . . . . . . . . . . . . . . 33.2.2 Aggregated Traffic . . . . . . . . . . . . . . . 33.2.3 Delay Model . . . . . . . . . . . . . . . . . . . 33.3 Interference Model . . . . . . . . . . . . . . . . 34.3.1 Maximal Independent Set . . . . . . . . . . . . . 34.3.2 Cliques . . . . . . . . . . . . . . . . . . . . . 36.3.3 Node Independent Pairs . . . . . . . . . . . . . 37.3.4 Link Independent Sets . . . . . . . . . . . . . . 38.4 Summary . . . . . . . . . . . . . . . . . . . . . . 38HAPTER 4 COMPARISON OF DIFFERENT CODING TECHNIQUES . . 41.1 Model Validation . . . . . . . . . . . . . . . . . 41.1.1 Rate-Distortion Model . . . . . . . . . . . . . . 41.1.2 Loss Distortion Model . . . . . . . . . . . . . . 43.2 Grid Topology . . . . . . . . . . . . . . . . . . . 44.2.1 Optimized Rate . . . . . . . . . . . . . . . . . 44.2.2 Effect of Delay Models . . . . . . . . . . . . . . 46.2.3 Impact of Different Video Coding techniques . . . 46.3 Roofnet Topology . . . . . . . . . . . . . . . . . 49.3.1 Impact of Interference Model . . . . . . . . . . 50.4 Summary . . . . . . . . . . . . . . . . . . . . . . 51HAPTER 5 MODELING AND IMPACT OF ROUTING LAYERECHANISMS . . . . . . . . . . . . . . . . . . . . . . 52.1 Category of Routing Protocols . . . . . . . . . . . 52.1.1 Minimum Hop Counts . . . . . . . . . . . . . . . 52.1.2 Minimum Delay . . . . . . . . . . . . . . . . . . 53.1.3 Minimum Distance . . . . . . . . . . . . . . . . 54.2 Results of Different Routing objectives . . . . . . 54.2.1 Difference between Different Routing objectives . 54.2.2 Impact of Capacity Variance . . . . . . . . . . . 56.2.3 Impact of Coding Techniques in Minimum Delay Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59.2.4 Impact of Encoding Techniques in Minimum Hops Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.2.5 Impact of Encoding Techniques in Minimum Distance Routing . . . . . . . . . . . . . . . . . . . . . . . . 64.3 Summary . . . . . . . . . . . . . . . . . . . . . . 67HAPTER 6 MODELING AND IMPACT OF MAC LAYER MECH-NISMS . . . . . . . . . . . . . . . . . . . . . . . . 69.1 Model of MAC Characteristics . . . . . . . . . . . 69.1.1 Model of Transmission Power . . . . . . . . . . . 69.1.2 Rate Adaptation . . . . . . . . . . . . . . . . . 70.1.3 Noise and Interference Model . . . . . . . . . . 71.1.4 BER . . . . . . . . . . . . . . . . . . . . . . . 72.2 Results of Optimization Including MAC Layer Model . 73.2.1 Impact of Rate Adaptation . . . . . . . . . . . . 73.2.2 Impact of Power Control . . . . . . . . . . . . . 77.3 Summary . . . . . . . . . . . . . . . . . . . . . . 84HAPTER 7 CONCLUSION AND FUTURE WORK . . . . . . . . . 86PPENDIX A RELATIONSHIP BETWEEN BER AND SNR FROMNTERSIL HFA3861B . . . . . . . . . . . . . . . . . . . 87EFERENCES . . . . . . . . . . . . . . . . . . . . . . 8
Institutional Buying Behavior and Net Fund Inflow: Empirical Study on Taiwanese Equity Mutual Fund
No full text本研究以2001至2014年所有台灣開放式股票型基金為樣本，觀察當基金經理人遇到資金淨流入時，傾向採取何種買進策略，及該策略對於基金績效與後續資金流的影響，即連結資金流-買進策略-績效三個構面，並以行為財務理論解釋所觀察到的現象。 本研究最主要的結論為，當面對資金淨流入時，基金經理人傾向加碼原有的持股，而非找尋新的標的，而這樣的行為有助於基金後續績效勝過其他基金，表示基金經理人因過去績效好而吸引資金流入，自信因而受到強化，因此相信自己原先的判斷而加碼原持股，且比起其他面對淨流出的競爭對手，更有餘裕地加碼持股中動能較差的股票，實證研究顯示這類被贏家基金選中、過去表現差的股票，對於基金長期績效有正面貢獻，此亦可歸因台股基金經理人之績效於選股能力之差異，即能力強的經理人本就持有潛在具上漲空間的股票，而資金流入則給予其等待市場調整股價的空間。本研究亦發現台股經理人無論在淨流入或流出時，皆不受處分效果的影響，與過去以台灣為樣本的實證結果不同。This study focuses on the fund managers’ buying decision following net fund inflow. Observations of the behavior of Taiwanese equity mutual fund managers are made within 2001-14 time frame. I demonstrate how the fund flows affect the fund managers’ buying behavior and how the behavior affects future performance and subsequent fund flows. The main finding of this study is fund managers tend to invest in the stocks they already have when facing net fund inflows, which increases the funds’ performance compared to other competitors’ and attract further inflows. This indicates fund inflows allow fund managers to gain confidence and provide them room to wait for the market to correct the undervalued stocks and enjoy persistent performance. Also, unlike previous studies, I found that Taiwanese fund managers do not show disposition effect
Enhanced mobile hybridization of gold nanoparticles decorated with oligonucleotide in microchannel devices
No full textMoving toward end-to-end support for handoffs across heterogeneous telephony systems on dual-mode mobile devices
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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
Crystallization mechanisms and recording characteristics of Si/CuSi bilayer for write-once blu-ray disc
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