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Thesis (Ph. D.)--Worcester Polytechnic Institute. / Keywords: In-process inspection; tolerance assignment; tolerance stack-up analysis; quality control planning. Includes bibliographical references (leaves 136-148).

Thesis (Ph.D.) - Carleton University, 2002. / Includes bibliographical references (p. 194-201). Also available in electronic format on the Internet.

隋著移動數據網絡的迅速發展，世界各地部署著不同制式的3G，HSPA和LTE網絡，這給移動互聯網應用帶來新的機遇和挑戰。不像他們的對手, 有線網絡，移動數據網絡有較長的延遲，較高的包率，以及急劇波動的頻寬。為了應付這些挑戰，移動無線基站往往配備較大的緩衝區（KBs以至數百多MBs），以吸收短期的頻寬波動，並促進鏈路層重傳。然而，由於大部分互聯網協議，並特別是TCP，全都假設路由器只擁有較小緩衝區，所以在移動網絡的大型緩衝區下，往往導致TCP展現出次優的性能。本論文解決兩個根本性的問題來克服這一項挑戰。首先，我們開發了一種新算法 (SoD）專門來估計網絡的鏈路緩衝區的大小和隊列長度。在今天的3G移動數據網絡，本文以大量網絡數據驅動的模擬結果證明 SoD 表現優於現有的算法，如 Max-min 和 Loss-pair。另外，我們採用 SoD算法來創造新的TCP擁塞控制模塊以解決移動網絡的大型緩衝區以及的頻寬波動問題。這個新的TCP變種，稱為 TCP- QA，在模擬情況以及移動數據網絡下均表現出大大優於現有的TCP變種，包括TCP CUBIC ，TCP Vegas，TCP Westwood，和FAST TCP。 / The rapidly emerging mobile data networks fueled by the world-wide deployment of 3G, HSPA, and LTE networks created new opportunities and challenges for developing mobile Internet applications. Unlike their wired counterpart, mobile data networks are known to exhibit longer delay, higher packet loss rate, and rapidly fluctuating bandwidth. To tackle these challenges mobile radio base stations are often equipped with large buffers (from hundreds of KBs to multi-MBs) to absorb short-term bandwidth fluctuations and to facilitate link-layer retransmissions. However as most Internet protocols in general, and TCP in particular, were designed with the assumption of small router buffer size, the large buffer in mobile networks can and do interact, often negatively, with the Internet protocols, leading to sub-optimal performance. This work tackles two fundamental problems in overcoming this challenge. First, we developed a novel Sum-of-Delays (SoD) algorithm specifically designed to estimate the link buffer size and queue length of bandwidth-varying networks. Extensive trace-driven simulation results showed that SoD outperforms existing algorithms such as max-min and loss-pair by orders of magnitude in today’s 3G mobile data networks. Second, we apply the SoD algorithm to TCP’s congestion control module to incorporate and compensate for the mobile network’s large buffer size. This new TCP variant, called TCP-Queue-length-Adaptive (TCP-QA), substantially outperforms existing TCP variants including TCP CUBIC, TCP Vegas, TCP Westwood, and FAST TCP. / Detailed summary in vernacular field only. / Chan, Chi Fung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Abstract --- p.ii / 摘要 --- p.iii / Acknowledgements --- p.iv / Contents --- p.v / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Background and Related Work --- p.5 / Chapter 2.1 --- Link Buffer Size Estimation --- p.6 / Chapter 2.2 --- Queue Length Estimation --- p.8 / Chapter 2.3 --- Performance over Fixed Networks --- p.10 / Chapter 2.4 --- Performance over Bandwidth-Varying Networks --- p.15 / Chapter Chapter 3 --- Sum-Of-Delay Method --- p.19 / Chapter Chapter 4 --- Performance Evaluation --- p.22 / Chapter 4.1 --- Link Buffer Size Estimation in Fixed Bandwidth Networks --- p.23 / Chapter 4.2 --- Link Buffer Size Estimation in Variable Bandwidth Networks --- p.25 / Chapter 4.3 --- Queue Length Estimation in Fixed Bandwidth Networks --- p.28 / Chapter 4.4 --- Queue Length Estimation in Variable Bandwidth Networks --- p.31 / Chapter 4.5 --- Convergence --- p.34 / Chapter 4.6 --- Limitations in Passive Estimation --- p.40 / Chapter Chapter 5 --- Impact of Competing Traffic --- p.42 / Chapter 5.1 --- Simulation Setup --- p.42 / Chapter 5.2 --- Link Buffer Size Estimation --- p.44 / Chapter 5.3 --- Queue Length Estimation --- p.50 / Chapter 5.4 --- Discussions --- p.54 / Chapter Chapter 6 --- TCP-Queue-Length-Adaptive (TCP-QA) --- p.56 / Chapter 6.1 --- Challenges in Mobile Networks --- p.57 / Chapter 6.2 --- Queue-Length-Adaptive Congestion Control --- p.59 / Chapter 6.3 --- Performance Comparisons --- p.65 / Chapter Chapter 7 --- Summary and Future Work --- p.76 / Bibliography --- p.78

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2004. / Includes bibliographical references (leaves 127-136).

Abstract In this thesis, we consider the performance evaluation of peer-to-peer (P2P)streaming over wireless networks. Traditionally, P2P streaming has been implemented and analyzed extensively in wire line networks. As more and more devices are connected to the internet through wireless, however, it is critical to understand how wireless channel variability affects the performance of P2P systems. Weformulate the P2P streaming system as a queuing network, and analyze its performance based onthe large deviation principle. We are interested in characterizing the buffer underow probability, where users run of out content and cannot receive smooth video playback. As explicit analysis is very dicult with a nite number of users, we focus on characterizing the performance bounds when the number of users goes to innity, assuming that playback rate and buffer size both grow linearly with the number of users N. We show that the upper bound of buffer underow probability decays exponentially in N. We also compare the decay rate of bound in different channel models, and show that the Markov modulated channel leads to a faster decay rate than the I.I.D. model with the same expected channel capacities. / Leung, Kam Wong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 50-52). / Abstract --- p.i / Acknowledgement --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.1.1 --- Video Streaming --- p.2 / Chapter 1.1.2 --- Large Deviations Theory --- p.4 / Chapter 1.2 --- Related Works --- p.6 / Chapter 2 --- System Model and Assumptions --- p.9 / Chapter 2.1 --- System Model --- p.9 / Chapter 2.2 --- Assumptions --- p.11 / Chapter 2.3 --- Queuing Model --- p.12 / Chapter 3 --- Performance of Large Network --- p.16 / Chapter 3.1 --- Large Deviation Principle --- p.16 / Chapter 3.2 --- Time I.I.D. Channel Model --- p.23 / Chapter 3.3 --- Markov Modulated Channel --- p.29 / Chapter 3.4 --- Performance Comparison of Channel Model: Time I.I.D. Model vs Markov Modulated Model --- p.31 / Chapter 4 --- Simulation Result and Analysis. --- p.35 / Chapter 4.1 --- Simulation Settings --- p.35 / Chapter 4.2 --- The Performance Bounds of Different Playback Rates --- p.36 / Chapter 4.3 --- The Performance Bounds for Different Channel Transition Matrix --- p.37 / Chapter 5 --- Conclusion --- p.40 / Chapter A --- Appendix --- p.42 / Chapter A.1 --- Convexity of decay rate function for time I.I.D Model --- p.42 / Chapter A.2 --- Condition for the Chernoff Bound hold --- p.44 / Chapter A.3 --- Convergence of the Decay Rate Function --- p.44 / Chapter A.4 --- Moment Generating Function of Markov Modulated Sources --- p.46 / Chapter A.5 --- Limiting Probability Distribution of Capacity of Markov Channel --- p.47 / Chapter A.6 --- Computation: Capacity p.d.f of Two States Markov Modulated Channel --- p.48 / Bibliography --- p.50

With the increased attention on high efficiency and controllability of industrial processes, as well as reduced weight, volume and cost of consumer products, the applications of nonlinear power electronic converters such as adjustable speed drives (ASDs) are showing a rapid rise. Power Quality (PQ) is becoming an increasing concern with the growth of both sensitive and disturbing nonlinear loads in the residential, commercial and industrial levels of the power system, where PQ related disruptions can cause system malfunction, product loss, and hardware damage resulting in costly data loss and downtime. Investigating and mitigating PQ issues pertaining to the input supply of ASDs and other sensitive power electronic equipment is extremely important in maintaining a high level of productivity. In response to these concerns, this research focuses on the development of a power quality test platform (PQTP) that has been implemented at Oregon State University (OSU), in the Motor Systems Resource Facility (MSRF). The central component of the PQTP is a 120kVA programmable ac power source with an integrated arbitrary waveform generator (AWG) which creates realistic voltage disturbance conditions that can be used to characterize ride-through capabilities of industrial processes in a controlled environment. Also presented is a command driver database that has been created and tested, using Lab VIEW, which contains the functionality necessary to conduct a wide range of power quality research and testing projects by remotely configuring and controlling the AWG. The power quality research and testing capabilities of the PQTP are demonstrated with ASD diode-bridge rectifier operation analysis and ride-through characterization. This research shows the transition of an ASD's three-phase diode rectifier into single-phase diode rectifier operation when relatively small single-phase voltage sags are applied to the input. Also shown are ride-through characterizations of varying sizes and configurations of ASDs when subjected to single, two, and three-phase voltage sags as well as capacitor switching transients. In addition, ASD topologies providing improved ride-through capabilities are determined. / Graduation date: 2002

University of Macau / Faculty of Science and Technology / Department of Electrical and Computer Engineering

Service quality as a component of overall Information Systems quality is examined. Three related studies test the SERVQUAL and related instruments (SERVPERF and Importance-weighted SERVPERF) using Information System users. SERVPERF outperformed SERVQUAL in all three studies.

Data stream systems have to deal with massive data volumes. To perform several queries in parallel or to perform even a single query, resources must be planned carefully and the resulting quality-of-service (QoS) is lower than the best one. Typical QoS measures are the output delay and the amount of data in the stream used for the processing. In this paper, we introduce a model which allows to describe stream operators and the streams between the operators of an operator graph belonging to a stream query. The model allows us to calculate the resources consumed by a query graph given a certain result quality. Furthermore, it can be used to determine in advance if the quality-of-service requirement of a given query can be met with the actual available system resources. This model is the basis for building QoS-guaranteeing systems.