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Approved for public release, distribution is unlimited / As more and more devices with a variety of capabilities are Internet-capable, device independence becomes a big issue when we would like the information that we request to be correctly displayed. This thesis introduces and compares how existing standards create a profile that describes the device capabilities to achieve the goal of device independence. After acknowledging the importance of device independence, this paper utilizes the idea to introduce a Device-Aware Network (DAN). DAN provides the infrastructure support for device-content compatibility matching for data transmission. We identify the major components of the DAN architecture and issues associated with providing this new network service. A Device-Aware Network will improve the network's efficiency by preventing unusable data from consuming host and network resources. The device profile is the key issue to achieve this goal. / Captain, Taiwan Army

Approved for public release; distribution in unlimited. / As the popularity of Internet soars, the content on the Internet is increasingly accessed by mobile devices that are usually small in form factor and limited in resources, in terms of processing capability, bandwidth and battery power. With the changing environment, content providers must serve a large number of access devices with different profiles, while the users have access to a large number of services with different content types. A key challenge in such an environment is how to enable the best possible fit between content and capabilities of a specific access device type. The goal of this thesis research is to explore on the concept of a device-aware network (DAN) that can provide the infrastructure support for device-content compatibility matching to avoid the unnecessary wastage of network and device resources that happens in current device-ignorant networks. A more efficient architecture is proposed which encapsulates device profile information in transmitting packets and incorporates content repurposing functionality in existing network entities, such as routers along the data path. Simulation models are developed to statistically evaluate the performance of the proposed architecture in comparison to existing content repurposing frameworks. The results demonstrated the feasibility and suitability of the architecture, with improvement in network bandwidth conservation. / Civilian, Singapore Defence Science and Technology Agency

It is specifically important to focus on voltage stability analysis of the power system to avoid worst case scenarios such as voltage collapse. The purpose of this thesis is to identify methods for enhancing the steady-state voltage stability using FACTS devices and determining their impact on real and reactive power losses, improvement of bus voltage magnitude, and transmission line loadability. To achieve this, FACTS devices such as Static VAR Compensator (SVC), Static Synchronous Compensator (STATCOM), and Thyristor Controlled Series Capacitor (TCSC) are used in the test system as three separate test cases. The results obtained assist in drawing conclusions on the effectiveness of each FACTS devices at generator, load and swing buses, on lines between two load buses, and between a load bus and a generator bus, in terms of metrics such as voltage magnitude profile, PV curves, and active and reactive power losses.

by Lee Sui Yip. / Thesis (M.Sc.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references. / Chapter Chapter1 --- Introduction / Chapter 1.1 --- Objectives of Common Channel Signalling --- p.1.1 / Chapter 1.1.1 --- Channel Associated Signalling --- p.1-1 / Chapter 1.1.2 --- Common Channel Signalling --- p.1.2 / Chapter 1.2 --- Functional Description --- p.1.3 / Chapter 1.3 --- Signalling Network Basics --- p.1.5 / Chapter 1.4 --- Network Topology --- p.1.9 / Chapter 1.5 --- Signalling Messages --- p.1.13 / Chapter Chapter2 --- Common Channel Signalling No. 7 Network of Hong Kong Telephone / Chapter 2.1 --- System Performance Criteria --- p.2.1 / Chapter 2.1.1 --- Post Dialing Delay --- p.2.2 / Chapter 2.1.2 --- Availability --- p.2.3 / Chapter 2.1.3 --- Survivabiliy --- p.2.3 / Chapter 2.2 --- Implementation Considerations --- p.2.4 / Chapter 2.2.1 --- System Constraints --- p.2.4 / Chapter 2.2.2 --- Number of Signal Transfer Points --- p.2.5 / Chapter 2.2.3 --- Signalling Modes and Assignments --- p.2.6 / Chapter 2.2.4 --- Signalling Link-sets and Diversity --- p.2.7 / Chapter 2.2.5 --- Post Dialing Delay --- p.2.7 / Chapter 2.3 --- The Common Channel Signalling Network of Hong Kong Telephone --- p.2.7 / Chapter Appendix : --- Queuing Delay Estimation --- p.2.9 / Chapter Chapter3 --- Message Routing Policy / Chapter 3.1 --- Originating Signalling Point --- p.3.2 / Chapter 3.2 --- Selection of Signalling Links --- p.3.3 / Chapter 3.3 --- Signal Transfer Points --- p.3.5 / Chapter 3.3.1 --- Same Cluster --- p.3.6 / Chapter 3.3.2 --- Adjacent Clusters --- p.3.6 / Chapter 3.3.3 --- Distant Clusters --- p.3.7 / Chapter 3.4 --- Destination Signalling Point --- p.3.8 / Chapter Appendix : --- STP Stages Estimation --- p.3.9 / Chapter Chapter4 --- Building the Simulation Model / Chapter 4.1 --- Modelling Objective --- p.4.1 / Chapter 4.2 --- The Cluster Level Model --- p.4.2 / Chapter 4.2.1 --- Message Generation --- p.4.2 / Chapter 4.2.2 --- Modelling Message Routing --- p.4.3 / Chapter 4.2.3 --- Modelling Failures --- p.4.5 / Chapter 4.2.4 --- The Simulation Procedures --- p.4.6 / Chapter 4.2.4.1 --- Processes --- p.4.6 / Chapter 4.2.4.2 --- Permanent Entities --- p.4.8 / Chapter 4.2.4.3 --- Initialization Routines --- p.4.9 / Chapter 4.3 --- The Signalling Point Level Model --- p.4.11 / Chapter 4.3.1 --- Message Generation and Routing --- p.4.13 / Chapter 4.3.2 --- Simulation Procedures --- p.4.13 / Chapter Chapter5 --- Network Planning and Evaluation with the Simulation Model / Chapter 5.1 --- Model Testing --- p.5.1 / Chapter 5.2 --- Comparison with Analytical Results --- p.5.2 / Chapter 5.3 --- Modelling with 1 STP Failure --- p.5.5 / Chapter 5.4 --- Simulation with Measured Data --- p.5.8 / Chapter 5.5 --- Network Performance Evaluation --- p.5.15 / Chapter 5.5.1 --- Normal Conditions --- p.5.15 / Chapter 5.5.2 --- STP Failures --- p.5.16 / Chapter 5.5.3 --- Signalling Link-set Failures --- p.5.17 / Chapter 5.6 --- Network Planning --- p.5.19 / Chapter 5.6.1 --- Re-allocation of Signalling Points --- p.5.21 / Chapter 5.6.2 --- Re-configuration of Signalling Network --- p.5.21 / Chapter 5.6.3 --- Associated Link Provision Policy --- p.5.22 / Chapter 5.6.4 --- New Message Routing Policy --- p.5.22 / Discussion and Conclusion / References

The study of systems for querying data streams, coined Data Stream Management Systems (DSMS), has gained in popularity over the last several years. This new area of research for the database community includes studies in areas such as Sensor Networks, Network Intrusion, and monitoring data such as Medicine, Stock, or Weather feeds. With this new popularity comes increased performance expectations, with increased data sizes and speed and larger more complex query plans as well as high volumes of possibly small queries. Due to the finite resources on a single query processor, future Data Stream Management Systems must distribute their workload to multiple query processors, working together in a synchronized manner. This thesis discusses a new Distributed Continuous Query System (D-CAPE) developed here at WPI that has the ability to distribute query plans over a large cluster of machines. We describe the architecture of the new system, policies for query plan distribution to improve overall performance, as well as techniques for self-tuning query plan re-distribution. D-CAPE is designed to be as flexible as possible for future research. We include a multi-tiered architecture that scales to a large number of query processors. D-CAPE has also been designed to minimize the cost of the communications network by bundling synchronization messages, thus minimizing packets sent between query processors. These messages are also incremental at run-time to aid in minimizing the communication cost of D-CAPE. The architecture allows for the flexible incorporation of different distribution algorithms and operator reallocation policies.. D-CAPE provides an operator reallocation algorithm that is able to seamlessly move an operator(s) across any query processors in our computing cluster. We do so by creating ``pipes" between query processors to allow the data streams to flow, and then filling these pipes with data streams once execution begins. Operator redistribution is accomplished by systematically reconnecting these pipes as to not interrupt the data flow. Experimental evaluation using our real prototype system (not just simulation) shows that executing a query plan distributed over multiple machines causes no more overhead than processing it on a single centralized query processor; even for rather lightly loaded machines. Further, we find that distributing a query plan among a cluster of query processors can boost performance up to twice that of a centralized DSMS. We conclude that the limitation of each query processor within the distributed network of cooperating processors is not primarily in the volume of the data nor the number of query operators, but rather the number of data connections per processor and the allocation of the stateful and thus most costly operators. We also find that the overhead of distributing query operators is very low, allowing for a potentially frequent dynamic redistribution of query plans during execution.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 104-106. / by Oliver Chukwudi Ibe. / Sc.D.

Este trabalho propõe uma nova metodologia para a solução do problema de coordenação de relés direcionais de sobrecorrente em sistemas de transmissão em malha. São utilizadas informações sobre a atuação do relé como dispositivo de proteção principal (ou retaguarda local no caso de se considerar o relé de distância) e também de sua atuação como proteção de retaguarda remota, fornecendo uma base mais sólida para definição dos ajustes. A partir de uma série de critérios determinados de acordo com a instalação, define-se uma área de ajuste do relé, diretamente sobre sua curva de atuação. Sobre esta área, aplica-se um método de otimização capaz de encontrar o melhor ajuste possível para o dispositivo em análise. A metodologia é aplicada sem a necessidade de uma análise topológica do sistema, sendo que as informações da localização do relé e sua integração com os outros dispositivos de proteção são resumidas durante o estudo de curto-circuito, que fornece os dados de entrada para a metodologia. O algoritmo resume os critérios de coordenação em pontos de referência, de modo que a análise é feita relé a relé, eliminando assim problemas comuns como o de tratamento de banco de dados e ganhando em agilidade e simplicidade no tratamento do problema. A resposta fornecida é bastante intuitiva, sendo fácil entender os resultados obtidos e quais seriam as implicações caso na prática sejam necessárias adequações à instalação. / This work proposes a new methodology to solve the problem of coordination of directional overcurrent relays in meshed transmission systems. Using information about the operation of the directional relay as primary protection (or local backup, in the case of considering the distance relay) and also its role as remote backup protection, the methodology provides a more solid basis for defining settings. Based on a series of criteria determined in accordance with the installation, an area of relay feasible settings is defined directly over their time-overcurrent curve. On this area, an optimization method is applied to find the best possible setting for the device under analysis. The method is applied without the need for topological analysis of the system, and the information of the relay location and its integration with other protective devices are summarized during the short circuit study, which provides the input data for the methodology. The algorithm summarizes the criteria of coordination in landmarks and the analysis is performed relay by relay, thus common problems are eliminated, such as database treatment, gaining agility and simplicity in treating the problem. The answer provided is extremely intuitive, making it easy to understand the results and what would be the implications in case of, in practice, be necessary to perform adjustments to fit with the installation.

An increasing number of network applications use reliable transport protocols. Applications with constant data transmission recover from loss without major performance disruption, however, applications that send data sporadically, in small packets, also called thin-streams, experience frequently high latencies due to 'Bufferbloat', that reduce the application performance. Active Queue Management mechanisms were proposed to dynamically manage the queues in routers by dropping packets early and reduce these, hence reducing latency. While their deployment to the internet remains an open issue, the proper investigation into how their functioning mechanism impacts latency is the main focus of this work and research questions have been devised to investigate the AQM impact on latency. A range of AQM mechanisms has been evaluated by the research, exploring performance of the methods for latency sensitive network applications. This has explored new single queue AQM mechanisms such as Controlled Delay (CODEL) and Proportional Integral Enhanced (PIE) and Adaptive RED (ARED). The evaluation has shown great improvements in queuing latency when AQM are used over a range of network scenarios. Scheduling AQM algorithms such as FlowQueue CODEL (FQ-CODEL) isolates traffic and minimises the impact of Bufferbloat on flows. The core components of FQ-CODEL, still widely misunderstood at the time of its inception, have been explained in depth by this study and their contribution to reducing latency have been evaluated. The results show significant reductions in queuing latency for thin streams using FQ-CODEL. When TCP is used for thin streams, high application latencies can arise when there are retransmissions, for example after dropping packets by an AQM mechanism. This delay is a result of TCP's loss-based congestion control mechanism that controls sender transmission rate following packet loss. ECN, a marking sender-side improvement to TCP reduces applicationlayer latency without disrupting the overall network performance. The thesis evaluated the benefit of using ECN using a wide range of experiments. The findings show that FQ-CODEL with ECN provides a substantial reduction of application latency compared to a drop-based AQM. Moreover, this study recommends the combination of FQ-CODEL with other mechanisms, to reduce application latency. Mechanisms such as ABE, have been shown to increase aggregate throughput and reduce application latency for thin-stream applications.

Zhao Fei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 87-89). / Abstracts in English and Chinese. / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Multirate Scheme --- p.2 / Chapter 1.1.1 --- VSF Scheme --- p.3 / Chapter 1.1.2 --- Multicode Scheme --- p.5 / Chapter 1.2 --- Multicode CDMA System --- p.7 / Chapter 1.2.1 --- System Model --- p.7 / Chapter 1.2.2 --- Envelope Variation of Multicode Signal --- p.9 / Chapter 1.2.3 --- Drawback of Multicode Scheme --- p.11 / Chapter 1.3 --- Organization of the Thesis --- p.13 / Chapter 2. --- Related Work on Minimization of PAP of Multicode CDMA --- p.15 / Chapter 2.1 --- Constant Amplitude Coding --- p.16 / Chapter 2.2 --- Multidimensional Multicode Scheme --- p.22 / Chapter 2.3 --- Precoding for Multicode Scheme --- p.25 / Chapter 2.4 --- Summary --- p.26 / Chapter 3. --- Multicode CDMA System with Constant Amplitude Transmission --- p.27 / Chapter 3.1 --- System Model --- p.28 / Chapter 3.2 --- Selection of Hadamard Code Sequences --- p.31 / Chapter 3.3 --- The Optimal Receiver for the Multicode System --- p.37 / Chapter 3.3.1 --- The Maximum-Likelihood Sequence Detector --- p.38 / Chapter 3.3.2 --- Maximum A Posteriori Probability Detector --- p.41 / Chapter 4. --- Multicode CDMA System Combined with Error-Correcting Codes --- p.45 / Chapter 4.1 --- Hamming Codes --- p.46 / Chapter 4.2 --- Gallager's Codes --- p.48 / Chapter 4.2.1 --- Encoding of Gallager's Codes --- p.48 / Chapter 4.2.2 --- Multicode Scheme combined with Gallager's Code --- p.52 / Chapter 4.2.3 --- Iterative Decoding of the Multicode Scheme --- p.55 / Chapter 4.3 --- Zigzag Codes --- p.59 / Chapter 4.4 --- Simulation Results and Discussion --- p.62 / Chapter 5. --- Multicode CDMA System with Bounded PAP Transmission --- p.68 / Chapter 5.1 --- Quantized Multicode Scheme --- p.69 / Chapter 5.1.1 --- System Model --- p.69 / Chapter 5.1.2 --- Interference of Code Channels --- p.71 / Chapter 5.2 --- Parallel Multicode Scheme --- p.74 / Chapter 5.2.1 --- System Model --- p.74 / Chapter 5.2.2 --- Selection of Hadamard Code Sequences --- p.75 / Chapter 6. --- Conclusions and Future Work --- p.82 / Chapter 6.1 --- Conclusions --- p.82 / Chapter 6.2 --- Future Work --- p.84 / Bibliography --- p.87