Tesi sul tema "Bandwidth"

Broadband high-speed networks, such as B-ISDN, are expected to play a dominant role in the future of networking due to their capability to service a variety of traffic types with very different bandwidth requirements such as video, voice and data. to increase network efficiency in B-ISDN and other such connection oriented networks, the concept of a virtual path (VP) has been proposed and studied in the literature. A VP is a permanent or semi-permanent reservation of capacity between two nodes. Using VPs can potentially reduce call setup delays, simplify hardware, provide quality of service performance guarantees, and reduce disruption in the event of link or node failure.;In order to use VPs efficiently, two problems must be solved. With the objective of optimizing network performance, (1) the VPs must be placed within the network, and (2) network link capacity must be divided among the VPs. Most previous work aimed at solving these problems has focused on one problem in isolation of the other. at the same time, previous research efforts that have considered the joint solution of these problems have considered only restricted cases. In addition, these efforts have not explicitly considered the benefits of sharing bandwidth among VPs in the network.;We present a heuristic solution method for the joint problem of virtual path distribution and capacity allocation without many of the limitations found in previous studies. Our solution method considers the joint bandwidth allocation and VP placement problem and explicitly considers the benefits of shared bandwidth. We demonstrate that our algorithm out-performs previous algorithms in cases where network resources are limited. Because our algorithm provides shared bandwidth, solutions found by our algorithm will have a lower setup probability than a network that does not use VPs as well as a lower loss probability than provided by VPDBA solutions produced by previous algorithms. In addition, our algorithm provides fairness not found in solutions produced by other algorithms by guaranteeing that some service will be provided to each source-destination pair within the network.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California
“The radio frequency spectrum is a limited natural resource; therefore, efficient use of available spectrum is mandatory.” IRIG Standard 106-96 [4] As the availability of the frequency spectrum decreases and demands for bandwidth from users increases, the telemetry community will have to find ways to use spectrum efficiently. This paper is an overview of the major areas of research that promise potential increases in the efficient use of the telemetry spectrum. The discussion is summarized in a matrix that compares potential gains with overall costs for each research area using relative values of high, medium, and low.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.
Includes bibliographical references (p. 81-83).
Traditional oblivious routing algorithms either do not take into account the bandwidth demand, or assume that each flow has its own private channel to guarantee deadlock freedom. Though adaptive routing schemes can react to varying network traffic, they require complicated router designs. In this thesis, we present a polynomial-time heuristic routing algorithm that takes bandwidth requirements of each flow into account to minimize maximum channel load. The heuristic algorithm has two variants. The first one produces a deadlock-free route. The second one produces a minimal route, and is deadlock-free with two or more virtual channels assuming proper VC allocation. Both routing algorithms are oblivious, and need only simple router designs. The performance of each bandwidth-sensitive routing algorithm is evaluated against dimension-order routing and against the other on a number of benchmarks.
by Tina Wen.
M.Eng.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada
While the transition to IP internetworking in space-based applications has a tremendous upside, there are significant challenges of communications efficiency and compatibility to overcome. This paper describes a very high efficiency, low-risk, incremental architecture for migrating to IP internetworking based on the use of proxies. In addition to impressive gains in communications bandwidth, the architecture provides encapsulation of potentially volatile decisions such as particular vendors and network technologies. The specific benchmarking architecture is a NetAcquire Corporation COTS telemetry system that includes built-in TCP-Tranquility (also known as SCPS-TP) and Reed-Solomon Forward Error Correction capabilities as well as a specialized proxy-capable network stack. Depending on network conditions, we will show that the effective bandwidth for satellite transmissions can be increased as much as a factor of one hundred with no external changes to existing internetworking equipment.

Mestrado em Métodos Quantitativos para a Decisão Económica e Empresarial
Esta dissertação tem como objetivo comparar o desempenho de duas heurísticas com a resolução de um modelo exato de programação linear inteira na determinação de soluções admissíveis do problema de minimização da largura de banda para matrizes esparsas simétricas. As heurísticas consideradas foram o algoritmo de Cuthill e McKee e o algoritmo Node Centroid com Hill Climbing. As duas heurísticas foram implementadas em VBA e foram avaliadas tendo por base o tempo de execução e a proximidade do valor das soluções admissíveis obtidas ao valor da solução ótima ou minorante. As soluções ótimas e os minorantes para as diversas instâncias consideradas foram obtidos através da execução do código para múltiplas instâncias e através da resolução do problema de Programação Linear Inteira com recurso ao Excel OpenSolver e ao software de otimização CPLEX. Como inputs das heurísticas foram utilizadas matrizes com dimensão entre 4×4 e 5580×5580, diferentes dispersões de elementos não nulos e diferentes pontos de partida.
This dissertation intends to compare the performance of two heuristics with the resolution on the exact linear integer program model on the search for admissible solutions of the bandwidth minimization problem for sparse symmetric matrices. The chosen heuristics were the Cuthill and McKee algorithm and the Node Centroid with Hill Climbing algorithm. Both heuristics were implemented in VBA and they were rated taking into consideration the execution time in seconds, the relative proximity of the value obtained to the value of the optimal solution or lower bound. Optimal solutions and lower bounds were obtained through the execution of the code for several instances and trough the resolution of the integer linear problem using the Excel Add-In OpenSolver and the optimization software CPLEX. The inputs for the heuristics were matrices of dimension between 4×4 and 5580×5580, different dispersion of non-null elements and different initialization parameters.
info:eu-repo/semantics/publishedVersion

Bandwidth estimation has been extensively researched in the past. The majority of existing methods assume either negligible or fluid cross-traffic in the network during the analysis. However, on the present-day Internet, these assumptions do not always hold right. Hence, over such paths the existing bandwidth estimation techniques become inaccurate. In this thesis, we explore the problem assuming arbitrary cross-traffic and develop a new probing method called Envelope, which can simultaneously estimate bottleneck and available bandwidth over an end-to-end path with multiple heavily congested links. Envelope is based on a recursive extension of the stochastic queuing model first proposed by Kang, Liu, Dai and Loguinov (2004), and a modified packet-train methodology. We use two small packets to surround the probing packet-trains and preserve the inter-packet spacing of probe traffic at each router in the path-suffix. The preserved spacings are then used by the receiver to estimate bandwidth. We first reproduce results for a single congested router case using the model proposed by Kang et al. Next, we extend it to the case of multiple congested routers with arbitrary cross-traffic and develop the methodology Envelope. We evaluate the performance of Envelope in various network path topologies and cross-traffic conditions through extensive NS-2 simulations. We also evaluate various probe-traffic parameters which affect the accuracy of this method and obtain the range of values for these parameters that provide good estimation results. Finally, we compare the bandwidth estimation results of our method with the results of other existing methods such as IGI (2003) , Spruce (2003), Pathload (2002), and CapProbe (June 2004) using simulation in Network Simulator (NS-2) with varied network topologies and cross-traffic.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.
Includes bibliographical references (p. 105-106).
The sampling of continuous-time signals based on local bandwidth is considered in this thesis. In an intuitive sense, local bandwidth refers to the rate at which a signal varies locally. One would expect that signals should be sampled at a higher rate in regions of higher local bandwidth, and at a lower rate in regions of lower local bandwidth. In many cases, sampling signals based on local bandwidth can yield more efficient representations as compared with conventional uniform sampling, which does not exploit local signal characteristics. In the first part of the thesis, a particular definition for a linear time-varying lowpass filter is adopted as a potential model for local bandwidth. A sampling and reconstruction method permitting consistent resampling is developed for signals generated by such filters. The method does not generally result in perfect reconstruction except for a special class of self-similar signals. However, the reconstruction error is shown to decrease with the variation in the cut-off frequency of the filter. In the second part of the thesis, a definition for local bandwidth based on the time-warping of globally bandlimited signals is reviewed. Using this definition, a method is developed for sampling and reconstructing signals according to local bandwidth. The method employs a time-warping to minimize the energy of a signal above a given maximum frequency. A number of techniques for determining the optimal time-warping are examined.
by Dennis Wei.
M.Eng.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California
The selection of the Intermediate Frequency (IF) bandwidth filter for a data receiver for processing PCM data is based on using a peak deviation of 0.35 times the bit rate. The optimum IF bandwidth filter is equal to the bit rate. An IF bandwidth filter of 1.5 times the bit rate degrades the data by approximately 0.7 dB. The selection of the IF bandwidth filter for tracking receivers is based on the narrowest “noise bandwidth” that will yield the best system sensitivity. In some cases the noise bandwidth of the tracking receiver is the same as the IF bandwidth of the data receiver because it is the same receiver. If this is the case, the PCM bit rate determines the IF bandwidth and establishes the system sensitivity. With increasing bit rates and increased transmitter stability characteristics, the IF bandwidth filter selection criteria for a tracking receiver must include system sensitivity considerations. The tracking receiver IF bandwidth filter selection criteria should also be based on the narrowest IF bandwidth that will not cause the tracking errors to be masked by high bit rates and alter the pedestal dynamic response. This paper describes a selection criteria for a tracking receiver IF bandwidth filter based on measurements of the tracking error signals versus antenna pedestal dynamic response. Different IF bandwidth filters for low and high bit rates were used.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California
With every new spacecraft that is designed comes a greater density of information that will be stored once it is in operation. This, coupled with the desire to reduce the number of ground stations needed to download this information from the spacecraft, places new requirements on telemetry transmitters. These new transmitters must be capable of data rates of 320 Mbps and beyond. Although the necessary bandwidth is available for some non-bandwidth-limited transmissions in Ka-Band and above, many systems will continue to rely on more narrow allocations down to X-Band. These systems will require filtering of the modulation to meet spectral limits. The usual requirements of this filtering also include that it not introduce high levels of inter-symbol interference (ISI) to the transmission. These constraints have been addressed at CE by implementing a DSP technique that pre-filters a QPSK symbol set to achieve bandwidth-limited 320 Mbps operation. This implementation operates within the speed range of the radiation-hardened digital technologies that are currently available and consumes less power than the traditional high-speed FIR techniques.

Mestrado em Mathematical Finance
O problema de minimização de largura de banda em matrizes consiste em encontrar uma permutação de linhas e colunas de forma que os elementos não nulos sejam mantidos em uma banda o mais próximo possível da diagonal principal. Este problema é conhecido por ser NP-completo, e também pode ser formulado como um problema de rotulagem de vértices em um grafo. Além disso, a reordenação de instruções em programas de computador pode reduzir o pico de utilização de memória, desalocando recursos em pontos ideais. Isso resulta no problema de minimização do pico de memória, que é uma extensão do problema de minimização de largura de banda, uma vez que também pode ser formulado como um problema de rotulagem de vértices, onde instruções e a dependência de entrada/saída são traduzidas em vértices e arestas, respectivamente. Para esses grafos, baixa largura de banda implica em baixo pico de utilização de memória. Neste relatório, o impacto da redução da largura de banda é analisado ao resolver numericamente a equação do calor e ao reduzir o pico de utilização de memória em programas. Os problemas são cuidadosamente descritos e uma variedade de algoritmos são implementados em C++, com o objetivo de aproveitar ao máximo a redução da largura de banda.
The matrix bandwidth minimization problem consists in finding a permutation of rows and columns such that non-zero elements are kept in a band as close as possible to the main diagonal. This is a long-established NP-complete problem, that can also be formulated as a vertex labeling problem in a graph. Moreover, reordering instructions in computer programs may reduce peak memory usage by deallocating resources at optimal points of execution. This leads to the peak memory minimization problem, an extension of the bandwidth minimization problem, since it can also be formulated as a vertex labeling problem, where instructions and input/output dependency are translated into vertices and edges, respectively. Fortunately, for these graphs, low bandwidth implies low peak memory usage. In this report, the impact of bandwidth reduction is analyzed when numerically solving the heat equation and reducing peak memory usage of computer programs. The problems are carefully described and a variety of algorithms are implemented in C++, aiming to fully take advantage of bandwidth reduction.
info:eu-repo/semantics/publishedVersion

El funcionament del cervell es basa en processos complexos, que encara no s’han descrit i comprès detalladament. En les últimes dècades, la neurociència ha experimentat un desenvolupament accelerat, impulsat per noves neurotecnologías que permeten monitoritzar les dinàmiques de l’activitat elèctrica al cervell amb una major resolució espai-temporal i una àrea de cobertura més àmplia. No obstant això, a causa de l’alta complexitat de les xarxes neuronals al cervell, que són compostes per poblacions neuronals fortament interconnectades en àmplies regions cerebrals, estem lluny de detectar una fracció significativa de les neurones que donen lloc a funcions complexes. Per tal d’investigar les dinàmiques neuronals a gran escala amb alta resolució espacial, s’han utilitzat diverses tecnologies, que inclouen la ressonància magnética funcional (fMRI), imatges amb marcadors sensibles al voltatge o registres electrofisiològics d’alt recompte de sensors. No obstant això, la resolució temporal del fMRI i els mètodes òptics es limita típicament a uns pocs hertzs, gairebé tres ordres de magnitud per sota de la dels potencials d’acció, i es limiten a les condicions en què el subjecte es troba immòbil. D’altra banda, els registres electrofisiològics basats en matrius de microelèctrodes proporcionen una alta resolució espai-temporal, el que permet detectar amb precisió dinàmiques ràpides de centenars de neurones individuals simultàniament en animals que es mouen lliurement. No obstant això, les interfícies de detecció neuroelectrónica presenten una limitació en el producte entre la resolució espacial i l’àrea de cobertura. A més, presenten una baixa sensibilitat a la banda de freqüència infra-lenta (<0.5Hz), que està relacionada amb la connectivitat funcional de llarg abast. En aquesta tesi es presenta una nova tecnologia basada en sensors actius de grafè, que permet incrementar l’àrea de cobertura i la resolució espacial dels registres electrofisiològics conservant una alta sensibilitat en una banda de freqüència àmplia, des de l’activitat infra-lenta fins a la de una sola cèl·lula electrogénica. Aquest desenvolupament tecnològic es divideix en tres etapes principals; en primer lloc, s’obté una comprensió més profunda de les característiques intrínseques del soroll i la resposta en freqüència d’aquests sensors basant-se en l’estat de l’art en tecnologia de sensors de grafè. En la segona etapa, es mostra un sistema quasi-comercial basat en matrius de sensors de grafè epi-cortical i transmissió sense fil per a la implantació crònica en rates. Amb aquest sistema, es demostra la reproductibilitat de les matrius de sensors de grafè, la seva estabilitat a llarg termini i la seva biocompatibilitat crònica. A més, es proporciona evidència preliminar per a una àmplia gamma de nous patrons electrofisiològics gràcies a la seva sensibilitat en la banda de freqüència infra-lenta. Finalment, en l’última etapa d’aquesta tesi, l’enfocament se centra en el desenvolupament de noves estratègies de multiplexació per augmentar el nombre de sensors a les sondes neuronals. Aquestes tres etapes principals de desenvolupament han portat a la demostració del potencial de les matrius de sensors de grafè multiplexats per al mapejat de les dinàmiques neuronals a gran escala en una banda de freqüència àmplia, en animals que es mouen lliurement, durant llargs períodes. La combinació d’aquestes capacitats fa que les matrius de sensors actius de grafè siguin una tecnologia prometedora per a interfícies cervell-ordinador d’alt ample de banda i una eina única per investigar el paper de l’activitat infra-lenta en la coordinació de les dinàmiques neuronals d’alta freqüència.
El funcionamiento del cerebro se basa en procesos complejos, que aún no se han descrito y comprendido detalladamente. En las últimas décadas, la neurociencia ha experimentado un desarrollo acelerado, impulsado por nuevas neurotecnologías que permiten monitorear la dinámica de la actividad eléctrica en el cerebro con una mayor resolución espacio-temporal y un área de cobertura más amplia. Sin embargo, debido a la alta complejidad de las redes neuronales en el cerebro, que están compuestas por poblaciones neuronales fuertemente interconectadas en amplias regiones cerebrales, estamos lejos de monitorear una fracción significativa de neuronas que dan lugar a funciones complejas. Con el fin de investigar las dinámica neuronales a gran escala con alta resolución espacial, se han utilizado diversas tecnologías, que incluyen la resonancia magnética funcional (fMRI), imágenes con marcadores sensibles al voltaje o registros electrofisiológicos de alto conteo de sensores. Sin embargo, la resolución temporal del fMRI y los métodos ópticos se limita típicamente a unos pocos hercios, casi tres órdenes de magnitud por debajo de la de los potenciales de acción, y se limitan a condiciones en los que el sujeto se encuentra inmóvil. Por otro lado, los registros electrofisiológicos basados en matrices de microelectrodos proporcionan una alta resolución espacio-temporal, lo que permite detectar con precisión dinámicas rápidas de cientos de neuronas individuales simultáneamente en animales que se mueven libremente. Sin embargo, las interfaces de detección neuroelectrónica presentan una limitación en el producto entre la resolución espacial y el área de cobertura. Además, presentan una baja sensibilidad en la banda de frecuencia infra-lenta (<0.5Hz), que está relacionada con la conectividad funcional de largo alcance. En esta tesis se presenta una nueva tecnología basada en sensores activos de grafeno, que permite incrementar el área de cobertura y la resolución espacial de los registros electrofisiológicos conservando una alta sensibilidad en una amplia banda de frecuencia, desde la actividad infra-lenta hasta la de una sola célula electrogénica. Este desarrollo tecnológico se divide en tres etapas principales; en primer lugar, se obtiene una comprensión más profunda de las características intrínsecas del ruido y la respuesta en frecuencia de estos sensores basándose en el estado del arte en tecnología de sensores de grafeno. En la segunda etapa, se muestra un sistema cuasi-comercial basado en matrices de sensores de grafeno epi-cortical y transmisión inalámbrica para implantación crónica en ratas. Con este sistema, se demuestra la reproducibilidad de las matrices de sensores de grafeno, su estabilidad a largo plazo y su biocompatibilidad crónica. Además, se proporciona evidencia preliminar para una amplia gama de nuevos patrones electrofisiológicos debido a su sensibilidad en la banda de frecuencia infra-lenta. Finalmente, en la última etapa de esta tesis, el enfoque se centra en el desarrollo de nuevas estrategias de multiplexación para aumentar el número de sensores en las sondas neuronales. Estas tres etapas principales de desarrollo han llevado a la demostración del potencial de las matrices de sensores de grafeno multiplexados para el mapeado de las dinámicas neuronales a gran escala en una amplia banda de frecuencia en animales que se mueven libremente durante largos períodos. La combinación de estas capacidades hace que las matrices de sensores activos de grafeno sean una tecnología prometedora para interfaces cerebro-ordenador de alto ancho de banda y una herramienta única para investigar el papel de la actividad infra-lenta en la coordinación de las dinámicas neuronales de alta frecuencia.
Brain function is based on highly complex processes, which remain yet to be described and understood in detail. In the last decades, neuroscience has experienced an accelerated development, prompted by novel neurotechnologies that allow monitoring the dynamics of electrical activity in the brain with a higher spatio-temporal resolution and wider coverage area. However, due to the high complexity of neural networks in the brain, which are composed of strongly interconnected neural populations across large brain regions, we are far from monitoring a significant fraction of neurons mediating complex functions. In order to investigate large-scale brain dynamics with high spatial resolution several technologies have been extensively used, including functional magnetic resonance imaging (fMRI), voltage-sensitive dye imaging or high sensor-count electrophysiological recordings. However, the temporal resolution of fMRI and optical methods is typically limited to few hertz, almost three orders of magnitude below that of action potentials, and are limited to head-fixed conditions. On the other hand, electrophysiological recordings based on micro-electrode arrays provide a high spatio-temporal resolution, allowing to accurately detect fast dynamics from hundreds of individual neurons simultaneously in freely moving animals. However, neuroelectronic sensing interfaces present a trade-off between spatial resolution and coverage area. Moreover, they present a poor sensitivity in the infra-slow frequency band ($<0.5$\,$Hz$), which is related to long-range functional connectivity. In this thesis, a novel technology based on graphene active sensors is presented, which allows to increase the coverage area and spatial resolution of electrophysiological recordings while preserving a high sensitivity in a wide frequency band, from infra-slow to single electrogenic cell activity. This technological development is divided into three main stages; first, a deeper understanding of the intrinsic noise characteristics and frequency response of these sensors is obtained by building on prior graphene sensor technology. In the second stage, a quasi-commercial system based on epi-cortical graphene sensor arrays and a wireless headstage for chronic implantation in rats is shown. Using this system, the reproducibility of the graphene sensor arrays, their long-term stability and their chronic biocompatibility are demonstrated. Furthermore, preliminary evidence is provided for a wide range of novel electrophysiological patterns owing to their sensitivity in the infra-slow frequency band. Finally, in the last stage of this thesis, the focus is centred on the development of new multiplexing strategies to upscale the number of sensors on the neural probes. These three main development stages have led to the demonstration of the potential of multiplexed graphene sensor arrays for mapping of large-scale brain dynamics in a wide frequency band in freely moving animals over long periods. The combination of these capabilities makes graphene active sensor arrays a promising technology for high bandwidth brain computer interfaces and a unique tool to investigate the role of infra-slow activity on the coordination of higher frequency brain dynamics.
Universitat Autònoma de Barcelona. Programa de Doctorat en Enginyeria Electrònica i de Telecomunicació

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.
Includes bibliographical references (p. 124-129).
In this dissertation, we propose a new architecture for Internet congestion control that decouples the control of congestion from the bandwidth allocation policy. We show that the new protocol, called XCP, enables very large per-flow throughput (e.g., more than 1 Gb/s), which is unachievable using current congestion control. Additionally, we show via extensive simulations that XCP significantly improves the overall performance, reducing drop rate by three orders of magnitude, increasing utilization, decreasing queuing delay, and attaining fairness in a few RTTs. Using tools from control theory, we model XCP and demonstrate that, in steady state, it is stable for any capacity, delay, and number of sources. XCP does not maintain any per-flow state in routers and requires only a few CPU cycles per packet making it implementable in high-speed routers. Its flexible architecture facilitates the design and implementation of quality of service, such as guaranteed and proportional bandwidth allocations. Finally, XCP is amenable to gradual deployment.
by Dina Katabi.
Ph.D.

In our technological society, the growth of applications is not always followed by the growth of network capacity. There is an increasing demand of bandwidth which cannot always be answered properly. It is especially true in wireless networks such as 3G. Mobile devices can store and use more and more applications which are all using the bandwidth without any control. The Internet experience for the end user can thus be quickly degraded. In this respect, my objective in this thesis is to fill the gap on this matter by implementing a traffic shaping software working on Android devices. In order to get the necessary knowledge to create such an application, series of tests are conducted on similar software based on Windows 7. The outcome of this research is my own solution to shape the traffic on Android mobile devices. The software allows the end user to choose which of his applications should get a higher priority to improve his overall experience with them.

Thesis (M.S. in Systems Technology (Joint Command, Control, Communications, Computers and Intelligence (JC4I))--Naval Postgraduate School, June 2005.
Thesis Advisor(s): William Kemple, John Osmundson. Includes bibliographical references (p. 59-60). Also available online.

In kernel density estimation, the most crucial step is to select a proper bandwidth (smoothing parameter). There are two conceptually different approaches to this problem: a subjective and an objective approach. In this report, we only consider the objective approach, which is based upon minimizing an error, defined by an error criterion. The most common objective bandwidth selection method is to minimize some squared error expression, but this method is not without its critics. This approach is said to not perform satisfactory in the tail(s) of the density, and to put too much weight on observations close to the mode(s) of the density. An approach which minimizes an absolute error expression, is thought to be without these drawbacks. We will provide a new explicit formula for the mean integrated absolute error. The optimal mean integrated absolute error bandwidth will be compared to the optimal mean integrated squared error bandwidth. We will argue that these two bandwidths are essentially equal. In addition, we study data-driven bandwidth selection, and we will propose a new data-driven bandwidth selector. Our new bandwidth selector has promising behavior with respect to the visual error criterion, especially in the cases of limited sample sizes.

Chip Multiprocessors (CMP) are an increasingly popular architecture and increasing numbers of vendors are now offering CMP solutions. The shift to CMP architectures from uniprocessors is driven by the increasing complexity of cores, the processor-memory performance gap, limitations in ILP and increasing power requirements. Prefetching is a successful technique commonly used in high performance processors to hide latency. In a CMP, prefetching offers new opportunities and challenges, as current uniprocessor heuristics will need adaption or redesign to integrate with CMPs. In this thesis, I look at the state of the art in prefetching and CMP architecture. I conduct experiments on how unmodified uniprocessor prefetching heuristics perform in a CMP. In addition, I have proposed a new prefetching scheme based on bandwidth monitoring and prediction through performance counters, suited for embedded CMP systems. This new prefetching scheme has been simulated with SimpleScalar. It offers lower bandwidth usage (up to 47.8 %), while retaining most of the performance gains from prefetching for low accuracy prefetching heuristics.

Telenor is faced with complex decisions regarding their access network strategies. Competitors are given the right to use Telenor’s copper access network through LLUB (Local Loop Un-Bundling) regulations. Competition is also seen from alternative access networks. Both implying lost customers and lost revenues. At the same time, the accumulated demand for bandwidth is increasing to a level beyond what can be accommodated by Telenor’s current access network. Failing to meet this demand will result in further lost revenues.This thesis uses the expected growth in bandwidth demand to motivate an upgrade of Telenor’s access network. Several schemes and technologies are considered. Finally three different solutions are chosen for an in-depth business case analysis. As part of this analysis, a set of models are created. These models can be used to calculate investment costs of an arbitrary area. The models are used on six different areas in and around Trondheim.New applications and services such as Peer-to-Peer, Streaming and Video-on-Demand are increasing the demand for bandwidth among home users. There is also a trend towards an access network convergence. Traditionally, basic services would have dedicated access networks. This is changing. The product called Triple Play (3P) is perhaps the best example. This is telephony, TV and Internet access all offered on one access network with one bill. Various fiber based solutions or an improvement of current xDSL technology are those options relevant to Telenor Nordic. A point-to-point (P2P) fiber solution, a passive optical network (PON) and a VDSL2 solution are chosen for a business case analysis. The two former solutions are considered capable of meeting long term demand. The latter solution is considered capable of meeting medium to long term demand. By applying the models created and using a Telenor GIS (Geographic Information System) tool for measurements, results are obtained. They indicate that a VDSL2 solution is the cheapest way of providing bit rates above 70 Mbit/s to all customers. In urban and sub-urban areas VDSL2 is approximately 50 % cheaper than fiber-based solutions. In rural areas, the difference between a PON solution and VDSL2 is reduced. A P2P solution remains the most expensive, but now by far. The net present value analysis show positive values for all solutions in urban and sub-urban areas. The rural areas seem unprofitable according to any standard.The presence of available fiber becomes a crucial factor in determining deployment costs for PONs. In the case of a P2P solution, existing available ducts are highly desirable. The fear of high deployment costs related to expensive civil work in urban areas, seem needless. The high population density and availability of existing infrastructure in these areas easily compensates expensive civil work.

This thesis addresses the problem of simultaneously transmitting several data signals across a single channel. For this purpose, a transmultiplexer that uses modulated filter banks is studied. Modulated filter banks comprise filters that are bandpass versions of a lowpass prototype. The filters serve to assign portions of the channel bandwidth to the data signals. The impulse responses of the filters are parameterized by a center frequency, delay and phase factor. The objectives in configuring modulated filter banks are to use the full channel bandwidth for transmission, cancel crosstalk between signals (arises when signals share bandwidth) and cancel intersymbol interference in each data signal. Assuming an ideal channel, a synthesis procedure is developed by assigning a bandwidth to the lowpass prototype and deriving relationships among the center frequencies, delays and phases such that the entire channel bandwidth is utilized and crosstalk is cancelled. New design procedures for an FIR lowpass prototype are proposed such that the intersymbol interference is suppressed. One design method is based on a minimax criterion. Another approach involves an unconstrained optimization of an error function.
The synthesis procedure leads to five bandwidth efficient transmultiplexers. Three of the systems implement multicarrier Quadrature Amplitude Modulation (QAM) and two accomplish multicarrier Vestigial Sideband Modulation (VSB). The performance of the five systems is compared with filters obtained by the new design approaches. Also, the issue of channel distortion is addressed. Finally, the transmultiplexers can be converted into new subband systems.

Telephone speech often sounds muffled and thin due to its narrowband characteristics. With the increased availability of terminals capable of receiving wideband signals, extending the bandwidth of narrowband telephone speech at the receiver has drawn much research interest. Currently, there exist many methods that can provide good reconstructions of the wideband spectra from narrowband speech; however, they often lack robustness to different channel conditions, and their performances degrade when they operate in unknown environments.
This thesis presents a bandwidth extension algorithm that mitigates the effects of adverse conditions. The proposed system is designed to work with noisy input speech and unknown channel frequency response. To maximize the naturalness of the reconstructed speech, the algorithm estimates the channel and applies equalization to recover the attenuated bands. Artifacts are reduced by employing an adaptive and a fixed postfilter.
Subjective test results suggest that the proposed scheme is not affected by channel conditions and is able to produce speech with enhanced quality in adverse environments.

Hastily Formed Networks (HFNs) are typically deployed in resource constrained environments. Clients operating within HFNs have inadvertently utilized excessive bandwidth without user interaction. Our research focuses on managing bandwidth usage in resource constrained networks through the use of DNS Tampering, a method of content filtering. We evaluate two operating systems, Windows XP and Windows 7, and analyze how it may be possible to limit operating system updates utilizing DNS Tampering. We then explore how it may be possible to implement this technique utilizing equipment available for an HFN. Through our efforts, we develop and set forth specific methodologies that can provide the opportunity to limit bandwidth usage for specific applications in resource constrained networks.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 189-197).
An ultra wide-bandwidth resonating thin film PZT MEMS energy harvester has been designed, modeled, fabricated and tested. It harvests energy from parasitic ambient vibration at a wide range of amplitude and frequency via piezoelectric effect. At the present time, the designs of most piezoelectric energy devices have been based on high-Q linear cantilever beams that use the bending strain to generate electrical charge via piezoelectric effect. They suffer from very small bandwidth and low power density which prevents them from practical use. Contrarily, the new design utilizes the tensile stretching strain in doubly-anchored beams. The resultant stiffness nonlinearity due to the stretching provides a passive feedback and consequently a wide-band resonance. This wide bandwidth of resonance enables a robust power generation amid the uncertainty of the input vibration spectrum. The device is micro-fabricated by a combination of surface and bulk micro-machining processes. Released devices are packaged, poled and electro-mechanically tested to verify the wide-bandwidth nonlinear behavior of the system. Two orders of magnitude improvement in bandwidth and power density is demonstrated by comparing the frequency response of the system with that of an equivalent linear harvester with a similar Q-factor.
by Arman Hajati.
Ph.D.

Laser Doppler Blood Flowmetry (LDBF) has for several decades been applied to measure the flow of red blood cells in living tissue. Laser Doppler Perfusion Imaging (LDPI), a recent advancement which enables full-field blood flow visualisation, is gaining clinical acceptance in fields such as burn diagnostics. However, video-rate full-field imagers with appropriate sensor and processing capability require large financial and physical resources and this has prompted the development of under-specified systems. These systems may reduce the bandwidth and processing complexity but the question of how they perform compared to their fully specified counterparts remains. The advantages of these cheaper and often highly reconfigurable systems are recognised and so it is beneficial to ask whether any novel processing schemes can reduce the resultant error. Here a reduced bandwidth LDBF signal processing system has been modelled. Bayesian Inference has been used to show that the Pareto distribution is a likely model for the LDBF power spectrum, despite often being cited as exponential. Methods of evaluating microvascular blood flow have been described and compared. Additionally, one fast algorithm's effectiveness has been explained, and a novel and accurate method using the Hilbert transform has been presented. By understanding how aliasing modifies the frequency distribution, Bayesian Inference has been used to correct the blood flow output towards gold-standard values. The technique has been shown to correct the output of a low bandwidth CMOS camera imaging a rotating diffuser. Low bandwidth LDPI systems may be suitable for certain clinical applications where sensitivity to high flow is not required. However, where sensitivity to higher flow than baseline is required, e.g. in burn diagnostics, low bandwidth systems may underestimate the true blood flow leading to misdiagnosis. Nevertheless, low bandwidth systems could be used in this scenario if reliable post-processing is employed, such as that suggested by this thesis.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada
The national telemetry ranges are being pushed to provide higher data rate telemetry services by users with increasingly complex test procedure for increasingly complex weapon systems. At the same time they are having trouble obtaining more spectrum in which to provide these higher rates because of the demand for spectrum in SHF range from various mobile/cellular Personal Communications Services (PCS) as well as congress’s desire to auction spectrum and to transfer as much spectrum as possible to commercial uses. In light of these pressures the industry is in need of a modulation standard that will out perform the existing PCM/FM standard. The motivation for the present review and analysis of the performance of various coded/uncoded modulation schemes arises from this issue. Comparison of the performance of these schemes will be utilized in the following work to find a suitable solution to the existing problem.

This thesis describes the development of a psychoacoustically optimised bandwidth limitation method for multichannel audio. The proposed method takes advantages from the hierarchical representation of multichannel audio signals. Several hierarchical transform techniques were reviewed and their applicability to be used in the proposed hierarchical bandwidth limitation method were verified using psychoacoustical studies. The Karhunen-Loeve Transform (KLT) outperformed other hierarchical transform techniques due to its ability of rearranging the information in a perceptually hierarchical manner. Another advantage of KLT is that the transform matrices are signal-content-dependent and are adaptive to the actual spatial characteristics of audio material. The perceptual effects of the adaptive KLT-based hierarchical bandwidth limitation were studied. The results showed that applying KLT to short-term multichannel audio signals and updating the KLT transform matrices adaptively over time will result in better audio quality compared with non-adaptive KLT for those multichannel audio programmes that had significantly varying statistical characteristics over time. In addition, the bandwidth allocation strategy in KLT-based hierarchical bandwidth limitation was optimised for 3/2 stereo format for two levels of overall bandwidth: 40 and 60 kHz. An evaluation has been made of the optimised KLT-based hierarchical bandwidth limitation algorithm by comparing it with other bandwidth limitation algorithms. The results showed that the KLT-based hierarchical bandwidth limitation with the optimal bandwidth allocation strategy provided higher audio quality than the other traditional bandwidth limitation algorithms used for the limitation of bandwidth of multichannel sound.

Includes bibliographical references.
This thesis investigates bandwidth allocation methodologies to transport new emerging bursty traffic types in ATM networks. However, existing ATM traffic management solutions are not readily able to handle the inevitable problem of congestion as result of the bursty traffic from the new emerging services. This research basically addresses bandwidth allocation issues for bursty traffic by proposing and exploring the concept of dynamic bandwidth allocation and comparing it to the traditional static bandwidth allocation schemes.

Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 107-109).
Contact-less, three-dimensional scanning is a highly important field for the semiconductor industry. By using a system of high-bandwidth impedance sensors and drive electronics, the physical constituents of ICs such as buried/surface dielectrics, buried/surface conductors and PN junctions could be detected. This thesis takes an initial step toward high-bandwidth electroquasistatic (EQS) imaging by exploring the use of high-frequency imaging. When combined with impedance sensors having a high spatial density, it could be possible to develop a very-high-bandwidth scanning imaging system. The system explored here uses a capacitively-coupled electrode array in order to distinguish various features such as a dielectric layer or a variable air gap based on measured electrode impedance. The frequency at which the impedance is measured is near 500 MHz. Also, this system can be potentially used to image depth information and dielectric composition by using multi-wavelength electrode arrays. This thesis presents the selection and layout for the high-speed drive electronics and the construction and modeling of the driven electrode arrays. Validation experiments to illustrate capacitive sensing ability are also performed. The system is able to identify surface topography, distinguish surface dielectrics from metals, and discern changes in bulk conductivity.
by Rakesh Kumar.
S.M.

Smartphones now account for the majority of all cell phones in use today [23]. Ubiquitous Internet access is a valuable feature offered by these devices and the vast majority of smartphone applications make use of the Internet in one way or another. However, the bandwidth offered by these cellular networks is often much lower than we typically experience on our standard home networks, leading to a less-than-optimal user experience. This makes it very challenging and frustrating to access certain types of web content such as video streaming, large file downloads, loading large webpages, etc. Given that most modern smartphones are multi-homed and are capable of ac- cessing multiple networks simultaneously, this thesis attempts to utilize all available network interfaces in order to achieve the aggregated bandwidth of each to improve the overall network performance of the phone. To do so, I implement a bandwidth aggregation system for iOS that combines the bandwidths of multiple devices located within close proximity of each other. Deployed on up to three devices, speedups of up to 1.82x were achieved for downloading a single, 10mb file. Webpage loading saw speedups of up to 1.55x.

With the advent of bandwidth-hungry video and audio applications, demand for bandwidth is expected to exceed supply. Users will require more bandwidth and, as always, there are likely to be more users. As the Internet user base becomes more diverse, there is an increasing perception that Internet Service Providers (ISPs) should be able to differentiate between users, so that the specific needs of different types of users can be met. Differentiated services is seen as a possible solution to the bandwidth problem. Currently, however, the technology used on the Internet differentiates neither between users, nor between applications. The thesis focuses on current and anticipated bandwidth shortages on the Internet, and on the lack of a differentiated service. The aim is to identify methods of managing bandwidth and to investigate how these bandwidth management methods can be used to provide a differentiated service. The scope of the study is limited to networks using both Ethernet technology and the Internet Protocol (IP). Tile study is significant because it addresses current problems confronted by network managers. The key terms, Quality of Service (QoS) and bandwidth management, are defined. “QoS” is equated to a differentiating system. Bandwidth management is defined as any method of controlling and allocating bandwidth. "Installing more capacity" is taken to be a method of bandwidth management. The review of literature concentrates on Ethernet/IP networks. It begins with a detailed examination of definitions and interpretations of the term "Quality of Service" and shows how the meaning changed over the last decade. The review then examines congestion control, including a survey of queuing methods. Priority queuing implemented in hardware is examined in detail, followed by a review of the ReSource reserVation Protocol (RSVP) and a new version of IP (lPv6). Finally, the new standards IEEE 802.1p and IEEE 802.1Q are outlined, and parts of ISO/IEC 15802-3 are analysed. The Integrated Services Architecture (ISA), Differentiated Services (DiffServ) and MultiProtocol Label Switching (MPLS) are seen as providing a theoretical framework for QoS development. The Open Systems Interconnection Reference Model (OSI model) is chosen as the preferred framework for investigating bandwidth management because it is more comprehensive than the alternative US Department of Defence Model (DoD model). A case study of the Edith Cowan University (ECU) data network illustrates current practice in network management. It provides concrete examples of some of the problems, methods and solutions identified in the literary review. Bandwidth management methods are identified and categorised based on the OSI layers in which they operate. Suggestions are given as to how some of these bandwidth management methods are, or can be used within current QoS architectures. The experimental work consists of two series of tests on small, experimental LANs. The tests are aimed at evaluating the effectiveness of IEEE 802.1 p prioritisation. The results suggest that in small Local Area Networks (LANs) prioritisation provides no benefit when Ethernet switches are lightly loaded.

Thesis (M.S. in Engineering Acoustics) Naval Postgraduate School, March 2001.
Thesis advisor(s): Smith, Kevin B. ; Nagle, Daniel T. "March 2001." Includes bibliographical references (p. 39-40). Also Available in print.

This thesis reports the development of a wide-bandwidth high-sensitivity mode-decoupled MEMS gyroscope showing robustness against ambient pressure variations. The designed gyroscope is based on a novel 2 degrees of freedom (DoF) sense mode oscillator, which allows increasing the operation bandwidth to the amount required by tactical-grade and inertial-grade operations while reaching the mechanical sensitivity of near matched-mode vibratory gyroscopes. Thorough theoretical study and finite element simulations verify the high performance operation of the proposed 2 DoF sense mode oscillator design. The designed gyroscope is fabricated using the in-house developed silicon-on-glass (SOG) micromachining technology at METU Microelectronics (METU-MET) facilities. The fabricated gyroscope measures only 5.1 x 4.6 mm square. The drive mode oscillator of the gyroscope reaches quality factor of 8760 under 25 mTorr vacuum environment, owing to high quality single crystal silicon structural layer. The sense mode bandwidth is measured to reach 2.5 kHz at 40 V proof mass voltage. When the fabricated gyroscope is operated with a relatively wide bandwidth of 1kHz, measurements show a relatively high raw mechanical sensitivity of 131 uV/(deg/s). Fabricated gyroscope is hybrid connected to external closed-loop drive mode amplitude control and open-loop sense mode readout electronics developed at METU-MEMS research group, to form a complete angular rate measurement system (ARMS). The scale factor of the ARMS is measured to be 13.1 mV/(deg/s) with a maximum R square nonlinearity of 0.0006 % and a maximum percent deviation nonlinearity of 0.141 %, while the maximum deviation of the scale factor for large vacuum level variations between 40 mTorr to 500 mTorr is measured to be only 0.38 %. The bias stability and angle random walk of the gyroscope are measured to be 131 deg/h and 1.15 deg/ rooth, respectively. It is concluded that, the mechanical structure can be optimized to show its theoretical limits of sensitivity with improvements in fabrication tolerances. The proposed 2 DoF sense mode oscillator design shows the potential of tactical-grade operation, while demonstrating extreme immunity to ambient pressure variations, by utilizing an optimized mechanical structure and connecting the gyroscope to dedicated low-noise electronics.

Authentication, authorization, and accounting (AAA) are key elements in network security. In many networks, clients can use resources only after they have been authenticated by an authentication server and authorized to use these resources. In some cases the server will also maintain accounting records in order for an operator (a provider of resources) to charge the account/subscriber for using the service. There are four main AAA protocols being used today. Of these RADIUS is the mostly widely used. This thesis starts with an introduction to AAA protocols, and then goes in the details of RADIUS. In order to perform a practical evaluation of how the AAA could be improved, FreeRADIUS was selected as the base code for this project; because this implementation is one of the most widely used RADIUS servers. A proposal for how to improve AAA performance is introduced and the implementation steps needed to realize these improvements are shown. Additionally, some experiments have been conducted to show both the correct functioning of the resulting implementation and to examine if there is a performance improvement. Following this some conclusions are drawn based upon a comparison with a traditional AAA server. A key element of the change in AAA which is proposed is the use of a non-binary IEEE 802.1x process. This new non-binary solution introduces a new type of AAA server and requires the re-thinking of a number of traditional AAA design decisions. It is expected that this change will have a significant impact, but will require some time for exposure, implementation by others, and a more extensive evaluation that was possible during the period of this thesis project. One of the most important conclusions drawn during this thesis is the difficulty of making a change in authentication and authorization, because of the large amount of interaction between both the various protocols and the standards which have been developed for these protocols. Thus one of the difficult aspects of the task is how to introduce a change in a protocol while maintaining backward compatibility for others who have not adopted this change -- without requiring the addition of a protocol version field. A second important conclusion is that doing this implementation in three separate parts with different students being responsible for the different parts revealed just how complex the interaction of protocol design decisions are. While a working version of the entire set of changes proved to be impossible, it was observed that the different parts could be decoupled more than initially expected.

This thesis studies the modulation and coding aspects of bandwidth efficient direct-sequence CDMA systems. The novel concepts proposed and investigated are: DS-CDMA employing combined modulation schemes; MFSK/DS-CDMA employing orthogonal codes; and DS-CDMA employing permutation modulation. Under each concept, one or more schemes are developed and examined. The first concept suggests that two or more modulation schemes can be considered together as a combined modulation in a DS-CDMA system. By combining two modulation schemes, the signal energy per symbol for a given bit energy is increased. This in turn increases the system power efficiency and also the bandwidth efficiency. By combining MFSK and MPSK, we proposed the MFSK-MPSK/DS-CDMA scheme. By combining MFSK and differential MPSK, we proposed the MFSK-DMPSK/DS-CDMA scheme. The second concept can be thought of as an application of the first. By combining MFSK and the orthogonal PN codes, we proposed the MFSK-OC/DS-CDMA scheme. It is found in this thesis that the orthogonal code concept has many significant applications in both performance improvement and complexity reduction in DS-CDMA systems. An analysis also shows that the ideal orthogonality of the codes can be relaxed with very little performance degradation. Thus, quasi-orthogonal codes can be used in practical applications. In the third concept, permutation modulation is applied to the DS-CDMA systems and it is proved to be a very powerful scheme in fading channels. By using the multi-tone FSK scheme, we proposed the MT-FSK/DS-CDMA system. In a fading channel, this system introduces an implicit diversity, and thus is robust in mobile environments. The concept of orthogonal codes are used here to reduce the implementation complexity. By using a simple frequency tone selection rule, we further proposed a novel scheme, namely OMT-FSK/DS-CDMA in which all symbols are orthogonal each other. For the proposed schemes, performance analyses are made over AWGN and fading channels with and without FEC coding. Computer simulation is done for the MFSK-OC/DS-CDMA and MT-FSK/DS-CDMA systems.

碩士
國立嘉義大學
資訊工程研究所
91
The bandwidth of a graph is the minimum of the maximum difference between labels of adjacent vertices in the graph. Bandwidth of graphs is an useful parameter for many applications including solving linear equations, parallel computation network, VLSI layout problem, back tracing in the constraint satisfaction problem etc. If we label the edges instead of the vertices of the graph, we can define the edge-bandwidth accordingly. The edge-bandwidth of a graph is the minimum of the maximum difference between labels of adjacent edges in the graph. The edge-bandwidth problem is a restricted version of the bandwidth problem. Establishing the bandwidth of a line graph is equivalent to verifying the edge-bandwidth of one or more graphs. However, the computing complexity of the edge-bandwidth is unknown up to now. Another parameter which is related to bandwidth is called cyclic bandwidth of a graph. The application about the cyclic bandwidth is also in the area of parallel computation network and VLSI layout. It is known that the decision problems corresponding to finding the bandwidth and the cyclic bandwidth of an arbitrary graph are NP-complete. In this thesis we solved bandwidth, edge-bandwidth and cyclic bandwidth for some classes of graphs with extensive proof.

碩士
國立東華大學
應用數學系
92
Given a graph G with V (G) = n and a set S contained in N, S = n, a proper S-labeling of G is a one to one function from V (G) to S. If f is a proper S-labeling of G, we define the S-bandwidth of G with respect to f to be the number B_f (G; S) =max{ f (u) − f (v) uv belongs to E(G)}, and define the S-bandwidth of G by B(G; S) = min_f(B_f (G; S)) When V (G) = n and S = {1, 2, · · · , n}, we use B(G) in place of B(G; S) and call it the bandwidth of G. We study the S-bandwidth and bandwidth problem of graphs in this thesis. We find some relations between the S-bandwidth of a graph G and the bandwidth of the join of two graphs, and use it to find B(G), when G = G1 + G2. We also study the bandwidth of a graph G, when G is a multiplication of a path.