Downstream Bandwidth Management for Emerging DOCSIS-based Networks

In this dissertation, we consider the downstream bandwidth management in the context of emerging DOCSIS-based cable networks. The latest DOCSIS 3.1 standard for cable access networks represents a significant change to cable networks. For downstream, the current 6 MHz channel size is replaced by a much larger 192 MHz channel which potentially can provide data rates up to 10 Gbps. Further, the current standard requires equipment to support a relatively new form of active queue management (AQM) referred to as delay-based AQM. Given that more than 50 million households (and climbing) use cable for Internet access, a clear understanding of the impacts of bandwidth management strategies used in these emerging networks is crucial. Further, given the scope of the change provided by emerging cable systems, now is the time to develop and introduce innovative new methods for managing bandwidth. With this motivation, we address research questions pertaining to next generation of cable access networks. The cable industry has had to deal with the problem of a small number of subscribers who utilize the majority of network resources. This problem will grow as access rates increase to gigabits per second. Fundamentally this is a problem on how to manage data flows in a fair manner and provide protection. A well known performance issue in the Internet, referred to as bufferbloat, has received significant attention recently. High throughput network flows need sufficiently large buffer to keep the pipe full and absorb occasional burstiness. Standard practice however has led to equipment offering very large unmanaged buffers that can result in sustained queue levels increasing packet latency. One reason why these problems continue to plague cable access networks is the desire for low complexity and easily explainable (to access network subscribers and to the Federal Communications Commission) bandwidth management. This research begins by evaluating modern delay-based AQM algorithms in downstream DOCSIS 3.0 environments with a focus on fairness and application performance capabilities of single queue AQMs. We are especially interested in delay-based AQM schemes that have been proposed to combat the bufferbloat problem. Our evaluation involves a variety of scenarios that include tiered services and application workloads. Based on our results, we show that in scenarios involving realistic workloads, modern delay-based AQMs can effectively mitigate bufferbloat. However they do not address the other problem related to managing the fairness. To address the combined problem of fairness and bufferbloat, we propose a novel approach to bandwidth management that provides a compromise among the conflicting requirements. We introduce a flow quantization method referred to as adaptive bandwidth binning where flows that are observed to consume similar levels of bandwidth are grouped together with the system managed through a hierarchical scheduler designed to approximate weighted fairness while addressing bufferbloat. Based on a simulation study that considers many system experimental parameters including workloads and network configurations, we provide evidence of the efficacy of the idea. Our results suggest that the scheme is able to provide long term fairness and low delay with a performance close to that of a reference approach based on fair queueing. A further contribution is our idea for replacing `tiered\u27 levels of service based on service rates with tiering based on weights. The application of our bandwidth binning scheme offers a timely and innovative alternative to broadband service that leverages the potential offered by emerging DOCSIS-based cable systems

Mass and Charge Transport in Hydrated Polymeric Membranes

Mass and charge transport through hydrated polymer membranes has significant importance for many areas of engineering and industry. Multi-scale modeling and simulation techniques were used to study transport in relation to two specific membrane applications: (1) food packaging and (2) additives for polymer electrolytes. Chitosan/chitin films were studied due to their use as a sustainable, biodegradable food packaging film. The effects of hydration on the solvation, diffusivity, solubility, and permeability of oxygen molecules in these films were studied via molecular dynamics and confined random walk simulations. With increasing hydration, the membrane was observed to have a more homogeneous water distribution with the polymer chains being fully solvated. Insight from this work will help guide molecular modeling of chitosan/chitin membranes and experimental synthesis of these membranes, specifically highlighting efforts to chemically tailor chitosan membranes to favor discrete as opposed to continuous aqueous domains to help reduce oxygen permeability. Additives for proton exchange membranes (PEMs) were studied to aid in the developing next-generation membrane materials for fuel cell applications. We calculate and present predictions of our analytical model that describes the fundamental relationship between the nanoscale structure of PEMs and their proton conductivity using a set of structural descriptors, accounting for nanopore size, functionalization and connectivity in order to predict proton conductivities in PEMs. The model reproduces experimentally determined conductivities in two current PEM materials. To extend the model based on structural descriptors of PEMs, we studied polyethylene glycol (PEG), a polymer used in electrochemistry applications due to it hydrophilicity and pH-dependent behavior in aqueous environments. We conducted ab initio molecular dynamics simulations of an excess proton in bulk water and aqueous triethylene glycol (TEG) solution and reactive molecular dynamics simulations of an excess proton in bulk water, aqueous TEG solution, and aqueous PEG solution. We determined differences in protonic defect structures, kinetics, thermodynamics, and hydrogen-bond networks associated with structural diffusion between systems. Driving forces for polymeric membrane design goals include economics, efficiency, energy consumption and sustainable production. Insight from this work hopes to aid in determining key design parameters and reduce time-to-discovery for developing next-generation polymeric membranes

Photochemical and photophysical reaction dynamics of chemical and biological systems

Texto en inglés, y resumen y conclusiones en inglés y españolEl proyecto realizado en esta Tesis consiste en el desarrollo y aplicación de metodologías teóricas y computaciones, usadas en la descripción estática y dinámica de procesos fotofísicos y fotoquímicos de compuestos químicos y de interés biológico. Estas metodologías computacionales fueron implementadas aplicando técnicas punteras usadas en el campo de la ciencia de la computación. La presente Tesis se compone de 4 bloques principales. El primero de estos bloques estudia el proceso de transferencia de energía intermolecular, especialmente transferencia de energía triplete. Por su parte, el segundo bloque examina los mecanismos y comportamiento dinámico de dos procesos biológicos fotoinducidos de intereses tecnológico. Mientras el tercer bloque, consiste en el estudio del efecto de fuerzas externas sobre las propiedades espectroscópicas de los sistemas moleculares. Finalmente, el último bloque considera el diseño de dispositivos moleculares que usan cambios conformacionales fotoinducidos en la generación de movimiento controlado. En la sección de transferencia de energía ha sido estudiado el problema de encontrar las principales coordenadas moleculares que modulan de forma eficiente el proceso de transferencia de energía triplete. Así mismo, se llevó a cabo una aproximación dinámica al proceso de transferencia energía triplete a temperatura constante, que completa el estudio estático llevado a cabo en la primera parte de la sección. En la primer parte del segundo bloque, se lleva a cabo la caracterización estática y dinámica de modelos moleculares en el estudio de los fenómenos de quimioluminiscencia y bioluminiscencia. Donde se analiza en detalle el mecanismo de descomposición concertado de la familia de 1,2-dioxetanes. Por su parte, en la segunda sección de este bloque es analizado el efecto del ambiente proteico en la emisión de fluorescencia de la proteína fluorescente IrisFP. En el tercer bloque de la presente Tesis ha sido explorado la respuesta fotodinámica de sistemas moleculares al efecto de una fuerza externa. Discutiendo en detalle el efecto sobre el cambio de la reactividad química a causa de la disrupción del sistema molecular por parte de la fuerza externa. Simultáneamente, se muestran los resultados obtenidos con respecto al cambio en las propiedades espectroscópicas debidos a la fuerza externa y se plantea su posible aprovechamiento en aplicaciones tecnológicas Finalmente en el último bloque del presente trabajo, se expone el diseño y operación de dispositivos moleculares como motores e interruptores controlados mediante ciclos fotoinducidos, controlado la rotación unidireccional en el caso de los motores moleculares a través de puentes de hidrógenos

Photochemical and photophysical reaction dynamics of chemical and biological systems

Texto en inglés, y resumen y conclusiones en inglés y españolEl proyecto realizado en esta Tesis consiste en el desarrollo y aplicación de metodologías teóricas y computaciones, usadas en la descripción estática y dinámica de procesos fotofísicos y fotoquímicos de compuestos químicos y de interés biológico. Estas metodologías computacionales fueron implementadas aplicando técnicas punteras usadas en el campo de la ciencia de la computación. La presente Tesis se compone de 4 bloques principales. El primero de estos bloques estudia el proceso de transferencia de energía intermolecular, especialmente transferencia de energía triplete. Por su parte, el segundo bloque examina los mecanismos y comportamiento dinámico de dos procesos biológicos fotoinducidos de intereses tecnológico. Mientras el tercer bloque, consiste en el estudio del efecto de fuerzas externas sobre las propiedades espectroscópicas de los sistemas moleculares. Finalmente, el último bloque considera el diseño de dispositivos moleculares que usan cambios conformacionales fotoinducidos en la generación de movimiento controlado. En la sección de transferencia de energía ha sido estudiado el problema de encontrar las principales coordenadas moleculares que modulan de forma eficiente el proceso de transferencia de energía triplete. Así mismo, se llevó a cabo una aproximación dinámica al proceso de transferencia energía triplete a temperatura constante, que completa el estudio estático llevado a cabo en la primera parte de la sección. En la primer parte del segundo bloque, se lleva a cabo la caracterización estática y dinámica de modelos moleculares en el estudio de los fenómenos de quimioluminiscencia y bioluminiscencia. Donde se analiza en detalle el mecanismo de descomposición concertado de la familia de 1,2-dioxetanes. Por su parte, en la segunda sección de este bloque es analizado el efecto del ambiente proteico en la emisión de fluorescencia de la proteína fluorescente IrisFP. En el tercer bloque de la presente Tesis ha sido explorado la respuesta fotodinámica de sistemas moleculares al efecto de una fuerza externa. Discutiendo en detalle el efecto sobre el cambio de la reactividad química a causa de la disrupción del sistema molecular por parte de la fuerza externa. Simultáneamente, se muestran los resultados obtenidos con respecto al cambio en las propiedades espectroscópicas debidos a la fuerza externa y se plantea su posible aprovechamiento en aplicaciones tecnológicas Finalmente en el último bloque del presente trabajo, se expone el diseño y operación de dispositivos moleculares como motores e interruptores controlados mediante ciclos fotoinducidos, controlado la rotación unidireccional en el caso de los motores moleculares a través de puentes de hidrógenos

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

The LHCb Upgrade I

The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

The LHCb Upgrade I

The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

Technology 2000, volume 1

The purpose of the conference was to increase awareness of existing NASA developed technologies that are available for immediate use in the development of new products and processes, and to lay the groundwork for the effective utilization of emerging technologies. There were sessions on the following: Computer technology and software engineering; Human factors engineering and life sciences; Information and data management; Material sciences; Manufacturing and fabrication technology; Power, energy, and control systems; Robotics; Sensors and measurement technology; Artificial intelligence; Environmental technology; Optics and communications; and Superconductivity

Design Methods and Tools for Application-Specific Predictable Networks-on-Chip

As the complexity of applications grows with each new generation, so does the demand for computation power. To satisfy the computation demands at manageable power levels, we see a shift in the design paradigm from single processor systems to Multiprocessor Systems-on-Chip (MPSoCs). MPSoCs leverage the parallelism in applications to increase the performance at the same power levels. To further improve the computation to power consumption ratio, MPSoCs for embedded applications are heterogeneous and integrate cores that are specialized to perform the different functionalities of the application. With technology scaling, wire power consumption is increasing compared to logic, making communication as expensive as computation. Therefore customizing the interconnect is necessary to achieve energy efficiency. Designing an optimal application specific Network-on-Chip (NoC), that meets application demands, requires the exploration of a large design space. Automatic design and optimization of the NoC is required in order to achieve fast design closure, especially for heterogeneous MPSoCs. To continue to meet the computation requirements of future applications new technologies are emerging. Three dimensional integration promises to increase the number of transistors by stacking multiple silicon layers. This will lead to an increase in the number of cores of the MPSoCs resulting in increased communication demands. To compensate for the increase in the wire delay in new technology nodes as well as to reduce the power consumption further, multi-synchronous design is becoming popular. With multiple clock signals, different parts of the MPSoC can be clocked at different frequencies according to the current demands of the application and can even be shutdown when they are not used at all. This further complicates the design of the NoC.Many applications require different levels of guarantee from the NoC in order to perform their functionality correctly. As communication traffic patterns become more complex, the performance of the NoC can no longer be predicted statically. Therefore designing the interconnect network requires that such guarantees are provided during the dynamic operation of the system which includes the interaction with major subsystems (i.e., main memory) and not just the interconnect itself. In this thesis, I present novel methods to design application-specific NoCs that meet performance demands, under the constraints of new technologies. To provide different levels of Quality of Service, I integrate methods to estimate the NoC performance during the design phase of the interconnect topology. I present methods and architectures for NoCs to efficiently access memory systems, in order to achieve predictable operation of the systems from the point of view of the communication as well as the bottleneck target devices. Therefore the main contribution of the thesis is twofold: scientific as I propose new algorithms to perform topology synthesis and engineering by presenting extensive experiments and architectures for NoC design