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Master of Science / Department of Electrical and Computer Engineering / Caterina M. Scoglio / Forecasting of network traffic plays a very important role in many domains such as congestion control, adaptive applications, network management and traffic engineering. Characterizing the traffic and modeling are necessary for efficient functioning of the network. A good traffic model should have the ability to capture prominent traffic characteristics, such as long-range dependence (LRD), self-similarity, and heavy-tailed distribution. Because of the persistent dependence, modeling LRD time series is a challenging task. In this thesis, we propose a non-linear time series model, Generalized AutoRegressive Conditional Heteroskedasticity (GARCH) of order p and q, with innovation process generalized to the class of heavy-tailed distributions. The GARCH model is an extension of the AutoRegressive Conditional Heteroskedasticity (ARCH) model, has been used in many financial data analysis. Our model is fitted on a real data from the Abilene Network which is a high-performance Internet-2 backbone network connecting research institutions with 10Gbps bandwidth links. The analysis is done on 24 hours data of three different links aggregated every 5 minutes. The orders are selected based on the minimum modified Akaike Information Criterion (AICC) using Introduction to Time Series Modeling (ITSM) tool. For our model the best minimum order was found to be (1,1). The goodness of fit is evaluated based on the Q-Q (t-distributed) plot and the ACF plot of the residuals and our results confirm the goodness of fit of our model. The forecast analysis is done using a simple one-step prediction. The first 24 hrs of the data set are used as the training part to model the traffic; the next 24 hrs are used for performing the forecast and the comparison. The actual traffic data and the predicted traffic data is compared to evaluate the performance of the model. Based on the prediction error the performance metrics are evaluated. A comparative study of GARCH model with other existing models is performed and our results confirms the simplicity and the better performance of our model. The complexity of the model is measured based on the number of parameters to be estimated. From this study, the GARCH model is found to have the ability to forecast aggregated traffic but further investigation need to be conducted on a less aggregated traffic. Based on the forecast model developed from the GARCH model, we also intend to develop a dynamic bandwidth allocation algorithm as a future work.

by Stanley B. Gershwin, David M. Orlicki. / Bibliography: p. 58-59. / "March 1982." / U. S. Department of Transportation Contract DOT-TSC-RSPA-81-9

The Aw-Rascle-Zhang (ARZ) model has become a favorable ``second order" macroscopic traffic model, which corrects several shortcomings of the Payne-Whitham (PW) model. The ARZ model possesses a family of flow rate versus density (FD) curves, rather than a single one as in the ``first order" Lighthill-Whitham-Richards (LWR) model. This is more realistic especially during congested traffic state, where the historic fundamental diagram data points are observed to be set-valued. However, the ARZ model also possesses some obvious shortcomings, e.g., it assumes multiple maximum traffic densities which should be a ``property" of road. Instead, we propose a Generalized ARZ (GARZ) model under the generic framework of ``second order" macroscopic models to overcome the drawbacks of the ARZ model. A systematic approach is presented to design generic ``second order" models from historic data, e.g., we construct a family of flow rate curves by fitting with data. Based on the GARZ model, we then propose a phase-transition-like model that allows the flow rate curves to coincide in the free flow regime. The resulting model is called Collapsed GARZ (CGARZ) model. The CGARZ model keeps the flavor of phase transition models in the sense that it assume a single FD function in the free-flow phase. However, one should note that there is no real phase transition in the CGARZ model. To investigate to which extent the new generic ``second order" models (GARZ, CGARZ) improve the prediction accuracy of macroscopic models, we perform a comparison of the proposed models with two types of LWR models and their ``second order" generalizations, given by the ARZ model, via a three-detector problem test. In this test framework, the initial and boundary conditions are derived from real traffic data. In terms of using historic traffic data, a statistical technique, the so-called kernel density estimation, is applied to obtain density and velocity distributions from trajectory data, and a cubic interpolation is employed to formulate boundary condition from single-loop sensor data. Moreover, a relaxation term is added to the momentum equation of selected ``second order" models to address further unrealistic aspects of homogeneous models. Using these inhomogeneous ``second order" models, we study which choices of the relaxation term &tau are realistic. / Mathematics

O trânsito das metrópoles do novo milênio é um dos problemas que mais leva ao desperdício de recursos, com a consequente redução da qualidade de vida nas metrópoles. Os gastos ligados a vários fatores fazem com que o uso do veículo na hora do pico de trânsito seja duas vezes maior que o normal. O trânsito também gera poluição e consequentemente contribui para doenças pulmonares. O problema de planejamento operacional das infraestruturas viárias em uma grande metrópole constitui algo muito complexo. Problemas deste tamanho ainda não podem ser enfrentados, pelos sistemas computacionais modernos, na sua totalidade. Este problema se resolve dividindo as metrópoles em áreas nas quais é possível conduzir estudos que resolvam as situações locais. A circulação entre zonas distantes das metrópoles é suportada pelas vias expressas, as quais podem ser otimizadas globalmente. Com o crescimento das metrópoles e de seu número de veículos, muitas vezes, as infraestruturas ficam inadequadas, fazendo com que parte dos fluxos das vias expressas invadam os bairros. Neste trabalho se propõe fortalecer a capacidade dos bairros de enfrentar as situações de fluxos intensos. O processo proposto é hierárquico tendo uma primeira fase composta de estudos locais efetuados com simulação micro/mesoscópica, e uma sucessiva otimização global baseada nos resultados das locais. O sistema de otimização necessita de um teste que avalia as soluções escolhidas ao longo do processo. Na literatura da engenharia de tráfego se encontram diferentes níveis de análise do trânsito que geram as três categorias de modelos de simulação. Estas categorias ganham os nomes de modelos microscópicos, mesoscópicos e macroscópicos, mas nenhuma se mostra apta a ser utilizada como teste do sistema proposto. Neste trabalho se propõe um simulador que abstrai o conceito de rede viária reduzindo os custos computacionais até conseguir simular uma inteira metrópole. A técnica de estudo proposta, nos testes, se revela útil em determinadas situações, mas ainda deve ser confrontada com as novas tecnologias capazes de refinar os planos operacionais em tempo real na base dos dados de sensores e câmeras espalhados nas infraestruturas. / The traffic of new-millennium metropolises is one of the problems that most cause resources waste, consequently reducing the quality of life in these metropolises. The costs related to a series of causes make the use of vehicles at rush times be twice as frequent as during other times. The traffic also generates pollution, hence contributing to pulmonary diseases. The infrastructures operational planning problems in big cities is a complex issue. Such big problems still cannot be fully faced by modern computer systems. This can be solved dividing the cities into areas where it is possible to run studies to solve local situations. The circulation between distant areas in metropolises can be done via express motorways, which can be globally improved. With the expansion of big cities and their vehicles, the infrastructures frequently become inadequate and the stream invades neighborhoods. The aim of the present work is to improve the capacity of neighborhoods streams, offering besides technical norms, a global optimization based on local results. The optimization system needs a test that evaluates the chosen solutions along the process. In traffic engineering literature, there are different levels of traffic analysis that generate the three simulation model categories. These categories are named microscopic, mesoscopic, and macroscopic models, but none of them is able to be used as test to the proposed system. In this work, it is proposed a simulator that abstracts the concept of road network, reducing the computer expenses up to the simulation of a whole city. The study technic pruioposed in the tests shows itself as useful in certain situations, but still must be confronted with new technologies able to refine the operational plans in real time based on the sensors and cameras data.

O trânsito das metrópoles do novo milênio é um dos problemas que mais leva ao desperdício de recursos, com a consequente redução da qualidade de vida nas metrópoles. Os gastos ligados a vários fatores fazem com que o uso do veículo na hora do pico de trânsito seja duas vezes maior que o normal. O trânsito também gera poluição e consequentemente contribui para doenças pulmonares. O problema de planejamento operacional das infraestruturas viárias em uma grande metrópole constitui algo muito complexo. Problemas deste tamanho ainda não podem ser enfrentados, pelos sistemas computacionais modernos, na sua totalidade. Este problema se resolve dividindo as metrópoles em áreas nas quais é possível conduzir estudos que resolvam as situações locais. A circulação entre zonas distantes das metrópoles é suportada pelas vias expressas, as quais podem ser otimizadas globalmente. Com o crescimento das metrópoles e de seu número de veículos, muitas vezes, as infraestruturas ficam inadequadas, fazendo com que parte dos fluxos das vias expressas invadam os bairros. Neste trabalho se propõe fortalecer a capacidade dos bairros de enfrentar as situações de fluxos intensos. O processo proposto é hierárquico tendo uma primeira fase composta de estudos locais efetuados com simulação micro/mesoscópica, e uma sucessiva otimização global baseada nos resultados das locais. O sistema de otimização necessita de um teste que avalia as soluções escolhidas ao longo do processo. Na literatura da engenharia de tráfego se encontram diferentes níveis de análise do trânsito que geram as três categorias de modelos de simulação. Estas categorias ganham os nomes de modelos microscópicos, mesoscópicos e macroscópicos, mas nenhuma se mostra apta a ser utilizada como teste do sistema proposto. Neste trabalho se propõe um simulador que abstrai o conceito de rede viária reduzindo os custos computacionais até conseguir simular uma inteira metrópole. A técnica de estudo proposta, nos testes, se revela útil em determinadas situações, mas ainda deve ser confrontada com as novas tecnologias capazes de refinar os planos operacionais em tempo real na base dos dados de sensores e câmeras espalhados nas infraestruturas. / The traffic of new-millennium metropolises is one of the problems that most cause resources waste, consequently reducing the quality of life in these metropolises. The costs related to a series of causes make the use of vehicles at rush times be twice as frequent as during other times. The traffic also generates pollution, hence contributing to pulmonary diseases. The infrastructures operational planning problems in big cities is a complex issue. Such big problems still cannot be fully faced by modern computer systems. This can be solved dividing the cities into areas where it is possible to run studies to solve local situations. The circulation between distant areas in metropolises can be done via express motorways, which can be globally improved. With the expansion of big cities and their vehicles, the infrastructures frequently become inadequate and the stream invades neighborhoods. The aim of the present work is to improve the capacity of neighborhoods streams, offering besides technical norms, a global optimization based on local results. The optimization system needs a test that evaluates the chosen solutions along the process. In traffic engineering literature, there are different levels of traffic analysis that generate the three simulation model categories. These categories are named microscopic, mesoscopic, and macroscopic models, but none of them is able to be used as test to the proposed system. In this work, it is proposed a simulator that abstracts the concept of road network, reducing the computer expenses up to the simulation of a whole city. The study technic pruioposed in the tests shows itself as useful in certain situations, but still must be confronted with new technologies able to refine the operational plans in real time based on the sensors and cameras data.

Este estudo tem por objetivo propor um método para aprimorar a estimativa de emissões veiculares em áreas urbanas através da utilização de modelagem híbrida de tráfego associada a modelos de previsão de emissões. A modelagem híbrida agrega as vantagens individuais das abordagens agregada e desagregada de tráfego, uma vez que combina a micro-simulação de tráfego em áreas específicas com a simulação agregada em uma área de estudo mais abrangente. O método proposto neste trabalho foi consolidado a partir do desenvolvimento de um estudo de caso que consistiu na modelagem de uma rede viária com características distintas de infraestrutura e operação viárias. Os resultados do estudo de caso permitiram a identificação de trechos da rede viária nos quais as estimativas de emissões provenientes de modelos agregados foram significativamente diferentes das estimativas derivadas de modelos microscópicos, demonstrando a importância de uma abordagem híbrida. A utilização do método proposto pode embasar a elaboração e implementação de políticas de transportes que busquem reduzir a ocorrência de eventos responsáveis pela geração de elevados níveis de emissões. / This study aims to propose a method to improve the vehicle emissions estimation in urban area. The method associates hybrid traffic flow models with emission models. Hybrid traffic modeling combines the specific advantages of aggregate and disaggregated approaches, since they integrate traffic microssimulation in specific areas with agregated simulation in a wide area. The development of the proposed method was based on a case study consisting in the modeling a road network with different operations and infrastructure characteristics. Case study results indicated that emission estimates obtained from aggregated models were significantly different from emission estimates derived from microscopic models on some road segments, emphasizing the importance of a hybrid approach adopted in the method proposed in this work. The proposed method can be used to guide the development and implementation of transportation policies that aim to reduce the number of traffic events responsible for high levels of emissions.

<p>Driving simulators are used to conduct experiments on for example driver behavior, road design, and vehicle characteristics. The results of the experiments often depend on the traffic conditions. One example is the evaluation of cellular phones and how they affect driving behavior. It is clear that the ability to use phones when driving depends on traffic intensity and composition, and that realistic experiments in driving simulators therefore has to include surrounding traffic.</p><p>This thesis describes a model that generates and simulates surrounding vehicles for a driving simulator. The proposed model generates a traffic stream, corresponding to a given target flow and simulates realistic interactions between vehicles. The model is built on established techniques for time-driven microscopic simulation of traffic and uses an approach of only simulating the closest neighborhood of the driving simulator vehicle. In our model this closest neighborhood is divided into one inner region and two outer regions. Vehicles in the inner region are simulated according to advanced behavioral models while vehicles in the outer regions are updated according to a less time-consuming model. The presented work includes a new framework for generating and simulating vehicles within a moving area. It also includes the development of enhanced models for car-following and overtaking and a simple mesoscopic traffic model.</p><p>The developed model has been integrated and tested within the VTI Driving simulator III. A driving simulator experiment has been performed in order to check if the participants observe the behavior of the simulated vehicles as realistic or not. The results were promising but they also indicated that enhancements could be made. The model has also been validated on the number of vehicles that catches up with the driving simulator vehicle and vice versa. The agreement is good for active and passive catch-ups on rural roads and for passive catch-ups on freeways, but less good for active catch-ups on freeways.</p>

During the last decade, the Internet usage has been growing at an enormous rate which has beenaccompanied by the developments of network applications (e.g., video conference, audio/videostreaming, E-learning, E-Commerce and real-time applications) and allows several types ofinformation including data, voice, picture and media streaming. While end-users are demandingvery high quality of service (QoS) from their service providers, network undergoes a complex trafficwhich leads the transmission bottlenecks. Considerable effort has been made to study thecharacteristics and the behavior of the Internet. Simulation modeling of computer networkcongestion is a profitable and effective technique which fulfills the requirements to evaluate theperformance and QoS of networks. To simulate a single congested link, simulation is run with asingle load generator while for a larger simulation with complex traffic, where the nodes are spreadacross different geographical locations generating distributed artificial loads is indispensable. Onesolution is to elaborate a load generation system based on master/slave architecture.

Este estudo tem por objetivo propor um método para aprimorar a estimativa de emissões veiculares em áreas urbanas através da utilização de modelagem híbrida de tráfego associada a modelos de previsão de emissões. A modelagem híbrida agrega as vantagens individuais das abordagens agregada e desagregada de tráfego, uma vez que combina a micro-simulação de tráfego em áreas específicas com a simulação agregada em uma área de estudo mais abrangente. O método proposto neste trabalho foi consolidado a partir do desenvolvimento de um estudo de caso que consistiu na modelagem de uma rede viária com características distintas de infraestrutura e operação viárias. Os resultados do estudo de caso permitiram a identificação de trechos da rede viária nos quais as estimativas de emissões provenientes de modelos agregados foram significativamente diferentes das estimativas derivadas de modelos microscópicos, demonstrando a importância de uma abordagem híbrida. A utilização do método proposto pode embasar a elaboração e implementação de políticas de transportes que busquem reduzir a ocorrência de eventos responsáveis pela geração de elevados níveis de emissões. / This study aims to propose a method to improve the vehicle emissions estimation in urban area. The method associates hybrid traffic flow models with emission models. Hybrid traffic modeling combines the specific advantages of aggregate and disaggregated approaches, since they integrate traffic microssimulation in specific areas with agregated simulation in a wide area. The development of the proposed method was based on a case study consisting in the modeling a road network with different operations and infrastructure characteristics. Case study results indicated that emission estimates obtained from aggregated models were significantly different from emission estimates derived from microscopic models on some road segments, emphasizing the importance of a hybrid approach adopted in the method proposed in this work. The proposed method can be used to guide the development and implementation of transportation policies that aim to reduce the number of traffic events responsible for high levels of emissions.