Η παρούσα διδακτορική διατριβή πραγματεύεται την ανάλυση και προσομοίωση τηλεπικοινωνιακών δικτύων πολυδιάστατης κίνησης, ενώ δίνεται ιδιαίτερη έμφαση στα οπτικά δίκτυα. Βασικός σκοπός της διατριβής αποτελεί η ανάπτυξη αναλυτικών μοντέλων για τον υπολογισμό παραμέτρων απόδοσης του δικτύου, όπως η πιθανότητα απώλειας σύνδεσης, πιθανότητα απώλειας κλήσης, η καθυστέρηση μετάδοσης και το ποσοστό χρησιμοποίησης του καναλιού μετάδοσης. Τα προτεινόμενα αναλυτικά μοντέλα διαφοροποιούνται ανάλογα με την τεχνολογία δικτύου. Οι τεχνολογίες αυτές είναι: Α) Οπτικά δίκτυα δρομολόγησης μήκους κύματος. Β) Οπτικά δίκτυα πρόσβασης. Γ) Ασύρματα δίκτυα πρόσβασης στο Διαδίκτυο. Για οπτικά δίκτυα δρομολόγησης μήκους κύματος αρχικά μελετάται η περίπτωση απλής οπτικής ζεύξης, ενώ στη συνέχεια εξετάζεται δίκτυο πολλαπλών κόμβων τυχαίας τοπολογίας. Επίσης, προτείνονται αναλυτικά μοντέλα για την περίπτωση της μεταγωγής οπτικών πακέτων με την αποτίμηση της απόδοσης ενός οπτικού διακόπτη, αλλά και δικτύου μεταγωγής οπτικών πακέτων τυχαίας τοπολογίας. Ακολούθως, προτείνονται αναλυτικά μοντέλα για την αποτίμηση της απόδοσης παθητικών οπτικών δικτύων, τα οποία υλοποιούν διαφορετικές μεθόδους πολλαπλής πρόσβασης. Για την περίπτωση της πολλαπλής πρόσβασης με διαίρεση χρόνου μελετάται το παθητικό οπτικό δίκτυο Ethernet, το οποίο υποστηρίζει πολυδιάστατη κίνηση. Αναφορικά με την πολυπλεξία με διαίρεση μήκους κύματος μελετάται ένα υβριδικό παθητικό οπτικό δίκτυο σε επίπεδο κλήσεων. Οι κλήσεις διακρίνονται ανάλογα με τη διαδικασία άφιξης σε τυχαίες και ψευδοτυχαίες κλήσεις, ανάλογα με τις απαιτήσεις σε εύρος ζώνης σε κλήσεις με σταθερές και ελαστικές απαιτήσεις και ανάλογα με τη συμπεριφορά τους κατά την παραμονή τους στο δίκτυο σε κλήσεις σταθερού ρυθμού μετάδοσης και σε κλήσεις οι οποίες εναλλάσσονται μεταξύ ενεργών περιόδων μετάδοσης και περιόδων σιγής. Τέλος, προτείνονται αναλυτικά μοντέλα υπολογισμού απωλειών για την περίπτωση της πολλαπλής πρόσβασης με διαίρεση οπτικού κώδικα, τα οποία λαμβάνουν υπ’όψιν πολλαπλές υπηρεσίες, την παρουσία προσθετικού θορύβου, αλλά και τη δραστηριότητα του χρήστη. Για την αποτίμηση της απόδοσης ασύρματων δικτύων πρόσβασης στο Διαδίκτυο προτείνονται αναλυτικά μοντέλα, τα οποία υλοποιούν το πρωτόκολλο ΙΕΕΕ 802.11 ή το πρωτόκολλο ΙΕΕΕ 802.11e. Η προτεινόμενη ανάλυση υπολογίζει τόσο τη διεκπεραιωτική ικανότητα του δικτύου, όσο και τη συνολική καθυστέρηση μετάδοσης πακέτου ως συνάρτηση της καθυστέρησης στο ασύρματο μέσο και της καθυστέρησης στην ουρά αναμονής. Σε όλες τις περιπτώσεις η ακρίβεια των προτεινόμενων μοντέλων πιστοποιείται/ελέγχεται με την προσομοίωση του δικτύου στον υπολογιστή. / In this PhD dissertation multi-rate models are examined for the performance analysis of telecommunication networks through mathematical analysis and simulation. Particular emphasis is given to optical networks. The main goal is the development of analytical models for the calculation of network performance metrics, such as blocking probabilities, transmission delay and utilization of the common channel. The proposed analytical models are distinguished according to the network technologies. Three different technologies are considered: A) Wavelength routed optical networks. B) Optical access networks. C) Wireless Internet access networks. Multi-rate loss models are proposed for the performance evaluation of wavelength routed optical networks. Firstly, the case of a single link is considered and then a mesh all-optical network is examined. In addition, analytical models are proposed for Optical Packet Switching (OPS) networks, for the case of an all-optical OPS switch and of an OPS mesh network. Multi-rate analytical models are proposed for the evaluation of the performance of Passive Optical Networks (PONs) implementing different multiple access methods. For the case of Time Division Multiple Access (TDMA) the Ethernet PON is studied, which supports multiple service-classes. Regarding the Wavelength Division Multiplexing (WDM) PONs a hybrid WDM-TDMA PON is considered and the call-level performance is evaluated. Calls are distinguished by their arrival process, which can be random or quasi random, by their bandwidth requirements, which can be fixed of elastic and by their behavior during their service, which can be calls of fixed transmission rate or calls that alternate between ON and OFF periods. Finally multi-rate loss models are proposed for the case of Optical Code Division Multiple Access (OCDMA) PONs that take into account the user activity and the presence of additive noise in the transmission channel. For the performance analysis of wireless Internet access networks analytical models are proposed, which implement the IEEE 802.11 protocol or the IEEE 802.11e protocol. The proposed analysis calculated the saturation throughput and the end-to-end packet delay as a function of the Medium Access Control (MAC) delay and the queueing delay. In all cases the accuracy of the proposed models is validated through simulation.

<div>With more and more videos taken from dash cams on thousands of cars, retrieving these videos and searching for important information is a daunting task. The purpose of this work is to mine some key road and vehicle motion attributes in a large-scale driving video data set for traffic analysis, sensing algorithm development and autonomous driving test benchmarks. Current sensing and control of autonomous cars based on full-view identification makes it difficult to maintain a high-frequency with a fast-moving vehicle, since computation is increasingly used to cope with driving environment changes.</div><div><br></div><div>A big challenge in video data mining is how to deal with huge amounts of data. We use a compact representation called the road profile system to visualize the road environment in long 2D images. It reduces the data from each frame of image to one line, thereby compressing the video clip to the image. This data dimensionality reduction method has several advantages: First, the data size is greatly compressed. The data is compressed from a video to an image, and each frame in the video is compressed into a line. The data size is compressed hundreds of times. While the size and dimensionality of the data has been compressed greatly, the useful information in the driving video is still completely preserved, and motion information is even better represented more intuitively. Because of the data and dimensionality reduction, the identification algorithm computational efficiency is higher than the full-view identification method, and it makes the real-time identification on road is possible. Second, the data is easier to be visualized, because the data is reduced in dimensionality, and the three-dimensional video data is compressed into two-dimensional data, the reduction is more conducive to the visualization and mutual comparison of the data. Third, continuously changing attributes are easier to show and be captured. Due to the more convenient visualization of two-dimensional data, the position, color and size of the same object within a few frames will be easier to compare and capture. At the same time, in many cases, the trouble caused by tracking and matching can be eliminated. Based on the road profile system, there are three tasks in autonomous driving are achieved using the road profile images.</div><div><br></div><div>The first application is road edge detection under different weather and appearance for road following in autonomous driving to capture the road profile image and linearity profile image in the road profile system. This work uses naturalistic driving video data mining to study the appearance of roads, which covers large-scale road data and changes. This work excavated a large number of naturalistic driving video sets to sample the light-sensitive area for color feature distribution. The effective road contour image is extracted from the long-time driving video, thereby greatly reducing the amount of video data. Then, the weather and lighting type can be identified. For each weather and lighting condition obvious features are I identified at the edge of the road to distinguish the road edge. </div><div><br></div><div>The second application is detecting vehicle interactions in driving videos via motion profile images to capture the motion profile image in the road profile system. This work uses visual actions recorded in driving videos taken by a dashboard camera to identify this interaction. The motion profile images of the video are filtered at key locations, thereby reducing the complexity of object detection, depth sensing, target tracking and motion estimation. The purpose of this reduction is for decision making of vehicle actions such as lane changing, vehicle following, and cut-in handling.</div><div><br></div><div>The third application is motion planning based on vehicle interactions and driving video. Taking note of the fact that a car travels in a straight line, we simply identify a few sample lines in the view to constantly scan the road, vehicles, and environment, generating a portion of the entire video data. Without using redundant data processing, we performed semantic segmentation to streaming road profile images. We plan the vehicle's path/motion using the smallest data set possible that contains all necessary information for driving.</div><div><br></div><div>The results are obtained efficiently, and the accuracy is acceptable. The results can be used for driving video mining, traffic analysis, driver behavior understanding, etc.</div>

This thesis aims to improve a satellite communication network which carries both data streams and Voice over IP (VoIP) communication sessions with resource reservation. The resource reservations are made using the standard protocols for Traffic Engineering: MPLS-TE and RSVP-TE. The goal of this thesis project is to optimize the number of concurrent VoIP calls that can be made, in order to use the available bandwidth while maintaining a guaranteed Quality of Service (QoS) level, which is not possible in the existing system. This thesis proposes and evaluates a solution to this optimization problem in the specific context of a satellite modem system that was developed by Thales Communications. This optimization improves the system's ability to carry VoIP communications through better use of the available transmission resources. A solution to this problem would also increase the  exibility in bandwidth allocation within the modem system, and could provide a framework for future development. The proposed solution allows all of the reservable bandwidth to be used.  The amount of reservable bandwidth must be at least a little lower than the channel's available bandwidth in order to avoid congestion. Some areas of future work are proposed. / Detta projekt har försökt förbättra ett datornätverk bestående av satelliter som används till både data och Voice over IP (VoIP) kommunikation. VoIP använder sig av resursreservation som bestäms av standardprotokollen för Traffic Engineering, MPLS-TE och RSVP-TE.  Målet är att optimera antalet samtidiga VoIP samtal så att det mesta av den befintliga bandbredden kan utnyttjas samtidigt som Quality of Service (QoS) kan garanteras. Detta är omöjligt i det befintliga systemet. Projektet föreslår en lösning för problemet med modemet som utvecklas av Thales Communications och utvärderar därefter lösningen. Dessa optimeringar förbättrar systemets förmåga att driva VoIP kommunikationer genom att bättre använda de befintliga resurserna. En lösning för det här problemet skulle höja systemets flexibilitet och kunna användas som underlag för kommande utvecklingar. Tack vare lösningen kan hela utsedda bandbredden reserveras. Antalet bandbredd som kan reserveras måsta vara minst lite lågre än total befintling bandbredd för att undvika överbelastning. även några möjliga ideer för vidare undersökning föreslås. / Ce projet a pour but d'améliorer un réseau de communication par satellite utilisé pour transporter des flux de données ainsi que des sessions de communication Voix sur IP (VoIP) avec réservation de ressources. Les réservations sont prises en charge par les protocoles standard de Traffic Engineering que sont MPLS-TE et RSVP-TE. L'objectif de ce projet est d'optimiser le nombre d'appels VoIP pouvant être passés en parallèle afin d'utiliser autant de bande passante que possible tout en offrant un niveau de Qualité de Service (QoS) garanti, chose impossible dans le système actuel. Ce rapport propose et évalue une solution à ce problème d'optimisation dans le contexte spécifique du modem satellite développé par Thales Communications. Ces optimisations amélioreraient la capacité du système à transporter des communications VoIP grâce à une meilleure utilisation des ressources disponibles pour la transmission. Une solution à ce problème rendrait aussi l'allocation de ressources plus flexible au sein du système, et pourrait fournir une base à de futurs développements. La solution proposée permet l'utilisation de toute la bande passante réservable. La quantité réservable doit être un peu inférieure à la bande passante totale disponible afin d'éviter la congestion. Les résultats de ces évaluations sont exposés. Enfin, ce rapport propose de futurs développements possibles.

Safety and congestion are ever present and increasingly severe transportation problems in urban areas throughout the nation and world. These phenomena can have wide-ranging consequences relating to safety, the economy, and the environment. Adverse weather conditions represent another significant challenge to safety and mobility on highways. Oregon is not immune from either of these global issues. Oregon Route (OR) 217, to the southwest of the downtown Portland, is one of the worst freeways for congestion in the state and is also subject to the Pacific Northwest's frequently inclement and unpredictable climate. High crash rates, severe recurrent bottlenecks and highly unreliable travel times continuously plague the corridor, making it a major headache for the thousands of commuters using it every day. In an effort to more effectively combat both congestion and adverse weather, transportation officials all over the world have been turning to increasingly technological strategies like Active Traffic Management (ATM). This can come in many forms, but among the most common are variable speed limit (VSL) systems which use real-time data to compute and display appropriate reduced speeds during congestion and/or adverse weather. After numerous studies and deliberations, Oregon Department of Transportation (ODOT) selected Oregon Route (OR) 217 as one of the first locations in the state to be implemented with an advisory VSL system, and that system began operation in the summer of 2014. This thesis seeks to evaluate the effectiveness of this VSL system through the first eight months of its operation through an in-depth and wide-ranging "before and after" analysis. Analysis of traffic flow and safety data for OR 217 from before the VSL system was implemented made clear some of the most prevalent issues which convinced ODOT to pursue VSL. Using those issues as a basis, a framework of seven specific evaluation questions relating to both performance and safety, as well as both congestion and adverse weather, was established to guide the "before and after" comparisons. Hypotheses, and measures of effectiveness for each question were developed, and data were obtained from a diverse array of sources including freeway detectors, ODOT's incident database, and the National Oceanic and Atmospheric Administration (NOAA). The results of the various "before and after" comparisons performed as a part of this thesis indicate that conditions have changed on OR 217 in a number of ways since the VSL system was activated. Many, but not all, of the findings were consistent with the initial hypotheses and with the findings from other VSL studies in the literature. Certain locations along the corridor have seen significant declines in speed variability, supporting the common notion that VSL systems have a harmonizing effect on traffic flow. Crash rates have not decreased, but crashes have become less frequent in the immediate vicinity of VSL signs. Flow distribution between adjacent lanes has been more even since VSL implementation during midday hours and the evening peak, and travel time reliability has seen widespread improvement in three of the corridor's four primary travel lanes during those same times. The drops in flow that generally occur upstream of bottlenecks once they form have had diminished magnitudes, while the drops in flow downstream of the same bottlenecks have grown. Finally, the increase in travel times that is usually brought about by adverse weather has been smaller since VSL implementation, while the decline in travel time reliability has largely disappeared.