The concept of using qualitative measures to describe the quality of service at signalized intersections provided by different designs and controls has been discussed in numerous conferences. Such measures may include driver's comfort, convenience, anxiety, and preferences. The primary objective of this study was to demonstrate the feasibility of using the University of Central Florida's interactive driving simulator to execute several scenarios involving different unusual design and operation practices to measure the quality of service at a signalized intersection. This thesis describes the scenarios, the experiments conducted, the data collected, and analysis of results. Signalized intersections with 3 types of characteristic features were identified for this study. They included 1. A lane dropping on the downstream side of the intersection 2. Misalignment of traffic lanes between the approach and downstream side 3. Shared left turn and through traffic lane or separate lanes for each approaching the intersection The experimental phase consisted of a brief orientation session to get acclimated to the driving simulator followed by two driving scenarios presented to all subjects. Each scenario consisted of a drive through an urban section of the simulator's visual data base where each subject encountered a Type 1, 2 and 3 intersections. A total of 40 subjects, 25 males and 15 females were recruited for the experiment. Data logging at 60 Hz for each scenario consisted of time-stamped values of x-position and y-position of the simulator vehicle, steering, accelerator and brake inputs by the driver, and vehicle speed. After the experiment a questionnaire soliciting opinions and reactions about each intersection was administered. Simulator experiment results showed that there was a significant difference between the merge lengths for the two cases of Type 1 intersection (lane drop on the downstream side of the intersection). For Type 2 intersection (misalignment of traffic lanes between the approach and downstream side) there was a considerable difference between the average paths followed by subjects for the two cases. For Type 3 intersection (shared left and through traffic lane approaching the intersection) the simulator experiment supported the fact that people get frustrated when trapped behind a left turning vehicle in a joint left and through lane intersection and take evasive actions to cross the intersection as soon as possible.

As the Internet evolves, there is a continued demand for high Internet bandwidth. This demand is driven partly by the widely spreading real-time video applications, such as on-line gaming, teleconference, high-definition video streaming. All-optical switches and routers have long been studied as a promising solution to the rapidly growing demand. Nevertheless, buffer sizes in all-optical switches and routers are very limited due to the challenges in manufacturing larger optical buffers. On the other hand, Internet traffic is bursty. The existence of burstiness in network traffic has been shown at all time scales, from tens of milliseconds to thousands of seconds. The widely existing burstiness has a very significant impact on the performance of small buffer networks, resulting in high packet drop probabilities and low link utilization. There have been many solutions proposed in the literature to solve the burstiness issue of network traffic. Traffic engineering techniques, such as traffic shaping and polishing, have been available in commercial routers/switches since the era of Asynchronous Transfer Mode (ATM) networks. Moreover, TCP pacing, as a natural solution to the TCP burstiness, has long been studied. Furthermore, several traffic conditioning and scheduling techniques are proposed to smooth core network traffics in a coordinated manner. However, all the existing solutions are inadequate to efficiently solve the burstiness issue of high-speed traffic. In this dissertation we aim to tackle the burstiness issue in small buffer networks, which refer to the future Internet core network consisting of all-optical routers and switches with small buffers. This dissertation is composed of two parts. In the first part, we analyze the impact of a general pacing scheme on the performance of a tandem queue network. This part serves as a theoretical foundation, based on which we demonstrate the benefits of pacing in a tandem queue model. Specifically, we use the Infinitesimal Perturbation Analysis (IPA) technique to study the impact of pacing on the instantaneous and average queue lengths of a series of nodes. Through theoretical analyses and extensive simulations, we show that under certain conditions there exists a linear relationship between system parameters and instantaneous/average queue lengths of nodes and that pacing improves the performance of the underlying tandem queue system by reducing the burstiness of the packet arrival process. In the second part, we propose a practical on-line packet pacing scheme, named Queue Length Based Pacing (QLBP). We analyze the impact of QLBP on the underlying network traffic in both time and frequency domains. We also present two implementation algorithms that allow us to evaluate the performance of QLBP in real experimental and virtual simulation environments. Through extensive simulations, we show that QLBP can effectively reduce the burstiness of network traffic and hence significantly improve the performance of a small buffer network. More important, the network traffic paced with QLBP does not exhibit a weakened competition capability when competing with non-paced traffic, which makes the QLBP scheme more attractive for ISPs.

<p>Packet transmission scheduling plays a key role in Quality of Service (QoS) support for real-time traffic and efficient radio resource utilization in a wireless mesh network (WMN). It is a highly complicated problem due to the fact that any scheduling decision at one mesh access point (AP) may affect the scheduling decisions in the entire network. The strict delay requirement of real-time applications makes the scheduling problem even more challenging.</p> <p> In this thesis, the packet transmission scheduling problem for real-time constant-bit-rate (CBR) traffic in a WMN is first formulated as a standard integer linear programming problem, which takes into consideration both the multihop packet transmission delay and timeline coordinations of the mesh APs. The objective is to efficiently utilize the radio resources, subject to available bandwidth of the mesh APs, co-channel interference, and packet transmission latency requirement.</p> <p>Two heuristic schemes, namely AP-based scheduling (ABS) and connection-based scheduling (CBS) schemes, are then proposed to support real-time CBR traffic. ABS makes scheduling decisions on a per-AP basis. Scheduling decisions at APs with a higher traffic load are determined before those at APs with a lower traffic load. ABS achieves close-to-optimum capacity but may go through multiple iterations before reaching a feasible solution. CBS makes scheduling decisions on a connection-by-connection basis. It gives a higher priority to connections with more hops. In CBS, connections with a lower priority can only use resources remaining from serving all higher priority connections. CBS requires much lower complexity than ABS while achieving capacity performance slightly lower than ABS.</p> <p>We extend the proposed ABS and CBS scheduling schemes for supporting real-time variable bit rate (VBR) traffic in a WMN. By combining the concept of effective bandwidth and the proposed scheduling schemes, both delay and packet loss performance of the VBR traffic can be effectively satisfied. The scheduling schemes are further extended for supporting real-time traffic in a WMN with multi-radio APs.</p> <p>All the scheduling decisions are done at the time when new connection requests arrive and the results are used to make admission control decisions. In this sense, the work in this thesis is for both packet transmission scheduling and admission control for real-time traffic in WMNs.</p> / Thesis / Doctor of Philosophy (PhD)

No / Quality of Service (QoS) is of extreme importance in accommodating the increasingly diverse range of services and types of traffic in present day communication networks and delay is one of the most important QoS metrics. This paper presents a new approach for constraining queueing delay in a buffer to a specified level as the arrival rate changes with time. A discrete-time control algorithm is presented that operates on a buffer (queue) which incorporates a moveable threshold. An algorithm is developed that controls the delay by dynamically adjusting the threshold which, in turn, controls the arrival rate. The feasibility of the system is examined using both theoretical analysis and simulation.

In the recent decade, peer-to-peer (P2P) technology has greatly enhanced the scalability of multimedia streaming on the Internet by enabling efficient cooperation among end-users. However, existing streaming applications are plagued by the problems of long playback latency and long churn-induced delays. First of all, many streaming applications, such as IPTV and video conferencing, have rigorous constraints on end-to-end delays. Moreover, churn-induced delays, including delays from channel switching and streaming recovery, in current P2P streaming applications are typically in the scale of 10-60 seconds, which is far below the favorable user experience as in cable TV systems. These two issues in terms of playback latency and churn-induced delays have hindered the extensive commercial deployment of P2P systems. Motivated by this, in this dissertation, we focus on reducing delays in P2P live streaming systems. Specifically, we propose solutions for reducing delays in P2P live streaming systems in four problem spaces: (1) minimizing the maximum end-to-end delay in P2P streaming; (2) minimizing the average end-to-end delay in P2P streaming; (3) minimizing the average delay in multi-channel P2P streaming; and (4) reducing churn-induced delays. We devise a streaming scheme to minimize the maximum end-to-end streaming delay under a mesh-based overlay network paradigm. We call this problem, the MDPS problem. We formulate the MDPS problem and prove its NP-completeness. We then present a polynomial-time approximation algorithm, called Fastream-I, for this problem, and show that the performance of Fastream-I is bounded by a ratio of O(SQRT(log n)), where n is the number of peers in the system. We also develop a distributed version of Fastream-I that can adapt to network dynamics. Our simulation study reveals the effectiveness of Fastream-I, and shows a reasonable message overhead. While Fastream-I yields the minimum maximum end-to-end streaming delay (within a factor of O(SQRT(log n)), in many P2P settings, users may desire the minimum average end-to-end P2P streaming delay. Towards this, we devise a streaming scheme which optimizes the bandwidth allocation to achieve the minimum average end-to-end P2P streaming delay. We call this problem, the MADPS problem. We first develop a generic analytical framework for the MADPS problem. We then present Fastream-II as a solution to the MADPS problem. The core part of Fastream-II is a fast approximation algorithm, called APX-Fastream-II, based on primal-dual schema. We prove that the performance of APX-Fastream-II is bounded by a ratio of 1+w, where w is an adjustable input parameter. Furthermore, we show that the flexibility of w provides a trade-off between the approximation factor and the running time of Fastream-II. The third problem space of the dissertation is minimizing the average delay in multi-channel P2P streaming systems. Toward this, we present an algorithm, called Fastream-III. To reduce the influence from frequent channel-switching behavior, we build Fastream-III for the view-upload decoupling (VUD) model, where the uploaded content from a serving node is independent of the channel it views. We devise an approximation algorithm based on primal-dual schema for the critical component of Fastream-III, called APX-Fastream-III. In contrast to APX-Fastream-II, APX-Fastream-III addresses the extra complexity in the multichannel scenario and maintains the approximation bound by a ratio of 1+w. Besides playback lag, delays occurring in P2P streaming may arise from two other factors: node churn and channel switching. Since both stem from the re-connecting request in churn, we call them churn-induced delays. Optimizing churn-induced delays is the dissertation's fourth problem space. Toward this, we propose NAP, a novel agent-based P2P scheme, that provides preventive connections to all channels. Each channel in NAP selects powerful peers as agents to represent the peers in the channel to minimize control and message overheads. Agents distill the bootstrapping peers with superior bandwidth and lifetime expectation to quickly serve the viewer in the initial period of streaming. We build a queueing theory model to analyze NAP. Based on this model, we numerically compare NAP's performance with past efforts. The results of the numerical analysis reveal the effectiveness of NAP. / Ph. D.

Long Term Evolution (LTE) was designed to provide fast data rates to replace 3G service for mobile devices. As LTE networks and the user base for those networks grow, it becomes necessary for the resources used for those networks to be used as efficiently as possible. This thesis presents an implementation which utilizes an algorithm extended upon the Frank Kelly algorithm to determine resource allocation for UEs and shapes traffic for each UE to meet those allocation limits. The implementation's network represents what an LTE network would do to manage data rates for a UE through a distributed algorithm for rate allocation. The main focus of the implementation is on the UE, where traffic shaping limits application rates by an elastic or inelastic classification through the use of Hierarchical Token Bucket (HTB) queuing disciplines. / Master of Science

Network management is a problem that faces designers and operators of any type of network. Conventional methods of capacity planning or configuration management are difficult to apply directly to networks that dynamically allocate resources, such as Asynchronous Transfer Mode (ATM) networks and emerging Internet Protocol (IP) networks employing Differentiated Services (DiffServ). This work shows a method to generically classify traffic in an ATM network such that capacity planning may be possible. These methods are generally applicable to other networks that support dynamically allocated resources. In this research, Call Detail Records (CDRs) captured from a ¡§live¡¨ ATM network were successfully classified into three traffic categories. The traffic categories correspond to three different video speeds (1152 kbps, 768 kbps, and 384 kbps) in the network. Further statistical analysis was used to characterize these traffic categories and found them to fit deterministic distributions. The statistical analysis methods were also applied to several different network planning and management functions. Three specific potential applications related to network management were examined: capacity planning, traffic modeling, and configuration management. / Master of Science

Because of their ubiquity and low cost fabrication techniques, electronic textiles (e-textiles) are an excellent platform for pervasive computing. Many e-textile applications are already available in the commercial, military, and academic domains, but most are very highly specialized and do not lend themselves easily to reuse or alteration. The purpose of this work is threefold: development of a methodology for building flexible and reusable applications that facilitates their use in the evolution of more complex systems, creation of a resource manager that realizes the methodology and enforces quality of service guarantees on tightly constrained textile resources, and construction of a simulation environment that allows for the rapid development and reconfiguration of systems to circumvent the need for the expensive physical prototyping process. This work discuss the effectiveness and appropriateness of the deployed event-driven hierarchical service model for application development. Additionally, this work explores the results of providing fault tolerance and quality of service guarantees in a textile environment that is particularly susceptible to faults. Further addressed by this work is the success of rapid prototyping and evaluation of applications in the simulation environment. / Master of Science

The growing demand on the variety of internet applications requires management of large scale networks by efficient Quality of Service (QoS) routing, which considerably contributes to the QoS architecture. The biggest contemporary drawback in the maintenance and distribution of the global state is the increase in communication overheads. Unbalancing in the network, due to the frequent use of the links assigned to the shortest path retaining most of the network loads is regarded as a major problem for best effort service. Localised QoS routing, where the source nodes use statistics collected locally, is already described in contemporary sources as more advantageous. Scalability, however, is still one of the main concerns of existing localised QoS routing algorithms. The main aim of this thesis is to present and validate new localised algorithms in order to develop the scalability of QoS routing. Existing localised routing, Credit Based Routing (CBR) and Proportional Sticky Routing (PSR), use the blocking probability as a factor in selecting the routing paths and work with either credit or flow proportion respectively, which makes impossible having up-to-date information. Therefore our proposed Highest Minimum Bandwidth (HMB) and Highest Average Bottleneck Bandwidth History (HABBH) algorithms utilise bandwidth as the direct QoS criterion to select routing paths. We introduce an Integrated Delay Based Routing and Admission Control mechanism. Using this technique Minimum Total Delay (MTD), Low Fraction Failure (LFF) and Low Path Failure (LPF) were compared against the global QoS routing scheme, Dijkstra, and localised High Path Credit (HPC) scheme and showed superior performance. The simulation with the non-uniformly distributed traffic reduced blocking probability of the proposed algorithms. Therefore, we advocate the algorithms presented in the thesis, as a scalable approach to control large networks. We strongly suggest that bandwidth and mean delay are feasible QoS constraints to select optimal paths by locally collected information. We have demonstrated that a few good candidate paths can be selected to balance the load in the network and minimise communication overhead by applying the disjoint paths method, recalculation of candidate paths set and dynamic paths selection method. Thus, localised QoS routing can be used as a load balancing tool in order to improve the network resource utilization. A delay and bandwidth combination is one of the future prospects of our work, and the positive results presented in the thesis suggest that further development of a distributed approach in candidate paths selection may enhance the proposed localised algorithms.

Récemment, l'utilisation des réseaux cellulaires a radicalement changé avec l’émergence de la quatrième génération (4G) de systèmes de télécommunications mobiles LTE/LTE-A (Long Term Evolution-Advanced). Les réseaux de générations précédentes (3G), initialement conçus pour le transport de la voix et les données à faible et moyen débits, ont du mal à faire face à l’augmentation accrue du trafic de données multimédia tout en répondant à leurs fortes exigences et contraintes en termes de qualité de service (QdS). Pour mieux répondre à ces besoins, les réseaux 4G ont introduit le paradigme des Réseaux Hétérogènes (HetNet).Les réseaux HetNet introduisent une nouvelle notion d’hétérogénéité pour les réseaux cellulaires en introduisant le concept des smalls cells (petites cellules) qui met en place des antennes à faible puissance d’émission. Ainsi, le réseau est composé de plusieurs couches (tiers) qui se chevauchent incluant la couverture traditionnelle macro-cellulaire, les pico-cellules, les femto-cellules, et les relais. Outre les améliorations des couvertures radio en environnements intérieurs, les smalls cells permettent d’augmenter la capacité du système par une meilleure utilisation du spectre et en rapprochant l’utilisateur de son point d’accès au réseau. Une des conséquences directes de cette densification cellulaire est l’interférence générée entre les différentes cellules des diverses couches quand ces dernières réutilisent les mêmes fréquences. Aussi, la définition de solutions efficaces de gestion des interférences dans ce type de systèmes constitue un de leurs défis majeurs. Cette thèse s’intéresse au problème de gestion des interférences dans les systèmes hétérogènes LTE-A. Notre objectif est d’apporter des solutions efficaces et originales au problème d’interférence dans ce contexte via des mécanismes d’ajustement de puissance des petites cellules. Nous avons pour cela distingués deux cas d’étude à savoir un déploiement à deux couches macro-femtocellules et macro-picocellules. Dans la première partie dédiée à un déploiement femtocellule et macrocellule, nous concevons une stratégie d'ajustement de puissance des femtocellules assisté par la macrocellule et qui prend en compte les performances des utilisateurs des femtocells tout en atténuant l'interférence causée aux utilisateurs des macrocellules sur leurs liens montants. Cette solution offre l’avantage de la prise en compte de paramètres contextuels locaux aux femtocellules (tels que le nombre d’utilisateurs en situation de outage) tout en considérant des scénarios de mobilité réalistes. Nous avons montré par simulation que les interférences sur les utilisateurs des macrocellules sont sensiblement réduites et que les femtocellules sont en mesure de dynamiquement ajuster leur puissance d'émission pour atteindre les objectifs fixés en termes d’équilibre entre performance des utilisateurs des macrocellules et celle de leurs propres utilisateurs. Dans la seconde partie de la thèse, nous considérons le déploiement de picocellules sous l'égide de la macrocellule. Nous nous sommes intéressés ici aux solutions d’extension de l’aire picocellulaire qui permettent une meilleure association utilisateur/cellule permettant de réduire l’interférence mais aussi offrir une meilleure efficacité spectrale. Nous proposons donc une approche basée sur un modèle de prédiction de la mobilité des utilisateurs qui permet de mieux ajuster la proportion de bande passante à partager entre la macrocellule et la picocellule en fonction de la durée de séjour estimée de ces utilisateurs ainsi que de leur demandes en bande passante. Notre solution a permis d’offrir un bon compromis entre les débits réalisables de la Macro et des picocellules. / Recently the use of modern cellular networks has drastically changed with the emerging Long Term Evolution Advanced (LTE-A) technology. Homogeneous networks which were initially designed for voice-centric and low data rates face unprecedented challenges for meeting the increasing traffic demands of high data-driven applications and their important quality of service requirements. Therefore, these networks are moving towards the so called Heterogeneous Networks (HetNets). HetNets represent a new paradigm for cellular networks as their nodes have different characteristics such as transmission power and radio frequency coverage area. Consequently, a HetNet shows completely different interference characteristics compared to homogeneous deployment and attention must be paid to these disparities when different tiers are collocated together. This is mostly due to the potential spectrum frequency reuse by the involved tiers in the HetNets. Hence, efficient inter-cell interference mitigation solutions in co-channel deployments of HetNets remain a challenge for both industry and academic researchers. This thesis focuses on LTE-A HetNet systems which are based on Orthogonal Frequency Division Multiplexing Access (OFDMA) modulation. Our aim is to investigate the aggressive interference issue that appears when different types of base stations are jointly deployed together and especially in two cases, namely Macro-Femtocells and Macro-Picocells co-existence. We propose new practical power adjustment solutions for managing inter-cell interference dynamically for both cases. In the first part dedicated to Femtocells and Macrocell coexistence, we design a MBS-assisted femtocell power adjustment strategy which takes into account femtocells users performance while mitigating the inter-cell interference on victim macrocell users. Further, we propose a new cooperative and context-aware interference mitigation method which is derived for realistic scenarios involving mobility of users and their varying locations. We proved numerically that the Femtocells are able to maintain their interference under a desirable threshold by adjusting their transmission power. Our strategies provide an efficient means for achieving the desired level of macrocell/femtocell throughput trade-off. In the second part of the studies where Picocells are deployed under the umbrella of the Macrocell, we paid a special attention and efforts to the interference management in the situation where Picocells are configured to set up a cell range expansion. We suggest a MBS-assisted collaborative scheme powered by an analytical model to predict the mobility of Macrocell users passing through the cell range expansion area of the picocell. Our goal is to adapt the muting ratio ruling the frequency resource partitioning between both tiers according to the mobility behavior of the range-expanded users, thereby providing an efficient trade-off between Macrocell and Picocell achievable throughputs.