Towards the Quality of Service for VoIP traffic in IEEE 802.11 Wireless Networks

The usage of voice over IP (VoIP) traffic in IEEE 802.11 wireless networks is expected to increase in the near future due to widely deployed 802.11 wireless networks and VoIP services on fixed lines. However, the quality of service (QoS) of VoIP traffic in wireless networks is still unsatisfactory. In this thesis, I identify several sources for the QoS problems of VoIP traffic in IEEE 802.11 wireless networks and propose solutions for these problems. The QoS problems discussed can be divided into three categories, namely, user mobility, VoIP capacity, and call admission control. User mobility causes network disruptions during handoffs. In order to reduce the handoff time between Access Points (APs), I propose a new handoff algorithm, Selective Scanning and Caching, which finds available APs by scanning a minimum number of channels and furthermore allows clients to perform handoffs without scanning, by caching AP information. I also describe a new architecture for the client and server side for seamless IP layer handoffs, which are caused when mobile clients change the subnet due to layer 2 handoffs. I also present two methods to improve VoIP capacity for 802.11 networks, Adaptive Priority Control (APC) and Dynamic Point Coordination Function (DPCF). APC is a new packet scheduling algorithm at the AP and improves the capacity by balancing the uplink and downlink delay of VoIP traffic, and DPCF uses a polling based protocol and minimizes the bandwidth wasted from unnecessary polling, using a dynamic polling list. Additionally, I estimated the capacity for VoIP traffic in IEEE 802.11 wireless networks via theoretical analysis, simulations, and experiments in a wireless test-bed and show how to avoid mistakes in the measurements and comparisons. Finally, to protect the QoS for existing VoIP calls while maximizing the channel utilization, I propose a novel admission control algorithm called QP-CAT (Queue size Prediction using Computation of Additional Transmission), which accurately predicts the impact of new voice calls by virtually transmitting virtual new VoIP traffic

Runtime Detection of a Bandwidth Denial Attack from a Rogue Network-on-Chip

Chips with high computational power are the crux of today’s pervasive complex digital systems. Microprocessor circuits are evolving towards many core designs with the integration of hundreds of processing cores, memory elements and other devices on a single chip to sustain high performance computing while maintaining low design costs. Two decisive paradigm shifts in the semiconductor industry have made this evolution possible: (a) architectural and (b) organizational. At the heart of the architectural innovation is a scalable high speed data communication structure, the network-on-chip (NoC). NoC is an interconnect network for the glueless integration of on-chip components in the modern complex communication centric designs. In the recent days, NoC has replaced the traditional bus based architecture owing to its structured and modular design, scalability and low design cost. The organizational revolution has resulted in a globalized and collaborative supply chain with pervasive use of third party intellectual properties to reduce the time-to-market and overall design costs. Despite the advantages of these paradigm shifts, modern system-on-chips pose a plethora of security vulnerabilities. This work explores a threat model arising from a malicious NoC IP embedded with a hardware trojan affecting the resource availability of on-chip components. A rigorous simulation infrastructure is established to evaluate the feasibility and potency of such an attack. Further, a non-invasive runtime monitoring technique is proposed and thoroughly investigated to ensure the trustworthiness of a third party NoC IP with low overheads

Modélisation et distribution adaptatives de grandes scènes naturelles

Cette thèse traite de la modélisation et la diffusion de grandes scènes 3D naturelles. Nous visons à fournir des techniques pour permettre à des utilisateurs de naviguer à distance dans une scène 3D naturelle, tout en assurant la cohérence botanique et l'interactivité. Tout d'abord, nous fournissons une technique de compression multi-résolution, fondée sur la normalisation, l'instanciation, la décorrélation, et sur le codage entropique des informations géometriques pour des modèles de plantes. Ensuite, nous étudions la transmission efficace de ces objets 3D. L'algorithme de paquétisation proposé fonctionne pour la plupart des représentations multi-résolution d'objet 3D. Nous validons les techniques de paquétisation par des expériences sur un WAN (Wide Area Network), avec et sans contrôle de congestion (Datagram Congestion Control Protocol). Enfin, nous abordons les questions du streaming au niveau de la scène. Nous optimisons le traitement des requêtes du côté serveur en fournissant une structure de données adaptée et nous préparons le terrain pour nos travaux futurs sur l'évolutivité et le déploiement de systèmes distribués de streaming 3D. ABSTRACT : This thesis deals with the modeling and the interactive streaming of large natural 3D scenes. We aim at providing techniques to allow the remote walkthrough of users in a natural 3D scene ensuring botanical coherency and interactivity.First, we provide a compact and progressive representation for botanically realistic plant models. The topological structure and the geometry of the plants are represented by generalized cylinders. We provide a multi-resolution compression scheme, based on standardization and instantiation, on difference-based decorrelation, and on entropy coding. Then, we study efficient transmission of these 3D objects. The proposed packetization scheme works for any multi-resolution 3D representation. We validate our packetization schemes with extensive experiments over a WAN (Wide Area Network), with and without congestion control (Datagram Congestion Control Protocol). Finally, we address issues on streaming at the scene-level. We optimize the viewpoint culling requests on server-side by providing an adapted datastructure and we prepare the ground for our further work on scalability and deployment of distributed 3D streaming systems

Adaptive Modeling and Distribution of Large Natural Scenes

This thesis deals with the modeling and the interactive streaming of large natural 3D scenes. We aim at providing techniques to allow the remote walkthrough of users in a natural 3D scene ensuring botanical coherency and interactivity.First, we provide a compact and progressive representation for botanically realistic plant models. The topological structure and the geometry of the plants are represented by generalized cylinders. We provide a multi-resolution compression scheme, based on standardization and instantiation, on difference-based decorrelation, and on entropy coding. Then, we study efficient transmission of these 3D objects. The proposed packetization scheme works for any multi-resolution 3D representation. We validate our packetization schemes with extensive experiments over a WAN (Wide Area Network), with and without congestion control (Datagram Congestion Control Protocol). Finally, we address issues on streaming at the scene-level. We optimize the viewpoint culling requests on server-side by providing an adapted datastructure and we prepare the ground for our further work on scalability and deployment of distributed 3D streaming systems