Actuellement les communications véhiculaires sont devenues une réalité guidée par diverses applications. Notamment, la diffusion de vidéo de qualité élevée avec des contraintes de faible latence requises par les applications temps réel. Grâce au niveau de compression jamais atteint auparavant, l’encodeur H.265/HEVC est très prometteur pour la diffusion de vidéos en temps réel dans les réseaux ad hoc véhiculaire (VANET). Néanmoins, la qualité de la vidéo reçue est pénalisée par les mauvaises caractéristiques du canal de transmission (disponibilité, non stationnarité, rapport signal à bruit, etc.). Afin d’améliorer et d’assurer une qualité vidéo minimale à la réception nous proposons dans ce travail une optimisation conjointe source-canal-protocole de la transmission en tenant compte à la fois des paramètres de transmission et d’encodage vidéo. Dans un premier temps, nous montrons l’intérêt et le gain apporté par les solutions dites inter-couches « cross-layer ». Par la suite, nous développons deux approches l’une exploitant un « cross-layer » entre la couche application et la couche MAC et une seconde exploitant les protocoles de transports dans l’adaptation du flux vidéo. En ce qui concerne la première approche nous proposons une solution utilisant une gestion hiérarchique des trames au niveau des files d’attentes de la couche MAC, basée sur l’importance des images du flux vidéo. Dans une seconde solution, nous retenons le codage par descriptions multiples comme solution de protection à la source. Les résultats de simulations obtenus pour plusieurs types de scénarios véhiculaires réalistes montrent que les différents schémas de transmission véhiculaire proposés offrent des améliorations significatives en termes de qualité vidéo à la réception et de retard de bout en bout par rapport aux schémas classiques. / At present, vehicular communications have become a reality guided by various applications. In particular, high-quality video delivery with low latency constraints is required for real-time applications. The new state-of-the-art high-effciency video coding (HEVC) standard is very promising for real-time video streaming in vehicular ad hoc networks (VANET). Nevertheless, these networks have variable channel quality and a limited bandwidth that penalizes the overall performances of end-to-end video transmission. In order to meet these constraints, we proposed in this work to consider both transmission and video encoding parameters through a joint source-channel-protocol coding approach to provide an improvement in video transmission. First, we have shown the interest and the gain brought by the "cross-layer" solutions. Then, we developed two approaches. The first one exploits a "crosslayer" solution between the application layer and the Medium Access Control (MAC) layer while the second exploits the transport layer protocols in the adaptation of the video stream. Regarding the first approach, we have proposed solutions to allocate the frames to the most appropriate Access Category (AC) queue on the MAC layer based on the image importance in the video stream. In another solution, we chose multiple descriptions source coding as an error resilient solution. Thus, the simluation results obtained for different realistic vehicular scenarios demonstrate that the proposed transmission schemes offer significant video quality improvements and end-to-end delay reduction compared to conventional transmission schemes.

New generations of video surveillance systems are expected to possess a large-scale network of intelligent video cameras with built-in image processing capabilities. These systems need to be tethered for reasons of bandwidth and power requirements. To support economical installation of video cameras and to manage the huge volume of information flow in these networks, there is a need for new shared-medium daisy-chained physical and medium access control (bus arbitration) layer communication protocols. This thesis describes the design principles of Spatial reuse FireWire Protocol (SFP), a novel request/grant bus arbitration protocol, architected for an acyclic daisy-chained network topology. SFP is a new extension of the IEEE 1394b FireWire architecture. SFP preserves the simple repeat path functionality of FireWire while offering two significant advantages: 1) SFP supports concurrent data transmissions over disjoint segments of the network (spatial reuse of bandwidth), which increases the effective throughput and 2) SFP provides support for priority traffic, which is necessary to handle real-time applications (like packet video), and mission critical applications (like event notifications between cameras) that have strict delay and jitter constraints. The delay and throughput performance of FireWire and SFP were evaluated using discrete-event queuing simulation models built with the CSIM-18 simulation library. Simulation results show that for a homogeneous traffic pattern SFP improves upon the throughput of IEEE 1394b by a factor of 2. For a traffic pattern typical of video surveillance applications, throughput increases by a factor of 7. Simulation results demonstrate that IEEE 1394b asynchronous stream based packet transactions offer better delay performance than isochronous transactions for variable bit rate video like MPEG-2 and MPEG-4. SFP extends this observation by supporting priority traffic. QoS for packet video is provided in SFP by mapping individual asynchronous stream packets to the three priority classes.

This dissertation is composed of two independent studies: Cellular research and WBAN (Wireless Body Area Network) research. Both investigations are directed towards improving the system performance in wireless communication systems in terms of Quality of Service (QoS) and system capacity. For the Cellular research part, this dissertation will present novel user-specific QoS requirements as defined by their respective Mean Opinion Score (MOS) formulas, and associated schedulers for wireless applications and systems that optimize spectral allocation. User-specific QoS requirements are defined and several methods to make use of such requirements to maximum the spectral utilization are presented. Five User-Specific QoS Aware (USQA) schedulers are proposed that consider the user-specific QoS requirements in the allocation of spectral resources. Schedulers are introduced that dynamically adapt to the user-specific QoS requirements to improve quality as measured by the MOS, or the system capacity, or can improve both the quality and system capacity. Due to the different cell deployment arrangements and inter-cell interference in heterogeneous networks in comparison to homogeneous networks, the USQA scheduling is also analyzed and the system performance is evaluated in such networks. Throughput improvements of File Transfer Protocol (FTP) applications benefiting from the rate adaptation and MAC (Media Access Control) scheduling algorithms for video applications that incorporate user-specific QoS requirements to improve system capacity are demonstrated. Another novel approach recognizes that the user-specific frequency sensitivity can be used to improve capacity. There is considerable variation in the audible range of frequencies that can be perceived by individuals, especially at the high frequency end, which is primarily affected by a gradual decline with age. This can be utilized to improve the system performance by personalizing the VoIP codecs and decreasing the user's source data rate for people from an older age group and thus increase the system capacity. Given the potentially substantial system performance gain resulting from the USQA schedulers, it is critical to analyze their feasibility and complexity in practical LTE (4G cellular) and future wireless systems. From the LTE system perspective, LTE QoS end-to-end signaling procedures are addressed, and corresponding protocol adaptations are analyzed in order to support the USQA schedulers. In addition, the optimal scheduling period is analyzed that trades off between performance gain and implementation complexity. In the WBAN research, MIMO (Multiple Input Multiple Output) in vivo antenna technologies are introduced and are motivated by the high data rate requirements of wirelessly transmitted low-delay High Definition (HD) video during Minimally Invasive Surgery (MIS). MIMO in vivo technologies are proposed to be used in the in vivo environments to enhance and determine the maximum data transmission rate while satisfying the Specific Absorption Rate (SAR) power limitations. Various factors are considered in the MIMO in vivo study including antenna separation, antenna angular positions, human body size, and system bandwidth to determinate the maximum data rate that can be supported.

Semantic role labeling is an important stage in systems for Natural Language Understanding. The basic problem is one of identifying who did what to whom for each predicate in a sentence. Thus labeling is a two-step process: identify constituent phrases that are arguments to a predicate, then label those arguments with appropriate thematic roles. Existing systems for semantic role labeling use machine learning methods to assign roles one-at-a-time to candidate arguments. There are several drawbacks to this general approach. First, more than one candidate can be assigned the same role, which is undesirable. Second, the search for each candidate argument is exponential with respect to the number of words in the sentence. Third, single-role assignment cannot take advantage of dependencies known to exist between semantic roles of predicate arguments, such as their relative juxtaposition. And fourth, execution times for existing algorithm are excessive, making them unsuitable for real-time use. This thesis seeks to obviate these problems by approaching semantic role labeling as a multi-argument classification process. It observes that the only valid arguments to a predicate are unembedded constituent phrases that do not overlap that predicate. Given that semantic role labeling occurs after parsing, this thesis proposes an algorithm that systematically traverses the parse tree when looking for arguments, thereby eliminating the vast majority of impossible candidates. Moreover, instead of assigning semantic roles one at a time, an algorithm is proposed to assign all labels simultaneously; leveraging dependencies between roles and eliminating the problem of duplicate assignment. Experimental results are provided as evidence to show that a combination of the proposed argument identification and multi-argument classification algorithms outperforms all existing systems that use the same syntactic information.

It is widely accepted that low energy consumption is the most important requirement when designing components and systems for a wireless sensor network (WSN). The greatest energy consumer of each node within a WSN is the radio transceiver and as such, it is important that this component be used in an extremely energy e±cient manner. One method of reducing the amount of energy consumed by the radio transceiver is to turn it off and allow nodes to enter a sleep mode. The algorithms that directly control the radio transceiver are traditionally grouped into the Medium Access Control (MAC) layer of a communication protocol stack. This thesis introduces the emerging field of wireless sensor networks and outlines the requirements of a MAC protocol for such a network. Current MAC protocols are reviewed in detail with a focus on how they utilize this energy saving sleep mode as well as performance problems that they suffer from. A proposed new method of coordinating the use of this sleep mode between nodes in the network is specifed and described. The proposed new protocol is analytically compared with existing protocols as well as with some fundamental performance limits. The thesis concludes with an analysis of the results as well as some recommendations for future work.

a course vers des débits plus élevés pour les utilisateurs de réseaux cellulaires devient plus difficile chaque jour. La nouvelle technologie surnommée "Femtocell" est considérée comme le potentiel sauveur des opérateurs menacés par la concurrence du Wifi. Ce point d'accès résidentiel au réseau cellulaire offre une meilleure couverture et un plus haut débit aux utilisateurs situés en intérieur. Dans cette thèse, nous évaluons séparément, la capacité utile offerte par un point d'accès Wifi et par un point d'accès "Femtocell". Dans la première partie nous proposons un modèle réaliste du mécanisme d'accès à la ressource du Wifi appelé EDCA. Notre modèle est basé sur les chaînes de Markov. Nous évitons les principales approximations faites dans les modèles antérieurs en prenant en compte, un régime non saturé et un canal non idéal. Ainsi nous pouvons obtenir les performances attendues avec plus de précision pour différentes charges de trafic et divers taux d'erreur binaire (BER). Dans un second temps nous évaluons les performances des Femtocells en proposant une nouvelle planification de la ressource radio, ce qui est considérée comme un des principaux défis étant donné le déploiement imprévisible des Femtocells par leurs propres utilisateurs. Nous proposons dans cette thèse différents schéma de "double" réutilisation des fréquences consistant à allouer au femtocell les fréquences déjà utilisées par les macrocells avoisinantes. Nous évaluons les performances en termes de puissance de signal reçue et rapport signal à interférence plus bruit. Nous montrons que femtocells contribue à une amélioration significative par rapport à une couverture macrocell classique.

Un réseau ad hoc est une collection de stations communicant au travers d'un lien sans fil sans l'aide d'aucune autre infrastructure. L'un des principaux défis dans la conception de protocoles pour ce type de réseaux est l'accès au médium. Le standard IEEE 802.11 définit un mode pour les réseaux ad hoc. Cependant, le protocole MAC (Medium Access Control) décrit montre des problèmes d'équité et d'efficacité. Dans cette thèse j'ai d'abord évalué les performances d'algorithmes et de protocoles MAC existants et mis en évidence leurs problèmes de performance grâce à un modèle exploitant le formalisme des algèbres de processus stochastiques. Grâce à ces résultats j'ai proposé deux protocoles MAC (MadMac et PAS) pour les réseaux ad hoc et les réseaux locaux sans fil. Nos protocoles sont différents de ceux présentés dans la littérature car nous essayons de répondre au compromis équité-efficacité et les solutions que nous proposons sont à la fois équitables et efficaces

<p>The Internet has mainly been interconnecting stationary computers by wired links, but an increasing number of mobile clients require wireless communication. One way to connect these clients is to use the Universal Mobile Telecommunication System, UMTS. UMTS is a third generation mobile system. </p><p>A network can be seen as nodes interconnected by links. The functionality of the nodes can be described as a layered hierarchy. A reference model for this hierarchy was developed by OSI. In this model the second lowest layer is called data link layer. The data link layer is responsible for making the raw transmission appear error free to upper layers. </p><p>The focus for this thesis is the data link layer in the UMTS. Compared to the data link layer in a wired scenario it contains more control and error correction mechanisms. These mechanisms use a lot of timers and triggers, which makes it very difficult to analyze them mathematically. Therefore simulation is the preferred method. </p><p>For the simulations the network simulator version 2 was used. This is an open source discrete event simulator. It has a modularized wireless stack already implemented. This can not be used to simulate UMTS though. Some modules in this stack were replaced by a new implementation to make simulations on UMTS possible. </p><p>Tests were performed on the new implementation and the results were what could be expected. The results were also consistent with previous research in the area.</p>

<p>This Master Thesis presents the design of the core of a fixed point general purpose multimedia DSP processor (MDSP) and its instruction set. This processor employs parallel processing techniques and specialized addressing models to speed up the processing of multimedia applications. </p><p>The MDSP has a dual MAC structure with one enhanced MAC that provides a SIMD, Single Instruction Multiple Data, unit consisting of four parallel data paths that are optimized for accelerating multimedia applications. The SIMD unit performs four multimedia- oriented 16- bit operations every clock cycle. This accelerates computationally intensive procedures such as video and audio decoding. The MDSP uses a memory bank of four memories to provide multiple accesses of source data each clock cycle.</p>

<p>The wide spread use of IEEE Wireless LAN 802.11 in battery operated mobile devices introduced the need of power consumption optimization while meeting Quality-of-Service (QoS) requirements of applications connected through the wireless network. The IEEE 802.11 standard specifies a baseline power saving mechanism, hereafter referred to as standard Power Save Mode (PSM), and the IEEE 802.11e standard specifies the Automatic Power Save Delivery (APSD) enhancement which provides support for real-time applications with QoS requirements. The latest amendment to the WLAN 802.11 standard is the IEEE 802.11n standard which enables the use of much higher data rates by including enhancements in the Physical and MAC Layer. In this thesis, different 802.11n MAC power saving and QoS optimization possibilities are analyzed comparing against existing power saving mechanisms.</p><p>Initially, the performance of the existing power saving mechanisms PSM and Unscheduled-APSD (UAPSD) are evaluated using the 802.11n process model in the OPNET simulator and the impact of frame aggregation feature introduced in the MAC layer of 802.11n was analyzed on these power saving mechanisms. From the performance analysis it can be concluded that the frame aggregation will be efficient under congested network conditions. When the network congestion level increases, the signaling load in UAPSD saturates the channel capacity and hence results in poor performance compared to PSM. Since PSM cannot guarantee the minimum QoS requirements for delay sensitive applications, a better mechanism for performance enhancement of UAPSD under dynamic network conditions is proposed.</p><p>The functionality and performance of the proposed algorithm is evaluated under different network conditions and using different contention settings. From the performance results it can be concluded that, by using the proposed algorithm the congestion level in the network is reduced dynamically thereby providing a better power saving and QoS by utilizing the frame aggregation feature efficiently.</p>