Les progrès réalisés en systèmes micro-électro-mécaniques couplés avec leur convergence vers les systèmes de communication sans fil, ont permis l'émergence des réseaux de capteurs sans fil (RCSF). Les contraintes de ces réseaux font que tous les efforts soient fournis pour proposer des solutions économes en énergie. Avec les récents développements des technologies CMOS, des capteurs d'images à faible coût ont été développés. En conséquence, un nouveau dérivé des RCSF, qui sont les Réseaux de Capteurs Vidéo Sans Fil (RCVSF), a été proposé. La particularité des données vidéo ainsi que les contraintes inhérentes aux nœuds ont introduit de nouveaux défis. Dans cette thèse, nous proposons deux solutions basées sur l'approche inter-couches pour la livraison de la vidéo sur les RCVSF. La première solution propose un nouveau schéma de compression vidéo adaptatif, efficace en énergie et basé sur la norme de compression vidéo H.264/AVC. Le flux vidéo est ensuite géré par une version améliorée du protocole MMSPEED que nous proposons et notons EQBSA-MMSPEED. Les résultats des simulations montrent que la durée de vie du réseau est étendue de 33%, tout en améliorant la qualité du flux vidéo reçu de 12%. Dans la deuxième solution, nous enrichissons le schéma de compression de modèles mathématiques pour prévoir la consommation d'énergie et la distorsion de l'image lors des phases d'encodage et de transmission. Le flux vidéo est géré par un nouveau protocole de routage efficace en énergie et à fiabilité améliorée noté ERMM. Comparée à une approche basique, cette solution réalise une extension de la durée de vie du réseau de 15%, tout en améliorant la qualité du flux vidéo reçu de 35%. / Thanks to the valuable advances in Micro Electro-Mechanical Systems coupled with their convergence to wireless communication systems, the Wireless Sensor Networks (WSN). In the WSN context, all the efforts are made in order to propose energy-efficient solutions. With the recent developments in CMOS technology, low-cost imaging sensors have been developed. As a result, a new derivative of the WSN, which is the Wireless Video Sensor Network (WVSN), has been proposed. The particularities of the video data as well as the inherent constraints of the nodes have introduced new challenges. In this thesis, we propose two cross-layer based solutions for video delivery over the WVSN. The first solution proposes a new energy efficient and adaptive video compression scheme dedicated to the WVSNs, based on the H.264/AVC video compression standard. The video stream is then handled by an enhanced version of MMSPEED protocol, that we propose and note EQBSA-MMSPEED. Performance evaluation shows that the lifetime of the network is extended by 33%, while improving the video quality of the received stream by 12%. In the second solution, we enrich our compression scheme with mathematical models to predict the energy consumption and the video distortion during the encoding and the transmission phases. The video stream is then handled by a novel energy efficient and improved reliability routing protocol, that we note ERMM. Compared to a basic approach, this solution is extending the network lifetime by 15%, while improving the quality of the received video stream by 35%.

La presencia de topologías multi-salto en comunicaciones inalámbricas de todo tipo es cada vez más apreciable, esperándose además que esta tendencia se mantenga en un futuro cercano. A pesar de que inicialmente fueran concebidos para solventar la falta de infraestructura subyacente en ciertos escenarios concretos, estos despliegues han acaparado el interés de diferentes actores del ámbito de las comunicaciones (incluyendo los operadores), con lo que es razonable pensar que su relevancia irá creciendo paulatinamente. De hecho, existen diversas iniciativas en algunos foros de estandarización que de alguna manera corroboran este hecho. Hay que tener en cuenta, por otro lado, otros factores adicionales (como la eclosión que se ha producido en el campo de las redes de sensores inalámbricos) que seguramente fomentarán el uso de estas topologías.A pesar de la creciente actividad en el ámbito de los despliegues multi-salto, sigue siendo necesario establecer, de manera cuantitativa, cuáles son sus posibles beneficios, tanto para los usuarios finales de los sistemas de comunicación, como para los operadores, especialmente teniendo en cuenta el elevado grado de heterogeneidad que también caracterizará las redes inalámbricas.Por otro lado, en lo que se refiere a los algoritmos y protocolos a ser empleados sobre este tipo de topologías, y a pesar de la intensa labor de investigación que sobre ellos se ha realizado recientemente, queda aún un número relevante de aspectos a analizar. En primer lugar, el mero hecho de que sus requerimientos y retos iniciales hayan variado de manera sustancial puede, y debe, influenciar sus principios básicos. Además, es necesario acometer verificaciones de los mismos sobre plataformas reales y, así mismo, asegurar que las evaluaciones que se realicen con técnicas de simulación utilicen modelos reales que permitan reflejar de manera fidedigna las condiciones que se dan en la realidad.Esta Tesis afronta, en primer lugar, la evaluación cuantitativa de la mejora que es posible alcanzar al utilizar topologías inalámbricas multi-salto para extender despliegues de red más tradicionales. Un primer aspecto que es razonable considerar es la ampliación de la cobertura que se consigue; en este caso se ha realizado un análisis que sigue un doble enfoque, analítico y mediante técnicas de simulación, para determinar es la ganancia que se logra. Se ha partido de dos modelos de red complementarios entre sí, asumiendo en el primero de ellos una falta total de planificación previa, mientras que en el segundo se utiliza un emplazamiento óptimo de los elementos de conexión a la red. Se ha comprobado que, a pesar de sus características claramente antagónicas, los resultados obtenidos con ambos escenarios son similares entre sí. Además, se concluye que, a pesar de que la ampliación de la cobertura que se alcanza es muy relevante, es posible establecer un límite razonable para el número máximo de saltos a emplear, ya que la mejoría adicional al incrementar la longitud de la ruta deja de ser apreciable a partir del mismo. Este aspecto se podría aprovechar para influir en el diseño de las técnicas de encaminamiento a emplear sobre este tipo de topologías.Se analizan también otras mejoras adicionales, utilizando un escenario en el que predomina sobremanera la heterogeneidad de los elementos de conexión a la red, e integrando las extensiones multi-salto con un algoritmo de selección de acceso genérico, que permite modular el peso que tienen las diferentes entidades (tanto el terminal de usuario como la propia red), así como diversos parámetros y restricciones a considerar, a la hora de determinar la alternativa de conexión óptima. Se comprueba que, tanto para los usuarios, gracias a la mejora de la calidad del servicio que perciben, como para la red, que incrementa el tráfico que es capaz de cursar, el uso de comunicaciones multi-salto puede resultar altamente atractivo.En segundo lugar, también se afronta la mejora de las técnicas de encaminamiento que tradicionalmente se emplean sobre las redes multi-salto, basadas en minimizar el número de saltos entre los dos extremos de la comunicación. Para ello, y utilizando el paradigma de Cross-Layer Optimisation, se propone una versión mejorada del protocolo DSR, denominada SADSR, que emplea la información relativa a la calidad de los enlaces subyacentes para modular el algoritmo de selección de ruta. Destacar que se acomete una verificación experimental de dicha propuesta, contestando, de este modo, a una de las reivindicaciones más importantes en este campo. Los resultados obtenidos permiten inferir que las prestaciones de la propuesta realizada en el marco de esta Tesis son superiores a los de la versión original del DSR.A pesar del evidente valor que las validaciones empíricas aportan, tienen la limitación de que es complicado establecer topologías con un número elevado de nodos, o acometer experimentos con una pauta repetitiva para determinar un comportamiento promedio. Es por ello que también se acomete un análisis mediante técnicas de simulación, en el que se compara SADSR con la versión original del DSR, así como con otras propuestas que han acaparado el interés por parte de la comunidad científica. Los resultados que se derivan a raíz de la evaluación llevada a cabo no hacen sino corroborar lo que ya adelanta la verificación experimental, ya que las prestaciones del SADSR son muy superiores a las del resto de alternativas analizadas.Para llevar a cabo el análisis anterior es fundamental el uso de un modelo de canal que refleje, con el mayor grado de exactitud posible, un comportamiento realista. Para ello, en la Tesis se afronta el diseño, implementación y posterior integración en la plataforma Network Simulator de BEAR, un modelo de canal basado en filtrado auto-regresivo, que se caracteriza principalmente por emular la aparición de errores a ráfagas que se observa en entornos reales. En ese sentido, se parte de un extenso conjunto de medidas que permite corroborar el correcto funcionamiento de la propuesta. / The presence of multi-hop topologies within all types of wireless communications is becoming more and more common, and this tendency is expected to be maintained in the near future. Although they were originally conceived to compensate the lack of subjacent infrastructure in certain scenarios, these deployments have attracted the interest of different actors in the wireless communications value chain (including network operators) and thus it is logical to think that their relevance will gradually increase. In fact, there already exist some standardization initiatives which corroborate this point to some extent. Furthermore, other additional factors, such as the rapid growth which has been seen in wireless sensor technologies, also strengthen the use of these topologies..In spite of the growing activity in the multi-hop deployment field, it is still necessary to establish, in a quantitative way, their potential benefits, both for the end-users of the communication systems, as well as for the operators, considering, in addition, the high degree of heterogeneity which will characterize wireless networks in the future.On the other hand, as far as algorithms and protocols to be used over this type of topology are concerned, and despite the intense research which has been conducted into them, there is still a large number of issues to be tackled. First, the simple fact that their initial requirements and challenges have been modified can, and must, influence their basic principles. In addition, it becomes necessary to address their validation on real platforms and, on the other hand, to ensure that simulation-based evaluations of their performance make use of realistic models which accurately reflect the conditions which are observed in real scenarios.This dissertation tackles, on the one hand, the quantitative evaluation of the improvements which are achievable when using multi-hop topologies to extend legacy network deployments. One first aspect which is logical to consider is the increase in the coverage which is brought about. In this sense, a two-fold approach has been followed, employing both an analytical as well as a simulation-based analysis, to establish what the gain is. Two network models have been used, being complementary to each other; the first one assumes a complete lack of network planning for the deployment of the access elements, while the second one assumes an optimum distribution of them. Although their characteristics are completely different, the results are somehow similar for both cases. Furthermore, it can be concluded that, despite the coverage extension which can be obtained, it is indeed possible to establish a reasonable limit on the maximum number of hops to be used, since the improvement becomes less relevant for higher values. This aspect could influence the design of routing techniques to be used over this type of topology.Furthermore, other additional benefits have been also analyzed, using a network deployment in which the presence of heterogeneity (multi-access) is evident. The multi-hop extensions have been integrated within a generic access selection algorithm which enables the modification of the weights which are assigned to the different entities (both the end-user terminals and the network) as well as to the set of parameters and constraints to be considered when selecting the most appropriate access alternative. It is concluded that for both the end-users, who improve their perception of the quality of service, and the network, which is able to increase the overall amount of traffic possible to be handled, multi-hop extensions are certainly beneficial.In addition, the dissertation also tackles the improvement of the routing techniques which are traditionally employed over multi-hop networks, which are based on minimizing the number of hops between the two sides of the communication. To accomplish this, and using the Cross-Layer Optimisation paradigm, an improved version of the DSR protocol is proposed, namely SADSR. It uses information about the subjacent link qualities to modulate the route selection algorithm. It is worth highlighting that a fully empirical (on a real platform) validation has been conducted, addressing one of the most pressing demands within this field. The results obtained allow us to infer that the proposal made in the framework of this dissertation is clearly outperforming the original DSR version.Although the added value provided by empirical validations is unquestionable, they also have some limitations. First, they normally do not favour the establishment of large topologies, or to undertake repetitive experiments aimed at finding an average behaviour. In this sense, a simulation-based analysis is also used so as to compare the SADSR with the original DSR version as well as with other proposals which have recently attracted interest from the scientific community. The results obtained by the validation carried out on a real platform are confirmed, since the performance brought about by the SADSR is somewhat higher than that of the other strategies.In order to perform the previous analysis the use of a realistic channel model, able to capture with a high degree of accuracy the behaviour exhibited on real platforms, is mandatory. To fulfil this requirement, the dissertation also tackles the design, implementation, and integration within the Network Simulator platform of BEAR, a channel model based on auto-regressive filtering. It is mainly characterized by being able to emulate the bursty presence of errors which is observed over real channels. The design is based on an extensive set of measurements which is used to assess the validity of the proposal.

Un dels aspectes claus en el disseny i gestió de les xarxes sense fils d'accés de banda ampla és l'ús eficient dels recursos radio. Des del punt de vista de l'operador, l'ample de banda és un bé escàs i preuat que s´ha d'explotar i gestionar de la forma més eficient possible tot garantint la qualitat del servei que es vol proporcionar. Per altra banda, des del punt de vista del usuari, la qualitat del servei ofert ha de ser comparable al de les xarxes fixes, requerint així un baix retard i una baixa pèrdua de paquets per cadascun dels fluxos de dades entre la xarxa i l'usuari. Durant els darrers anys s´han desenvolupat nombroses tècniques i algoritmes amb l'objectiu d'incrementar l'eficiència espectral. Entre aquestes tècniques destaca l'ús de múltiples antenes al transmissor i al receptor amb l'objectiu de transmetre diferents fluxos de dades simultaneament sense necessitat d'augmentar l'ample de banda. Per altra banda, la optimizació conjunta de la capa d'accés al medi i la capa física (fent ús de l'estat del canal per tal de gestionar de manera optima els recursos) també permet incrementar sensiblement l'eficiència espectral del sistema.L'objectiu d'aquesta tesi és l'estudi i desenvolupament de noves tècniques d'adaptació de l'enllaç i gestió dels recursos ràdio aplicades sobre sistemes d'accés ràdio de propera generació (Beyond 3G). Els estudis realitzats parteixen de la premissa que el transmisor coneix (parcialment) l'estat del canal i que la transmissió es realitza fent servir un esquema multiportadora amb múltiples antenes al transmisor i al receptor. En aquesta tesi es presenten dues línies d'investigació, la primera per casos d'una sola antenna a cada banda de l'enllaç, i la segona en cas de múltiples antenes. En el cas d'una sola antena al transmissor i al receptor, un nou esquema d'assignació de recursos ràdio i priorització dels paquets (scheduling) és proposat i analitzat integrant totes dues funcions sobre una mateixa entitat (cross-layer). L'esquema proposat té com a principal característica la seva baixa complexitat i que permet operar amb transmissions multimedia. Alhora, posteriors millores realitzades per l'autor sobre l'esquema proposat han permès també reduir els requeriments de senyalització i combinar de forma óptima usuaris d'alta i baixa mobilitat sobre el mateix accés ràdio, millorant encara més l'eficiència espectral del sistema. En cas d'enllaços amb múltiples antenes es proposa un nou esquema que combina la selecció del conjunt optim d'antenes transmissores amb la selecció de la codificació espai- (frequència-) temps. Finalment es donen una sèrie de recomanacions per tal de combinar totes dues línies d'investigació, així con un estat de l'art de les tècniques proposades per altres autors que combinen en part la gestió dels recursos ràdio i els esquemes de transmissió amb múltiples antenes. / Uno de los aspectos claves en el diseño y gestión de las redes inalámbricas de banda ancha es el uso eficiente de los recursos radio. Desde el punto de vista del operador, el ancho de banda es un bien escaso y valioso que se debe explotar y gestionar de la forma más eficiente posible sin afectar a la calidad del servicio ofrecido. Por otro lado, desde el punto de vista del usuario, la calidad del servicio ha de ser comparable al ofrecido por las redes fijas, requiriendo así un bajo retardo y una baja tasa de perdida de paquetes para cada uno de los flujos de datos entre la red y el usuario. Durante los últimos años el número de técnicas y algoritmos que tratan de incrementar la eficiencia espectral en dichas redes es bastante amplio. Entre estas técnicas destaca el uso de múltiples antenas en el transmisor y en el receptor con el objetivo de poder transmitir simultáneamente diferentes flujos de datos sin necesidad de incrementar el ancho de banda. Por otro lado, la optimización conjunta de la capa de acceso al medio y la capa física (utilizando información de estado del canal para gestionar de manera óptima los recursos) también permite incrementar sensiblemente la eficiencia espectral del sistema.El objetivo de esta tesis es el estudio y desarrollo de nuevas técnicas de adaptación del enlace y la gestión de los recursos radio, y su posterior aplicación sobre los sistemas de acceso radio de próxima generación (Beyond 3G). Los estudios realizados parten de la premisa de que el transmisor conoce (parcialmente) el estado del canal a la vez que se considera que la transmisión se realiza sobre un sistema de transmisión multiportadora con múltiple antenas en el transmisor y el receptor. La tesis se centra sobre dos líneas de investigación, la primera para casos de una única antena en cada lado del enlace, y la segunda en caso de múltiples antenas en cada lado. Para el caso de una única antena en el transmisor y en el receptor, se ha desarrollado un nuevo esquema de asignación de los recursos radio así como de priorización de los paquetes de datos (scheduling) integrando ambas funciones sobre una misma entidad (cross-layer). El esquema propuesto tiene como principal característica su bajo coste computacional a la vez que se puede aplicar en caso de transmisiones multimedia. Posteriores mejoras realizadas por el autor sobre el esquema propuesto han permitido también reducir los requisitos de señalización así como combinar de forma óptima usuarios de alta y baja movilidad. Por otro lado, en caso de enlaces con múltiples antenas en transmisión y recepción, se presenta un nuevo esquema de adaptación en el cual se combina la selección de la(s) antena(s) transmisora(s) con la selección del esquema de codificación espacio-(frecuencia-) tiempo. Para finalizar, se dan una serie de recomendaciones con el objetivo de combinar ambas líneas de investigación, así como un estado del arte de las técnicas propuestas por otros autores que combinan en parte la gestión de los recursos radio y los esquemas de transmisión con múltiples antenas. / In Broadband Wireless Access systems the efficient use of the resources is crucial from many points of views. From the operator point of view, the bandwidth is a scarce, valuable, and expensive resource which must be exploited in an efficient manner while the Quality of Service (QoS) provided to the users is guaranteed. On the other hand, a tight delay and link quality constraints are imposed on each data flow hence the user experiences the same quality as in fixed networks. During the last few years many techniques have been developed in order to increase the spectral efficiency and the throughput. Among them, the use of multiple antennas at the transmitter and the receiver (exploiting spatial multiplexing) with the joint optimization of the medium access control layer and the physical layer parameters.In this Ph.D. thesis, different adaptive techniques for B3G multicarrier wireless systems are developed and proposed focusing on the SS-MC-MA and the OFDM(A) (IEEE 802.16a/e/m standards) communication schemes. The research lines emphasize into the adaptation of the transmission having (Partial) knowledge of the Channel State Information for both; single antenna and multiple antenna links. For single antenna links, the implementation of a joint resource allocation and scheduling strategy by including adaptive modulation and coding is investigated. A low complexity resource allocation and scheduling algorithm is proposed with the objective to cope with real- and/or non-real- time requirements and constraints. A special attention is also devoted in reducing the required signalling. However, for multiple antenna links, the performance of a proposed adaptive transmit antenna selection scheme jointly with space-time block coding selection is investigated and compared with conventional structures. In this research line, mainly two optimizations criteria are proposed for spatial link adaptation, one based on the minimum error rate for fixed throughput, and the second focused on the maximisation of the rate for fixed error rate. Finally, some indications are given on how to include the spatial adaptation into the investigated and proposed resource allocation and scheduling process developed for single antenna transmission.

Wireless sensor networks (WSN) are event based systems that rely on the collective effort of densely deployed sensor nodes continuously observing a physical phenomenon. The spatio-temporal correlation between the sensor observations and the cross-layer design advantages are significant and unique to the design of WSN. Due to the high density in the network topology, sensor observations are highly correlated in the space domain. Furthermore, the nature of the energy-radiating physical phenomenon constitutes the temporal correlation between each consecutive observation of a sensor node. This unique characteristic of WSN can be exploited through a cross-layer design of communication functionalities to improve energy efficiency of the network. In this thesis, several key elements are investigated to capture and exploit the correlation in the WSN for the realization of advanced efficient communication protocols. A theoretical framework is developed to capture the spatial and temporal correlations in WSN and to enable the development of efficient communication protocols. Based on this framework, spatial Correlation-based Collaborative Medium Access Control (CC-MAC) protocol is described, which exploits the spatial correlation in the WSN in order to achieve efficient medium access. Furthermore, the cross-layer module (XLM), which melts common protocol layer functionalities into a cross-layer module for resource-constrained sensor nodes, is developed. The cross-layer analysis of error control in WSN is then presented to enable a comprehensive comparison of error control schemes for WSN. Finally, the cross-layer packet size optimization framework is described.

As more and more wireless applications/services emerge in the market, the already heavily crowded radio spectrum becomes much scarcer. Meanwhile, however,as it is reported in the recent literature, there is a large amount of radio spectrum that is under-utilized. This motivates the concept of cognitive radio wireless networks that allow the unlicensed secondary-users (SUs) to dynamically use the vacant radio spectrum which is not being used by the licensed primary-users (PUs). In this dissertation, we investigate protocol design for both the synchronous and asynchronous cognitive radio networks with emphasis on the medium access control (MAC) layer. We propose various spectrum sharing schemes, opportunistic packet scheduling schemes, and spectrum sensing schemes in the MAC and physical (PHY) layers for different types of cognitive radio networks, allowing the SUs to opportunistically utilize the licensed spectrum while confining the level of interference to the range the PUs can tolerate. First, we propose the cross-layer based multi-channel MAC protocol, which integrates the cooperative spectrum sensing at PHY layer and the interweave-based spectrum access at MAC layer, for the synchronous cognitive radio networks. Second, we propose the channel-hopping based single-transceiver MAC protocol for the hardware-constrained synchronous cognitive radio networks, under which the SUs can identify and exploit the vacant channels by dynamically switching across the licensed channels with their distinct channel-hopping sequences. Third, we propose the opportunistic multi-channel MAC protocol with the two-threshold sequential spectrum sensing algorithm for asynchronous cognitive radio networks. Fourth, by combining the interweave and underlay spectrum sharing modes, we propose the adaptive spectrum sharing scheme for code division multiple access (CDMA) based cognitive MAC in the uplink communications over the asynchronous cognitive radio networks, where the PUs may have different types of channel usage patterns. Finally, we develop a packet scheduling scheme for the PU MAC protocol in the context of time division multiple access (TDMA)-based cognitive radio wireless networks, which is designed to operate friendly towards the SUs in terms of the vacant-channel probability. We also develop various analytical models, including the Markov chain models, M=GY =1 queuing models, cross-layer optimization models, etc., to rigorously analyze the performance of our proposed MAC protocols in terms of aggregate throughput, access delay, and packet drop rate for both the saturation network case and non-saturation network case. In addition, we conducted extensive simulations to validate our analytical models and evaluate our proposed MAC protocols/schemes. Both the numerical and simulation results show that our proposed MAC protocols/schemes can significantly improve the spectrum utilization efficiency of wireless networks.

We study the problem of joint congestion control, routing and MAC layer scheduling in multi-hop wireless mesh networks, where the nodes in the network are subjected to energy expenditure rate constraints. As wireless scenario does not allow all the links to be active all the time, only a subset of given links can be active simultaneously. We model the inter-link interference using the link contention graph. All the nodes in the network are power-constrained and we model this constraint using energy expenditure rate matrix. Then we formulate the problem as a network utility maximization (NUM) problem. We notice that this is a convex optimization problem with affine constraints. We apply duality theory and decompose the problem into two sub-problems namely, network layer congestion control and routing problem, and MAC layer scheduling problem. The source adjusts its rate based on the cost of the least cost path to the destination where the cost of the path includes not only the prices of the links in it but also the prices associated with the nodes on the path. The MAC layer scheduling of the links is carried out based on the prices of the links. The optimal scheduler selects that set of non-interfering links, for which the sum of link prices is maximum. We study the effects of energy expenditure rate constraints of the nodes on the maximum possible network utility. It turns out that the dominant of the two constraints namely, the link capacity constraint and the node energy expenditure rate constraint affects the network utility most. Also we notice the fact that the energy expenditure rate constraints do not affect the nature of optimal link scheduling problem. Following this fact, we study the problem of distributed link scheduling. Optimal scheduling requires selecting independent set of maximum aggregate price, but this problem is known to be NP-hard. We first show that as long as scheduling policy selects the set of non-interfering links, it can not go unboundedly away from the optimal solution of network utility maximization problem. Then we proceed and evaluate a simple greedy scheduling algorithm. Analytical bounds on performance are provided and simulations indicate that the greedy heuristic performs well in practice.

Multimedia services are the killer applications on next generation convergent networks. Video contents are the most resource consuming part of a multimedia flux. Video transmission, video multicast and video conferencing services are the most popular types of video communication with increasing difficulty levels. Four main parts of the distributed cross-layer scalable multimedia services over next generation convergent networks are considered in this research work, both from the architecture and performance point of views. Firstly, we evaluate the performance of scalable multimedia transmissions over an overlay network. For that, we evaluate the performance of scalable video end-to-end transmissions over EvalSVC. It is capable of evaluating the end-to-end transmission of SVC bit-streams. The output results are both objective and subjective metrics of the video transmission. Through the interfaces with real networks and an overlay simulation platform, the transmission performance of different types of SVC scalability and AVC bit-streams on a bottle-neck and an overlay network will be evaluated. This evaluation is new because it is conducted on the end-to-end transmission of SVC contents and not on the coding performance. Next, we will study the multicast mechanism for multimedia content over an overlay network in the following part of this PhD thesis. Secondly, we tackle the problems of the distributed cross-layer scalable multimedia multicast over the next generation convergent networks. For that, we propose a new application-network cross layer multi-variable cost function for application layer multicast of multimedia delivery over convergent networks. It optimizes the variable requirements and available resources from both the application and the network layers. It can dynamically update the available resources required for reaching a particular node on the ALM's media distribution tree. Mathematical derivation and theoretical analysis have been provided for the newly proposed cost function so that it can be applied in more general cases of different contexts. An evaluation platform of an overlay network built over a convergent underlay network comprised of a simulated Internet topology and a real 4G mobile WiMAX IEEE802.16e wireless network is constructed. If multicast is the one-to-many mechanism to distribute the multimedia content, a deeper study on the many-to-many mechanism will be done in the next part of the thesis through a new architecture for video conferencing services. Thirdly, we study the distributed cross-layer scalable video conferencing services over the overlay network. For that, an enriched human perception-based distributed architecture for scalable video conferencing services is proposed with theoretical models and performance analysis. Rich theoretical models of the three different architectures: the proposed perception-based distributed architecture, the conventional centralized architecture and perception-based centralized architecture have been constructed by using queuing theory to reflect the traffic generated, transmitted and processed at the perception-based distributed leaders, the perception-based centralized top leader, and the centralized server. The performance of these three different architectures has been considered in 4 different aspects. While the distributed architecture is better than the centralized architecture for a scalable multimedia conferencing service, it brings many problems to users who are using a wireless network to participate into the conferencing service. A special solution should be found out for mobile users in the next part of the thesis. Lastly, the distributed cross-layer scalable video conferencing services over the next generation convergent network is enabled. For that, an IMS-based distributed multimedia conferencing services for Next Generation Convergent Networks is proposed. [...]

Les travaux de cette thèse s'inscrivent dans le contexte des réseaux sans fil et des réseaux d'accès par Satellite en particulier, qui facilitent l'installation d'infrastructures réseau dans les zones géographiquement reculées et faiblement peuplées. Cependant, ces derniers présentent certains inconvénients lorsqu'il s'agit de déployer des applications multimédia interactives. En effet, de telles applications requièrent un délai de bout en bout aussi faible que possible et plus généralement exigent une meilleure Qualité de Service (QdS) du système de communication que le classique Meilleur-Effort (BE) afin de fonctionner correctement. Or, les réseaux d'accès par satellite géostationnaires souffrent déjà d'un délai de propagation non négligeable d'autant plus accru que la transmission des données est assurée par des mécanismes d'allocation dynamique, par exemple dans un système DVB-S2/RCS. Dans ces travaux de thèse, nous proposons d'utiliser les informations de signalisation de session des applications multimédia basées sur le protocole de session SIP afin d'ajuster le paramétrage du système de communication selon une approche " cross-layer " qui permet alors d'améliorer de façon significative la réactivité du système. Nous avons proposé plusieurs solutions pour, d'abord réduire le temps entre la demande de communication et le démarrage effectif du transfert des flux multimédia, ensuite réduire le délai de transmission des données multimédia durant la communication (tout en utilisant de manière optimale les ressources réseau disponibles sur la voie retour), et enfin accroître le nombre de flux multimédia admissibles dans le réseau satellite tout en leur garantissant un niveau de QdS satisfaisant. Afin de faciliter l'intégration et l'implémentation des solutions proposées dans un système de communication réel, un mécanisme de communication inter-couches d'optimisation est proposé et développé. De plus, une architecture orientée web services est utilisée afin de faciliter la découverte et l'invocation des différentes niveaux de services de communication présents dans de tels réseaux d'accès. Les solutions proposées ont été évaluées dans des environnements sans fil émulés et réels

Abstract Wireless sensor networks (WSNs) consisting of battery-powered sensors are increasingly deployed for a myriad of Internet of Things applications, e.g., environmental, industrial, and healthcare monitoring. Since wireless access is typically the main contributor to battery usage, minimizing communications is crucial to prolong network lifetime and improve user experience. The objective of this thesis is to develop and analyze energy-efficient distributed compressed data acquisition techniques for WSNs. The thesis proposes four approaches to conserve sensors' energy by minimizing the amount of information each sensor has to transmit to meet given application requirements. The first part addresses a cross-layer design to minimize the sensors’ sum transmit power via joint optimization of resource allocation and multi-path routing. A distributed consensus optimization based algorithm is proposed to solve the problem. The algorithm is shown to have superior convergence compared to several baselines. The remaining parts deal with compressed sensing (CS) of sparse/compressible sources. The second part focuses on the distributed CS acquisition of spatially and temporally correlated sensor data streams. A CS algorithm based on sliding window and recursive decoding is developed. The method is shown to achieve higher reconstruction accuracy with fewer transmissions and less decoding delay and complexity compared to several baselines, and to progressively refine past estimates. The last two approaches incorporate the quantization of CS measurements and focus on lossy source coding. The third part addresses the distributed quantized CS (QCS) acquisition of correlated sparse sources. A distortion-rate optimized variable-rate QCS method is proposed. The method is shown to achieve higher distortion-rate performance than the baselines and to enable a trade-off between compression performance and encoding complexity via the pre-quantization of measurements. The fourth part investigates information-theoretic rate-distortion (RD) performance limits of single-sensor QCS. A lower bound to the best achievable compression — defined by the remote RD function (RDF) — is derived. A method to numerically approximate the remote RDF is proposed. The results compare practical QCS methods to the derived limits, and show a novel QCS method to approach the remote RDF. / Tiivistelmä Patterikäyttöisistä antureista koostuvat langattomat anturiverkot yleistyvät esineiden internetin myötä esim. ympäristö-, teollisuus-, ja terveydenhoitosovelluksissa. Koska langaton tiedonsiirto kuluttaa merkittävästi energiaa, kommunikoinnin minimointi on elintärkeää pidentämään verkon elinikää ja parantamaan käyttäjäkokemusta. Väitöskirjan tavoitteena on kehittää ja analysoida energiatehokkaita hajautettuja pakattuja datankeruumenetelmiä langattomiin anturiverkkoihin. Työssä ehdotetaan neljä lähestymistapaa, jotka säästävät anturien energiaa minimoimalla se tiedonsiirron määrä, mikä vaaditaan täyttämään sovelluksen asettamat kriteerit. Väitöskirjan ensimmäinen osa tarkastelee protokollakerrosten yhteissuunnittelua, jossa minimoidaan anturien yhteislähetysteho optimoimalla resurssiallokaatio ja monitiereititys. Ratkaisuksi ehdotetaan konsensukseen perustuva hajautettu algoritmi. Tulokset osoittavat algoritmin suppenemisominaisuuksien olevan verrokkejaan paremmat. Loppuosat keskittyvät harvojen lähteiden pakattuun havaintaan (compressed sensing, CS). Toinen osa keskittyy tila- ja aikatasossa korreloituneen anturidatan hajautettuun keräämiseen. Työssä kehitetään liukuvaan ikkunaan ja rekursiiviseen dekoodaukseen perustuva CS-algoritmi. Tulokset osoittavat menetelmän saavuttavan verrokkejaan korkeamman rekonstruktiotarkkuuden pienemmällä tiedonsiirrolla sekä dekoodausviiveellä ja -kompleksisuudella ja kykenevän asteittain parantamaan menneitä estimaatteja. Työn viimeiset osat sisällyttävät järjestelmämalliin CS-mittausten kvantisoinnin keskittyen häviölliseen lähdekoodaukseen. Kolmas osa käsittelee hajautettua korreloitujen harvojen signaalien kvantisoitua CS-havaintaa (quantized CS, QCS). Työssä ehdotetaan särön ja muuttuvan koodinopeuden välisen suhteen optimoiva QCS-menetelmä. Menetelmällä osoitetaan olevan verrokkejaan parempi pakkaustehokkuus sekä kyky painottaa suorituskyvyn ja enkooderin kompleksisuuden välillä mittausten esikvantisointia käyttäen. Neljäs osa tutkii informaatioteoreettisia, koodisuhde-särösuhteeseen perustuvia suorituskykyrajoja yhden anturin QCS-järjestelmässä. Parhaimmalle mahdolliselle pakkaustehokkuudelle johdetaan alaraja, sekä kehitetään menetelmä sen numeeriseen arviointiin. Tulokset vertaavat käytännön QCS-menetelmiä johdettuihin rajoihin, ja osoittavat ehdotetun QCS-menetelmän saavuttavan lähes optimaalinen suorituskyky.

Submitted by Eduarda Figueiredo (eduarda.ffigueiredo@ufpe.br) on 2015-03-06T13:44:05Z No. of bitstreams: 2 chaves.pdf: 2856967 bytes, checksum: 08cd733e8cb84a531adc13230e5edaaf (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-06T13:44:05Z (GMT). No. of bitstreams: 2 chaves.pdf: 2856967 bytes, checksum: 08cd733e8cb84a531adc13230e5edaaf (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2012-02-24 / CNPq e CAPES / Nesta Tese são propostas diversas estratégias para projetar redes ópticas WDM de forma otimizada. As redes são consideradas com tráfego dinâmico e penalizadas pelas penalidades da camada física. As estratégias propostas lidam com os principais elementos que afetam a relação custo desempenho em uma rede óptica: o algoritmo de roteamento e atribuição de comprimentos de onda (RWA), a colocação de regeneradores (RP), a atribuição de regeneradores (RA), o projeto da topologia física da rede (PTD) e o dimensionamento dos dispositivos ópticos (DDO) que serão instalados na rede. Esses problemas são tratados tanto de forma separada quanto de forma integrada na Tese. Para o RWA, é proposta uma metodologia para se projetar algoritmos heurísticos de roteamento que têm como objetivo o aumento no desempenho da rede e que levam em conta as penalidades da camada física. Para a solução do RP são propostos algoritmos heurísticos e metaheurísticos para o projeto de redes ópticas translúcidas, considerando simultaneamente a otimização dos custos de capital (CapEx) e operacional (OpEx) e do desempenho da rede. O problema de PTD é tratado em conjunto com o DDO também de forma mutiobjetiva, considerando a otimização simultânea do CapEx e do desempenho (probabilidade de bloqueio). Um algoritmo multiobjetivo para realização da expansão de topologia (i.e. adição de novos enlaces a uma rede já existente) também é proposto. Além disso, são resolvidos conjuntamente os problemas de PTD, RP e RWA de forma mutiobjetiva considerando a otimização simultânea de CapEx e desempenho da rede. As otimizações das soluções são feitas utilizando as seguintes estratégias metaheuristicas propostas na área de inteligência computacional: Particle Swarm Optimization (PSO) e Non-dominated Sorting Genetic Algorithm II (NSGA-II).