This thesis introduces LIFT, a combination of a cluster-based approach with a cross-layer scheme in order to discover services in MANET. In this proposal, High Capability Devices (HCD) are differentiated from Limited Capability Devices (LCD). HCD are set up as the cluster leaders in each cluster so as to perform most of the service discovery activities. Thus, LIFT manages local traffic instead of global traffic. Consequently, messages, energy, computing processes, and bandwidth were reduced due to the optimum usage of network resources. In order to know if LIFT achieves its goal to minimize resources, we have compared LIFT with another well-known solution (AODV-SD) in terms of control message overhead, energy consumption, PDR, throughput, hop count average, NRL, end-to-end delay, and service acquisition time. After carrying out many trials and simulations, LIFT improved previous results in the area. / La tesis presenta a LIFT, una solución para descubrir servicios en MANET que combina un enfoque basado en cluster con un esquema cross-layer. En esta propuesta se diferencian los dispositivos de capacidades superiores (HCD) de los dispositivos de capacidades limitadas (LCD). Los HCD se establecen como líderes en cada cluster para ejecutar la mayoría de las actividades de descubrimiento de servicios. De esta forma, LIFT maneja tráfico local en vez de tráfico global. Por tanto, se reduce el consumo de mensajes, energía y cómputo al hacer uso óptimo de los recursos de la red. Para saber si LIFT logra el objetivo de minimizar recursos, lo hemos comparado contra otra solución (AODV-SD) en aspectos como sobrecarga de paquetes de control, consumo de energía, PDR, throughput, promedio de saltos, NRL, retardo extremo a extremo y tiempo de adquisición de servicios. Después de muchas pruebas y simulaciones, LIFT mejora resultados anteriores en este campo

Advancements in video coding, compact media display, and communication devices, particularly in emerging broadband wireless access networks, have created many foreseeable and exciting applications of video broadcast/multicast over the wireless meidum. For efficient and robust wireless video broadcast/multicast under fading, this thesis presents and examines a novel cross-layer framework that exploits the interplay between applying protections on a successively refinable video source and transmitting through a layered broadcast/multicast channel. The framework is realistically achieved and evaluated by using multiple description coding (MDC) on a scalable video source and using superposition coding (SPC) for layered broadcast/multicast transmissions. An analytical model using the total received/recovered video bitstreams from each coded wireless broadcast/multicast signal is developed, which serves as a metric of video quality for the system analysis and optimization. An efficient methodology has demonstrated that optimal power allocations and modulation selections can be practically determined to improve the broadcast/multicast video quality. From the information-theoretical perspective, a general closed-form formula is derived for the end-to-end distortion analysis of the proposed framework, which is applicable to any (n, k) protection code applied on a successive refinable source with a Gaussian distribution over layered Gaussian broadcast channels. The results reveal the scenarios for the proposed framework to lead to a lower distortion than a legacy system without any protection. By analyzing the characteristics of the closed-form formula, an efficient O(n log n) algorithm is developed to determine optimal k values in the (n, k) protection codes that minimize the distortion under the framework. Finally, a cross-layer design of logical SPC modulation is introduced to achieve layered broadcast/multicast for scalable video. It serves as an alternative for practically implementing the proposed framework of coded wireless video broadcast/multicast, if the hardware-based SPC component is not available in a wireless system. In summary, the thesis presents comprehensive analyses, simulations, and experiments to understand, investigate, and justify the effectiveness of the proposed cross-layer framework of coded wireless video broadcast/multicast. More importantly, this thesis contributes to the advancement in the related fields of communication engineering and information theory by introducing a new design dimension in terms of protection. This is unique when compared to previously-reported layered approaches that are often manipulating conventional parameters alone such as power and modulation scheme. The impact of this dimension was unapparent in the past, but is now proven as an effective means to enable high-quality, efficient, and robust wireless video broadcast/multicast for promising media applications.

Advancements in video coding, compact media display, and communication devices, particularly in emerging broadband wireless access networks, have created many foreseeable and exciting applications of video broadcast/multicast over the wireless meidum. For efficient and robust wireless video broadcast/multicast under fading, this thesis presents and examines a novel cross-layer framework that exploits the interplay between applying protections on a successively refinable video source and transmitting through a layered broadcast/multicast channel. The framework is realistically achieved and evaluated by using multiple description coding (MDC) on a scalable video source and using superposition coding (SPC) for layered broadcast/multicast transmissions. An analytical model using the total received/recovered video bitstreams from each coded wireless broadcast/multicast signal is developed, which serves as a metric of video quality for the system analysis and optimization. An efficient methodology has demonstrated that optimal power allocations and modulation selections can be practically determined to improve the broadcast/multicast video quality. From the information-theoretical perspective, a general closed-form formula is derived for the end-to-end distortion analysis of the proposed framework, which is applicable to any (n, k) protection code applied on a successive refinable source with a Gaussian distribution over layered Gaussian broadcast channels. The results reveal the scenarios for the proposed framework to lead to a lower distortion than a legacy system without any protection. By analyzing the characteristics of the closed-form formula, an efficient O(n log n) algorithm is developed to determine optimal k values in the (n, k) protection codes that minimize the distortion under the framework. Finally, a cross-layer design of logical SPC modulation is introduced to achieve layered broadcast/multicast for scalable video. It serves as an alternative for practically implementing the proposed framework of coded wireless video broadcast/multicast, if the hardware-based SPC component is not available in a wireless system. In summary, the thesis presents comprehensive analyses, simulations, and experiments to understand, investigate, and justify the effectiveness of the proposed cross-layer framework of coded wireless video broadcast/multicast. More importantly, this thesis contributes to the advancement in the related fields of communication engineering and information theory by introducing a new design dimension in terms of protection. This is unique when compared to previously-reported layered approaches that are often manipulating conventional parameters alone such as power and modulation scheme. The impact of this dimension was unapparent in the past, but is now proven as an effective means to enable high-quality, efficient, and robust wireless video broadcast/multicast for promising media applications.

Wireless Sensor and Actor Networks (WSANs) are distributed systems of heterogeneous devices, referred to as sensors and actors, which sense, control, and interact with the physical environment. Sensors are low-cost, low-power, multi-functional devices that communicate untethered in short distances. Actors are resource-rich devices that collect and process sensor data and consequently perform actions on the environment. This thesis is concerned with coordination and communication problems in WSANs, in datacentric and multimedia application scenarios. First, communication and coordination problems are jointly addressed in a unifying framework for the case of static actors. A sensor-actor coordination model is proposed, based on an event-driven partitioning paradigm. Sensors are partitioned into different sets and each set is associated with a different actor. Data delivery trees are created to optimally react to the event and timely deliver event data with minimum energy expenditure. The optimal partitioning strategy is determined bymathematical programming, and a distributed solution is also proposed. Furthermore, the actor-actor coordination problem is formulated as an optimal task assignment problem, and a distributed solution of the problem based on an analogy with a one-shot auction is presented. Application scenarios for WSANs with mobile actors are then studied. A location management scheme is introduced to handle the mobility of actors with minimal energy consumption for resource-constrained sensors. The proposed scheme, which is the first localization scheme specifically designed for WSANs, is shown to consistently reduce the energy consumption with respect to existing localization services for ad hoc and sensor networks. An optimal energy-aware forwarding rule is then derived for sensor-actor communication in fast varying Rayleigh channels. The proposed scheme allows controlling the delay of the data-delivery process based on power control, and reacts to network congestion by diverting traffic from congested to lightly-loaded actors. The mobility of actors is coordinated to optimally accomplish application-specific tasks, based on a nonlinear optimization model that accounts for location and capabilities of heterogeneous actors. The research challenges for delivery of multimedia traffic in wireless sensor and actor networks are then outlined. Finally, a cross-layer communication architecture based on Ultra Wide Band communications is described, whose design objective is to reliably and flexibly deliver QoS to multimedia applications in WSANs, by carefully leveraging and controlling interactions among layers according to application requirements. Performance evaluation shows how the proposed solution achieves the performance objectives of wireless sensor and actor networks.

Overlay networks have recently gained popularity as a viable alternative to overcome functionality limitations of the Internet (e.g., lack of QoS, multicast routing). They offer enhanced functionality to end-users by forming an independent and customizable virtual network over the native network. Typically, the routing at the overlay layer operates independent of that at the underlying native layer. There are several potential problems with this approach because overlay networks are selfish entities that are chiefly concerned with achieving the routing objective of their own users. This leads to complex cross-layer interactions between the native and overlay layers, and often tends to degrade the achieved performance for both layers. As overlay applications proliferate and the amount of selfish overlay traffic surges, there is a clear need for understanding the complex interactions and for strategies to manage them appropriately. Our work addresses these issues in the context of "service overlay networks", which represent virtual networks formed of persistent nodes that collaborate to offer improved services to actual end-systems. Typically, service overlays alter the route between the overlay nodes in a dynamic manner in order to satisfy a selfish objective. The objective of this thesis is to improve the stability and performance of overlay routing in this multi-layer environment. <br><br> We investigate the common problems of functionality overlap, lack of cross-layer awareness, mismatch or misalignment in routing objectives and the contention for native resources between the two layers. These problems often lead to deterioration in performance for the end-users. This thesis presents an analysis of the cross-layer interaction during fault recovery, inter-domain policy enforcement and traffic engineering in the multi-layer context. Based on our characterization of the interaction, we propose effective strategies that improve overall routing performance, with minimal side-effects on other traffic. These strategies typically 1) increase the layer-awareness (awareness of information about the other layer) at each layer, 2) introduce better control over routing dynamics and 3) offer improved overlay node placement options. Our results demonstrate how applying these strategies lead to better management of the cross-layer interaction, which in turn leads to improved routing performance for end-users.

Quality-of-service (QoS) guarantees have become critically important for the transmission of real-time multimedia traffic in next generation mobile wireless networks. The aim of this dissertation is to investigate the cross-layer design for support of delay bound QoS guarantees over fading channels. Providing diverse QoS guarantees presents a challenge due to the time-varying fading nature of wireless channels. Existing physical layer modelling is inadequate in supporting real time QoS metrics such as delay, hence adaptive techniques need to be extended to the upper-protocol layers. The first objective of this dissertation is to introduce a cross-layer design framework which investigates the impact of the physical layer on the data link delay bound QoS performance. At the physical layer, adaptive modulation and coding (AMC) is utilized for transmission over block fading channels. At the data link layer, the effective capacity approach is used to model the delay bound QoS performance subject to physical layer variations. The effects of varying physical layer parameters, such as average signal-to-noise ratio (SNR), the fading parameter for the kagami- model, and target packet-error rate (PER), on the analytical delay bound performance are investigated and then validated by the simulation of a queuing system. Due to the cross-layer design framework, the system’s throughput has a significant impact on bounded delay at the data link layer. The switching levels of the conventional AMC scheme used in the first objective were fixed, subject to a target PER. However, fixed switching levels results in the system’s throughput limiting the delay bound performance. The second objective of this dissertation is to optimize the switching levels of the AMC scheme employed at the physical layer, by maximizing the average throughput, while maintaining the target PER constraint. The analytical and simulated results show that by optimizing the switching levels, a superior delay bound performance is achieved, when compared to the deterministic switching levels of the conventional AMC scheme used in the first objective. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

Redes sem fio devem prover qualidade de serviço para aplicações de voz, video e dados. Um padrão definido para oferecer qualidade de serviço nessas redes é o documento IEEE 802.16. Com o objetivo de melhorar a qualidade de transmissão, este padrão utiliza dois principais mecanismos físicos: (i) Orthogonal Frequency Division Multiple Access como interface física e (ii) a possibilidade de ajustar a robustez da transmissão em relação as imperfeições físicas que podem comprometer a transmissão. Além disso, o padrão define um conjunto de componentes na estação base, tal como alocadores, escalonadores e controles de admissões que devem ser modelados para prover uma arquitetura que garanta qualidade de serviço. Entretanto, o padrão não define nem os algoritmos de cada componente, nem a integração entre estes componentes. Investigações objetivando prover qualidade de serviço tem sido propostas no contexto de redes IEEE 802.16. A literatura sobre redes IEEE 802.16 móveis mostra que as atuais pesquisas estão focadas em soluções específicas para cada componente, ou em soluções com integrações parciais. O foco destas soluções é prover a melhor alternativa para problemas individuais para um componente particular. Entretanto, em todos os estudos realizadas nesta tese, não encontrou-se nenhuma pesquisa endereçando propostas sobre a qualidade de serviço global considerando a diversidade dos requisitos de tráfegos das aplicações e as condições de propagação do canal de rádio frequência. Neste contexto, essa tese propõe uma nova arquitetura para garantir qualidade de serviço em uma estão base que deve ser modelada usando uma infraestrutura entre camada para adaptar-se aos requisitos dinâmicos do tráfego, bem como as condições do canal de rádio frequência. O objetivo é integrar os componentes definidos pelo padrão com os mecanismos físicos. Outro objetivo é analisar a arquitetura proposta, através de uma metodologia de avaliação que é baseada segundo a especificação do sistema de avaliação do fórum Worldwide Interoperability for Microwave Access. Assim, a análise da nova arquitetura adaptativa entre camadas é realizada e os resultados mostram a eficiência na alocação dos dados, bem como o mínimo atraso e jitter gerado nas aplicações de tempo real. / Wireless networks must provide quality of service to voice, video and data applications. A standard defined to offer quality of service in these networks is the IEEE 802.16 document. In order to improve the quality of transmission, this standard uses two main physical mechanisms: (i) Orthogonal Frequency Division Multiple Access as physical interface and (ii) the possibility of adjusting the transmission robustness to face the physical impairments that may compromise the transmission. Moreover, the standard defines a set of components in the base station, such as allocators, schedulers, and connection admission controllers that must be modeled to provide an architecture that guarantees quality of service. However, the standard does not define either the algorithm running inside each one of the components nor the integration among them. Investigations aiming to provide quality of service have been proposed in the context of IEEE 802.16 networks. The literature on mobile IEEE 802.16 networks shows that the current research is focused on specific solutions for each component or in solutions with partial integration. The focus of those solutions is to provide the best alternative for individual problems of a particular component. However, to the best of our knowledge, no research addressing the overall quality of service architecture considering both the diversity of applications traffic requirements and the propagation conditions of the radio frequency channel has been proposed so far. In this context, this thesis proposes a new architecture to guarantee quality of service in the base station that must be modeled using a cross-layer infrastructure able to adapt to the dynamics of traffic requirements as well as to the radio frequency channel conditions. The aim is to integrate the components defined by the standard with the physical mechanisms. Another objective is to evaluate the proposed architecture, through an evaluation methodology that is defined following the specification of the system evaluation of the Worldwide Interoperability for Microwave Access forum. Therefore, the analysis on the new cross-layer adaptive architecture is performed and the results show efficient data allocation as well as a minimal delay and jitter for real-time applications.

La demande accrue de services en temps rel, comme la vidéo streaming, justifie le besoin d'études qui visent à optimiser le délai de transmission de données. En plus du délai de transmission au niveau physique, les délais nécessaires à l'accès à la ressource et à la récupération de données venant des couches basses peuvent avoir un impact important sur les performances et ne doivent pas être négligés. Aussi, des études cross-layer doivent être menées pour minimiser le délai de transmission de l'information. Comprendre l'impact des mécanismes des couches basses sur les performances de bout-en-bout permet un meilleur dimensionnement du réseau, une adaptation du trafic transmis, ou l'introduction de service à faible priorité. Dans cette thèse, nous avons mesuré l'impact des mécanismes des couches liaison et réseau sur les performances de divers protocols de congestion de la couche transport.Dans le contexte des liens 4G par satellite, nous proposons un ensemble d'outils, Trace Manager Tool (TMT) et Cross Layer InFormation Tool (CLIFT), pour simuler de manière réaliste l'ensemble de la couche OSI dans le simulateur de réseau NS-2. Nous avons montré que, pour l'ensemble des variantes de TCP considérées, quand le débit au niveau transport est proche de la capacité de canal, utiliser ARQ au niveau liaison est optimal. Dans le cas où le taux d'erreur au niveau de la couche physique est plus élevé, H-ARQ permet d'obtenir un meilleur débit au niveau transport.Les dernières spécifications concernant l'accès au lien satellite DVB-RCS2 présentent deux méthodes d'accès (aléatoire et dédié) qui peuvent être implémentées pour permettre aux utilisateurs des services proposés par DVB d'aller sur Internet ou de transmettre des données. Nous avons développé un module pour NS-2, Physical Channel Access (PCA), qui modèle l'accès au canal pour chacune de ces méthodes afin de comparer leur impact sur les performances de bout-en-bout. Nous avons mesuré que les méthodes d'accès dédié permettent un débit plus important et les méthodes d'accès aléatoire une transmission rapide des flots courts. Nous avons donc proposé de mixer ces méthodes d'accès, en fonction de l'évolution dynamique de la charge du réseau et de la taille du flot de données transmis.Finalement, nous avons étudié s'il était possible d'exploiter les données de la gateway du satellite pour introduire un trafic à priorité basse. Nous avons montré qu'il était possible avec Low Ewtra Delay Background Transport (LEDBAT) comme protocole de la couche transport d'introduire un trafic en tâche de fond. Cependant, en fonction de la variation de la charge du réseau, paramétrer correctement des paramètres internes à ce protocole sont nécessaires. / Network providers offer services in line with users’ requests, even though the challengesintroduced by their mobility and the download of large content are crucial. Mobile videostreaming applications are delay sensitive and the increasing demand for this service legitimateextensive studies evaluating transmission delays. On top of physical transmissiondelays, accessing a resource or recovering data from lower layers should not be neglected.Indeed, recovery schemes or channel access strategies variously introduce end-to-end delays.This document argues that those cross-layer effects should be explored to minimizethe transmission delays and optimize the use of network resources. Also, understandingthe impacts of low layers protocols on the end-to-end transmission will enable betterdimensioning of the network and adapt the traffic carried on.In the context of satellite 4G links, we measure the impact of link layer retransmissionschemes on the performance of various transport layer protocols. We develop Trace ManagerTool (TMT) and Cross Layer InFormation Tool (CLIFT) to lead realistic cross layersimulations in NS-2. We show that, for all target TCP variants, when the throughput ofthe transport protocol is close to the channel capacity, using the ARQ mechanism is mostbeneficial for TCP performance improvement. In conditions where the physical channelerror rate is high, Hybrid-ARQ results in better performance.In the last specifications for DVB-RCS2, two access schemes (random and dedicated)are presented and can be implemented to manage the way home users access to the satellitelink for Web browsing or data transmission. We developed Physical Channel Access (PCA)that models in NS-2 the behaviour of those link layer level access methods. We measurethat, even though dedicated access methods can transmit more information data, randomaccess methods enable a faster transmission of short flows. Based on these results, wepropose to mix random and dedicated access methods depending on the dynamic load ofthe network and the sequence number of the TCP segments.As a potential exploitation of cross layer information, we explore the feasibility to introducelow priority traffic on long delay path. The rationale is to grab the unused 4G satellitelinks’ capacity to carry non-commercial traffic. We show that this is achievable with LEDBAT.However, depending on the fluctuation of the load, performance improvements couldbe obtained by properly setting the target value.

Redes sem fio devem prover qualidade de serviço para aplicações de voz, video e dados. Um padrão definido para oferecer qualidade de serviço nessas redes é o documento IEEE 802.16. Com o objetivo de melhorar a qualidade de transmissão, este padrão utiliza dois principais mecanismos físicos: (i) Orthogonal Frequency Division Multiple Access como interface física e (ii) a possibilidade de ajustar a robustez da transmissão em relação as imperfeições físicas que podem comprometer a transmissão. Além disso, o padrão define um conjunto de componentes na estação base, tal como alocadores, escalonadores e controles de admissões que devem ser modelados para prover uma arquitetura que garanta qualidade de serviço. Entretanto, o padrão não define nem os algoritmos de cada componente, nem a integração entre estes componentes. Investigações objetivando prover qualidade de serviço tem sido propostas no contexto de redes IEEE 802.16. A literatura sobre redes IEEE 802.16 móveis mostra que as atuais pesquisas estão focadas em soluções específicas para cada componente, ou em soluções com integrações parciais. O foco destas soluções é prover a melhor alternativa para problemas individuais para um componente particular. Entretanto, em todos os estudos realizadas nesta tese, não encontrou-se nenhuma pesquisa endereçando propostas sobre a qualidade de serviço global considerando a diversidade dos requisitos de tráfegos das aplicações e as condições de propagação do canal de rádio frequência. Neste contexto, essa tese propõe uma nova arquitetura para garantir qualidade de serviço em uma estão base que deve ser modelada usando uma infraestrutura entre camada para adaptar-se aos requisitos dinâmicos do tráfego, bem como as condições do canal de rádio frequência. O objetivo é integrar os componentes definidos pelo padrão com os mecanismos físicos. Outro objetivo é analisar a arquitetura proposta, através de uma metodologia de avaliação que é baseada segundo a especificação do sistema de avaliação do fórum Worldwide Interoperability for Microwave Access. Assim, a análise da nova arquitetura adaptativa entre camadas é realizada e os resultados mostram a eficiência na alocação dos dados, bem como o mínimo atraso e jitter gerado nas aplicações de tempo real. / Wireless networks must provide quality of service to voice, video and data applications. A standard defined to offer quality of service in these networks is the IEEE 802.16 document. In order to improve the quality of transmission, this standard uses two main physical mechanisms: (i) Orthogonal Frequency Division Multiple Access as physical interface and (ii) the possibility of adjusting the transmission robustness to face the physical impairments that may compromise the transmission. Moreover, the standard defines a set of components in the base station, such as allocators, schedulers, and connection admission controllers that must be modeled to provide an architecture that guarantees quality of service. However, the standard does not define either the algorithm running inside each one of the components nor the integration among them. Investigations aiming to provide quality of service have been proposed in the context of IEEE 802.16 networks. The literature on mobile IEEE 802.16 networks shows that the current research is focused on specific solutions for each component or in solutions with partial integration. The focus of those solutions is to provide the best alternative for individual problems of a particular component. However, to the best of our knowledge, no research addressing the overall quality of service architecture considering both the diversity of applications traffic requirements and the propagation conditions of the radio frequency channel has been proposed so far. In this context, this thesis proposes a new architecture to guarantee quality of service in the base station that must be modeled using a cross-layer infrastructure able to adapt to the dynamics of traffic requirements as well as to the radio frequency channel conditions. The aim is to integrate the components defined by the standard with the physical mechanisms. Another objective is to evaluate the proposed architecture, through an evaluation methodology that is defined following the specification of the system evaluation of the Worldwide Interoperability for Microwave Access forum. Therefore, the analysis on the new cross-layer adaptive architecture is performed and the results show efficient data allocation as well as a minimal delay and jitter for real-time applications.

In this thesis, we present a detailed analysis of hybrid point-to-multipoint free space optical (FSO)/radio frequency (RF) wireless system. Hybrid FSO/RF sys- tems have emerged as a promising solution for high data rate wireless transmission. FSO technology can be used effectively in multiuser scenarios to support Point-to- Multi-Point (P2MP) networks. In this P2MP network, FSO links are used for data transmission from a central location to multiple users. When more than one FSO link fail, the central node uses a common backup RF link to transmit a frame to a remote node using an equal priority protocol. An equal priority protocol means that the remote nodes have the same priorities in being assigned the RF link. We assume two traffic classes, a high-priority and low-priority classes. The base station reserves two transmit buffers of each user for the downlink transmission. Considering the downlink traffic from the base station to a tagged remote node, we study several performance metrics. We develop a cross-layer Markov chain model to study the throughput from central node to a remote node as well as the performance of the resulting system. / Graduate