Immobilization of Inorganic Nanoparticles on Responsive Polymer Brushes

Exploitation of well defined responsive polymer brushes for direct and controlled immobilization of metal/semiconductor nanoparticles on macroscopic surfaces has been demonstrated. The employed approach offers the possibility of the organization of a variety of inorganic nanoparticles by irreversible bonding and homogenous distribution on an underlying substrate. The immobilization process has been realized by chemical grafting of a variety of polymer brushes on a suitable substrate followed by the attachment of pre-/in-situ formed nanoparticles exploiting the chemical/physical interactions between surface functionalities of nanoparticles and polymer chain segments. A number of polymer brushes including poly (acrylic acid), polystyrene, poly (2-vinyl pyridine) and poly (N-isopropyl acrylamide) brushes have been prepared on silicon substrate by the “grafting to” approach. A variety of inorganic nanoparticles such as quantum dots (CdTe) noble metals (gold and silver) and magnetic (Fe3O4) were immobilized on macroscopic surfaces to impart them photo luminescent, catalytic or magnetic properties. In addition, responsiveness of grafted polymer brushes in terms of variation in thickness (due to changes in chain conformation) as a function of external stimuli such as solvent and pH allowed to use the resulting polymer brush-nanoparticles nanoassemblies in the fabrication of nanosensors. The design of fabricated nanosensors is based on the modulation in the interparticle distance of immobilized nanoparticles due to swelling/deswelling of underlined polymer brushes in response to some external trigger

Game theoretical analysis of rate adaptation protocols conciliating QoS and QoE

International audienceThe recent increase in the use of wireless networks for video transmission has led to the increase in the use of rate-adaptive protocols to maximize the resource utilization and increase the efficiency in the transmission. However, a number of these protocols lead to interactions among the users that are subjective in nature and affect the overall performance. In this paper, we present an in-depth analysis of interplay between the wireless network dynamics and video transmission dynamics in the light of subjective perceptions of the end users in their interactions. We investigate video exchange applications in which two users interact repeatedly over a wireless relay channel. Each user is driven by three conflicting objectives: maximizing the Quality of Service (QoS) and Quality of Experience (QoE) of the received video, while minimizing the transmission cost. Non-cooperative repeated games model precisely interactions among users with independent agendas. We show that adaptive video exchange is impossible if the duration of the interaction is determined. However, if the users interact indefinitely, they achieve cooperation via exchange of video streams. Our simulations evidence the tradeoff between users’ QoS and QoE of their received video. The expected duration of the interaction plays a role and draws the region of solution trade-offs. We propose further means of shaping this region using Pareto optimality and user-fairness arguments. This work proposes a concrete game theoretical framework that allows the optimal use of traditional protocols by taking into account thesubjective interactions that occur in practical scenarios

Contributions on networking techniques for wireless relay channels

En los últimos años, el relaying ha surgido como una poderosa técnica para mejorar la cobertura y el rendimiento de las redes inalámbricas. En consecuencia, la creciente demanda de servicios basados en redes inalámbricas con relays, ha conducido al desarrollo de técnicas de networking nuevas y eficientes. Estas técnicas pueden ser utilizadas en diferentes capas de la pila de protocolos y pueden ser optimizadas para cumplir diversos objetivos, como la maximización del rendimiento, mejora de cobertura, etc. en el marco de las redes existentes. En esta tesis se presenta una serie de contribuciones para las técnicas de networking, utilizando una variedad de herramientas a fin de maximizar el rendimiento de la red y satisfacer las demandas de los usuarios. Para hacer contribuciones efectivas y concretas, hemos seleccionado problemas exigentes en varios aspectos de las técnicas avanzadas de networking en redes inalámbricas y presentamos soluciones hábiles a éstos. En particular, hacemos uso de diferentes herramientas como network coding, técnicas de transmisión cognitiva y teoría de juegos, con el fin de diseñar soluciones para las redes inalámbricas modernas con relays. Las principales técnicas de networking, para diferentes capas de la pila de protocolos, presentadas en esta tesis son las siguientes. En primer lugar, a nivel de capa física, maximizamos el rendimiento de la red mediante la herramienta de network coding en la capa física (PNC) basada en el método compute and forward (CF) en redes con relays. Se sabe que las tasas máximas alcanzables en la transmisión basada en CF están limitadas debido a las aproximaciones de los canales en el relay. Proponemos el Integer Forcing Precoder (IFP), para superar esta limitación. Con la ayuda del IFP, demostramos una posible implementación de la prometedora técnica de CF, que allanaría el camino para un diseño avanzado del precodificador para maximizar el rendimiento de la red. En segundo lugar, en la capa de enlace de la red, maximizamos el rendimiento con el uso de dos herramientas diferentes: (a) network coding junto con una optimización cross-layer condicionada a la calidad de experiencia (QoE), (b) técnicas de transmisión cognitiva. En (a), utilizamos el network coding en la capa de enlace, en coherencia con la optimización cross-layer y demostramos la existencia de compromisos importantes entre rendimiento y QoE alcanzable. Por otra parte, proponemos utilizar factores realistas como la ubicación de los usuarios finales en la red de relays para optimizar el servicio obtenido en presencia de tales compromisos. En (b), utilizamos las técnicas de transmisión cognitiva para analizar la mejora en el rendimiento de una red inalámbrica particular, el sistema de satélites duales (DSS). Además, presentamos un análisis taxonómico exhaustivo de las diferentes técnicas cognitivas en DSS. Con la ayuda de este trabajo, proponemos posibles diseños para las técnicas "inteligentes" de networking, las cuales constituyen una plataforma para maximizar el rendimiento de futuras redes inalámbricas con relays. En tercer lugar, en la capa de transporte-aplicación, maximizamos no sólo el rendimiento, si no también una utilidad conjunta compuesta de rendimiento, QoE y coste del servicio, utilizando herramientas de la teoría de juegos. Consideramos una aplicación de video transmitida por una red inalámbrica en la que las usuarios que compiten tratan de maximizar sus utilidades. Modelamos y predecimos los puntos de equilibrio alcanzados usando repetidas formulaciones del juego, teniendo en cuenta factores reales como la tolerancia de los usuarios y el criterio óptimo de Pareto. Con la ayuda de este trabajo, se demuestra el potencial del uso de técnicas repetidas de teoría de juegos en redes inalámbricas, prometiendo así mejorar el rendimiento del sistema existente de manera categórica. En general, esta tesis presenta propuestas prácticas y efectivas junto con un análisis holístico para diferentes aspectos en el desarrollo de técnicas modernas de networking para redes inalámbricas con relays.In the recent years, relaying has emerged as a powerful technique to improve the coverage and throughput of wireless networks. Consequently, the growing demands of the wireless relay networks based services has led to the development of novel and efficient networking techniques. These techniques can be used at different layers of the protocol stack and can be optimized to meet different objectives like throughput maximization, improving coverage etc. within existent networking framework. This thesis presents a series of contributions towards the networking techniques using a variety of tools in order to maximize the throughput of the network and satisfy the user demands. To make effective and concrete contributions, we have selected challenging problems in various aspects of advanced wireless networking techniques and presented neat solutions to these problems. In particular, we make use of the different tools like network coding, cognitive transmission techniques and game theory in order to design networking solutions for modern wireless relay networks. The main contributions of this thesis towards networking techniques at different layers of the protocol stack are as follows. Firstly, at the physical layer, we maximize the throughput of the network using the tool of physical layer network coding (PNC) based on compute and forward (CF) in relay networks. It is known that the maximum achievable rates in CF-based transmission are limited due to the channel approximations at the relay. We propose the integer forcing precoder (IFP), which bypasses this maximum rate achievability limitation. With the help of IFP, we demonstrate a possible implementation of the promising scheme of CF thereby paving the way for an advanced precoder design to maximize network throughput. Secondly, at the link-network layer, we maximize throughput with the use of two different tools: (a) network coding along with Quality of Experience (QoE) driven cross-layer optimization and (b) cognitive transmission techniques. For (a), we use network coding at link layer in coherence with cross-layer optimization and prove the existence of crucial trade-offs between throughput and achievable QoE. Moreover, it is proposed to use the realistic factors such as positioning of the end users in the relay network to optimize the service obtained in presence of such trade-offs. For (b), we use the cognitive transmission techniques to analyze the improvement in throughput of a particular wireless network, namely Dual Satellite systems (DSS). Moreover, an exhaustive taxonomic analysis of the different cognitive techniques in DSS is presented. With the help of this work, the possible designs for 'intelligent' networking techniques are proposed, which form a platform for maximizing the throughput performance of future wireless, relay networks. Thirdly, at the transport-application layer, we maximize not only the throughput but a joint utility comprised of throughput, QoE and cost of service, with the use of game theoretical tools. We consider a video application relayed over a wireless network and competing users trying to maximize their utilities. We model and predict the equilibriums achieved using repeated game formulations taking into account the realistic factors such as tolerance of the users and pareto optimality. With the help of this work, the potential of use of repeated game theoretical tools in wireless networks is proved which also promises to improve the existing system performance categorically. Overall, this thesis presents effective and practical propositions along with holistic analysis towards different aspects of development of modern networking techniques for wireless relay networks

Immobilization of Inorganic Nanoparticles on Responsive Polymer Brushes

Exploitation of well defined responsive polymer brushes for direct and controlled immobilization of metal/semiconductor nanoparticles on macroscopic surfaces has been demonstrated. The employed approach offers the possibility of the organization of a variety of inorganic nanoparticles by irreversible bonding and homogenous distribution on an underlying substrate. The immobilization process has been realized by chemical grafting of a variety of polymer brushes on a suitable substrate followed by the attachment of pre-/in-situ formed nanoparticles exploiting the chemical/physical interactions between surface functionalities of nanoparticles and polymer chain segments. A number of polymer brushes including poly (acrylic acid), polystyrene, poly (2-vinyl pyridine) and poly (N-isopropyl acrylamide) brushes have been prepared on silicon substrate by the “grafting to” approach. A variety of inorganic nanoparticles such as quantum dots (CdTe) noble metals (gold and silver) and magnetic (Fe3O4) were immobilized on macroscopic surfaces to impart them photo luminescent, catalytic or magnetic properties. In addition, responsiveness of grafted polymer brushes in terms of variation in thickness (due to changes in chain conformation) as a function of external stimuli such as solvent and pH allowed to use the resulting polymer brush-nanoparticles nanoassemblies in the fabrication of nanosensors. The design of fabricated nanosensors is based on the modulation in the interparticle distance of immobilized nanoparticles due to swelling/deswelling of underlined polymer brushes in response to some external trigger

Physical Layer Network Coding Based on Integer Forcing Precoded Compute and Forward

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Game Theoretical Analysis of the Tradeoff Between QoE and QoS Over Satellite Channels

International audienceIn this work, a game-theoretic analysis of a video exchange application in which two users exchange their video streams over a satellite channel using Quality of Experience (QoE) driven rate adaptation is studied. In such an interaction, users aim at maximizing the Quality of Service (QoS) and QoE of their received video while minimizing their individual cost incurred by their video transmission, which is modeled as a repeated game. Given the payoff model of the users, it is shown that adaptive video exchange between selfish autonomous nodes for a deterministic time will not be sustained. However, if video is exchanged over an unlimited or indeterminate period, thenodes have an incentive to cooperate and exchange video streams with QoE-driven rate adaptation based on the trust they buildamong themselves. Our simulation results show that a tradeoff exists between the QoS and the QoE of the perceived video.Furthermore, it is shown that the expected interaction length has a high impact on such tradeoff