Teses / dissertações sobre o tema "Réseaux de communication sans"
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Albu, Roxana. "Architecture de communication pour les réseaux d'instrumentation sans fil". Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2011. http://tel.archives-ouvertes.fr/tel-00619443.
Texto completo da fonteAlbu, Roxana. "Architecture de communication pour les réseaux d’instrumentation sans fil". Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0045/document.
Texto completo da fonteResearches in the field of sensor networks show the variety and vastness of applications in which these types of systems are used. One of their main features is the large number (up to hundreds of elements) of sensors that must be distributed in different environments. Another concern consists in making routing decisions in order to reduce the energy consumption. Depending on the application requirements, ensuring synchronous network functionality is currently a challenge. The issue addressed in this thesis is to develop an architecture for smart objects using low-power antennas for structural heald monitoring. Integrating a multidisciplinary approach, this architecture includes services from the MAC layer to those of the highest level. In summary, we will develop an autonomous system ofi sensors, for acquisition and information processing, which communicate via a wireless network. The main problems are: the control of topology, the timing accuracy and the energy consumption
Kelif, Jean-Marc. "Modèles fluides de réseaux sans fil". Paris, ENST, 2008. https://pastel.hal.science/pastel-00004761.
Texto completo da fonteWang, Lusheng. "Sélection de Réseau dans les Réseaux Sans Fil Hétérogènes". Phd thesis, Télécom ParisTech, 2010. http://pastel.archives-ouvertes.fr/pastel-00517219.
Texto completo da fonteWang, Lusheng. "Sélection de réseau dans les réseaux sans fil hétérogènes". Phd thesis, Paris, ENST, 2010. https://pastel.hal.science/pastel-00517219.
Texto completo da fonteIn the present trend towards ubiquity of networks and mobility of services, we observe that network access can be provided by different types of access technologies with coverage overlapping, which composes an environment of heterogeneous wireless networks. In this environment, mobile terminals need always select the best network. In this dissertation, we make firstly a survey of existing schemes of network selection, which utilise different mathematical models. Then, we establish a simulator by matlab. In our first proposition, the problem of using mobility factors are studied. We explain that the selection of the best network becomes the selection of the best permutation when vertical handover properties are taken into account. In the end, we propose a scheme to find the best permutation. Secondly, we analyze the requirement of new subjective weighting method. We propose a new automatic method, which is based on the triggers and is capable of calculating efficiently subjective weights of various attributes, considering terminal and network factors. Finally, many other problems of network selection are analyzed and possible solutions are proposed. Based on all the above studies, we propose an integrated strategy for network selection
Ben, Abdesslem Fehmi. "Conception et prototypage d'algorithmes de communication pour réseaux sans fil". Paris 6, 2008. http://www.theses.fr/2008PA066397.
Texto completo da fonteChamp, Julien. "Communication et Localisation dans les réseaux de capteurs sans-fil". Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20133.
Texto completo da fonteRecent advancements in the fields of telecommunications and miniaturization make it possible to deploy for a reasonnable cost, autonomous communicating objects in order to collect environmental data, or to respond when a given event appears in the deployment area. Due to the emergence of these new kind of ad hoc networks, it is needed to design various new protocols, adapted to the constraints of considered objects and to the specific needs of targeted applications.During this thesis, the objective was to contribute to the field of wireless sensor networks by proposing solutions for some of the most important issues. In the first part of this document, dedicated to communication problems, we study and propose a new energy efficient geographical routing mechanism which overcomes the periodic exchange of HELLO messages, often required to determine sensors neighborhood. We also extend this method when considering the presence of location errors of sensors. Next, we have studied a strategy to enhance the lifetime of the network when periodic queries must be sent from the base station to the whole network, by adapting an efficient localized broadcast algorithm, in order to balance energy consumption between nodes. Additionally we have shown that it is not necessary to recompute the broadcast trees for each query to obtain a good lifetime.In the second part of this document, we considered the localization problem in wireless multihop networks. After a study of some of the most interesting solutions in the litterature, we propose a new family of localization methods which are well suited for wireless sensor networks, using 2-hop information and force-based algorithms. Through extensive simulations we show the scalabity of our method, and its ability to obtain accurate results, even when considering complex topologies or the presence of large measurement errors
Fawaz, Nadia. "Communications coopératives pour les réseaux ad hoc sans fil". Phd thesis, Télécom ParisTech, 2008. http://pastel.archives-ouvertes.fr/pastel-00004836.
Texto completo da fonteFawaz, Nadia. "Communications coopératives pour les réseaux ad hoc sans fil". Phd thesis, Paris, ENST, 2008. https://pastel.hal.science/pastel-00004836.
Texto completo da fonteWireless ad hoc networks received significant attention because of their defense and commercial applications. Most research on ad hoc networks focused on routing protocols. However, the theoretical and practical limits of the performance of dense ad hoc networks recently unveiled, revealed the need for alternative techniques to improve the interference-limited performance of dense ad hoc networks. In this thesis, we address the following issue: how can the link-capacity performance in wireless ad hoc networks be improved through the use of more advanced physical layer techniques? We first introduce the physical layer factors that impact the performance of dense ad hoc networks. In particular, we show how the throughput can be improved by using directive antennas, or by managing the number and position of relays. Then, we turn our attention to ad hoc networks in which nodes are empowered with cooperative capabilities. We first consider networks with a small number of nodes and propose techniques to improve spectral efficiency. The proposed cooperative strategies make more efficient use of the wireless resource by combining orthogonality-relaxation and dirty paper coding. Finally, networks with a high density of nodes are examined and cooperation is introduced through a cooperative-clustering approach. Using tools from random matrix and free probability theory, we analyze the asymptotic capacity of the system when the node density increases. This thesis shows that the link-capacity performance of dense wireless ad hoc networks can be improved as long as nodes are empowered with cooperative capabilities at the physical layer, and cooperative strategies are properly designed
Chelius, Guillaume. "Architectures et communications dans les réseaux spontanés sans-fil". Lyon, INSA, 2004. http://theses.insa-lyon.fr/publication/2004ISAL0024/these.pdf.
Texto completo da fonteThis PhD addresses several issues bound to ad hoc and sensor networks. We first define the notion of ad hoc architecture before describing our two proposals, Ana4 and Ana6. These architectures are notably used to evaluate and optimize unicast routing in wireless hybrid networks, i. E. , the rnerging of a wireless infrastructure network and ad hoc connectivity. Then we study ad hoc multicast routing. After having presented NP-completeness results for both ad hoc multicast and broadcast problems, we describe our ad hoc multicast routing protocol DMZ (Dense Multicast Zone). DMZ uses tree and mesh structures to create robust diffusion structures and rely on the notion of dense zones. Fin ally, we address the issue of energy consumption in sensor networks. Using a new analytical model, we derive upper and lower bounds for the minimum energy broadcast and covering problems
Nguyen, Huu Nghia. "Gestion de mobilité supportée par le réseau dans les réseaux sans fil hétérogènes". Paris, ENST, 2009. https://pastel.hal.science/pastel-00005406.
Texto completo da fonteIn this thesis, we focus on challenges to support Proxy Mobile IPv6 (PMIPv6) in heterogeneous wireless networks, of which the topology can be statically defined but more likely to be arbitrary and organized as spontaneous wireless mesh networks. We first propose the cluster-based architecture to scale up the network. Subsequently, we propose an extension to PMIPv6 for scalability support in large wireless networks in a cluster-based manner. We have evaluated the scalability of our framework, called Scalable Proxy Mobile IPv6 (SPMIPv6), in a wireless mesh network context. A mathematical model has been used to investigate the scalability of the framework with consideration of the wireless mesh network size, mobile node density, and average mobile speed. Furthermore, we introduce route optimization support into the SPMIPv6 framework, and then propose an enhanced IP-Layer network-based movement detection mechanism to deal with an environment employing heterogeneous radio access technologies. In order to evaluate the performance of these extensions, we implement all these propositions under Linux. We setup both virtual and real wireless mesh testbeds and run each in different scenarios to evaluate important information, such as signaling cost, handover latency, packets loss, Round Trip Time (RTT), and TCP throughput. Finally, we address the multi-homing context by proposing a virtual Stream Control Transmission Protocol (vSCTP) tunneling method, which is beneficial for both users and operators with wireless bandwidth aggregation and load balancing scenarios
Ameur, Hocine Abdelhakim. "Vers des réseaux hétérogènes sans fil efficaces en consommation énergétique". Thesis, Troyes, 2016. http://www.theses.fr/2016TROY0034.
Texto completo da fonteThe environment is undergoing a significant damage caused by the use of non-renewable energy sources. The information and communications technology sector is responsible for 2% of the global carbon footprint. Statistics show also that the energy consumed by wireless networks represents around 10% of the annual energy consumption. With the widespread of the Internet of Things, cellular networks are becoming the most used communication technology. Therefore, these networks start using heterogeneous infrastructures to address the lack of capacity.In this thesis, we focus on studying the energy saving problem within cellular networks. In particular, the energy consumed by heterogeneous cellular networks, which are known by their main importance in the future communication architectures namely, 5G networks. Heterogeneous networks (HetNets) use different types of access technologies. In addition to the conventional base stations, these networks introduce the concept of small cells which is characterized by the use of Microcells, Picocells and Femtocells. This diversity offers several advantages in terms of spectral efficiency, network coverage and capacity
La, Chi Anh. "Réplication de contenu dans les réseaux sans fil mobiles". Paris, Télécom ParisTech, 2010. http://pastel.archives-ouvertes.fr/pastel-00545009.
Texto completo da fonteThe growth of mobile devices and network-based services nowadays has raised a timely question on how to efficiently distribute the data items to mobile users. Network applications need data as an input to process and provide information to users. Consequently, data traffic exerted by mobile devices fetching content is a drainage of mobile operators’ network resources. Mobile users are now coping with the congestion at network gateways and due to the unpredictability of human mobility, mobile service providers cannot sufficiently provision infrastructures for their customers. Content replication in this context has been proved as a good solution to enhance network performance and scalability. In this thesis, we tackle the issues of content replication in heterogeneous mobile networks. Such scheme requires us to solve two basic questions: where and how many replicas should be placed in the system. We study the solution through the lenses of facility location theory and design a distributed mechanism that reduces content access latency and avoids congestion at mobile gateways. Additionally, we consider the resource constraints of mobile devices and introduce a P2P cache-and-forward mechanism for load balancing purpose. We evaluate our mechanisms against realistic human mobility models. Finally, to address rational users who may behave selfishly in replicating content, we derive a cost model and study content replication scheme using tools akin to game theory. Based on the theoretical findings, our future work is to develop the strategies to be implemented in a practical network setting
Benamrouche, Bilal. "Efficacité énergétique des architectures de communication sans fil IR-UWB pour les réseaux de capteurs sans fil". Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0023/document.
Texto completo da fonteThis Ph.D. Subject proposes the design of a new generation of wireless sensor networks (WSN) based on impulse radio ultra-wide band (IR-UWB), reconfigurable upon the application, reliable and ultra-low power. Applications like structure health monitoring of aerospace structures or portable smart sensing systems for human protection can be targeted. These industrial applications impose very demanding specifications for the wireless communication protocol (in some cases, new services are needed like: localization, clock synchronization, real-time transmission, etc) on one side, and for the circuit design, on the other side, as the ultra-low power circuits are needed. Energy efficiency is the major driver in today development of the wireless sensor networks. We chose impulse radio ultra-wideband (IR-UWB) technique for our developments. IR-UWB is a very promising technique able to respond to the wireless communication protocol constraints and to energy efficiency constraints.! The objective of this Ph.D. will be to design an ultra-low power IR-UWB transceiver. IR-UWB signal processing techniques has to be study and innovator solution has to be proposed for the implementation of the IR-UWB transceiver. The first prototype will be developed on FPGA boards (and/or USRP boards) and the final IR-UWB transceiver will be an ASIC in CMOS technology. The design of an ultra-low power consumption of the CMOS transceiver will be a major concern. Modern ultra-low power circuit techniques from the nanometrics CMOS design kits will be used. MAC layer adapted to the demands of the application and working on IR-UWB physical layer will be also studied and designed. A microprocessor integration on the chip for power management of the different parts (sensor, communication, computing, energy harvesting) of the system can also be studied. This work will be based on the previous research results obtained in our team in the case of static WSN. This work will take plac! e in the highly stimulating and competitive environment of a E! uropean project
Carsenat, David. "Contribution à l'étude de réseaux de communication sans fil : Application au LMDS". Limoges, 2003. http://aurore.unilim.fr/theses/nxfile/default/7e8e22b4-5d30-4813-8e3d-0367b844e76b/blobholder:0/2003LIMO0039.pdf.
Texto completo da fonteThis document is dedicated to the study of high speed wireless communication networks functioning in the 40 GHz frequency band. We will be mainly interested in the LMDS (Local Multipoint Distribution System) networks since this report has been written within the framework of an RNRT project (Réseau national de recherche en télécommunications) called ERASME. This project aims at studying the performances of an LMDS system based on the DVB (Digital Video Broadcasting) standard. The MAC layer (Medium Access Control) used in the ERASME platform is studied in detail witn an application software named OPNET which allows the development of a tool for dimensioning wireless networks. Because of the DVB standard performances submitted to multimedia applications like the videconference, this document presents and studies the IEEE 802. 16 standard which proves to be much more flexible than DVB standard
Randriatsiferana, Rivo Sitraka A. "Optimisation énergétique des protocoles de communication des réseaux de capteurs sans fil". Thesis, La Réunion, 2014. http://www.theses.fr/2014LARE0019/document.
Texto completo da fonteTo increase the lifetime of wireless sensor networks, a solution is to improve the energy efficiency of the communication's protocol. The grouping of nodes in the wireless sensor network clustering is one of the best methods. This thesis proposes several improvements by changing the settings of the reference protocol LEACH. To improve the energy distribution of "cluster-heads", we propose two centralized clustering protocols LEACH and k-optimized version k-LEACH-VAR. A distributed algorithm, called e-LEACH, is proposed to reduce the periodic exchange of information between the nodes and the base station during the election of "cluster-heads". Moreover, the concept of energy balance is introduced in metric election to avoid overloading nodes. Then we presented a decentralized version of k-LEACH, which in addition to the previous objectives, integrates the overall energy consumption of the network. This protocol, called k-LEACH-C2D, also aims to promote the scalability of the network. To reinforce the autonomy and networks, both routing protocols "multi-hop" probability, denoted CB-RSM and FRSM build elementary paths between the "cluster-heads" and elected the base station. The protocol, CB-RSM, forms a hierarchy of "cluster-heads" during the training phase clusters, with an emphasis on self-scheduling and self-organization between "cluster-heads" to make the networks more scalable. These protocols are based on the basic idea that the nodes have the highest residual energy and lower variance of energy consumption become "cluster-head". We see the central role of consumption of the node in our proposals. This point will be the last part of this thesis. We propose a methodology to characterize experimentally the consumption of a node. The objectives are to better understand the consumption for different sequences of the node status. In the end, we propose a global model of the consumption of the node
Le, Ngoc Khuyen. "Homologie simpliciale appliquée aux réseaux sans fil". Electronic Thesis or Diss., Paris, ENST, 2016. http://www.theses.fr/2016ENST0039.
Texto completo da fonteSimplicial homology is a useful tool to access important information about the topology of wireless networks such as : coverage and connectivity. In this thesis, we model the wireless network as a random deployment of cells. Firstly, we introduce an algorithm to construct the Cech complex, which describes exactly the topology of the network. Then, the Cech complex is used in further applications. The first application is to save transmission power for wireless networks. This application not only maximizes the coverage of the network but also minimizes its transmission power. At the same time, the coverage and the transmission power are optimized. The second application is to balance the traffic load in wireless networks. This application controls the transmission power of each cell in the network, always under the coverage constraint. With the controlled transmission power, the users are redirected to connect to the lower traffic load cells. Consequentially, the balanced traffic load is obtained for the network
Combes, Richard. "Mécanismes auto-organisants dans les réseaux sans fil". Paris 6, 2013. http://www.theses.fr/2013PA066028.
Texto completo da fonteIn this thesis we study the design, modeling and performance evaluation of mechanisms which can manage wireless networks autonomously (self-organizing mechanisms). We recall the technological context, and the required mathematical tools are introduced concisely: queuing theory, point processes, information theory, stochastic approximation, Markov decisions processes and reinforcement learning. In the first part, we study opportunistic scheduling. We are interested in their performance evaluation and their use to perform coverage-capacity optimization. Physical layer phenomena such as channel fading, interference, receiver structure and practical modulation and coding schemes are taken into account. In the second part, an algorithm for automatic load balancing is presented. The dynamical arrivals and departures of users are taken into account. For stationary traffic, the convergence of the mechanism to the optimal configuration is shown using stochastic approximation theorems. For non-stationary traffic, numerical experiments suggest that the mechanism is able to adapt itself to daily traffic patterns. In the third part, we study relay-enhanced networks. Based on a queuing analysis, a simple formula for network dimensioning is given. It is valid for the most general traffic model (stationary ergodic input). The load balancing mechanism is extended to relay-enhanced networks. A dynamical load balancing algorithm based on reinforcement is studied
Kamel, Sarah. "Sécurité pour les réseaux sans fil". Electronic Thesis or Diss., Paris, ENST, 2017. http://www.theses.fr/2017ENST0011.
Texto completo da fonteToday, there is a real need to strengthen the communication security to anticipate the development of quantum computing and the eventual attacks arising from it. This work explores two complementary techniques that provide confidentiality to data transmitted over wireless networks. In the first part, we focus on lattice-based public-key cryptography, which is one of the most promising techniques for the post-quantum cryptography systems. In particular, we focus on the Goldreich-Goldwasser-Halevi (GGH) cryptosystem, for which we propose a new scheme using GLD lattices. In the second part of this work, we study the security of multi-user cache-aided wiretap broadcast channels (BCs) against an external eavesdropper under two secrecy constraints: individual secrecy constraint and joint secrecy constraint. We compute upper and lower bounds on secure capacity-memory tradeoff considering different cache distributions. To obtain the lower bound, we propose different coding schemes that combine wiretap coding, superposition coding and piggyback coding. We prove that allocation of the cache memory to the weaker receivers is the most beneficial cache distribution scenario
Darties, Benoît. "Problèmes algorithmiques et de complexité dans les réseaux sans fil". Montpellier 2, 2007. http://www.theses.fr/2007MON20204.
Texto completo da fonteThe last couple of years have seen the advent of wireless networks, doped by their ease of deployment and their use in multiple fields: personal WiFi networks, mobile telephony, ad hoc networks, sensors networks,. . . The subject of this thesis relates to the study of algorithmic problems directly inspired by operating constraints which can be found in such networks. This manuscrit is divided into three parts. The first part of our work is devoted to the study of the problem of broadcasting a single source node message to all the other nodes of a network. This problem is tackled in various communication models. All the considered model suppose range-fixed omnidirectional transmissions subject to interference phenomena. It results from that, that any given node is unable to retrieve simultaneously two incoming transmissions. We study the complexity of this problem and propose some strategies in order to solve it. In a second part, We study another algorithmic problem in the same communication model, whose object is to satisfy a given set of communication requests. Our work consists in etablishing the complexity of this problem, and studying the impact of various factors on this complexity. The last part considers the problem of designing survivable radio networks. The objective is to ensure a distribution of bandwidth from source nodes to customers nodes, by minimizing the cost of the deployed infrastructure. Communications are made via directional antennas, and are not subjects to interferences. The difficulty of the problem lies in the satisfaction of deployment constraints (limited number of antennas per node, robustness against failures of nodes,. . . ). We study the complexity of this problem, and propose exact and approximated resolution methods to solve reasonable size instances
Audeoud, Henry-Joseph. "Routage efficace et garanti dans les réseaux de capteurs sans fil". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAM055.
Texto completo da fonteThe wireless sensor networks that we work with in this thesis are a set of devices connected to eachother by low-rate and low-power technologies. Their role is to produce measures on the physical environ-ment around them (meteorological and climate condition tracking, monitoring of industrial installations,control of distribution grids, topographical surveillance. . . ). These measures must then be collected out ofthe network. Since the sensors have short range radios, transmissions are multi-hop, the sensors close tothe destination relaying the information transmitted by those which are further away from it. Because ofthe movement of the nodes themselves or of objects in their environment interfering with wireless commu-nications, the exact topology of the network is subject to change. In addition, the battery-powered sensorsare limited in energy and therefore in transmission abilities. The power-saving techniques applied to turnoff the radio most of the time impose synchronization constraints.To route information through the network, the routing protocol establishes routes, so that the sensorscan relay information from and to the network border router through reliable links leading to the destina-tion through short paths. Due to sensor limitations, the routing must be energy efficient, i.e. the overloadof the radio transmissions involved by the routing algorithm itself must be as lightweight as possible. Itmust also be able to restore connectivity on a network topology change without creating routing loops thatnegatively impact the quality of service and the energy reserves of the nodes.This document describes a routing protocol that meets these objectives. It is capable of creating a self-healing collection tree that extracts information out of the network, as well as from the routes to distributecommand messages or acknowledgment to the nodes. It also validates the data path of each packet toensure that they never enter a routing loop. The protocol is run in simulations and also on real platformexperiments, showing the effectiveness of the proposed mechanisms.In order to improve its ability to choose the best available links, I also propose the use of a new esti-mation of their quality. It is based on two complementary measurements: a long-term measurement ofthe ambient noise level on the radio channel, and a measurement of the power of the signal received fromthe transmitter. These two measurements provide an estimate of the signal-to-noise ratio, and thereby theexpected reception rate. This estimate is both accurate, quick to obtain, and adapted to the constraints ofsensors and networks we are talking about
Ramassamy, Cédric. "Analyse des protocoles des réseaux de capteurs sans-fil". Thesis, Antilles-Guyane, 2012. http://www.theses.fr/2012AGUY0586/document.
Texto completo da fonteWireless sensor networks is one of the hotest research topic in the last few years. This technology can be applied for different fields such as environment, industry, trading, medicine, military etc. Wireless sensor networks are hard to conceive because they require a lot of energy and because each of its component may have an influence on the lifetime of the whole system. What we suggest is a tool allowing to choose the correct and optimal parameters for the reliability of the applications.In this thesis, we focused on two major problems : firstly, a classification of the parameters for a tool allowing to make decisions about the configuration of a wireless sensors network, and secondly, a tool testing the compliance of the system with a real environment. The document is divided into two parts : the first part states the different protocols that exist, and the second part describes our contributions to those topics.In the first contribution, we analyzed how influential the radio cover and the network topology are on the network performances. Then, we deduced from the study of the loss rate and of the level of energy, the reliability of the application. Next, we suggested a study leading to a classification for our decision making tool. For this classification, we studied various parameters related to the MAC layer, the Physical layer, the network layer, the application layer the number of nodes involved in the network.In the second contribution, we adopted a pragmatic approach so we could test the conformity of a wireless sensors network in a real environment. In order to test its conformity in a real environment, we suggested a structured test execution on a real wireless sensor network. This task has been suggested in order to check the conformance level of the network while it was working
Nivor, Frédéric. "Architecture de Communication pour les Applications Multimédia Interactives dans les Réseaux Sans Fil". Phd thesis, Université Paul Sabatier - Toulouse III, 2009. http://tel.archives-ouvertes.fr/tel-01067146.
Texto completo da fonteChen, Zheng. "Communication centrée sur les utilisateurs et les contenus dans les réseaux sans fil". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC092/document.
Texto completo da fonteThis thesis focuses on several emerging technologies towards future wireless networks with envisaged improvement on the area spectral efficiency and energy efficiency. The related research involves two major directions, including deviceto- device (D2D) communication underlaid cellular networks and proactive caching at network edge. The first part of this thesis starts with introducing D2D underlaid cellular network model and distributed access control methods for D2D users that reuse licensed cellular uplink spectrum. We aim at optimize the throughput of D2D network in the following two scenarios: 1) assuming always backlogged cellular users with coverage probability constraint, 2) assuming bursty packet arrivals at the cellular user, whose average delay must be kept below a certain threshold. The second part of this thesis focuses on proactive caching methods at network edge, including at small base stations (SBSs) and user devices. First, we study and compare the performance of probabilistic content placement in different types of wireless caching networks and with different optimization objectives. Second, we propose a cooperative caching and transmission strategy in a cluster-centric small cell networks (SCNs), which exploits the combined gain of cache-level cooperation and CoMP technique. Using spatial models from stochastic geometry, we build the connection between PHY transmission diversity and the content diversity in local caches
Alghamdi, Bandar. "Etude des méthodes d'ordonnancement sur les réseaux de capteurs sans fil". Thesis, Reims, 2015. http://www.theses.fr/2015REIMS010/document.
Texto completo da fonteThe Wireless Body Area Network (WBAN) is the most critical field when considering Wireless Sensor Networks (WSN). It must be a self-organizing network architecture, meaning that it should be able to efficiently manage all network architecture requirements. The WBAN usually contains at least two or more body sensors. Each body sensor sends packets to or receives packets from the Personal Area Network Coordinator (PANC). The PANC is responsible for scheduling its child nodes' tasks. Scheduling tasks in the WBAN requires a dynamic and an adaptive process in order to handle cases of emergency that can occur with a given patient. To improve the most important parameters of a WBAN, such as quality link, response time, throughput, the duty-cycle, and packet delivery, we propose three scheduling processes: the semi-dynamic, dynamic, and priority-based dynamic scheduling approaches.In this thesis, we propose three task scheduling techniques, Semi-Dynamic Scheduling (SDS), Efficient Dynamic Scheduling (EDS) and High Priority Scheduling (HPS) approaches. Moreover, a comprehensive study has been performed for the WBAN platforms by classifying and evaluating them. We also investigate the mobility model for the WBANs by designing an architecture that describe this model. In addition, we detail a diagnosis procedure by using classification methods in order to solve very sensitive epidemic diseases. Then, our proposals have been validated using two techniques to check out the feasibility of our proposals. These techniques are simulation scenarios using the well-known network simulator OPNET and real implementations over TelosB motes under the TinyOS system
Kamel, Sarah. "Sécurité pour les réseaux sans fil". Thesis, Paris, ENST, 2017. http://www.theses.fr/2017ENST0011/document.
Texto completo da fonteToday, there is a real need to strengthen the communication security to anticipate the development of quantum computing and the eventual attacks arising from it. This work explores two complementary techniques that provide confidentiality to data transmitted over wireless networks. In the first part, we focus on lattice-based public-key cryptography, which is one of the most promising techniques for the post-quantum cryptography systems. In particular, we focus on the Goldreich-Goldwasser-Halevi (GGH) cryptosystem, for which we propose a new scheme using GLD lattices. In the second part of this work, we study the security of multi-user cache-aided wiretap broadcast channels (BCs) against an external eavesdropper under two secrecy constraints: individual secrecy constraint and joint secrecy constraint. We compute upper and lower bounds on secure capacity-memory tradeoff considering different cache distributions. To obtain the lower bound, we propose different coding schemes that combine wiretap coding, superposition coding and piggyback coding. We prove that allocation of the cache memory to the weaker receivers is the most beneficial cache distribution scenario
Le, Ngoc Khuyen. "Homologie simpliciale appliquée aux réseaux sans fil". Thesis, Paris, ENST, 2016. http://www.theses.fr/2016ENST0039/document.
Texto completo da fonteSimplicial homology is a useful tool to access important information about the topology of wireless networks such as : coverage and connectivity. In this thesis, we model the wireless network as a random deployment of cells. Firstly, we introduce an algorithm to construct the Cech complex, which describes exactly the topology of the network. Then, the Cech complex is used in further applications. The first application is to save transmission power for wireless networks. This application not only maximizes the coverage of the network but also minimizes its transmission power. At the same time, the coverage and the transmission power are optimized. The second application is to balance the traffic load in wireless networks. This application controls the transmission power of each cell in the network, always under the coverage constraint. With the controlled transmission power, the users are redirected to connect to the lower traffic load cells. Consequentially, the balanced traffic load is obtained for the network
Galice, Samuel. "Modèle dynamique de sécurité pour réseaux spontanés". Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0102/these.pdf.
Texto completo da fonteNowadays, communicating objects are omnipresent in our daily life. The multiplication of wireless communication standards allows these heterogeneous devices to rapidly interconnect themselves. However, many obstacles prevent a connection at will. In particular, the absence of an easily realizable and socially acceptable model of security is an important constraint in their use. In order to circumvent these problems, a trust framework must be developed as long as spontaneous interactions occur between devices in an environment without a trusting third party. The trust establishment and management framework we present here is inspired directly from results obtained in analysis of human relations. In our model, trust is considered as a pseudo-transitive relation between the different entities. The trust levels are evaluated from cryptographically data stored in a history. For security reasons, these data are ensured to be not transferable to an unauthorized third party. Numerical simulations show that the model can easily be instanced into large scale wireless networks. The free parameters of our model are set by numerical modeling in order to optimize their usage. A detailed implementation is also presented
Laouiti, Mohamed Anis. "Unicast et Multicast dans les réseaux ad hoc sans fil". Versailles-St Quentin en Yvelines, 2002. http://www.theses.fr/2002VERS018V.
Texto completo da fonteKhan, Farooq. "Accès multiple et allocation des ressources pour réseaux multimédia sans fil". Versailles-St Quentin en Yvelines, 1997. http://www.theses.fr/1997VERS0003.
Texto completo da fonteNepomuceno, Napoleao. "Optimisation dans des réseaux backhaul sans fil". Phd thesis, Université de Nice Sophia-Antipolis, 2010. http://tel.archives-ouvertes.fr/tel-00593412.
Texto completo da fonteJacquot, Aurélien. "Supervision de réseaux d'objets intelligents communicants sans fil". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2010. http://tel.archives-ouvertes.fr/tel-00719350.
Texto completo da fonteAgba, Landaabalo. "Elaboration de logiciel d'aide au déploiement de réseaux sans fil millimétriques". Limoges, 2004. http://aurore.unilim.fr/theses/nxfile/default/4e4f4064-e256-4878-aa69-3c7844b0f2ae/blobholder:0/2004LIMO0020.pdf.
Texto completo da fonteThe deployment of wireless networks in an outdoor environment is complex because of the numerous parameters which must be taken into account. In this context, this report presents a relevant planning software for networks deployment which integrates these multiple parameters in millimetric frequency band. Rays Tracing method is used in association with antennae characteristics and propagation channel parameters. The coverage simulations on real cases are realized using GIS (Geographic Information system) databases coupled with aerial view photographs and GPS (Global Positioning System) measurements. The precision of the simulations was successfully confirmed by experimental measurements. This software allowed to propose some coverage improvements of a 40 GHz LMDS (Local Multipoint Distribution Services) system using new antennae topologies, reflectors and repeaters
Malik, Salman. "Evaluation et Optimisation des Réseaux Sans Fil Denses". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00719083.
Texto completo da fonteMunir, Muhammad Farukh. "Optimisation inter-couche de réseaux de capteurs et capteurs-actionneurs sans fil". Paris, ENST, 2009. http://www.theses.fr/2009ENST0039.
Texto completo da fonteJacquot, Aurélien. "Supervision de réseaux d'objets intelligents communicants sans fil". Phd thesis, Clermont-Ferrand 2, 2010. http://www.theses.fr/2010CLF22019.
Texto completo da fonteBouallegue, Mehdi. "Protocoles de communication et optimisation de l'énergie dans les réseaux de capteurs sans fil". Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1011/document.
Texto completo da fonteWireless sensor networks (WSNs) are composed of a large number of sensor nodes that are typicallybattery-powered and designed to operate for a long period. Application areas are many and varied, such as the environmental field, medical and military.The major advantage of this device is a large-scale deployment without any maintenance. The sensors do not need to achieve an established infrastructure to transmit vital data to the study of the environment. It is also necessary to ensure good quality service, because without son sensor networks must incorporate mechanisms that allow users to extend the life of the entire network, as each node is supplied by a limited power source and generally irreplaceable. Therefore, it is necessary to optimize the power consumption at all levels of design of this type of network. Accordingly, minimization of power consumption is one of the most important design factors in sensor networks.The aim of this thesis is study the different existing routing techniques in a context without multi-hop son to get better performance. We carry our study of the most popular routing protocols to offer in a second part a new routing protocol for optimizing energy consumption without son sensor networks, keeping an optimal quality of service
Maghmoumi, Chadi. "Mise en oeuvre des approches de clusterisation dans les réseaux de communication sans fil". Thesis, Mulhouse, 2010. http://www.theses.fr/2010MULH3083.
Texto completo da fonteThe proposed clustering approache divides the network into clusters based on affinity relationships between nodes and two types of keys which are generated by a clusterhead. The first one is shared by a clusterhead and its local members and the second one is shared by the clusterhead and its parent cluster. The proposed algorithm is adaptive according to the limitation of the mobile nodes battery power and to the dynamic network topology changes.The performance evaluation and communication overhead analysis of the proposed algorithm are presented using simulation
Abid, Mohamed Amine. "Systèmes de localisation en temps réel basés sur les réseaux de communication sans fil". Thèse, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/8820.
Texto completo da fonteVarela, santana Thomas. "Intérêt de la communication direct entre équipements mobiles dans les réseaux radio sans fil". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC083/document.
Texto completo da fonteThis thesis studies D2D communication in realistic and challenging scenarios for future wireless systems. In particular, the thesis focuses on how may D2D communication help other technologies to enhance their performance. The first wireless scenario is the one of multicasting, used for example in video streaming or common alert message transmission for police, firefighters or ambulances. The second wireless scenario is the critical one of URLLC expected to be used to avoid cars crashes in the upcoming V2X context, and also when connecting machines together in environments like connected hospitals, airports, factories (industry 4.0), and last but not least in e-health context in order to enhance medical tele-surgery. The last wireless scenario is the one of UE group localization in the context of massive IoT, where devices are interacting with each other and are mostly confined in local groups, needing local services. In the multicast channel scenario, where a transmitter wishes to convey a common message to many receivers, it is known that the multicast rate decrease as the number of UEs increases. This vanishing behavior changes drastically when enabling the receivers to cooperate with each other via D2D. Indeed, the multicast rate increases with high probability when the number of receivers increases. This chapter also analyzes the outage rate of the proposed scheme in the same setting. Extensions regarding firstly resource utilization and secondly considering the use of HARQ are also analyzed. Next chapter addresses one of the major challenges for future networks, named URLLC. Specifically, the chapter studies the problem of HARQ with delayed feedback, where the transmitter is informed after some delay on whether or not his transmission was successful. The goal is to minimize the expected number of retransmissions subject to a reliability constraint within a delay budget. This problem is studied at two levels: (i) a single transmitter faced with a stochastic i.i.d. noisy environment and (ii) a group of transmitters whom shares a collision channel. Then the chapter that follows provides a cooperative UE mapping method that is highly accurate. Four different channel models are studied in this chapter: LOS and NLOS for indoor and outdoor environments. The results show significant improvement compared to already existing methods. Identifying the dense local areas in real time and informing the network allows the Base Station (BS) to increase the capacity through highly directive beams, and therefore, avoids the deployment cost of new infrastructure
Dos, Santos Jessye. "Réseaux de capteurs et vie privée". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAM035/document.
Texto completo da fontePrivacy notion is frequently linked with cyber attack examples by media and scientific researches. In 2012, the hacking of 12 millions Apple user identifiers demonstrates that connected objects represent leaks exploited by hackers to access to user personal data. In this thesis, we will extend the privacy notion to the objects. To do this, we will show that in wireless sensor networks where communications are carried out from machine-to-machine, the knowledge of the static addresses of the devices within the network discloses information allowing deduction about elements of context and environment.Nowadays, the wireless communication standards provide security mechanisms whatever the communication protocols used including the low power ones designed to run on constrained environment. However, the frame header that comprises necessary information for routing and for the proper functioning of the network is always sent in clear text. Collecting and gathering these metadata by eavesdropping is dangerous for the environments and applications based on these networks.The work carried out in this thesis aims to explore how simple passive attacks on meshed networks based on IEEE 802.15.4 used to collect and exploit metadata allow to infer critical information about the network, the environment where the network is deployed and the behavior of users. Two kinds of solutions to hide the node addresses are studied. The first one provides anonymity for the devices. In the second kind of solutions, pseudonyms are used by nodes enabling the capability to audit the traffic within the network.To evaluate the characteristics and the performances of the solutions, a simulator has been used to reproduce the behavior of a meshed wireless sensor network embedding Contiki OS. This simulator allows to compare the performances of MT6D the most promising solution of our state of the art with that of a reference network do not mask the metadata. With this analyze, we can highlight some drawbacks and more especially the control frames overhead needed for the routing. We give the necessary specifications to deploy the most optimal solution for the embedded devices.Thus we propose Ephemeral that allows hiding device addresses provided in the sent frames by using pseudonyms without overhead on the control frames. After deployment in the simulation environment to evaluate expected theoretical performances, Ephemeral has been tested in real environment. The network is made up of twenty IEEE 802.15.4 sensor nodes deployed on a building. The results show that Ephemeral is an efficient low power and bandwidth-saving solution to hide device identifiers used in wireless communications
Djouama, Amir. "Contrôle de topologie ambiant dans les réseaux sans fil". Versailles-St Quentin en Yvelines, 2010. http://www.theses.fr/2010VERS0019.
Texto completo da fonteWith the evolution of the wireless communication systems and the increasing control of complexity in the material, it becomes possible to conceive network architectures dynamicaly controlable and equiped with a capacity of ambient decision. Within the framework of the thesis we propose to study and optimize the control of a network made up of mobile nodes wich communicate without infrastructure. Two levels of control will be considered, one being at the level of the lower layers while the other adresses the aspects relating to the higher layers. The dynamic control on the level of the lower layers relates to two aspects : 1- The adaptation of the topology of the network and the routing to the requests coming from the lower layers. 2- Optimization inter-layer (cross-layer) in order to use as well as possible the resources of the network and in particular the radio. The dynamic control on the level of the higher layer relates to the discovery and the adaptation of the application to the services of communications offered by the lower layers. In a second step, we study the admission control. We propose to study the local parameters of each node, wich are interesting for the continuity of sessions. An approach for admission control is given which interact lifetime of nodes and their point of attachment
Ghorbel, Asma. "Limites Fondamentales De Stockage Dans Les Réseaux Sans Fil". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC031/document.
Texto completo da fonteCaching, i.e. storing popular contents at caches available at end users, has received a significant interest as a technique to reduce the peak traffic in wireless networks. In particular, coded caching proposed by Maddah-Ali and Niesen has been considered as a promising approach to achieve a constant delivery time as the dimension grows. However, several limitations prevent its applications in practical wireless systems. Throughout the thesis, we address the limitations of classical coded caching in various wireless channels. Then, we propose novel delivery schemes that exploit opportunistically the underlying wireless channels while preserving partly the promising gain of coded caching. In the first part of the thesis, we study the achievable rate region of the erasure broadcast channel with cache and state feedback. We propose an achievable schemeand prove its optimality for special cases of interest. These results are generalized to the multi-antenna broadcast channel with state feedback. In the second part, we study the content delivery over asymmetric block-fading broadcast channels, where the channel quality varies across users and time. Assuming that user requests arrive dynamically, we design an online scheme based on queuing structure and prove that it maximizes the alpha-fair utility among all schemes restricted to decentralized placement. In the last part, we study opportunistic scheduling over the asymmetric fading broadcast channel and aim to design a scalable delivery scheme while ensuring fairness among users. We propose a simple threshold-based scheduling policy of linear complexity that requires only a one-bit feedback from each user
Mitton, Nathalie. "Auto-organisation des réseaux sans fil multi-sauts à grande échelle". Lyon, INSA, 2006. http://theses.insa-lyon.fr/publication/2006ISAL0023/these.pdf.
Texto completo da fonteWireless networks are mobile networks that do not rely over any infrastructure. Network devices have limited capacities as energy, bandwidth, memory size, etc. Current routing protocols do not allow the use of such networks over large scale. To overcome this drawback, I propose a hierarchical routing scheme for such networks. It is composed of a clustering protocol that organizes the network into groups of nodes (clusters), of a localization protocol to locate a single node in the network and of a hybrid routing protocol. Cluster structure can also be used to perform an efficient message broadcasting in the whole network. Algorithms have been studied by simulation, by comparative analysis with existing solutions and, when it was possible by a theoretical way stochastic geometry. The proposed approaches are local, distributed and use tools such the DHT and interval routing
Lertsinsrubtavee, Adisorn. "Sélection et transfert de spectre adaptatifs dans les réseaux de radio cognitive". Paris 6, 2013. http://www.theses.fr/2013PA066300.
Texto completo da fonteCognitive radio is proposed as a promising solution for the next generation of wireless communication networks. Cognitive radio users are required to perform spectrum handoff from a wireless channel to another in order to cope with the dynamic spectrum environment imposed by licensed users. Spectrum handoff can cause transmission interruptions leading to the degradation of services. We study and develop efficient spectrum management strategies that aim to provide diverse service requirements for cognitive radio users. First, we propose novel spectrum handoff and selection strategies in order to satisfy a delay requirement. In particular, we estimate the delay of arrival packets based on the prior packets in the queue and compare it to a maximum delay bound. Then, we use the expected delays to estimate a delay violation ratio that guides the spectrum handoff and selection decisions. Our strategies reduce the number of spectrum handoff significantly compared to existing approaches while the delay requirement is guaranteed. Second, we consider the rate requirement by investigating the interaction between spectrum handoff and spectrum sharing through an optimization framework. The results provide useful insights and guidelines for designing efficient spectrum sharing heuristics that take into account spectrum handoff and selection strategies. Finally, we develop a heuristic for spectrum sharing that includes novel static and dynamic spectrum sharing algorithms based essentially on a rate compensation approach and adapted best fit algorithms. Our heuristic reduces the number of handoffs significantly while the achieved rate is fulfilling compared to the optimal
Khan, Safdar Abbas. "Localisation et détection de fautes dans les réseaux de capteurs sans fil". Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST1028/document.
Texto completo da fonteIn this thesis three themes related to wireless sensor networks (WSNs) are covered. The first one concerns the power loss in a node signal due to voltage droop in the battery of the node. In the first part of the thesis a method is proposed to compensate for the apparent increase in the calculated distance between the related nodes due to decrease in the energy of the signal sending node battery. A function is proposed whose arguments are the apparently observed RSS and the current voltage of the emitter node battery. The return of the function is the corrected RSS that corresponds to the actual distance amongst the connected nodes. Hence increasing the efficiency of the RSS based localization methods in WSNs. In the second part of the thesis a position estimation method for localization of nodes in a WSN is proposed. In the proposed localization algorithm anchor nodes are used as landmark points. The localization method proposed here does not require any constraint on the placement of the anchors; rather any three randomly chosen nodes can serve as anchors. A heuristic approach is used to find the relative topology with the help of distance matrix. The purpose of the distance matrix is to indicate whether or not a pair of nodes has a connection between them and in case of connectivity it gives the estimated distance between the nodes. By using the information of connectivity between the nodes and their respective distances the topology of the nodes is calculated. This method is heuristic because it uses the point solution from the intersection of two circles instead of conventional triangulation method, where a system of three quadratic equations in two variables is used whereby the computational complexity of the position estimation method is increased. When two connected nodes have another node in common, then by using the information of distances between these interconnected nodes, two possible positions are calculated for the third node. The presence or absence of a connection between the third node and a fourth node helps in finding the accurate possibility out of the two. This process is iterated till all the nodes have been relatively placed. Once the relative topology has been calculated, we need to find the exact symmetry, orientation, and position of this topology in the plane. It is at this moment the knowledge of three nodes positions comes into action. From the relative topology we know the temporary coordinates of the nodes. By having a comparison of certain characteristics between the temporary coordinates and the exact coordinates; first the symmetry of relative topology is obtained that would correspond to the original topology. In other words it tells whether or not the relative topology is a mirror image of the original topology. Some geometrical operators are used to correct the topology position and orientation. Thus, all the nodes in the WSN are localized using exactly three anchors. The last part of the thesis focuses on the detection of faults in a WSN. There is always a possibility that a sensor of a node is not giving accurate measurements all of the time. Therefore, it is necessary to find if a node has developed a faulty sensor. With the precise information about the sensor health, one can determine the extent of reliance on its sensor measurement. To equip a node with multiple sensors is not an economical solution. Thus the sensor measurements of a node are modeled with the help of the fuzzy inference system (FIS). For each node, both recurrent and non-recurrent systems are used to model its sensor measurement. An FIS for a particular node is trained with input variables as the actual sensor measurements of the neighbor nodes and with output variable as the real sensor measurements of that node. The difference between the FIS approximated value and the actual measurement of the sensor is used as an indication for whether or not to declare a node as faulty
Bizagwira, Honoré. "Réseaux de capteurs sans fil étendu robuste exploitant des liens atypiques". Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22770/document.
Texto completo da fonteThis thesis takes place in the context of environmental monitoring applications requiring regular measurements of biological or geophysical characteristics. These applications include for instance the measuring of the spread of pollutants in rivers, monitoring of the development of bacteria in bathing waters, etc. Wireless Sensor Networks (WSNs) provide cost-effective and reliable solutions to allow the automation of such data gathering. The good functioning of these networks depends on the quality of the radio transmissions, which is particularly true in environments where the conditions are not suitable for the propagation of radio waves and where the links may therefore be intermittent. The objective of this work is to propose an effective protocol solution under such conditions, in the particular case of a sensor network deployed on the water surface. The thesis begins with a description of the methodology, mechanisms and a platform for exploring the quality of a radio link displayed at the water surface. We present different measures that have been carried out. The protocol solutions we propose take into account the evolutionary nature of the topology due to the instability of the radio links in order to improve the efficiency of the data gathering and to reduce the energy consumption of the nodes. Our approach is based on the periodic reconstruction of the topology, the communication between nodes by appointments defined by transmission windows, the use of the multi-channel to drain the data and the adaptation of the transmission window size as a function of local traffic. All these propositions are validated by prototyping and simulation using NS-3. The results show that our solution is capable of collecting data in a dynamic topology while reducing both gathering time and energy consumption
Helluy-Lafont, Étienne. "Sécurité et détection d'intrusion dans les réseaux sans fil". Thesis, Lille, 2021. http://www.theses.fr/2021LILUI017.
Texto completo da fonteThis thesis focuses on the security of wireless communications, as used on devices such as mobile phones, laptops, or connected devices that make up the Internet of Things. Nowadays, wireless communications are carried out using integrated components (modem), which can themselves be the target of attacks. Indeed, these modems contain Closed Source software, that are poorly audited, and may have flaws. During this thesis, we pursued two complementary approaches that aim to address the problem of wireless modems security. The first is to detect attacks in order to mitigate the risks posed by vulnerabilities ; the second is to identify and correct these vulnerabilities in order to eliminate the risks. Wireless modems pose particular constraints for Intrusion Detection Systems (IDS). In fact, if the modem is at risk of being compromised, the operating system (OS) cannot trust the information it is sending back : the modem is unreliable. This makes it difficult to detect wireless attacks from the OS, as it has no reliable source of information on whichto base detection. In this context, it is preferable to perform intrusion detection at the network level, by directly capturing the signals exchanged wirelessly. However, it is not always easy to recover the signals of interest. Today’s equipment supports a multitude of different communication standards. This heterogeneity represents a challenge for capture solutions. In addition, some protocols do not lend themselves well to passive capture of their exchanges, and are sometimes even specifically designed to prevent it. Finally, data is usually encrypted, which is an additional obstacle for intrusion detection systems. Software Defined Radio (SDR) can partly meet the challenges posed by this diversity. They consist of a hardware part, but above all of software, which can be adapted to receive signals of any standard - within the limits of the material. In this thesis, we present a SDR specifically designed to allow the capture and analysis of a given frequency band, in order to identify and label the signals present. It is an elementary building block for building wireless intrusion detection systems. In addition, software radio processes signals in terms of their physical representation. This allows them to collect additional information, which would not have been accessible if a conventional modem had been used to capture the signals. In this thesis, we describe methods to identify the model of a Bluetooth device by analysing the physical representation of the packets it transmits. In the second part of this thesis, we analysed the firmware of several Bluetooth modems, in order to identify vulnerabilities that would allow remote control. This allowed us to discover several exploitable vulnerabilities in widely used modems. Finally, we developeda free and open-source Bluetooth modem that allows interaction with real-world modems to facilitate research and development on their security
Darties, Benoit. "Problèmes algorithmiques et de complexité dans les réseaux sans fil". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2007. http://tel.archives-ouvertes.fr/tel-00270118.
Texto completo da fonteLa première partie de nos travaux s'intéresse à l'étude du problème de la diffusion d'un message émis depuis un noeud source unique vers l'ensemble des noeuds participant au réseau. Ce problème est abordé dans plusieurs modèles de communication, qui supposent tous des émissions omnidirectionnelles à portée fixée et l'existence de phénomènes d'interférences. Il en résulte l'incapacité pour un noeud donné de garantir la réception correcte de deux transmissions voisines simultanées. Nous étudions la complexité de ce problème et proposons des stratégies de résolution exactes ou avec garantie de performance.
Dans une seconde partie, l'un des modèles de communication précédemment introduits sert de support à l'étude d'un autre problème algorithmique, dont l'objet est la satisfaction de requêtes de communications. Les travaux menés sur ce problème visent à établir sa complexité ainsi que les facteurs dont elle dépend.
La dernière partie nous amène au problème de conception de réseaux sans fil. L'objectif est d'assurer une distribution de flux depuis des noeuds sources vers des noeuds clients, en minimisant le coût de l'infrastructure déployée. Les communications établies ici à l'aide d'antennes directionnelles ne sont pas sujettes aux phénomènes d'interférences. La difficulté du problème réside dans la satisfaction de contraintes de déploiement (nombre d'antennes limitées par noeud, résistance aux pannes, ...). Nous étudions la complexité de ce problème, et proposons plusieurs méthodes de résolution exactes et approchées pour des instances de taille raisonnable.
Afif, Mériem. "Interaction des mécanismes RLC/MAC et de SCTP dans les réseaux B3G". Paris, ENST, 2007. http://www.theses.fr/2007ENST0028.
Texto completo da fonteCurrent tendency in wireless communication networks (EDGE/EGPRS, WLAN, AdHoc…) is focused on the study of cross-layer interaction mechanisms. This thesis concerns the study of interaction mechanisms between transport and link layers, and their applications to transmission control parameters (as congestion and flow control parameters). After a detailed description of the basic SCTP functionalities and its additional extensions defined to adapt SCTP to wireless contexts, we investigate the influence of multi streaming when used to transport web pages in HTTP 1. 0 transactions over SCTP in EDGE environment. SCTP does not suffer from the head of line blocking issue inherent to TCP due to its multistreaming functionality. The results show that SCTP performs better than TCP when several streams are activated at SCTP level. The second contribution relates to intra and inter radio access technologies data handover performance improvement. We propose a new SCTP control chunk, QoS_Measurement_Chunk. It allows the transmission of radio QoS measurements from the mobile to its SCTP peer. These information can be used by the SCTP layer to adapt the transmission rate to current radio transmission conditions (particularly useful in handover/reselection situation). The combined use of Qos_Measurement_Chunk with multihoming feature provide a data handover (EDGE/EDGE, EDGE/WLAN) with performance improvement. The obtained simulation results are compared to the standard SCTP presenting so better performance in terms of data throughput over the access network. The third contribution of this thesis is on cross-layer modeling (transport : SCTP/link Layer EDGE)