Spelling suggestions: "subject:"multihop"" "subject:"multiihop""
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HMC-MAC : un protocole MAC hybride et multi-canal pour les réseaux de capteurs sans fil / HMC-MAC : hybrid multi-channel MAC protocol for wireless sensor networksDiab, Rana 15 June 2015 (has links)
L'utilisation des canaux multiples améliore significativement les performances globales des réseaux de capteurs sans fil (RCSF) en permettant des transmissions parallèles sur plusieurs canaux. Cependant, la mise en place d’un protocole MAC multi-canal dans un réseau multisauts nécessite une méthode efficace d’allocation des canaux pour permettre une coordination entre les nœuds afin de partager les canaux disponibles. Dans cette thèse, nous nous intéressons à la conception d’un protocole MAC multi-canal qui répond aux exigences des applications de collecte de données à haut débit dans un réseau multi-saut. Pour ce faire, nous abordons d’abord les principales façons d’utiliser plusieurs canaux pour réaliser le partage du médium. Ensuite, nous proposons un protocole MAC multi-canal, répondant aux exigences des RCSF à haut débit, qui combine les trois techniques TDMA, CSMA et FDMA. En effet, nous utilisons une nouvelle méthode d’allocation des canaux qui permet aux nœuds de choisir le canal de réception le plus convenable dans leurs voisinages jusqu’à 3-sauts d’une façon distribuée afin de minimiser les effets des interférences et des collisions. Enfin, nous évaluons par simulation les performances de notre protocole et nous le comparons à d’autres protocoles proposés dans la littérature. Les résultats obtenus montrent l’efficacité de notre proposition dans les différents scénarios étudiés. / The use of multi-channel significantly improves the overall network performance of wireless sensor networks (WSNs) by allowing parallel transmissions over multiple channels. However, the design of a multi-channel MAC protocol in a multi-hop network requires an efficient channel allocation method that allows the coordination between the nodes in order to share available channels. In this thesis, we focus on the conception of a multi-channel MAC protocol that meets the requirements of high data collection applications in a multi-hop network. In order to achieve this goal, we first present the main techniques to use multiple channels to realize medium access sharing. Then, we propose a multi-channel MAC protocol that meets the requirements of high data rate WSNs, which combines three techniques TDMA, FDMA and CSMA. Indeed, we use a new channel assignment method that enables nodes to choose the most convenient channel in their 3-hop neighborhood in a distributed manner in order to minimize the effects of interferences and collisions. Finally, we evaluate by simulation the performance of our protocol and we compare it to other protocols proposed in the literature. The results show the efficiency of our proposition in the different studied scenarios.
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Networking of UAVs Using 802.11sPolumuru, Pushpa 05 1900 (has links)
The thesis simulates the problem of network connectivity that occurs due to the dynamic nature of a network during flight. Nine nodes are provided with initial positions and are flown based on the path provided by leader-follower control algorithm using the server-client model. The application layer provides a point to point connection between the server and client and by using socket programming in the transport layer, a server and clients are established. Each node performs a neighbor discovery to discover its neighbors in the data link layer and physical layer performs the CSMA/CA using RTS/CTS. Finally, multi hop routing is achieved in network layer. Each client connects with server at dedicated interval to share each other location and then moves to next location. This process is continued over a period of several iterations until the relative distance is achieved. The constraints and limitations of the technology are network connectivity is lack of flexibility for random location of nodes, links established with a distant node having single neighbor is unstable. Performance of a system decreases with increase in number of nodes.
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Virtualisation de réseaux fixes et mobiles / Virtualization of fixed and mobile networksBenchaib, Yacine 25 March 2014 (has links)
Un nombre important d'outils d'expérimentation permettent aujourd'hui l'étude de problématiques pour les réseaux fixes et mobiles multi sauts. En s'appuyant sur un état de l'art faisant état des différentes fonctionnalités et caractéristiques propres aux outils et méthodes d'expérimentation les plus couramment utilisés, cette thèse vise à évaluer des outils d'expérimentations innovants. Concernant l'étude des réseaux fixes, nous proposons VIRCONEL, un outil permettant la définition de topologies réseaux virtuelles ainsi que la réalisation de scénario dans des conditions réalistes. Pour l'étude des réseaux mobiles multi sauts, nous proposons tout d'abord SILUMOD, un langage qui permet de définir aisément à l'aide de mots clés et d'opérateurs spécifiques les caractéristiques du mouvement d'un nœud mobile. Nous proposons ensuite VIRMANEL, un outil permettant la gestion des connexions entre des nœuds mobiles multi sauts représentés par des machines virtuelles, à l'aide d'un algorithme optimisant la mise à jour des liens effectifs entre ces nœuds mobiles. En associant SILUMOD et VIRMANEL, nous obtenons ainsi un outil capable de simuler les déplacements d'un nœud mobile tout en évaluant et établissant les connections potentielles entre ces nœuds mobiles. Les évaluations de ces outils montrent que si la virtualisation est effectivement un outil pertinent et utile pour l’expérimentation des réseaux, elle a aussi ses limites et le réalisme des résultats dépend des conditions d’expérimentation. Nous discutons de cette problématique et proposons, à l’issue de cette thèse, quelques critères permettant d’évaluer le degré de confiance à accorder à un résultat. / A significant number of experimental tools now allow the study of problems for fixed and mobile multi -hop networks. Based on a state of the art reporting different features and characteristics specific to different testing methods, this thesis aims to provide some assessment of these innovative experiments tools. Concerning the study of fixed networks , we propose and evaluate VIRCONEL , a tool for the definition of virtual network topologies as well as the realization of scenario under realistic conditions. For the study of mobile multi-hop networks , we first propose SILUMOD , a language that allows using specific keywords and operators to easily define characteristics of the movement of a mobile node. We then propose VIRMANEL , a tool for managing connections between mobile nodes represented by virtual machines, using an algorithm optimizing the update of effective links between mobile nodes. By combining SILUMOD and VIRMANEL , we obtain a tool to simulate the movement of a mobile node while evaluating and establishing potential connections between mobile nodes. Evaluations of these tools show that if virtualization is indeed a relevant and useful tool for network experiments , it also has its limitations and the realism of results depends on experimental conditions. We discuss this problem and propose at the end of this thesis , some criteria for assessing the degree of trust to give a result.
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Performance of UE Relaying for 6G NetworksHermoso Díaz, Celia January 2023 (has links)
Throughout the evolution of communication networks, users have consistently been demanding additional data and coverage. Future 6G networks seek to enable a seamless cyber-physical world through interconnected and integrated connectivity. Hereafter, to address these challenges and ensure the adaptability of future wireless networks, new technologies emerge. Relaying presents an attractive alternative, as it can be a cost-efficient deployment of highly dense networks, and it can enhance the performance of mobile networks in terms of both coverage and capacity. In addition, to meet the demanding Key Performance Indicators (KPI) of user experience, the relaying can be achieved via a User Equipment (UE) through UE-to-Network relaying as an alternative to conventional small-cell deployment of relay stations. The purpose of this project is to assess the impact of UE-based relaying policies. A comparative analysis is conducted, examining these schemes and a macro-only deployment. The study begins by conducting an analysis of the Third Generation Partnership Project (3GPP) urban macro scenario and then extends to include the real-world deployment scenario in London. Results have validated that UE relaying techniques help improve cell edge capacity and coverage compared to macro-only deployments. User throughput is enhanced up to three times in Downlink (DL) and twelve times in Uplink (UL) in the 3GPP urban macro deployment. While user throughput is improved up to ten times in DL and thirteen times in UL on the London map deployment. / Under utvecklingen av kommunikationsnätverk har användarna konsekvent efterfrågat ytterligare data och täckning. Framtida 6G-nätverk strävar efter att möjliggöra en sömlös cyber-fysisk värld genom sammanlänkad och integrerad anslutning. För att möta dessa utmaningar och säkerställa anpassningsbarheten hos framtida trådlösa nätverk framträder nya teknologier. Reläering utgör ett attraktivt alternativ eftersom det kan vara en kostnadseffektiv implementering av högt täta nätverk och signifikant förbättra prestandan hos mobila nätverk både vad gäller täckning och kapacitet. Dessutom kan reläeringen användas för att möta de utmanande behoven av användarupplevelse genom att användarutrustning (UE) används för reläeringen, vilket utgör ett alternativ till konventionell implementering av småceller för relästationer. Det primära fokuset för detta projekt är att bedöma påverkan av reläeringspolicyn baserad på UE. En jämförande analys genomförs där dessa metoder och enbart makroimplementering undersöks. Inledningsvis utförs studien i en urbant makroscen från Third Generation Partnership Project (3GPP), vilket utgör en grund för att utöka metodologin till en verklig implementeringsscen i London. Resultaten har visat att UE-reläeringstekniker bidrar till att förbättra kapaciteten och täckningen i cellens utkanter jämfört med enbart makroimplementering. Användarnas genomströmning ökar upp till tre gånger i nerlänken (DL) och tolv gånger i upplänken (UL) i 3GPP: s urbana makroimplementering. Samtidigt förbättras användarnas genomströmning upp till tio gånger (DL) och tretton gånger (UL) i Londonkartaimplementationen.
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Effective Use of Network Coding in Multi-hop Wireless NetworksChi, Yang January 2013 (has links)
No description available.
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Analytical Model for Capacity and Delay Optimization in Wireless Mesh NetworksFu, Weihuang January 2010 (has links)
No description available.
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Delay-Aware Multi-Path Routing in a Multi-Hop Network: Algorithms and ApplicationsLiu, Qingyu 21 June 2019 (has links)
Delay is known to be a critical performance metric for various real-world routing applications including multimedia communication and freight delivery. Provisioning delay-minimal (or at least delay-bounded) routing services for all traffic of an application is highly important. As a basic paradigm of networking, multi-path routing has been proven to be able to obtain lower delay performance than the single-path routing, since traffic congestions can be avoided. However, to our best knowledge, (i) many of existing delay-aware multi-path routing studies only consider the aggregate traffic delay. Considering that even the solution achieving the optimal aggregate traffic delay has a possibly unbounded delay performance for certain individual traffic unit, those studies may be insufficient in practice; besides, (ii) most existing studies which optimize or bound delays of all traffic are best-effort, where the achieved solutions have no theoretical performance guarantee.
In this dissertation, we study four delay-aware multi-path routing problems, with the delay performances of all traffic taken into account. Three of them are in communication and one of them is in transportation. Note that our study differ from all related ones as we are the first to study the four fundamental problems to our best knowledge. Although we prove that our studied problems are all NP-hard, we design approximation algorithms with theoretical performance guarantee for solving each of them. To be specific, we claim the following contributions.
Minimize maximum delay and average delay. First, we consider a single-unicast setting where in a multi-hop network a sender requires to use multiple paths to stream a flow at a fixed rate to a receiver. Two important delay metrics are the average sender-to-receiver delay and the maximum sender-to-receiver delay. Existing results say that the two delay metrics of a flow cannot be both within bounded-ratio gaps to the optimal. In comparison, we design three different flow solutions, each of which can minimize the two delay metrics simultaneously within a $(1/epsilon)$-ratio gap to the optimal, at a cost of only delivering $(1-epsilon)$-fraction of the flow, for any user-defined $epsilonin(0,1)$. The gap $(1/epsilon)$ is proven to be at least near-tight, and we further show that our solutions can be extended to the multiple-unicast setting.
Minimize Age-of-Information (AoI). Second, we consider a single-unicast setting where in a multi-hop network a sender requires to use multiple paths to periodically send a batch of data to a receiver. We study a newly proposed delay-sensitive networking performance metric, AoI, defined as the elapsed time since the generation of the last received data. We consider the problem of minimizing AoI subject to throughput requirements, which we prove is NP-hard. We note that our AoI problem differs from existing ones in that we are the first to consider the batch generation of data and multi-path communication. We develop both an optimal algorithm with a pseudo-polynomial time complexity and an approximation framework with a polynomial time complexity. Our framework can build upon any polynomial-time $alpha$-approximation algorithm of the maximum delay minimization problem, to construct an $(alpha+c)$-approximate solution for minimizing AoI. Here $c$ is a constant dependent on throughput requirements.
Maximize network utility. Third, we consider a multiple-unicast setting where in a multi-hop network there exist many network users. Each user requires a sender to use multiple paths to stream a flow to a receiver, incurring an utility that is a function of the experienced maximum delay or the achieved throughput. Our objective is to maximize the aggregate utility of all users under throughput requirements and maximum delay constraints. We observe that it is NP-complete either to construct an optimal solution under relaxed maximum delay constraints or relaxed throughput requirements, or to figure out a feasible solution with all constraints satisfied. Hence it is non-trivial even to obtain approximate solutions satisfying relaxed constraints in a polynomial time. We develop a polynomial-time approximation algorithm. Our algorithm obtains solutions with constant approximation ratios under realistic conditions, at the cost of violating constraints by up to constant-ratios.
Minimize fuel consumption for a heavy truck to timely fulfill multiple transportation tasks. Finally, we consider a common truck operation scenario where a truck is driving in a national highway network to fulfill multiple transportation tasks in order. We study an NP-hard timely eco-routing problem of minimizing total fuel consumption under task pickup and delivery time window constraints. We note that optimizing task execution times is a new challenging design space for saving fuel in our multi-task setting, and it differentiates our study from existing ones under the single-task setting. We design a fast and efficient heuristic. We characterize conditions under which the solution of our heuristic must be optimal, and further prove its optimality gap in case the conditions are not met. We simulate a heavy-duty truck driving across the US national highway system, and empirically observe that the fuel consumption achieved by our heuristic can be $22%$ less than that achieved by the fastest-/shortest- path baselines. Furthermore, the fuel saving of our heuristic as compared to the baselines is robust to the number of tasks. / Doctor of Philosophy / We consider a network modeled as a directed graph, where it takes time for data to traverse each link in the network. It models many critical applications both in the communication area and in the transportation field. For example, both the European education network and the US national highway network can be modeled as directed graphs. We consider a scenario where a source node is required to send multiple (a set of) data packets to a destination node through the network as fast as possible, possibly using multiple source-to-destination paths. In this dissertation we study four problems all of which try to figure out routing solutions to send the set of data packets, with an objective of minimizing experienced travel time or subject to travel time constraints. Although all of our four problems are NP-hard, we design approximation algorithms to solve them and obtain solutions with theoretically bounded gaps as compared to the optimal. The first three problems are in the communication area, and the last problem is in the transportation field. We claim the following specific contributions. Minimize maximum delay and average delay. First, we consider the setting of simultaneously minimizing the average travel time and the worst (largest) travel time of sending the set of data packets from source to destination. Existing results say that the two metrics of travel time cannot be minimized to be both within bounded-ratio gaps to the optimal. As a comparison, we design three different routing solutions, each of which can minimize the two metrics of travel time simultaneously within a constant bounded ratio-gap to the optimal, but at a cost of only delivering a portion of the data. Minimize Age-of-Information (AoI). Second, we consider the problem of minimizing a newly proposed travel-time-sensitive performance metric, i.e., AoI, which is the elapsed time since the generation of the last received data. Our AoI study differs from existing ones in that we are the first to consider a set of data and multi-path routing. We develop both an optimal algorithm with a pseudo-polynomial time complexity and an approximation framework with a polynomial time complexity. Maximize network utility. Third, we consider a more general setting with multiple source destination pairs. Each source incurs a utility that is a function of the experienced travel time or the achieved throughput to send data to its destination. Our objective is to maximize the aggregate utility under throughput requirements and travel time constraints. We develop a polynomial-time approximation algorithm, at the cost of violating constraints by up to constant-ratios. It is non-trivial to design such algorithms, as we prove that it is NPcomplete either to construct an optimal solution under relaxed delay constraints or relaxed throughput requirements, or to figure out a feasible solution with all constraints satisfied. Minimize fuel consumption for a heavy truck to timely fulfill multiple transportation tasks. Finally, we consider a truck and multiple transportation tasks in order, where each task requires the truck to pick up cargoes at a source timely, and deliver them to a destination timely. The need of coordinating task execution times is a new challenging design space for saving fuel in our multi-task setting, and it differentiates our study from existing ones under the single-task setting. We design an efficient heuristic. We characterize conditions under which the solution of our heuristic must be optimal, and further prove its performance gap as compared to the optimal in case the conditions are not met.
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Wide-area broadband private wireless communication system / 広域広帯域自営無線通信システムMakino, Kiminobu 25 March 2024 (has links)
付記する学位プログラム名: 社会を駆動するプラットフォーム学卓越大学院プログラム / 京都大学 / 新制・課程博士 / 博士(情報学) / 甲第25442号 / 情博第880号 / 京都大学大学院情報学研究科通信情報システム専攻 / (主査)教授 原田 博司, 教授 大木 英司, 教授 梅野 健, 教授 中村 公人 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM
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Network coding for quality of service in wireless multi-hop networks / Codage réseau pour la qualité de service dans les réseaux sans fil multi-sautsBenfattoum, Youghourta 15 November 2012 (has links)
Dans cette thèse, nous nous intéressons à l’application du codage réseau pour garantir la qualité de service (QoS) dans les réseaux sans fil multi-sauts. Comme le support de transmission est partagé, les réseaux sans fil souffrent de l’impact négatif des interférences sur la bande passante. Il est alors intéressant de proposer une approche basée sur le codage réseau qui prenne en compte ces interférences durant le processus de routage. Dans ce contexte, nous proposons d’abord un algorithme minimisant l’impact des interférences pour des flux unicast tout en respectant la bande passante qu’ils exigent. Puis, nous le combinons avec le codage réseau afin d’augmenter le nombre des flux acceptés et avec le contrôle de topologie pour améliorer davantage la gestion des interférences. Nous montrons par simulation l’intérêt de combiner les trois domaines : codage réseau, gestion des interférences et contrôle de topologie. Nous abordons également la gestion du délai pour les flux multicast et utilisons le codage réseau basé sur les générations (GBNC) qui combine les paquets par bloc. La plupart des travaux portant sur le GBNC considèrent une taille de génération fixe mais à cause des variations de l’état du réseau le délai de décodage et de récupération du bloc de paquets peut varier, dégradant la QoS. Pour résoudre ce problème, nous proposons une méthode qui ajuste la taille de la génération de façon dynamique pour respecter un certain délai de décodage avec prise en compte des contextes réseau et contenu. De plus, nous améliorons notre approche pour contrecarrer les pertes des acquittements. Puis, nous proposons de l’utiliser dans un réseau de domicile pour la diffusion de vidéo à la demande. Notre solution améliore la QoS et la qualité d’expérience pour l’utilisateur final sans équipement additionnel. Finalement, nous abordons un sujet plus théorique dans lequel nous présentons un nouveau réseau basé sur le schéma Butterfly pour des flux multi-sources multi-destinations. Nous caractérisons la taille du buffer du nœud source en utilisant la théorie des files d’attente et montrons qu’elle correspond aux résultats de simulation. / In this thesis we deal with the application of Network Coding to guarantee the Quality of Service (QoS) for wireless multi-hop networks. Since the medium is shared, wireless networks suffer from the negative interference impact on the bandwidth. It is thus interesting to propose a Network Coding based approach that takes into account this interference during the routing process. In this context, we first propose an algorithm minimizing the interference impact for unicast flows while respecting their required bandwidth. Then, we combine it with Network Coding to increase the number of admitted flows and with Topology Control to still improve the interference management. We show by simulation the benefit of combining the three fields: Network Coding, interference consideration and Topology Control. We also deal with delay management for multicast flows and use the Generation-Based Network Coding (GBNC) that combines the packets per blocks. Most of the works on GBNC consider a fixed generation size. Because of the network state variations, the delay of decoding and recovering a block of packets can vary accordingly degrading the QoS. To solve this problem, we propose a network-and content-aware method that adjusts the generation size dynamically to respect a certain decoding delay. We also enhance it to overcome the issue of acknowledgement loss. We then propose to apply our approach in a Home Area Network for Live TV and video streaming. Our solution provides QoS and Quality of Experience for the end user with no additional equipment. Finally, we focus on a more theoretical work in which we present a new Butterfly-based network for multi-source multi-destination flows. We characterize the source node buffer size using the queuing theory and show that it matches the simulation results.
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Distributed biconnectivity testing in Wireless multi-hop networksMilic, Bratislav 13 July 2010 (has links)
Ein drahtloses Multihop-Netzwerk (DMN) ist ein verteiltes Kommunikationssystem, welches vor allem die Fähigkeit zur automatischen Anpassung an sich ständig änderne Umgebungsbedingungen hat. Eine zentrale Fragestellung in DMNen ist, ob das Netzwerk partitioniert ist, ob also nicht mehr jeder Knoten mit jedem anderen Knoten kommunizieren kann. Um festzustellen, ob eine Partitionierung droht werden mit Hilfe von 2-Zusammenhangstests Brücken und Artikulationspunkte im Kommunikationsgraphen gesucht. Daraufhin können anschließend korrektive Aktionen eingeleitet werden um die Partitionierung zu verhindern und somit die Netzwerkverfügbarkeit zu erhöhen. Eine Vielzahl von 2-Zusammenhangstestverfahren wurde bereits erfolgreich bei drahtgebundenen Netzen eingesetzt. Allerdings sind diese Verfahren ungeeignet für drahtlose Netze, da die Ungenauigkeiten durch den häufigen Paketverlust in solchen Systemen bisher nicht berücksichtigt wurden. Mit Hilfe von stochastischen Modellen wird gezeigt, dass Fehler in der Entscheidungsfindung für DMNen bereits bei sehr einfachen Problemen wie der Link-Erkennung signifikant sein können. In dieser Arbeit werden daher verschiedene Verfahren präsentiert, die auch auf Grundlage unsicherer Informationen noch eine verlässliche Entscheidungsfindung ermöglichen. Die Arbeit präsentiert einen neuen verteilten Algorithmus zum Test auf 2-Zusammenhang, welcher Fehler durch Nachrichtenverlust berücksichtigt und gleichzeitig die Anzahl an Nachrichten reduziert. Basierend auf einer umfassenden Analyse der Einflüsse von Kommunikationsfehlern auf den Algorithmus, wurden Abstimmungsprozeduren entwickelt, die die Wahrscheinlichkeit von Fehlentscheidungen nochmals reduzieren. Zur weiteren Analyse werden die Algorithmen erstens in der Motelab-Umgebung und zweitens mit Hilfe von Simulationen untersucht. Die präsentierten Algorithmen zeigen überzeugende Ergebnisse unter variierenden Bedingungen, was ihre Anwendbarkeit in realen Szenarien unterstreicht. / Wireless multi-hop network (WMN) is a distributed communication system composed of autonomous processing nodes that is known for its ability to automatically adjust to rapidly changing conditions in the surrounding environment. Connectivity is one of the basic properties of a network. Removal of a bridge or an articulation point partitions a network. Biconnectivity testing identifies bridges and articulation points in a network, and once they are known corrective actions can be performed in order to improve network''s reliability. Numerous biconnectivity testing algorithms are successfully applied in graphs, wired networks and multiprocessor systems. However, they are inadequate for application in wireless networks since the frequent packet losses introduce uncertainty in the system which these algorithms cannot handle. The stochastic analysis shows that errors in decision-making in WMNs are considerable even for seemingly simple tasks such as the detection of links. The main contribution of this work is to provide means for accurate binary decision-making under uncertainty within the context of biconnectivity testing in WMNs. A distributed algorithm is developed that successfully handles the faults caused by message losses and simultaneously utilizes benefits of wireless communication to reduce message complexity from O(e) to O(n). Based on stochastic analysis of WMN topologies and a comprehensive analysis of impact of communication faults on algorithm''s behavior, the algorithm is extended by voting theory to reduce probability of erroneous decisions. The algorithm and the voting rules are evaluated in experiments in Motelab testbed and in the event-based simulator Jist/SWANS. The algorithm is accurate under various conditions which demonstrates its applicability in reality and capability of successful operation in presence of packet losses.
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