Dissertations / Theses on the topic 'Multipath transmission'
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Tedla, Sukesh Kumar. "Performance Evaluation of Concurrent Multipath Transmission : Measurements and Analysis." Thesis, Blekinge Tekniska Högskola, Institutionen för kommunikationssystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-10811.
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Context: The data transmission mechanisms in a multi-homed network has gained importance in the past few years because of its potentials. Concurrent multipath transmission (CMT) technique uses the available network interfaces for transmission by pooling multiple paths together. It allows transport mechanisms to work independent of the underlying technology, which resembles the concept of Transport Virtualization (TV). As a result, in the development of Future Internet Architectures (FIA), TV plays a vital role. The leading commercial software technologies like IOS and Android have implemented such mechanisms in their devices. Multipath TCP and CMT-SCTP are the protocols under development which support this feature. The implementation and evaluation of CMT in real-time is complex because of the challenges like path binding, out-of-order packet delivery, packet-reordering and end-to-end delay. Objectives: The main objective of this thesis is to identify the possibilities of implementing CMT in real-time using multiple access technologies, and to evaluate the performance of transmission by measurements and analysis under different scenarios. Methods: To fulfill the objectives of the thesis, different methods are adopted. The development of CMT scenario is based on a spiral methodology where each spiral refers to different objectives. The sub-stages in a spiral are mainly implementation, observations, decisions and modifications. In order to implement and identify the possibilities of CMT in real-time, a deep literature study is performed beforehand. Results: The throughput of data transmission is less affected by varying the total number of TCP connections in transmission. Under different cases it is observed that the throughput has significant impact by varying number of efficient paths in transmission. Conclusion: From the experimental methodology of this work it can be observed that, CMT can be implemented in real-time using off-the-shelf components. Based on the experimentation results, it can be concluded that the throughput of transmission is affected by increasing number of paths. It can also be concluded that the total number of TCP connections during the transmission have less impact on throughput.
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Landron, Orlando. "Microwave multipath resolution in microcellular channels." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03032009-040639/.
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Pérez, Tejada Natalia. "Cosine Modulated Filter Banks Systems in the Presence of Multipath Transmission." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9651.
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Pyk, Axel. "Multipath TCP : Performance in a LTE Environment." Thesis, Linköpings universitet, Databas och informationsteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129123.
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The market penetration of mobile access devices with multiple network interfaces has increased dramatically over the last few years. As a consequence, the quest for a widespread multi-path transport protocol that takes advantage of all available interfaces simultaneously to increase data throughput and improve robustness, has received considerable attention. One prominent protocol introduced by the IETF is Multipath TCP (MPTCP). MPTCP is an extension to the predominant single-path transport protocol, the Transport Control Protocol (TCP) that enables multihomed devices to aggregate available resources transparently to the applications. Combining multiple radio access technologies, like LTE and Wi-Fi, with diverse characteristics in terms of transmission rates and fluctuations opens for novel challenges that may disrupt and even harm the data throughput. Therefore MPTCP must take path heterogeneity into account. For MPTCP to supersede single-path TCP it is required that MPTCP always achieve at least the throughput of the best individual TCP path. This thesis investigates if MPTCP with uncoupled congestion control fulfills this condition, and if so, how much it improves the throughput. By examining the protocol in a deterministic emulated environment defined by the characteristics of LTE, we conclude two key factors impacting the outcome: the download size and the difference in characteristics between the paths. Our experiments show that MPTCP overall fulfills this task, especially during path homogeneity with near aggregated results. But we also show that MPTCP may decrease data throughput with 16% compared to TCP during path heterogeneity. Hence MPTCP does not always fulfill the goal of throughput. We therefore conclude further intelligence is needed for the packet scheduling mechanism to avoid throughput degradation in the initial phase of a transmission.
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Sherratt, Simon. "Reduction of vestigial sideband effects due to multipath transmission in terrestrial broadcast television." Thesis, University of Salford, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308288.
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In terrestrial television transmission multiple paths of various lengths can occur between the transmitter and the receiver. Such paths occur because of reflections from objects outside the direct transmission path. The multipath signals arriving at the receiver are all detected along with the intended signal causing time displaced replicas called 'ghosts' to appear on the television picture. With an increasing number of people living within built up areas, ghosting is becoming commonplace and therefore deghosting is becoming increasingly important. This thesis uses a deterministic time domain approach to deghosting, resulting in a simple solution to the problem of removing ghosts. A new video detector is presented which reduces the synchronous detector local oscillator phase error, caused by any practical size of ghost, to a lower level than has ever previously been achieved. From the new detector, dispersion of the video signal is minimised and a known closed-form time domain description of the individual ghost components within the detected video is subsequently obtained. Developed from mathematical descriptions of the detected video, a new specific deghoster filter structure is presented which is capable of removing both inphase (I) and also the phase quadrature (Q) induced ghost signals derived from the VSB operation. The new deghoster filter requires much less hardware than any previous deghoster which is capable of removing both I and Q ghost components. A new channel identification algorithm was also required and written which is based upon simple correlation techniques to find the delay and complex amplitude characteristics of individual ghosts. The result of the channel identification is then passed to the new I and Q deghoster filter for ghost cancellation. Generated from the research work performed for this thesis, five papers have been published.
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Ramaboli, Allen Lehopotseng. "Concurrent multipath transmission to improve performance for multi-homed devices in heterogeneous networks." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20404.
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Recent network technology developments have led to the emergence of a variety of access network technologies - such as IEEE 802.11, wireless local area network (WLAN), IEEE 802.16, Worldwide Interoperability for Microwave Access (WIMAX) and Long Term Evolution (LTE) - which can be integrated to offer ubiquitous access in a heterogeneous network environment. User devices also come equipped with multiple network interfaces to connect to the different network technologies, making it possible to establish multiple network paths between end hosts. However, the current connectivity settings confine the user devices to using a single network path at a time, leading to low utilization of the resources in a heterogeneous network and poor performance for demanding applications, such as high definition video streaming. The simultaneous use of multiple network interfaces, also called bandwidth aggregation, can increase application throughput and reduce the packets' end-to-end delays. However, multiple independent paths often have heterogeneous characteristics in terms of offered bandwidth, latency and loss rate, making it challenging to achieve efficient bandwidth aggregation. For instance, striping the flow's packets over multiple network paths with different latencies can cause packet reordering, which can significantly degrade performance of the current transport protocols. This thesis proposes three new solutions to mitigate the effects of network path heterogeneity on the performance of various concurrent multipath transmission settings. First, a network layer solution is proposed to stripe packets of delay-sensitive and high-bandwidth applications for concurrent transmission across multiple network paths. The solution leverages the paths' latency heterogeneity to reduce packet reordering, leading to minimal reordering delay, which improves performance of delay-sensitive applications. Second, multipath video streaming is developed for H.264 scalable video, where the reference video packets are adaptively assigned to low loss network paths to reduce drifting errors, thus combatting H.264 video distortion effectively. Finally, a new segment scheduling framework - which carefully considers path heterogeneity - is incorporated into the IETF Multipath TCP to improve throughput performance. The proposed solutions have been validated using a series of simulation experiments. The results reveal that the proposed solutions can enable efficient bandwidth aggregation for concurrent multipath transmission over heterogeneous network paths.
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Iyengar, Janardhan R. "End-to-end concurrent multipath transfer using transport layer multihoming." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 1.67 Mb., p. 123, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3220807.
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劉慶強 and Hing-keung Lau. "Pilot-symbol-aided techniques for spectrally efficient signals in multipath-fading channels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31237198.
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吳萬雄 and Man-hung Ng. "Bandwidth-efficient pilot-symbol-aided techniques for fading estimation in multipath fading channels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242212.
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Teal, Paul D., and p. teal@irl cri nz. "Real Time Characterisation of the Mobile Multipath Channel." The Australian National University. Research School of Information Sciences and Engineering, 2002. http://thesis.anu.edu.au./public/adt-ANU20020722.085502.
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In this thesis a new approach for characterisation of digital mobile radio channels is investigated. The new approach is based on recognition of the fact that while the fading which is characteristic of the mobile radio channel is very rapid, the processes underlying this fading may vary much more slowly. The comparative stability of these underlying processes has not been exploited in system designs to date.
Channel models are proposed which take account of the stability of the
channel. Estimators for the parameters of the models are proposed, and their performance is analysed theoretically and by simulation and
measurement.
Bounds are derived for the extent to which the mobile channel can be
predicted, and the critical factors which define these bounds are
identified.
Two main applications arise for these channel models. The first is the
possibility of prediction of the overall system performance. This may be used to avoid channel fading (for instance by change of frequency), or
compensate for it (by change of the signal rate or by power control). The
second application is in channel equalisation. An equaliser based on a
model which has parameters varying only very slowly can offer improved
performance especially in the case of channels which appear to be varying
so rapidly that the convergence rate of an equaliser based on the
conventional model is not adequate.
The first of these applications is explored, and a relationship is derived between the channel impulse response and the performance of a broadband system.
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Krishnan, Anupama. "The Multipath Fault-Tolerant Protocol for Routing in Packet-Switched Communication Network." Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc4199/.
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In order to provide improved service quality to applications, networks need to address the need for reliability of data delivery. Reliability can be improved by incorporating fault tolerance into network routing, wherein a set of multiple routes are used for routing between a given source and destination. This thesis proposes a new fault-tolerant protocol, called the Multipath Fault Tolerant Protocol for Routing (MFTPR), to improve the reliability of network routing services. The protocol is based on a multipath discovery algorithm, the Quasi-Shortest Multipath (QSMP), and is designed to work in conjunction with the routing protocol employed by the network. MFTPR improves upon the QSMP algorithm by finding more routes than QSMP, and also provides for maintenance of these routes in the event of failure of network components. In order to evaluate the resilience of a pair of paths to failure, this thesis proposes metrics that evaluate the non-disjointness of a pair of paths and measure the probability of simultaneous failure of these paths. The performance of MFTPR to find alternate routes based on these metrics is analyzed through simulation.
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Zinner, Thomas [Verfasser], and Phuoc [Akademischer Betreuer] Tran-Gia. "Performance Modeling of QoE-Aware Multipath Video Transmission in the Future Internet / Thomas Zinner. Betreuer: Phuoc Tran-Gia." Würzburg : Universitätsbibliothek der Universität Würzburg, 2012. http://d-nb.info/1025223810/34.
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Chen, Xiaomin [Verfasser], and Ashwin [Akademischer Betreuer] Gumaste. "Performance Analysis of Parallel Transmission and Multipath Routing in High-Speed Network Systems / Xiaomin Chen ; Betreuer: Ashwin Gumaste." Braunschweig : Technische Universität Braunschweig, 2014. http://d-nb.info/117582075X/34.
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Li, Shuang Lim Alvin S. "Improving throughput of video streaming in wireless sensor networks." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Computer_Science_and_Software_Engineering/Thesis/Li_Shuang_55.pdf.
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Moussa, Ali. "Egalisation aveugle, application pour des canaux de transmission." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC267/document.
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Les travaux de cette thèse portent sur l'égalisation des canaux de transmission pour des modulations mono-porteuses et multi-porteuses. Dans le cadre de l'égalisation, nous nous intéressons, plus précisément, à l'égalisation aveugle. Tout d'abord, nous décrivons les différents éléments constituants une chaîne de communication, et les différents types de modulations mono-porteuses et muti-porteuses (OFDM). Ensuite, nous faisons un état de l'art sur les méthodes de l'égalisation aveugle pour une modulation mono-porteuse. Nous proposons par la suite un algorithme d'égalisation aveugle en présence de perturbations bornées. Ensuite, nous fournissons une analyse de stabilité et de convergence de l'algorithme proposé. Dans le cadre de la modulation multi-porteuse, nous présentons, dans un premier temps, un état de l'art sur les techniques d'égalisation aveugle pour le système OFDM. Ensuite, nous adaptons l'algorithme proposé pour le système OFDM pour des canaux à trajets multiples, en particulier les canaux Raleigh et Rice. Les performances de l'algorithme proposé sont illustrées à travers plusieurs exemples en simulation tout au long de la thèseThe work of this thesis deals with the equalization of the transmission channels for a single-carrier and multi-carrier modulation. In the context of equalization, we focus precisely on the blind equalization. First, we give a description of various elements constituting a communication chain, a description of different types of single-carrier modulations and a description of a multi-carrier modulation (OFDM). Then, we give an overview of the blind equalization methods for a single-carrier modulation. We propose subsequently a blind equalization algorithm in the presence of a bounded perturbation. Next, we provide stability and convergence analysis of the proposed method. In the context of multi-carrier modulation, we first present an overview of the blind equalization techniques for the OFDM system. Next, we adapt the proposed method for the OFDM system under multipath channels, especially the Raleigh and the Rice channels. Performance of the proposed algorithm have been illustrated in simulation by considering many examples throughout this thesis
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Kresta, Daniel. "Analýza přenosu mobilního digitálního rozhlasového vysílání." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-241058.
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This thesis deals with an analysis of a system called Digital Audio Broadcast and describes its mathematical model created in MATLAB program. In the first part basic blocks of a transmitter and a receiver are analyzed along with their principles. Then different types of transmission channels for static, portable and mobile receivers are described. The second part contains description of the DAB mathematical model itself. Individual blocks are described in the order of the DAB signal path, from the transmitter through the transmission channel to the receiver side. In this part the graphical user interface is also described. In the final part the results of experimental measurements and simulations are presented.
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Jourdain, Dominique. "Caractérisation expérimentale du canal sous-marin petit fond pour la transmission acoustique horizontale." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0074.
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En milieu sous-marin, les performances des systemes de communication par voie acoustique sont limitees par les conditions de propagation: le milieu est bruyant, variable, diffuseur, multitrajets celles-ci sont encore plus defavorables en petits fonds, en raison des interactions multiples des rayons sonores avec la surface et le fond. L'etalement de la reponse peut alors correspondre a plusieurs temps symboles et creer de l'interference entre symboles transmis. Par ailleurs, l'addition des trajets multiples provoquent des evanouissements en reception. Enfin, le milieu est tres variable en temps, et les divers mouvements de la surface et des transducteurs induisent de l'effet doppler. Ce travail de these propose une etude aussi systematique que possible des caracteristiques du canal de transmission petit fond dans la gamme des frequences utiles aux transmissions acoustiques. Il est base sur des signaux experimentaux enregistres sur une quinzaine de sites differents. L'ensemble des donnees recueillies couvre une large variete de configurations (hauteur d'eau, distance de transmission, etats de surface et type de fond). Les reponses impulsionnelles du canal sont obtenues par filtrage adapte de signaux modules en phase. Leur analyse permet d'etudier l'influence des conditions experimentales sur la structure des trajets multiples. Les retards, amplitudes et phases des trajets principaux sont analyses dans la mesure du possible et donnent des renseignements directs sur les qualites des reflexions surface et fond. On evalue egalement l'influence des conditions de propagation sur les parametres pertinents pour la definition des systemes de transmission de donnees: etalement temporel, doppler, taux de fading, frequences et durees des evanouissements en reception. Un chapitre de synthese examine la valeur des parametres obtenus en fonction des imperatifs de la communication
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Daniele, Norbert. "Étude d'un système de transmission radio courte portée à 60 GHz par étalement de spectre." Grenoble INPG, 1995. http://www.theses.fr/1995INPG0145.
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Nous considerons dans ce memoire le probleme des transmissions radio numeriques de courte portee d'exterieurs a 60 ghz. Dans cette gamme de frequence, nous avons montre theoriquement et constate experimentalement, grace a la realisation d'un sondeur de canal radio, que les conditions de propagation etaient tres difficiles. Cependant, des phenomenes de reflexion et plus rarement de diffraction permettent d'etablir des liaisons hors visibilite, mais on se heurte alors aux degradations induites par la propagation multi-trajets. Pour combattre ces degradations, nous avons mis au point un couple emetteur-recepteur a etalement de spectre par sequence directe a 59,45 ghz utilisant en reception un filtre adapte a ondes acoustiques de surface. Ce systeme permet de tirer profit de tous les trajets de propagation, tout en assurant une grande discretion des liaisons puisque la densite spectrale de puissance emise est etalee sur une large bande. Les mesures de liaisons numeriques a 256 kbit/s realisees confirment les difficultes de propagation et tout particulierement dans un environnement rural ou les taux d'erreurs de bit (teb) sont rarement acceptables. En milieu suburbain et urbain la presence de reflecteurs favorise les echos ce qui devrait permettre dans une structure cellulaire de couvrir des zones dont le diametre maximal est compris entre 150 et 200 m. Moyennant une optimisation des parametres de modulation et l'elaboration d'une version numerique du filtre a ondes de surface, le systeme de transmission presente dans ce memoire constituera une excellente solution pour la realisation des futures liaisons de proximite. L'optimisation des parametres doit etre facilitee a court terme par l'emploi des outils de simulation decrits en derniere partie de cette these. L'incertitude sur l'avancement des technologies integrees en ondes millimetriques demeure aujourd'hui un frein
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Mitharwal, Pratibha. "A study of IP network mobility in a multihomed context." Thesis, Télécom Bretagne, 2016. http://www.theses.fr/2016TELB0407/document.
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Cette thèse présente une solution pour améliorer la mobilité des réseaux, dans le cadre de communications véhiculaires ainsi que pour la distribution de contenu. Les solutions actuelles pour les communications véhiculaires (c'est-à-dire lorsqu'un réseau est mobile) reposent sur la mise en place de tunnels, permettant également d'utiliser simultanément les différentes interfaces disponibles sur le véhicule (multi-homing). Même avec des tunnels, ces solutions ne sont pas en mesure d'équilibrer le trafic sur les interfaces réseau disponibles, elles ne parviennent pas à tirer partie du multi-homing. De plus, certaines des solutions existantes pour la mobilité de réseau cachent la mobilité aux hôtes connectés au routeur mobile. De fait, cela empêche les hôtes de participer aux décisions relatives au multi-homing, telles que le choix de l'interface réseau à utiliser, ce qui est pourtant utile pour réaliser du routage à moindre coût. Dans cette thèse, nous proposons de combiner un protocole de mobilité réseau (tel que NEMO) avec le protocole de TCP-multivoies (MPTCP), ce qui permet aux nœuds hôtes de participer à la mobilité et au multi-homing. Cette nouvelle combinaison améliore significativement le routage et l'encapsulation de paquets causée par les tunnels. En outre, cela augmente le débit, la tolérance de panne, le temps d'aller-retour et réduit le délai de transmission. La deuxième contribution de ce travail propose une solution de continuité de session pour la distribution de contenu dans les réseaux 5G. Dans le réseau 5G, les équipements d'accès IP seront au plus proche des nœuds terminaux afin d'améliorer l'expérience utilisateur et de réduire la charge de trafic dans le réseau central. Le fait est qu'à un instant donné un terminal ne peut être raccordé qu'à une seule passerelle (SGW/PGW) à la fois. Et comme la passerelle change lors de la mobilité, les sessions en cours seront rompues, impactant les applications temps réelle, le streaming vidéo, les jeux, etc. Pour cela, la thèse présente une solution de continuité de session avec l'aide de TCP-multivoie en bénéficiant du fait que les serveurs de contenu sont stationnairesThis thesis presents a solution for boosting network mobility in the context of vehicular communications and content distribution in fixed network. Existing solutions for vehicular communications (i.e., network mobility), relies on tunneling in order to use multiple available interfaces on a vehicle. Even with tunnels, these solutions are unable to balance the traffic over available network interfaces thus do not reach the goal to provide optimum multi-homing benefits. Moreover, some of the existing solutions for network mobility, hide the mobility from the hosts connected to the mobile router. This in result inhibits the host nodes from participating in multi-homing related decisions such as interface selection which can be helpful in performing least cost routing. In this thesis, we propose to combine network mobility protocol with MPTCP which enables the host nodes to participate in mobility and multi-homing. This novel combination significantly improves routing and tunneling packet overhead. Moreover it increases throughput, fault tolerance, round-trip time and reduces transmission delay. The second contribution of this work is providing a solution for session continuity in context of content distribution in 5G networks. In 5G network, the IP edges will be closer to the host nodes in order to improve the user experience and reduce traffic load in the core network. The fact that a host can only be connected to a single gateway (SGW/PGW) at a time, would break the ongoing sessions for real time applications like video streaming or gaming during an occurrence of mobility event requiring gateway relocation. The thesis presents the solution for session continuity with the help of multipath TCP by benefiting from the fact that the content servers are stationary
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Bouatit, Mohamed Nacer. "Optimisation du routage, tolérance aux pannes et gestion de l'énergie et de l'interférence pour la transmission des flux multimédia temps réel dans les réseaux de capteur sans fil." Thesis, Paris, CNAM, 2018. http://www.theses.fr/2018CNAM1188/document.
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Les applications multimédias, dans les réseaux de capteurs sans fil, véhiculent des données volumineuses, qui nécessitent un taux de transmission élevé et un traitement intensif et par conséquent une consommation d'énergie importante. Transmettre efficacement ces flux hétérogènes, tout en assurant leur fiabilité et garantir les exigences de QoS, avec les ressources limitées disponibles, en particulier dans les contextes critiques, demeure un verrou scientifique ouvert. C’est pourquoi, dans le cadre de cette thèse, nous nous sommes intéressés aux aspects liés : au routage, à la tolérance aux pannes et à la gestion des interférences dans les RCMSF.Compte tenu, du très faible nombre de protocoles de routage, qui ont approché la phase expérimentale et encore moins ceux qui l’ont abordé pendant la transmission des données en temps réel, nous avons développé dans ce contexte, un protocole routage géographique baptisé GNMFT (Geographic Non-interfering Multipath Fault-tolerant),En premier lieu, nous avons amélioré le mode de sélection des nœuds, utilisé par le transfert glouton, pour faire face au problème du Minimum-local, où une fonction objective multicritères (distance, énergie et puissance de réception) relative au choix du prochain saut a été définie. Puis, nous avons introduit une phase d’optimisation des chemins construits afin d’éliminer les boucles et une approche adaptative gérant les transmissions simultanées des différents trafics.Par la suite, nous nous sommes orientés vers la tolérance aux pannes, pour assurer la fiabilité des données transmises ainsi que la connectivité du réseau. A cet effet, nous avons modélisé le nombre des paquets perdus durant la livraison des paquets et proposé deux mécanismes : un curatif pour réparer les défaillances soudaines et un préventif afin d’anticiper l’épuisement des batteries. Les deux mécanismes sont combinés avec une stratégie de basculement dynamique lors de la construction des chemins alternatives.En dernier lieu, nous avons présenté un modèle d’interférence et un troisième mécanisme qui limite les interactions entre les liens adjacents. De plus, nous avons défini également un modèle de perte de chemins dans un environnement multi-paires (source,sink) et nous avons calculé le coefficient de probabilité d’erreurs basée sur une fonction de distance qui sépare les flux de données. Une nouvelle métrique a été ajouté dans la fonction objective, relative à la somme des bruits des nœuds actifs qui interférent sur les nœuds du ForwardingSet du nœud courant.Les résultats obtenus montrent l’efficacité des approches proposées qui ont été étudiées et validées à la fois par simulation et sur un banc d’essai expérimentalMultimedia applications in WSNs convey large data (image, audio and video) that requires high transmission rate and intensive treatment and therefore high energy consumption. Effectively transmit these heterogeneous flows, while ensuring their reliability and guaranteeing QoS requirements, with the limited resources available, especially in critical contexts, remains an open scientific problem. That is why, in this thesis, we are interested in aspects related to : routing, fault tolerance and interference management in WMSNs.Given the very low number of routing protocols, that have approached the experimental phase and still less those who approached it during data transmission in real time, we developed in this context, a geographic routing protocol baptised GNMF (Geographic Non-interfering Multipath Fault-tolerant),First, we improved node's selection mode used by the greedy-forwarding, to deal with local minimum problem, where a multi-criteria objective function (distance, energy and reception power) related to next-hop choice has been defined. Then, we introduced an optimization phase of built paths to eliminate loops and an adaptive approach to manage simultaneous traffic transmissions.After that, we oriented towards fault tolerance, to ensure transmitted data reliability and network connectivity. To this end, we modeled the number of lost packets during package delivery and proposed two mechanisms. The curative is used when sudden failures occurs and the preventive to anticipate batteries depletion. Both are combined with a dynamic failover strategy during alternative paths construction.Finally, we presented an interference model and a third mechanism that limits interactions between adjacent links. In addition, we also defined a path loss model in a multipairs environment (source, sink) and computed the error probability coefficient based on a distance function that separates the data flows. A new metric has been added in the objective function, related to noise sum of the active nodes that interferes on forwarding set nodes of the current node.Obtained results show the effectiveness of the proposed approaches that have been studied and validated both by simulation and on an experimental testbed
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Capellano, Vittorio. "Apport des traitements spatiaux-temporels pour les transmissions numériques en présence de trajets multiples. Application a l'acoustique sous-marine." Grenoble INPG, 1998. http://www.theses.fr/1998INPG0047.
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Bouatit, Mohamed Nacer. "Optimisation du routage, tolérance aux pannes et gestion de l'énergie et de l'interférence pour la transmission des flux multimédia temps réel dans les réseaux de capteur sans fil." Electronic Thesis or Diss., Paris, CNAM, 2018. http://www.theses.fr/2018CNAM1188.
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Les applications multimédias, dans les réseaux de capteurs sans fil, véhiculent des données volumineuses, qui nécessitent un taux de transmission élevé et un traitement intensif et par conséquent une consommation d'énergie importante. Transmettre efficacement ces flux hétérogènes, tout en assurant leur fiabilité et garantir les exigences de QoS, avec les ressources limitées disponibles, en particulier dans les contextes critiques, demeure un verrou scientifique ouvert. C’est pourquoi, dans le cadre de cette thèse, nous nous sommes intéressés aux aspects liés : au routage, à la tolérance aux pannes et à la gestion des interférences dans les RCMSF.Compte tenu, du très faible nombre de protocoles de routage, qui ont approché la phase expérimentale et encore moins ceux qui l’ont abordé pendant la transmission des données en temps réel, nous avons développé dans ce contexte, un protocole routage géographique baptisé GNMFT (Geographic Non-interfering Multipath Fault-tolerant),En premier lieu, nous avons amélioré le mode de sélection des nœuds, utilisé par le transfert glouton, pour faire face au problème du Minimum-local, où une fonction objective multicritères (distance, énergie et puissance de réception) relative au choix du prochain saut a été définie. Puis, nous avons introduit une phase d’optimisation des chemins construits afin d’éliminer les boucles et une approche adaptative gérant les transmissions simultanées des différents trafics.Par la suite, nous nous sommes orientés vers la tolérance aux pannes, pour assurer la fiabilité des données transmises ainsi que la connectivité du réseau. A cet effet, nous avons modélisé le nombre des paquets perdus durant la livraison des paquets et proposé deux mécanismes : un curatif pour réparer les défaillances soudaines et un préventif afin d’anticiper l’épuisement des batteries. Les deux mécanismes sont combinés avec une stratégie de basculement dynamique lors de la construction des chemins alternatives.En dernier lieu, nous avons présenté un modèle d’interférence et un troisième mécanisme qui limite les interactions entre les liens adjacents. De plus, nous avons défini également un modèle de perte de chemins dans un environnement multi-paires (source,sink) et nous avons calculé le coefficient de probabilité d’erreurs basée sur une fonction de distance qui sépare les flux de données. Une nouvelle métrique a été ajouté dans la fonction objective, relative à la somme des bruits des nœuds actifs qui interférent sur les nœuds du ForwardingSet du nœud courant.Les résultats obtenus montrent l’efficacité des approches proposées qui ont été étudiées et validées à la fois par simulation et sur un banc d’essai expérimentalMultimedia applications in WSNs convey large data (image, audio and video) that requires high transmission rate and intensive treatment and therefore high energy consumption. Effectively transmit these heterogeneous flows, while ensuring their reliability and guaranteeing QoS requirements, with the limited resources available, especially in critical contexts, remains an open scientific problem. That is why, in this thesis, we are interested in aspects related to : routing, fault tolerance and interference management in WMSNs.Given the very low number of routing protocols, that have approached the experimental phase and still less those who approached it during data transmission in real time, we developed in this context, a geographic routing protocol baptised GNMF (Geographic Non-interfering Multipath Fault-tolerant),First, we improved node's selection mode used by the greedy-forwarding, to deal with local minimum problem, where a multi-criteria objective function (distance, energy and reception power) related to next-hop choice has been defined. Then, we introduced an optimization phase of built paths to eliminate loops and an adaptive approach to manage simultaneous traffic transmissions.After that, we oriented towards fault tolerance, to ensure transmitted data reliability and network connectivity. To this end, we modeled the number of lost packets during package delivery and proposed two mechanisms. The curative is used when sudden failures occurs and the preventive to anticipate batteries depletion. Both are combined with a dynamic failover strategy during alternative paths construction.Finally, we presented an interference model and a third mechanism that limits interactions between adjacent links. In addition, we also defined a path loss model in a multipairs environment (source, sink) and computed the error probability coefficient based on a distance function that separates the data flows. A new metric has been added in the objective function, related to noise sum of the active nodes that interferes on forwarding set nodes of the current node.Obtained results show the effectiveness of the proposed approaches that have been studied and validated both by simulation and on an experimental testbed
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Zhao, Xia. "Transmission scheduling for routing paths and multipaths in cognitive radio mesh networks." Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/zhao/ZhaoX0510.pdf.
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Nodes in a cognitive radio mesh network may select from a set of available channels to use provided they do not interfere with primary users. This ability can improve overall network performance but introduces the question of how best to use these channels. This project addresses the following specific problem: given a routing path P, choose which channels each link in P should use and their transmission schedule so as to maximize the end-to-end data flow rate (throughput) supported by the entire path. This problem is relevant to applications such as streaming video or data where a connection may be long lasting and require a high constant throughput. The problem is hard due to the presence of both intra-flow and inter-flow interference. We have developed a new constant-factor approximation algorithm for this problem. If certain conditions on the path are met, the performance guarantee is 1/4 of optimal. It has been shown by simulation results that the end-to-end throughput given by the proposed algorithm is often within 90% or better of optimal.
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Barnett, Barry Stanley. "Full motion multiparty videoconferencing using motion compensated visual pattern image sequence coding /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Franek, Lešek. "Vícevodičový model komunikace po venkovním elektrickém vedení." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-256566.
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PLC - power line communication is not new. It has been known for many years. But It never be used in massive scale. There were only sporadic applications, for example ripple control system HDO used in the Czechoslovakia. PLC currently experiencing a renaissance thanks to the advent of Smart Grid. PLC offering relatively low bit rates and relatively unreliable transmission, but these disadvantages compensates very low costs to build a communication infrastructure and it offers specific functionalities for Smart Grid. The question is whether the declared parameters will be met in the real world. This thesis tries to find an answer.
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Yu, Shih-Chin, and 余仕錦. "SIMULATION OF WIRELESS DIGITAL TRANSMISSION IN MULTIPATH CHANNEL." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/69589692611329172084.
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碩士大同工學院
電機工程研究所
81
In this thesis we present the simulation methodology and the prediction of average bit error rateo wireless digital transmission system in multipath fading channel model. For considering wiresless digital transmission problem there may be more than one path from transmitter to receiver. Associated with each path is a propagation delay and a attenuation factor. Both the propagation delays and attenuation factors are time-variant as a result of change in the structure of the medium. Therefore the characterization of the multipath channel serves as a model for signal transmission is very important. We establish multipaht channel models, all these channel models are described under each constraints and assumptions. As demand grows for wireless digital communication systems, the acurate prediction of average bit error rate for different modulation schemes will become increasingly important in system design. We present the methodology and implementation of average BER simulation and a step-by-step approach is used to verify the basic ideal and channel models.
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HUNG, CHENG-FENG, and 洪晟峯. "Study on Improvement Transmission Performance and Reliability through multipath transmission in Software Defined Networks." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/bftd3r.
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碩士國立金門大學
理工學院資訊科技與應用碩士班
107
Industry 4.0 is booming all over the world. In the network industry, in order to provide users with good network services by connecting devices to the Internet, the transmission performance and reliability of the network have been paid more and more attention. Single-path transmission is often limited by network bandwidth limitations, network emergencies... Such factors as congestion or packet loss, if the packet transmission can be divided equally, then the network transmission needs can be satisfied. In this study, we propose two traffic diversion schemes, using Stochastic Switching OpenFlow Switch and P4 Switch to distribute traffic, data flows are distributed by multipath transmission, so as to improve network transmission performance. At the same time, we adopt Fast Failover mechanism of OpenFlow in the two schemes respectively to solve the sudden failure of network transmission and still provide users with good services to improve the reliability of the network. In this study, a topology is built in the software-defined network (SDN) environment. By changing the first Switch of the topology, including Stochastic Switch and P4 Switch, the packets of the data flow are designed to be diverted by the traffic flow, so as to reduce the probability of network congestion, packet loss and failure to transmit in case of network sudden failure. The simulated environment of the experiment was Mininet, which was used to evaluate and test our proposed transmission scheme. Mininet is a network simulator that simulates virtual hosts, switches, routers and controllers... And set up network topology. Experimental results show that two proposed scheme has significantly improved the network transmission performance and reliability, and provide better transmission quality for users.
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CHIANG, YI-ROU, and 江依柔. "A Multipath Transmission Scheme for the Improvement of Throughput over SDN." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/buy757.
Full textAbstract:
碩士國立金門大學
理工學院資訊科技與應用碩士班
106
Nowadays, the demand for data transmission is ever increasing with the increase of network applications. Therefore, how to enhance the performance of data transmission is an issue worthy of in-depth discussion. The throughput of single-path transmission schemes might be throttled by a congested link of its path. In contrast, multipath transmission schemes can utilize the bandwidth resource of several disjoint paths to increase the throughput. In this paper, we proposed a multipath transmission scheme to equally balance the traffic of a flow over the disjoint paths designated by the Software Defined Network (SDN) controller, which is able to learn the topology of the network and discover multiple transmission paths. Simulations were conducted with Mininet to evaluate our proposed transmission scheme. In comparison with the traditional single-path transmission scheme, which always adopts the shortest path, experimental results show that our proposed scheme achieves a significant improvement on performance in terms of transmission throughput.
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Ou, Shih-Hao, and 歐士豪. "Out-of-Order Transmission Enabled Congestion and Scheduling Control for Multipath TCP." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/34997220427307146017.
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碩士國立中央大學
通訊工程學系
104
With development of wireless communication technologies, mobile devices are commonly equipped with multiple network interfaces and ready to adopt emerging transport layer protocols such as multipath TCP (MPTCP). The protocol is specifically useful for Internet of Things streaming applications with critical latency and bandwidth demands. To achieve full potential of MPTCP, major challenges on congestion control, fairness, and path scheduling are identified and draw considerable research attention. In this paper, we propose a joint congestion control and scheduling algorithm allowing out-of-order transmission as an overall solution. It is achieved by adaptive window coupling, congestion discrimination, and out-of-order transmission enabled scheduling. The algorithm is implemented in the Linux kernel for real-world experiments. Favorable results are obtained in minumum topology and both shared or distinct bottleneck scenarios.
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Zinner, Thomas. "Performance Modeling of QoE-Aware Multipath Video Transmission in the Future Internet." Doctoral thesis, 2012. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-72324.
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Internet applications are becoming more and more flexible to support diverge user demands and network conditions. This is reflected by technical concepts, which provide new adaptation mechanisms to allow fine grained adjustment of the application quality and the corresponding bandwidth requirements. For the case of video streaming, the scalable video codec H.264/SVC allows the flexible adaptation of frame rate, video resolution and image quality with respect to the available network resources. In order to guarantee a good user-perceived quality (Quality of Experience, QoE) it is necessary to adjust and optimize the video quality accurately. But not only have the applications of the current Internet changed. Within network and transport, new technologies evolved during the last years providing a more flexible and efficient usage of data transport and network resources. One of the most promising technologies is Network Virtualization (NV) which is seen as an enabler to overcome the ossification of the Internet stack. It provides means to simultaneously operate multiple logical networks which allow for example application-specific addressing, naming and routing, or their individual resource management. New transport mechanisms like multipath transmission on the network and transport layer aim at an efficient usage of available transport resources. However, the simultaneous transmission of data via heterogeneous transport paths and communication technologies inevitably introduces packet reordering. Additional mechanisms and buffers are required to restore the correct packet order and thus to prevent a disturbance of the data transport. A proper buffer dimensioning as well as the classification of the impact of varying path characteristics like bandwidth and delay require appropriate evaluation methods. Additionally, for a path selection mechanism real time evaluation mechanisms are needed. A better application-network interaction and the corresponding exchange of information enable an efficient adaptation of the application to the network conditions and vice versa. This PhD thesis analyzes a video streaming architecture utilizing multipath transmission and scalable video coding and develops the following optimization possibilities and results: Analysis and dimensioning methods for multipath transmission, quantification of the adaptation possibilities to the current network conditions with respect to the QoE for H.264/SVC, and evaluation and optimization of a future video streaming architecture, which allows a better interaction of application and networkDie Applikationen im Internet passen sich immer besser an unterschiedliche Anforderungen der Nutzer und variierende Netzwerkbedingungen an. Neue Mechanismen ermöglichen die zielgerichtete Anpassung der Anwendungsqualität und damit der benötigten Bandbreite. Im Falle von Videostreaming ermöglicht der skalierbare Videocodec H.264/SVC, die flexible Veränderung der Bildwiederholungsrate, der Auflösung des Videos und der Bildqualität an die vorhandenen Ressourcen im Netzwerk. Um eine gute vom Nutzer erfahrene Dienstgüte (Quality of Experience, QoE) zu garantieren, muss die Videoqualität richtig angepasst und optimiert werden. Aber nicht nur die Anwendungen des heutigen Internets haben sich verändert. Gerade in den letzten Jahren entstanden neue Netzwerk- und Transporttechnologien, welche eine flexiblere und effizientere Nutzung der Kommunikationsnetze erlauben. Eine dieser Techniken ist die Virtualisierung von Netzwerken. Sie erlaubt es auf einem gemeinsamen physikalischen Netz verschiedene logische Netze zu betreiben, die zum Beispiel Anwendungs-abhängige Adressierung unterstützen, eigene Namensgebung erlauben oder ein individuelles Ressourcen Management ermöglichen. Neuartige Transportmechanismen wie Mehrpfadübertragung auf Netzwerk- und Transportebene des ISO/OSI Stacks streben eine effiziente Ausnutzung der zur Verfügung stehenden Übertragungsmöglichkeiten an. Doch die simultane Übertragung von Daten über heterogene Kommunikationspfade und –technologien führt unausweichlich zu einer Veränderung der Reihenfolge, in der die Pakete ankommen. Es werden zusätzliche Mechanismen und Puffer benötigt, um die ursprüngliche Paketreihenfolge wieder herzustellen und so einen störenden Einfluss auf den Datentransport zu verhindern. Die richtige Dimensionierung dieser Puffer sowie die Klassifizierung des Einflusses von variierenden Pfadparametern wie Bandbreite und Verzögerungen setzen passende Evaluierungsmethoden voraus. Darüber hinaus werden für die Auswahl von geeigneten Pfaden aus einer Menge vorhandener Pfade echtzeitfähige Bewertungsmechanismen benötigt. Eine bessere Interaktion zwischen Applikationen und Netzwerk und der damit verbundene Informationsaustausch ermöglicht die effiziente Anpassung der Applikationsqualität an das Netzwerk und umgekehrt. Diese Doktorarbeit analysiert eine auf Mehrpfadübertragung und skalierbarer Videokodierung basierende Videostreaming Architektur und erarbeitet die folgenden Optimierungsmöglichkeiten und Auswertungen: Analyse- und Dimensionierungsmethoden für Mehrpfadübertragung, Quantifizierung der Anpassungsmöglichkeiten von SVC an das Netzwerk unter Berücksichtigung der QoE und Evaluierung und Optimierung einer zukünftigen Videostreaming Architektur, welche eine stärkere Interaktion zwischen Applikation und Netzwerk ermöglicht
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TING, LU-CHUNG, and 丁律中. "Performance Analysis on Multipath Transmission Using Analytic Hierarchy Process in Software Defined Networks." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/e688ca.
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碩士國立臺北教育大學
資訊科學系碩士班
105
Due to the rapid advancement of internet and multimedia technology, many new multimedia streaming applications and services have been developed. These services make a substantial increase in bandwidth demand, and hence a strategy for network planning and control is also increasingly important. Software defined network (SDN) is a new networking paradigm which separates and abstracts data plane and forwarding plane in a network. Network intelligence is logically centralized in the controller layer and abstracted from the underlying physical network. SDN results in more efficient network management, more flexibility in response to demands and faster innovation. In order to provide better multimedia transmission service, some people use QoS Routing and Multipath Routing to improve performance of multimedia transmission. However, these methods must conform some restrictions in order to achieve the expected goals. Generally speaking, these methods are not easy be used. In this study, we developed a multipath transmission mechanism for single data flow in software defined networks. Firstly, we use LARAC algorithm to find the best transmission paths that conform the required restrictions. Secondly, we use Analytic Hierarchy Process to set multipath transmission weights based on Open Flow Stochastic Switching. Experimental results show the proposed mechanism can provide higher bandwidth, reduce packet loss rate, and decrease transmission delay in comparison with single path transmission. Therefore, the proposed mechanism can be effectively applied in the software defined networks for multimedia transmission.
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Wu, Shih-Jen, and 吳世仁. "An Efficient Scheduling Strategy for Multipath Packet Transmission in Ad Hoc Wireless Networks." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/23026270181766564270.
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碩士長庚大學
電機工程研究所
91
Ad Hoc wireless networks are formed by a cluster of mobile hosts, without the infrastructure of base stations. To deal with the dynamic changing topology of a Ad Hoc wireless networks, many routing protocols have been proposed. These protocols use single path to transmit data which is not only poor resource utilization but also bad toleration with link breakage or traffic congestion. Multipath routings can overcome these problems. In addition, it can provide load balancing by distributing traffic among a set of paths. Therefore, some researchers propose multipath routing protocols but they assume only one path is used as primary route, the others as backup routes. In this proposal, we consider multipath parallel transmission. We use the stability of individual links as the route selection criterion. It ensures that the route is established strong connection. We propose a new approach called Path Transmission Time (PTT) for multipath routing in Ad Hoc wireless networks. PTT is the duration that source transmits a data to destination successfully. It is because that the PTT of each path is different, so if source randomly use a path chosen from multipath to transmit data, maybe the PTT of the path is very large that will result data transmission inefficient. Our work focuses on how to choose an adaptive path from multipath to transmit each data. The objects of the project are to distribute the traffic load and to increase the end to end throughput.
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Chen, Wen-Yi, and 陳文毅. "Adaptive Multipath Transmission Mechanism with P4 Switches and Traffic Monitoring in Software Defined Networks." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/33k36y.
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碩士國立臺北教育大學
資訊科學系碩士班
107
Each traditional network switch can resolve the packet by itself, but this way cannot dynamically consider the overall network status into the selection path, so it is still possible to stream the data into the blocked link. The SDN support flexible scheduling and programmable control of network resources. It separates the Control Plane from the Data Plane. The controller is responsible for parsing and processing the packets. When the Data Plane receives the custom rules of the Control Plane, Data Plane forwarding packets according to the output port specified by its rules. It is know from the research of many scholars that multi-path transmission can improve the network transmission efficiency. Although OpenFlow can also implement packet-oriented multipath transmission, but OpenFlow is used by the controller to set the processing rules of the switch to the packet, when the controller fails and cannot be connected with the switch, the multipath transmission will be invalid. This research based on the P4 architecture and used the approach of placing the control layer in the switch that could be avoids the aforementioned problem. When the packet enters the P4 switch, the P4 Register, P4 Meter, or P4 Counter accesses it... The various states of the packets check the table in a stylized control manner and execute the corresponding action, and the random function in the actions determines which output port the packet should be send. In the same time, use the P4 simple_switch_CLI to support the cmd module written in python language, to define the probability of sending packets to different output ports. So that the P4 switch in the network can offload data packets and transmit them through different paths with different chances. At the same time, use the MRI tool belonging to the SDN Data Plane to collect the state information of the network topology. When the switch finds that one of the output paths is congestion, which can be programmable control the packets transmission to the specified output port. Simulation results showed that the proposed multipath transmission mechanism in addition to avoiding the problem of data transmission interruption due to single transmission path failure, it can improve transmission efficiency, reliability, and network throughput.
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Lee, Ei-Kwei, and 李奕逵. "Multipath Simulator for HFC Systems and Baseband Processing Circuit Implementation for 64-QAM Signal Transmission." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/40281235163598426547.
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碩士國立交通大學
光電工程研究所
84
In the thesis we implement the multipath simulator for HFC systems ,including digital attenuator , digital power combiner , and find the para-meters by means of optimization. We also implement 64-QAM baseband processingcircuits including scrambler , Reed-Solomon code , Convolutional Interleaving, and the related circuits of Reed-Solomon Code including frequency synthesizer, (de-)Multiplexer,data compression , data retraction , frame synchronization... etc
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Li, Yi-Da, and 李奕達. "Multipath Simulator for HFC Systems and Baseband Processing Circuit Implementation for 64-QAM Signal Transmission." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/85093931924513746999.
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CHANG, YI-CHIAO, and 張鉯喬. "A Method for Improving QoS of Multimedia Application Based on Distributed Storage and Multipath Transmission." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/82yf68.
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碩士醒吾科技大學
資訊科技應用系
107
With the rapid growth of science and technology, IPTV (Internet Protocol Television) become more and more popular. IPTV is different from traditional cable in general, the content store in the cloud server. IPTV provide channel content via IP broadband Internet to users. In order to make IPTV more popular, users’ satisfaction is a very important issue. A lot of researches indicate IPTV QoS is the channel switching time, that is, when a user change the current channel until the next channel display. This paper presents IPTV-N architecture which the IPTV architecture combined with fog, in order to improve the effectiveness of IPTV and users’ satisfaction. In addition to presenting IPTV-N architecture, we also propose a method call IPTV-f. IPTV-f is a algorithm to select the best fog end servers to deliver channel content to the user. Beside, this research also proposes a multi-path transmission scheduling which is suitable for transmitting multimedia application, As the results, it could expect to get the most important frames at the receiver before deadline time to increase the playback quality. This paper use NS2 to build a simulation environment. The simulation results show that IPTV-f selection method is superior to the others, less 44% than IPTV-c and less 52.6% than IPTV-r. The future work can focus on IPTV-N architecture, such as improved queuing methods or join prediction based techniques to reduce channel switching time and improve users’ satisfaction.
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Lin, Yung-Jeng, and 林永正. "Impact of Multipath Fading on the Quality of Signal Transmission in High Speed Railway Environments." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/78150295175371650660.
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Teal, Paul D. "Real Time Characterisation of the Mobile Multipath Channel." Phd thesis, 2001. http://hdl.handle.net/1885/48207.
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In this thesis a new approach for characterisation of digital mobile radio channels is
investigated. The new approach is based on recognition of the fact that while the
fading which is characteristic of the mobile radio channel is very rapid, the processes
underlying this fading may vary much more slowly. The comparative stability of these
underlying processes has not been exploited in system designs to date. ¶
Channel models are proposed which take account of the stability of the channel.
Estimators for the parameters of the models are proposed, and their performance is
analysed theoretically and by simulation and measurement. ¶
Bounds are derived for the extent to which the mobile channel can be predicted,
and the critical factors which define these bounds are identified. ¶
Two main applications arise for these channel models. The first is the possibility
of prediction of the overall system performance. This may be used to avoid channel
fading (for instance by change of frequency), or compensate for it (by change of the
signal rate or by power control). The second application is in channel equalisation. An
equaliser based on a model which has parameters varying only very slowly can offer
improved performance especially in the case of channels which appear to be varying so
rapidly that the convergence rate of an equaliser based on the conventional model is
not adequate. ¶
The first of these applications is explored, and a relationship is derived between the
channel impulse response and the performance of a broadband system.
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Liang-SyunHuang and 黃亮勳. "Equalization for Single-Carrier Block Transmission in Fast-Varying Multipath Fading Channels Using Iterative Block Decision Feedback." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/03347947088553459868.
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碩士國立成功大學
電腦與通信工程研究所
101
In doubly-selective channels, single-carrier block transmission suffers from not only inter-symbol interference (ISI) but also virtual inter-carrier interference (virtual ICI) because channel variation within a transmitted block can no longer be neglected. In this case, the detection performance deteriorates considerably if the equalizer does not account for time selectivity. In the literature, equalization algorithms that cope with time-varying channels include time-domain minimum mean squared error linear equalizer (MMSE-LE) and minimum mean squared error successive interference cancellation (MMSE-SIC). The latter has a better error-rate performance, but the former has a much lower complexity. In hopes of achieving a better trade-off between performance and complexity, we extend the low-complexity iterative block decision feedback equalizer (IBDFE), originally designed for frequency-selective channels only, to doubly-selective channels. To deal with the virtual ICI, the matrix feedback filter is adopted. We assume correct decisions to derive the equalizer coefficients; however, we feed back the actual decisions in simulations. Simulation results show that the proposed algorithm achieves a better performance than MMSE-LE with only a slight increase in complexity. Compared with MMSE-SIC, the proposed algorithm has a poorer performance, but a much lower complexity.
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Sahasranand, K. R. "Robust Nonparametric Sequential Distributed Spectrum Sensing under EMI and Fading." Thesis, 2015. http://etd.iisc.ac.in/handle/2005/3834.
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Opportunistic use of unused spectrum could efficiently be carried out using the paradigm
of Cognitive Radio (CR). A spectrum remains idle when the primary user (licensee) is
not using it. The secondary nodes detect this spectral hole quickly and make use of it
for data transmission during this interval and stop transmitting once the primary starts
transmitting. Detection of spectral holes by the secondary is called spectrum sensing in
the CR scenario. Spectrum Sensing is formulated as a hypothesis testing problem wherein under H0 the spectrum is free and under H1, occupied. The samples will have different probability distributions, P0 and P1, under H0 and H1 respectively.
In the first part of the thesis, a new algorithm - entropy test is presented, which performs better than the available algorithms when P0 is known but not P1. This is extended
to a distributed setting as well, in which different secondary nodes collect samples independently and send their decisions to a Fusion Centre (FC) over a noisy MAC which then makes the final decision. The asymptotic optimality of the algorithm is also shown.
In the second part, the spectrum sensing problem under impediments such as fading,
electromagnetic interference and outliers is tackled. Here the detector does not possess
full knowledge of either P0 or P1. This is a more general and practically relevant setting.
It is found that a recently developed algorithm (which we call random walk test) under suitable modifications works well. The performance of the algorithm theoretically and via simulations is shown. The same algorithm is extended to the distributed setting as above.
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Sahasranand, K. R. "Robust Nonparametric Sequential Distributed Spectrum Sensing under EMI and Fading." Thesis, 2015. http://etd.iisc.ernet.in/2005/3834.
Full textAbstract:
Opportunistic use of unused spectrum could efficiently be carried out using the paradigm
of Cognitive Radio (CR). A spectrum remains idle when the primary user (licensee) is
not using it. The secondary nodes detect this spectral hole quickly and make use of it
for data transmission during this interval and stop transmitting once the primary starts
transmitting. Detection of spectral holes by the secondary is called spectrum sensing in
the CR scenario. Spectrum Sensing is formulated as a hypothesis testing problem wherein under H0 the spectrum is free and under H1, occupied. The samples will have different probability distributions, P0 and P1, under H0 and H1 respectively.
In the first part of the thesis, a new algorithm - entropy test is presented, which performs better than the available algorithms when P0 is known but not P1. This is extended
to a distributed setting as well, in which different secondary nodes collect samples independently and send their decisions to a Fusion Centre (FC) over a noisy MAC which then makes the final decision. The asymptotic optimality of the algorithm is also shown.
In the second part, the spectrum sensing problem under impediments such as fading,
electromagnetic interference and outliers is tackled. Here the detector does not possess
full knowledge of either P0 or P1. This is a more general and practically relevant setting.
It is found that a recently developed algorithm (which we call random walk test) under suitable modifications works well. The performance of the algorithm theoretically and via simulations is shown. The same algorithm is extended to the distributed setting as above.
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Schoeman, Johan P. "An optimised QPSK-based receiver structure for possibly sparse data transmission over narrowband and wideband communication systems." Diss., 2010. http://hdl.handle.net/2263/27512.
Full textAbstract:
In this dissertation an in-depth study was conducted into the design, implementation and evaluation of a QPSK-based receiver structure for application in a UMTS WCDMA environment. The novelty of this work lies with the specific receiver architecture aimed to optimise the BER performance when possibly sparse data streams are transmitted. This scenario is a real possibility according to Verd´u et al [1] and Hagenauer et al [2–6]. A novel receiver structure was conceptualised, developed and evaluated in both narrowband and wideband scenarios, where it was found to outperform conventional receivers when a sparse data stream is transmitted. In order to reach the main conclusions of this study, it was necessary to develop a realistic simulation platform. The developed platform is capable of simulating a communication system meeting the physical layer requirements of the UMTS WCDMA standard. The platform can also perform narrowband simulations. A flexible channel emulator was developed that may be configured to simulate AWGN channel conditions, frequency non-selective fading (either Rayleigh or Rician with a configurable LOS component and Doppler spread), or a full multipath scenario where each path has a configurable LOS component, Doppler spread, path gain and path delay. It is therefore possible to even simulate a complex, yet realistic, COST207-TU channel model. The platform is also capable of simulating MUI. Each interfering user has a unique and independent multipath fading channel, while sharing the same bandwidth. Finally, the entire platform executes all simulations in baseband for improved simulation times. The research outputs of this work are summarised below: - A parameter, the sparseness measure, was defined in order to quantify the level by which a data stream differs from an equiprobable data stream.
- A novel source model was proposed and developed to simulate data streams with a specified amount of sparseness.
- An introductory investigation was undertaken to determine the effect of simple FEC techniques on the sparseness of an encoded data stream.
- Novel receiver structures for both narrowband and wideband systems were proposed, developed and evaluated for systems where possibly sparse data streams may be transmitted.
- Analytic expressions were derived to take the effect of sparseness into account in communication systems, including expressions for the joint PDF of a BPSK branch, the optimal decision region of a detector in AWGN conditions as well as the BER performance of a communication system employing the proposed optimal receiver in both AWGN channel conditions as well as in flat fading channel conditions.
- Numerous BER performance curves were obtained comparing the proposed receiver structure with conventional receivers in a variety of channel conditions, including AWGN, frequency non-selective fading and a multipath COST207-TU channel environment, as well as the effect of MUI
- ’n Parameter, die ylheidsmaatstaf, is gedefin¨ýeer om dit moontlik te maak om die vlak waarmee die ylheid van ’n datastroom verskil van ’n ewekansige stroom te versyfer.
- ’n Nuwe bronmodel is voorgestel en ontwikkel om datastrome met ’n spesifieke ylheid te emuleer.
- ’n Inleidende ondersoek is onderneem om vas te stel wat die effek van VFK tegnieke op die ylheid van ’n enkodeerde datastroom is.
- Nuwe ontvanger strukture is voorgestel, ontwikkel en evalueer vir beide noueband en wyeband stelsels waar yl datastrome moontlik versend kan word.
- Analitiese uitdrukkings is afgelei om die effek van ylheid in ag te neem in kommunikasie stelsels. Uitdrukkings vir onder andere die gedeelte WDF van ’n BFVK tak, die optimale beslissingspunt van ’n detektor in SWGR toestande, sowel as die BFT werksverrigting van ’n kommunikasie stelsel wat van die voorgestelde optimale ontvangers gebruik maak, hetsy in SWGR of in plat duinende kanaal toestande.
- Talryke BFT werksverrigting krommes is verkry wat die voorgestelde ontvanger struktuur vergelyk met die konvensionele ontvangers in ’n verskeidenheid kanaal toestande, insluitend SWGR, plat duinende kanale en ’n veelvuldige pad COST207-TU kanaal omgewing, sowel as in die teenwoordigheid van VGS.
Electrical, Electronic and Computer Engineering
unrestricted
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Feteiha, Mohamed. "On the Performance Analysis of Cooperative Vehicular Communication." Thesis, 2012. http://hdl.handle.net/10012/6544.
Full textAbstract:
Vehicular networking is envisioned to be a key technology area for significant growth in the coming years. Although the expectations for this emerging technology are set very high, many practical aspects remain still unsolved for a vast deployment of vehicular networks. This dissertation addresses the enabling physical layer techniques to meet the challenges in vehicular networks operating in mobile wireless environments. Considering the infrastructure-less nature of vehicular networks, we envision cooperative diversity well positioned to meet the demanding requirements of vehicular networks with their underlying
distributed structure.
Cooperative diversity has been proposed as a powerful means to enhance the performance of high-rate communications over wireless fading channels. It realizes spatial diversity advantages in a distributed manner where a node uses others antennas to relay its message creating a virtual antenna array. Although cooperative diversity has garnered much attention recently, it has not yet been fully explored in the context of vehicular networks considering the unique characteristics of vehicular networks, this dissertation provides an error performance analysis study of cooperative transmission schemes for various deployment and traffic scenarios.
In the first part of this dissertation, we investigate the performance of a cooperative vehicle-to-vehicle (V2V) system with amplify-and-forward relaying for typical traffic scenarios under city/urban settings and a highway area. We derive pairwise error probability (PEP) expressions and demonstrate the achievable diversity gains. The effect of imperfect channel state information (CSI) is also studied through an asymptotical PEP analysis. We present Monte-Carlo simulations to confirm the analytical derivations and present the error rate performance of the vehicular scheme with perfect and imperfect-CSI.
In the second part, we consider road-to-vehicle (R2V) communications in which roadside access points use cooperating vehicles as relaying terminals. Under the assumption of decode-and-forward relaying, we derive PEP expressions for single-relay and multi-relay scenarios.
In the third part, we consider a cooperative multi-hop V2V system in which direct transmission is not possible and investigate its performance through the PEP derivation
and diversity gain analysis. Monte-Carlo simulations are further provided to con firm the analytical derivations and provide insight into the error rate performance improvement.
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"Routing and bandwidth management for multiparty videoconferencing." 1998. http://library.cuhk.edu.hk/record=b6073116.
Full textAbstract:
by Feng Gang.Thesis (Ph.D.)--Chinese University of Hong Kong, 1998.
Includes bibliographical references (p. 169-181).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.
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Μαλακάτας, Κωνσταντίνος-Επαμεινώνδας. "Μελέτη και προσδιορισμός του συντελεστή Κ της κατανομής Rice για ασύρματα κανάλια σε εσωτερικούς και εξωτερικούς χώρους." Thesis, 2014. http://hdl.handle.net/10889/8044.
Full textAbstract:
Σκοπός της παρούσας διπλωματικής εργασίας είναι η μελέτη και ο προσδιορισμός, θεωρητικός και πειραματικός, του συντελεστή Κ της Rician κατανομής σε ένα κανάλι στα 2.4 GHz. Η κατανομή Rice χρησιμοποιείται για την περιγραφή του πλάτους του λαμβανόμενου σήματος σε ένα κανάλι μετάδοσης με ισχυρή επίδραση οπτικής επαφής (Line-of-Sight) μεταξύ κεραίας πομπού και δέκτη. Ο συντελεστής Κ Rice εκφράζει τον λόγο της συνεισφοράς της ισχύος της απευθείας συνιστώσας του σήματος ως προς την συνολική λαμβανόμενη ισχύ λόγω φαινομένων διάχυσης. Χρησιμοποιείται για τον χαρακτηρισμό του καναλιού καθώς και τον υπολογισμό του BER (bit-error-ratio) και της πλέον σημαντικής παραμέτρου των τηλεπικοινωνιών SNR (Signal-to-Noise-Ratio), δηλαδή του λόγου σήματος προς θόρυβο.
Στο 1ο κεφάλαιο αναλύονται και περιγράφονται μερικές από τις σημαντικότερες τεχνολογίες ασυρμάτων δικτύων, από την πρώτη στιγμή της εμφάνισής τους (δίκτυα 1ης και 2ης γενιάς) έως τα πιο σύγχρονα δίκτυα 3ης και 4ης γενιάς, και παρουσιάζονται οι ζώνες συχνοτήτων που καταλαμβάνουν αυτές οι τεχνολογίες στο διαθέσιμο ηλεκτρομαγνητικό φάσμα.
Στο 2ο κεφάλαιο μελετώνται οι 3 βασικότεροι μηχανισμοί διάδοσης του ηλεκτρομαγνητικού κύματος μέσα σε ένα ασύρματο κανάλι (ανάκλαση, περίθλαση, σκέδαση), περιγράφονται οι τύποι των απωλειών που υφίσταται ένα σήμα κατά την μετάδοση του και τα φαινόμενα των διαλείψεων, που παρατηρούνται πολύ έντονα σε ένα κινητό και μεταβαλλόμενο περιβάλλον διάδοσης.
Στο 3ο κεφάλαιο γίνεται περιγραφή του μοντέλου ηλεκτρομαγνητικής μετάδοσης κατά Rice, δηλαδή όταν η απευθείας συνιστώσα του σήματος είναι η ισχυρότερη διαδρομή που ακολουθεί το εκπεμπόμενο σήμα κατά την πορεία του μέχρι τον δέκτη (LoS). Αναλύεται η σημαντικότερη παράμετρος αυτού του τύπου μετάδοσης, δηλαδή ο συντελεστής Κ, και παρουσιάζονται διάφορες μέθοδοι προσδιορισμού του τόσο θεωρητικά όσο και πειραματικά.
Στο 4ο κεφάλαιο παρουσιάζονται τα αποτελέσματα των πειραματικών μας μετρήσεων σε διάφορες τοπολογίες μετάδοσης με LoS για ένα δίκτυο Wi-Fi, δηλαδή για συχνότητα λειτουργίας στα 2.4 GHz. Για κάθε τοπολογία, περιγράφεται πλήρως το περιβάλλον μετάδοσης καθώς και ολόκληρη η διαδικασία εκπόνησης των μετρήσεων (μετρητικά όργανα, απαραίτητο λογισμικό, τυχόν προσεγγίσεις κτλ.).
Τέλος, στο 5ο και τελευταίο κεφάλαιο, παρουσιάζεται μια μέθοδος υπολογισμού του συντελεστή Κ μέσω των μετρήσεων και με τη βοήθεια του μοντέλου ελευθέρου χώρου, που χρησιμοποιείται για τον υπολογισμό των συνολικών απωλειών διαδρομής του σήματος. Τα αποτελέσματα των υπολογισμών χρησιμοποιήθηκαν, με την βοήθεια του Matlab, για την κατασκευή της CDF των τιμών του Κ αλλά και της γραφικής παράστασης της μεταβολής του Κ συναρτήσει της απόστασης. Οι εμπειρικές CDF συγκριθήκαν και προσεγγιστήκαν με γνωστές θεωρητικές CDF, και η συνάρτηση της μεταβολής του Κ με την απόσταση προσεγγίστηκε με όρους Goodness of Fit με την βοήθεια της γενικής μορφής γνωστών συναρτήσεων. Κλείνοντας, στην τελευταία παράγραφο της εργασίας αφήνεται περιθώριο και δίνεται τροφή για μελλοντική εργασία πάνω στην μελέτη και τον προσδιορισμό του συντελεστή Κ της Rice τόσο για εσωτερικούς όσο και για εξωτερικούς χώρους.The main purpose of this thesis, is the analysis and estimation , theoretical and empirical, of the Rician K factor for a wireless channel at 2.4 GHz. The Rician power density function is used to describe the amplitude of the received signal when there is a strong LOS component. The Rician K factor expresses the ratio of the power component due to LOS signal propagation and the received signal power due to diffuse components (reflection, scattering, diffraction etc.). It is commonly used for the channel's characterization and the estimation of BER (bit error rate) and SNR (signal to noise ratio), a very important parameter for telecommunications. In the 1st chapter, some of the most important wireless systems are described, since their very first appearance (1G & 2G networks) until the latest 3rd and 4rth generation systems. We also present the current frequency bands and how they are spread at the given electromagnetic spectrum. In the 2nd chapter, the 3 basic propagation mechanisms (reflection, scattering, diffraction) are studied. In addition, we describe all types of signal attenuation within a wireless channel and the fading phenomena that are so commonly seen in mobile and continuously changing propagation environments. In the 3rd chapter, the Rician model of electromagnetic propagation, where LOS is the strongest path of signal components, is analyzed. The most important parameter of this propagation type, the Rician K factor, is also studied. Therefore, various methods of theoretical and empirical estimation of the K factor are presented. In the 4rth chapter, we include the results of our measurements in various LOS propagation topologies for a Wi-Fi system at 2.4 GHz. For each measurement topology, the propagation environment as well as the entire measurement procedure, are thoroughly described. Lastly, in the 5th and final chapter, a K factor estimation method based on the empirical set of data and the Free Space Model, used for the average path loss calculation, is presented. The results of our measurements via the help of the Matlab software were used in order to plot the CDF of K values as well as the K values versus d (distance) curve. Using curve fitting methods, the empirical CDFs and plots were compared to theoretical ones in terms of Goodness of Fit. In the closing section, possible future research in the aforementioned fields is proposed.