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Savov, Emil I. "Multichannel photonic networks." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7835.
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This thesis presents several alternatives for fibre-optic local and metropolitan area networks. The issues considered are mainly related to the physical layer of the networks, i.e., the topology and the optical communications problems. The following approaches were considered in more detail: photonic switching using spatial light modulators; subcarrier-multiplexing techniques using direct optical detection, and in particular the transmission of 64-QAM signals by optical fibre; and subcarrier-multiplexing techniques combined with coherent optical detection. The spatial light modulator appears to be one of the most promising means for building a large-size (e.g., 1000 $\times$ 1000) optical space switch. The main constraints are the attenuation of the optical signal and the crosstalk between the channels. Other problems such as fan-in and fan-out are also addressed. Theoretical and experimental results are presented on the fibre-optic transmission of microwave 64-QAM signals at 90 Mb/s rate. Two important methods of improving the system performance are discussed and demonstrated: laser reflection-induced intensity noise minimization, and error-correction coding using a self-orthogonal convolutional code. The applicability of this transmission technique to the distribution of digital video services is assessed. The concept of photonic networks which use subcarrier-multiplexing techniques together with coherent optical detection is presented. The different radio and optical modulation formats that can be used are investigated and compared for several system modes of operation. The effects of laser phase noise on the system performance are also addressed. An 8-port homodyne phase-diversity receiver is analyzed theoretically.
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Nordin, N. "Multichannel cross-layer routing for sensor networks." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1566915/.
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Wireless Sensor Networks are ad-hoc networks that consist of sensor nodes that typically use low-power radios to connect to the Internet. The channels used by the low-power radio often suffer from interference from the other devices sharing the same frequency. By using multichannel communication in wireless networks, the effects of interference can be mitigated to enable the network to operate reliably. This thesis investigates an energy efficient multichannel protocol in Wireless Sensor Networks. It presents a new decentralised multichannel tree-building protocol with a centralised controller for ad-hoc sensor networks. The proposed protocol alleviates the effect of interference, which results in improved network efficiency, stability, and link reliability. The protocol detects the channels that suffer interference in real-time and switches the sensor nodes from those channels. It takes into account all available channels and aims to use the spectrum efficiently by transmitting on several channels. In addition to the use of multiple channels, the protocol reconstructs the topology based on the sensor nodes’ residual energy, which can prolong the network lifetime. The sensor nodes’ energy consumption is reduced because of the multichannel protocol. By using the lifetime energy spanning tree algorithm proposed in this thesis, energy consumption can be further improved by balancing the energy load in the network. This solution enables sensor nodes with less residual energy to remain functional in the network. The benefits of the proposed protocol are described in an extensive performance evaluation of different scenarios in this thesis.
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Liew, Soung Chang. "Capacity assignment in non-switching multichannel networks." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14711.
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JAIN, NITIN. "MULTICHANNEL CSMA PROTOCOLS FOR AD HOC NETWORKS." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin995471534.
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Tenneti, Shivaram Venkata. "Channel assignment for throughput improvement in multi-radio wireless mesh networks." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/tenneti/TennetiS1207.pdf.
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Saha, Dola. "Channel allocation using interference detection in multichannel wireless networks." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453577.
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Tall, Hamadoun. "Load balancing in multichannel data collection wireless sensor networks." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC006/document.
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Les Réseaux de Capteurs Sans Fil (RCSF) sont de plus en plus exploités par des applications diverses grâce à leur facilité de déploiement et d’auto-configuration. Les applications de collecte de données qui utilisent les RCSF ont souvent un profil convergecast : l’ensemble des données récoltées par tous les capteurs du réseau sont acheminées vers un puits de collecte, grâce à une communication multi-saut. Pendant l’acheminement des données des nœuds de collecte vers le puits, des goulots d’étranglement sont fréquemment observés, principalement au voisinage du puits. Cela est du à la congestion et au phénomène d’entonnoir couramment observé sur le trafic de données ayant un profile convergecast. Outre un risque accru de collision, cela entraîne le débordement des files d’attente des nœuds concernés conduisant à des pertes de données. Cette perte réduit le taux de livraison au puits entraînant une baisse du débit du réseau. Afin de réduire ces pertes et de permettre un meilleur taux de livraison au puits, le trafic doit être équitablement réparti au niveau de chaque saut pendant l’acheminement. Dans cette thèse, nous avons d’une part proposé S-CoLBA (Single channel Collaborative Load Balancing Algorithm), un protocole mono-canal de routage dynamique avec équilibrage de la charge. Sa métrique de routage est basée sur le délais moyen d’accès au medium radio par nœud. Chaque nœud choisit comme prochain saut à destination du puits, un de ses voisins ayant le délais d’accès le plus court. S-CoLBA intègre également une surveillance permanente des files d’attente des nœuds afin de prévenir la congestion et d’éviter le débordement de ces files. D’autre part, nous avons adapté S-CoLBA pour le rendre utilisable dans un réseau multicanal. Cette version du protocole s’appelle M-CoLBA (pour Mulitchannel CoLBA). M-CoLBA évite la congestion en équilibrant la charge grâce à une répartition du trafic au niveau de chaque saut du réseau. Dans un réseau multicanal, le problème de support de diffusion se pose. M-CoLBA introduit des périodes de synchronisations où tous les nœuds utilisent le même canal pour échanger les informations de routage. Ces périodes de synchronisation contribuent à allonger les délais de bout en bout des paquets. Nous avons ainsi optimisé M-CoLBA en "surchargeant" les acquittements des trames avec les informations de routage ( piggybacking) et les états des files d’attente. Cela évite de passer par des périodes de synchronisation pour diffuser ces informations. Cette version optimisée s’appelle ABORt ( Acknowledgement-Based opportunistic Routing protocol). Dans un cas de trafic de type convergecast, ABORt induit une diversité des routes prises par les données collectées, ce qui est bénéfique à la quantité de données transportées et à la robustesse de la solution. Les contributions ont été évaluées par simulation et expérimentation dans un réseau monocanal et multicanal. Les résultats montrent que nos contributions améliorent le taux de livraison des données au puits, optimisent le délais de bout en bout et réduisent la quantité de trafic de contrôle comparé à des solutions déjà existantesThe popularity of wireless sensor networks (WSNs) is increasing due to their ease ofdeployment and auto-configuration capabilities. They are used in different applica-tion domains including data collection with convergecast scenarios. In convergecast,all data collected in the network is destined to one common node usually called thesink. In case of high carried traffic load and depending on the used routing policy,this many-to-one data collection leads to congestion and queue overflow mainly innodes located near the sink. Congestion and queue overflow reduce delivery ratiothat negatively affects the network efficiency.Wireless sensor nodes are resource constrained devices with limited buffers sizeto store and forward data to the sink. Introducing multichannel communication inWSNs helps to increase the carried traffic load thanks to allowing parallel data trans-mission and reduction of contention and interference. With high traffic load, thenumber of data packets travelling from leaf nodes towards the sink becomes higher.In case the routing scheme does not balance the traffic load, it will be unfairly dis-tributed between forwarding nodes. Thus, nodes that are in part of the routing will beoverloaded while others are less used. Overloaded nodes increase the risk of conges-tion and queue overflow leading to data loss that reduces the throughput. Therefore,we need to couple the routing protocols with traffic load balancing scheme in hightraffic load network scenarios.The goal of this thesis is to propose an efficient routing solution to prevent con-gestion and queue overflow in high data rate convergecast WSNs, in such a way, tooptimize data delivery ratio at the sink node.On the one hand, we proposed a single channel traffic load balancing routingprotocol, named S-CoLBA (Single channel Collaborative Load balancing routing).It relies on data queueing delay metric and best score (according to the value of themetric) next hop neighbors to fairly distribute traffic load in per hop basis in the net-work. Since the carried traffic load increases in multichannel communication, onthe other hand, we adapted our contribution to cope with multichannel WSNs andwe named it as Multichannel CoLBA (M-CoLBA). As broadcasting information isnot straightforward in multichannel, we optimize M-CoLBA to use piggybackingscheme for routing information sharing in the network. This enhanced version iscalled ABORt for Acknowledgement-Based opportunistic Routing protocol and re-lies on ACK frames to share routing information. Doing so helps to optimize dataframe end-to-end delay and to reduce the transmitted beacons in the network. ABORtfairly distributes traffic load in the network and avoids congestion and queue over-flow.We evaluated the performance of our contributions in both simulation using Con-tiki OS Cooja simulator and experiment (only for S-CoLBA) on TelosB motes. Ob-tained results in both simulation and experiment confirm the efficiency of our routingprotocols in term of packet delivery ratio and queue overflow compared to some ex-isting routing protocols in the literature
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Nguyen, Minh Duc. "Application-aware Scheduling in Multichannel Wireless Networks with Power Control." Thesis, KTH, Kommunikationsnät, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-99194.
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Scheduling algorithm is the algorithm to allocate system resources among processes and data flows. Joint channel-assignment and workload-based (CAWS) is a recently developed algorithm for scheduling in the downlink of multi-channel wireless systems, such as OFDM. Compared to well known algorithms, CAWS algorithm has been proved to throughput optimal with flow-level dynamics. In this master thesis project, we design a system that accounts for power control and for the characteristics of common radio channels. We evaluate the efficiency of the algorithm under a diverse set of conditions. We also do analysis of CAWS algorithm under different traffic density.
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TALWAR, SUMEET. "PERFORMANCE EVALUATION OF MULTIPATH ROUTING WITH MULTICHANNEL AD HOC NETWORKS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1054312541.
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Kakumanu, Sandeep. "Component Based Channel Assignment in Single Radio, Multichannel Ad hoc Networks." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19870.
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In this work, we consider the channel assignment problem in single radio multi-channel mobile ad-hoc networks. Specifically, we investigate the granularity of channel assignment decisions that gives the best trade-off in terms of performance and complexity. We present a new granularity for channel assignment that we refer to as component level channel assignment. The strategy is relatively simple, and is characterized by several impressive practical advantages. We also show that the theoretical performance of the component based channel assignment strategy does not lag significantly behind the optimal possible performance, and perhaps more importantly we show that when coupled with its several practical advantages, it significantly outperforms other strategies under most network conditions.
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Luo, Qiuchan. "Delay Sensitive Services In Multichannel Random Access Networks With Selfish Users." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102774.
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Because of the scarcity of spectrum, it is becoming more and more important to use the spectrum efficiently. Dynamic spectrum allocation schemes are proposed to increase the efficiency of spectrum usage. Meanwhile, delay-sensitive services like voice service are still a strong contributor to operator revenues and constitute a significant portion of user demand. Therefore, it is valuable to study whether delay-sensitive services like voice service can be provided in multichannel random access network, in which multiple operators use the unlicensed spectrum and decentralized dynamic spectrum allocation scheme is adopted. In this study, two User Reinforcement Learning schemes are proposed to model the behavior of selfish users in the multichannel random access network. We analyze the performance of these two schemes and compare them with Operator Reinforcement Learning scheme and Operator Non-Reinforcement Learning scheme in terms of delay, jitter, packet loss rate, consecutive packet loss rate, throughput per channel and utility per user. We find that both the "User Reinforcement Learning Non-Retransmission" scheme and the "Operator Reinforcement Learning" scheme can provide a satisfactory quality service under a moderately high load.
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Garkusha, Sergey, Maryna Gogolieva, and Ahmed Hassan Abed. "A mathematical model of channel distribution in multichannel mesh networks 802.11." Thesis, 11-th International Conference THE EXPERIENCE OF DESIGNING AND APPLICATION OF CAD SYSTEMS IN MICROELECTRONICS, 2011. http://dspace.uccu.org.ua/handle/123456789/867.
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This paper focuses on mathematical models of distribution channels in the multi-mesh-networks, the 802.11 standard by which the balancing of mesh-stations on domains conflicts with their territorial remoteness and activity that can improve the performance of multichannel mesh network as a whole
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Keefer, Edward W. (Edward Wesley). "Medial Medulla Networks in Culture: a Multichannel Electrophysiologic and Pharmacological Study." Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc278519/.
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Spontaneously active primary cultures obtained from dissociated embryonic medial medulla tissue were grown on microelectrode arrays for investigating burst patterns and pharmacological responses of respiratory-related neurons. Multichannel burst rates and spike production were used as primary variables for analysis. Pacemaker-like neurons were identified by continued spiking under low Ca++/high Mg++conditions. The number of pacemakers increased with time under synaptic blocking medium. Sensitivity to CO2 levels was found in some neurons. Acetylcholine changed activity in a complex fashion. Curare, atropine and gallamine modified ACh effects. Eserine alone was ineffective, but potentiated ACh-induced responses. Norepinephrine caused channel-specific increases or decreases, whereas dopamine and serotonin had little effect at 30 μM. GABA and glycine stopped most spiking at 70 μM. Developmental changes in glycine sensitivity (increasing with age) were also observed. It is concluded that pacemaker and chemosensitive neurons develop in medial medulla cultures, and that these cultures are pharmacologically histiotypic.
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El, Ajaltouni Hikmat. "An Efficient QoS MAC for IEEE 802.11p Over Cognitive Multichannel Vehicular Networks." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20715.
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One of the most challenging issues facing vehicular networks lies in the design of an
efficient MAC protocol due to mobile nature of nodes, delay constraints for safety applications and interference. In this thesis, I propose an efficient Multichannel QoS Cognitive MAC (MQOG). MQOG assesses the quality of channel prior to transmission employing dynamic channel allocation and negotiation algorithms to achieve significant increase in channel reliability,
throughput and delay constraints while simultaneously addressing Quality of Service.
The uniqueness of MQOG lies in making use of the free unlicensed bands. To consider
fair effective sharing of resources I propose a Mobility Based Dynamic Transmit Opportunity
(MoByToP) while modifying the 802.11e TXOP (Transmit Opportunity). The proposed protocols were implemented in OMNET++ 4.1, and extensive experiments demonstrated a faster and more efficient reception of safety messages compared to existing VANet MAC Protocols. Finally, improvements in delay, packet delivery ratios and throughput were noticed.
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Qureshi, Faisal Fayyaz. "A reliable and energy efficient cognitive radio multichannel MAC protocol for ad-hoc networks." Thesis, University of Bedfordshire, 2014. http://hdl.handle.net/10547/337026.
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Recent research has shown that several spectrum bands are mostly underutilised. To resolve the issue of underutilisation of spectrum bands across the networks, the concept of Cognitive Radio (CR) technology was envisaged. The CR technology allows Secondary Users (SUs) to acquire opportunistic access to large parts of the underutilised spectrum bands on wireless networks. In CR networks, SUs may scan and identify the vacant channels in the wireless spectrum bands and then dynamically tune their receivers to identify vacant channels and transmitters, and commence communication among themselves without causing interference to Primary/Licensed Users (PUs). Despite the developments in the eld of CR technology, recent research shows that still there are many challenges unaddressed in the eld. Thus, there is a need to reduce additional handshaking over control and data channels, to minimise large sized control frames and to introduce reliable channel selection process and maintenance of SUs' communication when PUs return to a licensed channel. A fundamental challenge a ecting this technology is the identi cation of reliable Data Channels (DCHs) for SUs communication among available channels and the continuation of communication when the PU returns. This doctoral research investigates in detail how to resolve issues related to the protocol design for Cognitive Radio Networks (CRNs) on Medium Access Layers (MAC) for Ad-Hoc networks. As a result, a novel Reliable and Energy e cient Cognitive Radio multi-channel MAC protocol (RECR-MAC) for Ad-Hoc networks is proposed to overcome the shortcomings mentioned. After discussing the background, operation and architecture of CR technology, this research proposes numerous platforms and testbeds for the deployment of personal and commercial applications of the CRNs. Side by side, optimised control frames and a reduced number of handshakes over the CCH are suggested to extend the transmitting time for data communication. In addition, the reliable channel selection process is introduced instead of random selection of DCHs for successful data communication among the SUs. In RECR-MAC, the objective of every SU is to select reliable DCHs, thereby ensuring high connectivity and exchanging the successful data frames across the cognitive network. Moreover, the selection criteria of the DCHs are based on multiple factors, such as an initial selection based on the maximum free time recorded by the SUs over the DCH channel ranking, which is proportional to the number of positive/negative acknowledgements, and the past history of DCHs. If more than two DCHs have an equal value during the second, third and following iterations, then the DCHs are selected based upon the maximum free time. The priorities of the DCHs are then assigned based on Reliable Data Channels, that is, RDCH 1, RDCH 2, RDCH 3, and RDCH 4 respectively (where RDCH 1 and RDCH 2 have the highest priority, DRCH 3 and RDCH 4 have the next priority, and so on). The impacts of channel selection process and Backup Data Channel (BDC) over the proposed RECR-MAC protocol are analysed in combination with comparative benchmark CR-MAC protocols based on the timing diagrams proposed. Finally, the RECR-MAC protocol is validated by using a MATLAB simulator with PU impact over the DCHs, both with and without BDC, and by comparing results, such as communication time, transmitting energy and throughput, with benchmark CR-MAC protocols.
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Özyagci, Ali. "Selfish Dynamic Spectrum Access in Multichannel Wireless Networks : Complete and incomplete information analysis." Licentiate thesis, KTH, Kommunikationssystem, CoS, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50738.
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The increasing popularity and widespread deployment of wireless data systems fuel the increasing demand for more spectrum. On the other hand, various studies measuring spectrum utilization show that there is a huge variation in spectrum utilization at different times and locations. In view of this, various dynamic spectrum access (DSA) methods have been proposed in order to achieve more efficient utilization of spectrum resources by virtue of exploiting the variations in spectrum demand over time and space. Implementing DSA systems in a centralized way can lead to complexity and scalability problems due to the extensive control signaling involved. Therefore distributed implementations of DSA systems in which the users can access the system resources at their own discretion have been proposed. These distributed mechanisms typically incorporate cognitive radio systems which act as agents on behalf of users to measure the radio environment and make decisions based on these measurements. On the other hand, the freedom of the users in distributed systems to form their actions can lead each user to try to maximize its benefit from the system without regard the overall performance of the DSA system. Therefore, selfish behavior can prevail in distributed systems, which is likely to degrade the system performance.In this thesis we investigate the implications of selfish decision making in dynamic spectrum access systems. To address this broad problem, we focus our analysis on a particular system which can represent the essential properties of DSA systems and thus can shed light on the performance of the broad class of DSA systems with selfish users. Specifically, we model a DSA system as a multichannel random access system which uses ALOHA for medium access, and we analyze the behavior of the selfish users by modeling the system as a non-cooperative game. In this analysis we incorporate the effect of channel state information on the decision making of the users; we consider both cases when the users act on global (complete) and on local (incomplete) information. We determine the behavior of the selfish users at the Nash equilibria of the non-cooperative game and measure the performance of the system in terms of sum and individual utilities for various user loads and amount of available resources. We try to identify how the performance of the DSA system with selfish users compares with its cooperative counterpart. By performing these analyses we provide insights into the broader question of whether selfish users can utilize spectrum resources in a DSA system as well as cooperative users.QC 20111208
MultiOperator Dynamic Spectrum access (MODyS)
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Buranapanichkit, D. "Multichannel distributed coordination for wireless sensor networks : convergence delay and energy consumption aspects." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1402955/.
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This thesis develops new approaches for distributed coordination of data-intensive communications between wireless sensor nodes. In particular, the topic of synchronization, and its dual primitive, desynchronization at the Medium Access Control (MAC) or the Application (APP) layer of the OSI stack, is studied in detail. In Chapters 1 and 2, the related literature on the problem of synchronization is overviewed and the main approaches for distributed (de)synchronization at the MAC or APP layers are analyzed, designed and implemented on IEEE802.15.4- enabled wireless sensor nodes. Beyond the experimental validation of distributed (de)synchronization approaches, the three main contributions of this thesis, corresponding to the related publications found below, are: • establishing for the first time the expected time for convergence to distributed time division multiple access (TDMA) operation under the two main desynchronization models proposed in the literature and validating the derived estimates via a real-world implementation (Chapter 3); • proposing the extension of the main desynchronization models towards multi-hop and multi-channel operation; the latter is achieved by extending the concept of reactive listening to multi-frequency operation (Chapter 4 and 5). • analyzing the energy consumption of the distributed TDMA approach under different transmission probability density functions (Chapter 6 and 7). Conclusions and items for future work in relation to the proposals of this thesis are described in Chapter 8.
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McTasney, Robert. "On-demand resource reservation for multichannel wireless mesh networks using cut-through switching." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303875.
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Chen, Ming. "Communication protocols and channel assignment algorithms for high-bandwidth multichannel networks: Design and analysis." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/6776.
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With the rapid progress in Wavelength Division Multiplexing (WDM) techniques, high-bandwidth multichannel networks with many concurrent gigabit channels over a single-mode fiber become feasible. In this thesis, we investigate communication protocols and channel assignment problems in these high-bandwidth multichannel networks. We propose a dynamic channel sharing protocol to accommodate both connection-oriented real-time traffic and connectionless non-real-time traffic efficiently. We further design a multiconnection protocol to allow each originating station to set up connections with multiple terminating stations and allow each terminating station to keep connections with multiple originating stations. To support these protocols, we also propose some dynamical channel assignment algorithms for connectionless traffic. These algorithms are further extended to two-layer high-bandwidth multichannel networks. The proposed channel assignment algorithms are compared with some existing algorithms found in the literature. Analytical performance results in terms of blocking probability and channel utilization for the proposed protocols, and also efficiency and computational complexity for the proposed algorithms, are given. Results show superior performance of these proposed protocols and algorithms.
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Lemeshko, Alexandr, Sergey Garkusha, and Ahmed Hassan Abed. "Two-index Mathematical Model the Distribution of the channels in Multichannel Mesh Networks 802.11." Thesis, Modern Problems of Radio Engineering, Telecommunications and Computer Science. Proceedings of the international Conference TCSET’2012, 2012. http://dspace.uccu.org.ua/handle/123456789/868.
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The article introduces a two-index model of
the distribution channels in the multiradio multichannel wireless mesh networking (MR-MC WMN) standard IEEE 802.11. The model describes the process of distribution channels in both homogeneous and in
heterogeneous MR-MC WMN
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Murdiyat, Prihadi. "A Multichannel Medium Access Control and its Performance Estimation for Multihop Wireless Sensor Networks." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/69408.
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The thesis proposes a three-tier architecture wireless sensor network to monitor the environment of wide rural area. To enhance the network throughput, a multichannel MAC, 2HCR, is developed. The performance of 2HCR is examined for both single and bidirectional traffics. For the bidirectional traffic, a simple priority support scheme is proposed to give a priority for command traffic. Also, a procedure to estimate the throughput of multihop networks is developed to be used in network design.
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Han, Chong. "Analysis and design of efficient medium access control schemes for vehicular ad-hoc networks." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.576087.
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In this dissertation, analysis and design of the efficient Medium Access Control (MAC) sub-layer schemes are considered for Vehicular Ad hoc Networks (VANE~s). The contributions of this study are three-fold. First, an analytical model based on Markov chain is developed in order to investigate the performance of the MAC sub-layer of the IEEE 802.11p for vehicular communications. The results indicate that single channel MAC sub-layers may not be adequate for the future Intelligent Transportation Systems (ITS). The analytical model is validated with the results from simulation-based analysis. Performance analysis based on simulations is given on MAC metrics such as throughput, access delay, packet delivery. Second, a multi-channel MAC protocol is proposed and comprehensively analyzed in terms of channel utilizing and Quality of service (QoS) differentiation for dense VANETs. It is demonstrated that the proposed scheme, namely Asynchronous Multichannel MAC with Distributed TDMA (AMCMACD), improves the system performance in terms of throughput, packet delivery rate, collision rate on service channels, load balancing, and service differentiation for dense vehicular networks. Third, to cope with the interference from contention with neighbours within two hops in large-scale networks, a Large-scale Asynchronous Multichannel MAC (LS-AMCMAC) is proposed. The proposed scheme outperforms other benchmark multichannel MAC schemes in large-scale networks, in terms of throughput, channel utilization, dissemination of emergency messages, and the collision rates on control and service channels.
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Chiu, Hon-sun, and 邵漢新. "Channel assignment and routing in multi-channel multi-interface wireless networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182050.
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Chiu, Hon-sun. "Channel assignment and routing in multi-channel multi-interface wireless networks." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182050.
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Garkusha, Sergey, and Maryna Ievdokymenko. "Classification and Analysis of Methods of the Channels Distribution in Multichannel Mesh Networks IEEE 802.11." Thesis, Modern Problems of Radio Engineering, Telecommunications and Computer Science. Proceedings of the international Conference TCSET’2012, 2012. http://dspace.uccu.org.ua/handle/123456789/869.
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Campbell, Carlene. "An efficient multichannel wireless sensor networks MAC protocol based on IEEE 802.11 distributed co-ordinated function." Thesis, Middlesex University, 2011. http://eprints.mdx.ac.uk/7913/.
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This research aimed to create new knowledge and pioneer a path in the area relating to future trends in the WSN, by resolving some of the issues at the MAC layer in Wireless Sensor Networks. This work introduced a Multi-channel Distributed Coordinated Function (MC-DCF) which takes advantage of multi-channel assignment. The backoff algorithm of the IEEE 802.11 distributed coordination function (DCF) was modified to invoke channel switching, based on threshold criteria in order to improve the overall throughput for wireless sensor networks. This work commenced by surveying different protocols: contention-based MAC protocols, transport layer protocols, cross-layered design and multichannel multi-radio assignments. A number of existing protocols were analysed, each attempting to resolve one or more problems faced by the current layers. The 802.15.4 performed very poorly at high data rate and at long range. Therefore 802.15.4 is not suitable for sensor multimedia or surveillance system with streaming data for future multichannel multi-radio systems. A survey on 802.11 DCF - which was designed mainly for wireless networks –supports and confirm that it has a power saving mechanism which is used to synchronise nodes. However it uses a random back-off mechanism that cannot provide deterministic upper bounds on channel access delay and as such cannot support real-time traffic. The weaknesses identified by surveying this protocol form the backbone of this thesis The overall aim for this thesis was to introduce multichannel with single radio as a new paradigm for IEEE 802.11 Distributed Coordinated Function (DCF) in wireless sensor networks (WSNs) that is used in a wide range of applications, from military application, environmental monitoring, medical care, smart buildings and other industry and to extend WSNs with multimedia capability which sense for instance sounds or motion, video sensor which capture video events of interest. Traditionally WSNs do not need high data rate and throughput, since events are normally captured periodically. With the paradigm shift in technology, multimedia streaming has become more demanding than data sensing applications as such the need for high data rate protocol for WSN which is an emerging technology in this area. The IEEE 802.11 can support data rates up to 54Mbps and 802.11 DCF was designed specifically for use in wireless networks. This thesis focused on designing an algorithm that applied multichannel to IEEE 802.11 DCF back-off algorithm to reduce the waiting time of a node and increase throughput when attempting to access the medium. Data collection in WSN tends to suffer from heavy congestion especially nodes nearer to the sink node. Therefore, this thesis proposes a contention based MAC protocol to address this problem from the inspiration of the 802.11 DCF backoff algorithm resulting from a comparison of IEEE 802.11 and IEEE 802.15.4 for Future Green Multichannel Multi-radio Wireless Sensor Networks.
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Morse, Brian. "Mathematical modelling of sediment transport and bed transients in multichannel river networks under conditions of unsteady flow." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7667.
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The fixed-bed, hydrodynamic and water quality model ONE-D has been successfully applied to virtually every major river system in Canada. In 1984 one of the supporting agencies, Environment Canada, expressed the desire to extend ONE-D for the simulation of sediment transport processes and river-bed dynamics. After performing a literature review it was found that currently available mobile-bed river models did not have the features that the basic ONE-D model had, particularly those required to model channel networks. Because of these numerical modelling limitations it was decided to proceed with this research effort. Sediment transport and bed dynamic routines were written in modular form and the resulting model (ONE-D-SED) became the mobile-bed version of ONE-D. ONE-D-SED was initially validated for hypothetical test cases. This initial application showed that the model reproduced analytical solutions for the 'linear' cases examined. In addition, these simulations provided documentation of the numerical properties of ONE-D-SED's finite difference schemes. Following these preliminary tests correction coefficients were generated for analytical solutions of bed transients of finite height. The subsequent application of ONE-D-SED to the Lower Fraser River was partly in response to the need expressed by Public Works Canada for accurate sediment budgets for certain reaches of this major river system. More importantly, part of this system is tidal, multi-channel network and hence is ideally suited for model validation purposes. Finally, superior sediment data were available for the study reach identified in this research. After analysis of Lower Fraser River sediment data, and calibration of the Ackers-White (A-W) sediment transport equation. ONE-D-SED was applied to the study reach at a "screening-level". Since the results of this application were encouraging, ONE-D-SED was then applied at a detailed level and simulated changes in bed elevation were compared to those observed. In addition to the work directly related to model development, application and validation work was also undertaken to address the issue of representing suspended sediment 'fractions' consisting of a range of grain sizes. This work was motivated by the findings of analyses of the suspended sediment load in the Lower Fraser River and by the necessity of characterizing the representative grain size for natural rivers where there is a large gradation in the bed material composition. This study revealed that the representative grain size of a fraction depends on certain local hydraulic conditions. In addition, correction factors for modelling suspended sediment concentrations were obtained when the geometric grain size of the fraction is used in lieu of the mathematically accurate representative size.
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Rehan, Muhammad Waqas [Verfasser], Erik [Akademischer Betreuer] Maehle, and Stefan [Akademischer Betreuer] Fischer. "High performance communication in stream-based multichannel wireless sensor networks / Muhammad Waqas Rehan ; Akademische Betreuer: Erik Maehle, Stefan Fischer." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2020. http://d-nb.info/1214914179/34.
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Friend, Daniel. "Cognitive Networks: Foundations to Applications." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26449.
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Fueled by the rapid advancement in digital and wireless technologies, the ever-increasing capabilities of wireless devices have placed upon us a tremendous challenge - how to put all of this capability to effective use. Individually, wireless devices have outpaced the ability of users to optimally configure them. Collectively, the complexity is far more daunting. Research in cognitive networks seeks to provide a solution to the diffculty of effectively using the expanding capabilities of wireless networks by embedding greater degrees of intelligence within the network itself.
In this dissertation, we address some fundamental questions related to cognitive networks, such as "What is a cognitive network?" and "What methods may be used to design a cognitive network?" We relate cognitive networks to a common artificial intelligence (AI) framework, the multi-agent system (MAS). We also discuss the key elements of learning and reasoning, with the ability to learn being the primary differentiator for a cognitive network.
Having discussed some of the fundamentals, we proceed to further illustrate the cognitive networking principle by applying it to two problems: multichannel topology control for dynamic spectrum access (DSA) and routing in a mobile ad hoc network (MANET). The multichannel topology control problem involves confguring secondary network parameters to minimize the probability that the secondary network will cause an outage to a primary user in the future. This requires the secondary network to estimate an outage potential map, essentially a spatial map of predicted primary user density, which must be learned using prior observations of spectral occupancy made by secondary nodes. Due to the complexity of the objective function, we provide a suboptimal heuristic and compare its performance against heuristics targeting power-based and interference-based topology control objectives. We also develop a genetic algorithm to provide reference solutions since obtaining optimal solutions is impractical. We show how our approach to this problem qualifies as a cognitive network.
In presenting our second application, we address the role of network state observations in cognitive networking. Essentially, we need a way to quantify how much information is needed regarding the state of the network to achieve a desired level of performance. This question is applicable to networking in general, but becomes increasingly important in the cognitive network context because of the potential volume of information that may be desired for decision-making. In this case, the application is routing in MANETs. Current MANET routing protocols are largely adapted from routing algorithms developed for wired networks.
Although optimal routing in wired networks is grounded in dynamic programming, the critical assumption, static link costs and states, that enables the use of dynamic programming for wired networks need not apply to MANETs. We present a link-level model of a MANET, which models the network as a stochastically varying graph that possesses the Markov property. We present the Markov decision process as the appropriate framework for computing optimal routing policies for such networks. We then proceed to analyze the relationship between optimal policy and link state information as a function of minimum distance from the forwarding node.
The applications that we focus on are quite different, both in their models as well as their objectives. This difference is intentional and signficant because it disassociates the technology, i.e. cognitive networks, from the application of the technology. As a consequence, the versatility of the cognitive networks concept is demonstrated. Simultaneously, we are able to address two open problems and provide useful results, as well as new perspective, on both multichannel topology control and MANET routing.
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Soua, Ridha. "Wireless sensor networks in industrial environment : energy efficiency, delay and scalability." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-00978887.
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Some industrial applications require deterministic and bounded gathering delays. We focus on the joint time slots and channel assignment that minimizes the time of data collection and provides conflict-free schedules. This assignment allows nodes to sleep in any slot where they are not involved in transmissions. Hence, these schedules save the energy budjet of sensors. We calculate the minimum number of time slots needed to complete raw data convergecast for a sink equipped with multiple radio interfaces and heterogeneous nodes traffic. We also give optimal schedules that achieve the optimal bounds. We then propose MODESA, a centralized joint slots and channels assignment algorithm. We prove the optimality of MODESA in specific topologies. Through simulations, we show that MODESA is better than TMCP, a centralized subtree based scheduling algorithm. We improve MODESA with different strategies for channels allocation. In addition, we show that the use of a multi-path routing reduces the time of data collection .Nevertheless, the joint time slot and channels assignment must be able to adapt to changing traffic demands of the nodes ( alarms, additional requests for temporary traffic ) . We propose AMSA , an adaptive joint time slots and channel assignment based on incremental technical solution. To address the issue of scalability, we propose, WAVE, a distributed scheduling algorithm for convergecat that operates in centralized or distributed mode. We show the equivalence of schedules provided by the two modes.
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Zidi, Chaima. "Energy efficient underwater acoustic sensor networks." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCB003/document.
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Les réseaux de capteurs acoustiques sous-marins (UW-ASN) sont les plus nouveaux achèvements technologiques en termes de communication. Les UW-ASN visent à observer et à explorer les lacs, les rivières, les mers et les océans. Récemment, ils ont été soumis à une attention particulière en raison de leur grand potentiel en termes d'applications prometteuses dans divers domaines (militaires, environnementaux, scientifiques ...) et aux nouvelles questions scientifiques qu'ils suscitent. Un problème majeur dans les UW-ASN est l'épuisement rapide de l'énergie, car une grande puissance est nécessaire pour la communication acoustique, tandis que le budget de la batterie des capteurs est limité. Par conséquent, les protocoles de communication énergétiques revêtent une importance primordiale pour faire usage judiciaire du budget énergétique disponible. Dans ce contexte, cette thèse vise à étudier les principales caractéristiques des capteurs acoustiques sous-marins difficiles afin de concevoir des protocoles de communication énergétiques, plus spécifiquement au niveau routage et MAC. Tout d'abord, nous abordons le problème des trous énergétiques dans UW-ASN. Le problème du « sink-hole » se produit lorsque les capteurs les plus proches du sink épuisent leur énergie plus rapidement en raison de leur charge plus lourde. En effet, ces capteurs, en particulier ceux qui sont à un seul saut du sinkstatique, agissent comme des relais pour tous les autres capteurs, ce qui leur épuise sévèrement l’énergie.A la couche de routage,en particulier, nous proposons de distribuer la charge transmise par chaque capteur parmi plusieurs voisins potentiels, en supposant que les capteurs peuvent ajuster leur gamme de communication entre deux niveaux lorsqu'ils envoient ou transmettent des données. Plus précisément, nous déterminons pour chaque capteur l'ensemble des prochains sauts avec les poids de charge associés qui entraînent un épuisement équitable d'énergie entre tous les capteurs du réseau. Ensuite, nous étendons notre stratégie de routage équilibrée en supposant que chaque capteur n'est pas seulement capable d'ajuster sa puissance d'émission à 2 niveaux mais aussi jusqu'à n niveaux où n> 2. Par conséquent, à la couche de routage, pour chaque valeur possible de n, nous déterminons pour chaque capteur l'ensemble des éventuels sauts avec les poids de charge associés qui mènent à une consommation d'énergie équitable chez tous les capteurs du réseau. En outre, nous obtenons le nombre optimal de puissances de transmission n qui équilibre la consommation d'énergie de tous les capteurs pour chaque configuration de réseau. En plus de cela, il convient de souligner que notre protocole de routage étendu utilise un modèle de canal à variation de temps plus réaliste qui tient compte de la plupart des caractéristiques fondamentales de la propagation acoustique sous-marine. Les résultats analytiques montrent que notre protocole de routage assure une réduction importante de la consommation d’énergie. Deuxièmement, pour atténuer les impacts de collision spectaculaires gaspillant l’énergie, nous concevons un protocole MAC multicanal (MC-UWMAC) évitant les collisions pour les UW-ASNs. MC-UWMAC fonctionne avec un canal de contrôle (décomposé en créneaux de temps) et un ensemble de canaux de données à bande passante égale. Les créneaux du canal de contrôle sont dédiés à l’échange RTS / CTS permettant à une paire de capteurs communicants de s'accorder sur l'heure de début de la communication sur un canal de données pré-alloué. Dans cette thèse, nous proposons deux nouvelles procédures associées d'allocation des créneaux du canal de contrôle et d'attribution des canaux de données sans nécessiter de frais de négociation supplémentaires. En conséquence, chaque capteur peut initier l'échange RTS / CTS uniquement à son créneau assigné, calculé à l'aide d'une procédure d'allocation basée sur une partition virtuelle de grille de la zone de déploiement. (...)UnderWaterAcoustic Sensor Networks (UW-ASNs) are the newest technological achievement in terms of communication. Composed of a set of communicating underwater sensors, UW-ASNs are intended to observe and explore lakes, rivers, seas and oceans. Recently, they have been subject to a special attention due to their great potential in terms of promising applications in various domains (military, environmental, scientific...) and to the new scientific issues they raise. A great challenging issue in UW-ASNs is the fast energy depletion since high power is needed for acoustic communication while sensors battery budget is limited. Hence, energy-efficient networking protocols are of a paramount importance to make judicious use of the available energy budget while considering the distinguishing underwater environment characteristics. In this context, this thesis aims at studying the main challenging underwater acoustic sensors characteristics to design energy-efficient communication protocols specifically at the routing and MAC layers. First, we address the problem of energy holes in UW-ASNs. The sink-hole problem occurs when the closest nodes to sink drain their energy faster due to their heavier load. Indeed, those sensors especially the ones that are 1-hop away from the static sink act as relays to it on behalf of all other sensors, thus suffering from severe energy depletion. In particular, at the routing layer, we propose to distribute the transmission load at each sensor among several potential neighbors, assuming that sensors can adjust their communication range among two levels when they send or forward data. Specifically, we determine for each sensor the set of next hops with the associated load weights that lead to a fair energy depletion among all sensors in the network. Then, we extend our balanced routing strategy by assuming that each sensor node is not only able to adjust its transmission power to 2 levels but eventually up to n levels where n > 2. Consequently, at the routing layer, for each possible value of n, we determine for each sensor the set of possible next hops with the associated load weights that lead to a fair energy consumption among all sensors in the network. Moreover, we derive the optimal number of transmission powers n that balances the energy consumption among all sensors for each network configuration. In addition to that, it is worth pointing out that our extended routing protocol uses a more realistic time varying channel model that takes into account most of the fundamental characteristics of the underwater acoustic propagation. Analytical results show that further energy saving is achieved by our extended routing scheme. Second, to mitigate the dramatic collision impacts, we design a collision avoidance energy efficient multichannel MAC protocol (MC-UWMAC) for UW-ASNs. MC-UWMAC operates on single slotted control and a set of equal-bandwidth data channels. Control channel slots are dedicated to RTS/CTS handshaking allowing a communicating node pair to agree on the start time of communication on a pre-allocated data channel. In this thesis, we propose two novel coupled slot assignment and data channels allocation procedures without requiring any extra negotiation overhead. Accordingly, each node can initiate RTS/CTS exchange only at its assigned slot calculated using a slot allocation procedure based on a grid virtual partition of the deployment area. Moreover, for each communicating pair of nodes, one data channel is allocated using a channel allocation procedure based on our newly designed concept of singleton- intersecting quorum. Accordingly, each pair of communicating nodes will have at their disposal a unique 2-hop conflict free data channel. Compared with existing MAC protocol, MC-UWMAC reduces experienced collisions and improves network throughput while minimizing energy consumption
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Yu, Xiaoting. "Inclusive creativity: Wanghong economy and the Chinese social media entertainment industry." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/235385/1/Xiaoting%2BYu%2Bthesis%284%29.pdf.
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This thesis analyses the development trajectory and implications of China’s online creative industry (known as wanghong) and examines both empowerment and precarity of labor in the specific context of China. Focusing on major platforms and media intermediaries, the study explores how the industry facilitates and regulates the production of mass cultural creativity within the datafication and commodification logic of platforms. The thesis considers platform governance, platform affordances, and creative labor management, serving as an extended case study of the global social media entertainment industry.
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Kunert, Kristina. "Architectures and Protocols for Performance Improvements of Real-Time Networks." Doctoral thesis, Högskolan i Halmstad, Inbyggda system (CERES), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-14082.
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When designing architectures and protocols for data traffic requiring real-time services, one of the major design goals is to guarantee that traffic deadlines can be met. However, many real-time applications also have additional requirements such as high throughput, high reliability, or energy efficiency. High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions, while wireless industrial applications, communicating control data, require support of reliability and guarantees of real-time predictability at the same time. To meet the requirements of high-performance embedded systems, this thesis work proposes two multi-wavelength high-speed passive optical networks. To enable reliable wireless industrial communications, a framework incorporating carefully scheduled retransmissions is developed. All solutions are based on a single-hop star topology, predictable Medium Access Control algorithms and Earliest Deadline First scheduling, centrally controlled by a master node. Further, real-time schedulability analysis is used as admission control policy to provide delay guarantees for hard real-time traffic. For high-performance embedded systems an optical star network with an Arrayed Waveguide Grating placed in the centre is suggested. The design combines spatial wavelength reuse with fixed-tuned and tuneable transceivers in the end nodes, enabling simultaneous transmission of both control and data traffic. This, in turn, permits efficient support of heterogeneous traffic with both hard and soft real-time constraints. By analyzing traffic dependencies in this multichannel network, and adapting the real-time schedulability analysis to incorporate these traffic dependencies, a considerable increase of the possible guaranteed throughput for hard real-time traffic can be obtained. Most industrial applications require using existing standards such as IEEE 802.11 or IEEE 802.15.4 for interoperability and cost efficiency. However, these standards do not provide predictable channel access, and thus real-time guarantees cannot be given. A framework is therefore developed, combining transport layer retransmissions with real-time analysis admission control, which has been adapted to consider retransmissions. It can be placed on top of many underlying communication technologies, exemplified in our work by the two aforementioned wireless standards. To enable a higher data rate than pure IEEE 802.15.4, but still maintaining its energy saving properties, two multichannel network architectures based on IEEE 802.15.4 and encompassing the framework are designed. The proposed architectures are evaluated in terms of reliability, utilization, delay, complexity, scalability and energy efficiency and it is concluded that performance is enhanced through redundancy in the time and frequency domains.
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Nugraha, Aditya Arie. "Réseaux de neurones profonds pour la séparation des sources et la reconnaissance robuste de la parole." Electronic Thesis or Diss., Université de Lorraine, 2017. http://www.theses.fr/2017LORR0212.
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Dans cette thèse, nous traitons le problème de la séparation de sources audio multicanale par réseaux de neurones profonds (deep neural networks, DNNs). Notre approche se base sur le cadre classique de séparation par algorithme espérance-maximisation (EM) basé sur un modèle gaussien multicanal, dans lequel les sources sont caractérisées par leurs spectres de puissance à court terme et leurs matrices de covariance spatiales. Nous explorons et optimisons l'usage des DNNs pour estimer ces paramètres spectraux et spatiaux. À partir des paramètres estimés, nous calculons un filtre de Wiener multicanal variant dans le temps pour séparer chaque source. Nous étudions en détail l'impact de plusieurs choix de conception pour les DNNs spectraux et spatiaux. Nous considérons plusieurs fonctions de coût, représentations temps-fréquence, architectures, et tailles d'ensembles d'apprentissage. Ces fonctions de coût incluent en particulier une nouvelle fonction liée à la tâche pour les DNNs spectraux: le rapport signal-à-distorsion. Nous présentons aussi une formule d'estimation pondérée des paramètres spatiaux, qui généralise la formulation EM exacte. Sur une tâche de séparation de voix chantée, nos systèmes sont remarquablement proches de la méthode de l'état de l'art actuel et améliorent le rapport source-interférence de 2 dB. Sur une tâche de rehaussement de la parole, nos systèmes surpassent la formation de voies GEV-BAN de l'état de l'art de 14%, 7% et 1% relatifs en terme d'amélioration du taux d'erreur sur les mots sur des données à 6, 4 et 2 canaux respectivementThis thesis addresses the problem of multichannel audio source separation by exploiting deep neural networks (DNNs). We build upon the classical expectation-maximization (EM) based source separation framework employing a multichannel Gaussian model, in which the sources are characterized by their power spectral densities and their source spatial covariance matrices. We explore and optimize the use of DNNs for estimating these spectral and spatial parameters. Employing the estimated source parameters, we then derive a time-varying multichannel Wiener filter for the separation of each source. We extensively study the impact of various design choices for the spectral and spatial DNNs. We consider different cost functions, time-frequency representations, architectures, and training data sizes. Those cost functions notably include a newly proposed task-oriented signal-to-distortion ratio cost function for spectral DNNs. Furthermore, we present a weighted spatial parameter estimation formula, which generalizes the corresponding exact EM formulation. On a singing-voice separation task, our systems perform remarkably close to the current state-of-the-art method and provide up to 2 dB improvement of the source-to-interference ratio. On a speech enhancement task, our systems outperforms the state-of-the-art GEV-BAN beamformer by 14%, 7%, and 1% relative word error rate improvement on 6-channel, 4-channel, and 2-channel data, respectively
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Wang, Evan Y. (Ye-Wen). "Traffic control in a multichannel optical fiber communication network." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14716.
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Wang, Le. "Hybrid DES-based Vehicular Network Simulator with Multichannel Operations." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/525.
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Vehicular Ad-hoc Network (VANET) is considered to be a viable technology for inter- vehicle communications for the purpose of improving road safety and efficiency. The En- hanced Distribution Channel Access (EDCA) mechanism and multichannel operations are introduced to ensure the Quality of Service (QoS). Therefore, it is necessary to create an accurate vehicular network simulator that guarantees the vehicular communications will work as described in the protocols. A comprehensive vehicular network simulator should consider the interaction between mobility models and network protocols. In this dissertation, a novel vehicular network simulation environment, VANET Toolbox, designed using discrete-event system (DES) is presented. The APP layer DES Module of the proposed simulator integrates vehicular mo- bility operations with message generation functions. The MAC layer DES module supports single channel and multichannel EDCA operations. The PHY layer DES module supports bit-level processing. Compared with packet-based simulator such as NS-3, the proposed PHY layer is more realistic and accurate. The EDCA scheme is evaluated and compared with the traditional Carrier-Sensing Mul- tiple Access (CSMA) scheme, with the simulations proving that data with different priorities can coexist in the same channel. The multichannel operation for the EDCA scheme is also analyzed in this dissertation. The multichannel switching operation and coordination may cause packet dropping or increased latency to the communication. The simulations show that with heavy network traffic, multichannel communication performs better than single channel communication. From the perspective of safety-related messages, the multichannel operation is able to isolate the interference from the non-safety messages in order to achieve a better packet delivery rate and latency. On the other hand, the non-safety messages can achieve high throughput with reasonable latency from multichannel communication under heavy load traffic scenario.
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Semaan, Ghassan. "Architectures and protocols for multichannels based high speed networks /." [S.l.] : [s.n.], 1993. http://library.epfl.ch/theses/?nr=1151.
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Sin, Chun Yin. "Performance analysis of multi-user wireless network /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?ECED%202006%20SIN.
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Neto, Sylvio Ximenez de Azevedo. "Cifra multicanal para maior segurança em redes TCP /IP." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-28112013-143703/.
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Neste documento apresentamos uma cifra multicanal inspirada nas técnicas de telecomunicações de espalhamento espectral (Spread Spectrum), ou como também conhecido, difusão espectral, para prevenir escuta em uma rede de computadores TCP/IP. Mostramos que dividindo um texto-ilegível ciphertext em blocos de tamanho fixo e transmitindo-os aleatoriamente através de diversos canais estabelecidos entre os agentes (transmissor - receptor) é possível aumentar a complexidade da criptanálise por um suposto adversário não autorizado que esteja escutando a comunicação, dessa forma aumentando relativamente a segurança. Mostramos teoricamente que o tempo de quebra da cifra multicanal cresce em ordem fatorial ou exponencial em função do número de canais utilizados na comunicação. Além disso, adaptado a um esquema de difusão binária herdado do AES (Advanced Encryption Standard) é possível incrementar a segurança da cifra multicanal para maior resiliência contra a criptanálise diferencial.In this work we present a multichannel cipher inspired on telecommunications Spread Spectrum techniques to prevent eavesdropping in a TCP/IP network. We show that splitting any ciphertext into fixed size blocks and sending them randomly through multiple channels established between the agents (transmitter and receiver) it is possible to increase the complexity of cryptanalysis by a supposed not authorized adversary that might be eavesdropping the communication, in this way, relatively increasing the security. We show theoretically that the brake time of multichannel cipher grows in factorial or exponential order, in function of the number of channel used in the communication. Moreover adapted to binary spread scheme inherited from AES (Advanced Encryption Standard) it is possible to increase the cipher security for more resilience against differential cryptanalysis.
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Петрусь, Василь Євгенович, and Vasyl Petrus. "Методи та засоби побудови мультиканального сервера в системі «Розумний будинок»." Master's thesis, Тернопільський національний технічний університет імені Івана Пулюя, 2021. http://elartu.tntu.edu.ua/handle/lib/36704.
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Кваліфікаційну роботу магістра присвячено розробленню методів та засобів побудови мультиканального сервера в системі «Розумний будинок».
Проведено огляд методів та засобів побудови бездротових технологій розумного будинку.
Розроблений мультиканальний сервер для розумного будинку фактично виконує роль комутатора і сервера одночасно, який може об’єднувати декілька різних периферійних пристроїв і підмереж за допомогою USB, SPI, I2C шин із безпровідними мережами типу Bluetooth, Wi-Fi, XBee.
Проведено налаштування пристроїв ХВее та тестування всієї мережі можна визначити рівень сигналу та втрати пакетів при передачі даних, що визначають дальність та надійність роботи мережі ХВее. Розгортання мережі Z-Wave потребує налаштування як окремих пристроів, але й налаштування всієї мережі. Таке розгортання може проводитись на базі ПК або на базі запропонованого мультиканального сервера.
Розглянутовимог з охорони праці, розробка і виготовлення мультиканального сервера в системі «Розумний будинок» буде безпечною та забезпечить високу продуктивність праці. Проведення рятувальних та інших невідкладних робіт на об’єкті господарської діяльності в осередку ураження.The master's thesis is devoted to the development of methods and tools for building a multi-channel server in the system "Smart Home". A review of methods and tools for building wireless technologies of a smart home. The developed multi-channel server for smart home actually acts as a switch and server at the same time, which can connect several different peripherals and subnets via USB, SPI, I2C buses with wireless networks such as Bluetooth, Wi-Fi, XBee. The settings of ХВее devices have been adjusted and the whole network has been tested. It is possible to determine the signal level and packet loss during data transmission, which determine the range and reliability of ХВее network operation. Deploying a Z-Wave network requires setting up both individual devices and the entire network. Such deployment can be performed on the basis of a PC or on the basis of the proposed multi-channel server. Considered labor protection requirements, the development and manufacture of a multi-channel server in the system "Smart Home" will be safe and ensure high productivity. Carrying out rescue and other urgent work on the object of economic activity in the affected area.
Вступ РОЗДІЛ 1. Аналіз бездротових технологій розумного будинку 9 1.1. Загальні вимоги до бездротових технологій розумного будинку 9 1.2. Застосування Wi-Fi для домашньої автоматизації 12 1.3. Застосування Z-Wave для розумного будинку. 14 1.4. Застосування Zigbee для розумного будинку 16 1.5. Застосування THREAD для розумного будинку 18 1.6. Використання Bluetooth для розумного будинку 21 1.7. Висновки до розділу 1. 24 РОЗДІЛ 2. Побудова Методів та засобів мультиканального сервера для Розумного будинку 26 2.1. Структурна схема мультиканального сервера для розумного будинку 26 2.2. Апаратні засоби побудови мультиканального сервера 28 2.2.1. Особливості Raspberry Pi 4 28 2.2.2. Плата розширення ARPI600 30 2.2.3. Шилд розширення Expansion Shield 31 2.3. Налаштування роботи мультиканального сервера 32 2.3.1. Налаштування роботи Ethernet 33 2.3.2. Налаштування роботи Wi-Fi 37 2.3.3. Налаштування плати шилда ARPI600 42 2.4. Висновки до розділу 2 45 РОЗДІЛ 3. тестування Методів та засобів побудови мультиканального сервера розумного будинку 47 3.1. Налаштування та тестування мережі ZigBee для розумного будинку 47 3.1.1. Інсталяція програмного забезпечення і підключення модемів ZigBee 47 3.1.2. Налаштування пристроїв та їх тестування 51 3.2. Тестування безпровідної мережі ZigВее в межах розумного будинку 53 3.3. Розгортання та тестування мережі Z-Wave 55 3.4. Висновки до розділу 3 60 РОЗДІЛ 4. ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ 61 4.1 Охорона праці 61 4.2 Безпека в надзвичайних ситуаціях 63 4.3 Висновки до розділу 4 63 Висновки 68 СПИСОК ВИКОРИСТАНИХ ДЖЕРЕЛ ...69 Додаток А. Опубліковані тези конференції за темою дипломної роботи магістра ...72
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Newman, Jonathan P. "Optogenetic feedback control of neural activity." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52973.
Full textAbstract:
Optogenetics is a set of technologies that enable optically triggered gain or loss of function in genetically specified populations of cells. Optogenetic methods have revolutionized experimental neuroscience by allowing precise excitation or inhibition of firing in specified neuronal populations embedded within complex, heterogeneous tissue. Although optogenetic tools have greatly improved our ability manipulate neural activity, they do not offer control of neural firing in the face of ongoing changes in network activity, plasticity, or sensory input. In this thesis, I develop a feedback control technology that automatically adjusts optical stimulation in real-time to precisely control network activity levels. I describe hardware and software tools, modes of optogenetic stimulation, and control algorithms required to achieve robust neural control over timescales ranging from seconds to days. I then demonstrate the scientific utility of these technologies in several experimental contexts. First, I investigate the role of connectivity in shaping the network encoding process using continuously-varying optical stimulation. I show that synaptic connectivity linearizes the neuronal response, verifying previous theoretical predictions. Next, I use long-term optogenetic feedback control to show that reductions in excitatory neurotransmission directly trigger homeostatic increases in synaptic strength. This result opposes a large body of literature on the subject and has significant implications for memory formation and maintenance. The technology presented in this thesis greatly enhances the precision with which optical stimulation can control neural activity, and allows causally related variables within neural circuits to be studied independently.
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Mahé, Pierre. "Codage ambisonique pour les communications immersives." Thesis, La Rochelle, 2022. http://www.theses.fr/2022LAROS011.
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Cette thèse s’inscrit dans le contexte de l’essor des contenus immersifs. Depuis quelques années, les technologies de captation et de restitution sonore immersive se sont développées de manière importante. Ce nouveau contenu a fait naître le besoin de créer de nouvelles méthodes dédiées à la compression audio spatialisée, notamment dans le domaine de la téléphonie et des services conversationnels. Il existe plusieurs manières de représenter l’audio spatialisé, dans cette thèse nous sommes intéressés à l’ambisonie d’ordre 1. Dans un premier temps, nos travaux ont porté sur la recherche d’une solution pour améliorer le codage multimono. Cette solution consiste en un traitement en amont du codec multimono pour décorréler les signaux des composantes ambisoniques. Une attention particulière a été portée à la garantie de continuité du signal entre les trames et à la quantification des métadonnées spatiales. Dans un second temps, nous avons étudié comment utiliser la connaissance de la répartition de l’énergie du signal dans l’espace, aussi appelée image spatiale, pour créer de nouvelles méthodes de codage. L’utilisation de cette image spatiale a permis d’élaborer deux méthodes de compression. La première approche proposée est basée sur la correction spatiale du signal décodé. Cette correction se base sur la différence entre les images spatiales du signal d’origine et du signal décodés pour atténuer les altérations spatiales. Ce principe a été étendu dans une seconde approche à une méthode de codage paramétrique. Dans une dernière partie de cette thèse, plus exploratoire, nous avons étudié une approche de compression par réseaux de neurones en nous inspirant de modèles de compression d’images par auto-encodeur variationnelThis thesis takes place in the context of the spread of immersive content. For the last couple of years, immersive audio recording and playback technologies have gained momentum and have become more and more popular. New codecs are needed to handle those spatial audio formats, especially for communication applications. There are several ways to represent spatial audio scenes. In this thesis, we focused on First Order Ambisonic. The first part of our research focused on improving multi-monocoding by decorrelated each ambisonic signal component before the multi-mono coding. To guarantee signal continuity between frames, efficient quantization new mechanisms are proposed. In the second part of this thesis, we proposed a new coding concept using a power map to recreate the original spatial image. With this concept, we proposed two compressing methods. The first one is a post-processing focused on limiting the spatial distortion of the decoded signal. The spatial correction is based on the difference between the original and the decoded spatial image. This post-processing is later extended to a parametric coding method. The last part of this thesis presents a more exploratory method. This method studied audio signal compression by neural networks inspired by image compression models using variational autoencoders
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Ghrissi, Amina. "Ablation par catheter de fibrillation atriale persistante guidée par dispersion spatiotemporelle d’électrogrammes : Identification automatique basée sur l’apprentissage statistique." Thesis, Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ4026.
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La fibrillation atriale (FA) est l’arythmie cardiaque soutenue la plus fréquemment rencontrée dans la pratique clinique. Pour la traiter, l’ablation par cathéter de zones cardiaques jugées responsables de soutenir l’arythmie est devenue la thérapie la plus utilisée. Un nouveau protocole d’ablation se base sur l’identification des zones atriales où les électrogrammes (EGM) enregistrés à l’aide d’un cathéter à électrodes multiples, appelé PentaRay, manifestent des décalages spatiotemporels significatifs sur plusieurs voies adjacentes. Ce phénomène est appelé dispersion spatio-temporelle (DST). L’intervention devient ainsi plus adaptée aux spécificités de chaque patient et elle atteint un taux de succès procédural de 95%. Cependant, à l’heure actuelle les zones de DST sont identifiées de manière visuelle par le spécialiste pratiquant l’ablation. Cette thèse vise à identifier automatiquement les sites potentiels d’ablation basée sur la DST à l’aide de techniques d’apprentissage statistique et notamment d’apprentissage profond adaptées. Dans la première partie, les enregistrements EGM sont classés par catégorie en DST vs. non-DST. Cependant, le rapport très déséquilibré entre les données issues des deux classes dégrade les résultats de classification. Nous abordons ce problème en utilisant des techniques d’augmentation de données adaptées à la problématique médicale et qui permettent d’obtenir de bons taux de classification. La performance globale s’élève ainsi atteignant des valeurs de précision et d’aire sous la courbe ROC autour de 90%. Deux approches sont ensuite comparées, l’ingénierie des caractéristiques et l’extraction automatique de ces caractéristiques par apprentissage statistique à partir d’une série temporelle, appelée valeur absolue de tension maximale aux branches du PentRay (VAVp). Les résultats montrent que la classification supervisée de VAVp est prometteuse avec des valeurs de précision, sensibilité et spécificité autour de 90%. Ensuite, la classification des enregistrements EGM bruts est effectuée à l’aide de plusieurs outils d’apprentissage statistique. Une première approche consiste à étudier les circuits arithmétiques à convolution pour leur intérêt théorique prometteur, mais les expériences sur des données synthétiques sont infructueuses. Enfin, nous investiguons des outils d’apprentissage supervisé plus conventionnels comme les réseaux de neurones convolutifs (RNC). Nous concevons une sélection de représentation des données adaptées à différents algorithmes de classification. Ces modèles sont ensuite évalués en termes de performance et coût de calcul. L’apprentissage profond par transfert est aussi étudié. La meilleure performance est obtenue avec un RNC peu profond pour la classification des matrices EGM brutes, atteignant 94% de précision et d’aire sous la courbe ROC en plus d’un score F1 de 60%. Dans la deuxième partie, les enregistrements EGM acquis pendant la cartographie sont étiquetés ablatés vs. non-ablatés en fonction de leur proximité par rapport aux sites d’ablation, puis classés dans les mêmes catégories. Les annotations de dispersion sont aussi prises en compte comme une probabilité à priori dans la classification. La meilleure performance représente un score F1 de 76%. L’agrégation de l’étiquette DST ne permet pas d’améliorer les performances du modèle. Globalement, ce travail fait partie des premières tentatives d’application de l’analyse statistique et d’outils d’apprentissage pour l’identification automatique et réussie des zones d’ablation en se basant sur la DST. En fournissant aux cardiologues interventionnels un outil intelligent, objectif et déployé en temps réel qui permet la caractérisation de la dispersion spatiotemporelle, notre solution permet d’améliorer potentiellement l’efficacité de la thérapie personnalisée d’ablation par cathéter de la FA persistanteCatheter ablation is increasingly used to treat atrial fibrillation (AF), the most common sustained cardiac arrhythmia encountered in clinical practice. A recent patient-tailored AF ablation therapy, giving 95% of procedural success rate, is based on the use of a multipolar mapping catheter called PentaRay. It targets areas of spatiotemporal dispersion (STD) in the atria as potential AF drivers. STD stands for a delay of the cardiac activation observed in intracardiac electrograms (EGMs) across contiguous leads.In practice, interventional cardiologists localize STD sites visually using the PentaRay multipolar mapping catheter. This thesis aims to automatically characterize and identify ablation sites in STD-based ablation of persistent AF using machine learning (ML) including deep learning (DL) techniques. In the first part, EGM recordings are classified into STD vs. non-STD groups. However, highly imbalanced dataset ratio hampers the classification performance. We tackle this issue by using adapted data augmentation techniques that help achieve good classification. The overall performance is high with values of accuracy and AUC around 90%. First, two approaches are benchmarked, feature engineering and automatic feature extraction from a time series, called maximal voltage absolute values at any of the bipoles (VAVp). Statistical features are extracted and fed to ML classifiers but no important dissimilarity is obtained between STD and non-STD categories. Results show that the supervised classification of raw VAVp time series itself into the same categories is promising with values of accuracy, AUC, sensi-tivity and specificity around 90%. Second, the classification of raw multichannel EGM recordings is performed. Shallow convolutional arithmetic circuits are investigated for their promising theoretical interest but experimental results on synthetic data are unsuccessful. Then, we move forward to more conventional supervised ML tools. We design a selection of data representations adapted to different ML and DL models, and benchmark their performance in terms of classification and computational cost. Transfer learning is also assessed. The best performance is achieved with a convolutional neural network (CNN) model for classifying raw EGM matrices. The average performance over cross-validation reaches 94% of accuracy and AUC added to an F1-score of 60%. In the second part, EGM recordings acquired during mapping are labeled ablated vs. non-ablated according to their proximity to the ablation sites then classified into the same categories. STD labels, previously defined by interventional cardiologists at the ablation procedure, are also aggregated as a prior probability in the classification task.Classification results on the test set show that a shallow CNN gives the best performance with an F1-score of 76%. Aggregating STD label does not help improve the model’s performance. Overall, this work is among the first attempts at the application of statistical analysis and ML tools to automatically identify successful ablation areas in STD-based ablation. By providing interventional cardiologists with a real-time objective measure of STD, the proposed solution offers the potential to improve the efficiency and effectiveness of this fully patient-tailored catheter ablation approach for treating persistent AF
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Kyasanur, Pradeep Narayanaswamy. "Multichannel wireless networks : capacity and protocols /." 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3242905.
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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6513. Adviser: Nitin H. Vaidya. Includes bibliographical references (leaves 140-146) Available on microfilm from Pro Quest Information and Learning.
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Cheng, Yung-Yuan, and 鄭永遠. "Multichannel Protocols in Wireless Local Area Networks." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/65503602034048714221.
Full textAbstract:
碩士真理大學
資訊工程學系碩士班
99
Using multichannel can enhance throughput in wireless network, but it may cause many problems, such as rendezvous, hidden terminal, as well as exposed terminal problems. This paper proposes two protocols based on home channel mechanism, for avoiding above mentioned problems. In our protocols, each node is equipped with an antenna and assigned a home channel. One protocol called Asynchronous Multichannel Protocol. Nodes in the network need not to synchronize, it can find receiver by channel transfer rules. Time synchronization is needed for the other protocol. The time interval is divided into control interval and data interval. In control interval, each receiver has an independent negotiation slot for communication. Hence, the collision of messages is reduced. Finally, those two protocols are shown that they will reduce the transmission time and prevents nodes from starvation.
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Meng, Lehan. "Multichannel optical access networks : design and resource management." Thesis, 2009. http://spectrum.library.concordia.ca/976371/1/MR63281.pdf.
Full textAbstract:
At present there is a strong worldwide push towards bringing fiber closer to individual homes and businesses. The next evolutionary step is the cost-effective all-optical integration of fiber-based access and metro networks. STARGATE [1] is an all-optical access-metro architecture which does not rely on costly active devices, e.g., Optical Cross-Connects (OXCs) or Fixed Wavelength Converters (FWCs), and allow low-cost PON technologies to follow low-cost Ethernet technologies from EPON access into metro networks, resulting in significantly reduced cost and complexity. It makes use of an overlay island of transparency with optical bypassing capabilities. In this thesis we first propose Optical Network Unit (ONU) architectures, and discuss several technical challenges, which allow STARGATE EPONs (SG-EPONs) to evolve in a pay-as-you-grow manner while providing backward compatibility with legacy infrastructure and protecting previous investment. Second, and considering all the hardware constraints, we present the corresponding dynamic bandwidth allocation algorithm for effective resource management in these networks and investigate their performances (delay, throughput) through simulation experiments. We further investigate the problem of transmission grant scheduling in multichannel optical access networks using a scheduling theoretic approach. We show that the problem can be modeled as an Open Shop and we formulate the joint scheduling and wavelength assignment problem as a Mixed Integer Linear Program (MJLP) whose objective is to reduce the length of a scheduling period. Since the problem is known to be NP-hard, we introduce a Tabu Search based heuristic for solving the joint problem. Different other heuristics are also considered and their performances are compared with those of Tabu and MILP. Results indicate that by appropriately scheduling transmission grants and assigning wavelengths, substantial and consistent improvements may be obtained in the network performance. For example, Tabu shows a reduction of up to 29% in the schedule length with substantial reduction in channel idle gaps yielding to both higher channel utilization and lower queuing delays. Additionally, when the number of channels in the network is not small, the benefits of performing appropriate wavelength assignment, together with transmission scheduling, are observed and discussed. We further perform a packet-level simulation on the considered network to study the benefits of efficient grant scheduling; significant improvements are shown both in terms of system utilization and packet queuing delays.
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Chien, Chih-Yang, and 簡志揚. "Exploring Multichannel MAC Protocols in Cognitive Radio Networks." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/96tn56.
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碩士國立臺北科技大學
資訊工程系研究所
96
In cognitive radio networks, how does communication nodes effectively sense and compete for the wireless network transmission bandwidth is a very important subject. Although the IEEE802.11 standard provides multiple channels for the Wireless Local Area Network (WLAN), but its Medium Access Control (MAC) is designed for transmission on single channel. Using CSMA/CA scheme can avoid collision and packet loss. However, the neighbors of transmitting nodes must wait until the transmission is over to establish their own communication links. Based on the CSMA scheme, CT-MAC can achieve concurrent transmissions without interfering primary communication links. In this thesis, we first revise CT-MAC to increase the throughput. Then, we consider the multi-channel environments and propose a multi-channel MAC protocol which can solve the Multi-Channel Hidden Terminal problem. Our experimental results show that the proposed MAC protocols can reduce access time and transmission time as well as increase the throughput dramatically.
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"A multichannel computer network with local and global transceiving media." Chinese University of Hong Kong, 1985. http://library.cuhk.edu.hk/record=b5885553.
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Chen, Yan-Da, and 陳彥達. "Distributed Multichannel Negotiation Protocol for Multihop Mobile Ad Hoc Networks." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/68943347064476710329.
Full textAbstract:
碩士淡江大學
資訊工程學系
91
We proposed a multichannel medium access control (MAC) protocol,named distributed multichannel negotiation protocol (DMNP), for multihop mobile ad hoc networks (MANET) by using single transceiver. Increasing the capacity of wireless communication is an open and interesting research area which has attracted much attention. The familiar solution is dividing the radio spectrum into several independent radio channels, which can be operated and accessed simultaneously by all nodes within its radio transmitting power. Nevertheless, all solutions of researches adopt multiple transceivers to fulfill this goal. These schemes will be short of implementation and increase the prime cost since most wireless devices only equip a single transceiver. Moreover, with a few exceptions,most researchers have emphasized centralized resource allocation algorithms for cellular systems where the base station keeps track of the requirements of the various users and is thus responsible for the management of network resources.However, on the other hand, MANETs are generally configured as peer-to-peer networks with no centralized hubs or controllers. Therefore, we address the issue of distributed resource allocation for MANET by presenting a DMNP that builds on the request-to-send/clear-to-send (RTS/CTS) bandwidth reservation mechanism with single transceiver constraint. We show via simulations that DMNP provides a higher throughput compared to its single channel counterpart by promoting simultaneous transmissions in different channels. Simulation results show that the performance of proposed DMNP derives well.
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Wang, Yao-Zong, and 汪耀宗. "A Multiple Rendezvous Multichannel MAC Protocol for Underwater Sensor Networks." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/78169561278978071467.
Full textAbstract:
碩士國立臺灣海洋大學
資訊工程學系
97
Compared with traditional terrestrial radio transmissions inWireless Sensor Networks (WSN), the features of transmissions in UnderWater Sensor Networks (UWSN) include lower transmission rate, longer delay time, and higher power consumption. In such a circumstance, the negative effects of transmission collisions deteriorate. Most of the existing UWSN MAC protocols handle the collision problem in a single hop or light-loaded environment. They fail to function effectively in a multi-hop network consisting of more sensor nodes with heavier traffic loads. Using the concept of cyclic quorum systems, we propose a distributed multiple rendezvous multichannel MAC protocol, MM-MAC, in this paper to reduce collision probability. The advantages of the proposed protocol are threefold: 1) Only one modem is needed for each node to solve the missing receiver problem which is often encountered in multichannel protocols. 2) Multiple sensor node pairs can complete their channel negotiations on different channels simultaneously. 3) After successful channel negotiations, the data packets sent by sensor nodes are collision-free.Simulation results verify that our protocol can reduce collision probability significantly which enhances the network performance and conserves more energy in a multi-hop UWSN.