Dissertations / Theses on the topic 'Communication networks'
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Lundy, G. M. "Systems of communicating machines : a model for communication protocols." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/8210.
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Rafiei, Nima. "Quantum Communication Networks." Thesis, Stockholms universitet, Fysikum, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-186606.
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Quantum communication protocols invoke one of the most fundamentallaws of quantum mechanics, namely the superposition principle whichleads to the no-cloning theorem. During the last three decades, quantumcryptography have gone from prospective theories to practical implementationsscalable for real communication. Scientist from all over the world havecontributed to this major progress, starting from Stephen Wiesner, CharlesH. Bennett and Gilles Brassard who all developed the theory of QuantumKey Distribution (QKD). QKD lets two users share a key through a quantumchannel (free space or fiber link) under unconditionally secure circumstances.They can use this key to encode a message which they thereaftershare through a public channel (internet, telephone,...). Research developmentshave gone from the ordinary 2-User Quantum Key Distribution oververy small free space distances to distances over 200 km in optical fiber andQuantum Key Distribution Networks.As great experimental achievements have been made regarding QKDprotocols, a new quantum communication protocol have been developed,namely Quantum Secret Sharing. Quantum Secret Sharing is an extensionof an old cryptography scheme called Secret Sharing. The aim of secretsharing is to split a secret amongst a set of users in such a way that thesecret is only revealed if every user of this set is ready to collaborate andshare their part of the secret with other users.We have developed a 5-User QKD Network through birefringent singlemode fiber in two configurations. One being a Tree configuration and theother being a Star configuration. In both cases, the number of users, thedistances between them and the stability of our setup are all well competitivewith the current worldwide research involving similar work.We have also developed a Single Qubit Quantum Secret Sharing schemewith phase encoding through single mode fiber with 3, 4 and 5 parties. Thelatter is, to the best of our knowledge, the first time a 5-Party Single QubitQuantum Secret Sharing experiment has been realized.
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Sanchez, Net Marc. "Architecting space communication networks." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90792.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-122).
Reliable communication and navigation services are critical to robotic and human space missions. NASA currently provides them through three independent and uncoordinated network that consist of both Earth-based and space-based assets, all managed under the Space Navigation and Communication Program. Nevertheless, the ever increasing mission requirements and funding limitations motivates the need of revising the current network architectures in order to identify areas of potential performance and cost efficiency improvements. The main objective of this thesis is to present a tool that helps decision-makers during the process of architecting a space communication network by (1) systematically enumerating and exploring the space of alternative network architectures, (2) identifying those with better performance and lower cost, and (3) providing traceability between the outputs of the tool and the architecting decisions. The tool is tailored to the high level design of near Earth space communication networks that support robotic and human activities in the Earth vicinity through a set of relay communication satellites and their supporting ground stations. The decisions available to the network architect (both technical and contractual) are presented and along with their couplings. The tool is validated by comparing it to NASA's Space Network. The current operations of the system are analyzed and used as the baseline case for the validation process. Results demonstrate that the both performance model and spacecraft design algorithm are accurate to less than 10%, while the cost module produces estimates with a 15% error. Finally, the utility of the tool is demonstrated through three case studies on the evolution of the Space Network. In particular, the impact of new radio-frequency and optical technology to increase the system capacity is analyzed based on the predicted demand for the 2020-2030 decade. Similarly, the savings of flying relay transponders in commercial satellites as hosted payloads are quantified and benchmarked with respect to NASA's current approach of procuring and operating the entire network. Lastly, the tool is used to compare the current Space Network bent-pipe architecture with a constellation of satellites that takes advantage of inter-satellite links to provide full coverage of low Earth orbits with only one ground station.
by Marc Sanchez Net.
S.M.
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Lakshmanan, Meenakshi. "Pricing in communication networks." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624263.
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Moessner, K. "Reconfigurable mobile communication networks." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/844245/.
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Telecommunication technologies and networks are constantly changing; with the introduction of the GSM system the shift from wired to wireless telephony experienced a unique boom. Since then, behaviour and communication needs of users (i.e. subscribers) have undergone rapid changes from initially the need for pure wireless voice transmission to now data and multimedia content traffic. Introduction of the 3rd Generation (UMTS/IMT 2000) promised the delivery of these services and the integration with the Internet. However, legacy technologies and networks are not likely to be replaced soon, the different wireless and wired communication and information infrastructures will co-exist and will have to work, seemingly seamless, together. The here documented research work delivers basic mechanisms supporting this integration, therefore a variety of technologies from different areas, ranging from Software Radio technology to Object-Oriented computing, have been brought together to introduce reconfigurability to mobile communication networks. Distributed object computing technologies are evaluated and their application as signalling and support platforms for reconfigureable systems is shown in different examples. Other novelties are the introduction of a protocol for download of reconfiguration software, from various software sources, these sources include Smart Cards, wired outlets and Over-The-Air. Furthermore, an object-oriented framework for flexible, 'on-the-fly' protocol exchange has been developed; the mechanisms and architecture of this framework are described within this thesis. Combining protocol reconfiguration, software download and distributed platforms and focusing on control and management of reconfiguration have led to the design and definition of a reconfiguration management architecture. Functionality and structure of this architecture are documented, and its single modules are described. Providing means and mechanisms enabling management and control of reconfiguration within reconfigureable mobile communication networks is the purpose of this thesis. KM, Guildford, July 2001 Key words: reconfiguration, reconfiguration management. Software Radio, object-orientation, middleware, CORBA, Universal Control CHannel.
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Gao, Zihao. "Wireless Powered Communication Networks." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17169.
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The limited life time of batteries is a crucial issue in energy-constrained wireless communications. Recently, the radio frequency (RF) wireless energy transfer (WET) technique has been developed as a new practical method to extend the life time of wireless communication networks. Inspired by this, wireless-powered communication network (WPCN) has attracted much attention. Therefore, in this thesis, we consider practical WET and wireless-powered information transmission in WPCNs. First we investigate a WPCN with two nodes, in which an access point (AP) exchanges information with a wireless-powered user. The user is assumed to have no embedded energy supply and needs to harvest energy from RF signals broadcast by the AP. Differing from existing work that focuses on the design of wireless-powered communication with one-way information flow, we deal with a more general scenario where both the AP and the user have information to transmit. Considering that the AP and user can work in either half-duplex or full-duplex mode as well as having two practical receiver architectures at the user side, we propose five elementary communication protocols for the considered system. Moreover, we define the concept of a throughput region to characterize the tradeoff between the uplink and downlink throughput in all proposed protocols. Numerical simulations are finally performed to compare the throughput regions of the proposed five elementary protocols. To further the study on WPCN, we investigate a wireless-powered two-way relay system, in which two wireless-powered sources exchange information through a multi-antenna relay. Both sources are assumed to have no embedded energy supply and thus first need to harvest energy from the radio frequency signals broadcast by the relay before exchanging their information via the relay. We aim to maximize the sum throughput of both sources by jointly optimizing the time switching duration, the energy beamforming vector and the precoding matrix at the relay. The formulated problem is non-convex and hard to solve in its original form. Motivated by this, we simplify the problem by reducing the number of variables and by decomposing the precoding matrix into a transmit vector and a receive vector. We then propose a bisection search, a 1-D search and an iterative algorithm to optimize each variable. Numerical results show that our proposed scheme can achieve higher throughput than the conventional scheme without optimization on the beamforming vector and precoding matrix at the relay. Due to the high attenuation of RF energy over a long distance, RF based wireless-powered communication is usually designed for low-power scenarios, e.g., wireless-powered sensor networks. Recently, magnetic induction (MI) based WET has been proposed to wirelessly transfer a large amount of energy. Inspired by this, we investigate MI based WET in WPCN. Specifically, we study a MI based wireless-powered relaying network, in which a MI source transmits information to a MI destination, with the help of a MI based wireless powered relay. We propose four active relaying schemes, which consider different relaying modes and different energy harvesting receiver architectures at the relay. We then aim to maximize the end-to-end throughput of each scheme by using a bisection search, a water-filling algorithm, a Lagrange multiplier, quasi-convex programming and an iterative algorithm. We compare the proposed active relaying schemes with passive relaying. Numerical results show that the proposed relaying schemes with a decode-and-forward relaying mode significantly improve the throughput over passive relaying.
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Cullen, Cionaith. "Network and signalling aspects of satellite personal communication networks." Thesis, University of Surrey, 1995. http://epubs.surrey.ac.uk/842984/.
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The use of satellites for mobile communication applications has become a global issue. The use of handheld, vehicle mounted and transportable terminals is a key feature of Satellite Personal Communication Networks (S-PCNs). Due to the higher eirp requirements on the Earths surface and also because of their inherent delay, geostationary (GEO) satellites are not considered suitable for such applications. Instead, constellations of satellites at lower altitudes have been proposed for use in what are termed 2nd generation mobile satellite communication systems. Low intensity regions in the Earths surrounding trapped radiation bands, have resulted in two altitude bands of specific interest, resulting in two constellation types - LEO (Low Earth Orbit) constellations at around 1,000 km and MEO (Medium Earth Orbit) constellations at around 10,000 km. A satellite constellation consists of a number of satellites orbiting at the same altitude and inclination and phased in a specific way. The work reported in this thesis proposes a network control architecture for LEO or MEO based S-PCN systems. Air-interface signalling aspects are then considered for mobility management and call setup signalling. LEO and MEO constellation design aspects and properties are initially considered. Important implications on the control network are drawn based on constellation coverage and connectivity properties. Other system constraints such as terrestrial network interworking considerations as well as user, network operator and regulator requirements are also considered. Finally network and more specifically satellite control signalling is examined before a S-PCN architecture is proposed. The reference architecture results in constellation control being distributed globally with individual satellite control, at any one time, being located at a specific earth station. The use of two earth station types allows network administration to be separated from traffic channel carrying aspects. In order to reduce system setup cost and delay, the reuse of network related standards from the GSM terrestrial mobile communication system is envisaged. An equivalence is made between the S-PCN architecture and the GSMs terrestrial architecture. Network implementation aspects are considered for a 14 satellite MEO constellation. Network implications resulting from the use of LEO and MEO constellations are considered. After an examination of S-PCN traffic demand on a MEO constellation, mobility management signalling is considered. A new approach is proposed based on the use of a positioning system. The performance of this approach is examined from a system signalling viewpoint for both LEO and MEO constellations and a method to minimise the required amount of signalling is described. The air interface signalling procedure for location update, based on a modified GSM network layer protocol, is simulated from a delay point of view for both LEO and MEO constellations. User-originated, user-terminated and user-to-user call setup signalling were also simulated and their delay performance examined. The importance of random access channel delay and of user cooperation with the link were highlighted as aspects which have a significant influence on the average signalling delay. Finally, the effect of common and dedicated control channel system signalling on satellite power consumption, based on busy hour call setup and mobility management signalling estimates, was examined for a MEO constellation. From this, conclusions can be made on the signalling power efficiency of S-PCN systems.
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Pendergast, Mark Overton. "Interprogram communication for PC/LAN-based collaborative applications: PLEXNET, a session level communications system." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184784.
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This dissertation describes the analysis, design, and implementation of a session level communication system referred to as PLEXNET. PLEXNET was developed specifically to provide communication services required by Computer Supported Cooperative Work (CSCW) applications but which are not currently available as part of commercially available LAN products. CSCW services include such things as: reliable broadcast communications, dynamic multicasting, and message queuing. Analysis of CSCW networking requirements entailed: reviewing CSCW applications and communications systems; synthesizing a data exchange model for collaborative tools; and defining a target system (PC-LAN). PLEXNET design provides a discussion of: networking tradeoffs, the relationship between PLEXNET and NETBIOS, PLEXNET queue structure, and PLEXNET implementation details. The design and implementation of PLEXNET were validated by performing discrete event simulations comparing response times and resource utilization for three communication paradigms and by developing four collaborative applications which employ PLEXNET for data communications. These applications are: Multi-User LAN Editor, Electronic Discussion System, Contracts Procurement, and Video Switcher.
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Lu, Ching-sung. "Automated validation of communication protocols /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726702499786.
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Krause, Wolfram O. "Wireless communication networks : structure and dynamics of wireless multi-hop ad hoc communication networks /." Lichtenberg (Odenw.) : Harland media, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015507583&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Cui, Nenghui. "Wireless Sensor Networks - Network Coded Cooperative Communication : Design and Implementation." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-188750.
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This thesis is concerned with the design and implementation of a testbed for network coded cooperative communication (NC-CC) in IEEE 802.15.4-based wireless sensor networks (WSNs). The work and test are based on Contiki 2.5 and sensor nodes Zolertia Z1. In the testbed, a new network framework with large extensibility is provided, as well as a basic realization of NC-CC. In our implementation, CC is realized as a Rime primitive in Contiki, while NC is inserted as a new layer between Rime and MAC to perform opportunistic coding. In this way the network stack of Contiki is extended while still keeping the backward compatibility. Because of the lack of multicast in IEEE 802.15.4 protocol and the contradiction of applying continuous overhearing on power-constraint sensor nodes, new mechanisms called pseudo overhearing and pseudo multicast is proposed in our testbed. A configurable test program is also designed for the purpose of evaluation. A combination of two senders, one relay and one destination is used as our network model. Experiments show that all the designed functions work properly. But to be robust, more experiments under different models should be brought in the future. A more detailed report on the experiments can be found in my project-partner Yitian Yan’s thesis.
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Jeoun, Kristina S. "The tactical network operations communication coordinator in mobile UAV networks." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FJeoun.pdf.
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Moldoveanu, Matei. "In-Network Learning : Distributed Training and Inference in Communication Networks." Electronic Thesis or Diss., Université Gustave Eiffel, 2023. http://www.theses.fr/2023UEFL2003.
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Nous étudions le problème de l'apprentissage statistique distribué. Plus précisément, nous considérons le cadre d'apprentissage distribué et d'inférence. Dans le scénario considéré, plusieurs nœuds doivent travailler ensemble pour prédire une certaine quantité d'intérêt/d'événement au niveau d'un nœud central. Certains nœuds observent les données liées à la quantité cible, tandis que d'autres ne le font pas ; cependant, les nœuds qui n'ont pas accès aux données forment un lien entre le nœud central et les nœuds qui observent les données. Nous considérons le cas où un graphe orienté acyclique peut modéliser un tel réseau. Nous étudions comment on peut entraîner un réseau aussi complexe de manière distribuée, c'est-à-dire sans échange de données brutes, pour le cas où chaque nœud est équipé d'un réseau de neurones pour traiter les données. Inspirés par le fameux problème de goulot d'étranglement de l'information, nous utilisons d'abord la théorie de la distorsion du débit pour dériver un compromis réalisable entre les performances du réseau sous perte logarithmique et le débit des messages transmis entre les nœuds. Ensuite, en utilisant le compromis obtenu, nous montrons comment on peut dériver une fonction de perte qui peut entraîner conjointement les réseaux de neurones aux nœuds de manière distribuée. Nous étudions également le problème d'ordonnancement et d'allocation de puissance pour le modèle proposé pour les topologies de réseau en étoile, c'est-à-dire dans lequel les nœuds d'observation des données sont connectés directement au nœud central faisant la prédiction. En raison de la nature distribuée des données et de l'absence d'a priori connu, aucun nœud ne peut fournir une image définitive du système et décider correctement de l'allocation des ressources. Pour surmonter ce problème, le professeur Abdellatif Zaidi a breveté une solution dans laquelle 1. Chaque appareil mesure sa propre évaluation locale de la pertinence des données qu'il détient pour la tâche d'inférence en cours et la transmet au nœud de décision. 2. Cet appareil envoie également simultanément les valeurs d'activation de sortie au nœud de décision. 3. Le nœud de décision combine toutes les informations reçues (valeurs d'activation des différents appareils ainsi que leurs évaluations locales individuelles) et forme ensuite sa propre évaluation (globale) de la pertinence de l'observation de chaque appareil. 4. Les nœuds centraux ont utilisé les évaluations obtenues pour planifier l'allocation de puissance. Dans cette thèse, nous nous appuyons sur le brevet en présentant une méthode de calcul des évaluations locales et globales et en proposant de nouveaux algorithmes d'ordonnancement et d'allocation de puissanceWe study the problem of distributed statistical learning. More specifically, we consider the distributed training and inference setting. In the considered scenario, multiple nodes need to work together to predict some quantity of interest/event at a central node. Some nodes observe data related to the target quantity, while others do not; however, the nodes that do not have access to data form a link between the central node and the nodes that observe data. We consider the case in which a directed acyclic graph can model such a network. We study how one can train such a complex network in a distributed manner, i.e., without the exchange of raw data, for the case in which each node is equipped with a neural network to process the data. Inspired by the famous information bottleneck problem, we first use rate-distortion theory to derive an achievable trade-off between the network's performance under logarithmic loss and the rate of the messages passed between the nodes. Then, using the obtained trade-off, we showcase how one can derive a loss function that can jointly train the neural networks at the nodes in a distributed manner. We also study the problem of scheduling and power allocation for the proposed model for the star network topologies, i.e., in which the data observing nodes are connected directly to the central node making the prediction. Due to the distributed nature of the data and the lack of a known prior, no node can provide a definitive picture of the system and correctly decide the allocation of the resources. To overcome this issue, Prof. Abdellatif Zaidi patented a solution in which 1. Each device measures its own local assessment of how relevant is the data it holds for the inference task at hand and transmits it to the decision node. 2. That device also simultaneously sends the output activation values to the decision node. 3. The decision node combines all received information (activation values from the various devices as well as their individual local assessments) and then forms its own (global) assessment of how relevant each device's observation is. 4. The central nodes used the obtained assessments for scheduling for power allocation. In this thesis, we build upon the patent by presenting a method for computing the local and global assessments and proposing new scheduling and power allocation algorithms
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Lindh, Thomas. "Performance monitoring in communication networks." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3724.
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Performance monitoring in communication networks, which isthe main topic of this thesis, is an essential part ofperformance and network management. The applications cover anumber of different areas such as daily operations andmaintenance, usage information for billing purposes, customerreports, traffic control, planning, and dimensioning.
The main purpose of the thesis is to develop a single methodfor measurement of the most significant network performanceparameters in IP networks. It is a continuation from a previouslicentiate thesis that focused on performance monitoring incell-based networks.
The development of a measurement method that combines activeand passive approaches using monitoring blocks is the maincontribution of this work. A traffic flow performance meterbased on these principles has been implemented as an extensionto the open source flow meter NeTraMet and tested. Theresolution and precision of the results are determined by thesize of the monitoring block, which is the methods mainparameter. Relevant statistical issues regarding packet lossesand delays are analysed. Finally, the measurement method isdiscussed in the context of applications, as well as networkand service management systems in general.
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Mykkeltveit, Anders. "Dependability differentiation in communication networks." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for telematikk, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5011.
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Unintentional failures affect links and nodes in communication networks. Recovery mechanisms are the key tool for achieving the dependability required by the services using the network. However, high dependability in communication networks comes at a high cost in terms of the capacity needed by these mechanisms.The traffic from all services and users is carried by the same backbone network. Since the users and services have different requirements, and users have different willingness to pay for a high quality of service, it is desirable to have methods that enable provision of different levels of dependability in the same network, i.e. dependability differentiation. The thesis addresses dependability differentiation in connection-oriented backbone communication networks. Two methods to provide connections meeting differentiated guarantees on the asymptotic availability are proposed.The first of these uses a novel flexible arrangement for dedicated protection denoted a protection pattern. The protection pattern is used in a proposed distributed connection management system. The system is compared with alternative proposals based on centralized management and shows good performance. The second proposal uses shared protection, which may potentially use less resources in terms of bandwidth, but has higher complexity than dedicated protection. The proposed system is based on rules to control the sharing to enable provision of guarantees. Simulation results show that the proposed method performs significantly better than an alternative strategy based on dedicated protection.A different approach to availability-guaranteed services is to offer guarantees on the interval availability which is a measure commonly used Service Level Agreements (SLAs). The thesis contains a proposal of using adaptive management to increase compliance with interval availability guarantees. Different adaptive management policies are proposed and compared to alternative static provisioning policies in a case study. The thesis also addresses the problem of measuring dependability by simulation. To reduce the simulation effort needed to obtain precise estimates of dependability attributes, a rare-event simulation technique has been applied to the well-known Network Simulator 2 (NS2). The results show that the technique is applicable to this types of simulation scenario, but the gain is modest. The thesis also contains a broad literature survey of dependability differentiation research. This is the first survey of the topic. Hence, it is in itself a significant contribution. A classification scheme for how to approach differentiation is proposed and a critical evaluation of the state of art is given.This thesis contributes to fill in some of the ``gaps'' identified, but there are still significant challenges ahead before differentiation may be deployed in operational networks.
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Chapple, Rebecca Jane. "Communication problems in optical networks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq37496.pdf.
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Meriluoto, Laura. "Negative externalities in communication networks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0008/NQ52712.pdf.
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Gutekunst, Samuel C. "Characterizing Forced Communication in Networks." Scholarship @ Claremont, 2014. http://scholarship.claremont.edu/hmc_theses/56.
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This thesis studies a problem that has been proposed as a novel way to disrupt communication networks: the load maximization problem. The load on a member of a network represents the amount of communication that the member is forced to be involved in. By maximizing the load on an important member of the network, we hope to increase that member's visibility and susceptibility to capture. In this thesis we characterize load as a combinatorial property of graphs and expose possible connections between load and spectral graph theory. We specifically describe the load and how it changes in several canonical classes of graphs and determine the range of values that the load can take on. We also consider a connection between load and liquid paint flow and use this connection to build a heuristic solver for the load maximization problem. We conclude with a detailed discussion of open questions for future work.
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Mihalak, Matus. "Optimization problems in communication networks." Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/30104.
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We study four problems arising in the area of communication networks. The minimum-weight dominating set problem in unit disk graphs asks, for a given set D of weighted unit disks, to find a minimum-weight subset D' ⊆ D such that the disks D' intersect all disks D. The problem is NP-hard and we present the first constant-factor approximation algorithm. Applying our techniques to other geometric graph problems, we can obtain better (or new) approximation algorithms. The network discovery problem asks for a minimum number of queries that discover all edges and non-edges of an unknown network (graph). A query at node v discovers a certain portion of the network. We study two different query models and show various results concerning the complexity, approximability and lower bounds on competitive ratios of online algorithms. The OVSF-code assignment problem deals with assigning communication codes (nodes) from a complete binary tree to users. Users ask for codes of a certain depth and the codes have to be assigned such that (i) no assigned code is an ancestor of another assigned code and (ii) the number of (previously) assigned codes that have to be reassigned (in order to satisfy (i)) is minimized. We present hardness results and several algorithms (optimal, approximation, online and fixed-parameter tractable). The joint base station scheduling problem asks for an assignment of users to base stations (points in the plane) and for an optimal colouring of the resulting conflict graph: user u with its assigned base station b is in conflict with user v, if a disk with center at 6, and u on its perimeter, contains v. We study the complexity, and present and analyse optimal, approximation and greedy algorithms for general and various special cases.
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Cavallari, Riccardo <1986>. "Human-Centric Wireless Communication Networks." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7444/1/tesi.pdf.
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This thesis covers two main topics: the design and performance
evaluation of Wireless Body Area Networks (WBANs), and the simulation
and mathematical modeling of Delay Tolerant Networks (DTNs).
Different Medium Access Control (MAC) protocols for WBANs are
implemented on dedicated hardware in order to evaluate, through
extensive measurement campaigns, the performance of the network in
terms of packet loss rate, delay and energy consumption. Novel
solutions to cope with body shadowing and to improve the coexistence
with other wireless technologies, are presented and evaluated. An
analytic model for the CSMA/CA protocol defined in the IEEE 802.15.6
standard is also presented.
The benefits of offloading part of the traffic carried by a wireless
backbone to a DTN composed of mobile nodes in a urban environment, is
also investigated. A more analytic approach, mainly using tools from
stochastic geometry and Markov chains theory, is used to develop a
mathematical framework for the evaluation of the performance of
routing rules for DTNs.
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Cavallari, Riccardo <1986>. "Human-Centric Wireless Communication Networks." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7444/.
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This thesis covers two main topics: the design and performance
evaluation of Wireless Body Area Networks (WBANs), and the simulation
and mathematical modeling of Delay Tolerant Networks (DTNs).
Different Medium Access Control (MAC) protocols for WBANs are
implemented on dedicated hardware in order to evaluate, through
extensive measurement campaigns, the performance of the network in
terms of packet loss rate, delay and energy consumption. Novel
solutions to cope with body shadowing and to improve the coexistence
with other wireless technologies, are presented and evaluated. An
analytic model for the CSMA/CA protocol defined in the IEEE 802.15.6
standard is also presented.
The benefits of offloading part of the traffic carried by a wireless
backbone to a DTN composed of mobile nodes in a urban environment, is
also investigated. A more analytic approach, mainly using tools from
stochastic geometry and Markov chains theory, is used to develop a
mathematical framework for the evaluation of the performance of
routing rules for DTNs.
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ZHANG, LINCHAO. "Reliable Communication in Wireless Networks." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2537290.
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Wireless communication systems are increasingly being used in industries and infrastructures since they offer significant advantages such as cost effectiveness and scalability with respect to wired communication system. However, the broadcast feature and the unreliable links in the wireless communication system may cause more communication collisions and redundant transmissions. Consequently, guaranteeing reliable and efficient transmission in wireless communication systems has become a big challenging issue. In particular, analysis and evaluation of reliable transmission protocols in wireless sensor networks (WSNs) and radio frequency identification system (RFID) are strongly required.
This thesis proposes to model, analyze and evaluate self-configuration algorithms in wireless communication systems. The objective is to propose innovative solutions for communication protocols in WSNs and RFID systems, aiming at optimizing the performance of the algorithms in terms of throughput, reliability and power consumption. The first activity focuses on communication protocols in WSNs, which have been investigated, evaluated and optimized, in order to ensure fast and reliable data transmission between sensor nodes. The second research topic addresses the interference problem in RFID systems. The target is to evaluate and develop precise models for accurately describing the interference among readers. Based on these models, new solutions for reducing collision in RFID systems have been investigated.
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Rosén, Anders. "Embedded Communication Channel for Node Communication in WDM Networks." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209167.
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Optical Transport Network is a set of Optical Network Elements (NE) connected by optical fiber links able to provide support for optical networking using Wavelength-Division Multiplexing (WDM). In order to be able to introduce link-level applications that require NE-to-NE communication in a packet-optical network, an embedded communication channel is needed. Examples of such applications are dual-ended protection, remote configurationand path trace. By implementing a NE-to-NE communication channel, the exchange of commands and information will allow for implementation of applications that will increase the data link stability in the network. The purpose of this work has been to prove the feasibility of such a channel. This thesis discusses the possibilities of implementing such a channel adjusted to Transmode's layer 1 products without causing disturbance inthe regular traffic or affecting any existing embedded communication. It also proves the channels function in a proof-of-concept manner by demonstrating a simple Path trace application run upon an implementation of the channel on hardware. The chosen solution is an Embedded Communication Channel driver intended to provide termination points for an Embedded Communication Channel (ECC), supervising the connectivity of the channel and relay messages to applications. This thesis project has been carried out at Infinera Corporation (earlier Transmode Systems AB) during summer/autumn 2015.
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Martina, Jean Everson. "Verification of security protocols based on multicast communication." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609650.
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Wells, Daniel David. "Network management for community networks." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1006587.
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Community networks (in South Africa and Africa) are often serviced by limited bandwidth network backhauls. Relative to the basic needs of the community, this is an expensive ongoing concern. In many cases the Internet connection is shared among multiple sites. Community networks may also have a lack of technical personnel to maintain a network of this nature. Hence, there is a demand for a system which will monitor and manage bandwidth use, as well as network use. The proposed solution for community networks and the focus within this dissertation, is a system of two parts. A Community Access Point (CAP) is located at each site within the community network. This provides the hosts and servers at that site with access to services on the community network and the Internet, it is the site's router. The CAP provides a web based interface (CAPgui) which allows configuration of the device and viewing of simple monitoring statistics. The Access Concentrator (AC) is the default router for the CAPs and the gateway to the Internet. It provides authenticated and encrypted communication between the network sites. The AC performs several monitoring functions, both for the individual sites and for the upstream Internet connection. The AC provides a means for centrally managing and effectively allocating Internet bandwidth by using the web based interface (ACgui). Bandwidth use can be allocated per user, per host and per site. The system is maintainable, extendable and customisable for different network architectures. The system was deployed successfully to two community networks. The Centre of Excellence (CoE) testbed network is a peri-urban network deployment whereas the Siyakhula Living Lab (SLL) network is a rural deployment. The results gathered conclude that the project was successful as the deployed system is more robust and more manageable than the previous systems.
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Li, Yingjie. "Information dissemination and routing in communication networks." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1132767756.
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Yuan, Fenghua. "Lightweight network management design for wireless sensor networks." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/F_Yuan_081307.pdf.
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Zhao, Li. "Enhance communication security in wireless ad hoc networks through multipath routing." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Summer2007/L_Zhao_072407.pdf.
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Dahlgren, Jeremy. "Efficient failure detection protocols for point-to-point communication networks /." Online version of thesis, 2004. https://ritdml.rit.edu/dspace/handle/1850/2752.
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Pompili, Dario. "Efficient Communication Protocols for Underwater Acoustic Sensor Networks." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16301.
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Underwater sensor networks find applications in oceanographic data collection, pollution monitoring, offshore exploration, disaster prevention, assisted navigation, tactical surveillance, and mine reconnaissance. The enabling technology for these applications is acoustic wireless networking. UnderWater Acoustic Sensor Networks (UW-ASNs) consist of sensors and Autonomous Underwater Vehicles (AUVs) deployed to perform collaborative monitoring tasks. The objective of this research is to explore fundamental key aspects of underwater acoustic communications, propose communication architectures for UW-ASNs, and develop efficient sensor communication protocols tailored for the underwater environment. Specifically, different deployment strategies for UW-ASNs are studied, and statistical deployment analysis for different architectures is provided. Moreover, a model characterizing the underwater acoustic channel utilization efficiency is introduced. The model allows setting the optimal packet size for underwater communications. Two distributed routing algorithms are proposed for delay-insensitive and delay-sensitive applications. The proposed routing solutions allow each node to select its next hop, with the objective of minimizing the energy consumption taking the different application requirements into account. In addition, a resilient routing solution to guarantee survivability of the network to node and link failures in long-term monitoring missions is developed. Moreover, a distributed Medium Access Control (MAC) protocol for UW-ASNs is proposed. It is a transmitter-based code division multiple access scheme that incorporates a novel closed-loop distributed algorithm to set the optimal transmit power and code length. It aims at achieving high network throughput, low channel access delay, and low energy consumption. Finally, an efficient cross-layer communication solution tailored for multimedia traffic (i.e., video and audio streams, still images, and scalar sensor data) is introduced.
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Sandström, Adam, and Nico Klerks. "Evaluation of 6TiSCH network performance for SDN-enabled IoT networks." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-48819.
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Within the Internet of Things (IoT) a need for new IP-compatible communication technologies has grown stronger during the last few years as the need to connect these IoT networks to the Internet has become increasingly more important. In this report, we evaluate IPv6 over the TSCH mode of IEEE 802.15.4e (6TiSCH) with the purpose of observing how different values for the enhanced beacon (EB) period affect certain network metrics such as delay, energy consumption, join time, and throughput. The EB period is a periodic message used in the Time Slotted Channel hopping (TSCH) protocol used to advertise the network. Our goal is to evaluate the effect of different EB periods on the network and determine if there would be a benefit of integrating SDN to change the EB period dynamically. To fulfill our goal, we will evaluate the effect of the change in EB period on the network metrics. This would be an indication that the 6TiSCH network benefits from an integration with SDN. The reason that we would draw this conclusion is because SDN would be capable of predicting the state of the network and from that update the EB period for the 6TiSCH network. Our results indicate that a lower EB period has a positive effect on join times in the network while a longer EB period has a positive effect on the end-to-end delay. Our results display a promising future for future research on the integration of SDN and 6TiSCH.
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Chitedze, Zimani. "Mobility management for Wi-Fi infrastructure and mesh networks." University of the Western Cape, 2012. http://hdl.handle.net/11394/2960.
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Magister Scientiae - MScThis thesis shows that mobility management protocols for infrastructure Internet may be used in a wireless mesh network environment. In this research Mobile IPv6 and Fast Handover for Hierarchical Mobile IPv6 are successfully implemented in a wireless mesh network environment. Two experiments were carried out: vertical and horizontal handover simulations. Vertical handover simulation involved a heterogeneous wireless environment comprising both wireless local area and wireless mesh networks. An OPNET Mobile IPv6 model was used to simulate the vertical handover experiment. Horizontal handover simulation involved Mobile IPv6 and Fast Handover for Hierarchical Mobile IPv6 applied in ns2 wireless mesh network. The vertical handover results show that MIPv6 is able to manage vertical handover between wireless local area and wireless mesh network. The horizontal handover results illustrate that in mesh networks, Fast Handover for Hierarchical Mobile IPv6's performance is superior to Mobile IPv6. Fast Handover for Hierarchical Mobile IPv6 generates more throughput and less delay than Mobile IPv6. Furthermore, Fast Handover for Hierarchical Mobile IPv6 drops less data packets than Mobile IPv6. The simulations indicate that even though there are multi-hop communications in wireless mesh networks, the performance of the multi-hop routing may not play a big role in the handover performance. This is so because the mesh routers are mostly static and the multi-hop routes are readily available. Thus, the total handover delay is not affected too much by the WMN hops in the paths for signaling message transmission.
South Africa
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Ahmadvand, Nima. "Wavelength division multiplexing cross connect networks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30066.pdf.
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Al-Yatama, Anwar. "Quantization and routing in broadband networks." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/15374.
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Kanjani, Khushboo. "Supporting fault-tolerant communication in networks." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3118.
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Kalalas, Charalampos. "Cellular networks for smart grid communication." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/620760.
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The next-generation electric power system, known as smart grid, relies on a robust and reliable underlying communication infrastructure to improve the efficiency of electricity distribution. Cellular networks, e.g., LTE/LTE-A systems, appear as a promising technology to facilitate the smart grid evolution. Their inherent performance characteristics and well-established ecosystem could potentially unlock unprecedented use cases, enabling real-time and autonomous distribution grid operations. However, cellular technology was not originally intended for smart grid communication, associated with highly-reliable message exchange and massive device connectivity requirements. The fundamental differences between smart grid and human-type communication challenge the classical design of cellular networks and introduce important research questions that have not been sufficiently addressed so far. Motivated by these challenges, this doctoral thesis investigates novel radio access network (RAN) design principles and performance analysis for the seamless integration of smart grid traffic in future cellular networks.
Specifically, we focus on addressing the fundamental RAN problems of network scalability in massive smart grid deployments and radio resource management for smart grid and human-type traffic. The main objective of the thesis lies on the design, analysis and performance evaluation of RAN mechanisms that would render cellular networks the key enabler for emerging smart grid applications.
The first part of the thesis addresses the radio access limitations in LTE-based networks for reliable and scalable smart grid communication. We first identify the congestion problem in LTE random access that arises in large-scale smart grid deployments. To overcome this, a novel random access mechanism is proposed that can efficiently support real-time distribution automation services with negligible impact on the background traffic. Motivated by the stringent reliability requirements of various smart grid operations, we then develop an analytical model of the LTE random access procedure that allows us to assess the performance of event-based monitoring traffic under various load conditions and network configurations. We further extend our analysis to include the relation between the cell size and the availability of orthogonal random access resources and we identify an additional challenge for reliable smart grid connectivity. To this end, we devise an interference- and load-aware cell planning mechanism that enhances reliability in substation automation services. Finally, we couple the problem of state estimation in wide-area monitoring systems with the reliability challenges in information acquisition. Using our developed analytical framework, we quantify the impact of imperfect communication reliability in the state estimation accuracy and we provide useful insights for the design of reliability-aware state estimators.
The second part of the thesis builds on the previous one and focuses on the RAN problem of resource scheduling and sharing for smart grid and human-type traffic. We introduce a novel scheduler that achieves low latency for distribution automation traffic while resource allocation is performed in a way that keeps the degradation of cellular users at a minimum level. In addition, we investigate the benefits of Device-to-Device (D2D) transmission mode for event-based message exchange in substation automation scenarios. We design a joint mode selection and resource allocation mechanism which results in higher data rates with respect to the conventional transmission mode via the base station. An orthogonal resource partition scheme between cellular and D2D links is further proposed to prevent the underutilization of the scarce cellular spectrum.
The research findings of this thesis aim to deliver novel solutions to important RAN performance issues that arise when cellular networks support smart grid communication.Las redes celulares, p.e., los sistemas LTE/LTE-A, aparecen como una tecnología prometedora para facilitar la evolución de la próxima generación del sistema eléctrico de potencia, conocido como smart grid (SG). Sin embargo, la tecnología celular no fue pensada originalmente para las comunicaciones en la SG, asociadas con el intercambio fiable de mensajes y con requisitos de conectividad de un número masivo de dispositivos. Las diferencias fundamentales entre las comunicaciones en la SG y la comunicación de tipo humano desafían el diseño clásico de las redes celulares e introducen importantes cuestiones de investigación que hasta ahora no se han abordado suficientemente. Motivada por estos retos, esta tesis doctoral investiga los principios de diseño y analiza el rendimiento de una nueva red de acceso radio (RAN) que permita una integración perfecta del tráfico de la SG en las redes celulares futuras. Nos centramos en los problemas fundamentales de escalabilidad de la RAN en despliegues de SG masivos, y en la gestión de los recursos radio para la integración del tráfico de la SG con el tráfico de tipo humano. El objetivo principal de la tesis consiste en el diseño, el análisis y la evaluación del rendimiento de los mecanismos de las RAN que convertirán a las redes celulares en el elemento clave para las aplicaciones emergentes de las SGs. La primera parte de la tesis aborda las limitaciones del acceso radio en redes LTE para la comunicación fiable y escalable en SGs. En primer lugar, identificamos el problema de congestión en el acceso aleatorio de LTE que aparece en los despliegues de SGs a gran escala. Para superar este problema, se propone un nuevo mecanismo de acceso aleatorio que permite soportar de forma eficiente los servicios de automatización de la distribución eléctrica en tiempo real, con un impacto insignificante en el tráfico de fondo. Motivados por los estrictos requisitos de fiabilidad de las diversas operaciones en la SG, desarrollamos un modelo analítico del procedimiento de acceso aleatorio de LTE que nos permite evaluar el rendimiento del tráfico de monitorización de la red eléctrica basado en eventos bajo diversas condiciones de carga y configuraciones de red. Además, ampliamos nuestro análisis para incluir la relación entre el tamaño de celda y la disponibilidad de recursos de acceso aleatorio ortogonales, e identificamos un reto adicional para la conectividad fiable en la SG. Con este fin, diseñamos un mecanismo de planificación celular que tiene en cuenta las interferencias y la carga de la red, y que mejora la fiabilidad en los servicios de automatización de las subestaciones eléctricas. Finalmente, combinamos el problema de la estimación de estado en sistemas de monitorización de redes eléctricas de área amplia con los retos de fiabilidad en la adquisición de la información. Utilizando el modelo analítico desarrollado, cuantificamos el impacto de la baja fiabilidad en las comunicaciones sobre la precisión de la estimación de estado. La segunda parte de la tesis se centra en el problema de scheduling y compartición de recursos en la RAN para el tráfico de SG y el tráfico de tipo humano. Presentamos un nuevo scheduler que proporciona baja latencia para el tráfico de automatización de la distribución eléctrica, mientras que la asignación de recursos se realiza de un modo que mantiene la degradación de los usuarios celulares en un nivel mínimo. Además, investigamos los beneficios del modo de transmisión Device-to-Device (D2D) en el intercambio de mensajes basados en eventos en escenarios de automatización de subestaciones eléctricas. Diseñamos un mecanismo conjunto de asignación de recursos y selección de modo que da como resultado tasas de datos más elevadas con respecto al modo de transmisión convencional a través de la estación base. Finalmente, se propone un esquema de partición de recursos ortogonales entre enlaces celulares y D2
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Akkor, Gün. "Multicast communication support over satellite networks." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2452.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Barros, João. "Reachback communication in wireless sensor networks." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973065753.
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Forss, Jonas. "Real-Time Communication over Broadcast Networks." Thesis, University of Skövde, Department of Computer Science, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-308.
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Today the utilization of all kind of multimedia services in networks increases and due to this demand for real-time communication gets higher for every day. One of the most common protocols used today is Ethernet. It is of interest to find real-time protocols that are useful together with already existing protocols since it is expensive to rebuild the network infrastructure. Several new protocols have been proposed to solve the upcoming problems.
The objective of this project is to make an inventory and a comparison between Ethernet and these new protocols. During this project four different protocols capability to fulfill the demands for real-time communication have been studied and compared with Ethernet. Three of the protocols are built on the same basic technique as Ethernet and these are PCSMA, CSMA-DCR and DOD-CSMA-CD. The fourth protocol is ATM and it transmits in a different way over communication networks.
The analysis of this project is pointing out advantages, similarities and differences between the protocols from a real-time perspective. All four protocols are more suitable for real-time requirements than Ethernet.
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Wittie, Mike P. "Towards Sustainable Scalability of Communication Networks." UNIVERSITY OF CALIFORNIA, SANTA BARBARA, 2012. http://pqdtopen.proquest.com/#viewpdf?dispub=3482054.
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Demircan, Ahmet Emrah. "Routing Optimization Methods For Communication Networks." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605908/index.pdf.
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This study discusses the routing optimization techniques and algorithms for communication networks. Preventing data loss on overloaded communication links and utilizing link bandwidths efficiently are the main problems of traffic engineering. Load balancing and routing problems are solved using both by heuristics such as genetic algorithms, and simulation techniques. These algorithms work on destination-based or flow-based routing techniques and mainly change the link weight system or try to select the best routes set upon K-routes routing table respectively to optimize network utilization. In this study, first a definition of the network routing optimization problem will be made. Then the heuristics to solve the problem will be discussed and finally an analysis of these heuristics will be made on sample network models. This thesis includes a discussion about the performance of different optimization heuristics working as a part of the centralized network load balancing systems.
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Yi, Na. "Cooperative communication for future cellular networks." Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/843080/.
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Cellular networks are multi-user communication systems that consist of three basic elements: interference, cooperation, and feedback. A fundamental goal of multi-user systems research is to find out the capacity limit and its achievability of a general model that consists of many senders, receivers, and intermediate nodes. In the past 60 years, a huge amount of research efforts have been paid towards five special problems of multi-user systems: multiple-access channel, broadcast channel, relay channel, crosstalk channel, and feedback channel. Although most of those problems have not received a satisfactory answer yet, rapid development of cellular networks have motivated communication-theoretic research about cooperation in those special channels. The primary objective of this thesis is to study the cooperation theory in relay and crosstalk channels. The overall organisation of this thesis is based on our new vision about cooperative behaviour in communication networks. This new vision indicates that cooperative behaviour in relay and crosstalk networks can be classified into three groups, namely. Postman, Host, and Synergy. The classification is based on how a cooperative node utilises the multi-user side information such as channel quality information (CQI), codebook, message, in various communication scenarios. Specifically, major contributions of this thesis are summarised as follows. The Postman describes cooperative behaviour in relay networks, where a cooperative node offers cooperation by delivering other's message to its desired destination. Our first work in this category is about doubly differential cooperative relaying scheme proposed for mobile communication over rapidly time-varying channel. It is shown that the proposed scheme can enjoy full cooperative diversity-gain without need of full channel state information. The other work in this category is about adaptive bit-power allocation for orthogonal frequency-division multiplexing (OFDM)-based relay networks. Provided full knowledge of CQI, a number of sub-optimum approaches have been proposed to improve the power efficiency through multi-link optimisation. The Host describes cooperative behaviour in cognitive interference networks, where a primary user offers cooperation to a secondary user by opening its own spectrum and sharing knowledge of side information. The work in this category is about overlay and underlay cognitive radio channels, where the primary user broadcasts its private codebook and knowledge of CQI, so that the secondary user can perceive the primary user's message and interference state. Capacity theorem of two-user Gaussian cognitive interference channels have been carefully investigated, based on which power allocation and spectrum access approaches have been proposed in terms of power and spectrum efficiency. The Synergy describes cooperative behaviour in crosstalk channels. A typical example is the cooperative bit-power allocation between two individual transmitter-receiver pairs. One cooperative behaviour is sharing of codebook and CQI between two transmitter-receiver pairs. The purpose of sharing is to maximize their common profit and to allow an optimal treatment of mutual interference. Provided full knowledge of multi-user CQI at transmitters, two transmitter-receiver pairs first perform iterative rate-adaptation to maximize the sum-rate, and then employ proportional fairness for rate allocation.
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Dogan, Safak. "Video transcoding for multimedia communication networks." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843006/.
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Video transcoding is a generic name for a video gateway structure whereby the tandeming process does not involve any high complexity cascaded decoding and re-encoding operations in contrast to the existing conventional solutions. Diverse multimedia communication network characteristics, such as bandwidth limitations and varying congestion conditions, incur quality degradation in video transmissions. The matching of input and output network constraints and characteristics is possible with video transcoding at a centralised unit within the network. Moreover, video transcoding also provides a suitable translation mechanism for different video compression standards achieving a transparent interconnection between diverse network topologies. In addition, video transcoding offers a method for providing robustness against transmission error effects which occur during the transmission of compressed video streams over highly bandwidth- restricted communication media, such as popular mobile-wireless networks. Due to the severe bandwidth restrictions of such networks, the video signals require low bit rate coding which in turn renders video streams highly susceptible to radio channel errors. Therefore, error-resilient operations also need to be provided together with the syntax and transmission rate translation features of video transcoders. The unique features of video transcoding provide flexible and efficient ways to alleviate the previously addressed three major issues for various requirements. These requirements can be imposed by the diversity of networks on which numerous applications are running or by different standards themselves as well as by a wide range of users. This is strictly related to a universal interoperability issue of heterogeneous characteristics and requirements which demand effective end-to-end solutions. Thus, the aim of this research presented in this thesis is to develop algorithms for the provision of such remedial solutions to the interoperability problem. In the light of these facts, the research work focuses on the design of various video transcoding algorithms. The objectives of these algorithms are to ease network congestion and/or user bandwidth limitation conditions, support essential standard conversions between different compression schemes and provide necessary error robustness over highly error-prone transmission media, such as mobile radio networks. The ultimate target is to establish a common platform where all the above three aims are successfully satisfied. Extensive computer simulations demonstrate the effectiveness of the proposed and designed systems, throughout the course of the research work. These simulations are assessed with the use of objective and subjective performance measures.
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Angus, Simon Douglas Economics Australian School of Business UNSW. "Economic networks: communication, cooperation & complexity." Awarded by:University of New South Wales. Economics, 2007. http://handle.unsw.edu.au/1959.4/27005.
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This thesis is concerned with the analysis of economic network formation. There are three novel sections to this thesis (Chapters 5, 6 and 8). In the first, the non-cooperative communication network formation model of Bala and Goyal (2000) (BG) is re-assessed under conditions of no inertia. It is found that the Strict Nash circle (or wheel) structure is still the equilibrium outcome for n = 3 under no inertia. However, a counter-example for n = 4 shows that with no inertia infinite cycles are possible, and hence the system does not converge. In fact, cycles are found to quickly dominate outcomes for n > 4 and further numerical simulations of conditions approximating no inertia (probability of updating > 0.8 to 1) indicate that cycles account for a dramatic slowing of convergence times. These results, together with the experimental evidence of Falk and Kosfeld (2003) (FK) motivate the second contribution of this thesis. A novel artificial agent model is constructed that allows for a vast strategy space (including the Best Response) and permits agents to learn from each other as was indicated by the FK results. After calibration, this model replicates many of the FK experimental results and finds that an externality exploiting ratio of benefits and costs (rather than the difference) combined with a simple altruism score is a good proxy for the human objective function. Furthermore, the inequity aversion results of FK are found to arise as an emergent property of the system. The third novel section of this thesis turns to the nature of network formation in a trust-based context. A modified Iterated Prisoners' Dilemma (IPD) model is developed which enables agents to play an additional and costly network forming action. Initially, canonical analytical results are obtained despite this modification under uniform (non-local) interactions. However, as agent network decisions are 'turned on' persistent cooperation is observed. Furthermore, in contrast to the vast majority of non-local, or static network models in the literature, it is found that a-periodic, complex dynamics result for the system in the long-run. Subsequent analysis of this regime indicates that the network dynamics have fingerprints of self-organized criticality (SOC). Whilst evidence for SOC is found in many physical systems, such dynamics have been seldom, if ever, reported in the strategic interaction literature.
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Brunet, Richard. "Temporal alarm correlation in communication networks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0004/MQ32426.pdf.
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Ren, Kui. "Communication security in wireless sensor networks." Worcester, Mass. : Worcester Polytechnic Institute, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-040607-174308/.
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Bean, Nigel Geoffrey. "Statistical multiplexing in broadband communication networks." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282808.
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Waters, A. Gill. "Multi-party communication over packet networks." Thesis, University of Essex, 1996. http://kar.kent.ac.uk/21390/.
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The majority of applications running over packet networks involve point-to-point working. Over the last few years, there has been growing interest in applications involving multiple participants and, increasingly, where these participants are all simultaneously involved in the communication. This interest has strengthened with the introduction of the MBone (the Internet multicasting backbone) and with the range of services made possible by ATM and those envisaged for Broadband ISDN. This thesis discusses the potential for a wide variety of multi-party applications. It examines their detailed requirements and the support mechanisms needed to meet these requirements. The work is presented as a dissertation and a collection of work published over a period of about ten years and as such draws together work on multi-party communication undertaken by the author and postgraduate students under her supervision. The major contribution of the thesis and the most recent work concerns multicast routing strategies capable of supporting high-bandwidth delay sensitive applications. A new heuristic is introduced which is shown to offer efficient routing solutions whilst ensuring that delays to each participant are kept within a bound. The heuristic is reasonably simple and is shown to perform well under a variety of conditions. The chapters of the these leading up to the work on multicast routing present the earlier published work. Architectural frameworks are presented which extend existing protocol reference models to offer multicast support mechanisms at appropriate hierarchical levels with a view to flexible yet efficient use of the network. One important support mechanism is group management and a system developed in the context of an integrated services network is described. This comprises a group management database together with a collection of flexible group management procedures capable of supporting a wide variety of applications.
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Shirshekar, Hossna. "Reliable communication in cognitive radio networks." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44940.
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The emergence of new wireless applications has driven increased demand for radio spectrum and therefore, the fixed spectrum assignment approach cannot efficiently utilize the radio spectrum. On the other side, several researches show that there are many parts of the licensed spectrum bands that are left unused most of the time. To address the problem of limited spectrum resources and underutilization of the radio spectrum resource, cognitive radio was used to make it possible for secondary users to opportunistically access the underutilized radio spectrum bands. However, in comparison with the general wireless network, cognitive radio technology gives invaders more possibilities to influence the wireless networks. This makes it more challenging to guarantee reliable communication in cognitive radio networks.
In this thesis, first we describe the cognitive radio, cognitive radio networks, and security threats in these networks. Then the concepts of spectrum sensing as well as cooperative spectrum sensing are presented.
There are two important kinds of security threats in the cognitive radio networks, which have attracted considerable attention in the literature. The first kind of threat which is called primary user mimicry invasion includes the cognitive radios or some outsiders that try to emulate the primary user’s signal characteristics in order to interrupt the spectrum sensing process. In the second kind of invasion, known as spectrum sensing data distortion invasion, the disruption of the spectrum sensing process is caused by those cognitive radios that send false data to the fusion center.
Primary user mimicry invasion and spectrum sensing data distortion invasion have been majorly focused on in the past researches. Considering the significance of these two kinds of security threats in the ways in which they have disturbing effects on the overall performance of the cognitive radio networks, I focus my research work on these two kinds of threats. Then I provide a survey of the state of the art detection and mitigation techniques against them. The shortcomings associated with some of these detection and mitigation techniques are also investigated, which can be used as starting points for future researches.
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Abdul-Reda, A. J. "Simulation performance studies of communication networks." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377714.
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