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Dissertations / Theses on the topic 'Broadcast routing'
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王慧霞 and Wai-ha Wong. "Efficient algorithms for broadcast routing." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31214733.
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Wong, Wai-ha. "Efficient algorithms for broadcast routing /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18565402.
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Chen, Jinze. "Broadcast routing and scheduling of ad hoc networks." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/6993.
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Arumugam, Rajkumar. "SCRIBE self-organized contention and routing in intelligent broadcast environments /." Cincinnati, Ohio : University of Cincinnati, 2002. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1024331160.
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ARUMUGAM, RAJKUMAR. "SCRIBE: SELF-ORGANIZED CONTENTION AND ROUTING IN INTELLIGENT BROADCAST ENVIRONMENTS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1024331160.
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Lee, Kok Thong. "Performance analysis of Mobile Ad Hoc Networking routing protocols /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FLee%5Kok.pdf.
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Bani, Khalaf Mustafa. "Dynamic probabilistic routing discovery and broadcast schemes for high mobility ad-hoc networks." Thesis, Edinburgh Napier University, 2013. http://researchrepository.napier.ac.uk/Output/6151.
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Mobile Ad-hoc Networks (MANETs) have lately come to be widely used in everyday applications. Their usability and capability have attracted the interest of both commercial organizations and research communities. Recently, the Vehicular Ad-hoc Network (VANET) is a promising application of MANETs. It has been designed to offer a high level of safety for the drivers in order to minimize a number of roads accidents. Broadcast communication in MANETs and VANETs, is essential for a wide range of important services such as propagating safety messages and Route REQuest (RREQ) packets. Routing is one of the most challenging issues in MANETs and VANETs, which requires high efficient broadcast schemes. The primitive and widely deployed method of implementing the broadcast is simple ‘flooding'. In this approach, each node ‘floods' the network, with the message that it has received, in order to guarantee that other nodes in the network have been successfully reached. Although flooding is simple and reliable, it consumes a great deal of network resources, since it swamps the network with many redundant packets, leading to collisions contention and huge competition, while accessing the same shared wireless medium. This phenomenon is well-known in MANETs, and is called the Broadcast Storm Problem. The first contribution of this thesis is to design and develop an efficient distributed route discovery scheme that is implemented based on the probabilistic concept, in order to suppress the broadcast storm problem. The proposed scheme is called a Probabilistic Disturbed Route Discovery scheme (PDRD), and it prioritizes the routing operation at each node with respect to different network parameters such as the number of duplicated packets, and local and global network density. The performance of the proposed scheme PDRD has been examined in MANETs, in terms of a number of important metrics such as RREQ rebroadcast number and RREQ collision number. Experimental results confirm the superiority of the proposed scheme over its counterparts, including the Hybrid Probabilistic-Based Counter (HPC) scheme and the Simple Flooding (SF) scheme. The second contribution of this thesis is to tackle the frequent link breakages problem in MANETs. High mobility nodes often have frequent link breakages; this potentially leads to re-discovery of the same routes. Although different probabilistic solutions have been suggested to optimize the routing in MANETs, to the best of our knowledge they have not focused on the problem of frequent link breakages and link stability. II Unlike other existing probabilistic solutions, this thesis proposes a new Velocity Aware-Probabilistic (VAP) route discovery scheme, which can exclude unstable nodes from constructing routes between source and destination. The main idea behind the proposed schemes is to use velocity vector information to determine the stable nodes and unstable nodes. A proper rebroadcast probability and timer are set dynamically according to the node stability. Simulation results confirm that the new proposed scheme has much better performance in terms of end-to-end delay, RREQ rebroadcast number and link stability. The routing in VANETs is very critical and challenging in terms of the number of broken links and packet overheads. This is mainly due to the fast vehicles' speed and different vehicles' movement directions. A large number of routing protocols such as Ad-hoc On-demand Distance Vector (AODV) and Dynamic Source Routing (DSR) have been proposed to deal with the routing in MANETs. However, these protocols are not efficient and cannot be applied directly to VANETs context due to its different characteristics. Finally toward this end, this thesis proposes new probabilistic and timer probabilistic routing schemes in order to improve the routing in VANETs. The main aim of the proposed schemes is to set up the most stable routes to avoid any possible link breakage. These schemes also enhance the overall network performance by suppressing the broadcast storm problem, which occurs during the route discovery process. The proposed schemes also make AODV protocol suitable and applicable for VANETs. Simulation results show the benefit of the new routing schemes in terms of a number of metrics such as RREQ rebroadcast number, link stability and end-to-end delay.
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Ke, Kai-Wei. "State reduction and state-dependent call admission and routing in multirate communications networks." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/13922.
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Lai, Shouwen. "Duty-Cycled Wireless Sensor Networks: Wakeup Scheduling, Routing, and Broadcasting." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/27333.
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In order to save energy consumption in idle states, low duty-cycled operation is widely used in Wireless Sensor Networks (WSNs), where each node periodically switches between sleeping mode and awake mode. Although efficient toward saving energy, duty-cycling causes many challenges, such as difficulty in neighbor discovery due to asynchronous wakeup/sleep scheduling, time-varying transmission latencies due to varying neighbor discovery latencies, and difficulty on multihop broadcasting due to non-simultaneous wakeup in neighborhood. This dissertation focuses on this problem space. Specifically, we focus on three co-related problems in duty-cycled WSNs: wakeup scheduling, routing and broadcasting.
We propose an asynchronous quorum-based wakeup scheduling scheme, which optimizes heterogenous energy saving ratio and achieves bounded neighbor discovery latency, without requiring time synchronization. Our solution is based on quorum system design. We propose two designs: cyclic quorum system pair (cqs-pair) and grid quorum system pair (gqs-pair). We also present fast offline construction algorithms for such designs. Our analytical and experimental results show that cqs-pair and gqs-pair achieve better trade-off between the average discovery delay and energy consumption ratio. We also study asymmetric quorum-based wakeup scheduling for two-tiered network topologies for further improving energy efficiency.
Heterogenous duty-cycling causes transmission latencies to be time-varying. Hence, the routing problem becomes more complex when the time domain must be considered for data delivery in duty-cycled WSNs. We formulate the routing problem as time-dependent Bellman-Ford problem, and use vector representation for time-varying link costs and end-to-end (E2E) distances. We present efficient algorithms for route construction and maintenance, which have bounded time and message complexities in the worst case by ameliorating with beta-synchronizer.
Multihop broadcast is complex in duty-cycled WSNs due to non simultaneous wakeup in neighborhoods. We present Hybrid-cast, an asynchronous multihop broadcast protocol, which can be applied to low duty-cycling or quorum-based duty-cycling schedules, where nodes send out a beacon message at the beginning of wakeup slots. Hybrid-cast achieves better tradeoff between broadcast latency and broadcast count compared to previous broadcast solutions. It adopts opportunistic data delivery in order to reduce the broadcast latency. Meanwhile, it reduces redundant transmission via delivery deferring and online forwarder selection. We analytically establish the upper bound of broadcast count and the broadcast latency under Hybrid-cast.
To verify the feasibility, effectiveness, and performance of our solutions for asynchronous wakeup scheduling, we developed a prototype implementation using Telosb and TinyOS 2.0 WSN platforms. We integrated our algorithms with the existing protocol stack in TinyOS, and compared them with the CSMA mechanism. Our implementation measurements illustrate the feasibility, performance trade-off, and effectiveness of the proposed solutions for low duty-cycled WSNs.Ph. D.
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Whisman, Daniel Montgomery. "Benefits of opportunistic routing, implicit acknowledgments, and network coding on a linear broadcast network." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105956.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 69-72).
This thesis studies the benefits of using opportunistic routing, implicit acknowledgments, and network coding on a linear broadcast packet network. Nodes are arranged in a line, and the first node wishes to communicate with the end node. When node i transmits, it is received at node j with a probability Pi,j . Several communication protocols are proposed and their performance studied using the mean and variance of the completion time as metrics. The protocols studied use end-to-end retransmission, end-to-end coding, and link-by-link retransmission with network coding both with and without opportunistic routing. Simulation and analytical results are presented. End-to-end coding significantly outperforms end-to-end retransmission on both metrics, and the link-by-link protocols outperform both. Opportunistic routing shows a mixed benefit over link-by-link protocols without it. When using opportunistic routing, the variance of the completion time is higher, and the mean is either similar or lower, depending on the channel conditions. When the loss probabilities are higher, opportunistic routing shows little benefit, whereas with a lower probability of packet loss, opportunistic routing shows a significant reduction in mean completion time.al Engineering and Computer Science.
by Daniel Montgomery Whisman.
S.M.
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Adamek, Jordan Matthew. "Concurrent Geometric Routing." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1501087573328402.
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Khan, Shariq Mahmood. "Reliable on-demand routing protocols for mobile ad-hoc networks." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11627.
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Mobile Ad-Hoc Network (MANET) facilitates the creation of dynamic reconfigurable networks, without centralized infrastructure. MANET routing protocols have to face high challenges like link instability, node mobility, frequently changing topologies and energy consumption of node, due to these challenges routing becomes one of the core issues in MANETs. This Thesis mainly focuses on the reactive routing protocol such as Ad-Hoc On-Demand Distance Vector (AODV) routing protocol. Reliable and Efficient Reactive Routing Protocol (RERRP) for MANET has been proposed to reduce the link breakages between the moving nodes. This scheme selects a reliable route using Reliability Factor (RF); the RF considers Route Expiration Time and Hop Count to select a routing path with high reliability and have less number of hops. The simulation result shows that RERRP outperforms AODV and enhance the packet delivery fraction (PDF) by around 6% and reduces the network routing load (NRL) by around 30%. Broadcasting in MANET could cause serious redundancy, contention, and collision of the packets. A scheme, Effective Broadcast Control Routing Protocol (EBCRP) has been proposed for the controlling of broadcast storm problem in a MANET. The EBCRP is mainly selects the reliable node while controlling the redundant re-broadcast of the route request packet. The proposed algorithm EBCRP is an on-demand routing protocol, therefore AODV route discovery mechanism was selected as the base of this scheme. The analysis of the performance of EBCRP has revealed that the EBCRP have controlled the routing overhead significantly, reduces it around 70% and enhance the packet delivery by 13% as compared to AODV. An Energy Sensible and Route Stability Based Routing Protocol (ESRSBR) have also been proposed that mainly focuses on increasing the network lifetime with better packet delivery. The ESRSBR supports those nodes to participate in the data transfer that have more residual energy related to their neighbour nodes. The proposed protocol also keeps track of the stability of the links between the nodes. Finally, the ESRSBR selects those routes which consist of nodes that have more residual energy and have stable links. The comparative analysis of ESRSBR with AODV and recently proposed routing protocol called Link Stability and Energy Aware (LSEA) routing protocol revealed that the proposed protocol ESRSBR has a significantly affect the network lifetime, increases it around 10% and 13% as compared to LSEA and AODV protocols respectively. The ESRSBR also decreases the routing overhead by 22% over LSEA and by 38% over AODV.
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Thong, Lee Kok. "Performance analysis of mobile ad hoc networking routing protocols." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1225.
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Approved for public release, distribution is unlimitedThis thesis presents a simulation and performance evaluation analysis of the various routing protocols that have been proposed for the Mobile Ad Hoc Network (MANET) environment using the Network Simulator-2 (NS-2) tool. Many routing protocols have been proposed by the academic communities for possible practical implementation of a MANET in military, governmental and commercial environments. Four (4) such routing protocols were chosen for analysis and evaluation: Ad Hoc On-demand Distance Vector routing (AODV), Dynamic Source Routing (DSR), Destination-Sequenced Distance Vector routing (DSDV) and Optimized Link State Routing (OLSR). NS-2 is developed and maintained by the University of Southern California's Information Sciences Institute (ISI). Leveraging on NS-2's simulation capabilities, the key performance indicators of the routing protocols were analyzed such as data network throughput, routing overhead generation, data delivery delay as well as energy efficiency or optimization. The last metric is explored, especially due to its relevance to the mobile environment. Energy is a scare commodity in a mobile ad hoc environment. Any routing software that attempts to minimize energy usage will prolong the livelihood of the devices used in the battlefield. Three important mobility models are considered, namely, Random Waypoint, Manhattan Grid, and Reference Point Group Mobility. The application of these three models will enhance the realism of simulation to actual real life mobility in an urban or military setup scenario. The performance of the routing protocols in varied node density, mobility speed as well as loading conditions have been studied. The results of the simulation will provide invaluable insights to the performance of the selected routing protocols. This can serve as a deciding factor for the U.S. Department of Defense (DoD) in their selection of the most suitable routing protocols tailored to their specific needs.
Civilian, Defence Science Technology Agency, Singapore
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Khan, Faisal Ahmad. "Safety-message routing in vehicular ad hoc networks." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47743.
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The safety-message dissemination problem for vehicular ad hoc networks (VANETs) was investigated. Four novel techniques were contributed for the efficient and reliable routing of safety messages in the vehicular ad hoc networks. The instant-broadcast technique was proposed to improve the end-to-end dissemination delay. The lane-based sectoring mechanism was presented for the collision mitigation in the dense-urban traffic scenario. The negative acknowledgment with smart neighborhood (NSN) technique was proposed to ensure the reliability of reception through recovering the packet loss caused by interference. Finally, the negative acknowledgment with smart neighborhood - hole recovery (NSN-H) technique was presented to provide guaranteed reception of the safety message at each individual node in the VANET. The investigation of the safety message routing in VANET conducted in this research also revealed the significance of hitherto-neglected factors that influence the vehicular network. Significance of the small payload size of the VANET safety message, the effect of road width on the multi-hop relay, and the attenuation caused by vehicles in the propagation path were among the important revealed factors.
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Brown, Darren Jacob. "A NOVEL MESSAGE ROUTING LAYER FOR THE COMMUNICATION MANAGEMENT OF DISTRIBUTED EMBEDDED SYSTEMS." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/41.
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Fault tolerant and distributed embedded systems are research areas that have the interest of such entities as NASA, the Department of Defense, and various other government agencies, corporations, and universities. Taking a system and designing it to work in the presence of faults is appealing to these entities as it inherently increases the reliability of the deployed system. There are a few different fault tolerant techniques that can be implemented in a system design to handle faults as they occur. One such technique is the reconfiguration of a portion of the system to a redundant resource. This is a difficult task to manage within a distributed embedded system because of the distributed, directly addressed data producer and consumer dependencies that exist in common network infrastructures. It is the goal of this thesis work to develop a novel message routing layer for the communication management of distributed embedded systems that reduces the complexity of this problem. The resulting product of this thesis provides a robust approach to the design, implementation, integration, and deployment of a distributed embedded system.
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Aymak, Onur. "Ad Hoc Packet Routing Simulation And Tactical Picture Display Tool For Navy." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605266/index.pdf.
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The importance of communication is vital in wartime. The capability of having all the position information of the allied and enemy forces in a single Tactical Information Display System (TIDS), maintains a great advantage for deciding what to do before the enemy reacts. A Naval Information Distributing System (NIDS) is developed for building an effective communication infrastructure between the war ships. In the designed network, besides the mobile platforms (ships), some fixed platforms (land stations) are used to transfer the information coming from these mobile platforms to all the other platforms. To demonstrate the performance and effectiveness of the Naval Information Distribution System, a discrete event simulation model is developed on a Geographic Information System. The goal of this thesis is to describe and experimentally evaluate an effective and feasible information sharing and routing system for Navy.
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Haggar, Bachar Salim. "Auto-organisation et routage dans les réseaux mobiles ad hoc." Thesis, Reims, 2011. http://www.theses.fr/2011REIMS036/document.
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Nos travaux se positionnent dans le cadre de l'algorithmique distribuée et plus particulièrement des réseaux ad hoc. Les réseaux ad hoc sont auto-organisés en permettant des échanges directs entre nœuds mobiles et ne reposent sur aucune infrastructure. Chaque nœud peut se déplacer librement et indépendamment des autres impliquant une modification perpétuelle de la topologie. Dans ce contexte, la probabilité que des défaillances surviennent dans le réseau est importante. Ces défaillances gênent le bon fonctionnement du réseau et peuvent même entrainer une paralysie de celui-ci. C'est pourquoi la conception de solutions pour de tels réseaux nécessitent des mécanismes de gestion de fautes. Parmi ceux-ci, l'approche d'auto-stabilisation permet à un système de gérer les fautes transitoires. Nous étendons cette approche pour répondre aux principaux problèmes liés à la mobilité des nœuds. Notre objectif est de répondre à un double besoin d'auto-organisation du réseau et d'optimisation du nombre de messages échangés. Notre approche consiste à découper le réseau en clusters afin de lui donner une structure hiérarchique. Cette dernière rend l'utilisation du réseau plus efficace et plus performante. L'algorithme que nous avons développé à cet effet est auto-stabilisant et n'est basé que sur des connaissances locales. Nous exploitons cette solution pour proposer deux utilisations efficaces : la diffusion d'informations dans le réseau et le routage. La diffusion d'informations exploite un arbre couvrant inter-clusters, construit sans surcoût, en parallèle de la clusterisation. Le routage quant à lui exploite cet arbre pour permettre à la fois d'optimiser le délai de bout en bout et le nombre de messages échangésOur work relies in the domain of distributed system, more preciselly ad hoc networks. Ad hoc networks are self-organized allowing direct exchanges between mobile nodes and do not rely on any infrastruture. Each node can move freely and independently of each others involving continuous topology variability. In this context, the probability that a failure occurs in the network is high. These failures hinder the proper functioning of the network and even causes its paralysis. Therefore, designing solutions for such networks requires fault management mechanisms. Among these, a self-stabilizating approach allows the system to withstand transient faults. We extend this approach to answer the problems induced by nodes mobility. We have two main objectives: a self-organizing network and optimizing number of exchanged messages. Our approach consists in dividing the network into clusters in order to give it a hierarchical structure. This solution allows a more efficient and effective network use. The algorithm that we developed for this purpose is a self-stabilizing algorithm based only on local informations. Based on this solution, we propose two efficient use cases: Information broadcast and a routing protocol. Information broadcast uses an inter-cluster spanning tree, generated without any overhead. In the same time as the clustering process. The routing protocol uses this tree for both round trip and number of exchanged messages optimization
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Rajendran, Rajapandiyan. "The Evaluation of GeoNetworking Forwarding in Vehicular Ad-Hoc Networks." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-23982.
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In Intelligent Transportation Systems (ITS), disseminating warning messages in a timely and efficient way through wireless short-range communications can save many lives and reduce traffic congestion. A geographical broadcast protocol provides data delivery to specified geographical areas, using multi-hop communications if needed. Among the main challenges for such protocols are forwarder selection and the reduction of the number of hops required to reach and cover the destination area. In this thesis we propose an efficient geographical broadcast protocol called Preferred and Contention Based Forwarding (PCBF) and evaluate it through simulations. PCBF uses a combination of contention-based forwarding and selecting preferred forwarders also found in other protocols like Emergency Message Dissemination for Vehicular Environments (EMDV). Since the preferred forwarder is allowed to immediately forward the packet (evading contention among other potential forwarders), this approach reduces end-to-end delays. Notable extensions of PCBF compared to EMDV are the use of direct negative acknowledgements in case of unnecessary rebroadcasts and the use of forwarders outside the target region. Our simulation results show that the PCBF protocol outperforms selected other protocols in terms of end-to-end delay, re-broadcast overhead and reliability in both sparse and dense networks.
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Breschi, Karla. "Optimisation multi-objectif des communications dans les réseaux de capteurs hétérogènes." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD045/document.
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Cette thèse étudie les problèmes d’optimisation bi-objectifs des communications dans les réseaux de capteurs hétérogènes du point de vue de la portée de transmission. Le premier critère considéré est nécessairement l'énergie qu’il s’agit d'économiser pour maximiser la durée de vie du réseau. Le second critère, primordial dans le cas des applications en temps réel, est le délai d'acheminement des données. Pour résoudre le problème d’optimalité de la diffusion, nous proposons une formulation en nombres entiers, un algorithme d’approximation, une méta-heuristique et une heuristique permettant de trouver ou s’approcher de l’optimal pour les objectifs considérés.Pour le cas du routage, nous proposons une approche cross-layer via un programme linéaire en nombre entiers entre les couches MAC et Liaison de données permettant de calculer l'optimal et ainsi d'avoir un point de comparaison pour les futures heuristiques ayant les mêmes objectifsThis thesis studies the problems of bi-objective optimization of communications in heterogeneous wireless sensor networks from the point of view of the transmission range. The first criterion considered is necessarily the energy consumption that needs to be reduced in order to maximize the network lifetime. The second criterion is the data transmission delay, which is essential for real-time applications.To solve the optimality problem of the broadcast, we propose an integer linear program, an approximation algorithm, a meta-heuristic and a heuristic. All these techniques allow us to find or to approximate the optimal solutions for the considered objectives.For the routing case, we propose a cross-layer approach via an integer linear program between the MAC and Data Link layers. Our method calculates the optimal solution, which represents a point of comparison for future heuristics having the same goals
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Pokorný, Karel. "Laboratorní scénáře objasňující základy komunikačních protokolů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-400947.
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The goal of this thesis was to design two complex scenarios with focus on different kinds of transmission in packet-switched networks. First scenario is about ARQ (Automatic Repeat Request) protocols. It consists of introduction to Stop-and-Wait, Go Back N and Selective Repeat protocols and their comparison. Second scenario compares unicast, multicast, broadcast and anycast transmission methods. Both scenarios use applications which can simulate particular methods or protocols. These applications along with virtual environments are used for demonstration of characteristics of these methods/protocols.
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Uznanski, Przemyslaw. "Large scale platform : Instantiable models and algorithmic design of communication schemes." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00878837.
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The increasing popularity of Internet bandwidth-intensive applications prompts us to consider followingproblem: How to compute efficient collective communication schemes on large-scale platform?The issue of designing a collective communication in the context of a large scale distributed networkis a difficult and a multi-level problem. A lot of solutions have been extensively studied andproposed. But a new, comprehensive and systematic approach is required, that combines networkmodels and algorithmic design of solutions.In this work we advocate the use of models that are able to capture real-life network behavior,but also are simple enough that a mathematical analysis of their properties and the design of optimalalgorithms is achievable.First, we consider the problem of the measuring available bandwidth for a given point-topointconnection. We discuss how to obtain reliable datasets of bandwidth measurements usingPlanetLab platform, and we provide our own datasets together with the distributed software usedto obtain it. While those datasets are not a part of our model per se, they are necessary whenevaluating the performance of various network algorithms. Such datasets are common for latencyrelatedproblems, but very rare when dealing with bandwidth-related ones.Then, we advocate for a model that tries to accurately capture the capabilities of a network,named LastMile model. This model assumes that essentially the congestion happens at the edgesconnecting machines to the wide Internet. It has a natural consequence in a bandwidth predictionalgorithm based on this model. Using datasets described earlier, we prove that this algorithm is ableto predict with an accuracy comparable to best known network prediction algorithm (DistributedMatrix Factorization) available bandwidth between two given nodes. While we were unable toimprove upon DMF algorithm in the field of point-to-point prediction, we show that our algorithmhas a clear advantage coming from its simplicity, i.e. it naturally extends to the network predictionsunder congestion scenario (multiple connections sharing a bandwidth over a single link). We areactually able to show, using PlanetLab datasets, that LastMile prediction is better in such scenarios.In the third chapter, we propose new algorithms for solving the large scale broadcast problem.We assume that the network is modeled by the LastMile model. We show that under thisassumption, we are able to provide algorithms with provable, strong approximation ratios. Takingadvantage of the simplicity and elasticity of the model, we can even extend it, so that it captures theidea of connectivity artifacts, in our case firewalls preventing some nodes to communicate directlybetween each other. In the extended case we are also able to provide approximation algorithmswith provable performance.The chapters 1 to 3 form three successful steps of our program to develop from scratch amathematical network communication model, prove it experimentally, and show that it can beapplied to develop algorithms solving hard problems related to design of communication schemesin networks.In the chapter 4 we show how under different network cost models, using some simplifyingassumptions on the structure of network and queries, one can design very efficient communicationschemes using simple combinatorial techniques. This work is complementary to the previous chapter in the sense that previously when designing communication schemes, we assumed atomicityof connections, i.e. that we have no control over routing of simple connections. In chapter 4 weshow how to solve the problem of an efficient routing of network request, given that we know thetopology of the network. It shows the importance of instantiating the parameters and the structureof the network in the context of designing efficient communication schemes.
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Zeitzmann, Hanko Kalle. "A Model of Non-Routine Organizational Search: Broadcast Search as an Alternative Knowledge-Sourcing Mechanism in the Pharmaceutical Industry." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19237.
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Combining Cyert and March\'s (1963) model of search with foundational concepts from evolutionary theory (Nelson & Winter, 1982), this dissertation scrutinizes the expansion of search and develops a refined framework for organizational search behavior. Special emphasis is put on the aspect of search in organizationally vulnerable areas (Cyert & March, 1963). Considering pressure to innovate as a potential driver, the dissertation develops a conceptual model based on open innovation (Chesbrough, 2003a). Three pre-studies and two main studies illuminate broadcast search in the pharmaceutical industry and test the theoretical model. The pre-studies elucidate the use of broadcast search in the pharmaceutical industry from various angles. One investigation uses public data from an intermediary to test for the uniqueness of pharma-related broadcast search. Findings indicate that pharma-related challenges are frequented less by solvers. Another pre-study administered surveys to managers from pharmaceutical firms interested in open innovation for R&D. Results indicate alignment between the academic literature and practice. The tenor of the pre-studies is that broadcast search in the pharmaceutical industry deserves legitimate consideration. Also, anecdotal evidence supports the notion that broadcast search, at current, is used after other attempts have failed"as a search mechanism at the margin.
The two main studies test the theoretically developed ideas. Building on prior work, study 1 singles out the breadth of the knowledge base as the defining factor for forming strategic knowledge groups. Study 2 supports the notion that innovation pressure is associated with changes in organizational search behavior. Since study 2 does not find a direct link between innovation pressure and broadcast search engagement, a post-hoc analysis follows which combines study 1 findings with study 2 data. Results support the idea that a broad knowledge base precedes broadcast search.
Theory development benefits from this dissertation by emphasizing on a better understanding of organizational search processes and setting a foundation for future investigations. For practitioners the dissertation cautions of blind adoption of broadcast search while at the same time pointing to its potential. Having supplemental capabilities becomes crucial. The nature of these capabilities requires further scientific investigation.
Ph. D.
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Ferreira, Nogueira Douglas. "Mobile-Based Early WarningSystems in Mozambique. : An exploratory study on the viability to integrate Cell Broadcast into disaster mitigation routines." Thesis, Uppsala universitet, Institutionen för informatik och media, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-378978.
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Mozambique is one of the countries most affected by natural hazards in the world. Therefore it can benefit greatly from enhancements on its early warning system. Cell broadcast, which is a technology able to send simultaneous alert messages to all mobile phones in a geographical area has gained attention of emergency authorities since various catastrophes in the years 2000’s and increasing diffusion of the mobile network. This research has looked into the disaster risk management routines in Mozambique, interviewing relevant institutions, to identify the currently in use early warning system and analyze the circuit of information from detecting a hazard until the transmission of alert messages to the population. The goal of this research has been to identify how alert messages are sent to the population and, based on currently available infrastructure, analyze the possibilities to use Cell Broadcast to target alerts to all subscribers on specific geographic zones. It has been identified that the country already uses a solution that sends SMS to a list of phone numbers registered in a database. Nonetheless, telecommunication operators in the country are willing to cooperate with emergency authorities to design a solution in which Cell Broadcast can be used to strategically target alerts to subscribers at designated areas of risk. In this way, enabling enhanced accuracy and efficiency of the public alert system in Mozambique, with reduced time between detection and the simultaneously delivery of public alert messages to the entire population or only to people located on relevant geographic zones. Furthermore, the results also allowed to speculate on the viability of automated solutions, which can be used in combination to the enhancements that Cell Broadcast can bring to disaster risk management routines.
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Tan, Chia-Lin, and 譚嘉林. "A Distributed Fail-Safe Broadcast Routing Protocol." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/14723719346994567369.
Full textAbstract:
碩士大同工學院
資訊工程研究所
81
Broadcast communication is the delivery of copies of message to all nodes in a network. Broadcast routing is defined to be the routing procedures by which broadcast data is transmitted overinherently nonbroadcast communication media. One of the most important considerations in broadcast routing design is reliability, which includes two issues: its ability to deliver exactly one copy of the packets to all nodes; and its ability to cope with topological changes. This paper prsents a distributed protocol that maintains a directed spanning tree (DST) at the broadcast source connecting to any node in the network. Using a DST, exactly one copy of the broadcast packets is delivered from the source to all nodes under normal operation. A DST quarantees minimum number of copies of the broadcast packets. Under arbitrary number, timing , and topology changes, a new spanning tree with minimum changes from old one is formed in finite time. Since each node, rather than the source,is responsible to maintain its own connectivity to the source, no central tables are required and there is no global knowledge of the topology or of the routes.
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Hsieh, Ming-Hsuan, and 謝明軒. "The Appropriate Forwarder Highway Emergency Broadcast Routing Protocol." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/12192039854070865502.
Full textAbstract:
碩士國立暨南國際大學
資訊工程學系
104
Recent years, Vehicular Ad hoc Network (VANET) is a popular research topic in Ad hoc Network and has attract considerable attention from both research community and automotive industry. Since IEEE 802.11p and IEEE 1609 standards have been adopted as the main technology in every country, vehicular safety application has played an important role in VANETs. Many emergency broadcast protocols had been proposed, but most of these schemes cannot solve hidden terminal and the redundancy. As the result, we proposed a protocol called Appropriate Forwarder Emergency Broadcast Routing Protocol (AFEB). AFEB uses the distance factor and periodical distance prediction to select the farthest and appropriate forwarder within the communication range to disseminate the emergency warning message (EWM). By the rebroadcast mechanism, AFEB ensures that all vehicles behind the accident car can receive EWM successfully. Also, pausing the broadcast of CAM within the communication range can avoid the packet collisions. In addition, the proposed method is implemented with NS2 simulator. The simulation results show that the proposed mechanism AFEB not only ensure the EWM reception ratio in each scenario but also reduce the End-to-End delay of dissemination and the number of EWM transmitted. AFEB also reduces the number of the collisions in any scenarios. Compared to other routing protocol, AFEB is able to perform better.
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Liu, Ning Han, and 劉寧漢. "Improved linear broadcast routing protocols for high speed networks." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/85014466905937065700.
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Wu, Cheng-Yu, and 巫承諭. "An Efficient Highway Emergency Broadcast Routing Protocol Based on Stability." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/12339937679356826610.
Full textAbstract:
碩士國立暨南國際大學
資訊工程學系
103
In recent year, Vehicular Ad hoc Network (VANET) is a significant research topic in Ad hoc Network. Since IEEE 802.11p and IEEE 1609 standards have been adopted as the main technology in US, EU and JP, vehicular safety application has played an important role in VANETs. There are many emergency broadcast protocols had been proposed, but most of these schemes could not improve hidden terminal and intense media contention problems efficiently. These problems will lead to rear drivers could not successfully receive emergency messages in time, and finally causes a serious chain reaction accident. Therefore, to make sure each vehicle can receive emergency packets, and avoiding the second accident. The proposed protocol called Appropriate Vehicular Emergency Dissemination (AVED), using stability to select the most stable forwarder in the transmission range to relay the emergency packet. After that, to allow rear drivers to take appropriate response, emergency messages must be quickly forwarded to shorten the latency. In addition, the proposed method is implemented with NS2 simulator based on WAVE/DSRC standard and having analysis of stability. The simulation results show that the proposed protocol has outstanding reception rate and delay time in any different highway environment.
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Hung, Chih-Chia, and 洪志佳. "Direction-Based Routing Strategy to Reduce Broadcast Storm in MANET." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/69022464608122152175.
Full textAbstract:
碩士國立政治大學
資訊科學學系
97
In MANET the nodes may move fast and unpredictable, this may cause the original set up route well broken. Adopt those Reactive Routing Protocols may not only cause seriously data delivery delay but also produce a large number of control packages (RREQ) thus reducing network capacity. This is known as Broadcast Storm Problem. In this thesis, we proposed a routing protocol, Directive Location-Aided Routing (DLAR), that helps to choose appropriate relay nodes (intermediate nodes) in MANET. DLAR considers the node movement direction factor in deciding a stable route. Relay node is considered to be the same movement direction as source node. The goal is to maintain longer path lifetime, and make the broken very close to the destination node. DLAR adopts AODV to discovery route and accelerate the route recovery using Local Repair mechanism. Simulations show that as the network loading is high, DLAR can increase the packet delivery ratio by 6% ~ 55 % and increase the bandwidth utility by 40%, reduce the largely broadcast storm probability, and reduce end-to-end delay by 20%.
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Shi, Jun-Bin, and 石俊彬. "Fault Tolerant Routing and Broadcast Algorithms for Binary Undirected de Bruijn Networks." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/94673116219079738151.
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Yen, Chia-Hung, and 顏嘉宏. "Broadcast Routing Algorithm Based on Minimum Cost Spanning Tree for Ad-Hoc Networks." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/43005471850723292378.
Full textAbstract:
碩士國立宜蘭大學
電子工程學系碩士班
96
For many wireless applications such as group conference and digital audio/video broadcast, it is necessary to send data to all devices that form an ad-hoc network. In this thesis, minimum cost broadcast routing (MCBR) and minimum cost broadcast routing with forbidden set (MCBRF) are proposed. We first formulate a new cost model for the underlying graph by considering the distance between nodes, the remaining battery energy, and battery discharge pattern at each node. A minimum cost broadcast routing (MCBR) based on minimum cost graph spanning is described. Then forbidden set is introduced into MCBR to obtain MCBRF. MMLE is modified from minimum longest edge (MLE). It removes the longest edge and replaces it with a pair of shorter links which may raise total route cost but decrease maximum energy consumption. The performance of the algorithms is investigated through extensive simulations and compared to several other routing methods. The results on a variety of topologies of different sizes indicate that the spanning tree constructed by MCBRF algorithm has more leaf nodes than BIP and MMLE. Although the broadcast trees constructed by MWIS and MCDS have more leaf nodes, they suffer serious drawbacks in terms of energy consumption. Also, MCBR and MCBRF generate spanning trees that select nodes with higher remaining battery capacity as relay nodes. Thus more robust broadcast routes are established. Compared to BIP and MMLE, MCBRF also enjoys longer bottleneck lifetime and shorter broadcast latency.
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Chen, Li-Sheng, and 陳立勝. "EOBDBR: An Efficient Optimum Branching-Based Distributed Broadcast Routing Algorithm for Wireless Ad Hoc Networks." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/66963739661790192007.
Full textAbstract:
碩士國立宜蘭大學
電子工程學系碩士班
98
Wireless ad hoc networks are in general characterized by dynamic topologies that do not have a fixed infrastructure. In addition, connectivity is maintained in a decentralized fashion through a form of multi-hop radio network. To this effect, wireless ad hoc networks with asymmetric link costs have been advocated as more realistic ones from a network modeling perspective. In this paper, we propose an Efficient Optimum Branching-based Distributed Broadcast Routing (EOBDBR) protocol for wireless ad hoc networks with asymmetric link costs, which makes use of local information exchange only. The proposed protocol contrasts with centralized routing protocols, in which link state and other relevant information are kept in the routing table of each node. It involves setting up link states, finding minimum in-edge, detecting cycles, re-weighting and breaking cycles. Through extensive simulations, our protocol is compared against four distributed broadcast routing protocols chosen as benchmarks. The performance metrics used are message overhead, total energy consumption, number of retransmitting nodes, network lifetime, and maximum hop count. The superiority of EOBDBR against the studied benchmark protocols is established with respect to the above-mentioned metrics.
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Chen, Zhi-Cheng, and 陳志誠. "A Study on high-performance power-aware group broadcast routing protocols in mobile ad hoc networks." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/33951117203068861990.
Full textAbstract:
碩士國立雲林科技大學
電機工程系碩士班
93
The battery power has always been one of the central issues of mobile ad hoc networks (MANETs). This is because the operation of a host on MANETs is subject to the constraint of its battery capacity and the speed of its power consumption. Designing effective power-aware routing protocols has become a hot research topic in recent years. The purpose of our present research project is to explore the minimum power group multicast/broadcast routing problem on a MANET. The problem arises because every member in a group has a communication request of transmitting its data packets to all the members of the group. This problem belongs to a category that deals with the asymmetric minimum power routing problem in unidirectional communication model, also known as the range assignment problem, in which the data transmission range of host is absolutely determined by its transmission power. Generally speaking, in MANETs, the approaches to design power-aware mechanisms fall into two types. One approach is conducted in terms of network lifetime. The other is conducted in terms of network’s total transmission power. In this paper, we will adopt the second one, namely minimum network’s total transmission power, as our approach. Furthermore, we consider that there will be some advantages by using a shared tree as the bases of power-aware routing protocols in a MANET. (1) A shared tree is accessible to each source host. (2) The time and memory space for each source host to calculate its own broadcast tree can be reduced. (3) In the process of communication, the network only needs to monitor this one shared tree. As a result, the control and error detections of packet transmissions become much easier. (4) The delay and delay variations associated with the data transmissions are easier to control. In view of the above-mentioned merits, we will adopt the group broadcast shared tree model in our investigation of the minimum power group broadcast routing problem. In other words, we will establish a shared tree so that every member in the group can make use of this broadcast shared tree in transmitting its data packets to other members of the group. Meanwhile, the total transmission power spent on this tree will be minimum. In this thesis, we will propose the heuristic algorithms and the approximation algorithm to find the sub-optimal solution for this problem, and use a mixed integer programming formula to generate the optimal soluton. Finally, we do the computer simulations to compare the performances among these three methods.
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Qadir, Junaid Computer Science & Engineering Faculty of Engineering UNSW. "Improving broadcast performance in multi-radio multi-channel multi-rate wireless mesh networks." 2008. http://handle.unsw.edu.au/1959.4/41214.
Full textAbstract:
This thesis addresses the problem of `efficient' broadcast in a multi-radio multi-channel multi-rate wireless mesh network (MR$^2$-MC WMN). In such a MR$^2$-MC WMN, nodes are equipped with multiple radio network interface cards, each tuned to an orthogonal channel, that can dynamically adjust transmission rate by choosing a modulation scheme appropriate for the channel conditions. We choose `broadcast latency', defined as the maximum delay between a packet's network-wide broadcast at the source and its eventual reception at all network nodes, as the `efficiency' metric of broadcast performance. The problem of constructing a broadcast forwarding structure having minimal broadcast latency is referred to as the `minimum-latency-broadcasting' (MLB) problem. While previous research for broadcast in single-radio single-rate wireless networks has highlighted the wireless medium's `\emph{wireless broadcast advantage}' (WBA); little is known regarding how the new features of MR$^2$-MC WMN may be exploited. We study in this thesis how the availability of multiple radio interfaces (tuned to orthogonal channels) at WMN nodes, and WMN's multi-rate transmission capability and WBA, might be exploited to improve the `broadcast latency' performance. We show the MLB problem for MR$^2$-MC WMN to be NP-hard, and resort to heuristics for its solution. We divide the overall problem into two sub-problems, which we address in two separate parts of this thesis. \emph{In the first part of this thesis}, the MLB problem is defined for the case of single-radio single-channel multi-rate WMNs where WMN nodes are equipped with a single radio tuned to a common channel. \emph{In the second part of this thesis}, the MLB problem is defined for MR$^2$-MC WMNs where WMN nodes are equipped with multiple radios tuned to multiple orthogonal channels. We demonstrate that broadcasting in multi-rate WMNs is significantly different to broadcasting in single-rate WMNs, and that broadcast performance in multi-rate WMNs can be significantly improved by exploiting the availability of multi-rate feature and multiple interfaces. We also present two alternative MLB broadcast frameworks and specific algorithms, centralized and distributed, for each framework that can exploit multiple interfaces at a WMN node, and the multi-rate feature and WBA of MR$^2$-MC WMN to return improved `broadcast latency' performance.
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Omar, Hassan Aboubakr. "Medium Access Control, Packet Routing, and Internet Gateway Placement in Vehicular Ad Hoc Networks." Thesis, 2014. http://hdl.handle.net/10012/8314.
Full textAbstract:
Road accidents represent a serious social problem and are one of the leading causes of human death and disability on a global scale. To reduce the risk and severity of a road accident, a variety of new safety applications can be realized through wireless communications among vehicles driving nearby each other, or among vehicles and especially deployed road side units (RSUs), a technology known as a vehicular ad hoc network (VANET). Most of the VANET-enabled safety applications are based on broadcasting of safety messages by vehicles or RSUs, either periodically or in case of an unexpected event, such as a hard brake or dangerous road condition detection. Each broadcast safety message should be successfully delivered to the surrounding vehicles and RSUs without any excess delay, which is one of the main functions of a medium access control (MAC) protocol proposed for VANETs. This thesis presents VeMAC, a new multichannel time division multiple access (TDMA) protocol specifically designed to support the high priority safety applications in a VANET scenario. The ability of the VeMAC protocol to deliver periodic and event-driven safety messages in VANETs is demonstrated by a detailed delivery delay analysis, including queueing and service delays, for both types of safety messages. As well, computer simulations are conducted by using MATLAB, the network simulator ns-2, and the microscopic vehicle traffic simulator VISSIM, in order to evaluate the performance of the VeMAC protocol, in comparison with the IEEE 802.11p standard and the ADHOC MAC protocol (another TDMA protocol proposed for ad hoc networks). A real city scenario is simulated and different performance metrics are evaluated, including the network goodput, protocol overhead, channel utilization, protocol fairness, probability of a transmission collision, and safety message delivery delay. It is shown that the VeMAC protocol considerably outperforms the existing MAC schemes, which have significant limitations in supporting VANET safety applications.
In addition to enhancing road safety, in-vehicle Internet access is one of the main applications of VANETs, which aims at providing the vehicle passengers with a low-cost access to the Internet via on-road gateways. This thesis presents a new strategy for deploying Internet gateways on the roads, in order to minimize the total cost of gateway deployment, while ensuring that a vehicle can connect to an Internet gateway (using multihop communications) with a probability greater than a specified threshold. This cost minimization problem is formulated by using binary integer programming, and applied for optimal gateway placement in a real city scenario. To the best of our knowledge, no previous strategy for gateway deployment has considered the probability of multihop connectivity among the vehicles and the deployed gateways. In order to allow a vehicle to discover the existence of an Internet gateway and to communicate with the gateway via multihops, a novel data packet routing scheme is proposed based on the VeMAC protocol. The performance of this cross-layer design is evaluated for a multichannel VANET in a highway scenario, mainly in terms of the end-to-end packet delivery delay. The packet queueing at each relay vehicle is considered in the end-to-end delay analysis, and numerical results are presented to study the effect of various parameters, such as the vehicle density and the packet arrival rate, on the performance metrics.
The proposed VeMAC protocol is a promising candidate for MAC in VANETs, which can realize many advanced safety applications to enhance the public safety standards and improve the safety level of drivers/passengers and pedestrians on roads. On the other hand, the proposed gateway placement strategy and packet routing scheme represent a strong step toward providing reliable and ubiquitous in-vehicle Internet connectivity.
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Ba, Amadou Adama. "Protocole de routage basé sur des passerelles mobiles pour un accès Internet dans les réseaux véhiculaires." Thèse, 2011. http://hdl.handle.net/1866/5306.
Full textAbstract:
La rapide progression des technologies sans fil au cours de ces dernières années a vu
naître de nouveaux systèmes de communication dont les réseaux véhiculaires. Ces réseaux
visent à intégrer les nouvelles technologies de l’information et de la communication dans le
domaine automobile en vue d’améliorer la sécurité et le confort sur le réseau routier. Offrir un accès Internet aux véhicules et à leurs occupants peut sans doute aider à anticiper
certains dangers sur la route tout en rendant plus agréables les déplacements à bord des véhicules. Le déploiement de ce service nécessite que des messages soient échangés entre les véhicules. Le routage constitue un élément crucial dans un réseau, car définissant la façon dont les différentes entités échangent des messages. Le routage dans les VANETS constitue un grand défi car ces derniers sont caractérisés par une forte mobilité entraînant une topologie très dynamique.
Des protocoles ont été proposés pour étendre Internet aux réseaux véhiculaires. Toutefois,
la plupart d’entre eux nécessitent un coût élevé de messages de contrôle pour
l’établissement et le maintien des communications. Ceci a pour conséquence la saturation de la bande passante entrainant ainsi une baisse de performance du réseau.
Nous proposons dans ce mémoire, un protocole de routage qui s’appuie sur des
passerelles mobiles pour étendre Internet aux réseaux véhiculaires. Le protocole prend en compte la mobilité des véhicules et la charge du réseau pour l’établissement et le maintien des routes.The fast progression of wireless technologies has motivated the emergence of new communications system called VANETS (Vehicular Adhoc Networks). VANETS enable vehicles on the roadway to communicate with each other and with road infrastructure using wireless capabilities. The applications of VANETS include improving safety and comfort on the road. For example, by providing Internet to vehicles, traveling can be safer and more comfortable. To provide Internet connectivity, messages need to be exchanged between the vehicles. However, it is hard to design an efficient routing protocol for connecting vehicles to Internet with a reasonable cost due to high mobility in VANETS. Although, several existing routing protocols have been proposed in the open literature to extend Internet to VANETS, they generate considerable overhead. This leads to unfairly consumption of bandwidth decreasing network performance. We design a routing protocol to connect vehicles to Internet through mobile gateways with the objective to make efficient use of the network bandwidth. Indeed, the protocol significantly reduces the communication overhead required to establish and maintain the routes relying on the mobility of the gateways and the network’s load.
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"Efficient routing schemes for multiple broadcasts in hypercubes." Massachusetts Institute of Technology, Laboratory for Information and Decision Systems, 1990. http://hdl.handle.net/1721.1/3182.
Full textAbstract:
George D. Stamoulis and John N. Tsitsiklis."February 1990/Revised June 1990."--Cover. Cover title.
Includes bibliographical references (p. 36-37).
Research supported by the NSF. ECS-8552419 Research supported by Bellcore, Inc. and Du Pont. Research supported by the ARO. DAAL03-86-K-0171 Research supported by a fellowship from the Vinton Hayes Fund.
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Sharifian, Shaham. "Signal design for multi-way relay channels." Thesis, 2016. http://hdl.handle.net/1828/7677.
Full textAbstract:
Today’s communication systems are in need of spectrally efficient and high throughput
techniques more than ever because of high data rate applications and the scarcity
and expense of bandwidth. To cope with increased data rate demands, more base
stations are needed which is not cost and energy efficient in cellular networks. It
has been shown that wireless relay networks can provide higher network throughput
and increase power efficiency with low complexity and cost. Furthermore, network
resources can be utilized more efficiently by using network coding in relay networks.
A wireless relay network in which multiple nodes exchange information with the
help of relay node(s) is called a multi-way relay channel (MWRC). MWRCs are
expected to be an integral part of next generation wireless standards. The main
focus of this dissertation is the investigation of transmission schemes in an MWRC to
improve the throughput and error performance. An MWRC with full data exchange
is assumed in which a half-duplex relay station (RS) is the enabler of communication.
One of the challenges with signal demodulation in MWRCs is the existence of
ambiguous points in the received constellation. The first part of this dissertation
investigates a transmission scheme for full data exchange in MWRC that benefits from
these points and improves its throughput by 33% compared to traditional relaying.
Then an MWRC is considered where a RS assists multiple nodes to exchange messages.
A different approach is taken to avoid ambiguous points in the superposition of
user symbols at the relay. This can be achieved by employing complex field network
coding (CFNC) which results in full data exchange in two communication phases.
CFNC may lead to small Euclidean distances between constellation points, resulting
in poor error performance. To improve this performance, the optimal user precoding
values are derived such that the power efficiency of the relay constellation is highest
when channel state information is available at the users. The error performance of
each user is then analyzed and compared with other relaying schemes.
Finally, focusing on the uplink of multi-way relay systems, the performance of an
MWRC is studied in which users can employ arbitrary modulation schemes and the
links between the users and the relay have different gains, e.g. Rayleigh fading. Analytical
expressions for the exact average pairwise error probability of these MWRCs
are derived. The probability density function (PDF) and the mean of the minimum
Euclidean distance of the relay constellation are closely approximated, and a tight
upper bound on the symbol error probability is developed.Graduate