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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Non-cooperative beaconing control in vehicular ad hoc networks

Goudarzi, Forough January 2017 (has links)
The performance of many protocols and applications of Vehicular Ad hoc Networks (VANETs), depends on vehicles obtaining enough fresh information on the status of their neighbouring vehicles. This should be fulfilled by exchanging Basic Safety Messages (BSMs) also called beacons using a shared channel. In dense vehicular conditions, many of the beacons are lost due to channel congestion. Therefore, in such conditions, it is necessary to control channel load at a level that maximizes BSM dissemination. To address the problem, in this thesis algorithms for adaptation of beaconing to control channel load are proposed. First, a position-based routing protocol for VANETs is proposed and the requirement of adaptive beaconing to increase the performance of the protocol is indicated. The routing protocol is traffic-aware and suitable for city environments and obtains real-time traffic information in a completely ad hoc manner without any central or dedicated control, such as traffic sensors, roadside units, or information obtained from outside the network. The protocol uses an ant-based algorithm to find a route that has optimum network connectivity. Using information included in small control packets called ants, vehicles calculate a weight for every street segment that is proportional to the network connectivity of that segment. Ant packets are launched by vehicles in junction areas. To find the optimal route between a source and destination, a source vehicle determines the path on a street map with the minimum total weight for the complete route. The correct functionality of the protocol design has been verified and its performance has been evaluated in a simulation environment. Moreover, the performance of the protocol in different vehicular densities has been studied and indicated that in dense vehicular conditions the performance of the protocol degrades due to channel load created by uncontrolled periodic beaconing. Then, the problem of beaconing congestion control has been formulated as non-cooperative games, and algorithms for finding the equilibrium point of the games have been presented. Vehicles as players of the games adjust their beacon rate or power or both, based on the proposed algorithms so that channel load is controlled at a desired level. The algorithms are overhead free and fairness in rate or power or both rate and power allocation are achieved without exchanging excess information in beacons. Every vehicle just needs local information on channel load while good fairness is achieved globally. In addition, the protocols have per-vehicle parameters, which makes them capable of meeting application requirements. Every vehicle can control its share of bandwidth individually based on its dynamics or requirements, while the whole usage of the bandwidth is controlled at an acceptable level. The algorithms are stable, computationally inexpensive and converge in a short time, which makes them suitable for the dynamic environment of VANETs. The correct functionality of the algorithms has been validated in several high density scenarios using simulations.
2

Optimization of Cross-Layer Network Data based on Multimedia Application Requirements

Rahman, Tasnim 15 August 2019 (has links)
This thesis proposes a convex network utility maximization (NUM) problem that can be solved to optimize a cross-layer network based on user and system defined requirements for quality and link capacity of multimedia applications. The problem can also be converged to a distributed solution using dual decomposition. Current techniques do not address the changing system's requirements for the network in addition to the user's requirements for an application when optimizing a cross-layer network, but rather focus on optimizing a dynamic network to conform to a real-time application or for a specific performance. Optimizing the cross-layer network for the changing system and user requirements allows a more accurate optimization of the overall cross-layer network of any given multi-node, ad-hoc wireless application for data transmission quality and link capacity to meet overall mission demands.
3

Tvorba a uplatnění požadavků na nezbytné dodávky při přípravě na řešení krizových situací v podmínkách ORP / The creation and application requirements for the necessary supplies for the purposes of preparation for dealing with crisis situations under the conditions of a municipality with extended competence

KUBIŠTOVÁ, Ludmila January 2011 (has links)
This thesis deals with the necessary supplies in terms of municipalities with extended powers. Specifically, it focuses on the creation and application of the requirements for necessary supplies. The thesis is divided into a theoretical part and a practical one. The theoretical part of the thesis discusses the economic measures for crisis situations in general; it discusses the entities that deal with necessary supplies. The main role among these entities is played by the Administration of State Material Reserves. One of the objectives of the thesis is to map these entities. Another objective of the thesis is devoted to the analysis and evaluation of the creation and application of the requirements for necessary supplies in the preparation for dealing with crisis situations. This second objective is fulfilled in both the theoretical and practical parts. The practical part was carried out in the form of a questionnaire survey. The questionnaires were sent to the crisis entities of municipalities with extended powers in the South Bohemian Region and the Vysočina Region to enable comparison. These two regions are similar both in size and the number of municipalities with extended powers. These questionnaires helped to confirm the assumed hypothesis that municipalities with extended powers effectively create and apply the requirements for necessary supplies.

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