Physical layer impact on wireless mobile ad-hoc network performance
Item
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Title
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Physical layer impact on wireless mobile ad-hoc network performance
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Identifier
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d_2009_2013:7e22fe64218d:10271
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identifier
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10310
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Creator
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Drini, Merlinda,
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Contributor
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Tarek Saadawi
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Date
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2009
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Language
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English
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Publisher
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City University of New York.
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Subject
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Electrical engineering | Communications | Computer | Networks | Wireless
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Abstract
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In this thesis, we propose performance optimization challenges of ad hoc networks using cross layer design. Due to size and mobility requirements of the nodes that make up these networks, the routing protocols employed often must deal with limited performance. Thus, it is necessary to consider models and constraints at multiple layers when we explore network performance limits. The formulations of these cross-layer problems are usually in very complex forms and are mathematically challenging.;We introduce effective mathematical tools that can model time varying wireless channels in a discrete time domain. These mathematical tools, known as Markov models, have been proved as very proficient way of modeling wireless communication parameters such as channel fading statistics and Bit Error Rate (BER) performance.;We start the analysis of wireless channel first using 2-state Markov model, which in spite of network performance enhancement, cannot be very efficient in all scenarios, since wireless channel characteristics dynamically change in time. Next we demonstrate that using higher order of Markov chains, it is possible to implement a more realistic channel. However, increasing the number of states increases the computational complexity. Thus, we use a 3-state Markov model of the wireless channel as a tradeoff between complexity and the performance.;We propose an optimal algorithm on how the physical layer channel state information can be translated into the QoS parameters in higher layers. Since a cross-layering between the physical layer and the routing protocol has been proven to be significant, we introduce a development of physical layer-constrained routing algorithm that switches between the best possible routes as a function of Signal to Noise Ratio (SNR). We explore cross-layer adaptation of the route selection to channel conditions, to optimize network throughput. We propose a physical layer aware routing that switches between the best possible routes as a function of SNR.;Furthermore, to improve the performance of wireless ad-hoc networks, we implement a new metric based on the channel SNR information and lifetime of the links, for optimal route discovery. Introducing this new parameter, called Link Lifetime (LLT), we show how we can reduce the control overhead by avoidance of frequent routes reestablishment, and realize sudden route maintenance in mobile ad hoc networks.;Finally using numerous simulations, we analyze the performance of an ad-hoc routing protocol. Our results indicate that employing this new metric of LLT and 3-state Markov chain model, we achieve more stabile routes, thus, dramatically improving the overall performance of a mobile ad-hoc network.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Engineering
