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MITIGATING MISBEHAVIOR IN WIRELESS NETWORKS: A GAME THEORETIC APPROACH
Title
MITIGATING MISBEHAVIOR IN WIRELESS NETWORKS: A GAME THEORETIC APPROACH.
Creator
Wang, Wenjing, Chatterjee, Mainak, University of Central Florida
Abstract / Description
In a distributed wireless system, multiple network nodes behave cooperatively towards a common goal. Though such assumptions on cooperation are desirable (e.g., controlling the transmit power level, reducing interference for each other, revealing private information, adhering to network policies) for analyzing and modeling, certain nodes belonging to a real-world system have often shown to deviate. These nodes, known as misbehaving nodes, bring more challenges to the design of the wireless...
Show moreIn a distributed wireless system, multiple network nodes behave cooperatively towards a common goal. Though such assumptions on cooperation are desirable (e.g., controlling the transmit power level, reducing interference for each other, revealing private information, adhering to network policies) for analyzing and modeling, certain nodes belonging to a real-world system have often shown to deviate. These nodes, known as misbehaving nodes, bring more challenges to the design of the wireless network because the unreliable channel makes the actions of the nodes hidden from each other. In this dissertation, we analyze two types of misbehavior, namely, selfish noncooperation and malicious attacking. We apply game theoretic techniques to model the interactions among the nodes in the network. First, we consider a homogeneous unreliable channel and analyze the necessary and sufficient conditions to enforce cooperative packet forwarding among a node pair. We formulate an anti-collusion game and derive the conditions that achieve full cooperation when the non-cooperative nodes collude. In addition, we consider multi-hop communication with a heterogeneous channel model. We refine our game model as a hidden action game with imperfect private monitoring. A state machine based strategy is proposed to reach Nash Equilibrium. The strategy attains cooperative packet forwarding with heterogeneous channel and requires only partial and imperfect information. Furthermore, it also enforces cooperation in multi-hop packet forwarding. To tackle the malicious attacks, we use Bayesian game analysis to show the existence of equilibrium in the detection game and argue that it might not be profitable to isolate the malicious nodes upon detection. We propose the concept of "coexistence with malicious nodes" by proving the co-existence equilibrium and derive the conditions that achieve the equilibrium. This research is further accomplished by extensive simulation studies. Simulation results illustrate the properties of the games and the derived equilibria. The results validate our design philosophy and clearly indicate that the proposed game theoretic solutions can be effectively used to enforce cooperation and mitigate attacks.
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Date Issued
2010
Identifier
CFE0003080, ucf:48294
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003080
SPECTRUM SHARING AND SERVICE PRICING IN DYNAMIC SPECTRUM ACCESS NETWORKS
Title
SPECTRUM SHARING AND SERVICE PRICING IN DYNAMIC SPECTRUM ACCESS NETWORKS.
Creator
Brahma, Swastik, Chatterjee, Mainak, University of Central Florida
Abstract / Description
Traditionally, radio spectrum has been statically allocated to wireless service providers (WSPs). Regulators, like FCC, give wireless service providers exclusive long term licenses for using specific range of frequencies in particular geographic areas. Moreover, restrictions are imposed on the technologies to be used and the services to be provided. The lack of flexibility in static spectrum allocation constrains the ability to make use of new technologies and the ability to redeploy the...
Show moreTraditionally, radio spectrum has been statically allocated to wireless service providers (WSPs). Regulators, like FCC, give wireless service providers exclusive long term licenses for using specific range of frequencies in particular geographic areas. Moreover, restrictions are imposed on the technologies to be used and the services to be provided. The lack of flexibility in static spectrum allocation constrains the ability to make use of new technologies and the ability to redeploy the spectrum to higher valued uses, thereby resulting in inefficient spectrum utilization [23, 38, 42, 62, 67]. These limitations have motivated a paradigm shift from static spectrum allocation towards a more 'liberalized' notion of spectrum management in which secondary users can borrow idle spectrum from primary spectrum licensees, without causing harmful interference to the latter- a notion commonly referred to as dynamic spectrum access (DSA) or open spectrum access ,. Cognitive radio [30, 47], empowered by Software Defined Radio (SDR), is poised to promote the efficient use of spectrum by adopting this open spectrum approach. In this dissertation, we first address the problem of dynamic channel (spectrum) access by a set of cognitive radio enabled nodes, where each node acting in a selfish manner tries to access and use as many channels as possible, subject to the interference constraints. We model the dynamic channel access problem as a modified Rubinstein-Stahl bargaining game. In our model, each node negotiates with the other nodes to obtain an agreeable sharing rule of the available channels, such that, no two interfering nodes use the same channel. We solve the bargaining game by finding Subgame Perfect Nash Equilibrium (SPNE) strategies of the nodes. First, we consider finite horizon version of the bargaining game and investigate its SPNE strategies that allow each node to maximize its utility against the other nodes (opponents). We then extend these results to the infinite horizon bargaining game. Furthermore, we identify Pareto optimal equilibria of the game for improving spectrum utilization. The bargaining solution ensures that no node is starved of channels. The spectrum that a secondary node acquires comes to it at a cost. Thus it becomes important to study the 'end system' perspective of such a cost, by focusing on its implications. Specifically, we consider the problem of incentivizing nodes to provide the service of routing using the acquired spectrum. In this problem, each secondary node having a certain capacity incurs a cost for routing traffic through it. Secondary nodes will not have an incentive to relay traffic unless they are compensated for the costs they incur in forwarding traffic. We propose a path auction scheme in which each secondary node announces its cost and capacity to the routing mechanism, both of which are considered as private information known only to the node. We design a route selection mechanism and a pricing function that can induce nodes to reveal their cost and capacity honestly (making our auction truthful), while minimizing the payment that needs to be given to the nodes (making our auction optimal). By considering capacity constraint of the nodes, we explicitly support multiple path routing. For deploying our path auction based routing mechanism in DSA networks, we provide polynomial time algorithms to find the optimal route over which traffic should be routed and to compute the payment that each node should receive. All our proposed algorithms have been evaluated via extensive simulation experiments. These results help to validate our design philosophy and also illustrate the effectiveness of our solution approach.
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Date Issued
2011
Identifier
CFE0004049, ucf:49125
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004049
THE NATURE OF TURBULENCE IN A NARROW APEX ANGLE ISOSCELES TRIANGULAR DUCT
Title
THE NATURE OF TURBULENCE IN A NARROW APEX ANGLE ISOSCELES TRIANGULAR DUCT.
Creator
Krishnan, Vaidyanathan, Kapat, Jayanta, University of Central Florida
Abstract / Description
An experimental investigation was performed to ascertain the nature of turbulence in a narrow apex angle isosceles triangular duct. The study involved the design and construction of a low noise, low turbulence wind tunnel that had an isosceles triangular test section with an apex angle of 11.5°. Experiments involved the measurement of velocity fluctuations using hot wire anemometry and wall pressure fluctuations using a condenser microphone. Measurement of the velocity fluctuations...
Show moreAn experimental investigation was performed to ascertain the nature of turbulence in a narrow apex angle isosceles triangular duct. The study involved the design and construction of a low noise, low turbulence wind tunnel that had an isosceles triangular test section with an apex angle of 11.5°. Experiments involved the measurement of velocity fluctuations using hot wire anemometry and wall pressure fluctuations using a condenser microphone. Measurement of the velocity fluctuations reconfirms the coexistence of laminar and turbulent regions at a given cross section for a range of Reynolds numbers. The laminar region is concentrated closer to the apex while the turbulent region is found closer to the base. The point of transition is a function of the Reynolds number and moves closer to the apex as the flow rate is increased. Moreover, it was found in this investigation that traditional scaling of the turbulent statistical quantities do not hold good in this geometry. Although velocity fluctuations showed distinctive flow regimes, no such distinction could be seen in the dynamic wall pressure data. The nature of the dynamic wall pressure was uniform throughout the entire cross section suggesting that wall pressure fluctuations, unlike the velocity fluctuations, are able to travel from the base to the apex, without being damped. This implies that the relationship between the velocity and the pressure fluctuations applicable in the other systems does not hold well in a narrow apex angle isosceles triangular duct. Further, the typical scaling relationships applied to wall pressure spectra of other geometries doesn't apply in this scenario and the ratio of the RMS pressure fluctuation to the mean shear is much higher compared to a flat plate or pipe flow situation.
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Date Issued
2007
Identifier
CFE0001955, ucf:47471
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001955
A modeling framework of brittle and ductile fractures coexistence in composites
Title
A modeling framework of brittle and ductile fractures coexistence in composites.
Creator
Qiao, Yangyang, Bai, Yuanli, Gou, Jihua, Kassab, Alain, Gordon, Ali, An, Linan, University of Central Florida
Abstract / Description
In order to reduce the weight of automobiles and aircrafts, lightweight materials, such as aluminum alloy, advanced high strength steel, composite materials, are widely used to replace the traditional materials like mild steel. Composite materials are complicated in material mechanical properties and less investigated compared to metallic materials. Engineering composites can be categorized into polymer matrix composites (PMCs), metal matrix composites (MMCs) and ceramic matrix composites ...
Show moreIn order to reduce the weight of automobiles and aircrafts, lightweight materials, such as aluminum alloy, advanced high strength steel, composite materials, are widely used to replace the traditional materials like mild steel. Composite materials are complicated in material mechanical properties and less investigated compared to metallic materials. Engineering composites can be categorized into polymer matrix composites (PMCs), metal matrix composites (MMCs) and ceramic matrix composites (CMCs) according to their matrix materials.A set of mechanical experiments ranging from micro scale (single fiber composite and thin film composite) to macro scale (PMCs and MMCs) were conducted to fully understand the material behavior of composite materials. Loading conditions investigated includes uniaxial tension, three-point bending, uniaxial compression, simple shear, tension combined with shear, and compression combined with shear.For single fiber composite and thin-film composite, details of each composition are modelled. For the PMCs and MMCs which have plenty of reinforcements like fibers and particles, the details of the composition of structures cannot be modelled due to the current limitations of computing power. A mechanics framework of composite materials including elasticity, plasticity, failure initiation and post failure softening is proposed and applied to two types of composite materials.Uniaxial tension loading is applied to several single fiber composites and thin film composites. A surprising phenomenon, controllable and sequential fragmentation of the brittle fiber to produce uniformly sized rods along meters of polymer cladding, rather than the expected random or chaotic fragmentation, is observed with a necking propagation process. A combination of necking propagation model, fiber cracking model and interfacial model are proposed and applied to the finite element simulations. Good predictions of necking propagation and uniform fragmentation phenomenon are achieved. This modeling method of the micro-scale phenomenon reveals the physics inside composites in micro scale and helps the understanding of the process of nano fragmentation.Unidirectional carbon fiber composites were tested under multi-axial loading conditions including tensile/compression/shear loadings along and perpendicular to the fiber direction. Compression dominated tests showed a brittle fracture mode like local kicking/buckling, while tension dominated tests showed a fracture mode like delamination and fiber breakage. Simple shear tests with displacement control showed matrix material hardening and softening before total failure. The proposed modeling framework is successfully applied to the PMCs. A new parameter ? was introduced to represent different loading conditions of PMCs. Numerical simulations using finite element method well duplicated the anisotropic elasticity and plasticity of this material. Failure features like delamination was simulated using cohesive surface feature. It is also applied to carbon fiber composite laminates to further validate the proposed model.A round of experimental study on high volume fraction of metallic matrix nano composites was conducted, including uniaxial tension, uniaxial compression, and three-point bending. The example materials were two magnesium matrix composites reinforced with 10 and 15% vol. SiC particles (50nm size). Brittle fracture mode was exhibited under uniaxial tension and three-point bending, while shear dominated ductile fracture mode (up to 12% fracture strain) was observed under uniaxial compression. Transferring the Modified Mohr Coulomb (MMC) ductile fracture model to the stress based MMC model (sMMC), the proposed modeling framework is applied to this material. This model has been demonstrated to be capable of predicting the coexistence of brittle and ductile fracture modes under different loading conditions for MMCs. Numerical simulations using finite element method well duplicated the material strength, fracture initiation sites and crack propagation modes of the Mg/SiC nano composites with a good accuracy.
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Date Issued
2018
Identifier
CFE0007078, ucf:51977
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007078