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Cross-layer design of admission control policies in code division multiple access communications systems utilizing beamformingSheng, Wei 07 August 2008 (has links)
To meet growing demand for wireless access to multimedia traffic, future generations of wireless networks need to provide heterogenous services with high data rate and guaranteed quality-of-service (QoS). Many enabling technologies to ensure QoS
have been investigated, including cross-layer admission control (AC), error control and congestion control.
In this thesis, we study the cross-layer AC problem. While previous research focuses on single-antenna systems, which does not
capitalize on the significant benefits provided by multiple antenna
systems, in this thesis we investigate cross-layer AC policy for a code-division-multiple-access (CDMA) system with antenna arrays at the base station (BS). Automatic retransmission request (ARQ)
schemes are also exploited to further improve the spectral efficiency.
In the first part, a circuit-switched network is considered and an exact outage probability is developed, which is then employed to derive the optimal call admission control (CAC) policy by formulating a constrained semi-Markov decision process (SMDP). The derived optimal policy can maximize the system throughput with
guaranteed QoS requirements in both physical and network layers.
In the second part, a suboptimal low-complexity CAC policy is
proposed based on an approximate power control feasibility condition (PCFC) and a reduced-outage-probability algorithm. Comparison between optimal and suboptimal CAC policies shows that the suboptimal CAC policy can significantly reduce the computational
complexity at a cost of degraded performance.
In the third part, we extend the above research to packet-switched networks. A novel SMDP is formulated by incorporating ARQ protocols. Packet-level AC policies are then
proposed. The proposed policies exploit the error control capability provided by ARQ schemes, while simultaneously
guaranteeing QoS requirements in the physical and packet levels.
In the fourth part, we propose a connection admission control policy
in a connection-oriented packet-switched network, which can guarantee QoS requirements in physical, packet and connection levels. By considering joint optimization across different layers,
the proposed optimal policy provides a flexible way to handle multiple QoS requirements, while at the same time, maximizing the overall system throughput. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2008-08-05 16:21:40.431
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A Microstructural Model for a Proton Exchange Membrane Fuel Cell Catalyst LayerBaker, CRAIG 08 September 2012 (has links)
This thesis presents a framework for a microstructural model of a catalyst layer in a proton exchange membrane (PEM) fuel cell. In this study, a stochastic model that uses individual carbon, platinum and ionomer particles as building blocks to construct a catalyst layer geometry, resulting in optimal porosity and material mass ratios has been employed. The construction rule set in this design is easily variable, enabling a wide range of catalyst layer geometries to be made. The generated catalyst layers were found to exhibit many of the features found in currently poduced catalyst layers. The resulting geometries were subsequently examined on the basis of electronic percolation, mean chord length and effective diffusivity of the pore phase. Catalyst layer percolation was found to be most effected by the number of carbon see particles used and the specified porosity. The mean chord lengths of all of the catalyst layer geometries produced Knudsen numbers ranging in order of magnitude between 0.1 and 10, thus indicating that gas diffusion within the catalyst layers lies in the transition regime between bulk and Knudsen diffusion. Calculated effective diffusivities within the pore space of the model were shown to be relatively insensitive to changes in the catalyst layer composition and construction rule set other then porosity, indicating that the pore size distribution does not significantly vary when the catalyst layer mass ratios vary. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-08-31 08:52:55.747
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Metal Oxide Processing on Gallium Nitride and Silinovon Hauff, Peter A Unknown Date
No description available.
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Atomic Layer Deposition of Metal Oxide Thin Films on Metallic SubstratesForoughi Abari, Ali Unknown Date
No description available.
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Heat and mass transfer in combined convection.Crotogino, Reinhold Hermann. January 1971 (has links)
No description available.
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Finite amplitude waves in a model boundary layerBalagondar, Puttappa Mallappa. January 1981 (has links)
No description available.
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Ozone maxima off the East Coast of South Africa : the role of biomass burning.Pillay, Yogesveri. January 1993 (has links)
No abstract available. / Thesis (M.Sc.)-University of Natal, Durban, 1993.
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Aerodynamic interactions between bodies in relative motionSchreiber, Olivier 08 1900 (has links)
No description available.
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Investigation of chemically reacting boundary layers in solid propellant rockets : steady and periodic solutionsSrivastava, Rajiva 05 1900 (has links)
No description available.
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Effects of cavity dimensions, boundary layer, and temperature on cavity noise generation and controlMendoza, Jeffrey Michael 12 1900 (has links)
No description available.
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