Efficient Spectrum Management for Mobile Ad Hoc Networks

The successful deployment of advanced wireless network applications for defense, homeland security, and public safety depends on the availability of relatively interference-free spectrum. Setup and maintenance of mobile networks for military and civilian first-response units often requires temporary allocation of spectrum resources for operations of finite, but uncertain, duration. As currently practiced, this is a very labor-intensive process with direct parallels to project management. Given the wide range of real-time local variation in propagation conditions, spatial distribution of nodes, and evolving technical and mission priorities current human-in-the loop conflict resolution approaches seem untenable. If the conventional radio regulatory structure is strictly adhered to, demand for spectrum will soon exceed supply. Software defined radio is one technology with potential to exploit local inefficiencies in spectrum usage, but questions regarding the management of such network have persisted for years. This dissertation examines a real-time spectrum distribution approach that is based on principles of economic utility and equilibrium among multiple competitors for limited goods in a free market. The spectrum distribution problem may be viewed as a special case of multi-objective optimization of a constrained resource. A computer simulation was developed to create hundreds of cases of local spectrum crowding, to which simultaneous perturbation simulated annealing (SPSA) was applied as a nominal optimization algorithm. Two control architectures were modeled for comparison, one requiring a local monitoring infrastructure and coordination ("top down") the other more market based ("bottom up"). The analysis described herein indicates that in both cases "hands-off" local spectrum management by trusted algorithms is not only feasible, but that conditions of entry for new networks may be determined a priori, with a degree of confidence described by relatively simple algebraic formulas

Simulating The Impact of Emissions Control on Economic Productivity Using Particle Systems and Puff Dispersion Model

A simulation platform is developed for quantifying the change in productivity of an economy under passive and active emission control mechanisms. The program uses object-oriented programming to code a collection of objects resembling typical stakeholders in an economy. These objects include firms, markets, transportation hubs, and boids which are distributed over a 2D surface. Firms are connected using a modified Prim’s Minimum spanning tree algorithm, followed by implementation of an all-pair shortest path Floyd Warshall algorithm for navigation purposes. Firms use a non-linear production function for transformation of land, labor, and capital inputs to finished product. A GA-Vehicle Routing Problem with multiple pickups and drop-offs is implemented for efficient delivery of commodities across multiple nodes in the economy. Boids are autonomous agents which perform several functions in the economy including labor, consumption, renting, saving, and investing. Each boid is programmed with several microeconomic functions including intertemporal choice models, Hicksian and Marshallian demand function, and labor-leisure model. The simulation uses a Puff Dispersion model to simulate the advection and diffusion of emissions from point and mobile sources in the economy. A dose-response function is implemented to quantify depreciation of a Boid’s health upon contact with these emissions. The impact of emissions control on productivity and air quality is examined through a series of passive and active emission control scenarios. Passive control examines the impact of various shutdown times on economic productivity and rate of emissions exposure experienced by boids. The active control strategy examines the effects of acceptable levels of emissions exposure on economic productivity. The key findings on 7 different scenarios of passive and active emissions controls indicate that rate of productivity and consumption in an economy declines with increased scrutiny of emissions from point sources. In terms of exposure rates, the point sources may not be the primary source of average exposure rates, however they significantly impact the maximum exposure rate experienced by a boid. Tightening of emissions control also negatively impacts the transportation sector by reducing the asset utilization rate as well as reducing the total volume of goods transported across the economy

Analysis of Operations Management Problems in Currency and Food Supply Chains

This dissertation is constituted of three essays addressing operational issues be- longing to two research domains including (i) Logistics and Supply Chain Management for Currency Supply Network and (ii) Facility Location and Capacity Optimization for Food Supply Chains. Minimum cost ow network model and mixed integer programming model (linear and nonlinear) are developed to analyze and optimize supply chains of banknotes, coins, and foods. Approaches developed are general and can easily be applied to other categories of supply chains under different settings around the world with appropriate modifications. The first domain comprises two essays with different scopes and objectives, in which two unique monetary supply chains with distinctive operations and governmental regulations are analyzed from both supply-side and demand-side perspectives. In the first essay, in order to improve the efficiency of the central bank's currency network in a large country, currency vaults are upgraded by expanding their capacities, and the sourcing of the updated currency network is optimized. This is the first study that analyzes a country's overall currency network's operations from the supply-side perspective. In the same domain, the second essay presents general models for analyzing the operational issues in the U.S. Coin Supply Chain. As the first study to view the U.S. Coin Supply Chain as a closed-loop/reverse supply chain, it investigates the supply chain from both supply-side and demand-side perspectives to increase efficiency and effectiveness in ordering, producing, packaging, distributing and managing inventory of coins. This essay provides efficient methods and guidelines for effectively managing the supply chain that can be implemented in practice. Belonging to the second domain, the third essay optimizes a food supply chain to assure food safety and provides suggestions to government agencies and private companies concerning where to locate new irradiation facilities with appropriate capacities strategically, how to source the demand of U.S. hubs from the supply of Mexican growing regions through irradiation facilities tactically, and how to efficiently transport fresh fruits imported from Mexico to the U.S. operationally

Energy price increases in developing countries : case studies of Colombia, Ghana, Indonesia, Malaysia, Turkey, and Zimbabwe

When domestic energy prices in developing countries fall below opportunity costs, price increases are recommended to conserve fiscal revenue and to ensure efficient use of resources. Using six case studies, the authors investigate the effect of energy price increases on the poor, inflation, growth, public revenues, and industrial competitiveness. The effect on household in various income classes depends on the energy commodity's share in the household budget and the price elasticity of demand. For energy as a whole (electricity and fuels, traditional and commercial), budget shares often decline with income. So in terms of income distribution, taxing energy is not ideal. But commercial fuel consumption increases greatly with income, so any subsidies applied will largely benefit nonpoor urban households. For each commercial energy source (electricity, kerosene, diesel, and gasoline) proportionate household spending will generally be lower, and some energy sources will be luxuries. In no instance does energy spending exceed 10 percent of the typical household budget for any income group. The effect on industry is generally modest, since cost shares for energy typically range from 0.5 to 3 percent (with typical value being 1.5). In addition, many industries are flexible enough to substitute when energy prices increase. Energy prices tended to increase in adjustment and liberalization programs, and industrial output usually increased even with the higher energy prices. This suggests that the effects of the price increase is modest compared with the effects of other changes in the environment. There are exceptions, of course, such as energy-intensive industries with limited possibilities for substitution. Estimating the effects on public deficits is straight-forward, even with uncertainty about demand elasticities: energy price increases reduce the drain on public resources significantly. It is harder to trace the effects on inflation and growth in national income. The effects on inflation will generally not be severe, and inflation may even be reduced in the intermediate to long run, through lowered public deficits. Income growth rates were generally higher after the years of energy price adjustments than they were in the years before the price increases (with one exception). Income growth rates were higher during the years of price increases than before in about half of the case study countries.Markets and Market Access,Environmental Economics&Policies,Climate Change,Engineering,Economic Theory&Research,Economic Theory&Research,Environmental Economics&Policies,Access to Markets,Markets and Market Access,Energy and Environment

Composite variable formulations for express shipment service network design

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 181-187).In this thesis, we consider large-scale network design problems, specifically the problem of designing the air network of an express shipment (i.e., overnight) delivery operation. We focus on simultaneously determining the route structure, the assignment of fleet types to routes, and the flow of packages on aircraft. Traditional formulations for network design involve modeling both flow decisions and design decisions explicitly. The bounds provided by their linear programming relaxations are often weak. Common solution strategies strengthen the bounds by adding cuts, but the shear size of the express shipment problem results in models that are intractable. To overcome this shortcoming, we introduce a new modeling approach that 1) removes the flow variables as explicit decisions and embeds them within the design variables and 2) combines the design variables into composite variables, which represent the selection of multiple aircraft routes that cover the demands for some subset of commodities. The resulting composite variable formulation provides tighter bounds and enables very good solutions to be found quickly. We apply this type of formulation to the express shipment operations of the United Parcel Service (UPS). Compared with existing plans, the model produces a solution that reduces the number of required aircraft by almost 11 percent and total annual cost by almost 25 percent. This translates to potential annual savings in the hundreds of millions of dollars. We establish the composite variable formulation to be at least as strong as the traditional network design formulation, even when the latter is strengthened by Chvital-Gomory rounding, and we demonstrate cases when strength is strictly improved. We also place the composite variable formulation in a more general setting by presenting it as a Dantzig-Wolfe decomposition of the traditional (intractable) network design formulation and by comparing composite variables to Chvital-Gomory cuts in the dual of a related formulation. Finally, we present a composite variable formulation for the Pure Fixed Charge Transportation Problem to highlight the potential application of this approach to general network design and fixed-charge problems.by Andrew P. Armacost.Ph.D

Methodological Analyses of the Export Transportation Network Flows: Hard Red Winter Wheat

Agricultural Economic

Express shipment pick-up and delivery : evaluating airline recovery options

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (p. 93-96).Irregular operations in the Express Shipment Service Delivery industry require real time solutions that can be implemented to determine routings for aircraft and time-sensitive commodities. During inclement weather, crew unavailability, and mechanical failures, operations personnel use various approaches to recover from disruptions, including rescheduling or canceling flight legs, diverting aircraft and commodities, or missing service all together. We present an optimization approach that can capture and evaluate the effects of different operating policies. Specifically, we compare and contrast three different strategies, namely: 1) minimizing schedule delay, 2) minimizing the number of service failures, and 3) minimizing the combined cost of operations and service failures. We provide proof of concept by implementing our optimization models and evaluating them using several representative scenarios and conducting computational experiments. The solutions, which are highly dependent on user-defined parameters, represent tradeoffs between costs of operations and service failures.by Jennifer C. Cheung.S.M