Browsing by Subject "Resource allocation"
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Item A methodological framework for cross-asset resource allocations to support infrastructure management(2016-08) Porras-Alvarado, Juan Diego; Zhang, Zhanmin, 1962-; Machemehl, Randy; Walton, Michael; Bhasin, Amit; Gao, LuResource allocation mechanisms have become a major issue for transportation agencies in the United States and around the world. For this reason, transportation agencies are exploring alternatives to modify traditional allocation mechanism due to budgetary challenges generated by the decrease in funding and the increasing cost of preserving and operating transportation systems. Transportation asset management (TAM) practices enable agencies to change the operation and management of transportation infrastructure from the traditional concept of “public-owned” systems to more business-oriented processes. One of the main concerns with the TAM framework and its implementation is the absence of an organized process for cross-asset resource allocations. Additionally, most of the alternative methods for funding allocations focus on maximizing infrastructure performance under budget constraints, but ignore the consideration of equity or fairness. The objective of this study is to develop an innovative methodological framework for cross-asset resource allocations, yielding a data-oriented approach to enhancing infrastructure management. The allocation module is comprised of three resource allocation mechanisms following a top-down approach: a fair division approach based on asset performance, a performance-based multi-objective optimization, and an asset value-based multi-objective optimization. In the first mechanism, the fair division method is used to allocate resources in such a way that all parties involved believe they are receiving a fair share of the available resource based on established utility functions. Then, Collective Utility Functions (CUFs) are employed to perform the resource allocation, which results in total utility and total envy values. These values are used to conduct trade-off analyses of the different allocations based on the CUFs. Under the second procedure, a multi-objective optimization formulation is employed to integrate efficiency and equity, where equity is taken into consideration by using utility and envy concepts, while efficiency is incorporated by maximizing performance. In the third mechanism, an innovative asset value methodology is integrated into the cross-asset resource allocation process, serving as a common comparative measure between assets. To demonstrate the applicability of the proposed methodological framework, a case study was conducted using two asset groups, pavements and bridges, from the roadway network of the Austin District located in Texas. Results from the case study shows that the proposed methodological framework has great potential as a tool to support highway agencies in performing cross-asset resource allocations at the network level.Item An analysis between organizational structure and enterprise resource planning system implementation success(Texas Tech University, 2004-12) Colak, MuratIn the past decade, the business environment has changed dramatically. The world has become a small and very dynamic marketplace and the evolution of Enterprise Resource Planning (ERP) systems has been a highlight in the information systems arena. While the growth of ERP systems has been enormous, cost and failures have undermined its true capabilities. With respect to the high percentage of implementation failures, it is very important to study all of the critical success factors in order to increase the ratio of successful implementations. This research presents an experimental design for a survey that will be utilized to investigate what effect that organizational structure has on the success of ERP implementation. First the organizational structures are described and possible effects of these structures are identified. Then, the necessary tests to analyze the survey are described. Finally, the results of the statistical analysis take place. After getting the results, the expected and actual relationship between the variables are discussed. Finally, conclusions about these results and future research that may take place after this study is described.Item Analyses of water markets and allocation mechanisms in Texas(Texas Tech University, 1997-08) Yoskowitz, David WilliamThe purpose of this study is, given water scarcity in the State of Texas, to examine the efforts to improve the efficient use of water through marketing and transfers. There has been quite a bit of work conducted in the area ofthe efficiency of water marketing in general, including Howe et al. [1986], Saliba [1987], and Simpson [1992]. But only a relatively small number of empirical studies have been conducted and out of these very few have any statistical analysis of water marketing. The specific objective is to develop three essays that examine the differing mechanisms of water marketing or water reallocation among users. Essay 1 will examine the surface water spot water transactions along the Rio Grande. Statistical analysis along with on site interviews will be used to reveal what determines spot market prices and why price differentials between users exists. Essay 2, using a modified case study approach, will examine underground water transactions made by West Texas municipalities. The purchase of irrigated farmland by municipalities to increase supply is becoming a common practice as limited surface water is already committed. Essay 3 will examine critically the purpose, structure, and operation ofthe Texas Water Bank (TWB) which was created to facilitate water marketing on a statewide basis.Item Cognitive radios : fundamental limits and applications to cellular and wireless local networks(2012-05) Chung, Goochul; Vishwanath, Sriram; Shakkottai, Sanjay; Andrews, Jeffrey; Caramanis, Constantine; Choi, JihwanAn ever increasing number of wirelessly-enabled applications places a very high demand on stringent spectral resources. Cognitive radios have the potential of enhancing spectral efficiency by improving the usage of channels that are already licensed for a specific purpose. Research on cognitive radios involves answering questions such as: how can a cognitive radio transmit at a high data rate while maintaining the same quality of service for the licensed user? There are multiple forms of cognition studied in literature, and each of these models must be studied in detail to understand its impact on the overall system performance. Specifically, the information-theoretic capacity of such systems is of great interest. Also, the design of cognitive radio is necessary to achieve those capacities in real applications. In this dissertation, we formulate different problems that relate to the performance of such systems and methods to increase their efficiency. This dissertation discusses, firstly, the means of "sensing" in cognitive systems, secondly, the optimal resource allocation algorithms for interweave cognitive radio, and finally, the fundamental limits of partially and overly cognitive overlay systems.Item Devolution in a Texas school system : redefining the efforts of three central office directors at the school site(2003-08) Moynihan-McCoy, Toni Marsh, 1945-; Thomas, Michael P.Item Financial resource allocation in Texas : how does money matter(2010-05) Villarreal, Rosa Maria, active 2010; Olivárez, RubénThe study examined school district expenditures in Texas and their correlations with student achievement. The following research question guided this study: Which resource allocations produce statistically significant correlations between the resource allocation variances among school district and student achievement? An ordinal logistic regression analysis included 1009 school districts in the State of Texas, 18 of 26 possible finance function codes provided per-pupil dollar amounts, and 9 of 11 possible demographic categories were utilized for the study. The study held the school district as the unit of analysis. The statistical model was used to regress the dollar amounts categorized by financial function codes and percent student demographics to determine if a relationship existed with the dependent variable of the Texas Education Agency’s defined accountability rating during the 5-year time period—2004-2008. At the national level, there is a long-standing debate over whether the amount of money allocated to education affects student achievement. The literature review presents two sides of the debate concerning whether financial resources make a difference with regard to student achievement as represented through district-level accountability ratings. The research revealed that specific school district resource allocations by function code are statistically significant with regard to district level accountability measures through the Texas Education Agency (TEA) accountability system. However, the odds ratios temper the impact of the significance. The research also revealed that demographics are statistically significant in the State of Texas accountability system.Item An information model for subcontractor resource allocation(2010-05) Wang, Ting-Kwei; O'Brien, William J.; Caldas, Carlos H.; Machemehl, Randy B.; Julien, Christine; O’Connor, James T.Subcontractors perform the majority of the work on commercial construction projects. However, only limited research has focused on subcontractors’ practical needs. In response, this research discovered and documented subcontractor needs through data collections and extended these findings with development of an information model and tool. This research significantly enlarges detailed understanding of subcontractor management practices, in particular around resource allocation across multiple projects. While existing research has shown the importance of multi-project management, exploration of details of this process has largely been limited to overviews of policies. Rich details that allow for specific critiques of existing methods and tools have been missing. This research provides such details, including specific limitations and recommendations to existing information standards, commercial applications, and assignment algorithms. In particular, contributions of this research focus on support for what-if analysis under extreme frequency of resource reallocation, a limitation of existing tools and methods that make them unsuitable for most subcontractors.Item A mixed methods study : the allocation of resources in times of fiscal austerity for community colleges in the state of Texas(2012-08) Bender, Karla Connor; Roueche, John E.; Gooden, Mark A.; Heilig, Julian V.; Bumphus, Walter G.; Tyler, Arthur Q.; Butler, Jesse J.The current fiscal crisis in U.S. institutions of higher education is a direct result of the 2008 global recession. The collapse in the financial industry, housing foreclosures, and high unemployment are just a few of the consequences that continue to wreak havoc on state and local governments. Funding cuts continue to trickle down as state revenue sources decline. Debates over what should be funded (national security, health, or education) leave legislative bodies at odds. Higher education is especially vulnerable in part because lawmakers are less willing to slash such programs as Medicaid, children's health insurance and K-12 public education. The competition for state funding leaves public institutions with fewer resources and major deficits to address. Given the challenging fiscal environment that community colleges continue to face, this research, focusing specifically on community colleges in the state of Texas, presents the pressing array of challenges that confront community colleges and identifies the techniques that have been adopted to allocate resources most effectively. Exploration of the issue may provide insight into the best practices, and strategies that can help other institutions address fiscal challenges. A mixed method research design, using survey and interview research methods, was used to implement this study. The survey findings provide useful insights into what is currently going on at Texas community colleges. Follow up interview discussions compliment the survey findings and provide the researcher with important contextual information pertaining to “why” things are as they are based on participant perceptions.Item Multiuser resource allocation in multichennel wireless communication systems(2006) Shen, Zukang; Andrews, Jeffrey G.; Evans, Brian L. (Brian Lawrence), 1965-A downlink wireless system features a centralized basestation communicating to a number of users physically scattered around the basestation. The purpose of resource allocation at the basestation is to intelligently allocate the limited resources, e.g. total transmit power and available frequency bandwidth, among users to meet users’ service requirements. Channel-aware adaptive resource allocation has been shown to achieve higher system performance than static resource allocation, and is becoming more critical in current and future wireless communication systems as the user data rate requirements increase. Adaptive resource allocation in a multichannel downlink system is more challenging because of the additional degree of freedom for resources, but offers the potential to provide higher user data rates. Multiple channels can be created in the frequency domain using multiple carrier frequencies, a.k.a. multicarrier modulation (MCM), or in the spatial domain with multiple transmit and receive antennas, a.k.a. multiple-input multiple-output (MIMO) systems. This dissertation aims to study the system performance, e.g. total throughput and/or fairness, in multiuser multicarrier and multiuser MIMO systems with adapvii tive resource allocation, as well as low complexity algorithms that are suitable for cost-effective real-time implementations in practical systems. The first contribution of this dissertation is a general framework for adaptive resource allocation in multiuser multicarrier systems that maximizes the total throughput subject to fairness constraints to enforce arbitrary proportional data rates among users. Whereas the global optimality is computationally intensive to obtain, a low complexity algorithm that decouples the subchannel and power allocation is proposed. The second contribution concerns precoding using block diagonalization (BD) for single-carrier downlink multiuser MIMO systems. The contribution is twofold. First, it is shown that BD, as a practically realizable precoding technique, can achieve a significant part of the sum capacity achieved by dirty paper coding (DPC), which is optimal. Practical coding schemes that approach the DPC sum capacity, however, are still largely unknown. Second, an upper bound on the ergodic sum capacity gain of DPC over BD in Rayleigh fading channels is derived. The third contribution concerns low-complexity BD precoding algorithms. Due to the zero inter-user interference requirement imposed by BD, the maximum number of simultaneously supportable users is limited. The brute-force search for the optimal user set, however, is computationally prohibitive for systems with a large number of users. The dissertation proposes two suboptimal user selection algorithms for BD that have linear complexity in the number of users, yet achieve total throughput close to the optimal. A common characteristic of the resource allocations for multiuser multicarrier and multiuser MIMO systems is that the limited resources shall be allocated among multiple users as well as multiple parallel subchannels. As MCM and MIMO have been widely adopted in various standards, the research in this dissertation contributes to a better understanding of the system performance, and bridges the theory to practical implementations with the proposed low complexity algorithms.Item NoC Resource Allocation Based on Physical Design Techniques(2014-05-05) Yang, GongmingNetworks-on-Chip (NoC) has been recognized as a scalable approach for on-chip communication. Quality-of-Service (QoS) is a fundamental part of application specific NoCs. This thesis focuses on resource allocation on NoC, to improve the capability of NoC for Guaranteed Service (GS). A graph model is adopted to describe physical and temporal sources of a NoC. Based on the graph model, an RRR-based algorithm is proposed for simultaneous routing and time slot allocation. In addition, a negotiation-based algorithm is suggested for achieving power-efficient QoS for application-specific NoCs. Last, a hybrid NoC architecture, which combines circuit switching and packet switching, is developed and investigated. Experimental results show that our techniques outperform previous works.Item On a class of distributed algorithms over networks and graphs(2011-05) Lee, Sang Hyun, 1977-; Vishwanath, Sriram; Vikalo, Haris; Powers, Edward J.; Ghosh, Joydeep; Sanghavi, Sujay; Qiu, LiliDistributed iterative algorithms are of great importance, as they are known to provide low-complexity and approximate solutions to what are otherwise high-dimensional intractable optimization problems. The theory of message-passing based algorithms is fairly well developed in the coding, machine learning and statistical physics literatures. Even though several applications of message-passing algorithms have already been identified, this work aims at establishing that a plethora of other applications exist where it can be of great importance. In particular, the goal of this work is to develop and demonstrate applications of this class of algorithms in network communications and computational biology. In the domain of communications, message-passing based algorithms provide distributed ways of inferring the optimal solution without the aid of a central agent for various optimization problems that happen in the resource allocation of communication networks. Our main framework is Affinity Propagation (AP), originally developed for clustering problems. We reinterpret this framework to unify the development of distributed algorithms for discrete resource allocation problems. Also, we consider a network-coded communication network, where continuous rate allocation is studied. We formulate an optimization problem with a linear cost function, and then utilize a Belief Propagation (BP) approach to determine a decentralized rate allocation strategy. Next, we move to the domain of computational biology, where graphical representations and computational biology play a major role. First, we consider the motif finding problem with several DNA sequences. In effect, this is a sequence matching problem, which can be modeled using various graphical representations and also solved using low-complexity algorithms based on message-passing techniques. In addition, we address the application of message-passing algorithms for a DNA sequencing problem where the one dimensional structure of a single DNA sequence is identified. We reinterpret the problem as being equivalent to the decoding of a nonlinear code. Based on the iterative decoding framework, we develop an appropriate graphical model which enables us to derive a message-passing algorithm to improve the performance of the DNA sequencing problem. Although this work consists of disparate application domains of communications, networks and computational biology, graphical models and distributed message-passing algorithms form a common underlying theme.Item Optimal allocation of irrigation water in Egypt - a dynamic approach(Texas Tech University, 1992-05) Darwish, Mohamed RagyCurrently, Egypt is faced with several fundamental problems: an ever-increasing population, a limited supply of cultivable land and a limited supply of water resources. These problems intensify the importance of developing efficient natural resource use strategies. The future of Egypt depends on the water stored in the Nasser Lake reservoir for all purposes. There is strong evidence that governmental policies in the agricultural sector have led to an inefficient allocation of resources in general and water resources in particular, the latter being the focus of this study. These policies should be examined within sound economic frameworks, and policy alternatives should be tested to insure the efficient use of water resources. The last drought in Africa brought attention to the need for optimal intertemporal allocation of this vital resource. The main objective of this study was to determine optimal decision rules of cropping mix and irrigation water in Egypt under different policy settings and water inflow levels. This study tests the impact of these policies and water availability on the optimal decision rules in an intertemporal context. A total of 10 dynamic programming models were developed to address the objective. The models considered two different policy settings. The first setting included the current agricultural policy of cropping area regulations and administered prices in both agricultural inputs and outputs markets. In the second setting, the elimination of these policies was assumed to simulate free market conditions. Both policy settings were tested under five different water inflow scenarios over a 30-year planning horizon. The derived optimal decision rules for the different models were used to construct a Decision Rule Matrix, which summarizes the optimal course of action that should be pursued given a particular condition. The results obtained indicate that the elimination of current agricultural land regulation and the modification of the policies, with respect to prices in both inputs and outputs markets in the Egyptian agricultural sector, would lead to higher revenues and to an increase in water use efficiency. The study also revealed that if such deregulation actions were to take place, a reduction in the variation of regional and intertemporal water allocation would be achieved. This in turn would reduce the managerial burden of water control and allow for better water management. Furthermore, such actions would lead to a regional crop consolidation process which would ease the managerial and administrative effort requirements for crop production and water control.Item Recipient allocation preferences and organizational choices: a fit perspective(Texas A&M University, 2007-04-25) Gogus, Celile ItirThe purpose of this dissertation is to understand how individuals?????? preferences for resource allocation affect their attitudinal and behavioral responses towards the organization. Building on the three main allocation norms (equity norm, equality norm and need norm) and taking the perspective of the recipient of an allocation, a model that predicts the antecedents of norm preference and consequences of using different allocation norms by the organization is presented and tested with a sample of Turkish registered nurses. Results show that recipients have differential preferences for allocation norms depending on resource type being allocated and characteristics of the environment. Furthermore, the fit or misfit between recipients?????? preferred allocation norm and the allocation norm used by the organization affects recipients?????? justice perceptions about the organization, their outcome satisfaction and performance.Item Resource allocation in large-scale multi-server systems(2014-12) Moharir, Sharayu Arun; Shakkottai, Sanjay; Sanghavi, Sujay Rajendra, 1979-The focus of this dissertation is the task of resource allocation in multi- server systems arising from two applications – multi-channel wireless com- munication networks and large-scale content delivery networks. The unifying theme behind all the problems studied in this dissertation is the large-scale nature of the underlying networks, which necessitate the design of algorithms which are simple/greedy and therefore scalable, and yet, have good perfor- mance guarantees. For the multi-channel multi-hop wireless communication networks we consider, the goal is to design scalable routing and scheduling policies which stabilize the system and perform well from a queue-length and end-to-end delay perspective. We first focus on relay assisted downlink networks where it is well understood that the BackPressure algorithm is stabilizing, but, its delay performance can be poor. We propose an alternative algorithm - an iterative MaxWeight algorithm and show that it stabilizes the system and outperforms the BackPressure algorithm. Next, we focus on wireless networks which serve mobile users via a wide-area base-station and multiple densely deployed short- range access nodes (e.g., small cells). We show that traditional algorithms that forward each packet at most once, either to a single access node or a mobile user, do not have good delay performance and propose an algorithm (a distributed scheduler - DIST) and show that it can stabilize the system and performs well from a queue-length/delay perspective. In content delivery networks, each arriving job can only be served by servers storing the requested content piece. Motivated by this, we consider two settings. In the first setting, each job, on arrival, reveals a deadline and a subset of servers that can serve it and the goal is to maximize the fraction of jobs that are served before their deadlines. We propose an online load balanc- ing algorithm which uses correlated randomness and prove its optimality. In the second setting, we study content placement in a content delivery network where a large number of servers, serve a correspondingly large volume of con- tent requests arriving according to an unknown stochastic process. The main takeaway from our results for this setting is that separating the estimation of demands and the subsequent use of the estimations to design optimal content placement policies (learn-and-optimize approach) is suboptimal. In addition, we study two simple adaptive content replication policies and show that they outperform all learning-based static storage policies.Item Scheduling and resource allocation for mobile broadband networks(2014-12) Ishiguro, Arthur Go; Andrews, Jeffrey G.; De Veciana, GustavoUnlike traditional cellular networks, where voice calls dominate the network traffic, modern mobile traffic is created by of a mixture of both voice and broadband data services. The heterogeneous mixture of voice and data services in mobile broadband networks includes voice calls, web browsing, file transfers, video streaming, and social media applications. Consequently, network planning and radio resource management strategies must be aware of the quality of experience perceived by the users using various types of applications. In this report, we explore the traffic characteristics, scheduling and resource allocation strategies, and user experience models in mobile broadband networks.Item Small cell and D2D offloading in heterogeneous cellular networks(2015-05) Ye, Qiaoyang; Andrews, Jeffrey G.; Caramanis, Constantine; Baccelli, Francois; Morton, David; Shakkottai, Sanjay; Vishwanath, SriramFuture wireless networks are evolving to become ever more heterogeneous, including small cells such as picocells and femtocells, and direct device-to-device (D2D) communication that bypasses base stations (BSs) altogether to share stored and personalized content. Conventional user association schemes are unsuitable for heterogeneous networks (HetNets), due to the massive disparities in transmit power and capabilities of different BSs. To make the most of the new low-power infrastructure and D2D communication, it is desirable to facilitate and encourage users to be offloaded from the macro BSs. This dissertation characterizes the gain in network performance (e.g., the rate distribution) from offloading users to small cells and the D2D network, and develops efficient user association, resource allocation, and interference management schemes aiming to achieve the performance gain. First, we optimize the load-aware user association in HetNets with single-antenna BSs, which bridges the gap between the optimal solution and a simple small cell biasing approach. We then develop a low-complexity distributed algorithm that converges to a near-optimal solution with a theoretical performance guarantee. Simulation results show that the biasing approach loses surprisingly little with appropriate bias factors, and there is a large rate gain for cell-edge users. This framework is then extended to a joint optimization of user association and resource blanking at the macro BSs – similar to the enhanced intercell interference coordination (eICIC) proposed in the global cellular standards, 3rd Generation Partnership Project (3GPP). Though the joint problem is nominally combinatorial, by allowing users to associate to multiple BSs, the problem becomes convex. We show both theoretically and through simulation that the optimal solution of the relaxed problem still results in a mostly unique association. Simulation shows that resource blanking can further improve the network performance. Next, the above framework with single-antenna transmission is extended to HetNets with BSs equipped with large-antenna arrays and operating in the massive MIMO regime. MIMO techniques enable the option of another interference management: serving users simultaneously by multiple BSs – termed joint transmission (JT). This chapter formulates a unified utility maximization problem to optimize user association with JT and resource blanking, exploring which an efficient dual subgradient based algorithm approaching optimal solutions is developed. Moreover, a simple scheduling scheme is developed to implement near-optimal solutions. We then change direction slightly to develop a flexible and tractable framework for D2D communication in the context of a cellular network. The model is applied to study both shared and orthogonal resource allocation between D2D and cellular networks. Analytical SINR distributions and average rates are derived and applied to maximize the total throughput, under an assumption of interference randomization via time and/or frequency hopping, which can be viewed as an optimized lower bound to other more sophisticated scheduling schemes. Finally, motivated by the benefits of cochannel D2D links, this dissertation investigates interference management for D2D links sharing cellular uplink resources. Showing that the problem of maximizing network throughput while guaranteeing the service of cellular users is non-convex and hence intractable, a distributed approach that is computationally efficient with minimal coordination is proposed instead. The key algorithmic idea is a pricing mechanism, whereby BSs optimize and transmit a signal depending on the interference to D2D links, who then play a best response (i.e., selfishly) to this signal. Numerical results show that our algorithms converge quickly, have low overhead, and achieve a significant throughput gain, while maintaining the quality of cellular links at a predefined service level.Item Strategic configurations of system resources: configurations for the organizational orientation to change context creation competency(Texas Tech University, 1995-08) Black, Janice Anne DonahooDuring the preponderance of their lifetime, most companies do not attain average profitability rates much less above average ones. Although external elements such as market and industry position were the prominent form of determining firm survival and success in the past, a recent stream of research, the resource based view has refocused attention internally. This dissertation examines the "bundling" of the resources that is referred to in the resource based (and core competency) literature and which results in the creation of a competency. In particular, this dissertation examines a strategically important competency in an organization, the creation of an organizational context needed for organizational learning to occur. A framework provided by Ghoshal and Bartlett (1994) for the context creation calls for a set of four key attributes: discipline, stretch, trust, and support. The competency configurations among these key attributes and their interaction terms are examined to determine if some particular configuration of relationships among them is necessary for both higher levels of the competency and higher performance by comparing the configurations of competencies from high and low competency levels and high and low performance levels within and across sites and then across industry and firm boundaries. Such comparisons enable this dissertation to begin to open the "black box" on the bundling of resources. The dissertation finds that those maps created from high levels of orientation to change or performance are more similar with each other within sites, across sites, and across firms and industries. The range of variability across the high level maps was small when compared to the range found in the low level maps. In other words, there are many diverse ways to fail and only a few similar ways to succeed. This dissertation also found that being ready to change need not adversely affect performance since similar configurations are found in both high maps. Thus the bundling of this competencies resources appears to matter. Although these configurations were compared across sites within a firm and between firms, only a few actual sites were analyzed and, hence, there is room for further corroboration in future research.Item Study of efficient link adaptation schemes in wireless orthogonal frequency division multiplexing (OFDM) systems(2009-08) Choi, Eun Ho; Womack, Baxter F., 1930-; Andrews, Jeffrey G.Wireless communication systems require high spectral efficiency and throughput in order to be cost-effective. Link adaptation schemes are known to be a good solution to achieve this goal. However, the necessity of additional information or increased complexity prevents these schemes from being implemented. In this context, research on resource allocation based on different constraints, such as complexity or feedback, is important. The major contribution of this dissertation is the development of three novel techniques to enhance performance in practical implementations of the adaptive OFDM systems. This dissertation first introduces a new multiuser OFDM system to enhance performance in the low SNR regime. In this scheme, multiuser diversity can be efficiently amplified from random power allocation and opportunistic scheduling. Higher spectral efficiency can be achieved without an increase of complexity or feedback amount compared to conventional multiuser OFDM systems using equal power allocation. This dissertation also presents a modified multi-mode power loading scheme. A modified multi-mode power loading scheme can circumvent the limit of current multi-mode power loading schemes by significantly reducing search amount from 2N - 1 to N, where N is the number of subcarriers. Finally, this dissertation has introduced adaptive OFDM systems using channel gain order information in limited feedback environments. Adaptive OFDM systems using the order mapping technique achieve comparable performance to conventional adaptive OFDM systems in terms of bit error rate and average spectral efficiency, while the amount of feedback is significantly reduced. Furthermore, by simply exploiting order mapping and interpolation, the analyzing technique circumvents the practical shortcomings of previous limited feedback techniques for OFDM systems.Item Three essays on capital adjustment, reallocation and aggregate productivity(2007) Cao, Shutao, 1970-; Cooper, Russell W., 1955-; Corbae, DeanThis dissertation consists of three chapters. Chapter one estimates the capital adjustment costs at the plant level in a model entry and exit. We find that the estimated variance of plant-specific productivity shock is larger than obtained from balanced panel estimation. Estimation using the unbalanced panel generates a larger irreversibility cost, a smaller disruption cost, and a smaller convex cost, all compared with the estimates by Cooper and Haltiwanger (2006). In chapter two, we study how much of the aggregate productivity changes can be accounted for by the capital reallocation. We also study the impact of capital reallocation on the productivity dispersion across firms. We find that the capital reallocations accounts for roughly 12 percent of the labor productivity and capital productivity are reduced as the reallocation activity increases. When the economy-wide technology has a positive change, the reallocation increases temporarily then drops to its original level. After a short transition, the economy settles down with an increased labor productivity. Chapter three further studies the quantitative role of allocation, entry and exit in the growth of aggregate productivity. We find that, without including in the model the forces that drive the entry and exit changes, the model economy has a modest increase in the aggregate productivity as a result of decrease in the fixed reallocation cost.