<p> Wireless mesh networks are now being used to deploy radio coverage in a large variety of outdoor applications. One of the major obstacles that these networks face is that of providing the nodes with electrical power and wired network connections. Solar powered mesh nodes are increasingly used to eliminate the need for these types of connections, making the nodes truly tether-less. In these types of networks however, the cost of the energy collection and storage components can be a significant fraction of the total node cost, which motivates a careful selection of these resources.</p> <p> This thesis focusses on key issues relating to the deployment and operation of solar powered wireless mesh networks. First, the problem of provisioning the mesh nodes with a suitable solar panel and battery configuration is considered. This is done by assuming a bandwidth usage profile and using historical solar insolation data for the desired deployment location. A resource provisioning algorithm is proposed based on the use of temporal shortest-path routing and taking into account the node energy-flow for the target deployment time period. A methodology is introduced which uses a genetic algorithm (GA) to incorporate energy-aware routing into the resource assignment procedure. Results show that the proposed resource provisioning algorithm can achieve large cost savings when compared to conventional provisioning methods.</p> <p> During post-deployment network operation, the actual bandwidth profile and solar insolation may be different than that for which the nodes were originally provisioned. To prevent node outage, the network must reduce its workload by flow controlling its input traffic. The problem of admitting network bandwidth flows in a fair manner is also studied. A bound is first formulated which achieves the best max/min fair flow control subject to eliminating node outage. The bound motivates a proposed causal flow control algorithm whose operation uses prediction based on access to on-line historical weather data. The results show that the proposed algorithm performs well when compared to the analytic bound that is derived for this problem.</p> <p> Finally, as user traffic evolves, the network resources need to be updated. This problem is considered using a minimum cost upgrade objective. A mixed integer linear programming (MILP) formulation is derived to obtain a lower bound on the network update cost. A genetic algorithm is used to determine practical cost-effective network resource upgrading. The results show that the proposed methodology can obtain significant cost savings.</p> / Thesis / Doctor of Philosophy (PhD)

Electric power systems are a key infrastructure today. Power systems can be divided into three major parts: generation, transmission, and distribution. Out of these the distribution system is the most complex part and least studied system. In order to have continuous and reliable power to all customers it is necessary to have a good protection system. Major disturbances that are caused and last for a very short duration are called faults. With the advent of distributed generation (DG), the understanding of fault response has become more difficult. This thesis presents the study of the fault response and the factors that influence the fault response with and without DG. As a part of the fault analysis line to ground faults are placed at various locations on the I 13 node feeder test case. Simulations are conducted in PSCAD and the results are analyzed. At each node the voltage and the current changes at the time of the fault are recorded. A DG is added to the system and is located at various nodes for each fault and the impact of the DG on the fault voltage and current quantities is recorded. A comparison of the impact of faults at various locations is presented. The impact of faults without DG and with DG is also analyzed

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An ad hoc network adopts a decentralized unstructured networking model that depends on node cooperation for key network functionalities such as routing and medium access. The significance of node cooperation in ad hoc networks makes network survival particularly sensitive to insider node behavior. The presence of selfish or malicious nodes in an ad hoc network could greatly degrade the network performance and might even result in a total communication breakdown. Consequently, it is important for both security and performance reasons to discourage, expose, and react to such damaging misbehavior. Reputation management systems have been proposed to mitigate against such misbehavior in ad hoc networks. The functions of a reputation management system are to evaluate nodes' quality of behavior based on their cooperation (evaluation), distinguish between well-behaved and misbehaving nodes (detection), and appropriately react to misbehaving nodes (reaction). A significant number of reputation management systems have been proposed for ad hoc networks to date. However, there has been no attempt to consolidate all current research into a formal framework for reputation management systems. The lack of a formal framework is a potential weakness of the research field. For example, a formal comparison of proposed reputation management systems has remained difficult, mainly due to the lack of a formal framework upon which the comparison could be based. There is also a lack of formal metrics that could be used for quantitative evaluation and comparison of reputation management systems. Another major shortcoming in this research field is the assumption that the functions of reputation management (evaluation, detection, and reaction) are carried out homogeneously across time and space at different nodes. The dynamic nature of ad hoc networks causes node behavior to vary spatially and temporally due to changes in the local and network-wide conditions. Reputation management functions do not adapt to such changes, which may impact the system accuracy and promptness. We herein recognize an adaptive reputation management system as one where nodes carry out the reputation management functions heterogeneously across time and space according to the instantaneous perception of each of its surrounding network conditions. In this work, we address the above concerns. We develop a formal framework for reputation management systems upon which design, evaluation, and comparison of reputation management systems can be based. We define and discuss the different components of the framework and the interactions among them. We also define formal metrics for evaluation of reputation management systems. The metrics assess both, the effectiveness (security issues) of a reputation management system in detecting misbehavior and limiting its negative impact on the network, and its efficiency (performance issues) in terms of false positives and overhead exerted by the reputation management system on the network. We also develop ARMS, an autonomous reputation management system, based on the formal framework. The theoretical foundation of ARMS is based on the theory of Sequential Probability Ratio Test introduced by Wald. In ARMS, nodes independently and without cooperation manage their reputation management system functions. We then use ARMS to investigate adaptation in reputation management systems. We discuss some of the characteristics of an adaptive reputation management system such as sensitivity, adaptability, accuracy, and promptness. We consider how the choice of evaluation metric, typically employed by the evaluation function for assessment of node behavior, may impact the sensitivity and accuracy of node behavior evaluation. We evaluate the sensitivity and accuracy of node behavior evaluation using a number of metrics from the network and medium access layer. We then introduce a time-slotted approach to enhance the sensitivity of the evaluation function and show how the duration of an evaluation slot can adapt according to the network activity to enhance the system accuracy and promptness. We also show how the detection function can adapt to the network conditions by using the node's own behavior as a benchmark to set its detection parameters. To the best of our knowledge, this is the first work to explore the adaptation of the reputation management functions in ad hoc networks. / Ph. D.

Recently, many new types of wireless networks have emerged, such as mobile ad hoc networks (MANETs), cognitive radio networks (CRNs) and large scale wireless sensor networks. To get better performance in these wireless networks, various schemes, e.g., metrics, policies, algorithms, protocols, etc., have been proposed. Among them, optimal schemes that can achieve optimal performance are of great importance. On the theoretical side, they provide important design guidelines and performance benchmarks. On the practical side, they guarantee best communication performance with limited network resources. In this dissertation, we focus on the modeling and optimization of routing in wireless networks, including both broadcast routing, unicast routing, and convergecast routing. We study two aspects of routing: algorithm analysis and Qos analysis. In the algorithmic work, we focus on how to build optimal broadcast trees. We investigate the optimality compatibility between three tree-based broadcast routing algorithms and routing metrics. The Qos work includes three parts. First, we focus on how to optimally repair broken paths to minimize impact of path break in MANETs. We propose a provably optimal cached-based route repair policy for real-time traffic in MANETs. Second, we focus on the impact of secondary user (SU) node placement on SU traffic delay in CRNs. We design SU node placement schemes that can minimize the multi-hop delay in CRNs. Third, we analyze the convergecast delay of a large scale sensor network which coexists with WiFi nodes. We derive a closed form delay formula, which can be used to estimate sensor packet convergecast delay given the distance between a sensor node and the sink node together with other networking setting parameters. The main contributions of this dissertation are summarized as follows: Optimality compatibility study between tree-based broadcast routing algorithms and routing metrics: Broadcast routing is a critical component in the routing design. While there are plenty of routing metrics and broadcast routing schemes in current literature, arbitrary combination of broadcast routing metrics with broadcast tree construction (BTC) algorithms may not result in optimal broadcast trees. In this work, we study the requirement on the combination of routing metrics and BTC algorithms to ensure optimal broadcast tree construction. When a BTC algorithm fails to find the optimal broadcast tree, we define that the BTC algorithm and the metric are not optimality compatible. We show that different BTC algorithms have different requirements on the properties of broadcast routing metrics. The metric properties for BTC algorithms in both undirected network topologies and directed network topologies are developed and proved. They are successfully used to verify the optimality compatibility between broadcast routing metrics and BTC algorithms. Optimal cache-based route repair policy for real-time traffic in mobile ad hoc networks: Real-time applications in ad hoc networks require fast route repair mechanisms to minimize the interruptions to their communications. Cache-based route repair schemes are popular choices since they can quickly resume communications using cached backup paths after a route break. In this work, through thorough theoretical modeling of the cache-based route repair process, we derive a provably optimal cache-based route repair policy. This optimal policy considers both the overhead of the route repair schemes and the promptness of the repair action. The correctness and advantages of our optimal policy are validated by extensive simulations. Optimal secondary user node placement study in cognitive radio networks: Information propagation speed (IPS) in a multi-hop CRN is an important factor that affects the network's delay performance and needs to be considered in network planning. The impact of primary user (PU) activities on IPS makes the problem of analyzing IPS in multi-hop CRNs very challenging and hence unsolved in existing literature. In this work, we fill this technical void. We establish models of IPS in multi-hop CRNs and compute how to maximize IPS in two cases. The first case, named the maximum network IPS, maximizes IPS across a network topology over an infinite plane. The second case, named the maximum flow IPS, maximizes the IPS between a given pair of source and destination nodes separated by a fixed distance. We reveal that both maximum IPSs are determined by the PU activity level and the placement of SU relay nodes. We design optimal relay placement strategies in CRNs to maximize these two IPS under different PU activity levels. The correctness of our analytical results is validated by simulations and numerical experiments. Convergecast delay analysis of large scale sensor networks coexisting with WiFi networks: Due to the increasing popularity of wireless devices, such as WiFi (IEEE 802.11) and ZigBee (IEEE 802.15.4), the ISM bands have become more and more crowded. Since ZigBee is the de facto radio technology of sensor networks, coexistence of WiFi networks and sensor (ZigBee) networks is challenging because of the great heterogeneity between WiFi and ZigBee technologies. In the presence of interference from WiFi and other sensor nodes, the performance of sensor networks is not clearly understood. In this work, we study delay performance of a large scale sensor network which coexists with WiFi networks. Given the distance from the sensor node to the sink node, we are interested in the expected delay of sensor packets to reach the sink node in the presence of both WiFi and sensor interference. We formulate the delay analysis problem as a two priority M/G/1 preemptive repeat identical queueing system, and analyze the delay using queueing theory and probability theory. First, we use a path probabilistic approach to derive the expected delay. Second, we develop a simplified linear approximation model for delay analysis. The correctness of both models is validated by NS2 simulations.Recently, many new types of wireless networks have emerged, such as mobile ad hoc networks (MANETs), cognitive radio networks (CRNs) and large scale wireless sensor networks. To get better performance in these wireless networks, various schemes, e.g., metrics, policies, algorithms, protocols, etc., have been proposed. Among them, optimal schemes that can achieve optimal performance are of great importance. On the theoretical side, they provide important design guidelines and performance benchmarks. On the practical side, they guarantee best communication performance with limited network resources. In this dissertation, we focus on the modeling and optimization of routing in wireless networks, including both broadcast routing, unicast routing, and convergecast routing. We study two aspects of routing: algorithm analysis and Qos analysis. In the algorithmic work, we focus on how to build optimal broadcast trees. We investigate the optimality compatibility between three tree-based broadcast routing algorithms and routing metrics. The Qos work includes three parts. First, we focus on how to optimally repair broken paths to minimize impact of path break in MANETs. We propose a provably optimal cached-based route repair policy for real-time traffic in MANETs. Second, we focus on the impact of secondary user (SU) node placement on SU traffic delay in CRNs. We design SU node placement schemes that can minimize the multi-hop delay in CRNs. Third, we analyze the convergecast delay of a large scale sensor network which coexists with WiFi nodes. We derive a closed form delay formula, which can be used to estimate sensor packet convergecast delay given the distance between a sensor node and the sink node together with other networking setting parameters. The main contributions of this dissertation are summarized as follows: Optimality compatibility study between tree-based broadcast routing algorithms and routing metrics: Broadcast routing is a critical component in the routing design. While there are plenty of routing metrics and broadcast routing schemes in current literature, arbitrary combination of broadcast routing metrics with broadcast tree construction (BTC) algorithms may not result in optimal broadcast trees. In this work, we study the requirement on the combination of routing metrics and BTC algorithms to ensure optimal broadcast tree construction. When a BTC algorithm fails to find the optimal broadcast tree, we define that the BTC algorithm and the metric are not optimality compatible. We show that different BTC algorithms have different requirements on the properties of broadcast routing metrics. The metric properties for BTC algorithms in both undirected network topologies and directed network topologies are developed and proved. They are successfully used to verify the optimality compatibility between broadcast routing metrics and BTC algorithms. Optimal cache-based route repair policy for real-time traffic in mobile ad hoc networks: Real-time applications in ad hoc networks require fast route repair mechanisms to minimize the interruptions to their communications. Cache-based route repair schemes are popular choices since they can quickly resume communications using cached backup paths after a route break. In this work, through thorough theoretical modeling of the cache-based route repair process, we derive a provably optimal cache-based route repair policy. This optimal policy considers both the overhead of the route repair schemes and the promptness of the repair action. The correctness and advantages of our optimal policy are validated by extensive simulations. Optimal secondary user node placement study in cognitive radio networks: Information propagation speed (IPS) in a multi-hop CRN is an important factor that affects the network's delay performance and needs to be considered in network planning. The impact of primary user (PU) activities on IPS makes the problem of analyzing IPS in multi-hop CRNs very challenging and hence unsolved in existing literature. In this work, we fill this technical void. We establish models of IPS in multi-hop CRNs and compute how to maximize IPS in two cases. The first case, named the maximum network IPS, maximizes IPS across a network topology over an infinite plane. The second case, named the maximum flow IPS, maximizes the IPS between a given pair of source and destination nodes separated by a fixed distance. We reveal that both maximum IPSs are determined by the PU activity level and the placement of SU relay nodes. We design optimal relay placement strategies in CRNs to maximize these two IPS under different PU activity levels. The correctness of our analytical results is validated by simulations and numerical experiments. Convergecast delay analysis of large scale sensor networks coexisting with WiFi networks: Due to the increasing popularity of wireless devices, such as WiFi (IEEE 802.11) and ZigBee (IEEE 802.15.4), the ISM bands have become more and more crowded. Since ZigBee is the de facto radio technology of sensor networks, coexistence of WiFi networks and sensor (ZigBee) networks is challenging because of the great heterogeneity between WiFi and ZigBee technologies. In the presence of interference from WiFi and other sensor nodes, the performance of sensor networks is not clearly understood. In this work, we study delay performance of a large scale sensor network which coexists with WiFi networks. Given the distance from the sensor node to the sink node, we are interested in the expected delay of sensor packets to reach the sink node in the presence of both WiFi and sensor interference. We formulate the delay analysis problem as a two priority M/G/1 preemptive repeat identical queueing system, and analyze the delay using queueing theory and probability theory. First, we use a path probabilistic approach to derive the expected delay. Second, we develop a simplified linear approximation model for delay analysis. The correctness of both models is validated by NS2 simulations. / Ph. D.

An airport node-link network model is an important input for most airport simulation models. Developing, maintaining and updating detailed airport surface node-link models require significant work. A model to convert airport geographic and geometric information into a node-link network is thus needed. In this thesis, an efficient model to automate the procedure of converting airport geographic and geometric information into a node-link network is proposed. The geographic and geometric information are obtained from the Aeronautical Information Exchange Model (AIXM). The node-link network is generated by converting the geographic and geometric information contained into the AIXM files using coincident geometry management and polygon representation development. Finally, using the airport node-link network generation model, a standalone computer application, called Taxiway Toolkit, is developed to improve the Airfield Delay Simulation Model (ADSIM+). / Master of Science

In dogs with large primary tumors, regional lymph node involvement or evidence of distant metastasis can have worse prognoses and significantly decreased survival. Lymph node size alone has been shown to be insufficient as a predictor for the accurate clinical staging of some canine neoplasia, including oral malignant melanoma. However, regional lymph nodes of the oral cavity, such as the medial retropharyngeal lymph nodes, are difficult to access for routine sampling. Diffusion weighted magnetic resonance imaging (DWI) has demonstrated the ability to differentiate metastatic from inflammatory/benign lymph nodes in clinical studies with human cancer patients through the calculation of quantitative values of diffusion termed apparent diffusion coefficients (ADC). The objective of this exploratory study was to evaluate DWI and ADC as potential future methods for detecting malignant lymph nodes in dogs with naturally occurring disease. We hypothesized that DWI would identify significantly different ADC values between benign and metastatic lymph nodes in a group of canine patients with head or neck disease. Our results demonstrated that two of four observers identified a significant difference between the mean ADC values of the benign and metastatic lymph nodes. When data from all four observers were pooled, the difference between the mean ADC values of the benign and metastatic lymph nodes approached but did not reach significance (P-value: 0.0566). Therefore, our hypothesis was not supported. However, DWI does show promise in its ability to differentiate benign from metastatic lymph nodes, and further studies with increased patient numbers are warranted / Master of Science

Current processor designs use additional transistors to add functionality that improves performance. These features tend to exploit instruction level parallelism. However, a point of diminishing returns has been reached in this effort. Instead, these additional transistors could be used to take advantage of thread level parallelism (TLP). This type of parallelism focuses on hundreds of instructions, rather than single instructions, executing in parallel. Additionally, as transistor sizes shrink, the wires on a chip become thinner. Fabricating a thinner wire means increasing the resistance and thus, the latency of that wire. In fact, in the near future, a signal may not reach a portion of the chip in a single clock cycle. So, in future designs, it will be important to limit the length of the wires on a chip. The SCMP parallel computer is a new architecture that is made up of small processing elements, called nodes, which are connected in a 2-D mesh with nearest neighbor connections. Nodes communicate with one another, via message passing, through a network, which uses dimension order worm-hole routing. To support TLP, each node is capable of supporting multiple threads, which execute in a non-preemptive round robin manner. The wire lengths of this system are limited since a node is only connected to its nearest neighbors. This paper focuses on the System C hardware design of the node that gets replicated across the chip. The result is a node implementation that can be used to create a hardware model of the SCMP parallel computer. / Master of Science