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Title: Co-operative coded communication under network constraints
Creator: Misra, Kiran Mukesh
Date: 2010
Collection: Electronic Theses & Dissertations

Title: Flexible spectrum use in channel bonding wireless networks
Creator: Yang, Xi (Software engineer)
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Channel bonding, which assembles multiple narrow channels into one logical channel, can speed up data transmission and achieve better bandwidth utilization in wireless networks. Since introduced in 802.11n, channel bonding has been extended continually to support wider channels, making low-lag high-speed wireless communication possible. However, different radio technologies have different requirements on channel width. Devices that use different channel widths coexist in a contention domain...
Show moreChannel bonding, which assembles multiple narrow channels into one logical channel, can speed up data transmission and achieve better bandwidth utilization in wireless networks. Since introduced in 802.11n, channel bonding has been extended continually to support wider channels, making low-lag high-speed wireless communication possible. However, different radio technologies have different requirements on channel width. Devices that use different channel widths coexist in a contention domain may cause inefficiency and unfairness issues. For example, narrowband devices are easier to obtain medium access opportunities because they do not need to wait for the entire wide band to be idle. Therefore, although wideband devices can provide higher transmission speed, they are at an unfavorable position in contentions with narrowband devices.To this end, we propose a flexible spectrum use channel bonding (FSUB) protocol in which a node is allowed to start a transmission whenever there are some idle narrow channels and gradually increases the channel width during transmission. Because a node dynamically adjusts the channel width in a communication, we use a convolution method to achieve fast spectrum agreement between the transmitter and the receiver. To address contentions between devices in a wide band of spectrum, we introduce a compound preamble to make the collisions detectable in the frequency domain and use a parallel bitwise arbitration mechanism to quickly determine the winner. We implement and evaluate the proposed protocol through both the GNU Radio/USRP platform and ns-2 simulations. The results show that the proposed protocol well addresses the inefficiency and unfairness issues caused by heterogeneous radio coexistence. Channel bonding devices usingFSUB have more medium access opportunities and can aggregate wider channels than using other channel bonding protocols in presence of narrowband interference. The FSUB enables a device to always benefit from channel bonding without concerns about narrowband interference level.
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Title: Communication performance of multicomputers
Creator: Chittor, Suresh Suryanarayana
Date: 1991
Collection: Electronic Theses & Dissertations

Title: Cooperative resource sharing by integrating cellular and mobile Ad Hoc networks
Creator: Zhu, Danyu
Date: 2005
Collection: Electronic Theses & Dissertations

Title: Network reachability : quantification, verification, troubleshooting, and optimization
Creator: Khakpour, Amir Reza
Date: 2012
Collection: Electronic Theses & Dissertations
Description: Quantifying, verifying, troubleshooting, and optimizing the network reachability is essential for network management and network security monitoring as well as various aspects of network auditing, maintenance, and design. Although attempts to model network reachability have been made, feasible solutions for computing, maintaining and optimally designing network reachability have remained unknown. Network reachability control is very critical because, on one hand, reachability errors can cause...
Show moreQuantifying, verifying, troubleshooting, and optimizing the network reachability is essential for network management and network security monitoring as well as various aspects of network auditing, maintenance, and design. Although attempts to model network reachability have been made, feasible solutions for computing, maintaining and optimally designing network reachability have remained unknown. Network reachability control is very critical because, on one hand, reachability errors can cause network security breaches or service outages, leading to millions of dollars of revenue loss for an enterprise network. On the other hand, network operators suffer from lack of tools that thoroughly examine network access control configurations and audit them to avoid such errors. Besides, finding reachability errors is by no means easy. The access control rules, by which network reachability is restricted, are often very complex and manually troubleshooting them is extremely difficult. Hence, having a tool that finds the reachability errors and fix them automatically can be very useful. Furthermore, flawed network reachability design and deployment can degrade the network performance significantly. Thus, it is crucial to have a tool that designs the network configurations such that they have the least performance impact on the enterprise network.In this dissertation, we first present a network reachability model that considers connectionless and connection-oriented transport protocols, stateless and stateful routers/firewalls, static and dynamic NAT, PAT, IP tunneling, etc. We then propose a suite of algorithms for quantifying reachability based on network configurations (mainly access control lists (ACLs)) as well as solutions for querying network reachability. We further extend our algorithms and data structures for detecting reachability errors, pinpointing faulty access control lists, and fixing them automatically and efficiently. Finally, we propose algorithms to place rules on network devices optimally so that they satisfy the networks central access policies. To this end, we define correctness and performance criteria for rule placement and in turn propose cost-based algorithms with adjustable parameters (for the network operators) to place rules such that the correctness and performance criteria are satisfied.We implemented the algorithms in our network reachability tool called Quarnet and conducted experiments on a university network. Experimental results show that the offline computation of reachability matrices takes a few hours and the online processing of a reachability query takes 75 milliseconds on average. We also examine our reachability error detection and correction algorithms on a few real-life networks to examine their performance and ensure that Quarnet is efficient enough to be practically useful. The results indicate that we can find reachability errors in order of minutes and fix them in order of seconds depending on the size of network and number of ACLs. Finally, we added the rule placement suite of algorithms to Quarnet, which can design a network ACL in based on the network central policies in order of tens of minutes for an enterprise network. We compare it with Purdue ACL placement, the state-of-the-art access policy design technique, and explain its pros and cons.
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Title: Secure and private access control for systems of smart devices
Creator: Le, Tam Dan
Date: 2019
Collection: Electronic Theses & Dissertations
Description: With the emergence of Internet of Things (IoT) technologies and the invasion of smart devices in almost every aspect of our lives, access control that allows only authorized users to access IoT devices becomes an important problem. The limited capabilities of the devices and the distributed nature of IoT environments have presented unique challenges to the design of an effective access control mechanism. First, it should be lightweight enough for the IoT devices to handle due to their...
Show moreWith the emergence of Internet of Things (IoT) technologies and the invasion of smart devices in almost every aspect of our lives, access control that allows only authorized users to access IoT devices becomes an important problem. The limited capabilities of the devices and the distributed nature of IoT environments have presented unique challenges to the design of an effective access control mechanism. First, it should be lightweight enough for the IoT devices to handle due to their resource constraints. Second, the variety of devices and applications and the arbitrary manners of users require the support of fined-grain, flexible access control policies. Last but not least, traditional access control models that are often centralized may not be suitable for distributed IoT. Therefore, a decentralized approach should be considered.In this dissertation, we propose access control solutions that are not only secure and private but also scalable to meet IoT requirements. Our first design is an authorization protocol that supports flexible delegation for smart home applications. The protocol allows users to create and share various permissions within their authorities to other users. In addition, since simple computation operations are used, the protocol is lightweight and supports fast validation at resource-constrained devices. Next, the need to support larger environments and the open problem with the exchange of access keys without a central authority motivate us to seek a decentralized solution from blockchain technology, which is originated from the famous cryptocurrency Bitcoin. The advantages of blockchain, which lie in an immutable distributed ledger that is maintained by a peer-to-peer network of untrusted nodes, can bring decentralization to IoT applications. However, applying blockchain to IoT is not straightforward as it was not originally designed for IoT requirements. We address two main issues in blockchain-based access control for IoT systems. First, since blockchain is a public platform, user privacy is one of the top priorities. Second, resource-constrained IoT devices are often not powerful enough to interact directly with the blockchain but need to rely on certain trusted nodes to retrieve blockchain data.The first issue of user privacy leads to our design of CapChain, a blockchain-based privacy-preserving access control framework that enables the sharing of access capabilities to multiple devices in a secure and private manner. Then, applying similar techniques to CapChain but also extending the use of blockchain by smart contracts, we design a privacy-preserving service that allows users to create IoT automated tasks by defining one of multiple conditional statements that need to be satisfied before a task can be performed. We set up strict privilege at the triggering party, such that it may not trigger the task any time except only when the conditions are satisfied.To address the second issue of resource constrained devices, we propose a method for IoT devices to validate blockchain data without solely being dependent on a central server. In our approach, several witnesses on the network can be selected randomly by the devices to validate access control information. Our method is aided by Bloom filters, which are shown to be lightweight for resource-constrained devices.
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Title: A unified environment for distributed computing
Creator: Gendreau, Thomas Bernard
Date: 1987
Collection: Electronic Theses & Dissertations

Title: Autoconfiguration and security for wireless networks
Creator: Zhou, Hongbo
Date: 2005
Collection: Electronic Theses & Dissertations

Title: The effects of participation and feedback received on the length of time members in online communities remain active
Creator: Sarkar, Chandan
Date: 2013
Collection: Electronic Theses & Dissertations
Description: Online communities support extensive interactions among their members. Membership in most of these communities is voluntary, content supplied by other members is typically a primary attractant to new members, and barriers to admission and exit are minimal (Lampe, 2009; Lampe, 2010). For a community to thrive, it is necessary that members remain active in the community and continue to interact with others. Given that sustaining a solid base of active long-term members is critical to the...
Show moreOnline communities support extensive interactions among their members. Membership in most of these communities is voluntary, content supplied by other members is typically a primary attractant to new members, and barriers to admission and exit are minimal (Lampe, 2009; Lampe, 2010). For a community to thrive, it is necessary that members remain active in the community and continue to interact with others. Given that sustaining a solid base of active long-term members is critical to the sustainability of an online community, it is important that factors that contribute to the length of active membership are identified. Addressing certain limitations of prior studies, this dissertation examines key factors such as rate of participation, rate of feedback received, early participation and early feedback received that may influence the length of time members stay active in a community. A mixed method approach that included server log analyses for two online communities, Everything2 and Sploder, and qualitative interviews with members of Everything2, was used to study how these factors are related to how long members remain active in a community. A Cox proportional hazard rate model and a Granger causality test were employed to analyze the server log data. The results suggest that certain types of early participation (first post submitted in Sploder and first post and first message submitted in Everything2) and certain type of early feedback received (deletion of post in Sploder and first positive and negative vote and deletion of first post in Everything2) are significant predictors of how long a member remains active in Sploder and Everything2. A member's average rate of participation (writeups, votes given, and messages sent) in Everything2 is positively correlated with length of active membership, but not in Sploder. The rate of feedback received is not significantly correlated in either community. It is well-known that correlational evidence is not dispositive proof of a causal link. Therefore, the relationships between the dependent variable and the independent variables identified by the Cox Proportional Hazard Rate model are further examined using a Granger causality test, with which time series data can be employed for a more rigorous test of causality. The results showed no causality between rate of participation and the length of time a member remains active in a community. Findings from the quantitative studies are expanded on, based on interviews with long-term members in the community. These results show that the factors contributing to length of active membership may vary among online communities. While some results may generalize to other communities if the communities are similar enough, not all results do generalize. The findings also suggest that early negative feedback has a strong negative impact on how long a member will remain active in an online community, as both Everything2 and Sploder had a significant negative correlation with deletion of first post. The implications of these results for the design online communities are discussed.
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Title: Estimating available bandwidth for real-time supermedia applications
Creator: Chobanyan, Alexander
Date: 2007
Collection: Electronic Theses & Dissertations

Title: Integration of a statistical method in one way delay trend detection for available bandwidth estimation
Creator: Shafii, Mahnaz
Date: 2008
Collection: Electronic Theses & Dissertations

Title: Optimizing message to virtual link assignment in Avionics Full-Duplex Switched Ethernet networks
Creator: Klonowski, Joseph
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "Avionics Full-Duplex Switched Ethernet (AFDX) is an Ethernet-based data network that provides deterministic performance, high reliability, and lower costs and development time by utilizing commercial off-the-shelf networking components. As AFDX networks have become of the network are continually being evaluated. There are two main types of solutions to improving network performance: changes to the physical layer and changes to the logical layer. Because the physical network is setup prior to...
Show more"Avionics Full-Duplex Switched Ethernet (AFDX) is an Ethernet-based data network that provides deterministic performance, high reliability, and lower costs and development time by utilizing commercial off-the-shelf networking components. As AFDX networks have become of the network are continually being evaluated. There are two main types of solutions to improving network performance: changes to the physical layer and changes to the logical layer. Because the physical network is setup prior to defining the data that is transferred on the network, logical layer optimization becomes important and is often the only viable solution. Previous research has explored optimization of different aspects of the logical solution for a given target (whether it be latency or bandwidth), however, an approach for a customizable target using optimization techniques has not been attempted. In this work, we provide an overview of AFDX networks and discuss factors engineers consider while optimizing the network. Previously researched solutions are evaluated for effectiveness. We identify the need for an optimization solution that allows for a customizable objective to account for both message latency and bandwidth. To fill this gap, we consider the problem of assigning messages to virtual links, which are configurable, logical unidirectional links from publishing end systems to one or more subscribing end systems. We propose a flexible framework based on particle swarm optimization (PSO) that performs message to virtual link assignment in AFDX networks to optimize a user-defined objective. We discuss and provide results on PSO optimization for a range of hyperparameters. Finally, results for a sample swarm are presented to prove the feasibility and usefulness of the proposed approach."--Page ii.
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